A dual-cathode zinc-ethylene glycol/air battery for concurrent electricity generation and plastic waste upcycling

Domain: biology
Published: 2026-03-16
Editorial outcome: minor_revision

Abstract
Conventional rechargeable zinc-air batteries (ZABs) face two critical challenges: (1) slow
kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions; and (2) the
thermodynamic incompatibility of OER and ORR occurring concurrently on a single air cathode.
To address these limitations, we propose in this study a dual-cathode zinc-ethylene glycol/air
battery (D-ZEAB) that spatially decouples ORR and the ethylene glycol oxidation reaction (EGOR)
onto separate cathodes, enabling concurrent electricity generation and electroreforming of
polyethylene terephthalate (PET) plastic waste into high-value C chemicals. Furthermore, we
develop a bifunctional catalyst composed of defect- rich subnanometer-thick PdCuCo trimetallenes
to enhance both EGOR and ORR kinetics. Benefiting from the decoupled cathode configuration
and the bifunctional PdCuCo catalyst, the D-ZEAB demonstrates an energy conversion efficiency
of 91.7%, a long cycle life of 1696 h, and a Faradaic efficiency of >93% for GA production. This
work not only presents a promising strategy for advancing the zinc-air battery technology but also
offers a sustainable route for simultaneous energy storage and plastic waste upcycling.

Introduction
Energy shortage and environmental pollution remain persistent global challenges, driving
the development of sustainable energy storage systems such as metal-air batteries, metal-ion
batteries, metal-sulfur batteries, and fuel cells.1, 2, 3, 4 Among them, rechargeable zinc-air batteries
(ZABs) utilizing atmospheric oxygen as the cathode active substance are widely considered
promising energy storage and conversion devices due to their high theoretical energy density (1350
Wh kg-1), cost-effectiveness, and environmental benignity.5, 6 A typical ZAB consists of a zinc
anode, an aqueous electrolyte, and a bifunctional air cathode that facilitates oxygen reduction
(ORR) during discharge and oxygen evolution (OER) during charge.7, 8 However, the
commercialization of ZABs remains hindered by several limitations: (1) the absence of cost-
effective bifunctional electrocatalysts that can enhance the sluggish ORR and OER kinetics leads
to low per-cycle capacity, large charging/discharging voltage gaps (∆E), and reduced energy
conversion efficiency; (2) the single-cathode configuration requires both ORR and OER to occur
on the same electrode, which, due to their opposing thermodynamic requirements, accelerates
catalyst oxidation and deactivation, thus reducing the discharging capacity and cycle life of the
batteries; (3) the charging process produces low-value oxygen, which undermines the economic
viability of ZABs. Thus, strategies to improve the energy efficiency, economic efficiency, and
operational stability of ZABs are urgently needed.

Recently, a class of zinc-X/air hybrid batteries (ZXAHBs, X = KI, alcohol, or urea) has been
proposed, wherein the kinetically sluggish OER is replaced with thermodynamically favorable
oxidation reactions (XOR) involving readily oxidizable substances, such as KI, alcohol, and urea.9,
10, 11, 12 These hybrid batteries demonstrate a significant improvement in energy conversion
efficiency by lowering the required charging voltages. However, despite their enhanced charging
performance, challenges persist, including: the unresolved thermodynamic mismatch between
ORR and XOR on a single air cathode; the absence of highly active and selective bifunctional
catalysts for both ORR and XOR; the low economic value of products generated during the battery
charging process (e.g., N from urea oxidation, and CO from most alcohol oxidations);11, 13, 14 and
2 2
the potential battery safety hazards arising from the introduction of flammable organic compounds
(e.g., methanol, ethanol) into the electrolyte. As a result, most reported ZXAHBs demonstrate only
modest performance, with areal discharging capacities ≤ 2 mAh cm-2 per cycle and cycle lifetimes
≤ 400 h.15, 16 To meet the demands of large-scale commercialization, zinc-air and hybrid batteries
must overcome these kinetic and thermodynamic limitations, achieving high areal capacity, energy
conversion efficiency, product selectivity, and long -term stability.

In this work, we introduce a dual-cathode zinc-ethylene glycol/air battery (D-ZEAB) that
spatially decouples the ORR and ethylene glycol oxidation reaction (EGOR) onto separate
cathodes. This design enables simultaneous electricity generation and electroreforming of PET
plastic waste into high-value C chemicals. By isolating the two reactions, the D-ZEAB optimizes
2
the thermodynamic conditions for EGOR (charging) and ORR (discharging), while preventing the
oxidation of ORR catalyst. Thereby, the discharging capacity and cycle life are both enhanced.
Moreover, replacing OER with the thermodynamically favorable EGOR significantly reduces
charging voltages and improves energy conversion efficiency. From a kinetic perspective, efficient
catalysts with low overpotentials for ethylene glycol-to-glycolic acid oxidation and the ORR are
required to enable high-performance operation of D-ZEAB. While Pd exhibits high activity for
both EGOR and ORR, its practical application is hindered by challenges in atomic utilization, mass
activity, and stability.17, 18 Integrating alloying and structure engineering to design Pd-based
trimetallene aims to retain high atomic utilization via quantum size effect and synergistically
optimize EGOR/ORR performance through ternary component interactions and tailored
architectures. Therefore, defect-rich PdCuCo trimetallene was further engineered as dual-cathode
catalyst to accelerate EGOR/ORR kinetics. Leveraging synergistic structural (e.g., lattice defects,
compressive strain, and metallene architecture) and alloying effects, the optimized PdCuCo-0.9
achieves high electrocatalytic performance: an EGOR mass activity of 16.6 A mg -1, an ORR half-
Pd
wave potential of 0.90 V (vs. RHE), and notable durability. In situ experiments and density
functional theory (DFT) calculations reveal that the synergistic structural and alloying effects
modulate the electronic structure of Pd sites on PdCuCo. This modulation weakens the adsorption
of the carbonyl (*CO) intermediate intermediate and accelerates the in situ formation of Pd-O(H)
ad
species, thereby facilitating the selective oxidation from ethylene glycol to glycolic acid (GA).
As a result of the decoupled cathode configuration and the notable bifunctional catalytic activity,
the
PdCuCo-based D-ZEAB achieves an energy density of 868 Wh kg-1, a discharging capacity of 10
mAh per cycle, and a long cycle life of 1696 h, with a Faradaic efficiency exceeding 93% for GA
production. Notably, the battery retains a high energy conversion efficiency of 91.7% even after
1696 h of continuous cycling.

Results
Design and working principle of rechargeable D-ZEAB
Fig. 1a schematically illustrates the configuration and working mechanism of the
rechargeable D-ZEAB. The battery features four key components: (1) a porous zinc anode; (2) a
charging cathode utilizing PET hydrolysate solution as electrolyte; (3) a discharging cathode with
6.0 M KOH+0.2 M Zn(OAc) mixed electrolyte; and (4) a membrane separating the two
2
electrolytes. This spatially decoupled cathode configuration enables the ORR and EGOR to
proceed independently under their respective optimal thermodynamic conditions without
interfering with each other. During operation, the system automatically switches between two
modes: charging (EGOR at one cathode to produce high-value GA) and discharging (ORR at the
other cathode). The detailed reaction pathways and the thermodynamic calculations provided in
Supplementary Eqs. S1-S9. Unlike conventional ZABs that are limited by the sluggish OER, the
charging process of D-ZEAB is significantly optimized by the low oxidation potential (~0.2 V vs.
SHE) and fast kinetics of EGOR.19 Theoretical calculations indicate that the D-ZEAB achieves an
low charging voltage of ~0.623 V (Supplementary Eqs. S9), representing a reduction of at least
1.030 V compared to typical ZABs (Fig. 1b). Additionally, the decoupled cathode design prevents
the oxidation-induced deactivation of ORR catalyst even at high charging voltages, dramatically
enhancing the cycle stability. Notably, the system also offers compelling sustainability advantages:
ethylene glycol (key EGOR reactant) can be abundantly sourced from PET waste hydrolysis,
creating a circular economy.20, 21 Beyond electricity generation during the discharging process, the
D-ZEAB simultaneously produces valuable GA through electroreforming of PET plastic waste.
As shown in Fig. 1c, this integrated approach presents a more cost-effective, energy-efficient, and
environmentally benign alternative to conventional GA production methods, offering significant
potential for addressing global plastic pollution while advancing energy storage technology.

Synthesis and characterization of PdCuCo trimetallenes
To achieve high-efficiency operation of the D-ZEAB, we developed defect-rich PdCuCo
trimetallenes as advanced bifunctional catalysts for simultaneous EGOR and ORR enhancement
(Fig. 2a). The catalysts were synthesized via a one-pot solvothermal method using Pd2+, Cu2+ and
Co2+ precursors with ethylenediamine (EDA) as the reducing agent. The X-ray diffraction (XRD)
analysis of PdCuCo trimetallenes confirms the formation of well-alloyed face-centered cubic (fcc)
phases (Fig. 2b and Supplementary Fig. S1). The diffraction peaks of PdCuCo trimetallenes are
positively shifted compared to pure Pd, indicating the existence of lattice compression due to the
incorporation of Cu/Co with a smaller atomic radius into the Pd lattice. Meanwhile, the broadened
diffraction peaks of PdCuCo trimetallenes suggest reduced crystallite size and the generation of
lattice defects caused by Cu/Co incorporation.22 Energy-dispersive X-ray spectroscopy (EDS) and
inductively coupled plasma-optical emission spectroscopy (ICP-OES) results verify the
coexistence of Pd, Cu, and Co elements, with a bulk composition of Pd/Cu/Co = 55.0/44.1/0.9 for
PdCuCo-0.9 (Fig. 2c and Supplementary Table S1). High-resolution transmission electron
microscopy (HR-TEM) observations reveal a 2D sheet-like morphology of PdCuCo-0.9 with an
average lateral size of ~20 nm (Fig. 2d and 2e); and atomic force microscopy (AFM) analyses
further verify a metallene structure of PdCuCo -0.9 (~1.0 nm thickness, ~5 atomic layers;
Supplementary Fig. S2). The sub-nanometer metallene architecture is conducive to shortening
diffusion pathways for reactant/intermediate and enhancing mass/charge transfer efficiency during
the electrocatalysis process. The combined structural and compositional features synergistically
contribute to the catalyst's high performance in the D-ZEAB system.23

Atomic-scale lattice configuration of PdCuCo-0.9 trimetallene was investigated using
aberration-corrected high-angle annular dark-field scanning TEM (HAADF-STEM). As denoted
by the blue dashed circles in Fig. 2f and Supplementary Fig. S3, numerous lattice distortions (LDs)
can be observed in PdCuCo-0.9, arising from the atomic size mismatch between Pd, Cu, and Co
constituents. Distinct zigzag atomic steps appear along the curved edges (indicated by red arrows,
Fig. 2g), while the enlarged HAADF-STEM observations further confirm the presence of twin
boundaries (TBs), atomic vacancies (AVs), and stacking faults (SFs) (Fig. 2h-2j). These structural
defects are expected to modulate the surface electronic states and enhance the electrocatalytic
activity.24 The integrated pixel intensities obtained by line-scan along the [111] direction reveal an
average lattice spacing of 2.22 Å for (111) planes (Fig. 2k). This represents an approximately 6.3%
compressive strain in PdCuCo-0.9 relative to the bulk Pd crystal (2.30 Å, JCPDS No. 87-0637),
attributed to atomic size difference and lattice defects.25 EDS mapping further validates
homogenous distribution of Pd, Cu, and Co elements throughout the nanostructure (Fig. 2l and
2m). To assess the impacts of Cu and Co incorporation, control samples including PdCuCo-0.3,
PdCuCo-1.7, PdCu alloy, and monometallic Pd were also synthesized using the same approach.
The representative TEM and EDS elemental mapping images of these control samples reveal
similar lattice defects across these variants (Supplementary Fig. S4-S6), which underscores the
versatility of our synthetic approach for preparing defect-rich Pd-based alloys.

X-ray photoelectron spectroscopy (XPS) was carried out to analyze the surface chemical
composition and electronic states of the catalysts. The XPS survey spectra of the PdCuCo samples
confirm the simultaneous presence of Pd, Cu, and Co elements (Supplementary Fig. S7a). In the
Pd 3d XPS spectra (Fig. 3a and Supplementary Fig. S7b), two main peaks at 339.7 eV and 334.4
eV are ascribed to metallic Pd0, alongside two lower-intensity peaks at 340.6 eV and 335.2 eV are
attributed to oxidized Pd2+ species.26 Notably, the Pd 3d binding energies in PdCuCo-0.9 and PdCu
exhibit negative shifts relative to pure Pd, indicating charge transfer from Cu/Co to Pd atoms,
mediated by their strong p-d orbital hybrid interaction.27 The Cu 2p XPS spectra (Fig. 3b and
Supplementary Fig. S7c) reveal two sharp peaks at 930.9 eV and 950.7 eV, confirming the
presence of metallic Cu0.28 Furthermore, the valence band spectra (VBS) in Fig. 3c demonstrate a
pronounced downshift in the d-band center for PdCuCo-0.9 (-2.85 eV) compared to PdCu (-2.70
eV) and Pd (-2.57 eV), signifying a modulated electronic state that weakens the adsorption of
carbonyl (CO*) intermediates on PdCuCo-0.9 trimetallene.29, 30 These XPS and VBS analyses
corroborate the metallic nature of constituent elements and highlight the modulated electronic
environment around Pd atoms in PdCuCo-0.9 trimetallene. Optimizing the electronic structure
near Pd can facilitate the binding of reaction intermediates at the Pd site, accelerating the
conversion of CO* intermediates and promoting the incomplete oxidation of EG to GA.29

The coordination environment and local electronic structure of each element in PdCuCo-0.9
trimetallene were further investigated using X-ray absorption spectroscopy (XAS). The
normalized X-ray absorption near-edge structure (XANES) spectra (Fig. 3d-3e and Supplementary
Fig. S8) at Pd, Cu, and Co K-edges exhibit absorption edges nearly identical to pure metal foils,
confirming the metallic states of all constituent elements and corroborating XPS results. Fourier
transform extended X-ray absorption fine structure (FT-EXAFS) analysis at Pd K-edge reveals a
dominant peak at 2.68 Å for PdCuCo-0.9 (Fig. 3f), corresponding to the Pd-Pd/Cu/Co coordination.
Notably, the Pd-Pd/Cu/Co peak exhibits a ~0.04 Å negative shift relative to the Pd foil and
monometallic Pd sample, which is considered to be due to lattice compression induced by smaller
Cu/Co atoms.31 Spectral fitting indicates a reduced coordination number for Pd-Pd/Cu/Co bond in
PdCuCo-0.9 (10.8±1.2 vs. 12 for Pd foil), confirming abundant structural defects and dangling
bonds at the trimetallene surface (Fig. S9, and Supplementary Table S2).32 Furthermore, the
shortened bond length of Pd-Pd/Cu/Co (2.61 Å vs. 2.74 Å for Pd foil) quantitatively demonstrates
compressive strain in PdCuCo-0.9, being consistent with the XRD and TEM observations
(Supplementary Table S2). Wavelet transform analysis further verifies the modified coordination
environment of PdCuCo-0.9 through a distinct pattern from PdO and narrower intensity
distributions in the K range than those of Pd foils.33 Complementary Cu and Co K-edge analyses
(Fig. 3g-3h and Supplementary Fig. S10-S12) yield consistent conclusions, collectively
demonstrating successful synthesis of strained PdCuCo-0.9 trimetallene with modulated local
electronic structure of Pd active sites.

