bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Sites for ORR on Pt in PEM Fuel Cells: A DFT Perspective
Authors: Zeng Zhenhua
Published: December 2024

For ORR on Pt, the classic model categorizes active sites based on surface motifs, such as terraces and steps. However, this simplistic approach often leads to orders of magnitude errors in catalyst activity predictions and qualitative uncertainties of active sites, thus limiting opportunities for catalyst design. Using stepped Pt(111) surfaces and ORR as examples, we will illustrate that the root cause of larger errors and uncertainties is such a simplified categorization overlooks atomic site-specific reactivity driven by surface stress release. Specifically, we will show how surface stress release at steps introduces inhomogeneous strain fields, resulting in distinct electronic structures and reactivity for terrace atoms with identical local coordination. This phenomenon leads to a cluster of active sites flanking both sides of the step edge. We will demonstrate strategies to enhance ORR activity in low temperature (<100 °C) PEM fuel cells by leveraging this effect, such as varying terrace widths,[1] adjusting the thickness of 2D nanosheets[2] or controlling external stress.[3]

For ORR in high tempatature (>100°C) PEM fuel cells, we found that, in contrast to ORR under hydrous conditions, (111) terrace sites are not active for ORR under anhydrous conditions, because of weakened binding of ORR intermediates induced by O* accumulation on the surface. On the other hand, step edges, which are generally not active for ORR under hydrous conditions, are predicted to be the active sites for ORR under anhydrous conditions. Among them, (110) type step edge with a unique configuration of accumulated O stabilizes O2 adsorption and facilitates O2 dissociation, which lead an overpotential <0.4 V. To improve ORR catalysts in high‐temperature PEMFCs, it is desirable to maximize (110) step edge sites that present between two (111) facets of nanoparticles.[4]

[1] G. Liu, A. J. Shih, H. Deng, K. Ojha, X. Chen, M. Luo, I. T. McCrum, M. T. M. Koper, J. Greeley, Z. Zeng, Nature
2024, 626, 1005-1010.

[2] L. Wang, Z. Zeng, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley, Science
2019, 363, 870-874.

[3] K. J. Sawant, Z. Zeng, J. P. Greeley, Angew. Chem., Int. Ed.
2024, 63, e202312747.

[4] G. Liu, H. Deng, J. Greeley, Z. Zeng, Chinese Journal of Catalysis
2022, 43, 3126-3133.
Mechanistic Insights into the Formation and Growth of Supported Metal Nanoparticles By an Identical-Location Synthesis Approach
Authors: Seidl Lisa Maria , Hu Yang , Li Qingfeng
Published: December 2024

Electrocatalysts are key materials for the development of a wide range of renewable energy technologies, such as fuel cells, electrolyzers, and P2X devices. Often the best catalysts in terms of the activity and stability take the form of well-dispersed precious metal particles supported on a highly durable and conductive substrate. In particular, for high-temperature proton-exchange membrane fuel cells, the anode catalyst most desired by the industry is Pt-based nanoparticles of 4-5 nm with a high metal loading (e.g. 50 wt%) well dispersed on a graphitized carbon support. Unfortunately, synthesis of such catalysts on a sufficiently large scale has rarely been achieved.

Recently, our group has developed a solid-state chemical process for the synthesis of supported electrocatalysts.1, 2 Regarding the particle formation mechanism, the classical nucleation theory provides a fundamental basis for understanding the synthesis process, but it is insufficient to predict the detailed mechanism when synthesis precursors of specific structures are involved. Herein, we report our recent progress in understanding the key processes governing the formation and growth of Pt nanoparticles on different carbon supports, through investigations using an identical-location synthesis approach. Figure 1 shows the TEM images of a synthesis precursor before and after the reduction step. Based on the insights gained, we have attempted to synthesize the much-anticipated catalyst, graphitized carbon supported Pt-based nanoparticles. We believe that the mechanistic insights obtained and the syntheses demonstrated will provide important guidance for the synthesis of various types of supported catalysts. Furthermore, we expect this method to be suitable for the synthesis of catalysts on a larger scale.

References:

Y. Hu; Jensen, J. O.; Norby, P.; Cleemann, L. N.; Yang, F.; Li, Q., Mechanistic Insights into the Synthesis of Platinum–Rare Earth Metal Nanoalloys by a Solid-State Chemical Route. Chemistry of Materials
2021,
33 (2), 535-546.

Y. Hu; Jensen, J. O.; Cleemann, L. N.; Brandes, B. A.; Li, Q., Synthesis of Pt–Rare Earth Metal Nanoalloys. Journal of the American Chemical Society
2020,
142 (2), 953-961.

Figure 1: IL-TEM images of the synthesis precursors before (left) and after (right) of the high-temperature reduction.

