Electrolysis of water to produce hydrogen is an attractive option for many customers due to the low hydrogen storage needed, distributed production, and low emissions when powered by renewable energy sources. However, the current cost of producing hydrogen from electrolysis at very large scale is too expensive relative to steam methane reforming of natural gas, due to several factors. First, cell stack manufacturing methods need to be modernized for high precision and throughput. Second, stack technology improvements need to be transitioned from prototypes to volume manufacturing. Finally, easy to install, modular plant designs need to be developed which reduce installation costs. While less technology heavy, this third area is actually the highest cost contributor to hydrogen production from electrolysis. Nel Hydrogen has developed and is executing on strategies for both PEM and alkaline electrolysis to meet these three goals. For alkaline electrolysis, pressurized systems are being developed for smaller footprint, with advanced electrodes for higher efficiency. For PEM, Nel is working in partnership with General Motors to develop novel stack designs at significantly lower cost and higher efficiency. Nel has also developed agreements with integration partners such as Saipem and Samsung to create integrated and optimized designs. This talk will present an overview of Nel’s electrolyzer development in both the United States and Europe, in addition to presenting more detail on advanced proton exchange membrane-based stacks.

Hydrogen crossover in proton exchange membrane water electrolyzers (PEMWEs) poses a safety hazard, reduces the overall efficiency, and limits the operational differential pressure range. In this study, a membrane electrode assembly (MEA) with innovative Pt duo-recombination layer (DRL) design is developed by the unique reactive spray deposition technology (RSDT). The novel design comprises two thin RLs integrated within the volume of the membrane and has a total Pt loading of only 0.04 mgPt cm- 2. Long-term durability test for over 3000 h is performed with as-fabricated MEA at steady-state conditions typical for an industrial hydrogen production system. The results from the durability test show that the newly developed DRL design effectively suppresses the H2 crossover to below 0.5 vol%. Furthermore, comprehensive post-test characterization of the MEA is performed and potential failure mechanisms in the Pt RLs observed during the durability test are identified and discussed in detail for the first time.

Hydrogen generation via electrolysis has gained much attention internationally as not only a sustainable source of fuel for the transportation, but as a carrier of energy to capture stranded renewable energy due to the carbon-free chemical cycle and response characteristics of the technology. The barrier to entry preventing this technology from being widely adopted is the overall cost associated with both the upfront capital expense as well as the operating cost incurred over the product life. The majority of this cost is driven by 1) low electrical efficiencies due to the high ohmic resistance of thicker membranes required by electrolysis systems to electrochemically compress generated hydrogen for storage and the overpotential associated with the water splitting oxygen evolution reaction (OER) catalysts typically used, 2) high cost of system and cell stack materials, which need to be durable for up to 100,000hrs at potentials approaching 2V in both reducing and oxidizing environments, and 3) the lack of a robust supply chain for high volume manufacturing to further drive down cost through economies of scale. Nel Hydrogen has worked to commercialize this technology, originally developed for aerospace and miliary applications where cost and efficiency were not the drivers. Since the founding of Proton Energy Systems in 1996 and to the present as Nel Hydrogen we have worked to address these problem areas in an attempt to develop products that can serve cost sensitive markets, such as energy capture and storage. During this talk, I will look back on the challenges we faced as an industrial start-up dealing with uninterested suppliers, creating relationships, and establishing partnerships, all while developing our first 28cm2 products to the point today, where we are producing and siting multi-MW systems.

Scientists in industry are often confronted with the phrase “...and the rest is just engineering!” by aspiring inventors looking to license a concept that has been demonstrated at lab scale. Sometimes a brute force, trial and error method to make a saleable product can be initially successful. However, this method comes with many risks, including knowledge gaps in the importance and sensitivity of various manufacturing parameters. Deviations from baseline can result in unexpected defects or changes in performance, with little understanding in how to recover. In addition, as volumes are scaled up, out of control processes can generate expensive scrap very quickly. Another aspect of product development is how the customer will really use the product. Testing under ideal conditions often does not provide much predictability around performance in the field. Industrial researchers and developers therefore have to do much more than “just” engineering to successfully make money with a product. Nel (formerly Proton Energy Systems) was originally founded based on publicly available intellectual property around proton exchange membrane water electrolysis, taking a technology platform developed for oxygen generation in closed environments and applying it to commercial hydrogen generation. In the early days of the company, many processes were replicated as is, because they had been proven successful. However, making process changes for increased throughput or cost reductions sometimes pointed out the lack of underlying understanding. In this talk, some historical examples will be presented, as well as methodologies for successfully scaling up electrolysis manufacturing.