Electrocatalytic EGOR and ORR performances of PdCuCo trimetallenes
The EGOR performance of the as-prepared catalysts was primarily evaluated in 1.0 M
KOH+1.0 M EG solution. As displayed in the linear sweep voltammetry (LSV) curves
(Supplementary Fig. S13a), the recorded onset potential for EGOR is significantly lower than that
of the OER on the same electrode. In particular, only an EGOR potential of 0.92 V (vs. RHE) was
required for PdCuCo-0.9 trimetallene to deliver a current density of 100 mA cm-2 (Supplementary
Fig. S13b), which is about 1030 mV lower than that of OER. These results confirm the
thermodynamically favorable nature of EGOR over OER, highlighting its realistic feasibility for
substituting OER in D-ZEAB. Mass-normalized cyclic voltammetry (CV) curves display distinct
anodic peaks during the forward/reverse scanning of all catalysts (Fig. 4a and Supplementary Fig.
S14), which correspond to the ethylene glycol oxidation. Notably, the mass activity (MA) of
PdCuCo-0.9 trimetallene attained 11.9 A mg -1(Fig. 4b), which is 1.6, 3.1, and 4.0 times higher
Pd
than that of PdCu, Pd, and Pd black, respectively. The smallest Tafel slope of PdCuCo-0.9
trimetallene (127.8 mV dec-1) further reflected its rapid charge transfer kinetics during EGOR
(Supplementary Fig. S15). The electrocatalytically active surface areas (ECSA) were determined
to be 80.7, 63.0, 41.3, and 55.1 m2 g -1 for PdCuCo-0.9, PdCu, Pd, and Pd black, respectively by
Pd
the CV method (Supplementary Fig. S16 and S17). The larger ECSA value of PdCuCo-0.9 is
attributed to its thin 2D sheet-like morphology and defect-rich structure, which maximizes active
site density and Pd utilization. Moreover, specific activity (SA) calculations normalized to ECSA
further confirm the notable EGOR performance of PdCuCo-0.9 (9.7 mA cm-2), exceeding all
control catalysts (Fig. 4c and Supplementary Fig. S18). The stability of catalysts toward EGOR
was evaluated through CV tests. After 500 CV cycles, the EGOR mass activity of PdCuCo-0.9
was still up to 10.5 A mg -1, with a decay rate of only 12%, outperforming commercial Pd black
Pd
and underscoring its notable electrochemical stability (Fig. 4d and Supplementary Fig. S19). The
notable EGOR performance of PdCuCo-0.9 can be attributed to the highly exposed active Pd sites
enabled by its metallene structure, as well as the tuned electronic structure originating from the
lattice defects and alloying effect among the multiple elements.

Next, the EGOR performance of PdCuCo trimetallenes was further investigated using the
PET hydrolysate solution as electrolyte (Supplementary Fig. S20). Fig. 4e shows the CV curves
of the catalysts in alkaline PET hydrolysate solution, which exhibit EGOR profiles similar to those
observed in 1.0 M KOH+1.0 M EG electrolyte. Notably, PdCuCo-0.9 achieves a high peak mass
activity of 16.6 A mg -1, surpassing the mass activities of Pd black, Pd, PdCu, PdCuCo-0.3, and
Pd
PdCuCo-1.7, and is comparable to the advanced EGOR catalysts reported in references
(Supplementary Fig. S21 and Table S3). Furthermore, among all as-synthesized catalysts and
commercial Pd black, PdCuCo-0.9 demonstrated the high geometric activity (Supplementary Fig.
S22). After a 5 h chronoamperometric (in-t) test at 0.77 V (vs. RHE), PdCuCo-0.9 retained 42%
of its initial current density, exceeding the performance of control samples in this work, confirming
the notable stability (Fig. 4f). EGOR products were further quantified by 1H nuclear magnetic
resonance (NMR) spectroscopy (Supplementary Fig. S23 and S24). GA, identified by its distinct
peak at 3.8 ppm in the NMR spectrum, is the primary EGOR product of PdCuCo-0.9, with no
detectable formic acid (FA) byproduct, suggesting its high GA selectivity. Furthermore, PdCuCo-
0.9 achieves a GA Faradaic efficiency (FE ) exceeding 90% over a wide potential range from
GA
0.7 to 1.0 V (vs. RHE), reflecting its high selectivity for GA synthesis via the electroreforming of
PET wastes (Fig. 4g). Remarkably, the maximum FE and GA yield rate of PdCuCo-0.9 reach
GA
up to 94.8% and 0.32 mmol cm-2 h-1 at 0.85 V (vs. RHE), respectively, rivaling recently reported
advanced EGOR catalysts (Supplementary Table S4).

The ORR performance of PdCuCo trimetallenes was then assessed in O -saturated 0.1 M
2
KOH. As presented in Fig. 4h and Supplementary Fig. S25a, PdCuCo-0.9 exhibits a half-wave
potential (E ) of 0.90 V vs. RHE, surpassing the E values of PdCu, Pd, and commercial Pt/C
1/2 1/2
by 40, 60, and 50 mV, respectively, signifying notable ORR activity. Among all tested catalysts,
including Pt/C, PdCuCo-0.9 held the smallest Tafel slope (71.0 mV dec-1), reflecting the favorable
ORR kinetics (Supplementary Fig. S25b).34, 35 The average electron transfer number close to 4 and
low H O yield (< 6%) for PdCuCo-0.9 over 0.2 to 0.9 V (vs. RHE) confirm a dominant 4e- transfer
2 2
ORR pathway (Supplementary Fig. S25c). Durability testing via chronoamperometry displayed
93.6% current retention after 11 h, while 2000 CV cycles caused negligible E
1/2
loss, demonstrating
respectable ORR stability and performance reproducibility (Fig. 4i; Supplementary Fig. S25d).
The enhanced ORR activity of PdCuCo-0.9 trimetallene arises from its defect-rich structure, which
maximizes active Pd site density and utilization, while Cu/Co incorporation facilitates O
2
adsorption/dissociation into *O intermediates for efficient 4e- pathways.36

Reaction mechanism investigations and theoretical calculations.
The adsorption behavior of EG molecules on the catalyst surface was initially investigated
using the open-circuit potential (OCP) measurements (Supplementary Fig. S26). When switching
to PET electrolyte, the OCP of PdCuCo-0.9 decreased by 0.84 V, exceeding the OCP reductions
of PdCu (0.77 V) and Pd (0.65 V), reflecting its notable affinity for EG. CO stripping experiments
reveal that the oxidation potential of the CO* intermediate on PdCuCo-0.9 is 0.77 V
(Supplementary Fig. S27), which is 20 mV and 40 mV lower than those on PdCu and Pd,
respectively, indicating the weaker CO* adsorption on PdCuCo-0.9.29 This facilitates the rapid
desorption and subsequent conversion of carbonyl (CO*) intermediates during the EGOR process,
thereby maintaining a highly active catalyst surface and promoting high selectivity toward GA.37
In situ electrochemical impedance spectroscopy (EIS) analysis demonstrated that PdCuCo-0.9
exhibits a lower charge transfer resistance and phase angle compared to both PdCu and Pd black,
suggesting its faster reaction kinetics (Fig. 5a, 5b; Supplementary Fig. S28 and Table S5).38 This
enhanced kinetic behavior can be attributed to the synergistic effects of abundant lattice defects,
metallene architecture, and multi-element alloying, which collectively accelerate the EGOR
kinetics of PdCuCo-0.9.

To gain insight into the reaction mechanism of the EGOR on PdCuCo-0.9 trimetallene, in
situ electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy
(ATR-SEIRAS) and Raman spectroscopy measurements were performed to identify key reaction
intermediates. As displayed in the in situ ATR-SEIRAS spectra (Fig. 5c), the characteristic peaks
located at 1043 cm-1 and 1086 cm-1 are attributed to the stretching vibration of the GA species.39
The peaks at 1258 cm-1, 1362 cm-1 and 1336 cm-1 belong to the symmetric and antisymmetric
stretching vibrations of COO- in GA.40 The intensity of above characteristic peaks increases with
the increase of potential, indicating the continuous generation of GA during EG oxidation. Notably,
the GA-associated peak (1043 cm-1, 1086 cm-1 and 1258 cm-1) exhibits markedly higher intensity
on PdCuCo-0.9 compared to those of pure Pd and PdCu, confirming its notable selectivity for GA
production (Fig. 5d and Supplementary Fig. S29). Additionally, there is a distinct peak at 1646 cm-
1 corresponding to the CH OHCO* intermediate, which is a key intermediate in the EGOR process
2
of the C pathway.41 Meanwhile, the signal of FA was hardly observed at 1376 cm-1.42 Furthermore,
2
no clear hydroxyl radicals (•OH) signal was detected by electron paramagnetic resonance (EPR)
at 1.0 V (vs. RHE) for PdCuCo-0.9, demonstrating that •OH do not play a major role in mediating
the EGOR on this catalyst (Fig. 5e). Fig. 5f illustrates the potential-dependent in situ Raman
spectra of PdCuCo-0.9 recorded in 1.0 M KOH+1.0 M EG. As the applied potentials was increased
from 0.5 to 1.1 V (vs. RHE), distinct Raman peaks was emerged at 478 cm-1, 557 cm-1, and 652
cm-1. These signal are characteristic of the Pd-O stretching vibration associated with Pd-OH and
ad
Pd-O (denoted as Pd-O(H) ) species generated during glycolate formation.43 Notably, LSV
ad ad
measurement revealed no significant evidence of palladium oxide formation within the potential
range of 0.5 V-1.1 V (Supplementary Fig. S13), suggesting that the observed Pd-O(H) species
ad
formed in situ on PdCuCo-0.9 differ from typical PdO oxide. Under identical conditions, these
x
Pd-O(H) -related Raman signals exhibited significantly reduced intensity on the PdCu and were
ad
barely detectable on the pure Pd sample (Fig. 5g and Supplementary Fig. S30). Additional peaks
at 1355 cm-1, 1427 cm-1, and 1579 cm-1 are attributed to COO- symmetric and asymmetric
stretching vibration of GA.44 Collectively, the aforementioned in situ characterizations and EPR
analysis confirm that the in situ formed Pd-O(H) species on the PdCuCo catalyst surface strongly
ad
suppressed the cleavage of the C-C bond in intermediates, thereby contributing to a rapid reaction
pathway from EG to glycolate (Fig. 5h and Supplementary Fig. S31).

To explore the origins of the notable EGOR performance of PdCuCo-0.9, density functional
theory (DFT) calculations were conducted to investigate differences in electronic structures and
reaction energetics among various electrocatalysts. For all the catalyst surfaces, the most preferred
adsorption sites are near the Pd-top site, supporting that Pd is the main active site (Supplementary
Fig. S32-S34). The surface electronic distribution of PdCu and PdCuCo-0.9 was analyzed via
bonding and anti-bonding orbital distributions near the Fermi level (E) (Fig. 6a and 6b). By
f
introducing Co atoms, the orbital coupling at the Pd site in PdCuCo-0.9 is slightly weakened due
to electron modulation, indicating an enhanced electron richness of Pd. Meanwhile, the surface Co
sites exhibit significant orbital coupling, which is conducive to electron transfer/exchange and
thereby enhances the electroactivity of PdCuCo-0.9. Fig. 6c displays the bond length contraction
trends of different catalysts: Pd > PdCu > PdCuCo-0.9, indicating that the introduction of Cu/Co
induces a stronger lattice compression strain, which is consistent with the HAADF-STEM results.
Projected partial density of states (PDOS) comparisons between PdCu and PdCuCo-0.9 show Cu-
3d orbitals with sharp peaks at lower energies than E (Fig. 6d and 6e), positioning Cu as an
f
electron reservoir to modulate adjacent Pd sites. Conversely, the Pd-4d orbitals are located near
the E as the main active sites for EGOR. With the introduction of Co sites, the Pd-4d orbitals
f
slightly downshifted and became more concentrated, which weakened the adsorption strengths of
key intermediates and accelerated the subsequent conversion processes. Notably, the Co-3d
orbitals display a distinct E-adjacent peak, which contributes to the surface electron transfer
f
during EGOR. The d-band center shifts further confirm these trends, with both overall structures
and Pd sites exhibiting downward shifts (Fig. 6f). Mulliken charge analysis reveals reduced Pd
surface charge due to electron donation from positively charged Co sites, while electron-rich Cu
sites exhibit the most negative charges (Fig. 6g), optimizing the surface electroactivity. These
results support the XPS and VBS characterizations that more electrons are transferred from Cu/Co
to the Pd sites, which alleviates the adsorptions of key intermediates to improve the selectivity of
GA production.

The site-dependent PDOS of Pd sites in PdCuCo-0.9 reveals electronic structure changes
near the E (Fig. 6h). Compared to the pristine Pd surface, Pd-4d orbitals in PdCuCo-0.9 localize
f
toward the surface, promoting electron transfer. Meanwhile, the electron density near the E is
f
gradually decreases, which leads to weakened intermediate binding strengths during EGOR. In
contrast, Cu-3d orbitals display increased spatial confinement while maintaining similar d-band
center positions (Fig. 6i), revealing Cu's role as an electron reservoir to modulate Pd electronic
states. Adsorption energy analyses demonstrate distinct trends: PdCuCo-0.9 exhibits the strongest
EG* affinity, whereas CH OHCO* binding energies increase progressively from PdCuCo-0.9 to
2
Pd (Fig. 6j). This trend indicates that the notable performance of PdCuCo-0.9 in converting EG to
GA stems from the activation of reactants and the rapid conversion of intermediates. The analysis
of reaction free energy further revealed that the rate-determining steps (RDS) of Pd and PdCuCo-
0.9/PdCu were the formation processes of CH OHCH O* and CH OHCO*, respectively.
2 2 2
Compared with Pd (0.81 eV) and PdCu (0.44 eV), the RDS barrier of PdCuCo-0.9 was
significantly reduced to 0.25 eV, thereby achieving efficient EGOR performance (Fig. 6k).

Performance of rechargeable D-ZEAB based on PdCuCo-0.9 trimetallene
As a proof-of-concept study, a rechargeable D-ZEAB was assembled using PdCuCo-0.9
trimetallene as a bifunctional catalyst, with EGOR and ORR decoupled on two independent
cathodes (Supplementary Fig. S35). A mixed solution of 1.0 M KOH+1.0 M EG was served as the
charging electrolyte. For comparison, single-cathode zinc-ethylene glycol-air battery (S-ZEAB)
and dual-cathode zinc-air battery (D-ZAB) were also assembled using PdCuCo-0.9 catalysts
(Supplementary Fig. S36). As shown in Fig. 7a, the discharging voltage of D-ZEAB was at least
190 mV higher than that of S-ZEAB across 5~50 mA cm-2, demonstrating the decoupled cathodes
eliminate the adverse effect of concomitant EG in electrolyte during ORR and maintain optimal
reaction thermodynamics. At 5 mAh cm-2, D-ZEAB exhibits a significantly lower charging voltage
(1.31 V vs. 2.07 V for D-ZAB), highlighting ~32% higher charging efficiency via EGOR
substitution for OER (Supplementary Fig. S37a-S37d). Notably, EGOR replacement greatly
enhances the charging/discharging energy conversion efficiency (ECE) from 55.1% (D-ZAB) to
87.0% (D-ZEAB), confirming notable energy savings. Unlike D-ZAB, D-ZEAB prioritizes liquid
C chemicals during charging (Supplementary Fig. S37e), eliminating the formation of O and the
2 2
catalyst loss resulting from the bubble impulse, thereby extending the service life of battery. After
48 h continuous cycling, the FE remains >94.0% (Supplementary Fig. S37f and S37g),
GA
validating high and stable GA production efficiency in the PdCuCo-0.9-based D-ZEAB system.
To expand its practical applications, the performance of D-ZEAB using PET hydrolysate
solution as the charging electrolyte was investigated. Both the PdCuCo-0.9-based D-ZEAB and
ZAB delivered an energy density of approximately 868 Wh kg-1, which is 13.8% higher than that
of the Pt/C + Pd black reference system (763 Wh kg-1) and comparable to the recently reported
advanced ZABs, highlighting the notable energy storage performance of this catalyst (Fig. 7b and
Supplementary Table S6). Fig. 7c and Supplementary Fig. S38 show the galvanostatic
charging/discharging cycling curves of batteries at the areal discharging capacity of 5 mAh cm-2
per cycle. The PdCuCo-0.9-based D-ZEAB exhibits a narrow charging/discharging voltage gap
(∆E) of 50 mV and a high ECE of 95.7%, outperforming Pt/C+Pd black-based D-ZEAB
(Supplementary Fig. S39). Compared with the reported conventional ZABs, the PdCuCo-0.9-
based D-ZEAB is also competitive (Supplementary Table S7). In particular, only a slight decrease
of ∆E and ECE values were observed for PdCuCo-0.9 based D-ZEAB after continuous
discharging/charging for 848 cycles (a total of 1696 h), demonstrating an notable cycling stability.
Even at 10 mAh cm-2, the PdCuCo-0.9-based D-ZEAB still demonstrates an ECE of no less than
66.0% and maintains stable cycling for 615 h (Supplementary Fig. S40). Besides, the thin 2D
sheet-like morphology and defect-rich structure of PdCuCo-0.9 trimetallene after long-term
cycling tests are well preserved, verifying the structural stability (Supplementary Fig. S41 and
S42). Notably, unlike the partial oxidation of the catalyst on charging the cathode, the metallic
character and single-phase fcc structure of PdCuCo-0.9 on discharging the cathode are maintained
after long-term cycling tests (Supplementary Fig. S43 and S44). This significant difference
highlights the advantages of the spatially decoupled cathode structure of D-ZEAB in terms of
avoiding oxidation and deactivation of the ORR catalyst.

