bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating the Electrochemical CO2 Reduction Mechanism on Oxide-Derived Copper Using in Situ FTIR Spectroscopy
Authors: Delmo Ernest Pahuyo , Song Yihua , Wang Yian , Shao Minhua 
Published: February 2024

Oxide-derived copper (OD-Cu) electrocatalysts have been extensively used for CO2 reduction reaction (CO2RR) applications in recent years due to their capability to selectively produce valuable C2 compounds. The mechanism of CO2 reduction on these surfaces, however, is still not clearly understood. Using in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), we show how the copper pre-oxidation process can significantly influence the adsorption of various CO2RR intermediates. Upon mildly anodizing a Cu thin film, we observed a redshift on the *CO2
– band, indicating that the initial CO2 adsorption and activation step is promoted on the oxide-derived surface. Additionally, we observed a faster growth of the *COatop band for the anodized copper film at low overpotentials, which demonstrates how a high *CO coverage can be achieved on OD-Cu. Finally, for the first time, we observed the simultaneous formation of two bands at 1327 cm–1 and 1425 cm–1 on the anodized Cu thin film. Using DFT calculations, we show that these bands match the theoretical vibrational frequencies of the *COCHO dimer, a key intermediate of the C2 pathway. Furthermore, our calculations show that the thermodynamics of *CO and *CHO coupling can be improved in the presence of the subsurface oxygen sites in OD-Cu. Our findings reveal the different aspects through which the CO2 reduction mechanism can be improved on OD-Cu electrocatalysts as compared to metallic copper.
This work was financially supported by the Research Grants Council (16310419, 16309418, and 16304821) and the Innovation and Technology Commission (grant no. ITC-CNERC14EG03).
Real Time Analysis of the CO2 Reduction Reaction Products in a Cu-Gde Setup
Authors: Sajevic Urban , Parada Villarroel Walter Agustin Agustin , Nikolaienko Pavlo , Mayrhofer Karl J. J. 
Published: February 2024

The electrochemical reduction of CO2 (CO2RR) on copper is widely regarded as one of the most promising topics in green-energy research, due to it´s potential to produce a wide array of building block chemicals while consuming CO2 and utilizing renewable energy sources. Contrary to traditional electrolysers that utilize dissolved CO2, a gas diffusion electrode (GDE) approach is capable of circumventing the CO2 diffusion dependency and hence reach economically relevant currents of >300 mA/cm². Although GDE brings eventual industrial application closer, such systems suffer from short-lived stability, mostly on account of catalyst layer deactivation and GDE flooding. As a consequence, most GDE based electrolysers are incapable of reaching a true steady-state, rendering batch-based analyses such as gas chromatography less useful when it comes to studying sensitive properties such as on-set potentials, catalyst deactivation and product selectivity shifts.
In this work we present a novel set-up capable of exploring GDE-based systems and presenting both qualitative and quantitative response in real time. We base our system of a custom cell-design that is coupled to a proton transfer reaction mass spectrometer (PTR-MS) that analyses the liquid products and quadrupole mass spectrometer (QMS) for gaseous products analysis. As a proof of concept, we evaluate the CO2RR performance of copper based GDE´s in various electrolytes, showing how electrolyte´s pH influences properties such as product selectivity and on-set potentials. All experiments were conducted at industry-relevant currents of 200-600 mA/cm².
Tracking Mn and Zn in Rechargeable Aqueous Zn-MnO2 Batteries By Operando X-Ray Absorption
Authors: Liu Cheng , Wang Wenhai , Black Serra Ashley , Martin Diaconescu Vlad , Stievano Lorenzo , Simonelli Laura , Tonti Dino 
Published: February 2024

Zn-MnO2 batteries with mildly acidic electrolytes are a promising chemistry for large scale storage thanks to their remarkable energy density, low cost, and high safety. This is mainly obtained thanks to the high capacity of the Zn metal anode, and the nonflammable character of the aqueous electrolyte. MnO2 is one of the most common cathode of choice, not only for being Earth-abundant, but also because it can undergo a two-electron mechanism, which is however complex and still not fully understood. There is currently agreement in considering for discharge a MnO2 dissolution, leading to soluble Mn2+ and simultaneous precipitation of Zinc Hydroxide Sulfate (ZHS, ZnSO4[Zn(OH2)]3·xH2O). When charging the process is not simply reverted. In fact, a distinct electrochemical profile is observed, with at least two distinct plateaus and a third, apparently pseudocapacitive stage (Figure 1a). A similar multistage profile is observed during the second discharge. Although such profile is characteristic and observed with different MnO2 phases and architectures, the underlying mechanism remains elusive, as it seems to involve mainly poorly crystallized phases.
We studied the mechanism by operando X-ray absorption (XAS) at the Mn and Zn K-edges to follow speciation simultaneously and quantitatively in the cathode and in the electrolyte via principal component analysis. Beam intensity needed appropriate regulation to avoid interference with the experiment.
Simultaneous X-ray diffraction allowed precise correlation with the MnO2 dissolution and ZHS formation. We found evidence of Mn(III) intermediate occurring during local bond reorganization, which is inferred by the significant evolution of the absorption fine structure region (EXAFS) of the Mn K-edge (Figure 1b). In contrast, minor Zn spectral changes reflect primarily processes of precipitation and dissolution, suggesting that no Zn-Mn mixed phases form during cycling.

