bluuebunny/crossref_metadata_2025 huggingface dataset:
Universal Platform for Robust Dual-Atom Doped 2D Catalysts with Superior Hydrogen Evolution in Wide pH Media
Authors: Kim Ki Kang
Published: December 2024

Layered 2D transition metal dichalcogenides (TMDs) have been suggested as efficient substitutes for Pt-group metal electrocatalysts in the hydrogen evolution reaction (HER). However, poor catalytic activities in neutral and alkaline electrolytes considerably hinder their practical applications. Furthermore, the weak adhesion between TMDs and electrodes often impedes long-term durability and thus requires a binder. Here, I present a universal platform for robust dual-atom doped 2D electrocatalysts with superior HER performance over a wide pH range media. V:Co-ReS2 on a wafer scale is directly grown on oxidized Ti foil by a liquid-phase precursor-assisted approach and subsequently used as highly efficient electrocatalysts. The catalytic performance surpasses that of Pt group metals in a high current regime (≥ 100 mA cm−2) at pH ≥ 7, with a high durability of more than 70 h in all media at 200 mA cm−2. First-principles calculations reveal that V:Co dual doping in ReS2 significantly reduces the water dissociation barrier and simultaneously enables the material to achieve the thermoneutral Gibbs free energy for hydrogen adsorption.
Enhancing the Image Quality of Quantum-Dots-Based Infrared-to-Visible up-Conversion Optoelectronic Device By Surface Ligand Engineering
Authors: Ma Yi-Chun , Chen Hsueh-Shih
Published: December 2024

Devices that convert infrared (IR) photons into visible photons have various applications, including IR detection, bio-imaging, and security. This study introduces an optoelectronic up-conversion device based on quantum dots (QDs) that combines an IR lead sulfide (PbS) QD photodiode (PD) with a visible green cadmium selenide (CdSe) quantum dot light-emitting diode (QLED). The device is assembled using a layer-by-layer wet coating method. To improve exciton extraction in the PbS layer, a ligand exchange process has been employed to further enhance the film quality as well as charge carrier property, which significantly reduces the applying current density of the corresponding device at 10 cd/m2 of brightness. Our quantum dot devices can effectively detect a 940 nm IR light source and produce clear visible images with a spatial resolution of approximately 50 µm. This feature is particularly promising for imaging sensing applications.
Engineered Carbon Supports for Heavy-Duty Fuel Cell Vehicle Applications
Authors: Ramaswamy Nagappan , Wortman James , Kongkanand Anusorn , Kumaraguru Swami , Payne Michael , Ostraat Michele
Published: December 2024

Proton Exchange Membrane (PEM) fuel cells are a suitable electrochemical power source for heavy duty vehicle (HDV) applications due to their high performance, efficiency, and durability. The cathode of the fuel cell uses a higher geometric loading of platinum (~0.2 to 0.4 mgPt/cm2) for the electrocatalysis of the kinetically sluggish Oxygen Reduction Reaction (ORR), which requires higher weight percent loading of the metal (~50%) on the carbon support to decrease the catalyst layer thickness and hence, the reactant transport losses. Conventional supports for platinum catalysts, such as the KetjenBlackTM type high surface area carbon (HSC), feature limited mesopore area for the dispersion of Pt nanoparticles leading to increased aggregation and poor durability. Here, we show a new class of carbon materials developed by Pajarito Powder known as the Engineered Catalyst Support (ECS) with higher mesopore fraction for the dispersion of higher weight percentage of Pt nanoparticles. ECS materials can disperse up to 50% Pt by weight of the catalyst, thereby enabling lower catalyst layer thickness with higher performance retained after durability test. ECS materials are tunable in terms of their mesopore structure, graphitization levels and the use of metal-based additives as dopants on the carbon support to anchor catalyst nanoparticles. A comprehensive set of physico-chemical and electrochemical studies in membrane electrode assembly (MEA) are reported to understand the performance and durability of Pt/ECS catalysts.

Acknowledgements: This work is partially supported by U.S Department of Energy, Hydrogen and Fuel Cell Technologies Office under grant DE-EE0008821 and DE-EE0010749.
Modeling Water Uptake, Swelling, and Proton Conduction in Thin Ion-Conducting Films
Authors: Alam Shahriar , Allen Jeffrey S
Published: December 2024

Water absorption, volumetric expansion, and proton conduction in ion-conducting thin polymer films, pertinent to fuel cell catalyst layers, are modeled using a network model architecture. In addition to the effect of confinement (increase in Young's modulus), the modeling technique ascribes increased hydrophobicity to decreased water retention, volumetric swelling, and proton conductivity. This approach can be used to effectively capture the distribution of mass and ion transport resistances in a PEMFC catalyst layer under different fuel cell operating scenarios.
High-Loading Intermetallic PtCo Nanoparticles Supported on S-Doped Carbon for Oxygen Reduction Reaction Catalysts
Authors: Yang Hyunwoo , Chang HyunWoo , Lee KwangHo , Yang HyunWoo , Cho EunAe
Published: December 2024

Improving catalysts for the oxygen reduction reaction (ORR) is crucial for commercialization of proton exchange membrane fuel cells (PEMFCs) due to the sluggish kinetics of ORR at the cathode. Current ORR catalysts face challenges such as high costs associated with precious metals and poor durability. A common approach to improve catalyst activity is to alloy Pt with transition metals, such as cobalt and nickel, to control the d-band center. Instead of the disordered PtM, Pt intermetallic compounds show improved ORR intrinsic activity and enhanced stability. Also, doping carbon supports with heteroatoms such as nitrogen and sulfur is a feasible strategy to enhance the interaction between the metal nanoparticles of the catalyst and its support, which leads to improved performance and stability of the catalysts.