Finally, the EGOR products in the charging electrolyte of the PdCuCo-0.9 based D-ZEAB
were identified by 1H NMR spectroscopy under different cycling periods. As shown in
Supplementary Fig. S45 and S46, GA was identified as the main product during the charging
process, with trace amounts of FA by-products. The FE
GA
on the charging cathode remained above
93.0% at the areal discharging capacities of 5 and 10 mAh cm-2 per cycle, confirming the high
selectivity of GA production via PET electroreforming during the charging process of PdCuCo-
0.9 based D-ZEAB (Fig. 7d). To achieve effective resource recovery and recycling, we further
separated and purified the high-value products from the charging electrolyte after cycling tests.
Ultimately, 40.36 g TPA and 8.51 g GA were obtained from the electroreforming of 50 g PET
plastic waste (Fig. 7e and Supplementary Fig. S47), achieving a total mass yield of 97.7% for
products. The preliminary techno-economic analysis demonstrated that although the initial input
cost for the D-ZEAB exceeds that of a conventional ZAB by $466.7 per ton of processed PET, it
generates a substantially higher total output value ($2,346.3 versus $82.5). This yields a net profit
of $276.5 per ton of processed PET, confirming the D-ZEAB's economic viability (Supplementary
Tables S8-S11 and Fig. S48-S49). Notably, compared to existing aqueous zinc-based batteries
(Supplementary Table S12), the D-ZEAB proposed in this work exhibits comprehensive
superiority over critical performance metrics, including cycle life, energy conversion efficiency,
discharging capacity, and functionality, demonstrating promising application prospects.

Methods
Chemicals
Palladium (II) acetylacetonate (Pd(acac) , 99%), copper acetylacetonate (Cu(acac) , 97%), cobalt
2 2
(II) acetylacetonate (Co(acac) , 97%), ethylenediamine (EDA, 98%), polyvinylpyrrolidone (PVP,
2
MW 220000, K60), N, N-dimethylformamide (DMF, 99.5%), potassium hydroxide (KOH, 95%),
deuterium oxide (D O, 99.9%), Maleic acid (98%), zinc acetate (Zn(OAc) , 98%) and ethylene
2 2
glycol (EG, 98%) were purchased from Shanghai Macklin Biochemical Co., Ltd. Acetone was
purchased from China National Pharmaceutical Group Corporation. All the chemicals were used
without further purification. The Nafion solution (5 wt.%) was purchased from DuPont de
Nemours, Inc. Pd black (99.95 wt.%) and Pt/C (20 wt.%) were purchased from Suzhou Sinero
Technology Co., LTD.

Synthesis of PdCuCo trimetallenes
To synthesize PdCuCo trimetallenes, 30 mg Pd(acac) , 20 mg Cu(acac) , 3 mg Co(acac) , and 80
2 2 2
mg PVP were dissolved in a mixed solution containing 0.5 mL EDA and 10 mL DMF. The mixture
was then stirred for 15 min to form a homogeneous solution. Subsequently, the solution was sealed
in a Teflon reactor and heated under controlled conditions, with the temperature ramped from room
temperature (25 °C) to 145 °C over 35 min and maintained for 24 h. After reaction completion,
the products were collected via centrifugation and rinsed six times with a deionized water-acetone
mixture (1:1 v/v). The centrifuged precipitate was freeze-dried for 24 h to obtain PdCuCo-0.9
trimetallene. Systematic synthesis of PdCuCo trimetallenes with varying Co atomic percentages
(PdCuCo-0.3 and PdCuCo-1.7) were achieved by adjusting the Co(acac)₂ precursor quantity,
where the numerical subscript denotes the Co atomic percentage. The synthesis procedure of PdCu
and Pd catalyst was similar to that of PdCuCo trimetallenes except for the absence of Co(acac)
2
and in Cu(acac) the precursor solution.
2

Material Characterizations
The morphology and microstructure of the catalysts were analyzed by TEM (JEOL JEM 2100 F)
and and aberration-corrected HAADF-STEM (FEI Titan Themis Cubed G2 300). XRD patterns
were obtained by using Rigaku SmartLab SE powder diffractometer with Cu Kα radiation. ICP-
OES was applied to determine the content of metals. The thickness and roughness of samples were
measured by AFM (Bruker Dimension Icon). 1H and 13C NMR spectroscopy was measured on a
400 MHz/AVANCE NEO (Bruker). EPR measurement was performed on Bruker A300 EPR
spectrometer. In situ Raman spectra were collected on Horiba Scientific LabRAM HR Raman
spectrometer. XAS data were collected at the 1W1B station at the Beijing Synchrotron Radiation
Facility (BSRF). XPS and surface valence band photoemission spectra were recorded on Thermo
Scientific K-Alpha.The d-band centers were calculated by following equation:29
0 eV (Ef ) 0 eV (Ef )
∫ (binding energy (E) × intensity(E)dE)/∫ intensity(E)dE (1)
-10 eV -10 eV

Electrochemical measurements
All electrochemical measurements were performed on a Corrtest (CS 2350M, Wuhan CorrTest
Instruments Co. China) electrochemical workstation equipped with a rotating ring-disk electrode
(RRDE) device (d = 5 mm, RRDE-3A, BAS Inc). In the constructed standard three-electrode test
system, a Hg/HgO electrode and a graphite rod were used as reference electrode and counter
electrode, respectively. The reference electrode is calibrated by measuring the electrode potential
in a standard solution with a known concentration. The catalyst ink was prepared by dispersing 4
mg catalyst powders into a mixed solution containing 50 μL Nafion (5 wt.%), 750 μL isopropyl
alcohol, and 200 μL deionized water, followed by ultrasonicating for 0.5 h. Then, 4 μL catalyst ink
was dropped on the rotating disk electrode (RDE, d = 5 mm) and dried using an infrared lamp. All
potentials were recorded against the reversible hydrogen electrode (RHE) by the following
equation: E = E + 0.098 V+ 0.0592×pH, where E is the calibrated potential vs. RHE,
RHE Hg/HgO RHE
E is the measured potential, and the pH value depends on the electrolyte. 1.0 M KOH+1.0
Hg/HgO
M EG solution (volume: 50 mL, pH=13.8±0.05), and PET hydrolysate solution (volume: 50 mL,
pH=14.2±0.05) were used as electrolyte for EGOR performance measurements, respectively. O -
2
saturated 0.1 M KOH solution (volume: 50 mL, pH=12.8±0.05) was used as electrolyte for ORR
performance measurements. The electrolyte solution was freshly prepared and utilized without
storage to ensure optimal performance. The performance was collected from a representative
measurement. The electrochemical performance of the catalyst was evaluated after 20 activation
cycles, and the data from the second cycle were collected for analysis. The EGOR stability of
catalysts was assessed using the chronoamperometry (i-t) method at a constant potential of 0.77 V
(vs. RHE). Electrochemical impedance spectroscopy (EIS) was carried out over a frequency range
from 100 kHz to 0.01 Hz at various potentials, with an AC voltage amplitude of 5 mV. The CV
was tested with different scan rates (100, 120, 140, 160, 180 and 200 mV s-1) from 0.38 to 0.48 V
(vs.RHE) to calculate the effective ECSA of the catalyst. A linear plot was obtained by plotting the
value of ΔJ(|J -J |/2) of the current density against the CV scan rate. The slope of the fitted
max min
line is C , which is proportional to the ECSA. All potentials were recorded without IR
dl
compensation. The ORR stability was test by i-t method at 0.79 V (vs. RHE). Hydrogen peroxide
yields and the electron transfer number (n) were calculated by the following equations (Equation
2 and 3):
2𝐼𝑟
%( HO- ) = 100× 𝑁 (2)
2 𝐼𝑑+ 𝐼
𝑁
𝑟
n = 4 ×
Id
(3)
Id+I
N
𝑟
where I is the disk current, I is the ring current, and N (0.43) is the current collection efficiency
d r
of the Pt ring.45

In situ electrochemical ATR-SEIRAS measurements
In situ ATR-SEIRAS measurements were performed using a Nicolet iS50 FTIR spectrometer
equipped with a liquid nitrogen-cooled mercury-cadmium-telluride (MCT) detector at an
incidence angle of ca. 60°. The catalyst ink was prepared by dispersing the as-synthesized PdCuCo
catalyst powder in a mixture of isopropyl alcohol and Nafion solution followed by ultrasonication
for 30 minutes. 10 µL catalyst ink was drop-cast onto the Au-coated silicon prism and dried gently
under an infrared lamp to form a uniform catalyst layer. The in situ ATR-SEIRAS spectra were
collected from 0.1 to 1.1 V (vs. RHE) in N -saturated 1.0 M KOH containing 1.0 M EG, with an
2
interval of 0.1 V.

Assembly of rechargeable dual-cathode zinc-ethylene glycol/air battery (D-ZEAB)
As a proof-of-concept, a rechargeable D-ZEAB was assembled using home-made
electrochemical cell with PdCuCo-0.9 trimetallene as the bifunctional catalyst. The battery
architecture comprises: (1) a porous zinc plate (99.99% purity, 34 mm×85 mm×0.5 mm) as anode;
(2) a charging cathode with 1.0 M KOH+1.0 M EG or PET hydrolysate solution as the electrolyte;
(3) a discharging cathode containing 6.0 M KOH+0.2 M Zn(OAc) electrolyte; and (4) a Nafion
2
117 membrane (Dupont, d=3 cm, thickness: 178 µm) separating the charging/discharging
electrolytes. Prior to use, the Nafion 117 membrane was washed with deionized water to remove
surface impurities. The charging/discharging cathodes were prepared by drop-casting PdCuCo-0.9
catalyst ink (loading: 1.6 mg cm-2) onto gas diffusion layer (carbon paper, YLS-30T, Toray),
resulting in a total reaction area of 1.0 cm2. An automatic relay switch (mechanical electrical device,
<70 ms response time) was implemented for cathode polarity reversal, though inherent latency
introduced minor cycling hysteresis. Galvanostatic charging/discharging cycling (2 h/cycle) was
performed using a NEWARE (CT-4008Tn, Shenzhen Neware Electronic Co. Ltd.) battery testing
system. The volume of the electrolyte storage tank is 300 mL. The electrolyte was continuously
supplied to the cathode chambers with a flow rate of 30 mL min-1 and refreshed every 48 h during
the long-term charging/discharging cycling. For comparison, the D-ZEAB using Pd black and Pt/C
as EGOR and ORR catalysts were also assembled. The single-cathode zinc-ethylene glycol-air
battery (S-ZEAB) was fabricated using porous zinc plate as anode, gas diffusion layer supported
PdCuCo-0.9 catalysts as cathode, and 6.0 M KOH+0.2 M Zn(OAc) +1.0 M EG as electrolyte. The
2
dual-cathode zinc-air battery (D-ZAB) comprises a porous zinc anode, a charging cathode with
1.0 M KOH solution as electrolyte, a discharging cathode with 6.0 M KOH+0.2 M Zn(OAc)
2
solution as electrolyte. The zinc-air battery (ZAB) comprises a porous zinc anode, a cathode with
6.0 M KOH+0.2 M Zn(OAc) solution as electrolyte. All battery tests were performed in a
2
temperature-controlled chamber maintained at 25 ° C (±1.0 °C) and 60 ± 2% relative humidity.

EGOR products analysis
The EGOR products were collected by chronoamperometry tests at the potential range from 0.7 to
1.0 V (vs. RHE) with an interval of 50 mV. After 2 h of electrolysis, the products were quantified
using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. 500 μL electrolyte was
collected and diluted with 100 μL D O for NMR analysis. Maleic acid (2.5 mg mL-1) was
2
employed as an internal standard. The glycolic acid (GA) yield rate (mmol h-1 cm-2) was calculated
using the following equation:
Yield rate (GA) = (C × V)/(t × S) (4)
GA
The Faradaic efficiency of GA production (FE ) is defined as the percentage of the charge
GA
consumed for GA generation in the total charge passed through the electrode, which can be
calculated by following equation:
FE = (4 × F × C × V × 10-6)/Q × 100% (5)
GA GA
where C is the measured GA concentration (mmol L-1); V is the volume (mL) of collected
GA
electrolyte; t is the electrolysis time (h); F is the faraday constant (96485 C mol-1); S is the reaction
area (cm2); Q is the total charge (C) passed through the electrode.46

