bluuebunny/crossref_metadata_2025 huggingface dataset:
An Open-Source Continuum Model for Anion-Exchange Membrane Water Electrolysis
Authors: Gerhardt Michael Robert , Barnett Alejandro O , Khoza Thulile , Fortin Patrick , Andrenacci Sara , Faid Alaa Y. , Karstensen Pål Emil England , Sunde Svein , Clark Simon
Published: September 2023

Anion-exchange membrane (AEM) electrolysis has the potential to produce green hydrogen at low cost by combining the advantages of conventional alkaline electrolysis and proton-exchange membrane electrolysis. The alkaline environment in AEM electrolysis enables the use of less expensive catalysts such as nickel, whereas the use of a solid polymer electrolyte enables differential pressure operation. Recent advancements in AEM performance and lifetime have spurred interest in AEM electrolysis, but many open research areas remain, such as understanding the impacts of water transport in the membrane and salt content in the electrolyte on cell performance and degradation. Furthermore, integrating electrolyser systems into renewable energy grids necessitates dynamic operation of the electrolyser cell, which introduces additional challenges. Computational modelling of AEM electrolysis is ideally suited to tackle many of these open questions by providing insight into the transport processes and electrochemical reactions occurring in the cell under dynamic conditions.

In this work, an open-source, transient continuum modelling framework for anion-exchange membrane (AEM) electrolysis is presented and applied to study electrolyzer cell dynamic performance. The one-dimensional cell model contains coupled equations for multiphase flow in the porous transport layers, a parameterized solution property model for potassium hydroxide electrolytes, and coupled ion and water transport equations to account for water activity gradients within the AEM. The model is validated with experimental results from an AEM electrolyser cell. We find that pH gradients develop within the electrolyte due to the production and consumption of hydroxide, which can lead to voltage losses and cell degradation. The influence of these pH gradients on potential catalyst dissolution mechanisms is explored and discussed. Finally, initial studies of transient operation will be presented.

This work has been performed in the frame of the CHANNEL project. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under grant agreement No 875088. This Joint undertaking receives support from the European Union's Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research. Some of this work has been performed within the MODELYS project "Electrolyzer 2030 – Cell and stack designs" financially supported by the Research Council of Norway under project number 326809.
A Novel Stack Approach to Enable High Round Trip Efficiencies in Unitized PEM Regenerative Fuel Cells
Authors: Keane Alex , Roemer Andy B. , Roberts George , Junker Toby , Capuano Christopher , Ayers Katherine E. , Wang Shiyi , Weber Adam Z.
Published: September 2023

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.
A Study on the Electrochemical Performance of MOF Based HER Catalysts for Anion Exchange Membrane Water Electrolysis
Authors: Lee Hyein , Cho EunAe
Published: September 2023

Recently, research on anion exchange membrane water electrolysis (AEMWE) has been conducted, which has the advantage of using a non-noble transition metal catalyst to reduce cost and improve the activity and durability of the catalyst. In alkaline solutions, heterojunction catalysts are favored because the rational design of catalysts requires the ability to simultaneously dissociate water and bind hydrogen species.

In this study, N-doped carbon hollow polyhedron (NCHP) supports were synthesized using two types of metal-organic frameworks (MOFs) to enhance catalyst durability by effective active site-support interactions. Moreover, well dispersed MoC on MOFs with regularly connected metal nodes and organic ligands increased the number of active sites and improved the reaction kinetics owing to the synergistic effects between MoC and Co@NC, which enhanced the hydrogen evolution reaction (HER).

The formation mechanism of NCHP was confirmed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. During the half-cell test, the incorporation of MoC (MoC-Co@NC/NCHP) reduced the HER overpotential by approximately 1.8 times at 10mA/cm2 compared with that of Co@NC/NCHP. Furthermore, durability cycling was conducted from 0.1 to -0.6 V versus a reversible hydrogen electrode (RHE). The durability tests revealed that after 3000 cycles, the reduction in the HER current of MoC-Co@NC/NCHP was 1.4 and 2.7 times lower than those of Co@NC/NCHP and commercial Pt/C, respectively. This study provides two strategies to obtain highly stable NC matrix supports and highly active heterojunction catalysts.
Boosting Ethanol Oxidation by
3d
transition Metal-Based Nano-Heterostructure for Energy-Saving Hydrogen Production and Biomass Upgrading
Authors: Sun Hainan , Jung WooChul
Published: September 2023

Substituting the anodic oxygen evolution reaction in water electrolysis with a thermodynamically more favorable ethanol oxidation reaction (EOR) provides a promising route for simultaneous biomass upgrading and energy-saving hydrogen production. Herein, we synthesize a NiOOH-CuO nano-heterostructure anchored on a three-dimensional conductive Cu foam, which exhibits remarkable EOR performance, surpassing all the state-of-the-art
3d
transition-metal-based EOR electrocatalysts. Density functional theory reveals that the coupling between CuO and NiOOH by charge redistribution at the interface is critical, synergistically reducing the EOR energy barriers into an energetically favorable pathway. Conclusively, the hybrid water electrolysis cell using our catalyst as the anode (1) requires only a low cell voltage for H2 generation at the cathode and only liquid chemical production of acetate at the anode, and (2) shows a high ethanol conversion rate to acetate, which can readily be separated from the aqueous electrolyte by subsequent acidification and extraction processes.
Catalyst Application in Three-Dimensional Porous Electrodes for Alkaline Electrolysis
Authors: Russo Andrea , Jensen Jens Oluf , Kraglund Mikkel Rykær , Zhang Wenjing (Angela) , Cho EunAe
Published: September 2023