Figure 1
Durability of Highly Active PGM Catalyst MEA Tested Via Nitrogen and Air AST Cycling Under HDV Condition
Authors: Zhu Guangqi , Zhang Hannah , Yu Haoran , Cullen David A. , Jeon Sungho , Ortiz Erika , Stach Eric A. , Marina Oana C. , Li Zheng-Hua , Xie Jian
Published: December 2024

Polymer electrolyte membrane fuel cells (PEMFCs) have emerged as leading power source candidates for electric vehicles due to their ultimate cleanness, high efficiency and rapid refueling capabilities. Their ability to facilitate fast refueling with minimal dead mass penalty, unlike Li-ion batteries, positions fuel cells as ideal power plants for heavy-duty vehicles (HDVs) such as electric long-haul trucks, coaches, ships and airplanes, each with unique drive cycles and operational requirements. These applications demand catalyst, ionomer and membrane with enhanced durability compared to light duty vehicles (LDVs). In addition, PEMFCs operating with pure oxygen exhibit superior performance and efficiency but may face heightened challenges regarding durability of membrane electrode assembly (MEA). Presently, catalyst and MEA stability are evaluated for durability using the protocol of accelerated stress test (AST) under hydrogen/nitrogen (anode/cathode) atmosphere. Comparing with nitrogen atmosphere, the air will exert more significant degradation on both catalysts and ionomer/membranes. However, the impact of hydrogen/air condition, particularly under HDV operating conditions, on catalyst, ionomer, membrane degradation and their differences from the hydrogen/nitrogen condition remains unclearly understood. In this work, two MEAs fabricated by our highly active catalysts, specifically 30wt% Pt/KB, as the cathode and a commercial Pt/C catalyst as the anode. These MEAs underwent testing under HDV conditions (250 kPa back pressure) at various relative humilities, following the standard protocol of accelerated stress test (AST) in hydrogen/nitrogen and hydrogen/air (M2FCT) for 180k cycles. The results indicate substantial performance degradation in both MEAs during AST cycling. MEAs subjected to AST in hydrogen/nitrogen maintained the current density of 1.4 A/cm2, 1.2 A/cm2, 1.0 A/cm2 and 0.9 A/cm2 at the cell voltage of 0.7 V after the AST of 30k, 60k, 90k and 120k cycles, respectively. Moreover, the hydrogen/nitrogen MEA performance significantly declined to 0.5 A/cm2 and 0.3 A/cm2 at the same voltage after 150k and 180k cycles, respectively. In comparison, the MEA tested with AST in hydrogen/air exhibit similar beginning-of-life performance but experienced faster performance loss, especially within the mass transfer region, accompanied with the significant increase in crossover current, which indicates the degradation of membrane. In summary, this study elucidates the distinct degradation and mechanisms observed in highly efficient and durable PGM-catalyst MEAs running AST in nitrogen and air under HDV conditions.
Dihydroxyl Additives for Enhancing Activity and Durability of Pt/C Catalysts.
Authors: Agarwal Tanya , Komini Babu Siddharth , Li Kui , Borup Rod L.
Published: December 2024

Fuel cells are especially attractive as a decarbonization strategy for heavy duty transportation sector. However, the durability and cost of the fuel cell components remains a major barrier for market penetration. Expensive platinum based catalysts, represent a significant portion of this challenge. Therefore, effort to enhance their durability and performance, without increasing the loading, could make a significant advancement towards commercial viability. In this study, we investigated the incorporation of dihydroxyl additive, ellagic acid (EA), in cathode catalyst layers to improve the performance and durability of the catalysts. Our observation revealed that incorporation of EA into cathode catalyst layer led to an increase in mass activity when used with a Pt catalyst supported on either vulcan and high surface area (HSC) carbon support. Increase in the overall conductivity of the catalyst layers due to the hydrophilic nature of the additive could be responsible for improved performance. Decrease in the catalyst activity inhibition by the ionomer adsorption of the platinum surfaces could also result in improved catalytic activity.

Further increase in mass activity with the HSC can be achieved by the optimizing the solvent used for ink preparation for enhanced interaction of EA with the platinum inside the pores and not just the surface platinum particles. We also find enhanced durability of both Pt/Vulcan and Pt/HSC catalyst with the chosen additive in accelerated stress tests. The probable reasons for this behavior will be discussed.

Acknowledgement

This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos.
Thin Film Electrocatalysts on Extended Surface Supports for the Oxygen Reduction Reaction
Authors: Chiu Chan-Wen , Bhattacharya Deepra , Mohney Suzanne E. , Arges Christopher
Published: December 2024

The world is urgently looking to increase the amount of renewable energy power generation and reduce carbon emissions. Proton exchange membrane water electrolyzers (PEMWE) and fuel cells (PEMFC) play important roles in energy storage and help leveling the renewable power generation. Platinum group metals (PGMs) are popular catalysts used in PEMWE and PEMFC. However, the cost of PGMs hinders the widespread adoption of these two devices and slows down the progress of decarbonizing industrial sectors. In this talk, the oxygen reduction reaction (ORR) performance of platinum (Pt) catalysts, fabricated via different thin film deposition technologies will be compared to Pt catalysts prepared via traditional incipient wetness impregnation (IWI). Pt catalysts fabricated via thin film deposition technology, such as e-beam evaporation, sputtering, and atomic layer deposition (ALD), demonstrate higher mass activity and electrochemical surface area (ECSA) compared to Pt catalysts fabricated using IWI. This result points out the possible option to make PEMFC and PEMWE more affordable and provides alternate methods for researchers to finely control the loading of the Pt in device electrodes.
Ultrahigh Loading of Copper Single Atoms through Pyrolysis of Nitrogen-Doped Graphene Quantum Dots for Oxygen Reduction Reaction
Authors: Kim Doo Young , Perera Shashika , Sharma Prakhar , Thisera Ayanthi , Guiton Beth S.
Published: December 2024