Quantifying the relationship between operating conditions and individual electrode behavior is essential for advancing polymer electrolyte membrane fuel cell (PEMFC) technology. Here, a platinum wire embedded within the Nafion membrane was used as a voltage probe to quantify the polarization contributions of individual cell components under varying temperature and humidity conditions. Electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis, combined with dc current-voltage measurements, enabled the deconvolution of ohmic and polarization resistances of each component. The results reveal that, while temperature governs electrode kinetics predominantly, the asymmetric relative humidity significantly influences membrane hydration and interfacial transport. These trends arise from a shift in the dominant water transport mechanism: back diffusion controls membrane hydration at low current density, and electro-osmotic drag dominates at high current density. Moreover, a reciprocal electrode interaction was observed, with the cathode-side DRT peaks changing their position and area in response to anode humidity changes, highlighting the coupled polarization within the PEMFC.

This study presents the validation of protocols for measuring ion exchange capacity (IEC) and alkaline stability of anion exchange membranes (AEMs) for low-temperature water electrolysis. While protocols are often tested within individual laboratories, their results across multiple laboratories with varying equipment, environmental conditions, and personnel qualification remain unverified. The validation involved Los Alamos National Laboratory (LANL), National Renewable Energy Laboratory (NREL), and University of Oregon (UO) using the same commercially available AEM to assess reproducibility and reliability of the protocols under diverse conditions. For the IEC protocol, results across laboratories were consistent within ±10% of the NMR-determined reference value. The alkaline stability protocol could pose greater challenges due to factors such as variations in sample collection timing, preservation methods, and analytical techniques, but consistent test results for percentage IEC loss were demonstrated across institutions. These results highlight the reliability and applicability of the protocols, emphasizing the importance of validation to ensure consistency in diverse research environments.

Development of hydrogen production capacity with low carbon intensity (low carbon dioxide emissions) is an essential part of reaching global sustainability targets and mitigating long term climate change. While electrolysis has been commercial for decades, many applications have been smaller scale, and only a small fraction of the total hydrogen production is made from water rather than methane. In the US, there have also now been 7 Hubs selected which each have minimum targets of 50 metric tons of low carbon hydrogen production per day. The only way to meet these capacities in the near term is with proven commercial technologies such as liquid alkaline and proton exchange membrane (PEM) electrolysis. However, even though PEM technology has been commercial for decades, it has only recently reached megawatt scale, and most “gigafactories” that have been announced are not completely built out or staffed for these demands. It is therefore essential that PEM developers scale manufacturing capacity of cell stacks significantly in the next few years. Experience in commercial installations, manufacturing, and previous scale up are critical to success. Nel Hydrogen US has successfully scaled up cell stack active area by almost 2 orders of magnitude from its earliest products, and has gained decades of real world experience in how different field operation can be from controlled internal tests. The smaller platforms also offer built in verification testing for new designs and manufacturing methods. This talk will discuss Nel’s stack scale up journey, as well as updates on current expansion efforts.