Hydrogen is critical in the green transition, and a key system for producing green hydrogen is through alkaline electrolysis. Although the alkaline electrolyzers are mature and commercially available, vast improvements are still expected in the future 1.

Traditional and most commercially applied alkaline electrolyzer electrodes are made from massive nickel plates (or nickel-plated steel plates) with some scattered perforation. With the ongoing development of thin alkaline ion‐conducting membranes with low internal resistance, the benefit of three‐dimensional porous electrodes becomes obvious. With such electrodes, there will be no blind spots and the active catalytic area can be increased significantly. Today, most groups developing such 3D electrodes use commercial nickel foam as substrate. This limits the options to what is available in the market, moreover the purchase cost is high.

The present work aims at developing high‐performing three‐dimensional hydrogen and oxygen evolution electrodes for alkaline electrolysis. The focus will be on the application of nanostructured electrocatalysts into three‐dimensional electrode structures, similar to nickel foams.

The results obtained, so far, show homogeneous formation of nanoparticles on the surface. The analysed samples show mechanical flexibility as soon as the particles are deposited but samples become rigid after testing in a half cell setup with KOH 1 M electrolyte. Further analysis will explore changes to the microstructure. The roughness factor calculated by non-faradaic cyclic voltammetry is in the range of 75 cm2 ECSA / cm2geometric, showing higher value than the commercial Nickel foam.

Initial experiments are carried out on as-prepared samples, but more advanced catalysts are also explored based on state-of-the-art materials.

[1] IRENA - Green Hydrogen Cost Reduction: Scaling up Electrolysers to Meet the 1.5 °C Climate Goal, International Renewable Energy Agency, Abu Dhabi (2020)
Uniformly Dispersed Cobalt Catalyst on the Coffee Waste-Derived Carbon Support for Hydrogen Evolution Reaction
Authors: Sukhbaatar Bayaraa , Seo Jinmyeong , Qing Wang , Yoon Sanghwa , Yoo Bongyoung
Published: September 2023

The research interests in transition metal catalysts on carbon support have increased last decade for expensive noble metal catalyst replacement. Because those catalysts have a large surface area, good chemical stability, and are cheap and earth-abundant. Mainly structured with Co-N-C catalysts such as Cobalt (Co) nanoparticle embedded N-doped carbon, Co single-atom catalyst on carbon, etc., are highly efficient for hydrogen evolution reaction (HER) in acidic and alkaline electrolytes.

Here, we report the uniformly dispersed cobalt catalysts (Co-SCC-N) on nitrogen (N)-doped spent coffee grounds (SCG) derived carbon support, which was further utilized as HER electrocatalyst. In the first step, SCG-derived carbon is synthesized by simple pyrolysis with ZnCl2. Then, the cobalt catalyst is prepared by adsorption of the complex Co ion with 1,10-phenanthroline on the SCG-derived carbon support, followed by pyrolysis at 800°C under a nitrogen atmosphere. Uniform and high dispersions of cobalt on the carbon substrate have been confirmed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) elemental mapping analysis. X-ray photoelectron spectroscopy (XPS) determined that the catalyst contained Co2+ ions and had nitrogen-doped. Also, X-ray diffraction (XRD) and Raman spectroscopy revealed carbon materials disorders, crystallinity, and no metal-related peaks that validated no metal clusters on the carbon. Electrochemical tests were examined by linear sweep voltammetry, Tafel, electrochemical impedance spectroscopy, and chronopotentiometry (CP) in alkaline and acidic electrolytes. Co-SCC-N exhibited excellent HER performance in an alkaline medium, which needed 0.246 V to reach 10 mA cm-2. And the CP test confirmed better stability at 10 mA cm-2 for 12 hours. The result recommends a simple synthesis method for uniformly dispersed metal catalysts on biomass-derived carbon support by a simple pyrolysis technique.
Effect of Metal-Substitution within Ruthenium Oxide on Structure and Oxygen Evolution Activity and Stability
Authors: Albiter Luis A , Bailey Kathleen O. , Godinez Salomon Jose Fernando , Rhodes Christopher P.
Published: September 2023