Theoretical calculations
To investigate the performances of EGOR, DFT calculations have been performed through the
embedded CASTEP packages to understand the electronic modulations and reaction energetics in
PdCuCo catalysts.47 The generalized gradient approximation (GGAS) and Perdew-Burke-Ernzerhof
(PBE) functionals were employed to describe the exchange-correlation interactions.48 The PdCuCo
alloys have been constructed based on the (111) surface of Pd in a 4×4×1 supercell with five atomic
layer thicknesses to match the experimental characterizations (Supplementary Data 1). A 20 Å
vacuum spacer was introduced along the z-axis to prevent periodic boundary effects and ensure
full relaxation. Structural optimization convergence criteria included: (1) total energy difference
<5×10-5 eV/atom, (2) maximum ionic displacement <0.005 Å, and (3) Hellmann-Feynman forces
<0.001 eV/Å.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors introduce the EGOR reaction to address the slow kinetics of the OER in conventional zinc–air batteries, and\nthey further aim to achieve upcycling by employing PET plastic hydrolysate. As a result, they propose an environmentally\nfriendly battery system with high charging efficiency that utilizes waste plastics. To further validate the creativity and practical\nrelevance of this work, I suggest addressing the following points:\n1. The EGOR cathode and ORR cathode are separated by a Nafion 117 membrane. Does this membrane sufficiently\nprevent crossover between the two electrolytes? If available, please provide data or discussion on crossover performance.\n2. While the concept of recycling PET to produce GA in this system is highly noteworthy, the catalyst employed contains\nprecious metal Pd, which could be at odds with the claimed economic benefits of recycling. Please discuss the recyclability\nor recovery strategy for Pd and provide a perspective on the economic feasibility of this aspect. Additionally, consider\ncommenting on possible screening or substitution of other non-precious metal elements.\n3. As highlighted, one of the main discussion points of this paper is the recycling profits. Much of the techno-economic\nanalysis is contained on the supplementary information. Consider including more of this discussion in the main text if\nnecessary.\n4. The supporting information suggests that zinc oxide reacts with ethylene glycol to facilitate zinc electrodeposition. Does\nthis system avoid the passivation issues typically associated with ZnO formation in conventional ZABs? Please provide your\nthoughts on this point.\n5. How were the experimental setups for S-ZEAB and D-ZEAB configured? Please describe these in more detail (photos or\nfigures).\n6. For practical applicability, please discuss the potential for scaling up to larger electrode areas and cell formats.\n7. While the electrochemical performance profiles of the PET hydrolysate and pure EG electrolyte appear similar, what are\nthe expected impacts of by-products and impurities on the system if PET hydrolysate is used in a large-scale, high-capacity,\nlong-term setup?\n8. In the full-cell experiments, how was the operating temperature controlled? Additionally, what criteria were used to\nmanage or replace the zinc anode?", "reviewer_2": "The manuscript by Li et al. presents a dual-cathode zinc-ethylene glycol/air battery (D-ZEAB) that spatially decouples ORR\nand the ethylene glycol oxidation reaction (EGOR) onto separate cathodes, enabling concurrent electricity generation and\nelectroreforming of polyethylene terephthalate (PET) plastic waste into high-value C2 chemicals. In general, the authors did\na lot of work for this paper, while the novelty is not high to me. After struggling, I decided to reject it. Detailed review\ncomments are as follows:\n1. From plastic waste into high-value C2 chemicals is a great way in green chemistry, and here is the EGOR for converting\nEG to GA during charging for ZAB. However, the end-users only care about the ZAB price and energy density, and the GA\nrecovery is meaningless to them, plus the complex purify step to get pure GA. Therefore, the economic analysis does not\nmake sense to me.\n2. Since it is not practical for users to refresh the EG and electrolytes, this design changes the rechargeable ZAB to one-time\nuse with the continuous consumption of EG. Also, the two-cathode design will increase the capital cost.\n3. The PdCuCo catalyst exhibits remarkable catalytic performance for ethylene glycol. However, considering that the authors\ncompared the catalysts in the current reported literature based on the current activity current of Pd, it is necessary to\ndetermine whether this catalyst still has an advantage when compared based on the activity per unit area. And from the CV\ncurve in Figure 4, the oxidation overpotential of ethylene glycol is much higher than its theoretical potential. Even when the\ncurrent increases, it approaches the reaction potential of OER. Is the advantage of this system over the OER reaction\naccurate?\n4. From Supplementary Fig. S18, it seems there is no obvious current difference between the Pd and PdCuCo-0.9 catalysts\nin terms of ECSA-normalized CV curves, indicating the enhanced activity of PdCuCo-0.9 catalyst can only be attributed to\nthe increased ECSA instead of forming higher active sites, which conflicts with the finding and conclusion in this work.\nThis is critical.\n5. In this work, 0.1 M, 1 M, 4 M and 6 M KOH electrolytes were used for investigating the activity of catalysts and\nperformance of battery, making me confused. Why was there not constant electrolyte concentration used?\n6. For the battery test, “(1) a porous zinc plate (99.99% purity) as anode; (2) a charging cathode with 1.0 M KOH+1.0 M EG or\nPET hydrolysate solution as the electrolyte; (3) a discharging cathode containing 6.0 M KOH+0.2 M Zn(OAc)2 electrolyte;\nand (4) a Nafion 117 membrane separating the charging/discharging electrolytes.” 1 M and 6 M KOH electrolytes were used\nin the two cathodes, respectively. How do you balance the hydroxides produced and consumed from two cathodes? We\nknow that Nafion membrane can block the hydroxide transfer, while it can allow the potassium transfer. Also, the refreshing\nelectrolyte every 24 h is not practical. This part needs to be paid more attention.\n7. As can be seen in Figure 7e, the overpotential during the charging process is extremely high, especially under high\ncurrent conditions. A comparison with ZABs should be provided, and it should be considered whether the loss of charging\ncurrent in this system is meaningful without a significant reduction in charging voltage.\n8. The depiction of the reaction process and the device structure in Figure 1a is confusing and unclear. In Figure 1b, the\noxidation of ethylene glycol is labeled as the reaction of ethanol oxidizing to acetic acid. This may mislead the readers.", "reviewer_3": "This manuscript addresses the use of Pd-based catalysts in zinc–air batteries. The authors propose an electrocatalyst for\nethylene glycol/PET electrooxidation and oxygen reduction reactions. The innovative aspect of this work lies in the use of a\ndual-cathode battery, in which the charging reaction at one of the cathodes occurs via the oxidation of ethylene glycol\nderived from plastic waste. This approach makes the process both environmentally and commercially attractive, in addition\nto lowering energy costs, since the oxygen evolution reaction typically occurs at high overpotentials.\nThe manuscript is well-structured in both writing and organization of results, following a logical sequence that allows for\nsmooth reading and easy comprehension.The references used by the authors are current and consistent with the theme\nproposed in the manuscript.\nScientifically, the electrocatalyst was characterized using key surface techniques (XRD, EDS, XPS, SVB, and XAS), while\nits morphology and microstructure were examined using TEM and HAADF-STEM. The discussion of these characterization\nresults effectively clarifies the physical and chemical composition of the synthesized materials and how each element\ncontributes to the relationship between their chemical, electronic, and structural states in the studied reactions.\nRegarding the analysis of reaction intermediates, the authors employed NMR and FTIR to monitor the formation of the major\nspecies generated during the application of potential. Theoretical studies were conducted to provide a more in-depth\ndiscussion of the energetic contributions of Cu and Co incorporated into Pd, which, to some extent, shed light on the\nadsorption processes of ethylene glycol (EG) and its reaction intermediates.\nHowever, I have some comments on the manuscript that require minor revisions so that the final work meets the necessary\nstandards for approval and publication in Nature Communications.\nBelow are my comments:\n1.In my opinion, the authors should address the main motivation for studying the synthesized electrocatalyst in the\nintroduction. Numerous studies in the literature focus on the electrooxidation of alcohols, particularly ethylene glycol, which\nis a widely studied organic molecule for various applications. The rationale for selecting a PdCuCo-based catalyst remains\nunclear. A discussion of the main electrocatalysts used for this purpose could help clarify how this work advances the\nfrontiers of knowledge in this area.\n2. Another point that caught my attention concerns the use of such a high noble-metal loading, given that the current trend is\nto minimize or even eliminate the use of noble metals by replacing them with more abundant and less expensive\nalternatives. Palladium is among the most expensive noble metals. Considering the practical application of the proposed\nbattery, would the high Pd content be commercially viable? I invite the authors to comment on this aspect.\nAlso, the authors compare the performance of the synthesized material with others in the literature (Figure 4f). While it is\nimportant to highlight the performance of the material used compared to others, these comparisons often do not reflect\nreality. I say this because the amount of metal (Pd) used by the authors is significant, even with normalization. Other studies\nmay use non-noble metals or even a reduced amount of Pd, which results in lower current densities.\n3. Regarding the experiments presented, I have the following considerations:\n3.1. Indicate in the figures 4(a,e) which voltammetric cycles are shown (first, second, third, etc.).\n3.2. Regarding the in situ FTIR experiments, the authors used ATR-SEIRAS to analyze the intermediates formed during the\noxidation of EG. I recommend more details about the experimental procedure for obtaining the catalyst layer on the silicon\nprism coated with the metal film.\nI have some specific observations concerning the FTIR discussion.\nThe oxidation of organics on Pd is well discussed in the literature, and it is known that electrocatalytic activity depends on\nthe supporting electrolyte and pH. In alkaline media, bands at 1575, 14109, 1324, and 1075 cm⁻¹ can be attributed to the\nformation of intermediates such as glyoxal and glycolate, which can subsequently be oxidized to glyoxylate, with the\nappearance of a band at 1363 cm⁻¹ at higher potentials.\nAs the potential increases, a band may also appear at 1310 cm⁻¹, indicating the formation of oxalate. At high potentials,\nformate can be produced, with characteristic bands at 2820, 2740, 1386, and 1353 cm⁻¹.\nThe carbonate ion band (1370 cm⁻¹) is typically not visible in the spectra due to overlap with the band at 1409 cm⁻¹,\nalthough its presence can be inferred from the pronounced broadening of the latter.\nIt is also worth noting that glyoxal and glycolate are generally the primary products of EG electrooxidation at lower potentials.\nThen, taking into accoun the above considerations about this system, the authors state that the reaction mechanism involves\nthe formation of glycolaldehyde; however, in alkaline media, this species is rarely identified because it tends to undergo self-\npolymerization.\nRegarding CO, on Pd surfaces, its formation is not easily detected in either acidic or\nalkaline media. This suggests that the reaction pathway may proceed directly without CO\nas an intermediate, or that CO, being only weakly adsorbed on Pd, is rapidly oxidized.\nTherefore, given that the manuscript asserts the formation of CO as part of the mechanism, I encourage the authors to\nreconsider whether the proposed pathway is in fact the most plausible one."}, "author_response": "Point-to-Point Responses to Reviewers’ Comments\nReviewer #1:\nThe authors introduce the EGOR reaction to address the slow kinetics of the OER in\nconventional zinc–air batteries, and they further aim to achieve upcycling by employing\nPET plastic hydrolysate. As a result, they propose an environmentally friendly battery\nsystem with high charging efficiency that utilizes waste plastics. To further validate the\ncreativity and practical relevance of this work, I suggest addressing the following points:\nResponse: We thank the reviewer for acknowledging our proposal of an environmentally\nfriendly, high-efficiency battery system that utilizes waste plastics. Below, we have further\nhighlighted the novelty and practical relevance of this work.\n1. The EGOR cathode and ORR cathode are separated by a Nafion 117 membrane. Does\nthis membrane sufficiently prevent crossover between the two electrolytes? If available,\nplease provide data or discussion on crossover performance.\nResponse: We thank the reviewer for raising the important point of electrolyte crossover\nand have experimentally verified the efficacy of Nafion 117 membrane in our system. To\ndirectly address this point, we performed systematic ¹H NMR spectroscopic analyses of the\ncharging (EGOR side) and discharging (ORR side) electrolytes after 48 h of continuous\noperation at 10 mAh cm-2 per cycle. As shown in the Supplementary Fig. S46, the ¹H NMR\nspectrum of the charging electrolyte displays distinct signals at 3.6 ppm and 3.8 ppm,\ncorresponding to ethylene glycol (EG) and its intermediate, glycolic acid (GA), respectively.\nCritically, these characteristic peaks are entirely absent from the spectrum of the discharging\nelectrolyte, confirming that EG/GA species do not cross the membrane. Moreover, this\nexperimental procedure is consistent with previous reports. For instance, Wang et al. (Adv.\nMater., 2023, 35, 2304203) similarly used a Nafion 117 membrane to isolate anolyte (1.0\nM KOH+0.2 M furfural) and catholyte (1.0 M KOH) compartments in a furfural oxidation-\nassisted water electrolysis system. Thus, our direct experimental data, supported by prior\nliterature, confirm that the Nafion 117 membrane effectively prevents electrolyte crossover\nin our D-ZEAB system.\nSupplementary Fig. S46. 1H NMR spectra of the charing and discharing electrolytes\ncollected from the PdCuCo-0.9 based D-ZEAB after 48 h of operation at 10 mAh cm-2.\n1\n)u.a(\nytisnetnI\nC\nP\nE\nO\nA\nG\nR\n7h\nO\nR\ne\nR s id e\ns id e\n6\nm i c a l\nH\ns\nO\n2\nh\n5i\nf t (\nG\np\nA\np\n4m\n)\nE\n2\n2. While the concept of recycling PET to produce GA in this system is highly noteworthy,\nthe catalyst employed contains noble metal Pd, which could be at odds with the claimed\neconomic benefits of recycling. Please discuss the recyclability or recovery strategy for Pd\nand provide a perspective on the economic feasibility of this aspect. Additionally, consider\ncommenting on possible screening or substitution of other non-noble metal elements.\nResponse: We thank the reviewer’s insightful comment about the economic considerations\nregarding the use of Pd-based catalysts in our PET recycling system. We agree that the cost\nand recovery of noble metals are critical factors for the overall sustainability and economic\nviability of the process. In response to the comment, we have conducted rigorous\nexperiments on Pd recyclability and performed a comprehensive techno-economic analysis\n(Supplementary Tables S8-S11 and Figs. S48-S49). Our detailed responses and\ncorresponding revisions are summarized below:\n(1) Recyclability and recovery strategy for Pd\nTo recover Pd, we applied a simple acid dissolution-filtration method to the spent PdCuCo-\n0.9 catalysts. The catalyst was first separated from the gas diffusion layer substrate (Toray\nYLS-30T carbon paper), then stirred and dissolved in 1.0 M HNO , filtered, and vacuum\n3\ndried. Inductively coupled plasma optical emission spectrometry (ICP-OES) analysis of the\nrecovered residue confirmed a Pd purity of 94.2 wt.% and a recovery rate of 82.0 % (defined\nas the mass ratio of recovered Pd to the initial Pd in the catalyst). This laboratory-scale\nresults demonstrate that efficient Pd reclamation.