Proton exchange membrane water electrolysis (PEMWE) is a technology that has promise to help decarbonize the hydrogen sector and thus has recently been receiving significant attention. Incentives across the globe, including in the Hydrogen Hubs in the US and the European Hydrogen Bank, have been announced to support early projects and catalyze the industry. The PEMWE market growth was already starting due to recent technological advances and these incentives are helping further accelerate the industry. This acceleration is evident by the number of press releases on manufacturing capacity expansion and large projects being announced. With this market expansion, the industry will inherently demand more iridium – currently the only commercially viable OER catalyst for PEMWE. The mantra of reduce, reuse, and recycle is being applied to iridium where iridium thrifting (reduce) and circularity (recycle) are focal points. The first part of this talk will focus on iridium thrifting. Simply reducing the catalyst loading with today’s baseline technology results in performance and durability loss; therefore, advanced materials and technology must be developed to realize the iridium thrifting goals. Performance and durability data will be presented for state-of-the-art catalyst that enable low iridium loadings. The second part of this talk will cover iridium circularity. Various recycling streams exist including manufacturing waste, manufacturing scrap, and end-of-use devices from the field. The value recovery for each of these waste streams will be discussed and data demonstrating full circularity will be presented.

Nel Hydrogen has in the last decades substantially invested in R&D efforts to consolidate next-generation PEM stacks and systems towards a commercial pathway for these devices at scale. These innovative tasks have allowed the company to reach much lower values for levelized costs of hydrogen (LCOHs) supported by devices that are much more efficient and lower costs; but that still holds robustness and long-life characteristics. However, to truly represent a sustainable pathway, the production lifecycle needs to be considered, especially related to critical materials such as catalysts and polyfluorinated alkyl substances (PFAS) used for instance in the membranes. PFAS are beginning to be regulated globally, with a goal of for responsible manufacturing and hence zero disposal to the environment. Recycling programs for the polymers used in electrolyzers can assist in keeping them exempt from PFAS regulations, due to the minimized environmental impact and lack of related emissions. In addition, PEM electrolyzers use a significant amount of platinum group metals (PGMs), including iridium, one of the scarcest naturally occurring elements. Addressing these issues through recycling and a healthy circular economy of these key components is an important part of large-scale commercialization and deployment. Recent customers have already raised questions about supplier philosophy and documentation of environmental practices. In other words, these large-scale market players are looking for instance to be ISO14001 certified; designed to minimize a company’s negative impact on the environment. While recycling of any chemicals is not specifically required by ISO14001, the standards include lifecycle assessments, integration of environmental aspects into product design, reduction of greenhouse gas emissions, and related topics where recycling would have positive impact on the metrics. At the last 244 th ECS meeting in Gothenburg 2023, we have shown how recycling (or PGM thrifting) is ultimately required to meet the IEA projected capacity demands for electrolyzers by 2050, or around 2500 GW globally. Our analysis has demonstrated that above 40% market share can be reached by 2050 for PEM electrolysis, proven that: 1)20% annual Iridium production (ca. 8 tons/year) is allocated for PEM electrolyzer manufacturing; 2) significant PGM thrifting (above 80%) is demonstrated for these devices; 3) life-time and robustness of these new low loading electrodes are maintained; and 4) a circular economy (responsible recycling) is stablished. Repurposing other components such as titanium, stainless steel, and fluoropolymers provides some additional value stream from reclamation as well. For maximum benefit, material collection methods need to be set up within the manufacturing facility, to capture waste materials and scrap, as well as through the field population, so that systems no longer being operated can be reclaimed for materials. This talk will cover some of the business considerations for effective recycling, as well as current practices.

Water electrolysis is gaining traction in large-scale applications, with production of multiple technologies scaling to hundreds and thousands of megawatts of new electrolyzer capacity annually. Low-temperature electrolysis has dominated the electrolyzer market for decades, but still only represents a small amount of the overall hydrogen market, due to the higher production costs versus hydrogen derived from fossil fuels. Advances are needed in capital cost and efficiency to close the cost gap, especially for energy applications. Similarly, while high-temperature electrolyzers can operate more efficiently, reducing the operating cost, they still need further scale-up and cost reduction to compete in these markets. Understanding the recent advances in each and the priority research directions is important to focus and accelerate innovation, and will be discussed in this article. The different advantages and disadvantages of each of these technologies will also be reviewed; there will likely be applications for each in the overall deployment of renewable hydrogen.

