bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Mapping the Nanoscale Photochemical Activity of Photonic Nanostructures
Authors: Henrotte Olivier , Naldoni Alberto
Published: August 2024

In order to build reliable structure-activity relationships for the design of more efficient photocatalysts, it is crucial to progress the fundamental understanding of nanosystems interacting with light. Their photochemical reactivity is dictated by the nanoscale behavior. In this contribution, I will show our recent efforts to delve in this exciting field by leveraging a scanning photoelectrochemical microscope. The nanoscale detection of the molecular products generated by the photocatalysts unlocks the visualization of unexpected reactivity behavior and aid to the design of new materials.
(Invited) Thermal and Plasmon-Mediated Catalytic Transfer Hydrogenation Reactions on Nanostructured Metal Surfaces
Authors: Wang Hui
Published: August 2024

Catalytic hydrogenation reactions play crucial roles in fine chemical production and pharmaceutical synthesis. Compared to direct hydrogenation of organic compounds with pressurized hydrogen gas, catalytic transfer hydrogenation reactions using inexpensive and readily accessible small molecules as hydrogen-donors has been considered as a more versatile, scalable, and sustainable pathway toward enhanced chemoselectivity under mild reaction conditions. Noble metal nanoparticles, especially those within the sub-5 nm size regime, can efficiently catalyze the dehydrogenation of a series of hydrogen-storing molecules, such as ammonia borane, hydrazine, formaldehyde, formic acid, and isopropanol, to produce surface-adsorbed hydrogen species that actively hydrogenate a variety of organic substrate molecules. The transfer hydrogenation/hydrogenolysis reactions are mechanistically complex, and may occur selectively along multiple distinct pathways, exhibiting kinetic features signifying the Langmuir–Hinshelwood, Eley–Rideal, autocatalysis, and reversible reaction mechanisms, respectively, depending on the compositions of the metal catalysts and the chemical nature of the hydrogen donors. In this talk, I will share with the audience some new insights concerning the detailed mechanisms of transfer hydrogenation reactions over metal nanocatalyst surfaces. We employ surface-enhanced Raman scattering (SERS) as an in situ fingerprinting spectroscopic tool to precisely resolve the detailed structural evolution of molecular adsorbates during catalytic reactions, based upon which the key intermediates along different reaction pathways are unambiguously identified. The results of deliberately designed in situ SERS measurements show that the chemoselective transfer hydrogenation of nitrophenyl isocyanide by ammonia borane may proceed on noble metal nanocatalyst surfaces selectively through either a unimolecular or a bimolecular pathway, depending on how the nitrophenyl isocyanide adsorbates interact with the metal nanoparticle surfaces. The experimental observations are corroborated by density functional theory calculations, which shed light on the underlying relationships between catalyst-adsorbate interactions and reaction pathway selection. We have further demonstrated that the photoexcited plasmonic hot carriers in the metal nanoparticles can be effectively harnessed to fine-regulate the activation energy barriers associated with the rate-limiting steps for the transfer hydrogenation of nitrophenyl isocyanide on Pd nanocatalyst surfaces when ammonium formate serves as the hydrogen donor. Our results clearly demonstrate the feasibility of using plasmonic hot carriers to kinetically modulate catalytic molecule-transforming processes.
(Invited) Probing Electrolysis Interfacial Chemistry: From Well-Defined to Complex Interfaces Under in Situ and Operando Conditions Using Ambient Pressure XPS
Authors: Crumlin Ethan J.
Published: August 2024

Interfaces play an essential role in nearly all aspects of life and are critical for electrochemistry. Electrochemical systems ranging from high-temperature solid oxide fuel cells (SOFC) to batteries to capacitors have a wide range of essential interfaces between solids, liquids, and gases, which play a pivotal role in storing, transferring, and converting energy. This talk will focus on using ambient pressure XPS (APXPS) to probe the solid/gas and solid/liquid electrochemical interface directly. APXPS is a photon-in/electron-out process that can provide both atomic concentration and chemical-specific information at pressures greater than 20 Torr. Using synchrotron X-rays at Lawrence Berkeley Nation Laboratory, the Advanced Light Source has several beamlines dedicated to APXPS endstations that are outfitted with various in situ/operando features such as heating to temperatures > 500 °C, pressures greater than 20 Torr to support solid/liquid experiments and electrical leads to support applying electrical potentials support the ability to collect XPS data of actual electrochemical devices while it's operating in near ambient pressures. This talk will introduce APXPS and provide several interface electrochemistry examples using operando APXPS, including the probing of a well-defined metal electrode to complex composite polymer/nanoparticle electrodes undergoing water-splitting or carbon dioxide reduction reactions. These studies provide new insight to guide the design and control of future electrochemical interfaces.
(Invited) Techno-Economics of Photoelectrochemical Water Splitting and Progress in Cost Reduction of High-Efficiency III-V Photoabsorbers
Authors: Deutsch Todd G , Wyatt Keenan , Young James L. , Steiner Myles A.
Published: August 2024

Photoelectrochemical (PEC) water splitting is a potentially promising route to direct solar-driven hydrogen production. Challenging targets for solar-to-hydrogen (STH) efficiency, durability, and semiconductor absorber costs must be realized for this approach to be economically competitive with other hydrogen production pathways. The first part of this talk will focus on the cost and performance metrics that go into techno-economic analysis and their status.