\nFor industrial-scale application, established metallurgical processes, such as the patented\nmethod (CN 200810097804.2) involving calcination, acid leaching, and reduction, can\nachieve Pd recovery rates as high as 99.5%. Integrating such efficient Pd recovery is\nanticipated to substantially mitigate the initial material cost and improve the long-term\neconomic viability of the process.\n(2) Perspective on economic feasibility\nTo quantitatively address the economic concern, we updated the techno-economic analysis\nby comparing the D-ZEAB system with a conventional ZAB.\nFor the D-ZEAB, processing one ton of PET is totally $2,069.8, including miscellaneous\ncosts ($360.0) such as Pd recycling cost and GA separation cost (Supplementary Table S8).\nThe total output value is $2,346.3, derived from electricity ($82.5) and, more significantly,\nthe upgraded chemical products ($2,263.8). These high-value products constitute ~96% of\nthe total revenue (Supplementary Table S9), underscoring that the D-ZEAB system’s\neconomics are mainly driven by the upgrading of waste PET into a high-value chemical.\nConsequently, the D-ZEAB achieves a net profit of $276.5 per ton of PET (Supplementary\nFig. S48). In contrast, while the conventional ZAB has a lower initial cost ($1,603.1), its\nreliance solely on electricity output results in substantially lower profitability\n(Supplementary Table S10-S11, Fig. S49). This analysis confirms the significant economic\npotential and distinct value proposition of our integrated waste-to-chemicals strategy.\nZAB systems.\n(3) Screening and substitution with non-noble metals\nWe acknowledge that developing earth-abundant catalysts is a crucial long-term goal.\nHowever, for the specific anodic reaction in this work, i.e., the selective electrocatalytic\noxidation of EG to GA, the current state of the art is predominantly based on noble metals\n(e.g., Pd, Pt). Non-noble metal alternatives frequently suffer from insufficient selectivity\nand poor stability due to C-C bond cleavage (Adv. Mater., 2024, 36, 2401867; Chinese J.\nCantal., 2025, 73, 79-98).\nOur Pd-based catalyst was therefore selected to reliably establish the fundamental viability\nof the integrated D-ZEAB system, achieving the high activity and selectivity required for a\nrobust proof-of-concept. Building on this foundation, we fully agree with the reviewer that\nsustainable alternatives need to be explored. Our subsequent research will prioritize the\nsystematic screening of non-noble metal systems, including Co-based, Ni-based, and high-\nentropy alloys, to a logical and essential next step toward scalable application (Adv. Funct.\nMater. 2024, 34, 2404594).\n3. As highlighted, one of the main discussion points of this paper is the recycling profits.\nMuch of the techno-economic analysis is contained on the supplementary information.\nConsider including more of this discussion in the main text if necessary.\nResponse: To comply with the journal’s length constraints, the detailed techno-economic\nanalysis is presented primarily in the Supplementary Information. However, following the\ncomment, we have added a concise summary of the key profitability conclusion to the main\ntext (Page 25 in the revised manuscript):\n“A preliminary techno-economic analysis confirms the economic viability of the D-ZEAB\nsystem. While its initial cost is higher than that of a conventional ZAB by $466.7 per ton of\nprocessed PET, it generates a substantially greater total output value ($2,346.3 versus $82.5),\nyielding a net profit of $276.5 per ton (Supplementary Tables S8-S11 and Figs. S48-S49).”\n4. The supporting information suggests that zinc oxide reacts with ethylene glycol to\nfacilitate zinc electrodeposition. Does this system avoid the passivation issues typically\nassociated with ZnO formation in conventional ZABs? Please provide your thoughts on this\npoint.\n3\nstiforP\ntuptuO\ntupnI\nN e t l o\nD -Z E\nZ A B\n-1 0 0 0\ns\nA\ns\nB\n0V\na\nN\nlu e\ne t\n( $\np\n1)\nr\n0\no\n0\nf\n0\nit\n2 0 0 0\nResponse: Thank you for this critical observation. We apologize for any confusion from our\ninitial presentation and have revised the text in the Supporting Information for clarity as\nbelow. It should be clarified that in our constructed D-ZEAB system, ZnO does not directly\ncontact or react with the charging electrolyte (e.g., EG). To avoid potential\nmisunderstanding, we have appropriately revised the phrasing accordingly in Supporting\nInformation, as detailed below.\n“Overall reactiona:\n2ZnO + EG → GA + H O+2Zn (S9)\ncharging c a\na Note that this equation (S9) represents the net electrochemical process of the full cell, and\nZnO does not directly react with EG in the system; they are physically separated by a\nmembrane.”\nThe reaction equation S9 in the Supplementary Information represents the overall battery\nreaction, rather than a direct chemical reaction process between ZnO and EG. In the\nassembled D-ZEAB system (Fig. S35), a Nafion 117 membrane physically isolates the Zn\nanode from the EG-containing charging electrolyte, preventing any direct contact.\nRegarding the issue of Zn anode passivation caused by ZnO formation in traditional ZABs,\nit must be acknowledged that our D-ZEAB system cannot completely circumvent this\nphenomenon. However, by replacing the OER with the thermodynamically more favorable\nEGOR, the generation of superoxide radicals (O ⁻) in the charging electrolyte is avoided.\n2\ntheir absence in charging chamber of our D-ZEAB reduces the rate and extent of anode\npassivation.\nSupplementary Fig. S35. The (a) front and (b) side views of a D-ZEAB.\n5. How were the experimental setups for S-ZEAB and D-ZEAB configured? Please describe\nthese in more detail (photos or figures).\nResponse: In response to the comment, we have added annotated photographs of the D-\nZEAB (Supplementary Fig. S35, as shown above) and S-ZEAB (Supplementary Fig. S36,\nas shown below) configurations. The primary components of these two systems are detailed\nbelow.\n(1) Single-cathode Zinc-ethylene Glycol/air Battery (S-ZEAB)\ncomponents (Supplementary Fig. S36): (1) A porous zinc plate anode (99.99% purity, 1.5\nmm thickness); (2) a bifunctional cathode for the EGOR and ORR, fabricated by coating\nthe catalysts onto a gas diffusion layer (Toray YLS-30T carbon paper); and (3) a unified\nelectrolyte of 6.0 M KOH, 0.2 M Zn(OAc) , and 1.0 M EG.\n(2) Dual-cathode Zinc-ethylene Glycol/air Battery (D-ZEAB)\nThe D-ZEAB employs a unique dual-cathode configuration comprising six key components\n(Supplementary Fig. S35): (1) A porous zinc plate anode (99.99% purity, 1.5 mm thickness);\n(2) a dedicated charging cathode for the EGOR, using a PdCuCo catalyst-loaded gas\ndiffusion layer; (3) a charging electrolyte of 1.0 M KOH+1.0 M EG (or PET hydrolysate);\n(4) a Nafion 117 membrane, which physically separates the two cathode chambers; (5) a\ndedicated discharging cathode for the ORR, also based on the PdCuCo catalyst; and (6) a\ndischarging electrolyte of 6.0 M KOH and 0.2 M Zn(OAc) .\n2\n6. For practical applicability, please discuss the potential for scaling up to larger electrode\nareas and cell formats.\nResponse: We thank the reviewer for the valuable comment on the scalability of our D-\nZEAB, a crucial aspect for practical application. This initial study utilized lab-scale\nprototypes (1.0 cm2 electrode area) to establish fundamental principles and electrochemical\nperformance.\nWe agree that scaling up to larger electrode areas and configurations is a vital next step.\nWhile our current laboratory molds limit the rapid fabrication of larger assemblies, the\nmodular design of the D‑ZEAB is inherently scalable. This scalability is facilitated by the\npractical electrode fabrication method, i.e., coating catalysts onto a gas diffusion layer\n(Toray YLS-30T carbon paper), which can be readily adapted for larger formats. Our future\nwork will prioritize scale-up, including collaborations to fabricate custom hardware for\ntesting assemblies with electrode areas≥10 cm2.\n7. While the electrochemical performance profiles of the PET hydrolysate and pure EG\nelectrolyte appear similar, what are the expected impacts of by-products and impurities on\n5\nthe system if PET hydrolysate is used in a large-scale, high-capacity, long-term setup?\nResponse: We thank the reviewer for raising this critical question regarding the potential\nlong-term impacts of impurities in PET hydrolysate, which is essential for the practical\nimplementation and scalability of our D-ZEAB system.\nAs detailed in our composition analysis (Supplementary Fig. S20), alkaline hydrolysis of\nPET (4.0 M KOH) predominantly yields EG and TPA. In this alkaline medium, the\nsaturation concentration of soluble TPA (or potassium terephthalate) does not exceed 0.2 M.\nTo assess its impact on the EGOR performance of the catalysts, we performed dedicated\nelectrochemical tests. Cyclic voltammetry (CV) across a TPA concentration range of 0~0.2\nM shows that even at the maximum saturation concentration (0.2 M), the EGOR activity of\nour PdCuCo-0.9 catalyst decreased by only ~9% (Response Fig. R1). This minor decline is\nprimarily attributed to a slight reduction in electrolyte pH (ΔpH≈0.5) and ionic conductivity,\nwhich does not compromise the system’s operational integrity. Furthermore, the primary\nproduct of EGOR on the PdCuCo-0.9 catalyst is GA, with only trace amounts of formate\ndetected (Supplementary Fig. S45). The long-term cycling test (Fig. 7c) confirms that these\ntrace by-products have a negligible impact on the charge-discharge efficiency over short-to-\nmedium-durations.\nWe fully agree, however, that in large-scale, high-capacity, long-term operation, cumulative\nimpurities (e.g., TPA) and by-products (e.g., formate) could potentially lead to more\nsignificant issues, such as alterations in electrolyte composition, catalyst poisoning, or\ncomplexities in product separation. To mitigate these for future industrial implementation,\nwe recommend incorporating continuous pre- and intra-process purification steps to remove\nsoluble contaminants. This approach would ensure sustained system stability and efficiency\nover extended operational periods.\n300\nin 4.0 M KOH+1.0 M EG\nNo TPA\n+0.01 M TPA\n+0.05 M TPA\n200\n+0.1 M TPA\n)\n2 -m +0.2 M TPA\nc\nA\nm\n(100\nJ\n0\n0.0 0.3 0.6 0.9 1.2\nPotential (V vs. RHE)\nResponse Fig. R1. CV curves of PdCuCo-0.9 in 4.0 M KOH electrolyte containing different\nconcentrations of TPA.\n8. In the full-cell experiments, how was the operating temperature controlled? Additionally,\nwhat criteria were used to manage or replace the zinc anode?\nResponse: We thank the reviewer for emphasizing the importance of experimental rigor.\nTo ensure data accuracy and reproducibility, all battery tests adhered to the following controlled\nprotocols:\n6\n(1) Temperature control:\nAll electrochemical evaluations and battery tests were performed in a temperature-\ncontrolled chamber maintained at 25 °C (±1.0 °C) to ensure thermal consistency.\n(2) Zn anode management:\nTo prevent irreversible capacity loss from complete zinc depletion, a strict replacement\ncriterion was applied. During galvanostatic operation, the zinc anode was replaced once its\ndischarge voltage plateau fell below 1.0 V.\nReviewer #2:\nThe manuscript by Li et al. presents a dual-cathode zinc-ethylene glycol/air battery (D-\nZEAB) that spatially decouples ORR and the ethylene glycol oxidation reaction (EGOR)\nonto separate cathodes, enabling concurrent electricity generation and electroreforming of\npolyethylene terephthalate (PET) plastic waste into high-value C2 chemicals. In general,\nthe authors did a lot of work for this paper, while the novelty is not high to me. After\nstruggling, I decided to reject it. Detailed review comments are as follows:\nResponse: We sincerely appreciate the insightful evaluation of our manuscript and the\ndetailed feedback. Your recognition of our efforts is highly encouraging. In response to the\ncomment regarding novelty, we have significantly strengthened the manuscript with\nadditional data and refined our scientific narrative. Below, we detail the unique contributions\nand breakthroughs of this work across four critical dimensions. We hope that these\nclarifications will fully address your concerns and merit the manuscript’s reconsideration.\n(1) A pioneering D-ZEAB system: Bridging efficient energy conversion with chemical\nwaste upcycling\nCurrent ZABs and their derivatives (e.g., zinc-urea/air or zinc-methanol/air systems)\nuniversally employ a single-cathode configuration. This conventional design suffers from\nan intrinsic thermodynamic incompatibility between the ORR and anodic oxidation\nreactions (e.g., OER). This confliction inevitably leads to low energy efficiency, rapid\ncatalyst degradation, and poor cycling stability. Our work introduces a fundamentally new\ndevice architecture: the dual-cathode zinc-ethylene glycol/air battery (D-ZEAB). By\nspatially decoupling the ORR (discharging) and the ethylene glycol oxidation reaction\n(EGOR, charging) onto separate electrodes, we resolve this long-standing incompatibility.\nThis separation prevents the oxidative deactivation of the ORR catalyst and leverages the\nfavorable kinetics and low potential of EGOR (~0.2 V vs. SHE) to drastically reduce the\ncharging voltage. Theoretical calculations confirm an ultra-low charging voltage of ~0.623\nV for D-ZEAB, which is at least 1.030 V lower than that of conventional ZABs (Fig. 1b).\nCritically, this design bridges efficient energy storage with sustainable waste upcycling. The\nEG fuel can be derived from the hydrolysis of PET plastic waste, establishing a circular\neconomy model within a single device.\n(2) Development of a novel defect-rich PdCuCo trimetallene with record catalytic\nperformance\nIn tandem with the device innovation, we report a catalyst breakthrough: the synthesis of a\nnovel defect-rich PdCuCo trimetallene via an ethylenediamine-mediated solvothermal\napproach. This two-dimensional material features an ultrathin morphology (~1.0 nm, or ~5\natomic layers) and a high density of lattice defects, including distortions, vacancies, and\n7\ntwin boundaries. These structure features, combined with the electronically modulated Pd\nsites, produce a powerful synergistic effect. The optimized PdCuCo-0.9 catalyst achieves a\nrecord EGOR mass activity of 16.6 A mg -1, outperforming all previously reported Pd-\nPd\nbased catalysts (Fig. 4f and Table S3).\n(3) Unprecedented device efficiency and stability\nThe integration of the PdCuCo catalyst into our dual-cathode architecture yields\nunprecedented device performance. The resulting D-ZEAB achieves a record initial energy\nconversion efficiency (ECE) of 95.7%, which is the highest value reported for any\nconventional ZABs and liquid zinc-based batteries (Fig. 7e and Supplementary Table S7).\nThis system also demonstrates outstanding operational stability, sustaining performance\nover 848 cycles (1696 hours) with only a minimal decay in ECE, underscoring its practical\nviability.\n(4) Deep mechanistic insights into selective oxidation of ethylene glycol on PdCuCo\nTo elucidate the selective oxidation mechanism of ethylene glycol on the PdCuCo catalyst,\nwe have supplemented in situ Raman and electrochemical electron paramagnetic resonance\n(EPR) experiments (Fig. 5e-5g). Combining these results with in situ ATR-SEIRAS and\nDFT calculations reveals that the synergistic effects of the unique trimetallene structure,\nincluding lattice defects, compressive strain, and its ultra-thin architecture, predcisely\nmodulate the electronic state of the Pd active sites. This electronic modulation serves a dual\nfunction: it weakens the adsorption strength of the carbonyl (*CO) intermediate while\npromoting the in situ formation of critical Pd-O(H) species. Consequently, this engineered\nad\nsurface chemistry steers the reaction along a highly selective pathway from ethylene glycol\nto glycolic acid (Fig. 5h).\nIn summary, the novelty of our work is multi-faceted and profound, encompassing (1) a\ngroundbreaking dual-cathode device architecture, (2) a novel high-performance trimetallene\ncatalyst, (3) record-setting energy conversion efficiency and stability, and (4) a deep,\nexperimentally validated mechanistic understanding. We are confident that the revised\nmanuscript, now strengthened by additional data and clarified arguments, compellingly\ndemonstrates these significant and interlinked advancements.