Cell Technology Research Articles

Understanding Performance Limitation of Liquid Alkaline Water Electrolyzers

Green hydrogen production via water electrolysis powered by renewable energy is a critical technology in the pursuit of a net-zero emission economy1. Liquid alkaline water electrolyzers (LAWEs), being the most commercially mature electrolyzer technology, play a pivotal role in large-scale green hydrogen production2. The utilization of earth-abundant and cost-effective nickel and iron-based materials as cell components of LAWEs reduces capital cost of large-scale electrolyzer cells3. However, LAWEs suffer from low operational efficiency, primarily due to low intrinsic activity of unoptimized electrode materials, as well as high ohmic resistance introduced by separators and gas bubbles within thick electrodes. Herein, we used a lab-scale LAWE cell in combination with various electrode configurations to gain a deeper understanding of the limiting factors affecting conventional LAWE performance. Our results show that the electrochemical active surface area (ECSA), chemical compositions, and pore structure of the electrodes are key design parameters to achieve high efficiencies for advanced LAWEs. Besides, particular attention should be paid to the micro-gaps in between electrode and separator, which can be minimized through using electrodes with lower surface porosity and smaller pore size. Consequently, these enabled us to build LAWEs that are capable of sustaining 2 A cm-2 at 2.2 V and operating steadily at 1 A cm-2 for nearly 600 h with negligible performance decay. These findings establish essential criteria for selecting electrodes to achieve high-performance in LAWE and, in turn, expedite the adoption of LAWE technology in green hydrogen production and the transition towards a low-carbon economy. Acknowledgement The authors acknowledge the Department of Energy-Office of Energy Efficiency and Renewable Energy-Hydrogen and Fuel Cell Technologies Office (DOE-EERE-HFTO) and the H2 from Next-generation Electrolyzers of Water (H2NEW) consortium for funding under Contact Number DE-AC02-05CH11231.

Physics-Based Impedance Model for Understanding Proton Transport in PEM Fuel Cells

The electrochemical impedance spectroscopy (EIS) diagnostics using H2/N2 operation condition developed for fuel cell is useful tools to estimate the catalyst layer (CL) proton resistance. Currently, the resistance is estimated by fitting the measured EIS data to an equivalent circuit model. However, it is challenging to correctly determine the transmission line circuit and accurately estimate the proton resistance [1]. Moreover, the capacitive and resistance elements in the transmission line model are assumed similar throughout the CL even if there is nonhomogeneous distribution of ionomer. To understand the EIS response in CL, we present a physics-based model. Utilizing the model, we are able to investigate the H2/N2 cell impedance response under various operating conditions. The continuum scale model will be combined with agglomerate scale model to provide a detail study of the electrode parameters like ionomer loading and ionomer coverage The hybrid theoretical model allows us to study the effect of nonhomogeneous CL and its corresponding EIS response. Acknowledgement This research is supported by U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office, through the Million Mile Fuel Cell Truck Consortium (M2FCT).

Modeling of Electric Double Layer to Analyze Reaction Kinetics

Electric double layers (EDLs) play a fundamental role in various electrochemical processes such as colloid dispersion, surface charging, and charge-transfer reactions. Increasingly, the role of EDLs on reaction kinetics is being studied (1). Despite the extensive history of EDL modeling, there remain challenges in accurate prediction of its structure. The characteristic length of EDL (nanometer scale) exceeds the grasp of typical ab-initio molecular-dynamic simulations in order to capture a whole picture of the statistical equilibrium. While continuum models offer a means to estimate the thermodynamic equilibrium of EDLs with substantially lower computational cost than molecular dynamics, state–of-the-art continuum models require parameter fitting(2) due to the lack of appropriate expressions for microscopic interactions.Herein, we propose a predictive multiscale continuum model of EDL that eliminates the empirical fitting and relies more on physical relations. This model computes the distribution of the electrostatic potential, electron density, and species’ concentrations by minimizing the total grand potential of the system. The grand potential is calculated from entropic energy, electrostatic energy, electron energy, solute-solute interactions, and electrode-solute interactions. These energy expressions include not only the terms from previous work(2), but also the microscopic interactions that are newly introduced in this work: polarization of hydration shells, electrostatic interaction in parallel plane toward the electrode, and ion-size-dependent entropy. The parameters that identify the electrode and electrolyte materials are obtained from independent experiments such as vacuum work function, bulk modulus, X-ray diffraction, and concentration-dependent dielectric constant. The developed model reproduces the trends in the experimental differential capacitance with multiple electrode and electrolyte materials (Ag (111)-NaF, Ag (111)-NaClO4, and Hg-NaF), which verifies the accuracy and predictiveness of the model in a system without significant specific electrode-electrolyte interactions. The difference in the capacitance between mercury and silver electrode was attributed to the difference in the electron stability in the metal that is parameterized from the material’s bulk modulus. Finally, extension of the model to systems with specific electrode-electrolyte interactions (e.g., Pt (111)-NaClO4) and the analysis of reaction kinetics will be introduced. Overall, the model framework and findings will provide insights into the EDL structures and guidance on how to tailor electrode-electrolyte interface for improved reaction kinetics. Acknowledgements: This work was partially supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos, under contract number DE-AC02- 05CH11231, as well as by a CRADA with Toyota Central R&D Labs., Inc. and by the Center for Ionomer-based Water Electrolysis (CIWE), a DOE Energy Earthshot Research Center. Reference: S. J. Shin, D. H. Kim, G. Bae, S. Ringe, H. Choi, H. K. Lim, C. H. Choi and H. Kim, Nat Commun, 13, 174 (2022).J. Huang, J Chem Theory Comput, 19, 1003 (2023).