Major bottlenecks against the widespread utilization of proton-exchange-membrane fuel cells are (i) the sluggish kinetics of oxygen reduction reaction (ORR) and (ii) economic viability associated with the extensive use of Pt group metal (PGM) catalysts,. Therefore, non-PGM single-atom catalysts (SACs) have received a considerable attention as alternatives to PGM catalysts for ORR. In this presentation, we will share our recent studies that investigate the synthesis and characterization of copper single atom catalysts (Cu-SACs) for ORR. Ultrahigh loading (10 – 40 wt%) of Cu-SACs was achieved through a simple pyrolysis of nitrogen-doped graphene quantum dots derived from small organic molecules like pyrene and citric acid. Graphene quantum dots have abundant functional groups, facilitating the incorporation of nitrogen and Cu single atoms during pyrolysis. Abundant nitrogen sites (pyridinic-N and pyrrolic-N) effectively chelated Cu atoms by forming Cu-N complexes (Cu-Nx). The effects of Cu loading and pyrolysis temperature on ORR activities were investigated. Interestingly, after the removal of co-synthesized metallic Cu by acid-washing, Cu-SAC demonstrated a noticeable enhancement of ORR activity with 4-electron transfer pathway. High-resolution scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS) and electrochemical characterization results will be presented. This bottom-up approach of utilizing graphene quantum dots demonstrates promise for developing high-density, non-PGM-based SAC sites for efficient and economically viable electrocatalysis.
Expanding the Scope of ZIF-Derived Carbons Towards Tailored Architectures and Compositions
Authors: Pappas Nina , Ojo Alaba Upe , Chen Kate , Dolgopolova Ekaterina , Wang Xiaojing , Spendelow Jacob S.
Published: December 2024

Proton exchange membrane fuel cells (PEMFCs) represent a promising technology for clean energy conversion. The key chemical transformation within a fuel cell is conducted by catalyst nanoparticles tethered to a carbon support. Although the carbon support plays a critical role in maximizing the performance and durability of the catalyst nanoparticles and mass transport, predictably tuning the chemical environment and pore architecture of the carbon support remains a challenge. Metal–organic frameworks are a class of crystalline porous coordination polymers known for their structural and chemical tunability. Recently, metal–organic frameworks (MOFs), almost exclusively zeolitic imidazolate framework-8 (ZIF-8), have been used as precursors to generate carbon supports where the MOF architecture serves as a template to generate the carbon skeleton. As a result, these materials have an improved homogeneous porous landscape and, encouragingly, superior PEMFCs performance and durability. Herein, we leverage the vast library of MOFs and report design principles for generating precisely tuned carbon support architectures through systematic changes to the structure and chemical composition of MOFs. Advanced fuel cell testing of PEMFCs featuring these novel carbon architectures offers fine level insight into the effects of pore size, connectivity and chemistry on the performance of PEMFCs.

Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.
Advanced ORR Catalysts Based on Intermetallic Nanoparticles and Metal-Organic Frameworks
Authors: Chen Kate , Li Kui , Wang Xiaojing , Wu Gang , Spendelow Jacob S.
Published: December 2024

Metal-organic frameworks (MOFs) based catalysts are emerging as highly promising enablers for high-performance and durable fuel cells. Our novel PtCo catalyst, supported by porous carbon derived from the pyrolysis of zeolitic imidazolate framework-8 (ZIF-8), dubbed PtCo/ZIF8, demonstrates superior performance and robustness during fuel cell operations. Tested under the Million Mile Fuel Cell Truck Consortium (M2FCT) conditions—250 kPa, 85% relative humidity, 90 °C cell temperature, and 15% oxygen—the PtCo/CZIF8 consistently outperformed commercial catalysts at critical operating voltages of 0.7 V and above. Notably, it achieved a current density of 1.43 A/cm2 at 0.7 V after enduring 90,000 accelerated stress test (AST) cycles, surpassing the M2FCT's end-of-life target of over 1.07 A/cm2. Furthermore, the catalyst showed a high mass activity of 0.87 A/mgPt initially, which only declined to 0.59 A/mgPt by the end-of-life test , indicating a 32% loss. In terms of electrochemical surface area (ECSA), the PtCo/CZIF8 maintained about 64% of its initial ECSA after the 90,000 AST cycles, well within the M2FCT’s protocol of less than 40% ECSA loss1. These results establish MOF-based catalysts as front-runners for fuel cell commercialization and are crucial for global efforts to reduce greenhouse gas emissions.

Acknowledgement:

This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

References:

1.https://millionmilefuelcelltruck.org/ast-protocols
Potential Cycling Test of High Temperature PEMFC Based on Acid Doped Polybenzimidazole Membranes
Authors: Celenk Sanser , Cleemann Lars Nilausen , Jensen Jens Oluf , Li Qingfeng
Published: December 2024