Research on PEC hydrogen production at the National Renewable Energy Laboratory (NREL) has focused on III-V semiconductor absorber materials because their tunable bandgaps, high photon conversion efficiencies, and ability to make multi-junction structures that have resulted in the highest STH efficiencies yet demonstrated. However, to achieve the U.S. DOE’s hydrogen production target of $2/kg, in addition to high STH efficiency, the semiconductor absorber synthesis cost must come down 1-2 orders of magnitude from the current metal organic vapor phase epitaxial route. Hydride vapor phase epitaxy (HVPE) is a technique that has the potential to lower tandem III-V synthesis costs. The second part of this talk will describe experimental photoelectrochemical characterizations of HVPE-grown GaInP/GaAs tandem photoelectrodes with 1.85/1.38 eV bandgaps. Their incident photon-to-current efficiency, photocurrent vs. circuit bias, and unbiased chronoamperometry will be presented and discussed. Upon illumination, the HVPE-grown structures were able to drive water electrolysis spontaneously (e.g., without an external bias) at STH efficiencies up to 10%. The durability of III-V photoelectrodes remains an unresolved challenge for cost effective hydrogen production via photoelectrolysis.
Revealing the Role of Redox Reaction Selectivity and Mass Transfer in Current–Voltage Predictions for Ensembles of Photocatalysts
Authors: Barrera Luisa , Esposito Daniel V. , Ardo Shane , Bala Chandran Rohini
Published: August 2024

Photocatalysts are conceptually simple reaction units where nanoscale semiconductors integrated with catalysts drive a pair of redox reactions on illumination. However, the proximity of reaction sites performing cathodic and anodic reactions poses dire challenges to realize large light-to-fuel conversion efficiencies. In this study, a powerful, yet straightforward, equivalent-circuit detail-balance modeling framework is developed and applied to evaluate the performance of photocatalytic systems featuring multiple light absorbers. Specifically, low bandgap iridium-doped strontium titanate is modeled a Z-scheme photocatalyst to effect desired hydrogen evolution and iron-based redox shuttle oxidation reactions. Our model has unique capabilities to simulate competing redox reactions and address mass-transfer limitations. In a significant departure from state-of-the-art circuit models, our study develops tools to perform load-line analyses by incorporating a net electrochemical load curve that includes both desired and competing redox reactions. Consequently, reaction selectivity is predicted from equivalent circuit models for photocatalytic and photoelectrochemical systems. Our investigation into ensembles comprised of multiple, semi-transparent light absorbers reveals their potential to outperform a single, optically thick light absorber, particularly when operated under mass-transfer-limited conditions. However, this outcome hinges on minimizing mass-transfer rates of select redox species to prevent undesired reactions of hydrogen oxidation and/or redox shuttle reduction. Our findings demonstrate that reaction selectivity can be achieved by tuning asymmetry in redox species mass-transfer even with perfectly symmetric electrocatalytic charge-transfer coefficients. The influences of various kinetic, mass-transfer, and thermodynamic parameters are explored to offer crucial insights to inform the next-generation of photocatalysts, selective coatings, and reactor designs.
Modeling Diurnal and Annual Ethylene Generation from Solar-Driven Electrochemical CO2 Reduction Devices
Authors: Yap Kyra M. K. , Wei William , Rodríguez Pabón Melanie , Bui Justin C. , Wei Lingze , Lee Sang-Won , Weber Adam Z. , Bell Alexis T. , Nielander Adam C. , Jaramillo Thomas F.
Published: August 2024

Integrated solar fuels devices for CO2 reduction (CO2R) are a promising technology class towards achieving net-negative carbon emissions. Designing integrated CO2R solar fuels devices requires careful co-design of electrochemical and photovoltaic components as well as consideration of the diurnal and seasonal effects of solar irradiance, temperature, and other meteorological factors expected for ‘on-sun’ deployment. Using a photovoltaic-electrochemical (PV-EC) platform, we developed a temperature and potential-dependent diurnal and annual model using experimental CO2R performance of Cu-based electrocatalysts, local meteorological data from the National Solar Radiation Database (NSRD), and modeled performance of commercial c-Si PVs. We simulated diurnal product outputs with and without the effects of ambient temperature to determine gaseous product temperature sensitivity. From these outputs, we observed seasonal variation in gaseous product generation, with up to two-fold increases in ethylene productivity between the Winter and Summer, analyzed the consequences of dynamic cloud coverage, and identified periods where device cooling/heating mechanisms could be implemented to maximize ethylene generation. Finally, we modeled the annual ethylene generation for a scaled 1 MW solar farm at three different locations (Beijing, CN; Sydney, AUS; Barstow, CA) to determine the consequences of local meteorological climates on PV-EC CO2R product output, recording a maximum ethylene output of 18.5 tonne/yr at Barstow. Overall, this model presents a critical tool for streamlining the translation of experimental solar-driven electrochemical research to real-world implementation.
(Invited) Innovating Sustainable, Cost-Effective, and Durable Redox Flow Battery Membranes
Authors: Yang Guang , Lehmann Michelle , Self Ethan , Saito Tomonori
Published: August 2024

In the quest to integrate renewable energy sources like solar and wind into the electric grid efficiently, the development of long-duration energy storage (LDES) systems is paramount. The U.S. Department of Energy's Long Duration Storage Shot initiative is at the forefront of this endeavor, aiming to reduce the costs of grid-scale energy storage by 90% for systems with over 10 hours of operation. A key player in this mission is the non-aqueous redox flow battery (RFB), known for its use of earth-abundant materials and potential to meet these cost-reduction goals. However, the commercial viability of RFBs hinges on the development of high-performance, cost-effective membranes, which are crucial for their functionality and affordability. These membranes' ionic conductivity is vital for the power density of RFBs, while their ion selectivity and solvent uptake greatly influence the batteries' cycle life.