Accelerated Discovery of Multi-Metallic Nanostructured Catalysts for Anion Exchange Membrane Water Electrolyzers: Oxygen Evolution Reaction

The current reliance on platinum group metals (PGMs) as electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) water electrolyzers, the current industry standard, presents a significant barrier to the widespread adoption of hydrogen as a clean energy carrier. The scarcity and high cost of PGMs necessitate the development of alternative materials and technologies that offer comparable performance at a reduced cost. In this context, anion exchange membrane (AEM) water electrolyzers have emerged as a promising alternative.This presentation addresses this imperative by focusing on the design and synthesis of nanostructured mesoporous multi-metallic catalysts for AEM water electrolyzers, leveraging earth-abundant materials as alternatives to the rare and expensive PGMs currently employed in PEM water electrolyzers. Transition metal oxides, sulfides, and phosphides are promising candidates to replace PGMs, given their abundance, low cost, and tunable catalytic properties conducive to high OER activity. The OER activity and durability of newly developed multi-metallic transition metal catalysts in an alkaline environment will be discussed in this presentation.Preliminary results demonstrate that the developed catalysts exhibit high OER activity, achieving a potential of <1.5 V versus RHE at a current density of 10 mA cm⁻² in 1.0 M KOH. Notably, this surpasses the performance of commercial OER catalysts in alkaline environments. Furthermore, the catalyst exhibits superior durability, with < 0.5 mV/h potential loss over 100 h durability test at 10 mA cm⁻² in 1.0 M KOH.AcknowledgmentsThis work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). Argonne is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, under Contract DE-AC-02-06CH11357 .

(Invited) Department of Energy, Energy Efficiency and Renewable Energy - Activity Updates in Reversible Fuel Cells and High Temperature Electrolysis

The Hydrogen and Fuel Cell Technologies Office (HFTO) within the U.S. Department of Energy’s (DOE) Office of Energy Efficiency and Renewable Energy (EERE) supports a range of analysis, research, development, and demonstration efforts that fall under the areas of high temperature electrolysis (HTE) and reversible fuel cells (RFCs). These efforts range from earlier stage R&D on cell components to demonstrating early system technology. Particularly when used in conjunction with high temperature process heat, HTE technology shows promise for highly efficient, cost effective, sustainable hydrogen production at high volumes. This potential has led to its inclusion in multiple HFTO initiatives, including two national lab-led consortia separately focused on next generation materials and overcoming technical barriers to manufacturing durable, affordable, and efficient HTE systems. These consortia objectives, efforts, scopes, and developments are discussed in the context of HTE and recent DOE initiatives and announcements, including the Hydrogen Energy Earthshot, Long Duration Energy Storage Earthshot, and Clean Fuels and Products Earthshot.