\nPdCuCo-0.9 at various applied potentials in 1.0 M KOH+1.0 M EG. In situ ATR-SEIRAS\nspectra for (c) PdCuCo-0.9 and (d) Pd under the same conditions. (e) EPR spectra of Pd,\nPdCu and PdCuCo-0.9 at 1.0 V vs. RHE. In situ Raman spectra for (f) PdCuCo-0.9 and (g)\nPd during EGOR. (h) Proposed EGOR pathways on Pd (left) and PdCuCo-0.9 (right),\nillustrating the shift toward selective glycolate formation.\n1. From plastic waste into high-value C2 chemicals is a great way in green chemistry, and\nhere is the EGOR for converting EG to GA during charging for ZAB. However, the end-\nusers only care about the ZAB price and energy density, and the GA recovery is meaningless\nto them, plus the complex purify step to get pure GA. Therefore, the economic analysis does\nnot make sense to me.\nResponse: We thank the reviewer for the valuable feedback and for acknowledging that\nconverting plastic waste into high-value C2 chemicals represents a promising direction in\ngreen chemistry. We appreciate the opportunity to further clarify the economic rationale and\npotential end-users for our D-ZEAB system.\nA core innovation of the D-ZEAB system is its transformation from a single-function energy\nstorage device into a dual-mode “electricity-chemicals co-production” platform. This design\nsignificantly expands its potential user base. While it serves conventional battery consumers,\nit also directly addresses the needs of industries focused on waste valorization and green\nchemistry, such as plastic recycling and sustainable chemical production. Below, we detail\nthe system’s practical advantages from key perspectives:\n9\n(1) Competitive performance in energy density and cycle life\nEnergy density is a primary metrics for battery performance. As suggested, we have added\ncomparative energy density data (Fig. 7b). The PdCuCo-0.9-based D-ZEAB delivers an\nenergy density of ~868 Wh kg-1. This value is not only comparable to its ZAB counterpart\nbut also represents a 13.8% improvement over a benchmark Pt/C+Pd black system (763 Wh\nkg-1), positioning it competitively among recently reported advanced ZABs (Supplementary\nTable S6). More importantly, by replacing the kinetically sluggish OER with the\nthermodynamically more favorable EGOR, our system achieves a superior cycle life of\n~1700 h, exceeding that of most reported ZABs (Supplementary Table S7). Therefore, for\nend-users prioritizing high energy density and extended lifespan, the D-ZEAB represents a\ncompelling and superior alternative to conventional ZAB technology.\nFig. 7b Energy density plots of D-ZEAB and ZAB based on different catalysts.\nSupplementary Table S6. Comparison of discharging performance between the PdCuCo-\n0.9 based D-ZEAB and the reported conventional ZABs.\nEnergy\nSpecific capacity\nCatalyst Battery Electrolyte density Ref.\n(mAh g-1)\n(Wh kg-1)\nPdCuCo-0.9 D-ZEAB 6.0 M KOH 868 796.3\nThis work\nPt/C+Pd black ZAB 6.0 M KOH 759 716\nFe,W-N-C ZAB 6.0 M KOH 953 781 Nat.\nCommun.,\n2025, 16:\nPt/C + IrO 2 ZAB 6.0 M KOH 780 678 8085.\nNat.\nCR-Co/ClNC ZAB 6.0 M KOH / 745\nCommun.,\n2024,\nPt/C ZAB 6.0 M KOH / 719 15:1675.\nNat.\nCommun.,\nRu -NiFe LDH ZAB 6.0 M KOH 271 /\nSA 2024, 15:\n9616.\n10\n)V(\negatloV\n1\n1\n0\n0\n.6\n.2\n.8\n.4\nZ\nD\nZ\nE\n-Z\nA B\n-Z\nA B\nn\nE A B (P\n(P d C u\nE A B (P\n(P t/C +\ne r g y d\nd C\nC o\nt/C\nP d\n4 0\ne n\nu C o\n-0 .9\n+ P d\nb la\n0s\nit\n-0 .9\n)\nb la\nc k )\ny ( W\n)\nc k )\nh k\n5\ng\nm\n-1Z\nn\nA\n)\nc\n8\nm\n0\n-2\nChem. A,\nPt/C+RuO ZAB 6.0 M KOH 841 /\n2 2025,13,\n14216.\nMater. Rep.\nEnergy,\nFe-N/MPCS500 ZAB 6.0 M KOH / 708\n2025, 5,\n100352\nAngew.\nFe V -NC ZAB 6.0 M KOH / 766\n1 1 Chem. Int.\nEd. 2025,\nPt/C ZAB 6.0 M KOH / 795 e202514542.\nEnergy\nZnFe-BMSAC+ IrO ZAB 6.0 M KOH 657\nMater. 2025,\nPt/C+IrO 2 ZAB 6.0 M KOH / 594 e70122.\nAppl. Catal.\nB: Environ.\nPt/C ZAB 6.0 M KOH / 733 and Energy,\n2026, 382,\n125969.\nInfoMat.\nPt/C+RuO ZAB 6.0 M KOH 684 2025,\n2\ne70077.\nInfoMat.\nFe Co-NC-4 ZAB 6.0 M KOH / 639 2025, 7,\n3\ne70032.\nMn /Mn -NSC ZAB 6.0 M KOH / 778.7 Nano\nSA AC\nEnergy,\n2025, 146,\nPt/C+RuO ZAB 6.0 M KOH / 666\n2 111498.\n(2) Economic viability driven by high-value chemical co-production\nWhile it is true that traditional ZAB users may not prioritize GA, the D-ZEAB system\ngenerates an entirely new revenue stream by converting waste PET into this high-value\nchemical, thereby appealing to a broader market. Our updated techno-economic analysis\nconfirms this shift. Although the initial input cost for the D-ZEAB ($2069.8) is higher than\nthat of conventional ZAB ($1603.1), its total output value is substantially greater ($2,346.3\nvs. $82.5). This yields a net profit of $276.5 per ton of processed PET, whereas the\nconventional system operates at a net loss (Supplementary Tables S8-S11 and Fig. S48-S49).\nCrucially, GA production accounts for ~96% of the total output value, underscoring that the\neconomic model has been fundamentally transformed from one based solely on electricity\nto one that profitably co-produces a valuable commodity.\nsystems.\n(3) Industrial feasibility of GA production and utilization\nCompared to conventional industrial routes for GA synthesis, the electrochemical reforming\nof PET plastic offers a more cost-effective, energy-efficient, and environmentally benign\npathway (Fig. 1c). In this work, we obtained a high-purity GA product at the laboratory scale\nthrough a straightforward procedure involving acidification, filtration, and rotary\nevaporation-recrystallization (Supplementary Fig. S47). While this purification process\ninvolves multiple steps, it requires no specialized equipment and is operationally simple,\nmaking it highly amenable to industrial-scale implementation. More importantly, the\nindustrial relevance of this integrated approach is strongly corroborated by a recent large-\nscale study (Nat. Commun., 2025, 16, 4440), which demonstrated a 500-watt stack system\nprocessing 20 kg of waste PET to electrochemically produce GA, followed by its\npolymerization to biodegradable polyglycolic acid (PGA). This study determined that the\nproduction cost of PGA via this route is competitive with general polyolefin plastics,\nsolidifying the economic and practical viability of the PET electroreforming strategy at an\nindustrial scale.\n2. Since it is not practical for users to refresh the EG and electrolytes, this design changes\nthe rechargeable ZAB to one-time use with the continuous consumption of EG. Also, the\ntwo-cathode design will increase the capital cost.\nResponse: We appreciate the reviewer’s comments regarding the practical implementation\nand cost-effectiveness of our D-ZEAB system. We would like to clarify several key points\nto address the concerns.\nFirstly, the D-ZEAB is fundamentally a rechargeable battery system. The 48-hour\nelectrolyte refresh cycle mentioned in our study was a laboratory protocol for a small-\ncapacity (300 mL) setup. In an industrial-scale deployment, the system would be integrated\nwith large-capacity storage tanks (e.g., multi-ton PET hydrolysate reservoirs), enabling\nlong-term autonomous operation through continuous flow, a well-established principle in\nflow battery technology. This design, combined with the system’s high energy density and\nenergy conversion efficiency, makes it highly suitable for practical applications such as\nbattery-swapping stations.\nSecondly, as we analysed in our response to the reviewer’s comment #1, the increased\n12\nstiforP\ntuptuO\ntupnI\nN e t l o\nD -Z E\nZ A B\n-1 0 0 0\ns\nA\ns\nB\n0V\na\nN\nlu e\ne t\n( $\np\n1)\nr\n0\no\n0\nf\n0\nit\n2 0 0 0\ncapital cost of the two-cathode design is more than compensated by significant long-term\nvalue creation through four key mechanisms: (ⅰ) Reduced Energy Input by replacing OER\nwith EGOR ($90.0 for D-ZEAB vs. $142.5 for a conventional ZAB); (ⅰⅰ) New revenue\nstream generated through the co-production of high-value GA ($2,263.8 per ton of processed\nPET); (ⅰⅰⅰ) The spatial separation of reactions prevents cathod oxidation, enhancing\ncatalyst durability and reducing replacement costs; (ⅳ) Our comprehensive techno-\neconomic model shows the D-ZEAB achieves a net profit of $276.5 per ton of PET, whereas\na conventional ZAB operates at a substantial net loss (-$1520.6).\nIn summary, the D-ZEAB system maintains the core functionality of a rechargeable battery\nwhile fundamentally transforming its economic model from pure energy storage to a\nsynergistic energy-chemicals co-production. The points above collectively demonstrate the\ntechnical practicality and commercial viability of our architecture.\n3. The PdCuCo catalyst exhibits remarkable catalytic performance for ethylene glycol.\nHowever, considering that the authors compared the catalysts in the current reported\nliterature based on the current activity current of Pd, it is necessary to determine whether\nthis catalyst still has an advantage when compared based on the activity per unit area. And\nfrom the CV curve in Figure 4, the oxidation overpotential of ethylene glycol is much higher\nthan its theoretical potential. Even when the current increases, it approaches the reaction\npotential of OER. Is the advantage of this system over the OER reaction\naccurate?\nResponse: It should be noted that the performance of noble metal-based electrocatalysts is\nprimarily benchmarked using mass activity (current normalized to noble metal loading, in\nmA mg-1) in literatures, rather than geometric activity. As presented in our original\nmanuscript, the optimized PdCuCo-0.9 catalyst exhibits an exceptional EGOR mass activity\nof 11.9 A mg -1, outperforming both control samples and previously reported Pd-\nPd\nbased catalysts (Fig. 4a and 4f).\nIn direct response to the reviewer’s comment, we have supplemented the evaluation with\ngeometric activity data. As shown in Supplementary Fig. S22, PdCuCo-0.9 achieves a\ngeometric activity of 248 mA cm-2, which is significantly higher than those of PdCu (165\nmA cm-2), Pd (106 mA cm-2), and commercial Pd black (86 mA cm-2). This performance\nalso remains highly competitive against other reported Pd-based EGOR catalysts\n(Supplementary Table S3.). Thus, even from the perspective of geometric activity, our\nPdCuCo trimetalene catalyst retains a clear and remarkable performance advantage.\nSupplementary Fig. S22. (a, b) CV curves and (c) geometric activity of various catalysts\nfor EGOR in 1.0 M KOH+1.0 M EG at a scan rate of 50 mV s-1.\nSupplementary Table S3. Comparison of EGOR performance for PdCuCo-0.9 and recently\n13\nreported Pd-based catalysts.\nMA Geometric area\nCatalyst Electrolyte Reference\n(A mg-1) activity (mA cm-2)\nPET hydrolysate\n16.6 248.1 This work\n(4.0 M KOH)\nPdCuCo-0.9\n1.0 M KOH+1.0 M EG 11.9 123.1 This work\nAdv. Mater., 2024,\nPdB aerogel 1.0 M KOH+1.0 M EG 6.7 /\n2401867.\nAngew. Chem. Int.\nIr-CuPd SMTs 1.0 M KOH+1.0 M EG 7.9 / Ed., 2024, 63,\ne202400281.\nAppl. Catal. B:\nTe-Pd NSs/C 1.0 M KOH+1.0 M EG 10.0 ~110 Environ., 2024, 343,\n123564.\nSmall, 2024,\nm-Pd Se NWs/C 1.0 M KOH+1.0 M EG 10.4 ~107\n7 2 2403448.\nSmall, 2024,\nPdBi-HNCs 1.0 M KOH+1.0 M EG 0.4 7.5\n2400939.\nAngew. Chem. Int.\nPt-CuPd SMTs 1.0 M KOH+1.0 M EG 8.1 / Ed., 2024, 63,\ne202400281.\nSmall, 2024, 20,\nD-PdCoZn NSs 0.5 M KOH+1.0 M EG 9.5 /\n2306341.\nChem.Eur. J., 2023,\nNi(OH)/Ni @Pd 1.0 M KOH+1.0 M EG 1.6 5\n16 29, e202303286.\nChem.Eur. J., 2023,\nPd/Fe-Nb O 0.5 M KOH+0.5 M EG 0.4 /\n2 5 475, 146050.\nAngew. Chem. Int.\nPd-Ni(OH) /NF 1.0 M KOH+0.5 M EG 0.8 / Ed., 2023, 62,\n2\ne202300094.\nAdv. Funct. Mater.,\nPd/a-MnO 1.0 M KOH+1.0 M EG 10.5 24.7\n2 2023, 33, 2211909.\nJ. Colloid Interface\nPdPtAg 1.0 M KOH+0.5 M EG 5.0 / Sci., 2023, 636,\n602.\nAngew. Chem. Int.\nPd-PdSe HNSs 1.0 M KOH+1.0 M EG 8.6 / Ed., 2022,\ne202200899.\nAdv. Funct. Mater.,\nPd-N /Cu-N 1.0 M KOH+1.0 M EG 1.9 ~80\n4 4 2022, 32, 2206887.\nChem. Commun.,\nRhCuAgPd/Pd 1.0 M KOH+1.0 M EG 6.6 /\n2022, 58, 7773.\nRegarding the advantages of replacing the OER with the EGOR in the D-ZEAB system,\nthe theoretical thermodynamic potential for EGOR is approximately 0.2 V (vs. SHE), which\nis substantially lower than the 1.23 V (vs. SHE) required for OER, as detailed in the\nSupplementary Information (“Calculations and Descriptions”). This establishes a clear\ntheoretical advantage for EGOR.\nThe overpotential, defined as the deviation from the theoretical equilibrium potential at a\ngiven current density (e.g., 10 mA cm-2), cannot be derived from the CV curves normalized\nby mass activity in Fig. 4. Therefore, it is inappropriate to infer comparable overpotentials\nfor EGOR and OER from that figure. In fact, our systematic experimental measurements\n14\nusing the PdCuCo catalyst reveal a significantly lower overpotential for EGOR compared\nto OER (Supplementary Fig. S13a). For instance, the PdCuCo-0.9 trimetallene requires only\n0.92 V (vs. RHE) to achieve 100 mA cm-2 for EGOR, which is approximately 1030 mV\nlower than the potential needed for OER at the same current density (Supplementary Fig.\nS13b). In summary, both theoretical analysis and experimental evidence consistently\ndemonstrate that EGOR offers a decisive advantage over OER, confirming its practical\nviability as a superior replacement in the D-ZEAB system.\nSupplementary Fig. S13. (a) LSV curves of PdCuCo-0.9 and Pd black in 1.0 M KOH with\nand without 1.0 M EG. (b) Comparison of the required potentials for EGOR and OER on\nPdCuCo-0.9 at various current densities.\n4. From Supplementary Fig. S18, it seems there is no obvious current difference between\nthe Pd and PdCuCo-0.9 catalysts in terms of ECSA-normalized CV curves, indicating the\nenhanced activity of PdCuCo-0.9 catalyst can only be attributed to the increased ECSA\ninstead of forming higher active sites, which conflicts with the finding and conclusion in this\nwork. This is critical.\nResponse: We thank the reviewer for this critical observation regarding the ECSA-\nnormalized CV curves in Supplementary Fig. S18. We agree that the calculated specific\nactivity enhancement (9.70 mA cm-2 for PdCuCo-0.9 vs. 9.17 mA cm-2 for pure Pd, or a 5.4%\nenhancement) appears modest when viewed in isolation. We appreciate the opportunity to\nclarify this point.\nIndeed, a substantial portion of the catalyst’s overall performance gain originates from the\ngeometric effect, which is attributed to the significant increase in ECSA afforded by the\nultrathin metallene architecture and abundant lattice defects. However, our conclusion\nregarding the formation of electronically superior active sites is based on a holistic analysis\nof functional performance, which extends beyond the specific activity from EGOR current.\nThe key evidence for enhanced intrinsic activity (the electronic effect) is demonstrated by\nthe catalyst’s dramatically improved operational properties:\n(1) Enhanced GA selectivity\nIn situ Raman and ATR-SEIRAS observations (Fig. 5) reveal that the PdCuCo-0.9 surface\neffectively suppresses C-C bond cleavage, favoring the conversion of EG to GA with higher\nselectivity than pure Pd. This altered reaction pathway is a direct consequence of electronic\nmodification of Pd sites by Cu and Co, which tunes the adsorption energy of key\nintermediates.\n15\n(2) Superior stability and weaker adsorption of carbonyl (CO*) intermediates\nThe 5-hour chronoamperometry tests (Fig. 4g) confirm that PdCuCo-0.9 maintains a higher\ncurrent retention compared to Pd. This operational stability is directly correlated with its\nweaker adsorption of carbonyl (CO*) intermediates, as evidenced by a 40 mV negative shift\nin the CO oxidation peak (0.77 V vs. RHE) compared pure Pd (Supplementary Fig. S27).\nThis lower potential signifies a fundamental electronic modification (e.g., downshift of the\nd-band center), which facilitates the rapid oxidation and removal of CO* intermediates and\nindicates a more active site for this critical process.\nIn summary, the geometric and electronic effects in PdCuCo-0.9 are synergistic and\ninseparable. The geometric effect provides a high density of accessible sites, while the\nelectronic effect creates sites that are intrinsically more selective and resistant to poisoning.\nTherefore, the modest 5.4% gain in specific activity (the 3.1-fold enhancement in mass\nactivity), and more importantly, the dramatic improvements in stability and selectivity,\nconsistently support our conclusion that the PdCuCo-0.9 possesses higher-quality active\nsites. We have revised the manuscript to present this interpretation more clearly and to avoid\npotential misunderstanding.\n5. In this work, 0.1 M, 1 M, 4 M and 6 M KOH electrolytes were used for investigating the\nactivity of catalysts and performance of battery, making me confused. Why was there not\nconstant electrolyte concentration used?