Our team has made groundbreaking advancements in membrane technology for non-aqueous flow batteries. We've addressed the challenge of balancing ionic conductivity with mechanical strength in polymer electrolytes. Our findings reveal that enhanced solvent uptake while boosting membrane ionic conductivity, can compromise mechanical integrity. To counter this, we've employed two strategies: selective plasticization of the ion-conductive block in block copolymers and reinforcing the membrane's mechanical strength through hydrogen and ionic bonds with an inorganic scaffold. Significantly, we've also reduced the crossover of redox-active species in our membrane designs, notably decreasing polysulfide species crossover in a Na metal – polysulfide hybrid flow battery. This has led to improved capacity retention, Coulombic efficiency, and extended cycle life compared to traditional porous membranes.

Our latest innovations include the development of hydrocarbon single-ion conductors, demonstrating enhanced conductivity and stability. We've also introduced crosslinking chemistry to control solvent uptake more effectively, thus improving ionic conductivity while preserving mechanical strength. Lastly, our pioneering tape casting method for producing ceramic-polymer composite membranes represents a major leap in scalable membrane production, paving the way for the practical application of non-aqueous redox flow batteries in long-duration energy storage.

Acknowledgment

This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program in the Office of Electricity. We acknowledge Dr. Jagjit Nanda SLAC National Accelerator Laboratory for the fruitful discussions.
Development of Pentablock Copolymer Membranes for a Sodium Polysulfide Hybrid Redox Flow Battery
Authors: Lehmann Michelle , Self Ethan , Saito Tomonori , Yang Guang
Published: August 2024

Long duration energy storage devices, such as redox flow batteries (RFBs), are critical for enabling the widespread adoption of renewable energy sources such as wind and solar on the electric grid. Non-aqueous RFBs (NARFBs) have emerged as a possible alternative to aqueous RFBs (e.g., all-vanadium and Zn/Br systems), as they have the potential to use supporting electrolytes with wide operating voltage windows (>3 V) and a variety of redox couples. One NARFB of interest is a hybrid RFB that utilizes an alkali metal anode, such as sodium, and a polysulfide catholyte. However, the realization of a hybrid NARFB for long duration energy storage requires the development of new membranes with robust mechanical properties, good (electro)chemical stability, high ionic conductivity, and low polysulfide permeability. In this work, we have utilized a cation exchange pentablock copolymer membrane with sodium sulfonate and sodium trifluoromethanesulfonimide (TFSI) functionalities. We studied various crosslinking methods with the goal of reducing electrolyte uptake and polysulfide crossover of the membrane, while maintaining high ion transport. One lightly crosslinked membrane exhibits a 40% reduction in electrolyte uptake compared to the uncrosslinked membrane, but at the expense of a reduction in ionic conductivity from 2.5 x 10-4 S/cm to 4.2 x 10-5 S/cm at 20 °C. Our continued efforts in developing techniques to improve membrane properties will also be discussed.
(Invited) Unlocking Long-Duration Energy Storage with Unitized Reversible Fuel Cells
Authors: Komini Babu Siddharth , Arman Tanvir Alam , Li Yuanchao , Li Kui , Diaz-Abad Sergio , Murphy Eamonn , Fu Jintao , Liyanage Wipula Priya Rasika , Wang Xiaojing , Spendelow Jacob S.
Published: August 2024

As the proportion of energy supplied by renewable sources continually rises, the intermittent nature of these sources necessitates efficient energy storage to meet the demand of the grid. Hydrogen is a promising energy carrier for grid-scale storage due to its capacity for months-long storage without energy loss or self-discharge.(1) Reversible fuel cells generate power for the grid in fuel cell (FC) mode during periods when renewable power production is lower than demand, utilizing stored H2 generated by water electrolysis (WE) during periods when renewable power production exceeds demand from the grid. Unitized reversible fuel cells (URFCs) efficiently integrate WE and FC operation in a single electrochemical device, potentially reducing costs and providing higher energy density. In constant gas URFC operational configuration, both the oxygen evolution reaction (OER) for WE and the oxygen reduction reaction (ORR) for FC occur within the same electrode.(2) The contrasting electrode requirements for FC and WE have constrained the round-trip efficiency (RTE) of URFCs, highlighting the crucial need to improve RTE for greater competitiveness and widespread commercial adoption.

This presentation will discuss the results from development of novel bifunctional catalysts, electrode architectures, and porous transport layers (PTLs) aimed at enhancing efficiency and durability of URFCs. This talk will present the development of bifunctional catalysts and their supports to boost OER and ORR performance. Additionally, we will present insights into innovative electrode architecture designed for optimal utilization of the catalysts, thereby maximizing efficiency. The development of specialized PTLs featuring amphiphilic wettability and intricately engineered microporous layers will be presented emphasizing their role in increasing the performance and durability of URFCs.