Nanoparticles for Active and Sustainable Fuel Cell Cathodes

Depletion of fossil fuels and environmental pollution raised interest in new technologies for sustainable energy production, conversion, and storage, among which fuel cell technology is greatly studied, in both academia and industry. Proton exchange membrane fuel cells (PEMFCs) are reputed energy devices, due to their high conversion efficiency and low environmental pollution.1 Nowadays, Pt-based catalysts exhibit the best electrocatalytic activity towards oxygen reduction reaction (ORR), but enhancing their catalytic efficiency and reducing costs are essential for commercializing fuel cell technology.2 Our interest relies with the development of Pt-based nanoalloys2,4 via solution organometallic chemistry approach.3 This approach allows control over the composition, structure, and morphology of metal nanoparticles, and could lead to increased catalytic activity and long-term stability by revealing more active sites of the catalyst. Additionally, the ability to alloy with a range of metals for producing bimetallic compounds is one of the key advantages of this approach.In this communication, the synthesis of Pt-based nanoparticles and their characterization by state-of-the-art techniques such as ICP, EA, IR, TEM and HR-TEM will be described. The influence of the Pt complexes used as precursors and of the reaction conditions on the morphology of the Pt nanoparticles will be shown. The obtained nanostructures offer interesting starting materials to incorporate other metals, such as transition or rare earth metals, in order to have nanoalloys and study their performance in ORR in comparison to pure Pt catalysts.

Achieving High Performance with High Oxygen Permeability Ionomer (HOPI) in Heavy Duty Fuel Cell MEAs

Heavy-duty PEM fuel cells are expected to last 25,000-30,000 hours in the field. Therefore, materials, components, and interfaces used in these systems must be highly resistant to severe mechanical and chemical stress. Novel, highly active stable Pt and ordered PtCo intermetallic nanoparticles with well-controlled particle size and composition have been synthesized on a highly efficient PGM-free single metal active site rich carbon, to maximize their synergistic effects for enhanced performance and durability. Integrating these catalysts integrated with high O2 permeability ionomer (HOPI) in membrane electrode assemblies (MEAs) improved their fuel cell performance and durability, allowing the MEAs to achieve >1.2 A/cm2 at 0.7 V after 150k square wave accelerated stress test (AST) cycles, with a performance loss < 40 mV after 150K AST cycles.In a PEM fuel cell, the catalyst ink formulation and mixing processes control catalyst layer coating quality, electrode morphology, and the resulting fuel cell performance and durability. Catalyst ink properties are a result of complex solvent-catalyst-ionomer interactions that depend on the mixing method employed. Here, we compare the performance and durability of electrodes made from ball milled inks for Mayer rod coating before and after the catalyst scale up. Ink rheology and catalyst particle size are used to correlate ink properties to electrode morphology and structure and ensure consistency from batch to batch, and from small lab scale to subsequent scale-up. We evaluate and discuss the challenges that arise when coating the more viscous inks on decals, where the HOPI creates many bubbles in the ink. We also present the challenges of hot-pressing inks that contain HOPI, and how employing a Nafion overspray made with different solvents (isopropanol vs. ethanol) can improve hot-pressing. We investigate the how ionomer to carbon ratio affects hot pressing with HOPI and crack formation in the electrode via scanning electron microscopy (SEM).This work provides a comprehensive understanding of interactions between Pt, PtCo, carbon, ionomer, membrane, and GDLs and their impact on electrode structure, fuel cell performance and durability, as well as considerations for scale up to a R2R fabrication process. The attained information will be used to improve fuel cell electrode design, fabrication and scale-up.Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-FOA-0002360 (Phase I) and DE-SC0021671 (Phase II). Figure 1

Understanding the Impact of Conditioning Protocols for Water Electrolyzers on Durability

The global push towards climate neutrality has intensified research efforts on green hydrogen production technologies. Among them, proton exchange water electrolysis (PEMWE) stands out as a highly efficient technology for producing green hydrogen using renewable energies. Nevertheless, a significant reduction in the cost of PEMWE while maintaining its durability over its operational periods is imperative. The DOE’s Hydrogen Earthshot target aims to achieve $1 per 1kg of H2 production within the decade. Reducing the amount of expensive iridium catalysts also reduces the durability of PEMWE. Hence, understanding the degradation mechanisms of low Ir loading PEMWE holds utmost importance. One key step in the evaluation of PEMWE is the break-in or conditioning step. Ensuring optimal conditioning is crucial to guarantee the peak performance of membrane electrode assembly (MEA) before assessing the durability of the catalyst thereby ensuring representative and reproducible results.This research aims to comprehensively evaluate various conditioning protocols for PEMWE and their impact on durability. Utilizing a combination of electrochemical, electron, and X-ray characterization techniques. Accelerated stress tests (AST) will be conducted after each conditioning protocol to evaluate the degradation rate of the catalyst. Ex-situ characterization of the MEA post-conditioning as well as post-AST offers a comprehensive understanding of how the catalyst’s initial state, such as the iridium oxidation state, following the conditioning step directly influences the durability. The goal is to develop an optimal conditioning protocol for PEMWE, that considers the performance and durability challenges associated with low catalyst loading. Acknowledgment This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium with support from Dave Peterson and McKenzie Hubert.