The performance degradation of HT-PEMFC is studied by potential cycling at 160 oC. The membrane-electrode-assemblies are made of acid-doped polybenzimidazole membranes and PtCox catalysts on the cathode. While the upper potential limit is fixed at 0.95 V the degradation is stressed by varying the low-end potential from 0.8 to 0.65 V and hold duration from 5 to 60 sec. During the cycling tests, little degradation of the membrane, in terms of ohmic resistance and open circuit voltage is observed but a significant performance loss is attributable to the mass transport due to the degradation of the electrode hydrophobicity. A major catalyst degradation mechanism is the platinum particle growth via the electrochemical Ostwald ripening. No evidence of the cathode dealloying was detected during the potential cycling. The dissolution of platinum or the surface oxides of platinum during the upper potential hold at 0.95 V seems limited by the available acid in the electrolyte membrane. The low-end potential and the hold duration seem critical where the reduction and re-deposition of platinum occur, leading to formation of larger particles and hence loss of the active surface area.
Integrating Machine Learning for Colloidal Synthesis of Spinel Oxide Nanocrystals
Authors: Wang Xin , Bundschu Colin , Rowell Jonathan L. , Arias Tomas A. , Robinson Richard D. , Frazier Peter , Abruna Hector D.
Published: December 2024

The synthesis of spinel oxide nanocrystals is gaining momentum due to their broad applicability in energy storage and conversion technologies, including supercapacitors, lithium-ion batteries, and electrocatalysis for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The performance of these spinel nanomaterials depends on their intrinsic physical properties, such as electronic conductivity and the interaction with reaction intermediates, which are, in turn, influenced by particle size and morphology. These dependencies arise from effects such as quantum confinement and surface or lattice strain, highlighting the importance of producing nanocrystals with controlled size and low dispersity for precise property-application correlations. Achieving such control is crucial for tailoring material properties to specific applications. Colloidal synthesis emerges as a promising method, offering the precision to generate small, monodisperse nanocrystals in a scalable manner. The complexity of colloidal synthesis, dictated by factors such as precursor species, ligands, temperature and solvents, makes synthetic optimization of nanocrystals with precise crystallographic phase and composition both time-consuming and labor-intensive. This leads us to integrate machine learning to efficiently explore and optimize this vast parameter space. By leveraging historical data and employing iterative learning, we aim to automate reaction route optimization in colloidal synthesis. This approach not only enhances synthesis efficiency and material performance for energy applications but also enables the tailored development of nanomaterials through data-driven predictions and streamlined processes.
Dopant Modulated, Surface Restructured NixCo1-XSy Electrocatalysts for Oer in Alkaline Condition
Authors: Feng Zhenxing
Published: December 2024

The search of efficient and stable electrocatalysts for oxygen evolution reaction (OER) in alkaline electrolytes is the key to enable the commercialization of alkaline electrolyzers and lower hydrogen production price. However, there is a trade-off relation between the activity and stability of electrocatalysts due to the highly oxidative condition of OER, which induces the surface restructuring for electrocatalysts. Our recent work show that by modulating the composition of electrocatalysts for (Co, Ni)Sy anchored on carbon nanofibers, we can control the stability of electrocatalysts and optimize their activity in alkaline OER. Using electron microscopy and X-ray spectroscopy characterizations including X-ray absorption spectroscopy and X-ray photoelectron spectroscopy, we reveal the restructuring mechanism, which can help us break down the activity-stability trade-off relation to design and scale up such electrocatalysts for commercial applications.
Perovskites As Oxygen Evolution Reaction Catalysts for Alkaline Electrolysis: A Stable Alternative?
Authors: Buchauer Fabian Luca , Simonsen Soren Bredmose , Chatzichristodoulou Christodoulos
Published: December 2024

The sluggish nature of the Oxygen Evolution Reaction (OER) is responsible for a large efficiency penalty in alkaline electrolysis (AEL), with intensive research targeting more active and stable catalysts. Catalyst testing is typically carried out in RDE setups under mild conditions. Such tests are useful for evaluating the catalytic activity, but the results are seldom inter-comparable due to differences in electrode fabrication, microstructure, catalyst surface area, and test conditions. Furthermore, the material activity and stability at mild conditions does not represent the one at industrial conditions. Thus, testing the materials at industrial application conditions is crucial, i.e. at higher temperatures, e.g. 60-100°C, at concentrated KOH, e.g. 6-10M, and for longer times.

Perovskites are an exciting group of materials as OER catalysts due to their reported high catalytic activities [1], and their tunable properties, allowing ample room for optimization and use of abundant elements. Even though many studies report the stability of perovskites under mild conditions and for durations of up to 2000h [2], the stability at industrial conditions is still in question. In this study, we tested the catalytic activity of La-based perovskites and others at industrial conditions. For better comparability, the tests are carried out on dense and polished pelettes with a well-defined surface area. Post-mortem analysis shows that the most researched materials are unstable at industrial conditions. However, one candidate showed excellent stability far beyond the commercial operation window, with only minor signs of degradation after 200h at 150°C, while possessing excellent intrinsic activity, with an overpotential of 240mV at 10mA/cm2
ECSA.

Furthermore, perovskites are an excellent host for exsolution, which is the partial decomposition of the host material to form well-dispersed and anchored nanoparticles on the surface of the host. We have used the exsolution process to enhance the catalytic activity even further, and short-term stability tests confirm the presence of the exsolved particles after several hours of operation at industrial conditions. To the best of our knowledge, this study shows the first report of exsolved catalysts under industrial operating conditions.