Acknowledgement

This research is supported by the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) under project 20240061DR, and by the U.S. Department of Energy Hydrogen and Fuel Cell Technologies Office (DOE-HFTO) with support from technology manager Donna Ho.

References

Hydrogen Council, Hydrogen scaling up: a sustainable pathway for the global energy transition, in (2017).

S. Komini Babu et al., Advanced Energy Materials, 13, 2203952 (2023).
Exploring Cell Designs for Redox Flow Batteries with Flowable Suspension-Based Electrolytes
Authors: Majji Madhu V. , Brushett Fikile R.
Published: August 2024

Integrating flowable suspension-based electrolytes (FSEs) in redox flow batteries (RFBs) may expand the materials design space and unlock new pathways to cost-competitive stationary energy storage.1 In this approach, conductive particles are suspended in electrolyte solutions, forming electronically conductive networks that shuttle charge to and from the reaction volume, potentially replacing stationary porous electrode with RFB stacks. This configuration offers several potential benefits including access to extremely high surface areas for charge-transfer reactions, plating/stripping on a mobile solid phase, and the use of insoluble (or sparingly soluble) active species.2 However, FSEs often display shear-dependent properties that impact electrochemical and fluid dynamic performance and challenge compatibility with current electrochemical flow cells which are largely designed to support low-viscosity Newtonian fluids.1,3,4 As such, there is a need to consider alternate cell designs that may be better suited for FSEs.

We recently developed a continuum-based model and investigated how the performance of an RFB cell with an FSE changes as a function of material properties, cell dimensions, and operating conditions.4 In this presentation, we will use this modeling framework to explore three different cell configurations: fixed parallel plates, parallel plates with a linearly moving wall, and rotating concentric cylindrical surfaces. The distinct geometries and operational environments associated with each cell design result in different fluid flow and charge transport profiles which, in turn, alter the performance. We will compare and contrast fluid dynamic and electrochemical features of the three different configurations, with a focus on establishing operating envelopes and identifying which may best support FSEs. Ultimately, we aim to extend the design space considered for RFBs with FSEs as well as to better connect component material properties to cell engineering.

Acknowledgments

This work was supported by bridge funds from the Massachusetts Institute of Technology.

References

F. Savinell, and J. S. Wainright, The Electrochemical Society Interface 32, 61 (2023).

Parant et. al., Carbon, 119, pp.10-20 (2017).

C. Hoyt et. al., Chemical Engineering Science144 (2016): 288-297.

M. V. Majji et. al., Journal of The Electrochemical Society, 170(5), p.050532, (2023).
Developing Terpyridine-Based Metal Complexes for Non-Aqueous Redox Flow Batteries
Authors: Liu Bin , Zhao Tianshou , Jian Qinping
Published: August 2024

Redox flow batteries (RFBs) that utilize dissolved electroactive materials have shown great potential in storing intermittent solar and wind energy. The unique technological advantages of decoupled energy and power lead to high flexibility and scalability in RFB design, making it possible to satisfy a wide range of energy and power applications.[1,2] In traditional RFBs, inorganic transition-metal salts like all-vanadium, iron-chromium, and zinc-bromine RFBs are commonly used.[3,4] However, the narrow electrochemical stability window of water limits the attainable cell voltages in these aqueous systems. [5,6] To overcome these limitations, recent research has shifted towards non-aqueous RFBs (NARFBs) that use non-aqueous solvents, which can offer a wider electrochemical window up to 5 V.[7,8]

Here, we introduce our research efforts on the design and synthesis of a series of terpyridine-based complexes of the first-row transition metals Cr, Mn, Fe, and Co for non-aqueous redox flow batteries (NARFBs). Electrochemical studies reveal that these complexes can undergo multi-electron transfer redox reactions. Notably, the Mn and Fe-based complexes exhibit both low negative redox potentials and high positive redox potential, enabling them to serve as a bipolar electrolyte for symmetric RFBs with a cell voltage of over 2 V. The assembled iron-based symmetric NARFB demonstrates a high cell voltage of 2.3 V, columbic efficiency of 97%, energy efficiency as high as 88%, and stable charge-discharge capacity retention of 60% after 160 cycles, corresponding to 99.75 % capacity retention per cycle.

Figure 1
Supporting Electrolyte Design for a Stable Nonaqueous Redox Flow Battery Analyte
Authors: McIntosh Jory S. , Del Aguila Eric R. , Bhutto Samuel M. , Bao Neo Y. , Berben Louise A.
Published: August 2024