Durability Assessment of Roll-to-Roll Coated PEM Water Electrolysis Anodes

Widespread adoption of green hydrogen relies on the high-throughput production of key electrolyzer components in a manner yielding acceptable stack manufacturing costs. Roll-to-roll liquid coating methods, such as slot die and gravure coating, are particularly relevant means to produce key components (e.g., membranes and electrodes) at high throughput. In the case of proton exchange membrane water electrolysis (PEMWE), thrifting of expensive iridium-based catalysts poses additional challenges to the implementation of such high-throughput coating methods for iridium-based anode manufacture.Herein, we investigate key challenges around roll-to-roll manufacture of low-loaded (<0.2 mgIr/cm2) iridium-based electrodes for PEMWE. In particular, we highlight fundamental limitations in coating the thin layers required to manufacture low-loaded electrodes, for which the improper choice of coating conditions may lead to macro- and micro-scale heterogeneity. By addressing causes of this heterogeneity, homogeneous slot-die coated iridium oxide anodes of varying iridium loading are produced on decal substrates. Catalyst coated membranes (CCMs) are subsequently produced from these anodes via hot-pressed decal transfer, and 1,000 hour constant current tests are conducted with intermediate diagnostics (polarization curves and impedance spectroscopy). Key effects of loading and homogeneity on electrode durability are highlighted, and future directions are discussed.This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and Advanced Manufacturing Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.

Zero-Gap Liquid Alkaline Water Electrolyzers: Challenges in Benchmarking and Directions for Development

Green hydrogen is expected to play a central role in the replacement of fossil energy sources, especially in difficult to decarbonize sectors of the economy. Currently, low temperature methods of electrolysis are the only commercially realized sources of green hydrogen. Liquid alkaline water electrolysis (LAWE) is the most widely utilized method of electrolysis, with a 100-year history of use. Given this lengthy history one could be forgiven for assuming that there is little development left. However, standard LAWE materials and cell designs do not achieve the production, efficiencies, and durability necessary to meet the anticipated demand for green hydrogen.To spur development in this neglected area of hydrogen production, the US Department of Energy, Hydrogen and Fuel Cell Technology Office (DOE-HFTO) added LAWE to its Hydrogen from Next-generation Electrolyzers of Water (H2NEW) Consortium. One of the main tasks for this part of the consortium is to benchmark and validate materials and cell components for LAWE. This includes the development of lab-scale cell hardware and test protocols that can be widely disseminated in the research community. The result of this work will be the development of the methods and materials necessary to achieve robust and reproducible datasets for the improvement of catalysts, separators, cell architecture and operation.We will present the status of the benchmarking effort. This will include a description and explanation of a lab-scale LAWE test station, electrolyte handling, and hydrogen safety. The requirements for the safe operation of an electolyzer using high concentration alkaline electrolytes differs significantly from more typical proton exchange, or anion exchange membrane systems. We will also discuss common sources of error that can significantly influence cell performance and result in poor reproducibility. Acknowledgement:This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.

PGM-Free Oxygen Evolution Reaction Catalyst for PEM Water Electrolysis – a Mechanistic Study on Activity and Durability for Practical Applications