[1] Liu, L. B., Yi, C., Mi, H. C., Zhang, S. L., Fu, X. Z., Luo, J. L., & Liu, S. (2024). Perovskite Oxides Toward Oxygen Evolution Reaction: Intellectual Design Strategies, Properties and Perspectives. In Electrochemical Energy Reviews (Vol. 7, Issue 1). Springer Nature Singapore. https://doi.org/10.1007/s41918-023-00209-2

[2] Jo, H., Yang, Y., Seong, A., Jeong, D., Kim, J., Joo, S. H., Kim, Y. J., Zhang, L., Liu, Z., Wang, J. Q., Kwak, S. K., & Kim, G. (2022). Promotion of the oxygen evolution reaction: Via the reconstructed active phase of perovskite oxide. Journal of Materials Chemistry A, 10(5), 2271–2279.

Figure 1
Enhanced Activity and Stability via Fe Substitution in Lithium Nickel-Based Electrocatalyst for Oxygen Evolution Reaction in Alkaline Media
Authors: Jung Younghan , Tamboli Asiya M. , KIM Wan Sik , Im Sejin , Sim Junseok , OH JunSeok , Kim Chang-Hee
Published: December 2024

The oxygen evolution reaction (OER) is kinetically sluggish and requires a high overpotential compared to the hydrogen evolution reaction (HER) due to its four-electron transfer process. Herein, we have fabricated highly active Fe-substituted LiNiO2 using the electrostatic spray deposition (ESD) technique as scalable electrocatalysts. With this technique, we can modify the electronic and surface structure of LiNixFe1-xO2 by controlling the amounts of Ni and Fe, where x = 0, 0.2, 0.4, 0.6, and 0.8. This substitution can modify the electronic structure of the Ni ions to more electrophilic oxidation states, resulting in the M – O step facilitation, which is considered one of the rate-determining steps in the OER. The electronic structure modification was characterized by X-ray photoelectron spectroscopy (XPS). The surface structural modulation of the electrocatalysts due to Fe substitution was analyzed by scanning electron microscopy (SEM). The OER half-cell electrochemical measurements were carried out using standard three- electrode configuration. These results elucidate that substitution of Ni by Fe increases the electrocatalytic activity significantly. The optimized electrocatalyst, LiNi0.6Fe0.4O2, exhibits an overpotential of 239 mV at a current density of 10 mA cm-2 and a Tafel slope of 41.49 mV dec-1. Moreover, it exhibits excellent operational durability under continuous and dynamic operating environments without any significant performance degradation.
Monometallic, Bimetallic, and Trimetallic Oxyphosphides for OER Catalysis in Alkaline Electrolyte
Authors: Onajah Sammy , Lalley Marja , Kreider Melissa E , Alia Shaun M , Yu Haoran , Myers Deborah J. , Farghaly Ahmed A.
Published: December 2024

The development of efficient and durable catalysts for the kinetically sluggish oxygen evolution reaction (OER) is paramount for advancing various electrochemical processes including water splitting, CO2 electroreduction, and metal air batteries. In this presentation, the synthesis, characterization, and electrochemical evaluation of monometallic, bimetallic, and trimetallic transition metal OER catalysts will be discussed. We employed a colloidal synthesis approach to fabricate mesoporous oxyphosphide catalysts with varying compositions. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization revealed the formation of a distinct core@shell structure comprising a zero-valent metallic core enveloped by a porous oxygen-rich shell. An OER potential of <1.5 V versus RHE at 10 mA cm-2 and a low Tafel slope of 32 mV decade-1 were measured, surpassing other catalyst configurations including commercial platinum-group-metal-free (PGM-free) catalysts in alkaline media. Furthermore, excellent OER durability at 10 mA cm-2 was demonstrated, with a potential increase of <0.5 mV/h after 100 hours of testing. These findings underscore the potential of TM oxyphosphide catalysts as promising candidates for efficient and durable OER electrocatalysts, paving the way for sustainable energy conversion and storage technologies.

Acknowledgments

This 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.

Khalafallah D, Farghaly AA, Ouyang C, Huang W, Hong Z. Atomically dispersed Pt single sites and nanoengineered structural defects enable a high electrocatalytic activity and durability for hydrogen evolution reaction and overall urea electrolysis. Journal of Power Sources. 2023, 558, 232563.

Onajah S, Sarkar R, Islam MS, Lalley M, Khan K, Demir M, Abdelhamid HN, Farghaly AA. Silica‐Derived Nanostructured Electrode Materials for ORR, OER, HER, CO2RR Electrocatalysis, and Energy Storage Applications: A Review. The Chemical Record. 2024, e202300234.

Sarkar R, Farghaly AA, Arachchige IU. Oxidative Self-Assembly of Au/Ag/Pt Alloy Nanoparticles into High-Surface Area, Mesoporous, and Conductive Aerogels for Methanol Electro-oxidation. Chemistry of Materials. 2022, 34(13), 5874-87.
Accelerated Durability Tests of Electrostatic Spray Deposited NiFe2O4 for Renewable Energy-Powered Alkaline Water Electrolyzers
Authors: Tamboli Asiya M. , Jung Younghan , OH JunSeok , Kim Wan Sik , Sim Junseok , IM Sejin , Kim Changhee
Published: December 2024