Non-aqueous redox flow batteries (NRFB) are of interest due to their enhanced potential for large energy densities compared to aqueous redox flow batteries. In this work, we compare the effects of several commonly used supporting electrolytes on the cycling stability of our previously reported active organic electrolyte. We report on the effects of various common cations and anions, and on the combined effects of various pairs. We find that non-coordinating anions and cations provide the most stable battery configurations. Cation and anions that will be discussed include 1-ethyl-3-methylimidazolium (EMIM) and 1-butyl-3-methylimidazolium (BMIM), tetrabutyl ammonium (Bu4N), and also trifluromethanesulfonate (OTf), tetraphenylborate (BF4) and triflimide (Tf2N). In most cases we see that stability correlates independently with the cation and the anion identity, but there are cases where the combination of certain cation and anion pairs provides an unexpected result. Our results describing battery performance and stability will include charging and discharging studies, measurements of electron transfer rate, diffusions coefficients, solution stability absent applied current, conductivity and viscosity measurements.
Physics-Based Continuum Modeling for an Aqueous Rechargeable Zn/MnO2 Battery
Authors: Bernard John C. , Takeuchi Kenneth J. , Takeuchi Esther S. , Marschilok Amy C. , West Alan C.
Published: August 2024

While Lithium-ion batteries dominate high-energy-density applications, their reliance on scarce and expensive materials poses a challenge for large-scale renewable energy storage. Aqueous Zinc/Manganese Oxide (Zn/MnO2) batteries, utilizing abundant and cost-effective materials, emerge as a viable alternative. However, the lack of understanding of their fundamental reaction mechanisms hampers their optimization and commercialization. In this study, we present a physics-based model to aid in elucidating the reaction mechanisms governing Zn/MnO2 batteries. When coupled with statistical parameter estimation, the model accurately replicates the discharge behavior across various C-rates and offers predictive insights into the underlying phenomena. Our findings inform the design of future targeted experiments and lay the groundwork for in-depth mechanistic studies. Moreover, the model serves as a tool for in-silico optimization, accelerating the path to commercial viability.
Potential-Dependent BDAC Adsorption on Zinc Enabling ‘Selective’ Suppression of Zinc Corrosion for Energy Storage Applications
Authors: Phung Theodore , Akolkar Rohan , Sinclair Nicholas Scott
Published: August 2024

Utility-scale zinc (Zn) batteries are a promising solution to address the problem of intermittency of renewable energy sources[1],[2]; however, Zn-metal anodes in these batteries suffer from capacity loss due to spontaneous corrosion of the Zn especially when high-surface area anode configurations are employed[3]. Additionally, Zn dendrites are known to form during battery charging which limits the cycle-life of these batteries. Electrolyte additives have been explored that prevent the aforementioned issues[4],[5], but these too come at a cost, i.e., surface-blocking additives polarize the electrode surface leading to loss in the voltaic and energy efficiencies of the battery. In this presentation, a novel electrolyte additive, benzyldimethylhexadecylammonium chloride (BDAC), will be presented for its ability to suppresses corrosion of Zn in a mildly acidic (pH = 3) electrolyte. An attribute of BDAC distinct from previously studied additives is that it ‘selectively’ suppresses corrosion when the Zn electrode is held near its mixed potential; however, during high-rate Zn deposition (charging) or stripping (discharging), BDAC is essentially deactivated and thus does not appreciably polarize the electrode surface. This selective corrosion suppression behavior is explored using slow-scan cyclic voltammetry, which reveals a hysteretic response. The response implies a current-dependent BDAC adsorption mechanism in which BDAC reaches higher surface coverages when the partial currents at the Zn surface are low (e.g., at or near the corrosion mixed potential), but BDAC coverage is reduced considerably when the Zn deposition-stripping rates are increased. Numerical simulations of the BDAC diffusion-adsorption process are used to corroborate this model. Ramifications of our approach to the selective suppression of Zn dendrites will also be discussed.

References:

[1] J. Kosowatz, “Energy Storage Smooths the Duck Curve,” Mech. Eng., vol. 140, no. 06, pp. 30–35, Jun. 2018, doi: 10.1115/1.2018-JUN-1.

[2] W. Cole, P. Denholm, V. Carag, and W. Frazier, “The peaking potential of long-duration energy storage in the United States power system,” J. Energy Storage, vol. 62, no. February, p. 106932, 2023, doi: 10.1016/j.est.2023.106932.

[3] C. J. Kellamis and J. S. Wainright, “A zinc–iodine hybrid flow battery with enhanced energy storage capacity,” J. Power Sources, vol. 589, no. July 2023, p. 233753, 2024, doi: 10.1016/j.jpowsour.2023.233753.

[4] J. L. Ortiz-Aparicio, Y. Meas, T. W. Chapman, G. Trejo, R. Ortega, and E. Chainet, “Electrodeposition of zinc in the presence of quaternary ammonium compounds from alkaline chloride bath,” J. Appl. Electrochem., vol. 45, no. 1, pp. 67–78, 2015, doi: 10.1007/s10800-014-0777-9.