Low temperature proton exchange membrane water electrolyzer (PEMWE) represents a critical technology for green hydrogen production. It offers the advantages of significantly higher current density and higher H2 purity, rendering it a preferred technology when high energy efficiency and low footprint are essential. Working in the oxidative and acidic environment under high polarization voltage, however, adds substantial demand to the electrode catalyst and the support. This is particularly the case at anode where the oxygen evolution reaction (OER) takes place. At present, the platinum group metal (PGM) materials such as Ir black or Ir oxide are catalysts of choice. Their high cost and limited reserve add a significant cost barrier to PEM electrolyzer, which contributes to the overall expense of hydrogen production next only to the cost of electricity. Replacing Ir with earth-abundant transition metal oxides could help to reduce the electrolyzer system cost.For PEMWE application, a PGM-free anodic catalyst must be highly active to match the performance of Ir. Furthermore, it must be stable against oxidative acid corrosion. At Argonne National Laboratory, we recently developed a new PGM-free OER of a nanofibrous cobalt spinel catalyst co-doped with lanthanum and manganese (LMCF). [1] The catalyst was synthesized from the precursor of cobalt zeolitic methyl-imidazolate framework (Co-ZIF) doped with manganese and lanthanum. The Co-ZIF was mixed with a polymer solution and electrospun into nanofiber before being converted to fibrous cobalt spinel under low temperature oxidation to remove all the organics and carbon. The new PGM-free catalyst demonstrated a low overpotential of 353 mV (RHE) at 10 mA/cm2 and a low OER degradation over 360 hours in acidic electrolyte. A PEMWE containing this catalyst at its anode at ~2.0 mg/cm2 demonstrated a current density of 2000 mA/cm2 at 2.47 volts (Nafion® 115 membrane) or 4000 mA/cm2 at 3.00 volt (Nafion® 212 membrane). The membrane electrode was also subjected to accelerated-stress-test (AST) in both voltage cycling and galvanostatic run at different current densities. Low degradation rates under both ASTs were observed.In addition to catalyst design and synthesis, we also conducted extensive structural characterizations, stability measurement, as well as computational modeling. Our in situ study found that the OER process involves significant lattice oxygen movement, leading to lowering instead of raising the cobalt oxidation state during the electrolysis. The measurement of the stability number, combined with computational Pourbaix diagram, elucidated the importance of the operating potential in reducing catalyst dissolution. These findings offer in-depth understanding and direction of future development for PGM-free OER catalyst in PEM water electrolyzer. Acknowledgement: This work is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewal Energy, Hydrogen and Fuel Cell Technologies Office, and by Laboratory Directed Research and Development funding of Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DEAC02-06CH11357. Work performed at the Center for Nanoscale Materials and Advanced Photon Source, both U.S. Department of Energy Office of Science User Facilities, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.[1] “La- and Mn-doped cobalt spinel oxygen evolution catalyst for proton exchange membrane electrolysis” Lina Chong, Guoping Gao, Jianguo Wen, Haixia Li, Haiping Xu, Zach Green, Joshua D. Sugar, A. Jeremy Kropf, Wenqian Xu, Xiao-Min Lin, Hui Xu, Lin-Wang Wang, Di-Jia Liu, Science 380, 609–616 (2023)

Advancements in Additive Manufacturing of Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs), also known as proton conducting solid oxide fuel cells, are a promising low-temperature (400-600oC) fuel cell technology. Compared to conventional oxygen-ion conducting ceramic materials, proton conducting ceramic electrolyte materials have lower activation energy (< 50 eV), which can enhance fuel cell efficiency and power output. Additive manufacturing has the potential to revolutionize PCFC manufacturing, as it enables fabrication of both dense and porous structures with desirable mechanical and electrochemical properties. In this study, we employed extrusion-based 3D printing to fabricate PCFCs using BaZr0.3Ce0.5Y0.15O3-δ and BaZr0.4Ce0.4Y0.1Yb0.1O3-δ as electrolytes, NiO as anode, and BaCo0.4Fe0.4Zr0.1Y0.1O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ as cathode. For comparison, we also printed oxide conducting ceramic fuel cells using gadolinium-doped-ceria (GDC ) as electrolyte. We investigated the printable pastes' rheological properties using dynamic light scattering, viscometer, tensiometry, differential scanning calorimetry, and thermal gravimetric analysis. We also characterized the cells using current-voltage measurements, electrochemical impedance spectroscopy, and various spectroscopic and microscopic techniques (HR-TEM-EELS, SEM-EDX) to understand the underlying mechanisms. Finally, we conducted a systematic study to optimize the sintering temperature for optimal fuel cell performance and investigate degradation mechanisms to improve stability. The best printed fuel cells produced 926 mW/cm2 with 3-layer structure and 426 mW/cm2 with 1-layer structure at 550oC.

Exploring Low Temperature Proton Exchange Membrane Water Electrolysis Anode Catalyst Degradation Under Cathode Backpressure Conditions