Hydrogen production by water electrolysis is of utmost significance for a clean, renewable and carbon neutral energy economy. Specifically, the integration of water electrolysis systems with renewable energy sources (RES) shows great potential. A key obstacle for RES-powered water electrolysis technology is the incorporation of intermittent and unpredictable energy production, due to which constrains stable operation of water electrolyzer resulting in the electrode degradation of OER electrocatalysts. Herein, NiFe2O4 electrocatalyst was fabricated using simple and scalable electrostatic spray deposition technique. To evaluate robustness as OER electrode, the operational durability tests were carried out under three harsh dynamic operating regimes (i.e., constant, transient, and on-off). The electrode showed remarkable durability under steady state operation at constant applied voltage vs RHE and On-Off condition for about 24 hours. Furthermore, alterations in morphology and electrocatalytic performance were comprehensively investigated through the utilization of X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) measurements.
Discovering the Catalytic Role of Interfacial Water Towards Hydrogen Evolution/Oxidation Reactions in Aqueous Solutions
Authors: Liu Ershuai , Qin Xueping , Delmo Ernest Pahuyo , Shao Minhua , Vegge Tejs , Drisdell Walter S.
Published: December 2024

Abstract

Despite significant research efforts, the sluggish kinetics of the hydrogen evolution and oxidation reactions (HER/HOR) on Pt in alkaline solutions remain poorly understood. The role of interfacial water molecules has been investigated in recent years, yet several questions persist. These include a clear definition of interfacial water molecules, their distinction from bulk or hydrated water, and their specific mechanism of action in HER/HOR processes. Addressing these questions is critical for unraveling the HER/HOR interface and will inform the development of next-generation catalysts for green hydrogen. Herein, we explore the HER/HOR kinetics of various catalysts, including monometallic (Pt, Ru, Pd) and bimetallic (Pt-Ru) systems, in alkaline electrolytes (AMOH, where AM represents alkali metal cations) at different pH levels. Our findings indicate that HER/HOR kinetics are consistently slower in 0.01M AMOH (pH 12) than in 0.1M AMOH (pH 13), a trend that current pH-based theories do not explain. Using high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) and attenuated total reflectance-surface enhanced infrared adsorption spectroscopy (ATR-SEIRAS), we identified two distinct behaviors of interfacial water across the catalysts. In dilute electrolytes (0.01M), the interfacial water demonstrates reduced flexibility, hindering the transport of HER/HOR intermediates. Conversely, in concentrated electrolytes (0.1M), interfacial water supports the HER/HOR process via a bifunctional pathway and obey the hard-soft acid-base (HASB) interaction. Slow-growth sampling coupled with ab initio molecular dynamics (SG-AIMD) simulations corroborate that the hydrogen bonding network in 0.01M electrolyte is less conducive to reactivity compared to that in 0.1M electrolyte. Our results aid existing theories and provide new insights into the fundamental mechanisms of alkaline HER/HOR catalysis.

Acknowledgement

The authors thank the funding source from Liquid Sunlight Alliance under the U.S. DOE, Office of Science, Office of Basic Energy Sciences, Fuels Award Number DE-SC0021266 and the Laboratory Directed Research and Development Program of the Lawrence Berkeley National Laboratory under the U.S. DOE Contract No. DE-AC02-05CH11231. This research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704.
High Entropy Alloys Insights for Electrochemical Water Splitting
Authors: Campos Mata Maria Astrid , Roy Soumyabrata , Ajayan Pulickel M.
Published: December 2024

High Entropy Alloys (HEAs) constitute a novel class of materials characterized by the homogeneous integration of five or more metallic elements. They have grabbed the attention due to their unique properties and the multi-dimensional compositional space that can be tuned in many ways. However, the interaction between each of the metals in these HEAs hasn’t been studied sufficiently, impeding a comprehensive understanding of their roles and potential applications. In this work we studied the electrocatalytic activity and mechanism of HEA for Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER) in alkaline media. Our results demonstrate that these alloys outperform conventional catalysts, exhibiting lower overpotentials and higher current densities than standard materials such as RuO2 for OER. To understand the mechanism and electrochemical behavior of HEAs of these materials, we analyze the materials before and after electrochemical studies by Scanning Electron Microscopy (SEM), Transition Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). Additionally, Density Functional Theory (DFT) calculations are provided to elucidate the contributions of constituent metals to the electrochemical processes. This study contributes to the fundamental understanding and potential applications of HEAs as efficient electrocatalysts, thus facilitating their utilization in diverse energy conversion and storage technologies.
Multiscale Modeling of Heterogeneous Interfaces for Hydrogen Production
Authors: Pham Anh Tuan , Kwon Hyuna , Zagalskaya Alexandra , Calegari Marcos , Ogitsu Tadashi
Published: December 2024

Improving performance of hydrogen production devices requires a detailed understanding of physicochemical processes at solid-gas and solid-liquid interfaces. However, probing behavior of these interfaces under working conditions remain a significant challenge for both simulations and experimental probes. In this talk, I will provide an overview of our strategy for simulating heterogeneous interfaces within the HydroGEN Advanced Water Splitting Materials Consortium, ranging from first-principles calculations of chemical reactivity to machine learning approaches for accelerating theory-experiment integration and continuum methods for understanding microstructure effects. In particular, I will discuss how computational models can be used to elucidate mechanisms of interface chemical reactions and mass transport, as well as the formation of new phases and their impacts on materials stability and performance. I will also show how simulations have been integrated with experimental probes, such as X-ray spectroscopy, to obtain new understanding of materials interfaces under operating conditions. Finally, I will discuss how this understanding is being used to guide new strategies for improving materials functionality for hydrogen production.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Strengthening Ru−O Bonds with Co and Mn Dopants for Robust Oxygen Evolution in Acid Media
Authors: Wang Lei
Published: December 2024