\nResponse: We appreciate your attention to the use of different KOH concentrations in our\nstudy. These concentrations (0.1 M, 1.0 M, 4.0 M, and 6.0 M KOH) were deliberately\nselected based on established best practices, distinct experimental requirements, and safety\nconsiderations for each specific electrochemical process. The rationales for selecting each\nconcentration is as follows:\n(1) 0.1 M KOH for ORR performance evaluation\nThis is the widely adopted standard concentration for ORR studies. It provides sufficient\nionic conductivity for kinetic measurements while ensuring direct comparability of our\ncatalyst’s activity with reference data, as shown in Response Table R1.\nResponse Table R1. Comparison of ORR performance between PdCuCo-0.9 and the\nrecently reported Pd-based catalysts.\nCatalyst Electrolyte E Ref.\n1/2\nPdCuCo-0.9 0.1 M KOH 0.90 This work\nAdv. Funct. Mater., 2023, 33,\nPd/a-MnO 0.1 M KOH 0.87\n2\n2211909.\nACS Appl. Mater. Interfaces\nPd P S 0.1 M KOH 0.76\n3 2 8\n2022, 14, 12156.\nPd@Zn 0.1 M KOH 0.82 Chen, J. Catal. 2020, 382, 181.\nPd-HCS-700 0.1 M KOH 0.80 Chemistry 2020, 26, 12589.\nAppl. Catal. B: Environ. 2020,\nPd Au/C 0.1 M KOH 0.87\n3\n262, 118298.\nPd/MGN 0.1 M KOH 0.80 Appl. Catal. B: Environ. 2019,\n16\n244, 957.\nPd@NiO-0.5/C 0.1 M KOH 0.87 Nano Energy 2019, 58, 234.\nAu\n0.1 M KOH 0.90 ACS Catal. 2018, 8, 11287.\nNWs@Pd @PEI\n0.1\nACS Appl. Mater. Interfaces\nMnPd /C 0.1 M KOH 0.80\n3\n2018, 10, 8155.\nJ. Mater. Chem. A 2017, 5,\nNi@Pd /C 0.1 M KOH 0.86\n3\n9233.\nJ. Mater. Chem. A 2016, 4,\nPd/C-BAE 0.1 M KOH 0.86\n8337.\n(2) 1.0 M KOH for OER/EGOR performance evaluation\nSimilarly, A concentration of 1.0 M KOH is the established benchmark for studying\noxidation reactions, including OER and EGOR. It provides a sufficiently high OH⁻\nconcentration to drive the reaction kinetics effectively, while avoiding the excessive catalyst\ncorrosion and mass-transport limitations associated with extremely high concentrations.\nThis standard condition allows for a clear evaluation of intrinsic catalytic activity and\nensures direct data comparability with literature data (Supplementary Table S3, provided in\nthe response to Comment #3).\n(3) 4.0 M KOH for PET hydrolysis\nThe alkaline hydrolysis of PET is commonly conducted with concentrated bases. Standard\nindustrial and laboratory protocols often employ NaOH or KOH aqueous solutions (e.g., 4\nwt% to 20 wt%, or 0.4 to 2.2 M) at elevated temperatures (200-250 °C) and pressures (1.4-\n2.0 MPa). For our laboratory-scale study, we optimized these conditions to balance\nefficiency and operational safety. The selected 4.0 M KOH solution at 80 °C ensures a\npractical reaction rate while mitigating the significant hazards associated with handling\nconcentrated, hot alkaline solutions under pressure. These conditions are consistent with\nrecent literature on catalytic PET hydrolysis (Nat Commun, 2025, 16(1), 3426. DOI:\n10.1038/s41467-025-58813-3).\n(4) 6.0 M KOH for battery testing\nA 6.0 M KOH electrolyte was selected for zinc-air battery testing to meet the practical\nrequirements of high energy density and long-term cycling stability. This high-concentration\nprovides excellent ionic conductivity (600-650 mS cm-1) through dense K⁺ and OH⁻ ions,\nwhich is critical for supporting the zinc anode’s dissolution-deposition kinetics, especially\nunder high-current discharge. Furthermore, it helps prevent capacity fade by accelerating\nzinc dissolution and maintaining stable anode reaction kinetics. Consequently, 6.0 M KOH\nis a standard, essential parameter for evaluating practical battery performance, as\nbenchmarked in our Supplementary Table S6.\nSupplementary Table S6. Comparison of discharging performance between the PdCuCo-\n0.9 based D-ZEAB and the reported conventional ZABs.\nEnergy\nSpecific capacity\nCatalyst Battery Electrolyte density Ref.\n(mAh g-1)\n(Wh kg-1)\nPdCuCo-0.9 D-ZEAB 6.0 M KOH 868 796.3 This work\nFe,W-N-C ZAB 6.0 M KOH 953 781 Nat.\nCommun.,\n2025, 16:\nPt/C + IrO 2 ZAB 6.0 M KOH 780 678 8085.\nNat.\nCR-Co/ClNC ZAB 6.0 M KOH / 745\nCommun.,\n2024,\nPt/C ZAB 6.0 M KOH / 719 15:1675.\nNat.\nCommun.,\nRu -NiFe LDH ZAB 6.0 M KOH 271 /\nSA 2024, 15:\n9616.\nJ. Mater.\nChem. A,\nPt/C+RuO ZAB 6.0 M KOH 841 /\n2 2025,13,\n14216.\nMater. Rep.\nEnergy,\nFe-N/MPCS500 ZAB 6.0 M KOH / 708\n2025, 5,\n100352\nAngew.\nFe V -NC ZAB 6.0 M KOH / 766\n1 1 Chem. Int.\nEd. 2025,\nPt/C ZAB 6.0 M KOH / 795 e202514542.\nEnergy\nZnFe-BMSAC+ IrO ZAB 6.0 M KOH 657\nMater. 2025,\nPt/C+IrO 2 ZAB 6.0 M KOH / 594 e70122.\nAppl. Catal.\nB: Environ.\nPt/C ZAB 6.0 M KOH / 733 and Energy,\n2026, 382,\n125969.\nInfoMat.\nPt/C+RuO ZAB 6.0 M KOH 684 2025,\n2\ne70077.\nInfoMat.\nFe Co-NC-4 ZAB 6.0 M KOH / 639 2025, 7,\n3\ne70032.\nMn /Mn -NSC ZAB 6.0 M KOH / 778.7 Nano\nSA AC\nEnergy,\n2025, 146,\nPt/C+RuO 2 ZAB 6.0 M KOH / 666 111498.\nIn summary, the use of varied KOH concentrations was strategically selected to meet the\ndistinct requirements of each experimental stage: fundamental electrocatalyst evaluation\n(ORR/OER/EGOR), process optimization (PET hydrolysis), and practical device\nassessment (battery testing). We have revised the manuscript to explicitly state this rationale\nin the respective experimental sections for clarity.\n18\n6. For the battery test, “(1) a porous zinc plate (99.99% purity) as anode; (2) a charging\ncathode with 1.0 M KOH+1.0 M EG or PET hydrolysate solution as the electrolyte; (3) a\ndischarging cathode containing 6.0 M KOH+0.2 M Zn(OAc) electrolyte; and (4) a Nafion\n2\n117 membrane separating the charging/discharging electrolytes.” 1 M and 6 M KOH\nelectrolytes were used in the two cathodes, respectively. How do you balance the hydroxides\nproduced and consumed from two cathodes? We know that Nafion membrane can block the\nhydroxide transfer, while it can allow the potassium transfer. Also, the refreshing\nelectrolyte every 24 h is not practical. This part needs to be paid more attention.\nResponse: We thank the reviewer for raising this critical point regarding hydroxide balance,\nand electrolyte refreshment, which is essential for the long-term practical operation of our\ndual-cathode battery system. We fully agree that maintaining hydroxide (OH-) equilibrium\nbetween the two cathodes is a key-design challenge. In our proof-of-concept cycling tests,\nthe catholyte was renewed every 48 hours (not 24-hours) to periodically replenish the\nconsumed substrates (e.g., ethylene glycol) and mitigate concentration gradients, allowing\nus to focus on demonstrating the feasibility and long-term cycling stability of the integrated\ncatalyst system.\nWe acknowledge this is not a permanent solution. In direct response, our ongoing work is\nimplementing a redesigned electrolyte symmetry strategy. The core approach is to employ\na uniform, high concentration of KOH electrolyte (e.g., 6 M) in both cathode chambers. This\nfundamental change is expected to intrinsically balance the hydroxide generation and\nconsumption, moving towards a truly self-sustaining system architecture. The reviewer’s\ninsight is invaluable for guiding this effort to enhance the practical viability of this\ntechnology.\n7. As can be seen in Figure 7e, the overpotential during the charging process is extremely\nhigh, especially under high current conditions. A comparison with ZABs should be provided,\nand it should be considered whether the loss of charging current in this system is meaningful\nwithout a significant reduction in charging voltage.\nResponse: We thank the reviewer for the insightful comment regarding the charging voltage\ncharacteristics of our D-ZEAB system. In direct response, we have supplemented the rate\nperformance tests for the PdCuCo-0.9-based ZAB.\nAs shown in the updated Fig. 7e, the PdCuCo-0.9-based D-ZEAB exhibits significantly\nlower charging voltage plateaus than its ZAB counterpart. Notably, at a high current density\nof 150 mA cm-2, the D-ZEAB maintains a stable charging-discharging voltage profiles,\ndemonstrating superior energy efficiency and operational stability compared to the\nconventional ZAB. This enhancement arises from two key mechanistic advantages: (1) The\nthermodynamic benefits of replacing the high-overpotential OER with the more facile\nEGOR; (2) the dual-cathode architecture, which decouples the oxidation reaction from ORR,\neffectively mitigating catalyst oxidation and deactivation under high charging voltages.\nWe have further benchmarked this performance against state-of-the-art ZABs. As\nsystematically summarized in Response Table R2, the PdCuCo-0.9-based D-ZEAB\nachieves a lower charging voltage at 50 mA cm-2 than many recently reported systems,\nunderscoring its excellent charging capability.\nThe above comprehensive analyses provide robust evidence that the D-ZEAB system offers\na decisive advantage over traditional ZABs by substantially lowering the charging voltage,\n19\nthereby addressing the critical challenges of low energy conversion efficiency and stability.\nWe have revised the manuscript to include this comparative analysis and a more detailed\ndiscussion of mechanistic benefits.\nFig. 7. Performance of the rechargeable D-ZEAB. (a) Rate-discharging curves of S-ZEAB and D-\nZEAB based on PdCuCo-0.9. (b) Energy density plots and (c) galvanostatic charging/discharging cycling\nprofiles for the D-ZEAB using different catalysts at 5 mAh cm-2. (d) Energy conversion efficiency vs.\ncycle life for the PdCuCo-0.9-based D-ZEAB and previously reported conventional ZABs\n(Supplementary Table S7). (e) Rate-performance of the PdCuCo-0.9-based D-ZEAB and ZAB. (f) FE\nGA\nof PdCuCo-0.9-based D-ZEAB after different cycling time at 5 and 10 mAh cm-2. (g) 1H NMR spectrum\nand optical photograph (inset) of collected GA products. (h) Performance comparison among PdCuCo-\n0.9-based D-ZEAB and other representative Zn-based hybrid batteries.\nResponse Table R2. Comparison of the charging voltage at 50 mA cm-2 between PdCuCo-\n0.9 based D-ZEAB and the reported conventional ZABs.\nCatalyst Battery Charging voltage Ref.\nPdCuCo-0.9 D-ZEAB 2.0 V@50 mA cm-2 This work\nAngew. Chem. Int. Ed., 2025,\nGa/MnRuO ZAB 2.1 V@50 mA cm-2\n2 64, e202420481.\nJ. Energy Chem., 2024, 94,\nPt/C+RuO ZAB 2.4 V@50 mA cm-2\n2 778.\nLa CoFe O /3D-G ZAB 2.1 V@50 mA cm-2\n0.2 1.8 4 778.\nEnergy Storage Mater., 2024,\nCoTe @NCFs ZAB 2.3 V@50 mA cm-2\n2 71, 103654.\nChinese J. Catal., 2024, 58,\nFeNi@NC ZAB 2.2 V@50 mA cm-2\n206.\nAppl. Catal. B: Environ. and\nPtCoWO 700 NF ZAB 2.5 V@50 mA cm-2\nEnergy, 2024, 358, 124371.\nAdv. Mater., 2023, 35,\nCu-Co/NC ZAB 2.5 V@50 mA cm-2\n2300905.\nNiV O /AgMn ZAB 2.1 V@50 mA cm-2 Adv. Sci., 2022, 9, 2203663.\n2 6\nAppl. Catal. B: Environ.,\nCo O /NG ZAB 2.4 V@50 mA cm-2\n3 4-x 2020, 278, 119300.\n8. The depiction of the reaction process and the device structure in Figure 1a is confusing\nand unclear. In Figure 1b, the oxidation of ethylene glycol is labeled as the reaction of\nethanol oxidizing to acetic acid. This may mislead the readers.\nResponse: We thank the reviewer his/her careful attention to the details of Fig. 1 and for\nidentifying the issues in panel (a) and the labeling error in panel (b). We have thoroughly\nrevised the figure and its description as follows:\nPanel Fig. 1a has been redesigned to provide a clearer and more accurate illustration of both\nthe reaction process and the device structure.\nThe label in Fig. 1b has been corrected from “ethanol oxidizing to acetic acid” to “ethylene\nglycol oxidizing to glycolic acid”. We have also double-checked all related labels\nthroughout the manuscript to ensure consistency.\nand configuration for the D-ZEAB. (b) Comparison of the theoretical charging voltages between D-\nZEAB and typical ZABs. (c) Comparative analysis of the routes for industrial synthesis and\nelectroreforming synthesis of GA.\nReviewer #3:\nThis manuscript addresses the use of Pd-based catalysts in zinc–air batteries. The authors\npropose an electrocatalyst for ethylene glycol/PET electrooxidation and oxygen reduction\nreactions. The innovative aspect of this work lies in the use of a dual-cathode battery, in\nwhich the charging reaction at one of the cathodes occurs via the oxidation of ethylene\nglycol derived from plastic waste. This approach makes the process both environmentally\nand commercially attractive, in addition to lowering energy costs, since the oxygen\nevolution reaction typically occurs at high overpotentials. The manuscript is well-structured\nin both writing and organization of results, following a logical sequence that allows for\nsmooth reading and easy comprehension. The references used by the authors are current\nand consistent with the theme proposed in the manuscript. Scientifically, the electrocatalyst\nwas characterized using key surface techniques (XRD, EDS, XPS, SVB, and XAS), while its\nmorphology and microstructure were examined using TEM and HAADF-STEM. The\ndiscussion of these characterization results effectively clarifies the physical and chemical\ncomposition of the synthesized materials and how each element contributes to the\nrelationship between their chemical, electronic, and structural states in the studied reactions.\nRegarding the analysis of reaction intermediates, the authors employed NMR and FTIR to\nmonitor the formation of the major species generated during the application of potential.\nTheoretical studies were conducted to provide a more in-depth discussion of the energetic\ncontributions of Cu and Co incorporated into Pd, which, to some extent, shed light on the\n22\nadsorption processes of ethylene glycol (EG) and its reaction intermediates. However, I have\nsome comments on the manuscript that require minor revisions so that the final work meets\nthe necessary standards for approval and publication in Nature Communications. Below\nare my comments:\n1. In my opinion, the authors should address the main motivation for studying the\nsynthesized electrocatalyst in the introduction. Numerous studies in the literature focus on\nthe electrooxidation of alcohols, particularly ethylene glycol, which is a widely studied\norganic molecule for various applications. The rationale for selecting a PdCuCo-based\ncatalyst remains unclear. A discussion of the main electrocatalysts used for this purpose\ncould help clarify how this work advances the frontiers of knowledge in this area.\nResponse: We thank the reviewer for the insightful and constructive comments. In direct\nresponse, we provided the detailed design rationale below and have revised the Introduction\naccordingly to more clearly articulate the research motivation for developing the PdCuCo\ntrimetallene catalyst.\n“To enable high-performance operation of D-ZEAB, advanced electrocatalysts capable of\naccelerating both EGOR and ORR are essential. Palladium (Pd)-based materials are\npromising candidates for this dual functionality (Adv. Energy Mater., 2024, 14, 2304065;\nAdv. Funct. Mater., 2024, 34, 2405945). However, conventional Pd-based catalysts face\npersistent challenges in atomic utilization, mass activity, and long-term stability, which\nhinder their practical application. Alloying Pd with transition metals, termed alloying\nengineering, is a proven strategy to enhance performance while reducing precious metal\nconsumption. Trimetallic Pd-based alloys, in particular, offer superior compositional\nflexibility and structural stability (Adv. Mater., 2022, 34, 2202943). The synergistic\ninterplay of three distinct metals facilitates interfacial charge transfer through\nelectronegativity differences and orbital hybridization, optimizing the catalyst's electronic\nstructure and lowering reaction energy barriers (Adv. Mater., 2024, 36, e2311731; Appl.\nCatal. B: Environ., 2022, 309, 121228). Despite these advantages, research on Pd-based\ntrimetallic systems has predominantly focused on compositional tuning, often overlooking\nthe profound impact of deliberate structural modulation. Concurrently, structure engineering\nhas emerged as a powerful approach to modulate geometric and electronic properties\n(Energy Environ. Sci., 2019, 12, 1730-1750). Metallene, a class of new two-dimensional\n(2D) metallic materials with atomic layer thickness, exhibits exceptional characteristics\nsuch as a high density of low coordination, quantum size effects, and maximized atomic\nutilization, which are highly beneficial for electrocatalysis (ACS Nano, 2021, 16, 522-532).\nTheir enhanced atomic connectivity also promotes efficient electron transport. Therefore,\nthe integration of alloying and structure engineering to design a Pd-based trimetallene is\nexpected to retain ultra-high atomic utilization and synergistically optimize EGOR/ORR\nperformance through ternary component interactions and tailored architectures.”