Hydrogen is expected to play an important role in the decarbonization of the future energy landscape by integrating renewable, nuclear, and fossil fuels and using excess power from the grid to produce H2 that can then be stored and used for a variety of applications ranging from ammonia and steel production, stationary power, buildings, and transportation.1 In order to achieve low-cost hydrogen production that is competitive with steam methane reformation (SMR), it is necessary to decrease the capital cost and this can be done by leveraging variable renewable energy (VRE) as an electricity feedstock for LTE.2 However, cost, and durability are still current challenges in state-of-the art water electrolysis systems. More research is needed to better understand the effects of dynamic operation on electrolyzer degradation. Understanding the degradation mechanisms governing intermittent electrolysis operation can enable future improvements related to component design and system operation.In recent years, electrolyzer anode degradation has been investigated during continual intermittent operation at the single cell level. Square-wave potential cycling demonstrated higher anode degradation compared to the triangle-wave cycling over the same 525 hour test (21.9 d).3 Electrolyzers operating at differential pressures and producing electrochemically compressed hydrogen could decrease the hydrogen production cost by eliminating the need for equipment related to mechanical compression.4 This work investigates the dynamics of low-temperature proton exchange membrane (PEM) electrolyzers, with a specific focus on anode catalyst layer degradation from redox transition when subjected to hydrogen crossover from cathode backpressure conditions. While cathode backpressure and operation requirements are well understood from an industry perspective, its impact on degradation mechanisms and loss rates has been relatively underexplored when low-temperature electrolysis is focused on cost reduction and variable load.In this study, hydrogen cross-over rates were varied by cathode backpressure conditions (ambient to 30 Bar) and were compared to elucidate the impact hydrogen has on anode catalyst layer degradation. The durability test duration varied from 168 – 500+ hrs. Hydrogen cross-over rates were found to correlate to cell potential during operational shutdowns and loss rates during load cycling. Electrochemical impedance spectroscopy further demonstrates higher degrees of kinetic loss and the immergence of additional loss mechanisms. The findings presented in this research contribute to the fundamental understanding of low-temperature PEM electrolysis dynamics under cathode backpressure conditions. The implications of this research offer practical insights for the design and operation of efficient and durable electrolysis systems crucial for the advancement of sustainable hydrogen production technologies.(1) H2@Scale. Hydrogen and Fuel Cell Technologies Office. https://www.energy.gov/eere/fuelcells/h2scale.(2) Mark, R.; Jadun, P.; Gilroy, N.; Connelly, E.; Boardman, R.; Simon, A. J.; Elgowainy, A.; Zuboy, J. The Technical and Economic Potential of the H2@Scale Concept within the United States; NREL/TP-6A20-77610; National Renewable Energy Laboratory: Golden, CO, 2020.(3) Alia, S. M.; Reeves, K. S.; Yu, H.; Park, J.; Kariuki, N.; Kropf, A. J.; Myers, D. J.; Cullen, D. A. Electrolyzer Performance Loss from Accelerated Stress Tests and Corresponding Changes to Catalyst Layers and Interfaces. Journal of The Electrochemical Society 2022, 169 (5), 054517. https://doi.org/10.1149/1945-7111/ac697e.(4) Ragnhild Hancke, Thomas Holm, and Øystein Ulleberg, “The Case for High-Pressure PEM Water Electrolysis,” Energy Conversion and Management 261 (2022): 115642, https://doi.org/10.1016/j.enconman.2022.115642. Figure 1

Direct Hydroquinone Fuel Cells

The Increasing interest and need to shift to sustainable energy give rise to the utilization of fuel cell technologies in various applications. The challenging task of hydrogen storage and transport led to the development of liquid hydrogen carriers (LHC) as fuels for direct LHC fuel cells, such as methanol in direct methanol fuel cells (DMFC). Although simpler to handle, most direct LHC fuel cells suffer from durability and price issues, derived from high catalysts’ loadings and by-products of the oxidation reaction of the fuel. Herein, we report on the development of direct hydroquinone fuel cells (DQFC) based on anthraquinone-2,7-disulfonic acid (AQDS) as an LHC. We have shown that DQFC can operate with continues flow of quinone as a hydrogen carrier, outperforming the incumbent state-of-the-art DMFC by a factor of three in peak power density, while completely removing the need for any catalyst at the anode. In addition, we demonstrate that the quinone can be charged with protons in the same system, making it a reversible fuel cell system. We optimized the operating conditions and will discuss the governing conditions to reach best performance.

Novel Electrocatalytic Hydrogenation Using a Solid Polymer Electrolyte (SPE) Reactor