Significant decreases in the price of electricity from solar photovoltaics and wind are enabling concurrent decreases in the cost of clean hydrogen production by water electrolysis. However, to meet the US Department of Energy’s Hydrogen Shot Initiative target for levelized cost of hydrogen production of < $1 per kg of hydrogen by the year 2030,[1] it will also be necessary to drive down the capital costs of water electrolyzers. Reducing capital costs is especially important for scenarios where close to 100% of the electricity is provided by variable renewable energy generators, which greatly limits the capacity factor of the electrolyzer.[2] Towards this end, our team is exploring a proton exchange membrane (PEM) electrolyzer architecture based on ultrathin (< 1 micron) membranes. Modeling is used to show that defect-free membranes possessing appropriate proton and hydrogen transport properties present opportunities to decrease membrane resistances < 80% relative to conventional Nafion membranes, which can subsequently allow for operation at > 4 A cm-2 while maintaining the same efficiencies achieved by today’s commercialized PEM electrolyzers operated at < 2 A cm-2. Additionally, this talk will describe modeling and experimental efforts that address the viability of using sub-micron thick membranes that can operate with H2 crossover rates < 1%. References [1] US DOE Hydrogen Shot Initiative: https://www.energy.gov/eere/fuelcells/hydrogen-shot [2] D.V. Esposito, Joule, 1, 1-8, 2017.

Hydrogen generation via electrolysis has gained much attention internationally as not only a sustainable source of fuel for the transportation, but as a carrier of energy to capture stranded renewable energy due to the carbon-free chemical cycle and response characteristics of the technology. The barrier to entry preventing this technology from being widely adopted is the overall cost associated with both the upfront capital expense as well as the operating cost incurred over the product life. The majority of this cost is driven by 1) low electrical efficiencies due to the high ohmic resistance of thicker membranes required by electrolysis systems to electrochemically compress generated hydrogen for storage and the overpotential associated with the water splitting oxygen evolution reaction (OER) catalysts typically used, 2) high cost of system and cell stack materials, which need to be durable for up to 100,000hrs at potentials approaching 2V in both reducing and oxidizing environments, and 3) the lack of a robust supply chain for high volume manufacturing to further drive down cost through economies of scale. With 95% of hydrogen currently being produced through the reformation of cheap natural gas, significant cost reductions are necessary for electrolysis to become a viable alternative to the incumbent. Commercial proton exchange membrane (PEM)-based electrolysis has reached scales of several hundred kg/day, providing a relevant pathway for industrial scale hydrogen generation with tremendous opportunity for continuing cost reduction by leveraging system and manufacturing scaling laws and advancements in PEM fuel cell materials, manufacturing, and analysis tools. Order of magnitude improvements in some of the highest cost elements are easily achievable and with more research funding being directed towards hydrogen production, the realization of these reductions is occurring at a faster rate. While many improvements in stack design and materials of construction have been identified and implemented, there are still numerous opportunities to explore that would move electrolysis towards a viable, cost-effective alternative to natural gas reformation. This talk will describe some of the areas of success, where research is still needed, and ultimately how each of these improvements translate into cost and the path to reformation parity.