Figure 1
Understanding Aluminium Electrochemistry in Aqueous and Aqueous-Ionic Liquid Mixtures for Aluminium-Ion Batteries
Authors: Lahiri Abhishek , Chutia Arunabhiram 
Published: February 2024

Among various batteries, Aluminium ion batteries are potential low-cost alternatives to Li-ion batteries, which possess highest theoretical volumetric capacity of 8056 mAh cm-3 and a modest gravimetric capacity of 2981 mAh g-1. 1 However, due to passive layer formation of Aluminium and lack of suitable cathode materials, there are major challenges to overcome in order to accomplish a suitable Al-ion battery.
Here, we have studied the Al electrochemistry on electrodeposited MnO2 cathode and Zn anode in aqueous and aqueous-ionic liquid mixtures. Both from experiment and DFT calculations, we show that the presence of ionic liquid (1-ethyl-3-methylimidazolium trifluoromethanesulfonate) changes the Al solvation chemistry, which leads to a change in Al electrochemistry both on Zn and MnO2 (figure below). A strain-induced intercalation/deintercalation process was identified in MnO2 cathode leading to crack formation and capacity fading during Zn/Al-MnO2 battery cycling. By developing a MnO2-polymer matrix, a relatively stable average capacity of 150 mAh g-1 could be achieved over 50 cycles at a current density of 0.1 A g-1.

Acknowledgement:
The financial support by Royal Society grant (RGS\R2\212184) is gratefully acknowledged.

References

Faegh et al, Nat. Energy, 2021, 6, 21-29

Figure 1
Solid-State NMR Revealing the Impact of Polymer Additives on Li-Ion Motions in Plastic-Crystalline Succinonitrile Electrolytes
Authors: Möller Julia 
Published: February 2024

To enhance the safety of lithium-ion batteries (LIBs), alternatives to liquid electrolytes are widely studied. One of them is the plastic-crystal succinonitrile (SN) which can solvate various Li salts.[1] This system can be further extended by inserting polymers, bringing additional advantages such as higher melting points and the possibility of adjusting thermo-mechanical and electrochemical properties.[2]
The plastic-crystalline electrolyte consisting of the Li salt lithium bis(trifluoro-methanesulfonyl)imide (LiTFSI) dissolved in SN was extended by adding various thermoplastic polymers, namely, polyacrylonitrile (PAN), poly(ethylene oxide) (PEO), polyethylene carbonate (PEC), and polyvinylpyrrolidone (PVP). Even small amounts (10 wt %) of added polymer to the SN-base were found to impact the Li-ion mobility. Variable temperature investigations on structure and ion dynamics were performed using static and magic angle spinning (MAS) solid-state NMR and various relaxometry measurements. Influence of the Li-concentration and the polymers’ functional groups on the structure of SN and the resulting Li-ion mobility was elaborated. Activation energies and jump rates of the Li-ions were determined.
As a result, the PAN containing system stands out to be a promising candidate for application in future LIBs as it shows high ion mobility, low activation energy, and a high potential for further modifications. Solid-state NMR turned out to be a reliable method and a good alternative to impedance spectroscopy measurements for investigating ion mobility behaviour providing even more information.[3]
Literature:
[1] S. Long, D. R. MacFarlane, M. Forsyth, Solid State Ionics
2004, 175, 733.
[2] N. Voigt, L. van Wüllen, Solid State Ionics
2014, 260, 65.
[3] J. Möller, V. van Laack, K. Koschek, P. Bottke, M. Wark, J. Phys. Chem. C
2023, 127, 1464.
Exploring the Role of Molecular Intercalants in Electrochemical Production of Graphene-Based 2D Materials
Authors: Xia Zhenyuan , Zhang Daheng , Sasidharan Sankar , Sasikala Devi Assa Aravindh , Shi Jiahao , Su Jian-Hua , Huang Jinhai 
Published: February 2024