The development of cost-effective and acid-stable oxygen evolution reaction (OER) electrocatalysts to replace iridium-based catalysts is essential for the implementation of proton exchange membrane (PEM)-based water electrolysis at gird scale. While ruthenium (Ru) oxide is highly efficient in acidic environments, severe Ru dissolution, caused by the formation of highly oxidized RuO4 species, hinders its adoption. Herein, we develop a catalyst composite consisting of RuO2 skin deposited on a manganese-cobalt-spinel oxide (MnCo2O4.5) substrate, which demonstrates high active and stability towards acidic OER. Specifically, the optimized Ru/MnCo2O4.5 catalyst exhibits a low overpotential of 210 mV at 10 mA cm−
2 and outstanding stability with negligible degradation rate under practical conditions. When integrated into a PEM electrolyser as the anode catalyst, Ru/MnCo2O4.5 achieves an encouragingly low cell voltage of 1.83 V to reach 1 A cm−2. Moreover, the PEM electrolyser demonstrates stable operation at 1 A cm−2 for over 130 h. Additionally, we conducted pH-dependent and kinetic isotope experiments to probe the rate-determining steps under varying reaction conditions. Our findings demonstrate that Ru/MnCoO4.5 exhibits similar, if not improved, OER activity in acidic electrolyte compared to that in alkaline electrolyte. Finally, density functional theory calculations revealed that the incorporation of Co and Mn foreign atoms enhances the OER activity of RuO2 and stabilizes the RuO2 against dissolution by hindering its overoxidation into soluble RuO4 species.
Engineered Porous Transport Electrode for Proton Exchange Membrane Water Electrolysers
Authors: Sidney Santana Cássia , Bens Frennie , Shen Jie , Dijk Bas , Diaz-Morales Oscar
Published: December 2024

Proton Exchange Membrane Water Electrolysers (PEMWEs) is among the most promising approaches for green hydrogen production due to its rapid response times and high-power density operation, which make this electrolysis technology well-suited to harvest the intermittent power from wind and solar plants. Nevertheless, the commercial breakthrough of PEMWE technology continues to face barriers due to its costs [1]. The porous transport layer (PTL) is one of the PEMWE components that facilitates the transport of incoming water to the catalyst layer and the removal of the product gases, hence it is very important for good electrolyser performance. The state-of-the-art PTLs are manufactured by high temperature sintering of titanium fibers or powders, which can generate oxidized surfaces that will reduce PEMWE performance. Furthermore, titanium is listed by the European Union as a critical raw material since 2020 [2], so it is advisable to reduce the amounts of its use to produce PTLs. Additionally, the (micro)structure of state-of-the-art PTLs is not optimized for efficient liquid and gas transport in electrolysis. The manufacturing process plays a key role in achieving PTLs with optimized liquid and gas transport as well as reducing the usage of titanium.

In this work, we used lithography to manufacture PTLs in which the (micro-)structure can be optimized and the usage of titanium metal can be significantly reduced. The lithography manufactured PTLs were used as substrates to produce catalyst-coated electrodes (CCE) with (ultra-)low loadings of iridium and the PEMWE performance was evaluated, respect to CCEs manufactured on commercial PTLs. We demonstrate similar performance of the CCEs manufactured with the engineered PTL, with the advantage of using less titanium and being able to tune the (micro-)structure of the component.

References:

[1] Babic, U., Suermann, M., Büchi, F. N., Gubler, L., & Schmidt, T. J. (2017). Critical review - identifying critical gaps for polymer electrolyte water electrolysis development. Journal of The Electrochemical Society, 164(4), F387.

[2] European Commission, Directorate-General for Internal Market, Industry, Entrepreneurship and SMEs, Blengini, G., El Latunussa, C., Eynard, U. et al., Study on the EU's list of critical raw materials (2020) – Final report, Publications Office of the European Union, 2020, https://data.europa.eu/doi/10.2873/11619

Figure 1
Design of Highly Dispersed Pt Entities on Mesoporous N-Doped Carbon Nanospheres – Improving Pt Utilization for Hydrogen Evolution
Authors: Küspert Sven , Campbell Ian E. , Zeng Zhiqiang , Balaghi S. Esmael , Ortlieb Niklas , Thomann Ralf , Knäbbeler-Buß Markus , Allen Christopher S. , Mohney Suzanne E. , Fischer Anna
Published: December 2024

Considering the global and growing technological demand for platinum, increasing its utilization is key in the context of green hydrogen production by proton exchange membrane water electrolysis. An effective strategy to increase Platinum utilization in Pt/C hydrogen evolution electrocatalysts is to increase the Pt dispersion on the conductive carbon support and to reduce the Pt nanoparticle size down to Pt clusters or even Pt single sites. In that context utilization of 3D porous N-doped carbon supports is helpful to form and stabilize highly dispersed Pt species and achieve high mass activities.

In here we present two approaches for the synthesis of such electrocatalysts with high Pt dispersion for hydrogen evolution: one based on a simple wet impregnation with subsequent thermal reduction, the other based on a vapor phase CVD deposition. We use N-doped mesoporous carbon nanospheres as supports, with high surface area and surface functionality to build Pt nanoparticles, clusters, and single sites.