Organic electrosynthetic reactions, which are driven by electricity, can generally be carried out under mild conditions (room temperature and ambient pressure). In addition, they do not require any hazardous reagents and produce less waste than other conventional chemical syntheses. Therefore, electrosynthesis is known to be a mild and clean method for organic synthesis and there has recently been renewed interest in its development. However, electrosynthesis also has some disadvantages. Ordinary chemical reactions are homogeneous, while the reaction field of electrolysis is a heterogeneous interface, therefore electrosynthesis has a productive drawback. In addition, a large amount of supporting electrolyte is usually required. Therefore, the availability of solvents is limited by the necessity for dissolution of a supporting electrolyte. The presence of the supporting electrolyte might also cause separation problems in the reaction workup. Moreover, in an ordinary electrolysis system, solution resistance is generated between the working and counter electrodes, resulting in a decrease in energy efficiency. To overcome these problems, we focused on a solid polymer electrolyte (SPE) reactor which was originally developed for fuel cell technologies and demonstrated various electrocatalytic hydrogenations in a SPE reactor (Figure 1) [1-5].As shown in Figure 1, a SPE membrane such as a proton exchange membrane (PEM) is integrated into the central part of the reactor, and is sandwiched between a pair of catalyst layers on the anode and cathode sides. For this reason, the substrate solution does not require a supporting electrolyte and the cell resistance can be minimized. The anode and cathode have highly porous 3D structures in order to conduct an efficient electrochemical reaction. Moreover, the reaction can be carried out in a flow operation. Thus, the SPE reactor system possesses many characteristics designed to overcome the disadvantages of conventional electrosynthetic processes.In a series of studies we have conducted, in this presentation, we will discuss two topics such as diastereoselective reduction of cyclic ketones and electrocatalytic hydrogenation of pyridines.The authors gratefully acknowledged support by JST CREST Grant No. 18070940, Japan.[1] A. Fukazawa, M. Atobe, et al. ACS Susutain. Chem. Eng. 2019, 7, 11050.[2] S. Nogami, M. Atobe, et al. J. Electrochem. Soc. 2020, 167, 155506.[3] A. Fukazawa, M. Atobe, et al. Org. Biomol. Chem. 2021, 19,7363.[4] S. Nogami, M. Atobe, et al. ACS Catalysis, 2022, 12, 5430.[5] Y. Shimizu, M. Atobe, et al. ACS Energy Lett., 2023, 8, 1010. Figure 1

Surface Decorated SnOx modifiers Boost Oxygen Reduction and Hydrogen Evolution Reaction Performance of Pt Nanorods

The development of efficient, durable and commercially competitive catalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is undoubtedly a challenging task for fuel cell technology. In this context, for the first time, we developed a bi-metallic heterogeneous nanocatalyst (NC) comprising high-density atomic SnOx-clusters anchored Pt-nanorods (denoted as SnOx@Pt) via formic acid reduction method (FAM) as a bifunctional catalyst for ORR and HER (Fig.1). The as-prepared SnOx@Pt nanorods exhibit unprecedented high mass activity (MA) of 160 mAmg-1 (Pt) at 0.85 V vs RHE in acidic ORR (0.5M HClO4), which outperformed the commercial J.M.-Pt/C (20 wt.% Pt) catalyst by 1.4 folds. Of special relevance, SnOx@Pt nanorods exhibit remarkable durability when operated up to 5000 cycles in accelerated durability test (ADT) and retain their 87% MA as that of the initial condition. Additionally, as-prepared SnOx@Pt nanorods demonstrated a notable lower overpotential (η) of 48 mV at the cathodic current density of 10 mAcm-2 and the Tafel slope of 33 mVdec -1 in acidic HER (0.5M H2SO4). These overpotential and Tafel slope values are significantly lower compared to commercial J.M.-Pt/C catalyst (η = 60 mV and Tafel slope = 38 mVdec-1). Moreover, such material retained its 100% performance in the chronoamperometric (CA) stability test up to 6h, which shows its capability in potential commercialization. The cross-referencing results of physical inspections and electrochemical analysis reveal that such a high-performance of SnOx@Pt nanorods is attributed to the local synergetic collaboration between SnOx modifiers and neighboring Pt active sites. More specifically, the SnOx modifiers promote the H-OH bond cleavage during HER, while simultaneously promotes the desorption of oxygen species on Pt surface in ORR, which later triggers the reduction reaction performances. Meanwhile, SnOx provides a shielding effect to Pt during harsh reduction conditions and thus high stability of SnOx@Pt nanorods is achieved. Of utmost importance, this study not only unveils a novel geometric design but also provides the mechanistic understanding behind the superior electrochemical properties of the unique SnOx modifiers in ORR and HER. Hence, we envision that the proposed rationale will be a forwarding step for the development of high-performance low Pt content catalysts for fuel cells with superior electrochemical properties far beyond the physical nature of transition elements. Keywords: Oxygen reduction reaction, hydrogen evolution reaction, fuel cells, nanocatalysts, mass activity

How Mechanical Challenges Affect the Performance of Industrial Scale Carbon Dioxide Electrolyzer Cells?