[5] F. Mansfeld and S. Gilman, “The Effect of Lead Ions on the Dissolution and Deposition Characteristics of a Zinc Single Crystal in 6 N KOH,” J. Electrochem. Soc., vol. 117, no. 9, p. 1154, 1970, doi: 10.1149/1.2407584.
Tri-Electrode Structured Zinc-Air Batteries: A Leap in Energy Storage Efficiency and Stability
Authors: Lao-atiman Woranunt , Pornprasertsuk Rojana , Somwangthanaroj Anongnat , Kheawhom Soorathep
Published: August 2024

Rechargeable zinc-air batteries (ZABs) are gaining attention as a potent solution for large-scale energy storage, offering high capacity and an environmentally friendly profile. Utilizing zinc, an abundant and cost-effective alternative to lithium, ZABs capitalize on the plentiful oxygen in ambient air, presenting a more sustainable option than traditional lithium-ion batteries. In this work, we address the operational challenges of ZABs, primarily focusing on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) that occur during the discharge and charge cycles. ORR, a three-phase reaction, necessitates efficient water management and high-performance electrocatalysts, while OER is a two-phase reaction prone to creating oxygen bubbles that can damage the electrode structure. A critical issue in ZABs is the instability of ORR catalysts during the OER phase, and vice versa. To counter this, we propose a tri-electrode cell structure that separates the ORR and OER electrodes, allowing each to be optimized independently. This design enhances the stability and overall efficiency of the batteries. In our study, MnO2/C deposited on nickel foam was employed as the ORR electrode, and layered double hydroxides (LDHs) deposited directly on stainless steel mesh served as the OER electrode. A graphite electrode was used as the common negative electrode. Our proposed system, tested at 100 mAh/cm² and 25 mA/cm², demonstrated remarkable durability, sustaining at least 100 cycles with a Coulombic efficiency of 98% and a 60% roundtrip efficiency. These findings offer valuable insights into the future design of stable, high-efficiency rechargeable zinc-air batteries, marking a significant step forward in sustainable energy storage technology.
Energy Storage Capacity Utilization in Redox Flow Batteries
Authors: Bachman Ridge M. , Gamwo Isaac K. , Hall Derek M.
Published: August 2024

Redox flow batteries (RFBs) are predicted to be a major contributing technology in the need for four-to-ten-hour energy storage. Other energy storage technologies, such as lithium-ion batteries, provide well-documented performance indicators such as efficiency and especially energy storage capacity utilization. While redox flow batteries are compared similarly based on cost and round-trip efficiency, they often neglect a comparison of their operational energy storage capacity utilization. The breakdown of operational losses that represent the current state of operation for RFBs are pivotal to further compare the development of these technologies to the standard of other electrochemical storage devices. Quantifying the current state-of-the-art in relation to the theoretical potential of RFBs allows us to assess the extent of development required to enhance their effectiveness in contributing to future energy storage goals.

In this work, we set out to depict the operational energy storage density (W-h L-1) of various redox flow battery technologies based on consideration from experimental parameters and results from literature as key inputs. After reviewing five RFBs including the all-vanadium RFB, Hydrogen-Bromine RFB, All-Iron RFB, Zinc-Bromine RFB, and the Iron-Chromium RFB, results indicate that the VRFB is the most developed technology attaining around 60% of its theoretical energy storage density. While the Zinc-Bromine RFB has approximately the largest theoretical energy storage density (due to its high electroactive species concentration and standard potential difference), it is currently only able to operate at about a lowly 15% of it, dependent on its operational current density. We also assess the volumetric footprint for each RFB electrolyte system by considering a 6 MWh (6 MW, 1 hr) system. This assessment considers how large the electrolyte component of the RFB would be for operation. The Hydrogen-Bromine RFB would require electrolyte tanks to be more than 1600 m3 based on operational parameters, but if it were able to operate at 100% of its capability, the electrolyte tanks would shrink to be about 400 m3.
High-Rate and Durable Zinc-Based Flow Batteries for Large-Scale Energy Storage
Authors: Xu Zeyu , Li Jiayi , Wu Maochun
Published: August 2024

Large-scale energy storage is a key enabling technology for the widespread adoption of renewable energy such as wind and solar power. Among various technologies, zinc-based flow batteries stand out as one of the most promising candidates due to the high energy density, low cost, and use of earth-abundant active materials. However, the low operating current density and short cycle life resulting from notorious zinc dendrite formation, large internal resistance, and sluggish reaction kinetics pose a great challenge for their practical applications. Although great efforts have been made to address these issues, previous works mainly focused on one specific aspect, making it challenging to boost the overall performance of zinc-based flow batteries. In this presentation, a systematic study on the effects of key components on the electrochemical performance of zinc-bromine flow batteries will be presented. Our results show that all key components (electrodes, electrolytes, membranes, and flow fields) can exert a significant influence on the electrochemical performance. More impressively, a high areal capacity of >200 mAh/cm2 and an operating current density of as high as 400 mA/cm2 can be achieved by optimizing the design and operating parameters. Underlying mechanisms and perspectives for further improvement will be discussed during the presentation.
Aqueous Polysulfide-Based Redox Flow Battery with Soluble Molecular Catalysts
Authors: Lei Jiafeng , Lu Yi-Chun
Published: August 2024

Aqueous polysulfide-based redox flow batteries (RFBs) are promising for large-scale energy storage applications due to their low cost and high safety1. However, polysulfide negolyte suffers from poor kinetics, resulting in low operating current density and low energy efficiency2-5. Herein, we proposed a molecular catalyst strategy to transfer the sluggish electrochemical polysulfide reduction reaction to a fast chemical reaction via homogeneous catalysis. Inspired by the electron transport chain in the respiratory process, we selected riboflavin sodium phosphate (FMN-Na) as the molecular catalyst to transfer electrons from electrode to polysulfide with the disulfide bond cleavage6. The reaction rate (or turnover frequency) kobs is determined to be 33 s–1 at 1 M K2S4 solution, and this spontaneous chemical electron transfer process is verified by ultraviolet-visible light spectroscopy. In the polysulfide-ferrocyanide (S-Fe) RFB, the overpotential is dramatically decreased from over 800 mV to 241 mV at 30 mA cm–2 with the assistance of FMN-Na as the molecular catalysts. The catalyzed S-Fe RFB and polysulfide-iodide RFB showed stable operation for over 1,000 cycles at 40 mA cm–2. This work offers a simple but effective method to resolve the bottleneck for aqueous polysulfide-based RFBs, and such a homogeneous catalysis strategy may shed light on other flow battery systems with poor kinetics. We will combine operando spectroscopic techniques and theoretical calculation to discuss the possible reaction mechanism and intermediate.