\n2. Another point that caught my attention concerns the use of such a high noble-metal\nloading, given that the current trend is to minimize or even eliminate the use of noble metals\nby replacing them with more abundant and less expensive alternatives. Palladium is among\nthe most expensive noble metals. Considering the practical application of the proposed\nbattery, would the high Pd content be commercially viable? I invite the authors to comment\non this aspect. Also, the authors compare the performance of the synthesized material with\nothers in the literature (Figure 4f). While it is important to highlight the performance of the\nmaterial used compared to others, these comparisons often do not reflect reality. I say this\nbecause the amount of metal (Pd) used by the authors is significant, even with normalization.\nOther studies may use non-noble metals or even a reduced amount of Pd, which results in\nlower current densities.\nResponse: We thank the reviewer for raising the questions regarding the noble metal loading\nand the commercial viability of our D-ZEAB system. Please find below our responses with\nsupporting evidence from both experimental validation and technoeconomic analysis.\n(1) Commercial feasibility of high Pd loading and recycling strategy\nWe acknowledge the prevailing trend toward minimizing noble metal usage. Our choice of\nPd-based catalysts, however, is driven by a specific requirement: non-precious metal\ncatalysts generally exhibit insufficient selectivity, failing to effectively suppress C-C bond\ncleavage during EGOR to produce GA with high efficiency. As reported in the literature, Pd\nremains the most effective catalyst for this selective transformation (Adv. Mater., 2024, 36,\n2401867; Chinese J. Catal., 2025, 73, 79-98).\nCrucially, the commercial viability of Pd-based catalysts is not defined by its initial loading\nalone but is fundamentally enabled by efficient recovery. We validated this by recovering\nPd from spent PdCuCo-0.9 catalyst using a simple acid dissolution-filtration method,\nachieving a recovery rate of 82.0% with a purity of 94.2 wt.% (ICP-OES). For industrial-\nscale Pd recovery, the patented method (e.g., CN 200810097804.2) enables a Pd recovery\nrate of up to 99.5% through calcination and sequential leaching of catalyst-coated electrodes.\nThis closed-loop recyclability transforms Pd from a consumable into a reusable asset,\nensuring that the PdCuCo catalyst-based D-ZEAB system maintains economic feasibility\ndespite initial noble metal investment. Our techno-economic analysis directly incorporates\nthis principle. As detailed in Supplementary Fig. S48 and Table S9, the D-ZEAB system\nyields a net profit of $276.5 per ton of processed PET. This profitability is almost entirely\ndriven (~96%) by the high-value GA output, demonstrating that the process economics are\ncompelling even with the initial noble metal investment, provided robust recycling is\nimplemented.\n(2) Context of performance comparison in Fig. 4f\nWe agree that comparing catalysts with different Pd loadings requires careful normalization.\nFor clarity, all catalysts in Fig. 4f are Pd-based, and their performance is presented as mass\nactivity (current normalized to the mass of Pd). The evaluation based on mass activity offers\na relatively fair and widely accepted approach for comparing noble metal-based catalysts,\nconsistent with common practice in the current literature. Furthermore, the primary\nobjective of this comparison is not to claim absolute superiority but to contextualize our\ncatalyst’s performance for the specific application of EG-to-GA conversion. The figure\ndemonstrates that our PdCuCo catalyst achieves highly competitive mass activity within the\nfield of Pd-based systems while enabling the selective and productive synthesis of a valuable\nchemical. This technical performance, when integrated with the recycling strategy outlined\nabove, forms the foundation of a viable commercial process.\nIn summary, through experimental validation of Pd recovery and technoeconomic analysis,\nwe demonstrate that the PdCuCo-based D-ZEAB system achieves both technical superiority\nand commercial viability.\n3. Regarding the experiments presented, I have the following considerations:\n3.1. Indicate in the figures 4(a,e) which voltammetric cycles are shown (first, second, third,\netc.).\nensure a stable, clean electrochemical surface. All CV curves presented are from the second\nsubsequent cycle, ensuring consistency. This detail has been added to the “Electrochemical\nMeasurements” section in the revised manuscript.\n3.2. Regarding the in situ FTIR experiments, the authors used ATR-SEIRAS to analyze the\nintermediates formed during the oxidation of EG. I recommend more details about the\nexperimental procedure for obtaining the catalyst layer on the silicon prism coated with the\nmetal film.\nResponse: We appreciate the reviewer's attention to the experimental details of the in situ\nelectrochemical ATR-SEIRAS measurements. As advised, the \"Methods\" section has been\nrevised to include an elaborated description of the catalyst layer preparation process on the\ngold-coated silicon prism, as shown below:\n\" In situ electrochemical ATR-SEIRAS measurements\nIn situ ATR-SEIRAS measurements were performed using a Nicolet iS50 FTIR\nspectrometer equipped with a liquid nitrogen-cooled mercury-cadmium-telluride (MCT)\ndetector at an incidence angle of ca. 60°. The catalyst ink was prepared by dispersing the\nas-synthesized PdCuCo catalyst powder in a mixture of isopropyl alcohol and Nafion\nsolution followed by ultrasonication for 30 minutes. 10 µL catalyst ink was drop-cast onto\nthe Au-coated silicon prism and dried gently under an infrared lamp to form a uniform\ncatalyst layer. The in situ ATR-SEIRAS spectra were collected from 0.1 to 1.1 V (vs. RHE)\nin N -saturated 1.0 M KOH containing 1.0 M EG, with an interval of 0.1 V.\"\nThank you again for your insightful comments, which have helped us improve the clarity and\nquality of our manuscript.\n4. I have some specific observations concerning the FTIR discussion. The oxidation of\norganics on Pd is well discussed in the literature, and it is known that electrocatalytic\nactivity depends on the supporting electrolyte and pH. In alkaline media, bands at 1575,\n1410, 1324, and 1075 cm⁻¹ can be attributed to the formation of intermediates such as\nglyoxal and glycolate, which can subsequently be oxidized to glyoxylate, with the\nappearance of a band at 1363 cm⁻¹ at higher potentials. As the potential increases, a band\nmay also appear at 1310 cm⁻¹, indicating the formation of oxalate. At high potentials,\nformate can be produced, with characteristic bands at 2820, 2740, 1386, and 1353 cm⁻¹.\nThe carbonate ion band (1370 cm⁻¹) is typically not visible in the spectra due to overlap\nwith the band at 1409 cm⁻¹, although its presence can be inferred from the pronounced\nbroadening of the latter. It is also worth noting that glyoxal and glycolate are generally the\nprimary products of EG electrooxidation at lower potentials. Then, taking into accoun the\nabove considerations about this system, the authors state that the reaction mechanism\ninvolves the formation of glycolaldehyde; however, in alkaline media, this species is rarely\nidentified because it tends to undergo self-polymerization.\nRegarding CO, on Pd surfaces, its formation is not easily detected in either acidic or\nalkaline media. This suggests that the reaction pathway may proceed directly without CO\nas an intermediate, or that CO, being only weakly adsorbed on Pd, is rapidly oxidized.\nTherefore, given that the manuscript asserts the formation of CO as part of the mechanism,\nI encourage the authors to reconsider whether the proposed pathway is in fact the most\n25\nplausible one.\nResponse: Thank you very much for your professional and detailed comments regarding\nthe in situ ATR-SEIRAS analysis and the proposed reaction mechanism. The points raised\nabout the behavior of intermediates in alkaline media and the EGOR pathway on PdCuCo-\n0.9 catalyst surfaces are highly valuable. We have carefully re-examined our spectroscopic\ndata and revised our discussion accordingly.\n(1) Re-examination of in situ ATR-SEIRAS data and reaction intermediates\nWe agree with the reviewer that glycolaldehyde is rarely identified in alkaline media due to\nits tendency to undergo self-polymerization. According to your recommendations, following\nan extensive literature review and re-examination of our in situ ATR-SEIRAS spectra, we\nhave revised the relevant discussions in the manuscript, as detailed below:\n“As displsyed in the in situ ATR-SEIRAS spectra (Fig. 5c), the characteristic peaks located\nat 1043 cm-1 and 1086 cm-1 are attributed to the stretching vibration of the GA species.40\nThe peaks at 1258 cm-1, 1362 cm-1 and 1336 cm-1 belong to the symmetric and\nantisymmetric stretching vibrations of COO- in GA.41 The intensity of above characteristic\npeaks increases with the increase of potential, indicating the continuous generation of GA\nduring EG oxidation. Notably, the GA-associated peak (1043 cm-1, 1086 cm-1 and 1258 cm-\n1) exhibits markedly higher intensity on PdCuCo-0.9 compared to those of pure Pd and PdCu,\nconfirming its superior selectivity for GA production (Fig. 5d and Supplementary Fig. S29).\nAdditionally, there is a distinct peak at 1646 cm-1 corresponding to the CH OHCO*\n2\nintermediate, which is a key intermediate in the EGOR process of the C pathway.42\nat various applied potentials in 1.0 M KOH+1.0 M EG. In situ ATR-SEIRAS spectra of (c) PdCuCo-0.9\nand (d) Pd at various applied potentials in 1.0 M KOH+1.0 M EG. (e) EPR spectra of Pd, PdCu and\nPdCuCo-0.9 with applied potentials. In situ Raman spectra of (f) PdCuCo-0.9 and (g) Pd. (h) Schematic\ndiagrams of the EGOR pathways on Pd (left) and PdCuCo-0.9 (right).\n(2) Clarification on carbonyl (CO*) intermediates and the proposed EGOR pathway\nThe reviewer raises valid concerns about CO detection on Pd surfaces. We clarify that the\nterm “CO” in the original manuscript was ambiguously defined. The term “CO*”\nintermediate has now been clearly defined in the revised manuscript, following established\nliterature (Adv. Mater., 2024, 36, 2401867), to refer broadly to carbonyl-containing\nintermediates adsorbed on the catalyst surface, whose strong adsorption can adversely affect\nactivity and C-C bond retention.\nNotably, our in situ ATR-SEIRAS spectra identified a specific, important carbonyl\nintermediate as CH OHCO*, not molecular CO. Moreover, our CO stripping experiments\n2\n(Supplementary Fig. S27) demonstrate that PdCuCo-0.9 has a lower CO oxidation potential\nthan Pd and PdCu control samples, indicating weaker adsorption of carbonyl (CO*) species.\nThis facilitates the rapid oxidation and removal of carbonyl intermediates during the EGOR\nprocess, eventually contributing to the observed superior EGOR stability.\nBased on the combined evidence from NMR, in situ Raman, and in situ ATR-SEIRAS,\nwe propose a revised and more plausible EGOR pathway on PdCuCo-0.9 in alkaline electrolyte:\nethylene glycol (CH OHCH OH) undergoes continuous deprotonation at low potentials to\n2 2\nform the CH OHC*=O intermediate, which is then attacked by *OH via nucleophilic\n2\nsubstitution at the α-C to yield glycolic acid (CH OHCOOH), as illustrated in\ndefensible mechanistic discussion.\nSupplementary Fig. S31. C pathway-dominated EGOR on PdCuCo-0.9 catalyst.\n2\nReviewer #1:\nThe authors have carefully and comprehensively addressed my previous comments. In\nparticular, the additional crossover analysis using 1H NMR, the clarification of the ZnO-EG reaction mechanism, and the expanded discussion on Pd recyclability and techno-\neconomic feasibility significantly strengthen the manuscript. The experimental\nconfigurations of S-ZEAB and D-ZEAB are now clearly illustrated, and the discussion on\nscalability and impurity tolerance has been substantially improved. I suggest that the\npotential scalability of the D-ZEAB system be briefly incorporated into the Conclusions\nsection, which would further strengthen the manuscript. With this minor revision, I\nrecommend the manuscript for publication in Nature Communications.\nResponse:\nThank you very much for your thoughtful consideration of our manuscript and valuable\ncomments and suggestions. According to your suggestion, the potential scalability of the D-\nZEAB system is incorporated into the “Discussion” section.\nReviewer #2:\nAll of my comments have been adequately addressed and I recommend acceptance of the\nmanuscript.\nResponse:\nThank you very much for your thoughtful consideration of our manuscript and valuable\ncomments and suggestions.\nReviewer #3:\nThe authors have carefully and constructively addressed all points raised during the review\nprocess, significantly improving the clarity, technical rigor, and mechanistic interpretation\nof the work.\nIn particular, the expanded description of the in situ ATR-SEIRAS methodology enhances\nthe reproducibility and transparency of the experimental approach. More importantly, the\nrevised discussion of the spectroscopic data and reaction mechanism is now better aligned\nwith the established literature on ethylene glycol oxidation in alkaline media, offering a\nmore accurate and convincing interpretation of the key intermediates involved. The\nclarification of the role of carbonyl-containing intermediates, supported by complementary\nelectrochemical and spectroscopic evidence, substantially strengthens the mechanistic\nframework proposed by the authors.\nOverall, this study presents a conceptually innovative and technically robust dual-cathode\nzinc–ethylene glycol/air battery architecture that successfully couples high-efficiency\nenergy conversion with the electrochemical upcycling of plastic waste into value-added\nchemicals. The combination of advanced catalyst design, operando characterization, and\ndevice-level demonstration represents a significant contribution to the fields of\nelectrocatalysis, sustainable energy storage, and circular chemistry.\nIn my opinion, the manuscript now meets the high standards of Nature Communications and\nis suitable for publication without further revision.\nResponse:\nThank you very much for your thoughtful consideration of our manuscript and valuable\ncomments and suggestions."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have carefully and comprehensively addressed my previous comments. In particular, the additional crossover analysis using 1H NMR, the clarification of the ZnO–EG reaction mechanism, and the expanded discussion on Pd recyclability and techno-economic feasibility significantly strengthen the manuscript. The experimental configurations of S-ZEAB and D-ZEAB are now clearly illustrated, and the discussion on scalability and impurity tolerance has been substantially improved. I suggest that the potential scalability of the D-ZEAB system be briefly incorporated into the Conclusions section, which would further strengthen the manuscript. With this minor revision, I recommend the manuscript for publication in Nature communications.", "reviewer_2": "All of my comments have been adequately addressed and I recommend acceptance of the manuscript.", "reviewer_3": "Dear Editor,\nI thank for the opportunity to review the revised version of this manuscript. The authors have carefully and constructively\naddressed all points raised during the review process, significantly improving the clarity, technical rigor, and mechanistic\ninterpretation of the work.\nIn particular, the expanded description of the in situ ATR-SEIRAS methodology enhances the reproducibility and\ntransparency of the experimental approach. More importantly, the revised discussion of the spectroscopic data and reaction\nmechanism is now better aligned with the established literature on ethylene glycol oxidation in alkaline media, offering a\nmore accurate and convincing interpretation of the key intermediates involved. The clarification of the role of carbonyl-\ncontaining intermediates, supported by complementary electrochemical and spectroscopic evidence, substantially\nstrengthens the mechanistic framework proposed by the authors.\nOverall, this study presents a conceptually innovative and technically robust dual-cathode zinc–ethylene glycol/air battery\narchitecture that successfully couples high-efficiency energy conversion with the electrochemical upcycling of plastic waste\ninto value-added chemicals. The combination of advanced catalyst design, operando characterization, and device-level\ndemonstration represents a significant contribution to the fields of electrocatalysis, sustainable energy storage, and circular\nchemistry.\nIn my opinion, the manuscript now meets the high standards of Nature Communications and is suitable for publication\nwithout further revision."}, "author_response": ""}]

Decision letter