Since the discovery of graphene, two-dimensional (2D) materials have gained extensive attention due to the unique material properties from their reduced dimensionality. Numerous techniques have been thoroughly investigated for the fabrication of graphene-based 2D materials. Among them, electrochemical synthesis is one of the most promising approaches for the large-scale production of 2D materials with tunable properties [1-3]. Especially, intercalation of various ions/molecules electrochemically driven in between the graphene sheets plays the key role in the synthesis of single or few-layer 2D materials. However, the influence of molecular intercalants is still poorly understood.
In this work, we studied different types of intercalants (i.e., ClO4
-, PF6
-, BF4-, HSO4
-) and explored the inserting process of molecular anions in-between the weekly-bonded layered materials driven by electrochemistry. Combining the cyclic voltammetry, XRD, Raman and density functional theory computation modeling, we can monitor the intercalation behavior of different anions and evaluate the contribution of intercalants in the high-yield production of graphene by electrochemical exfoliation. By optimizing the use of certain molecular intercalants, high exfoliation yield (>80 %) of graphene nanosheets with moderate oxidation damage and good electrochemical stability was achieved assisted by electrochemical exfoliation. Our study provides new insights into the electrochemical production of graphene-based 2D materials and suggests that the introduction of molecular intercalants is a promising tool for the controlled synthesis of layered 2D materials.
Reference:
(1) Xia, Z. Y.; Pezzini, S.; Treossi, E.; Giambastiani, G.; Corticelli, F.; Morandi, V.; Zanelli, A.; Bellani, V.; Palermo, V. The Exfoliation of Graphene in Liquids by Electrochemical, Chemical, and Sonication-Assisted Techniques: A Nanoscale Study. Advanced Functional Materials
2013, 23 (37), 4684-4693. DOI: 10.1002/adfm.201203686.
(2) Xia, Z. Y.; Maccaferri, G.; Zanardi, C.; Christian, M.; Ortolani, L.; Morandi, V.; Bellani, V.; Kovtun, A.; Dell'Elce, S.; Candini, A.; et al. Dispersion Stability and Surface Morphology Study of Electrochemically Exfoliated Bilayer Graphene Oxide. Journal of Physical Chemistry C
2019, 123 (24), 15122-15130. DOI: 10.1021/acs.jpcc.9b03395.
(3) Cao, J. Y.; He, P.; Mohammed, M. A.; Zhao, X.; Young, R. J.; Derby, B.; Kinloch, I. A.; Dryfe, R. A. W. Two-Step Electrochemical Intercalation and Oxidation of Graphite for the Mass Production of Graphene Oxide. Journal of the American Chemical Society
2017, 139 (48), 17446-17456. DOI: 10.1021/jacs.7b08515.
High-Entropy Alloys as Oxygen Reduction Reaction Electrocatalysts for Proton Exchange Membrane Fuel Cells Application
Authors: Wan Daniel , Chen Guangyu , Yan Jay , Wang Feng , Shao Minhua 
Published: February 2024

High entropy alloys (HEA) are complex multi-element materials. Owing to their multi-elemental nature, they can finetune surface adsorption energy and active sites which make them appealing to various catalytic reactions. HEI is a subclass of HEA that consist of an ordered alloy structure rather than a random alloy structure. The order-ness may induce more stable structures and uniform active sites, which in turn enhance the durability and activity under catalytic conditions. Here, we have synthesized a HEI(Pt40Ni20Co20Mn10Ir10) supported on porous carbon via a seed-mediated impregnation method. The intermetallic characteristics with periodic trends can be seen in the HAADF-STEM image (Fig. 1a). Based on the atomic arrangement, the HEI resembled a L12 structure. The corresponding EDX mapping the catalyst also showed the presence of all alloying species in the nanoparticles. The catalyst performance of the catalysts was evaluated in a 3-electrode liquid cell set-up with catalyst coated glassy carbon rotating disk electrode, Ag/AgCl and Pt mesh as working, reference and counter electrode, respectively. The catalyst’s mass activity (MA) was calculated based on the result obtained from ORR polarization test conducted under O2 saturated 0.1M HClO4. The initial mass activities for PtCo and HEA in ORR were 0.81 and 1.23 A mg-1
Pt, respectively (Fig. 1b), while that of Pt/C was only 0.26 A mg-1
Pt. A subsequent accelerated degradation test (ADT) was conducted under Ar-saturated 0.1M HClO4 with 0.6-1.0 V vs RHE square-wave cycling (3s hold at each potential) for 30k cycles. MA was measured after 10k and 30k cycles. HEA retained a MA of 0.48 A mg-1
Pt after the ADT, above the DOE target (0.44 A mg-1
Pt). We also compared our HEI samples synthesized with different annealing temperatures and duration (Fig. 1c), and it showed that 800◦C with 20 mins temperature hold showed the highest MA and electrochemical surface area (ECSA).
Extended X-ray absorption spectroscopy (EXAFS) for the catalyst has also been conducted to further elucidate the structural-performance relationship of HEI (Fig.1d). From Pt L3 edge EXAFS fitting, the fitted R space showed that the Pt-Pt bond length was around 2.704 ± 0.004 Å, which was same as that of the PtCo (Fig. 1e). Therefore, it is believed that both HEI and PtCo has the same strain effect but HEI possessed stronger ligand effect than PtCo due to its unique Pt-M coordination, hence resulting in superior ORR performance over PtCo and Pt.