Acknowledgment

This work is supported by two grants from the Research Grants Council (RGC) T23-713/22-R and RFS2223-4S03.

Reference

Y. Yao, J. Lei, Y. Shi, F. Ai and Y.-C. Lu, Nat. Energy, 2021, 6, 582-588.

Z. Li and Y.-C. Lu, Nat. Energy, 2021, 6, 517-528.

X. Wei, G.-G. Xia, B. Kirby, E. Thomsen, B. Li, Z. Nie, G. G. Graff, J. Liu, V. Sprenkle and W. Wang, J. Electrochem. Soc., 2015, 163, A5150.

Z. Li, M. S. Pan, L. Su, P.-C. Tsai, A. F. Badel, J. M. Valle, S. L. Eiler, K. Xiang, F. R. Brushett and Y.-M. Chiang, Joule, 2017, 1, 306-327.

J. Lei, Y. Yao, Y. Huang and Y.-C. Lu, ACS Energy Lett., 2023, 8, 429-435.

J. Lei, Y. Zhang, Y. Yao, Y. Shi, K. L. Leung, J. Fan and Y.-C. Lu, Nat. Energy, 2023, DOI: 10.1038/s41560-023-01370-0.
Sodium Polysulfides As Catholytes for Redox Flow Batteries
Authors: Zuleta Suarez Ernesto Camilo , Lehmann Michelle , Yang Guang , Self Ethan
Published: August 2024

Redox flow batteries based on sodium polysulfide (Na2Sx) show promise due to sodium's high solubility in organic solvents (e.g., diglyme. However, when x is lower than 5, sodium polysulfide exhibits low solubility (less than 0.1 molal), limiting the nominal capacity of this redox-active material. Sodium phosphorothioate complexes, Na2P2Sx, have been reported as an alternative to Na2Sx. Incorporating phosphorus into the polysulfide structure improves their solubility in organic solvents, specifically in diglyme.

This presentation will describe the synthesis and characterization of sodium phosphorothioate complexes (Na2P2Sx, where x = 6, 7, 8, and 9) for nonaqueous redox flow batteries. The structure of these materials is explored using 31P NMR and 23Na NMR spectroscopy, Raman spectroscopy, and X-ray diffraction analysis. Overall, 31P NMR results indicate that P5+ is tetrahedrally coordinated in all structures and that Na-P-S compounds have a common PS3- moiety. Ongoing efforts are aimed at providing more precise assignments to the 31P bands and correlating these findings with complementary structural information obtained from 23Na NMR and Raman spectroscopy.

Electrochemical properties of sodium polysulfide and sodium thiophosphate catholytes, specifically Na2S8 and Na2P2S8, were also compared using CV. The voltammogram of Na2S8 revealed two clear redox reactions in the 1.5-3 V range vs. Na/Na+ due to a multi-step electron transfer process involving the S2-/S0 redox center. In contrast, Na2P2S8 exhibited a larger peak separation (~2 V) and lower peak currents at a given scan rate, potentially indicating a significant activation barrier associated with the rearrangement of the thiophosphate’s polyanionic structure during reduction/oxidation. Despite the substantial voltage hysteresis, Na2P2S8 displayed stable cycling performance, with a slight increase in peak current after 100 cycles. This behavior is consistent with measurements on RFBs containing a Na2P2Sx catholyte, where an electrode activation process increased the cell’s reversible capacity, likely due to subtle changes in the electrode’s surface chemistry during repeated oxidation/reduction. Finally, preliminary flow cell measurements on Na2P2S7 catholyte show reversible voltage profiles after the formation step with deep discharge. Overall, this presentation demonstrates that Na-P-S catholytes represent a promising material for high energy, low-cost redox flow batteries.

Acknowledgements

This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program in the Office of Electricity.
Functionalisation of Carbon Catalyst Support By Plasma Treatment for PEMFC Cathode
Authors: Blanchard Pierre-Yves , Parnière Alice , Donzel Nicolas , Cavaliere Sara , Rozière Jacques , Jones Deborah J.
Published: August 2024

Proton exchange membrane fuel cell (PEMFC) is one promising electric device to replace the combustion engine using fossil fuel especially for heavy-duty transport. One of the main issue for the widespread of this technology on the European roads is the cost and degradation of their components over time. The sluggish reduction of dioxygen at the cathode require high amount of noble metal (i.e. platinum). Under PEMFC operating conditions, carbon as catalyst support is unstable.