The Hydrogen Economy (HE) is the economy of the near future and is the only viable alternative to the current fossil fuel-based economy. This future green economy will eliminate the greenhouse gas emissions and stop the imminent global warming and climate change. The HE implementation relies on the development of zero-carbon emission technologies for Hydrogen (H 2 ) production. “Green” hydrogen can be produced at large scale by integration of water electrolyzers (WEs) with renewable energy sources. Currently, the proton exchange membrane water electrolyzers (PEMWEs) are considered to be the most advanced WEs that can be integrated with solar panels and wind turbines to produce large quantities of green H 2 . The main challenges that the state-of-the-art membrane electrode assemblies (MEAs) for PEMWEs are currently facing are: (i) high cost because of the high platinum group metals (PGM) loadings in their catalysts layers (2-3 mg PGM /cm 2 in each electrode), and time consuming and expensive multi-step fabrication processes associated with their manufacturing; (ii) limited durability caused by the instability of the catalysts and the other cell components, and (iii) safety concerns associated with the hydrogen gas crossover and the absence of technologies that can effectively keep it below the safety level of the lower flammability limit (LFL) [1, 2, 3]. In this work, we demonstrate the capabilities of a unique methodology for fabrication of advanced catalysts, catalyst layers, and MEAs for PEMWEs, known as Reactive Spray Deposition Technology (RSDT). The RSDT is a flame assisted method [4, 5] that combines the catalysts synthesis and deposition directly on the PEM membrane in one-step, which results in fast and facile fabrication of large scale (up to 1000 cm 2 ) MEAs for application in PEM fuel cells and water electrolyzers [5, 6]. This technology allows precise control of the composition, morphology, and particle size distribution of a wide range of nanoparticles, supported and unsupported on carbon, and ensures fine tuning of the catalysts’ activity and durability. MEAs with geometric areas of 86 cm 2 and 680 cm 2 , both with one order of magnitude lower PGM loading in their catalyst layers in comparison to the state-of-the-art MEAs for PEM water electrolyzers [6,7], are fabricated by the RSDT and evaluated for up to 5000 hours at current density of 1.8 A cm -2 , 50 o C, and 400 psi differential hydrogen pressure. Diagnostic tests that include polarization curves, electrochemical impedance spectroscopy, linear sweep voltammetry, and hydrogen crossover measurements are performed periodically in order to evaluate the cell performance change during the long-term durability test. After the test, the MEAs are disassembled and subjected to comprehensive post test analysis. A wide range of techniques, including high-resolution TEM, STEM, EDS, SEM, ICP, XCT, XPS, and digital optical microscopy, have been used to study the degradation mechanisms governing the performance loss in the MEAs during the long-term steady state operation. The results from these tests will be presented and discussed in detail in this talk. References https://www.energy.gov/sites/prod/files/2017/05/f34/fcto_myrdd_fuel_cells.pdf https://www.energy.gov/sites/prod/files/2015/06/f23/fcto_myrdd_production.pdf Klose, P. Trinke, T. Böhm, B. Bensmann, S. Vierrath, R. Hanke-Rauschenbach, and S. Thiele, J. Electrochem. Soc. , 165 , F1271–F1277 (2018). Kim, S., Myles, Maric, R., et al. Electrochimica Acta , 177, 190-200 (2015). Yu, H., Baricci, A., Bisello, A., Bonville, L., Maric, R., et al. Electrochimica Acta , 247, 1155-1168 (2017). Mirshekari, G., Ouimet, R., Zeng, Z, Yu, H., Bliznakov, S., Bonville, L., Niedzwiecki, A., Errico, S., Capuano, C., Mani, P., Ayers, K., Maric, R. International Journal for Hydrogen Energy , 46(2), 2021, pp. 1526-1539 (2021). Ayers, K. Current Opinion in Electrochemistry , 18 , 9–15 (2019).

Proton exchange membrane (PEM) electrolysis has advanced significantly in the last 10 years, scaling from units in the sub 100 kW range to installed systems at 10 megawatts and greater. This technology, among others, is likely to play a major role in decarbonizing the industry, transportation, and energy sectors, as both the cost of electrolyzer technology and the renewable energy to power it have decreased. Still, the capital cost of electrolysis needs to be further reduced to economically replace hydrogen from steam methane reforming in very large applications, especially as capacity factor goes down to take advantage of the lowest cost electricity. There is also significant potential to decrease cost, as electrolyzer manufacturing is still relatively undeveloped. PEM electrolysis has been developed for many decades and is proven as a reliable, scalable technology. However, electrodes are overdesigned due to the manual methods used to produce them, as well as the aerospace legacy of these systems. Many advancements such as reductions in catalyst loadings, use of thinner membranes, novel porous transport layers, and alternate cell configurations have been shown to be feasible in the lab, but have been slow to transition to commercial products. There are many factors in this lag, including the need to often change manufacturing methods when moving from the lab to a product environment. While this effort is sometimes viewed as “just engineering”, there is significant fundamental understanding required to translate a slow, manual process where finished parts can be individually scrutinized, to a fast, automated process that has to include automated inspection as well. For example, a catalyst ink that is hand painted onto a substrate will need different properties and formulation to deposit the catalyst by spray printing, or yet different properties for other methods such as slot die or gravure printing. Determining acceptability of the resulting parts can no longer rely on human judgment but must be well enough understood that the most important properties can be quickly measured and analyzed in real time. In addition, the scale over which high quality needs to be achieved increases by orders of magnitude when moving from lab scale to product scale. This talk will discuss these types of challenges and approaches to solve them.