The development and utilization of proton exchange membrane water electrolyzers (PEMWEs) is hindered by the cost, activity, and stability of the oxygen evolution reaction (OER) electrocatalyst. Iridium oxide (IrOx) is currently the go-to OER electrocatalyst, as it has been shown to have relative high activity and stability when compared to other OER active catalysts. However, iridium is one of the rarest elements in the Earth’s crust, and therefore cost is a major limitation of iridium-based electrocatalysts. Ruthenium oxide (RuO2) is much lower cost and more active than iridium oxide; however, RuO2 it is unstable in acidic media and undergoes degradation over time. We investigated substituting niobium, tantalum, and zirconium, which are OER-stable metals, into RuO2 to improve the OER stability. Our study explored the effects of different metals and varied concentrations within RuO2 (Ru1-xMxO2, M = Nb, Ta, and Zr) on the structure, morphology, OER activity, and stability. The structure and morphology were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and scanning electron microscopy. Preliminary results from XRD showed observable phase separation at higher concentrations of Nb, Ta, and Zr and less phase separation at lower concentrations for Nb and Ta. There was no observable phase separation for Zr at lower concentrations. XRD peak shifts were observed and indicate the incorporation of the metal ions into the crystal structure of rutile RuO2. The OER activities and stabilities of Ru1-xMxO2 were measured using a rotating disk electrode configuration and compared with synthesized RuO2. Our preliminary results show that the OER activity and stability are strongly affected by the addition of the different metals and could be attributed to morphology and structural changes. Our findings help to further the development of lower cost, high activity, and increased stability OER electrocatalysts, which are crucial to the large-scale adoption of PEMWE’s.
Durability and Performance of Poly(norbornene) Membranes and Ionomers in Alkaline Electrolyzers
Authors: Park Habin , Tee Hui Min , Shah Parin , Dietrich Chandler , Kohl Paul
Published: September 2023

Ion conducting polymer electrolytes provide an enabling technology for low-temperature alkaline electrolyzers. The critical parameters of solid polymer electrolytes include ionic conductivity, ion selectivity, chemical resistance and dimensional stability in the presence of excess water. High pH operation using anion conductive polymer electrolytes has several potential advantages over acid-based polymer devices including low-cost catalysts, hydrocarbon (non-perfluorinated) polymer, and low cost cell components.

In this study, a family of hydroxide conducting, poly(norbornene) solid polymer electrolytes were synthesized and used in high-performance, durable membrane electrode assemblies for fuel cells and electrolyzers. In addition to membranes, covalently bonded, self-adherent, hydroxide conducting ionomers were used to form high-performance, durable membrane electrode assembly for water electrolysis. The self-adhesive ionomers and membranes are based on hydroxide conducting poly(norbornene) polymers. The effect of porous transport layer material and porosity was examined. High performance electrolysis with very low degradation rates was achieved using stainless steel and nickel porous transport layers and flow-channels
Mechanical and Physio-Chemical Properties of Anion Exchange Membranes and Their Implications on Industrial Scale Water Electrolysis
Authors: Klinger Andre , Schmid Guenter , Martic Nemanja , Strobl Oscar , Kress Michael , Michaels Hannes , Ignat Teodora , Maltenberger Anna
Published: September 2023

Siemens Energy Global GmbH & Co. KG - Sustainable Energy Systems, Otto-Hahn-Ring 6, 81739 München

Membrane based water electrolysis can operate under acidic or alkaline conditions, depending on the nature of the conducting ion in the membrane. Proton conducting membranes became commercially available and sufficiently stable over the last decades, enabling to scale PEM (ProtonExchange Membrane) – electrolysis in the tens of MW range1,2 approaching GW plants.

Anion Exchange Membranes (AEM) suffered mainly from limited hydroxide stability. In recent years, AEMs with sufficient initial stability and semi-commercial availability on pilot size draw the attention of industry to invest in developing in AEM electrolysers3,4. On research scale, AEMs are mainly characterized by their ion exchange capacity, conductance, ASR, tensile strength or elongation at break5,6. For industrial application, parameters such as swelling, water uptake, permeability or solubility and viscosity of the corresponding ionomer set boundary conditions for scaling cell sizes into the square meter range and the applicability of high volume manufacturing or coating methods.

In the presentation, physio chemical properties of membranes (swelling, water uptake, IEC, conductance, stress/strain and anisotropy ) are brought in context to requirements for > 1000 cm² industrial membrane electrolysis. Investigations on ex-situ characterization of membranes are being compared to different membrane chemistries and implications for larger cell sizes are derived. First results of durability tests at 1.5 A/cm² and potential degradation mechanisms will be presented in an Ir-free electrolysis cell. Changes of morphological features of the membrane electrode assembly are

being examined by optical and scanning microscopy techniques. Membrane parameters will be correlated to the electrochemical performance (impedance, endurance) in 25 cm² cells. Relevant ex-situ measurable properties are compiled for discussion with the audience.

ACKNOWLEDGEMENT

The investigations were partly funded by the BMBF under the contract number AEMready

(FKZ:03SF0613B).

REFERENCES

1 https://www.siemens-energy.com/global/en/offerings/renewable-energy/hydrogen-solutions.html?gclid=EAIaIQobChMIsuu-wMHV wIVktZ3Ch24ngoYEAAYASAAEgJUF_D_BwE.