This study presents a new approach to improve the stability of the cathode components (catalyst, carbon support and ionomer) thanks to the enhancement of the interaction between the three entities and to reduce carbon corrosion. Plasma treatment were performed on different carbon black sources (different surface area and porosity) to functionalize their surface by nitrogen function using different gas. The modified carbons were characterized by TEM, XPS, Raman spectroscopy, calorimetry, elemental analysis. The plasma treatments were reproducible and allow controlling the degree of functionalisation. The nitrogen doped carbons were catalysed by platinum nanoparticles. A better dispersion of the nanoparticles was observed by TEM showing the interest of the plasma treatment. Cyclic voltammetry were performed and a better catalytic activity toward the electrochemical reduction of O2 was observed.[1] Isothermal titration calorimetry experiments were carried out and show an improved interaction between the nitrogen functionalized carbon and the ionomer.

[1] A. Parnière, P.-Y. Blanchard, S. Cavaliere, N. Donzel, B. Prelot, J. Rozière, D.J. Jones, Nitrogen Plasma Modified Carbons for PEMFC with Increased Interaction with Catalyst and Ionomer, J. Electrochem. Soc.
169 (2022) 044502.

Figure 1
Operando Characterization of Water Flux across Hydroxide-Exchange Membranes
Authors: Weiss Catherine M. , Setzler Brian P , Weber Adam Z. , Yan Yushan
Published: August 2024

The water balance in operating hydroxide-exchange-membrane fuel cells (HEMFCs) is a key challenge for improved performance and durability. For every 4 electrons produced in an HEMFC, 4 water molecules are generated in the anode, 2 water molecules are consumed in the cathode. Water is also transported from cathode to anode along with the hydroxide due to electroosmosis. Consequently, there is a concentration gradient of water that transport water from anode to cathode. Ineffective water management could lead to cathode dry-out, where insufficient water in the cathode limits the rate of reaction or causes ionomer degradation through alkaline instability, or to anode flooding, where excess liquid water in the anode limits gas diffusion. To address these issues, it is critical to measure the transport of water across the hydroxide-exchange membrane during cell operation. We built a water-flux station to measure the water in and out of the anode and cathode during cell operation with different inlet relative humidities and back pressures. Here, the effect of the membrane thickness and the effect of stacking hydroxide-exchange membranes on the water transport across the hydroxide exchange membrane is studied. The stacking of hydroxide-exchange membranes creates an interfacial ohmic resistance between membranes, measured from the high frequency resistance, but not an interfacial water transport resistance. This study shows that the water transport across the hydroxide-exchange membrane is sufficient for water consumption in the cathode and is not significantly affected by the membrane thickness or stacking. However, the added ohmic resistance from the increased membrane thickness or stacking membranes significantly affects the performance.
Tuning the Bifunctional Properties of Cell Reversal-Tolerant Ir-Pt Electrocatalysts for HOR and Oer
Authors: Seidel Philipp , Ioselli Giulia , Blaseio Sonja , Yoon Sooyoung , Hasché Frédéric , Oezaslan Mehtap
Published: August 2024

Hydrogen starvation is still a big problem in PEM fuel cells [1]. In order to provide protons and electrons to the cathode during H2 starvation, the carbon oxidation reaction (COR) takes place at the anode [2]. To solve this issue, there are three main strategies: (i) utilization of corrosion resistant support materials, (ii) integration of extensive and complex system mitigation strategies and finally (iii) the addition of co-catalyst to promote the oxygen evolution reaction(OER) instead of COR. [3, 4]

In this work, platinum-iridium (PtIr) nanoparticles (NPs) have been designed as a novel bifunctional electrocatalysts to accelerate either the hydrogen oxidation reaction (HOR) or the OER depending on the reaction conditions. Our catalyst concept is the combination of both functionality (HOR and OER) in single Pt-Ir alloy nanoparticles (NPs) deposited on the same support material. The Pt-Ir NPs with Pt:Ir ratios of 1:1 and 3:1 were prepared by two different (colloidal and wet-impregnation) routes. Very interestingly, the oxidation states of platinum and iridium as well as the particle size strongly vary depending on the synthesis route. More precisely, the wet-impregnation enables preparing Pt-Ir NPs of 3 – 4 nm size and mainly in the metallic state, while strongly oxidized NPs with ~2 nm size are produced by colloidal route. Despite the different oxidation states and particle sizes, the Pt-Ir NPs show considerable activity for HOR and OER compared to pure commercial Pt/C and IrOx catalysts. Very interestingly, the bifunctionality of these Pt-Ir is highly reversible and is robust during accelerated stress tests. Operando Quick-X-ray Absorption Near Edge Structure (XANES) spectroscopy were performed to provide fundamental insights into the reversibility and catalytically active states of these bifunctional catalysts under the working conditions by jumping with the potential between HER and OER within few seconds. The combination of operando XANES, RDE and MEA data show that the bifunctional approach is a promising way to improve the cell reversal-tolerant properties of anode catalyst materials compared to the state-of-the-art Pt-IrOx catalyst materials.

References:

[1] P. Mandal et al, J. Power Sources 2018, 397, 397-404.

[2] C.Qin et al, Catalysts 2016, 6, 197.

[3] M. Tovini et al, J. The Electrochem. Soc. 2021, 168, 06452.

[4] R. Marić et al., J. The Electrochem. Soc. 2020, 124520.