Figure 1
Dramatic Electrochemical Tuning of the Plasmonic Spectrum of a Metal Nanoparticle on a Mirror
Authors: Vaskevich Alexander , Chuntonov Lev , Basu Arghyadeep , Kaplan-Ashiri Ifat , Haran Gilad 
Published: February 2024

Enhancement of electric fields in the nanometric gap between plasmonic nanostructures is widely exploited for sensing, enhanced spectroscopies and photochemistry. Plasmonic properties of nanostructures with ultrathin gaps, such as nanoparticles (NPs) positioned on a flat metal surface (a mirror), have attracted much attention in recent years [1]. We studied the effect of electrochemical control on the plasmonic properties of single Au and Ag NPs on a mirror. We found that the coupled plasmonic resonance could be reversibly tuned over a range of tenths of nanometers, more than an order of magnitude higher than expected based just on capacitive charging of the NPs.
Our experimental system consisted of single Au or Ag NPs (50 nm – 100 nm) adsorbed on a self-assembled monolayer (SAM) of either polyelectrolytes, cysteamine (CEA) or ethanedithiol (EDT) deposited on an atomically flat 100nm thick Au electrode prepared by template stripping. The NPs were either bare (prepared by H2 reduction) or citrate-stabilized and the system was immersed in a basic solution.
Coupling to the mirror electrode resulted in the appearance of several bands in the plasmonic spectrum of individual NPs, as measured by dark-field microspectroscopy (Fig. 1a), and the lowest-energy band could be attributed to the coupled plasmon. Variation of the electrode potential generated a giant, though reversi shift of the spectrum. A plot of the peak position of the coupled plasmon band displayed an S-shaped, phase-transition like behavior (Fig. 1b).
This remarkable result could not be observed with individual NPs deposited on non-metallic surfaces, and can therefore be attributed to a dramatic modulation of the coupling between the particles and the mirror with electrode potential.
Figure 1. Scattering spectra (a) and variation of the spectral position of the coupled plasmon peak (b) of bare AuNP (ca. 60 nm) on CEA/Au electrode. Inset in (a): Scheme of NP on the mirror.

References

[1] J. J. Baumberg, J. Aizpurua, M. H. Mikkelsen, D. R. Smith, Nature Materials
2019,18, 668,

Figure 1
Electrochemical Reduction of Nitrate to Ammonia Using Copper Oxide Catalysts
Authors: Kwon Taesung , Cho Hyeon Beom , Nam Ki Min 
Published: February 2024

The electrochemical conversion of nitrates to ammonia offers a promising alternative to the energy- and resource-intensive Haber-Bosch process while simultaneously removing nitrates, a common water pollutant. However, this process is hindered by the eight-electron reduction required to convert nitrate to ammonia, as well as competing hydrogen evolution reactions and other nitrate reduction pathways. Efficient catalysts are essential to address these challenges, and recent studies suggest that oxide catalysts with oxygen vacancies can optimize adsorption energies of intermediates and improve catalytic performance. Copper oxides with oxygen vacancy display high ammonia selectivity in nitrate reduction, but the complexity in vacancy enrichment and the inferior hydrogen adsorption on oxides make nitrate reduction an inefficient process.
In this study, a CuOx composite electrode was synthesized using the hydrothermal method, and its performance was evaluated for efficient conversion of nitrate to ammonia. The synthesized CuOx nanostructure was characterized using X-ray diffraction to determine phase purity and crystal structure, while surface morphology of prepared samples was examined with high resolution transmission electron microscope. The results of X-ray photoelectron spectroscopy suggested that there were abundant oxygen vacancies on the surface of the CuOx, which can act as nitrate adsorption sites. The obtained CuOx composite electrode performs at a high ammonia Faradaic efficiency of over 80% and long-term stability due to interfacial coupling effects. These findings highlight the potential of CuOx catalysts for electrochemical nitrate reduction, offering new opportunities for sustainable nitrogen management and water treatment.
“Dewetted” Metal Nanoparticles As a Platform to Study Electrocatalytic Reactions
Authors: Harsha Shreyas , Sharma Rakesh , Dierner Martin , Casanova Andrea , Baeumer Christoph , Makhotkin Igor , Mul Guido , Ghigna Paolo , Will Johannes , Spiecker Erdmann , Altomare Marco 
Published: February 2024