2 https://press.siemens-energy.com/global/en/pressrelease/new-production-facility-berlin-siemens-energy-wants-eliminate-worlds-most-potent .

3 https://www.enapter.com/applications

4 https://www.enerstack.eu/

5 D. Henkensmeier, M. Najibah, C. Harms, J. Zitka, J. o. Electrochemical Energy Conversion and Storage, 2021, Vol. 18, 024001

6 K.M. Meek, C.M. Antunes, A. Neyerlin, B.S. Pivovar, “High-Throughput Anion Exchange-Membrane Characterisation at NREL”, Electrochemical Engineering & Materials Chemistry, National Renewable Energy Laboratory, Gold, Colorado, USA
(Invited) The Design, Fabrication, and Operation of a MW-Scale Low-Temperature Electrolyzer System to Support Industry and the U.S. Dept. of Energy
Authors: Harrison Kevin William , Victor Claire , Smith Owen , Kirschbaum Asher , Sievers David
Published: September 2023

Over the last 15 years the National Renewable Energy Laboratory (NREL) has supported industry and the U.S. Department of Energy by providing independent evaluation and performance validation of next generation electrolyzer stacks. Designated a U.S. Department of Energy user facility, the Energy Systems Integration Facility (ESIF) houses a comprehensive balance-of-plant infrastructure designed to support a wide range of drop-in electrolyzer stacks with capacities of up to 1 MW direct current (DC) electrical power. This NREL designed and fabricated infrastructure includes four individual power supplies (250V, 4000A Total), high-quality and high-flow deionized water (DIW) supply (up to 300 GPM), water polishing and particulate filters to achieve better than 10MΩ-cm resistive water, heat rejection via a plate heat exchanger and facility chilled water, gas/liquid phase separation of hydrogen and oxygen from water, and a hydrogen dryer bed to reduce water vapor content to less than 5 parts per million by volume to enable compression, storage and use in a wide variety of applications including light- and heavy-duty fueling, onsite fuel cell research and development (R&D), and biological and thermochemical processes requiring hydrogen. Safety, monitoring, data archiving, and control of the electrolyzer and balance of system are achieved using custom controls programmed specifically to achieve a safe and flexible architecture.

Robust and redundant safety systems ensure safe and reliable long-duration, unattended operation of the electrolyzer with downstream compression equipment and systems consuming the product gas directly from the stack. Working with a small business, NREL is working to develop a low-cost individual cell voltage (iCVM) monitoring system capable of monitoring 100’s of cell voltages in the 2 – 3V range at a rate of 1 sample per second. The presentation will highlight critical safety considerations including reliable hydrogen-in-oxygen monitoring, lessons learned, and performance date taken over last 15 years of designing, building, and operating lab- and megawatt-scale low-temperature water electrolyzer systems.
(Invited) Electrolyser Manufacturing Scale-up Versus Design Development for Meeting Green H2 Targets
Authors: Fahy Kieran , Sinanan Anson , Joos Nathan
Published: September 2023

Cummins-Hydrogenics pioneered our MW-scale PEM electrolysis cell stack architecture in 2012 and has built and operated multiple sites since, including the 20 MW Bécancour facility for Air Liquide from 2020. Lessons learned from these projects provide a springboard for large-scale manufacturing and deployment of PEM electrolysers worldwide and Cummins has announced GW-scale manufacturing deployment in Europe, N America and Asia. This is required to meet the growing global demand for PEM electrolysers, which derives from the targets and subsidies for green hydrogen production announced by many governments.

Concurrent to this manufacturing scale-up, significant work on cost reduction and technology advancement is ongoing resulting in anticipated cost decreases from catalyst loading (Ir<150g/MW), efficiency improvements (<46 kWh/kg) and higher current density, all of which need to be achieved for commercial viability. Driving down the Ir-loading of PEM electrolysers while increasing current densities will remain the primary driver of CapEx reductions in the short to medium term but the deployment of large-scale manufacturing also allows for significant economies of scale. Recycling and regeneration of used components will also become a larger issue and new processes need to be implemented for each stack component.

Moving from a project-based design methodology to design for volume manufacturing, all while maintaining the fast pace of technology development, makes for significant challenges and can lead to processing waste and inefficiencies. Rigorous testing and validation protocols are needed across the industry in order to successfully scale-up while implementing technology improvements necessary to meet TCO targets. This talk will focus on the juxtaposition of these challenges and ways to mitigate future risks.
Durability Study of Anode Catalysts from Iridium-Based Titanium Supports in Polymer Electrolyte Membrane Water Electrolyzers
Authors: Li Kui , Wang Xiaojing , Mukundan Rangachary , Spendelow Jacob S. , Komini Babu Siddharth
Published: September 2023