The Pt speciation, depending on the synthesis approach, was thereby investigated a. o. by XRD, XPS, ac-STEM, XAS and electrochemical CO stripping. In all cases, when high Pt dispersion was achieved in form of Pt clusters and single sites, ultra-high mass activity was demonstrated at the RDE level [1,2].

Literature:

[1] Zeng, Z.; Küspert, S.; Balaghi, S. E.; Hussein, H. E. M.; Ortlieb, N.; Knäbbeler‐Buß, M.; Hügenell, P.; Pollitt, S.; Hug, N.; Melke, J.; Fischer, A. Small
2023, 2205885.

[2] Küspert, S.; Campbell, I. E.; Zeng, Z.; Balaghi, S. E.; Ortlieb, N.; Thomann, R.; Knäbbeler‐Buß, M.; Allen, C. S.; Mohney, S. E.; Fischer, A. Small
2024, 2311260.
Development of Sustainable, Environment-Friendly Protein-Based Proton Exchange Membranes for Fuel Cells and Water Electrolyzers
Authors: Yer Huseyin , Pasaogullari Ugur , Amdursky Nadav , Bliznakov Stoyan
Published: December 2024

In the twenty-first century, proton-exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs) represent promising technologies for clean and efficient power generation. Proton exchange membranes (PEMs) are the key components in PEMFCs and PEMWEs. Currently, all proton exchange membranes (PEMs) employed in PEMFCs or PEMWEs are based on synthetic primarily sulfonated polymers. While these synthetic polymers have good proton conductivity, they are expensive and raise environmental concerns. As a result, there is growing interest in identifying suitable alternatives that are cost-effective, sustainable, and environmentally friendly. Biopolymers, which are naturally occurring alternatives to synthetic polymers, are linked by covalent bonds and include cellular components such as proteins, nucleotides, lipids, and polysaccharides. Proteins derived from sustainable sources offer potential advantages for polymer production due to their ability to self-heal and their higher water transport capabilities, particularly in fast-growing plants like cannabis, soybean, corn. In this study, we aim to: (i) develop proton exchange membranes based on plant-based proteins, (ii) fabricate membrane electrode assemblies (MEAs) with the protein membranes and assess their performance as PEM fuel cells and water electrolyzers, and (iii) optimize the polymerization procedures to comply with green chemistry principles and ensure high proton conductivity at temperatures ranging from 80°C to 150°C, making them suitable for use in PEMFCs and PEMWEs.
Highly Gas Permeable and Dimensionally Stable Anion Exchange Ionomers for Anion Exchange Membrane Water Electrolyzers
Authors: Liu Fanghua , Liu Fanghua , Iwataki Toshio , Uchida Makoto , Kakinuma Katsuyoshi , Miyatake Kenji
Published: December 2024

Hydrogen, as a clean energy carrier, is promising to alleviate the dependence on fossil fuels and contributing to carbon-neutrality. Alkaline water electrolyzers (AEMs) and proton exchange membrane water electrolyzers (PEMWEs) have realized commercialization to produce pure hydrogen, while high corrosiveness resulting from concentrated KOH aqueous solution and low hydrogen production efficiency of AWEs, as well as high cost resulting from platinum group metal (PGM) catalysts of PEMWEs enforced to develop the alternatives. Anion exchange membrane water electrolyzers (AEMWEs) which combine the advantages of AWEs and PEMWEs have been regarded as attractive and effective electrochemical devices as emerging water electrolyzers. Over the decades, the catalysts and AEMs have been widely studied to improve the performance and durability of AEMWEs. However, ionomers in the catalyst layers, has been largely overlooked, while ionomers play roles in binding catalyst particles and permeating produced hydrogen and oxygen.

Herein, we developed anion exchange ionomers (QC6xBA and QC6xPA) with high gas permeability and dimensional stability by introducing bulky cyclohexyl (C6) groups into polymer backbones. Among synthesized polymers, QC650BA-2.1 (target ion exchange capacity, IEC: 2.1 mmol g-1) with 50 mol% C6 composition was the most gas permeable, having 16.6-fold higher H2 permeability and 22.3-fold higher O2 permeability than QC60BA-2.1 without C6 groups. Meanwhile, QC650BA-2.1 was also more dimensionally stable, the through-plane swelling ratio decreased to 12.5% (QC650BA-2.1) from 31.1% (QC60BA-2.1). Applying QC650BA-2.1 as the anode ionomer and PGM-free Ni0.8Co0.2O1) as anode catalyst, the water electrolysis cell showed 2 times higher performance (2 A cm-2 at 1.69 V) than the cell using our previous QPAF-4-2.02) ionomer. During 1000 h durability test at 1.0 A cm-2, the QC650BA-2.1 cell showed ignorable change of cell voltage with decay rate of 1.1 μV h-1 after initial voltage increase. These results indicated using high gas permeable and dimensionally stable ionomer is significantly effective to enhance the performance and durability of AEMWE.

Reference

1) Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, J. Mater. Chem. A
2017,5, 24804.

2) Shi, T. Tano, D. A. Tryk, M. Yamaguchi, A. Iiyama, M. Uchida, K. Iida, C. Arata, S. Watanabe, K. Kakinuma, ACS Catal.
2022, 12, 14209.