Metal nanoparticles (NPs) are key for catalytic applications such as electrocatalysis. Besides morphology and composition, also structural features largely affect their performance [1]. Recent work uncovered correlations between exposed facets [2,3] and grain boundaries’ density [4,5] with nanoparticles’ activity, selectivity, and stability.
The present contribution addresses the effects of structural features of Pt NPs on the electrochemical performance in the hydrogen evolution reaction (HER). Our approach for the synthesis of metal NPs is distinct in that we produce a "monolayer" of spaced and defined Pt NPs directly on the electrode surface by controlled solid-state dewetting, i.e., by controlled heat-induced agglomeration of thin Pt films into particles [6,7] – see Fig. a. We use magnetron sputtering to deposit Pt films on electrically conductive substrates, followed by thermal treatment in a suitable environment. The resulting NP "monolayers" are tested for electrochemistry without using any binder or ionomer. By varying the duration of the thermal treatment systematically, we observe that dewetted Pt NPs show an evident increase of the ECSA area-specific HER activity compared to as-sputtered films – see Fig. b. This activity trend is consistent in the range of Pt particles’ size investigated (3-60 nm – see size control in Fig. c). The present contribution provides an analysis of the influence of NPs’ features, such as structure, grain size, grain boundaries’ density, and electronic metal-support interaction (EMSI), on the HER activity.
In a broader perspective, controlled dewetting allows to precisely tune the properties of metal NPs while at the same reduces the electrode complexity. Advantages are that single-crystalline, well-faceted NPs can be produced on desired electrically conductive substrates (see control of exposed facets in Fig. d). Moreover, dewetted NPs are free from impurities or additives, can be formed with desired composition by tuning the composition of the parent metal film, and can be formed on flat electrode geometries, which is ideal to minimize mass transport limitations and to enable accessibility for spectroscopic techniques.
[1] Zhu et al., Chem. Rev. 2020, 120 (2), 851.
[2] Lim et al., ACS Catal. 2021, 11 (12), 7568.
[3] de Gregorio et al., ACS Catal. 2020, 10 (9), 4854.
[4] Feng et al., J. Am. Chem. Soc. 2015, 137 (14), 4606.
[5] Zhu et al., Nano Research 2020 13:12 2020, 13 (12), 3310.
[6] Thompson, C.V., Annu. Rev. Mater. Res. 2012, 42, 399.
[7] Altomare et al., Chem. Sci. 2016, 7 (12), 6865.

Figure 1
How the Facet Edge Controls the Overall CO Oxidation in Nanoporous Gold: Combined Atomistic Characterization/DFT Study of Residual Ag Distribution and Catalytic Activity
Authors: Ayadathil Prajwal , Sandupatla Aditya , Chatterjee Abhijit 
Published: February 2024

Nanoporous gold (NPG) formed via dealloying/selective dissolution of the Au−Ag alloy is known to be catalytically active toward CO oxidation reaction (COR) even at room temperature. The atomistically resolved NPG structure is obtained by simulating the dealloying of Au25Ag75 nanoparticles using a combination of kinetic Monte Carlo and molecular dynamics. The effect of adsorbed O is included. The experiment-like NPG structures from these computer simulations are characterized. We map the surface of NPG, determine the diverse binding sites, and assess their role in catalysing the COR. Local surface Ag composition, population density of undercoordinated Au/Ag atoms, and cluster size distribution of surface Ag atoms are measured. A high density of dislocation defects is found in the simulated structure. The rate-determining steps, namely, O2 binding and dissociation, are probed using density functional theory. We conclude that O2 binding/dissociation is facilitated at the facet edge. Residual Ag at the edge aids in the capture of O2. Subsequently, O2 dissociates after spilling over to Au sites at the facet edge. These conclusions are confirmed by showing that the normalized facet edge length of NPG and supported Au nanoparticles is linearly correlated to the experimental turnover frequency.
Keywords: nanoporous gold, dealloying, CO oxidation, elemental distribution, density functional theory, molecular dynamics, Monte Carlo
Figure : Dealloying of Au-Ag NP to get NPG which has high catalytic activity for COR

Figure 1