Electrochemical water splitting has been recognized as one of the most promising methods for hydrogen production. Electrocatalysts are critical materials in water electrolysis. The sluggish reaction kinetics for the anode reaction, oxygen evolution reaction (OER), hinders the development of water electrolysis technology. Iridium-based material is an leading catalyst for OERs, but the high scarcity and high cost limit its application in polymer electrolyte membrane water electrolyzers (PEMWEs). Moreover, Ir dissolution during the OER operation is another limitation. Robust and effective support-based catalysts should be developed to reduce the catalyst loading and provide high durability in PEMWEs. Herein, we synthesized an OER catalyst of Ir deposited on Ti supports using a polyol reduction method. The Ir/Ti catalysts with different Ir loading were prepared and applied in the PEMWEs for performance evaluation. The cell performance (Figure 1A) with the optimized catalyst (Ir/Ti-50%Ir) exhibited better performance than the commercial IrO2 in the same low loading (0.1 mgIr cm-2) and very close current density (<10 mV difference) achieved at 4 A cm-2 as to the electrode with a high catalyst loading (0.4 mgIr cm-2). Accelerated stress tests (ASTs) performed between 2.0 V and 1.45 V were used to investigate the catalyst durability in the PEMWEs. Figure 1B shows a volcano shape for the correlation between degradation behavior and Ir percent in the catalyst. Our results, combined with the ex-situ characterization, provide a synthesis strategy for robust OER catalysts, and elucidate the catalyst degradation mechanism in the PEMWEs.

Figure 1
Green Hydrogen via PEM Electrolysis – Avoiding Iridium Supply Limitations
Authors: Clapp Mark , Zalitis Christopher Mark , Ryan Margery
Published: September 2023

Proton exchange membrane water electrolysis (PEMWE) is projected to become a key technology to enable the decarbonisation of ‘hard to abate’ sectors of the economy. However, the technology’s reliance on iridium, one of the scarcest elements on Earth, as an oxygen evolution reaction catalyst, has led to uncertainty over whether a large-scale PEMWE industry can be realised. This work investigates the future iridium demand of the global PEMWE sector and examines how different catalyst strategies can improve iridium utilisation in the anode catalyst. Iridium utilisation targets necessary to avoid a situation where the PEMWE sector becomes limited by iridium supply are reviewed. Modelling the iridium demand of the PEMWE sector showed that iridium utilisation needs to improve by an order of magnitude by 2050 to avoid iridium supply limiting the capacity expansion. Furthermore, closed-loop recycling of iridium would increase the installed capacity in 2050 by 170%. If these two conditions are met, global PEMWE capacity could reach 1.3 TW by 2050 using only 20% of annual global primary iridium supply, which we consider to be realistic given future demand projections. Different types of iridium-based anode catalysts are compared in terms of iridium utilisation using catalyst coated membrane (CCM) testing data from the literature. The need to place greater research focus on catalyst stability and the ability to make homogeneous catalyst layers at low iridium loadings is established. As a main result, it is found that a terrawatt-scale PEMWE industry can avoid being constrained by iridium supply as long as technological development of a similar level to that seen in PEM fuel cells and high iridium recycling rates are realised.

Reference: Perspectives on Current and Future Iridium Demand and Iridium Oxide Catalysts for PEM Water Electrolysis, submitted to Catalyst Today ‘Catalysis for the Future’ special edition.

Figure 1
Magnetron-Sputtered Thin-Film Catalyst with Low-Ir-Ru Content for Water Electrolysis: Long-Term Stability and Degradation Analysis
Authors: Hrbek Tomas , Kúš Peter , Kosto Julia , Rodriguez Miquel , Matolínová Iva
Published: September 2023

Proton Exchange Membrane Water Electrolyzers (PEM-WEs) are entering the phase of commercial mass production. However, the issue of an iridium catalyst for the anode remains. This work presents an iridium-ruthenium-based catalyst (25% Ir = 158 µg cm-2, 75% Ru) prepared as a thin film on the surface-enhanced-anode of PEM-WE via magnetron sputtering. Using a strictly practical single-cell approach, without any iR corrections, we show its excellent activity – 1 A cm-2 at 1.606 V, 80 °C, and stability – 1.3 µV h-1 at 1 A cm-2 for 500 hours. Together with a purely Ir-based catalyst (158 µg cm-2), we subject it to a massive electrochemical and material analysis, showing that the thickness and interconnectivity are essential for the catalyst’s stability. This conclusion is based on results from single-cell galvanostatic measurements, Potential Electrochemical Impedance Spectroscopy (PEIS), Scanning Electron Micrsocopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and Energy Dispersive X-ray spectroscopy (EDX). Consequently, we believe that magnetron sputtering is currently the most perspective method for preparing low-Ir-loading catalysts. Compared to the nanoparticle approach, it allows the creation of very thin films with unprecedented interconnectivity.
Iridium Deposited on Niobium-Doped Titanium Dioxide (NbTiO) for High-Stability and Effective Oxygen Evolution Reaction (OER) Catalyst in Acidic Environment
Authors: Tran Hoang , Nong Hong Nhan , Kroschel Matthias , Zlatar Matej , Cherevko Serhiy , Strasser Peter
Published: September 2023