One of the most important challenge of humanity in the mid-21st century is to maintain economic growth in an environmentally sustainable way. The European Green Deal addresses this issue, and it aims at making Europe climate neutral by 2050. To reach this aim, a promising technology is to convert a greenhouse gas, carbon dioxide into valuable chemicals (produce e.g., energy carriers, fine chemicals, pharmaceuticals) in an environmentally and economically sustainable manner, such as the utilization of renewable energy sources.The direct electrochemical reduction of carbon dioxide into carbon-monoxide (a high-value product which can be readily used in the chemical value chain) is a promising waste-to-wealth approach among the developed technologies and it can be easily coupled with carbon-free electricity sources to make the process completely sustainable. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance, as well as finding technological solutions that enable scale-up to reach industrially relevant dimensions.Zero-gap electrolyzer cell technology operates with high reaction rates and good efficiencies under ambient and near ambient conditions. In addition, its operation is simpler compared to other types of carbon-dioxide electrolyzer cell technologies (just one example: there is no need very precisely pressure control because no flowing catholyte inside the cell), and this allows the scale up of such architectures. Exploring the fundamentals and understanding of the chemistry in zero-gap electrochemical cells is carried out by many research groups, usually with small experimental test cells. These results provide a good scientific basis (e.g., to select the right catalysts, components, or to study long-term degradation, etc.), however, compared to the size of an industrial-scale electrolyzer, these experimental cells only measure a "one point" chemistry. The results cannot be transferred without careful consideration during scale-up, due to several additional challenges. These challenges are mainly of mechanical origin, and all of these create uneven conditions that can significantly affect the chemistry of the on given sections of the cells.Over the past several years, we have gone through the steps of scaling up electrochemical cells (for CO2-to-CO conversion) from a small experimental test cell (8 cm2) to an industrial-sized cell stack (2500 cm2 / cell). During the development journey we encountered many of the challenges outlined above. In this talk, I am going to present some of these challenges, their origins, what affects them and by them, and what principles can be used to find solutions.

(Invited) Unlocking Long-Duration Energy Storage with Unitized Reversible Fuel Cells

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).

(Invited) U.S. Department of Energy’s Hydrogen and Fuel Cell Perspectives

The U.S. Department of Energy (DOE) is supporting a comprehensive research, development, demonstration, and deployment (RDD&D) effort to address the challenges to achieving large-scale commercial viability of hydrogen and related technologies across sectors and applications. An overview will be provided on DOE’s Hydrogen Program, including the National Clean Hydrogen Strategy and Roadmap, and key priorities within the Bipartisan Infrastructure Law, which includes $8 billion for the Regional Clean Hydrogen Hubs and $1.5 billion for the Clean Hydrogen Electrolysis, Manufacturing and Recycling Programs. The presentation will discuss how hydrogen RDD&D activities are advancing the U.S. commitment to tackle the climate crisis through the DOE Hydrogen Program’s H2@Scale vision for clean hydrogen across the economy, and the Hydrogen Energy Earthshot; seeking to cut the cost of clean hydrogen to $1 per 1 kilogram in one decade. A focus of this presentation will be on low temperature electrolysis activities led by DOE’s Hydrogen and Fuel Cell Technologies Office and will include a discussion on current status, key targets, and remaining challenges that need to be addressed to meet Clean Hydrogen Electrolysis Program and Hydrogen Shot goals.

From nickel–metal hydride batteries to advanced engines: A comprehensive review of hydrogen's role in the future energy landscape

Hydrogen has emerged as a disruptive force in the energy landscape, poised to revolutionise the automotive sector with its use in both fuel cell and internal combustion engines. This article covered two topics: application of metal hydrides for hydrogen storage and use of cutting-edge engine technology in hydrogen-powered vehicles. This article begins with discussing the different characteristics of materials that are used to store hydrogen. Metal hydrides, rare earth elements, and carbon-based compounds are among the materials that are carefully studied in this work. Understanding how effectively these materials can store hydrogen was another goal of this research. In order to fully utilize hydrogen's potential, it is imperative to compare them with conventional fossil fuels highlighting their significance. Additionally, this study explains how hydrogen can be used to power existing and newer automobile vehicles. Also discussed are the viability and potential mechanisms of operation for various hydrogen-using engine technologies, such as compression ignition and spark ignition engines. Cutting-edge on vehicles with fuel cell and engine technology powered by hydrogen along with their challenges are explained. They include discussions of several techniques such as homogenous charge compression ignition (HCCI), dual-fuel, and reactivity-controlled combustion ignition (RCCI). Additionally, the advantages and disadvantages of utilizing hydrogen in these state-of-the-art engine technologies are discussed. This research offers insights on the future of automobiles in addition to hydrogen storage. This study points the path towards a more creative and sustainable energy environment in which hydrogen plays a major role in the storage and utilization for automobile vehicles.