The transport of protons and molecular hydrogen (H 2 ) are of relevance to a wide range of electrochemical applications ranging from fuel cells and electrolyzers to sensors and photoelectrochemical cells. One way to modulate the flux of these species to improve device performance such as selectivity and efficiency is to encapsulate electrodes with semi-permeable oxide coatings. [1-3] Thus, knowing the permeabilities of these species within thin oxide layers is of great importance for guiding the design of electrodes and devices. Towards this end, we have employed a modified rotating disk electrode (RDE) set-up to quantify proton and hydrogen permeabilities through sub- 20 nm thick silicon oxide coatings and understand how these transport properties change as a function of the structural and compositional characteristics of the coatings. Oxide coatings were fabricated by both atomic layer deposition (ALD) and photochemical deposition, and their physical and chemical properties characterized by X-Ray Photoelectron spectroscopy and ellipsometry. Based on measurements of the mass transfer limited current density for the hydrogen evolution and hydrogen oxidation reactions, permeabilities were computed. Species permeabilities are furthermore correlated with membrane density and composition, revealing structure-property-performance relationships that can be used to guide the selection of oxide thickness and processing conditions that will optimize performance for an application of interest. References: [1] Labrador, N. Y., et al. Hydrogen evolution at the buried interface between Pt thin films and silicon oxide nanomembranes. ACS Catalysis 8, 1767-1778 (2018). [2] Beatty, M. E., Gillette, E. I., Haley, A. T. & Esposito, D. V. Controlling the Relative Fluxes of Protons and Oxygen to Electrocatalytic Buried Interfaces with Tunable Silicon Oxide Overlayers. ACS Applied Energy Materials 3, 12338-12350 (2020). [3] Bhardwaj, A. A., et al. Ultrathin silicon oxide overlayers enable selective oxygen evolution from acidic and unbuffered pH-neutral seawater. ACS Catalysis 11, 1316-1330 (2021).

Porous transport layers (PTLs) serve many important functions for proton exchange membrane water electrolyzers. PTLs facilitate fluid transport towards and away from the anode catalyst layer, act as a mechanical support for the membrane, and provide electrical contact with the anode catalyst layer [1]. As a result, PTLs can greatly impact cell performance. However, while there has been an effort to improve similar gas diffusion layers in PEM fuel cells, there has not been a significant effort to optimize the overall form factor and design of PTLs for PEM water electrolyzers. One of the primary concerns about the current design of PEM water electrolyzer PTLs is how they interact with the anode catalyst layer. In order to ensure proper fluid transport through the PTL, there is significant porosity throughout the PTL including at the anode interface. The large porosity and particle sizes of the PTL can cause heterogeneous contact of the PTL and catalyst layer thus reducing the catalyst utilization. Therefore, high catalyst loadings are required to obtain acceptable performance and durability. One method to address this concern would be to develop a metal microporous layer (MPL) that can be integrated onto a PTL at the anode interface that can withstand the high potentials at the anode while maintaining sufficient fluid transport. The MPL is fabricated using smaller metal particle sizes compared to the bulk PTL, which results in smaller pores creating a more uniform surface. The uniform surface and small pore sizes of the MPL provide a much higher interfacial contact area at the anode interface compared to a traditional PTL and would allow for a more uniform contact pressure across the anode interface. Higher interfacial contact will improve catalyst utilization and facilitate the reduction in anode catalyst loading, leading to reductions in overall electrolyzer capital cost [2]. In this work, prototype PTLs with metal MPLs are developed and tuned for optimal PEM water electrolyzer cell performance. The prototype PTLs with MPLs are characterized to understand how specific properties (thickness, porosity, tortuosity, etc.) influence cell performance. Electrochemical testing shows that adding an MPL at the anode/PTL interface can allow for acceptable cell performance with 90% lower anode catalyst loading compared to when using a baseline PTL. References [1] X.-Z. Yuan, N. Shaigan, C. Song, M. Aujla, V. Neburchilov, J.T.H. Kwan, D. P. Wilkinson, A. Bazylak, K. Fatih. The porous transport layer in proton exchange membrane water electrolysis: perspectives on a complex component. Sustainable Energy & Fuels, 6, (2022), 1824-1853. [2] T. Schuler, J.M. Ciccone, B. Krentcher, F. Marone, C. Peter, T.J. Schmidt, F.N. Büchi. Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis. Advanced Energy Materials, 10, (2019), 1903216