The state-of-the-art iridium-based catalyst, which is the trade-off between activity and durability during acidic OER, needs to be distributed on low-cost effective support materials for the economical utilization of electrolyzers.1 Normally, dopant is introduced into the oxide lattice structure in order to improve the conductivity of the support, which in turn can diminish the Iridium loading content. In this talk, niobium doped titanium dioxide (NbTiO), which is proved to have promising durability in acidic OER conditions, is applied for supported Ir-based catalyst. Based on the powder compression method for conductivity measurement,2 the resistivity of synthesized Nb-doped TiO2, with niobium content of 10 at. % (NbTiO10), is about tens times lower than the resistivity of anatase TiO2 (a.TiO2). Which, in turn brings to the 40 wt. % Ir/NbTiO10 the resistivity of millions times lower than 40 wt.% Ir/a.TiO2 and hundreds times lower than 50 wt.% Ir/a.TiO2. Moreover, by introducing an organic framework to the synthesis, support's surface area can be enlarged and its macroporous morphology can be modified. Various ex-situ methods, e.g. HR-STEM, XRD, and RDE, are used to investigate the influence of the distribution and oxidation state of the Ir-active phase on doped TiO2 support onto the performance of catalysts, before and after the acceleration stress test (AST). And in-situ methods, including ICP-MS coupling scanning flow cell and XAS, are also applied, in order to reveal the alternating of every single component in the catalytic system during OER and after the AST. The catalyst was then tested in electrolyzer to compare its performance with the commercial Elyst Umicore Catalyst.

Reier, T.; Oezaslan, M.; Strasser, P., Electrocatalytic Oxygen Evolution Reaction (OER) on Ru, Ir, and Pt Catalysts: A Comparative Study of Nanoparticles and Bulk Materials. ACS Catalysis
2012,
2 (8), 1765-1772.

Karimi, F.; Peppley, B. A., Metal Carbide and Oxide Supports for Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Polymer-Electrolyte-Membrane Water Electrolysis. Electrochimica Acta
2017,
246, 654-670.
(Invited) Passivated Anodes in Anion-Exchange Membrane Water Electrolyzers
Authors: Kwak Minkyoung , Ojha Kasinath , Boettcher Shannon W.
Published: September 2023

Understanding and engineering the catalyst-electrolyte interface are important for many electrochemical devices. In anion exchange membrane water electrolysis (AEMWE) specifically, the durability of the system is limited by substantial oxidative ionomer degradation at the anodic potentials for oxygen evolution reaction (OER) at the anode. We understand that oxidative ionomer degradation at the anodes is due to the electron transfer from ionomer to the electrode as there is electrical contact between catalysts and ionomers. Here a thin layer of transition metal oxide coating is applied as a passivation (insulating) layer at the catalyst-ionomer interface at the anodes to suppress ionomer degradation and enhance the durability of AEMWE. We investigate the optimal thickness of the metal oxide coatings in Ir- and Co-based electrode systems and observe that the thin layer of metal oxide films on top of the catalyst layers improves the voltage degradation and protects ionomer from oxidative degradation. This work helps us understand the interaction between catalysts and ionomers and solve the durability problems in AEMWE systems using interfacial engineering.
Cooperative Fe-Sites in Nickel and Cobalt Oxyhydroxides
Authors: Twight Liam Peter , Ou Yingqing , Samanta Bipasa , Liu Lu , Biswas Santu , Fehrs Jessica L. , Caspary-Toroker Maytal , Boettcher Shannon W.
Published: September 2023

With incorporated iron, nickel and cobalt oxyhydroxides display the highest known oxygen evolution activities of any catalyst in alkaline media. To leverage this high activity in low temperature electrolysis systems, a comprehensive understanding of where Fe-based active sites form, their local chemical structure, and how this structure evolves under electrochemical conditioning is critical. Here we show that incorporation of Fe into NiOxHy and CoOxHy films during constant potential chronoamperometry yields NiFeOxHy and CoFeOxHy catalysts with extremely high TOFs of up to ~40 s-1 and 0.7 s-1, respectively, at 350 mV overpotential. Further, we discover that the TOF of these materials is linearly related to the amount of Fe incorporated with this method. We propose a mechanism involving cooperative catalysis involving multiple Fe sites to explain this linear dependence. Density functional theory calculations are used to show this cooperativity may arise from increased ability to delocalize oxidative charge in active sites comprised of neighboring FeOxHy monomers. We then show that cycling these films lowers the per-Fe TOF substantially, to a level similar to that of co-deposited NiFe and CoFe films. This loss of activity during cycling and similarity to co-deposited films in which Fe occupies intraplanar lattice sites is consistent with migration of high activity Fe clusters initially adsorbed at surface edges and defects during chronoamperometry to less active sites within the oxyhydroxide lattice via cycling-driven dynamic substrate behavior. Further evidence for this Fe relocation into bulk lattice sites is provided using the redox features of adsorbed Ni2+ and Co2+ as probes for monitoring the extent to which ions are incorporated into the bulk of NiOxHy and CoOxHy.
Reaching PEM Performance Parity with Anion Exchange Membrane Electrolyzers
Authors: Perez Bakovic Sergio Ivan , Keane Alex , Carmo Marcelo , De Porcellinis Diana
Published: September 2023

Anion exchange membrane (AEM) electrolyzers promise to combine the benefits from proton exchange membrane (PEM) electrolyzers and liquid alkaline electrolyzers. They offer both the compact stack design and high current densities that PEM electrolyzers provide, while also taking advantage of using non-platinum-group-metals (non-PGM) and titanium-free components similar to traditional alkaline electrolyzers. However, AEM stacks and systems must demonstrate competitive performance and durability to allow widespread commercial adoption.

As part of AEM development efforts, a comprehensive study has been conducted on the morphology of different porous plates and their impact on the cell performance. The key results demonstrate comparable performance of AEM electrolyzers to PEM electrolyzers under optimized conditions. Different ink formulation and processes have also been evaluated for a series of non-PGM catalysts, while testing their impact on performance and durability. In addition, commercially available AEMs have been evaluated for long term durability in short cell stacks, demonstrating comparable degradation rates to PEM electrolyzer technology.
On the Acid Stability of PGM-Free OER Catalyst for H2 Production in PEMWE
Authors: Liu Di-Jia
Published: September 2023

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, however, adds a significant cost 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.

Argonne National Laboratory has recently designed and prepared a new family of PGM-free OER catalyst for PEM electrolyzer. The new catalysts have high porosity and unique nanoarchitecture, and have demonstrated very promising activity and durability in both rotating disk electrode (RDE) and in operating PEMWE.

The most challenging aspect of PGM-free OER catalyst is its stability in the acidic media. To this end, we conducted extensive structural characterizations as well as computational modeling. Particularly, in situ X-ray absorption spectroscopy combined with high resolution imaging revealed insightful information on the electronic and surface structural changes during the electrochemical reaction. Computational Pourbaix diagram also elucidated the catalyst stability under the acidic OER operating condition.

Acknowledgement: This work is supported by U. S. Department of Energy, Hydrogen and Fuel Cell Technologies Office through Office of Energy Efficiency and Renewable Energy and by Office of Science, U.S. Department of Energy under Contract DE-AC02-06CH11357.
Enhancing Effect of Boron-Doping on the Activity of Nife-MOF-74 Towards Oxygen Evolution Reaction in Alkaline
Authors: Xing Jiale , Bliznakov Stoyan , Bonville Leonard J. , Maric Radenka
Published: September 2023

Water splitting has drawn significant attention due to the capability of mass-producing hydrogen, which is considered a promising alternative to fossil fuels in the future.[1] The development of electrochemical energy conversion and storage technologies, such as water electrolyzers, metal-air batteries, and regenerative fuel cells, is of great importance to support the transition to clean and renewable energy.[2] Based on the merits of high surface area, 3D periodic porous structure, large porosities, diverse composition and well-defined metal centers, metal–organic frameworks (MOFs) and their derivatives have been widely exploited as OER electrocatalysts.[3]However, MOFs have some limitation to be used as a OER catalysts, considering their poor stabilities (in water, especially basic/acidic conditions) and low electrical conductivities. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionalities. [4] In this work, the flower-like bimetallic NiFe-MOF-74 dopped with boron were fabricated, and they exhibit superior catalytic activity with a very low overpotential of 318 mV for OER at a laboratory grade current density of 10 to 100 mA/cm2 and fast reaction kinetics with a small Tafel slope of 89 mV dec-1 in 1.0 M KOH using a catalyst fabrication process that is scalable to commercial levels. Additional work is required to demonstrate current densities at commercial levels.

Reference

[1] L. Fan, Z. Kang, M. Li, D. Sun, Recent progress in pristine MOF-based catalysts for electrochemical hydrogen evolution, oxygen evolution and oxygen reduction, Dalton Trans. 50 (2021) 5732–5753. https://doi.org/10.1039/D1DT00302J.

[2] Bimetallic metal–organic frameworks and MOF-derived composites: Recent progress on electro- and photoelectrocatalytic applications - ScienceDirect, (n.d.). https://www.sciencedirect.com/science/article/pii/S0010854521005385 (accessed April 27, 2022).

[3] J. Du, F. Li, L. Sun, Metal–organic frameworks and their derivatives as electrocatalysts for the oxygen evolution reaction, Chem. Soc. Rev. 50 (2021) 2663–2695. https://doi.org/10.1039/D0CS01191F.