A Unitized Reversible Fuel Cell (URFC) system provides many benefits for energy storage by combining a fuel cell and an electrolyzer into a single stack, thus simplifying the system while decreasing weight, footprint, and material costs. URFC systems usually have low overall efficiency due to conflicting optimal operating conditions required for electrolyzer and fuel cell. This study optimized the membrane electrode assembly of the proton exchange membrane cell components to achieve 50% round trip efficiency and reliable performance under relevant duty cycles. Several components have been studied in this project including membranes, bifunctional catalysts for oxygen reduction and evolution reactions and porous transport layers (PTL). Different strategies have been applied to increase the overall performance of the stack while maintaining a low degradation rate. In particular, we looked at reducing the thickness of membranes as well as increasing the operating temperature. A comprehensive study of bifunctional catalyst has been carried out by varying the ratio of catalysts suitable for OER and catalysts suitable for ORR. Variation of the hydrophilicity of the PTL has been done to identify the optimum amount in terms of water and gas transport in the layers for both modes of operation.

Women have made significant contributions to applied physics research and development, and their participation is vital to continued progress. Recognizing these contributions is important for encouraging increased involvement and creating an equitable environment in which women can thrive. This Roadmap on Women in Applied Physics, written by women scientists and engineers, is intended to celebrate women’s accomplishments, highlight established and early career researchers enlarging the boundaries in their respective fields, and promote increased visibility for the impact women have on applied physics research. Perspectives cover the topics of plasma materials processing and propulsion, super-resolution microscopy, bioelectronics, spintronics, superconducting quantum interference device technology, quantum materials, 2D materials, catalysis and surface science, fuel cells, batteries, photovoltaics, neuromorphic computing and devices, nanophotonics and nanophononics, and nanomagnetism. Our intent is to inspire more women to enter these fields and encourage an atmosphere of inclusion within the scientific community.

Water electrolyzers are today of worldwide strategic importance for the deployment of green hydrogen as an energy carrier, and the ultimate integration of stochastic renewable energies into the electrical grid at scale. Targets for the total cost of ownership of hydrogen have been constantly revised, but values around $1 to $2 per kilogram of H 2 are generally accepted to reach parity with other energy conversion and storage strategies. However, further advancement of electrolyzers while maintaining durability and robustness of its cell/stack components is still needed. This can only be accomplished through focused research and development efforts that address efficiency, degradation, and cost aspects of the technology. A growing number of research groups are starting to participate in this development with key contributions in the form of fundamental and material advances. However, the high deviation of reported results as well as the complex history the tests performed, and components used have shown that this growth creates challenges that hinder the development of trust in the test results generated. Moreover, such lack of trust ends up hampering the overall progress and leads to wasted allocated resources. Contributors to the HydroGEN Advanced water splitting Materials, Energy Materials Network; and H2-New programs funded by the Department of Energy in the USA; aligned with efforts by the International Energy Agency (IEA) within the Electrolysis Annex 30 are conducting a benchmarking effort: 1) to develop methods to identify reference hardware, cell components, and materials; and 2) to harmonize testing protocols and enable the meaningful comparison of performance across the community. In this presentation, the latest results of this effort will be presented. The talk will also include updates on current strategies among the different teams, round robin testing results, protocol development and fine tuning of test parameters and material specifications. This effort should finally lead to the creation, validation, dissemination, and adoption of accelerated test protocols that can ultimately contribute to conducting collaborative studies on cell and stack degradation.