[4] Y. Xie, Z. Meng, T. Cai, W.-Q. Han, Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium–Sulfur Battery, ACS Appl. Mater. Interfaces. 7 (2015) 25202–25210. https://doi.org/10.1021/acsami.5b08129.
Investigation of Ni Foam and Stainless-Steel Mesh Substrates Toward Oxygen Evolution Reaction in Alkaline Seawater Electrolysis
Authors: Lyu Xiang , Serov Alexey , Li Jianlin
Published: September 2023

Electrolysis of alkaline seawater is a promising approach for the large-scale production of hydrogen, however, little effort has been devoted in studying the substrates for oxygen evolution reaction (OER) electrocatalysts. Stainless-steel mesh (SS mesh) and Ni foam were investigated systematically for OER in alkaline seawater electrolysis in this study. The overpotentials and Tafel slopes with SS meshes are smaller than Ni foams. Interestingly, the performance of the SS mesh even outperforms various non-noble metal electrocatalysts and is comparable to commercial RuO2 and IrO2 catalysts. Additionally, the Ni foam exhibits much poorer resistance to corrosion compared with SS meshes. This work suggests inexpensive and commercially available SS mesh is an outstanding substrate for OER in alkaline seawater electrolysis.
Transition Metal Carbides and Nitrides As Electrocatalysts for Hydrogen and Oxygen Evolution Reactions
Authors: Kang Jin Soo
Published: September 2023

Global demand to achieve carbon-neutral energy production and utilization has raised a trend of searching for a fuel that minimizes the production of CO2. From this viewpoint, hydrogen is considered as an ideal fuel as it does not contain carbon in its formula. Meanwhile, the challenge remains in the process for hydrogen production, as it is energetically up-hill and thereby produces CO2 unless a combination of renewable energy and water splitting is used.

There are a number of components that constitute a water electrolyzer, but its economic feasibility is largely challenged by noble metal electrocatalysts used for facilitation of hydrogen and oxygen evolution reactions. For this reason, significant efforts have been put to develop low-cost materials that could substitute costly catalysts. In-depth understandings on correlations between the electronic structure and the electrocatalytic activity led to the interest toward transition metal carbide and nitride materials, as they own electronic structures that mimic those of catalytic noble metals. These materials did manifest decent performances, though there are some remaining issues including the energy-intensive synthetic process.

Herein, nanostructured transition metal carbide and nitride produced by facile preparation methods are introduced. Self-supported carbides synthesized via electrochemical structuring followed by thermal carburization are applied in hydrogen evolution reaction, wherein decent catalytic activity and excellent durability are achieved. In addition, nitrides prepared at an ambient-temperature and environmentally-benign condition are utilized for oxygen evolution reaction, which manifested high performance both in terms of activity and long-term stability. Based on thorough characterization of carbides and nitrides, their physicochemical properties and electrochemical behaviors, and the relationships among them are discussed.
Layered Coaxial Nanowires Electrode (LCANE) for High Performance with Low Loading in Polymer Electrolyte Membrane Water Electrolyzer (PEMWE)
Authors: Arman Tanvir Alam , Yilmaz Abdurrahman , O. Godoy Andres , Liyanage Wipula Priya Rasika , Routkevitch Dmitri , Komini Babu Siddharth , Jankovic Jasna , Pasaogullari Ugur , Spendelow Jacob S.
Published: September 2023

Polymer electrolyte membrane water electrolyzer (PEMWE) could play a key role in green hydrogen production from intermittent renewable energy sources, yet, the high loading of scarce precious metals hinders widespread commercialization. Innovative electrode designs that decrease the precious metal loading while maintaining high performance can be a significant step forward for the quicker adoption of hydrogen-based energy storage systems. Herein, we report a novel Layered Coaxial Nanowire Electrode (LCANE) composed of ionomer nanowires encapsulated by IrO2-decorated Pt nanofilms, which enables increased hydrogen production with decreased catalyst loading. By combining atomic layer deposition of Pt, ultrasonic spray of IrO2, and nano-extrusion of ionomer, the LCANE architecture enables improved in-plane conductivity, faster transport, and less agglomeration of catalyst. With a fraction of loading compared to conventional electrodes, LCANE demonstrates a promising way to decrease the loading of the PEMWE anode.

Figure 1
Titanium Nitride (TiN) Micro-Porous Layers for Unitized Reversible Fuel Cell and Water Electrolyzers
Authors: Yilmaz Abdurrahman , Komini Babu Siddharth , Pasaogullari Ugur , Spendelow Jacob S.
Published: September 2023

Unitized reversible fuel cells combine power generation (fuel cell) and fuel and oxidant generation (water electrolyzers) in a single device. Compared to discrete systems, the URFC is more advantageous in terms of mass, volume, and cost. The conflicting requirements of the two different operational modes introduces several technical challenges to make URFCs competitive with other energy storage technologies. One of the most challenging problems is the wettability requirements of the PTL in the oxygen electrode. The fuel generation (water electrolyzer) mode requires fast water transport to the catalyst layer (CL), while the power generation (fuel cell) mode requires the discharge of the by-product water from the PTL to enable effective oxygen transport to the CL. We have previously demonstrated three different nanopowders for fabricating micro-porous layers (MPLs), which provide significant performance improvement in both operational modes. In this work, we report further improvement of the TiN MPL by optimizing the thickness and wettability and coating on the untreated and wetproofed substrate (i.e., titanium felt) for enhancing oxygen transport and water transport in both operational modes. The results are presented for the characterization, cell testing performance, and durability of TiN MPL coated on titanium fiber substrates.

Acknowledgment: Financial support from the US Department of Energy through the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cells Technology Office is gratefully acknowledged.