In this study, we synthesized high-loading intermetallic PtCo nanoparticles supported on sulfur-doped carbon. High metal loading catalysts have significant advantages for practical PEMFC applications as they accelerate mass transport, leading to a reduction in voltage loss, especially under high current densities. To synthesize high-loading intermetallic PtCo nanoparticles, uniform sulfur doping on commercial carbon support is introduced, since sulfur sites can anchor metal nanoparticles even during a harsh heat treatment process. The sulfur sites not only minimize sintering, but also improve the electrochemical performance. Using this approach, high-loading (52.5 wt%) sub-5 nm PtCo intermetallic compounds with a Pt-rich shell (PtCo@Pt/S-BP) were successfully synthesized. The morphology and characteristics of the PtCo nanoparticles were confirmed through various techniques, including XRD, TEM, ICP-OES, HAADF-STEM, EDS mapping, and XPS analysis. In the half-cell test, PtCo@Pt/S-BP exhibited over 5-fold enhancement in mass activity and 6-fold increase in specific activity compared to commercial Pt/C. Additionally, the performance of PtCo@Pt/S-BP was maintained even after 50,000 cycles due to thermodynamically stable structure of the intermetallic phase and Pt-rich shell. This synthesis strategy provides a promising pathway for practical application of Pt-based catalysts in future PEMFCs.
Effect of Carbon Supports on Performance and Durability of Hydrogen Fuel Cells
Authors: Atwa Marwa , Prinz Fritz
Published: December 2024

The global demand for clean and sustainable energy sources continues to rise, with hydrogen emerging as a key player in the energy landscape. Polymer exchange membrane fuel cells (PEMFCs) are positioned as a promising solution, converting hydrogen's chemical energy into electricity with zero emissions, which is particularly suitable for various industrial applications, including automotive.

While PEMFCs fueled by hydrogen offer superior efficiency over internal combustion engines, there's a pressing need for significant advancements in durability while maintaining high efficiency and performance, especially for light-duty vehicles. Furthermore, meeting the demands of heavy-duty applications necessitates substantial lifetime improvements (aiming for 4-5 times the current durability) alongside high efficiency.

In this presentation, we delve into the nanoengineering progress of developing highly durable and efficient cathodes for PEMFCs. Our approach leverages mesoporous carbons as supports and platinum as the electrocatalyst. Through extensive research, we've identified novel cathodes capable of achieving exceptional catalytic activity, performance, durability, and resistance to carbon corrosion—a unique combination rarely found in a single material.

Our study involved exploring a range of mesoporous carbon supports with varying porosity and graphitization degrees within a single-cell PEMFC device to identify the key characteristics conducive to robust cathode performance. By screening these supports, we've uncovered insights crucial for designing PEMFC cathodes resilient to platinum dissolution and performance losses even after undergoing several thousand accelerated durability tests while also exhibiting inherent corrosion resistance.
Pt-Cu Nanosheet Catalysts for Pemfcs with Enhanced Durability through Galvanic Replacement Reaction
Authors: Yang HyunWoo , Lee SangJae , Lee KwangHo , Chang HyunWoo , Roh JeongHan , Shin Dongwon , Kim Minjun , Cho EunAe
Published: December 2024

In order to cope with the cataclysmic environmental problems, PEMFCs are in the spotlight as a next-generation renewable energy utilization candidate, but the high platinum unit price used in the catalyst layer is still a sticking point. Accordingly, attempts are being made to maximize platinum utilization and improve performance through shape control of the catalyst, but there is a problem in that the structure collapses under extreme PEMFCs driving conditions and the performance deteriorates rapidly, resulting in wistful durability. In this work, Pt-Cu nanosheet with 15~20 nm lateral size and 1 nm thickness was synthesized on carbon support (PtCu NS/C) and further enhanced durability through surface copper substitution using galvanic replacement reaction (G-PtCu NS/C). To clarify the catalyst structure in more detail, acid-leached Pt-Cu nanosheet (A-PtCu NS/C) was synthesized by eluting copper on the surface, and the differences in electronic structure were compared through XAS and XPS. In the half-cell configuration, G-PtCu NS/C demonstrated high performance and excellent durability retention after 30,000 square-wave cycles (SWC) of accelerated stress test (AST). Moreover, G-PtCu NS/C showed marginal shift in CO adsorption peak after AST, indicating the high stability of catalyst structure. In the full-cell test, performance of G-PtCu NS/C after 30,000 SWC AST is consistent to initial performance, while PtCu NS/C showed noticeable power density drop at high current density region. Ex-situ EDS elemental mapping and XRF of membrane-electrode assembly (MEA) after AST confirms that transition metal dissolution on G-PtCu NS/C was imperceptible. Our study suggests new engineering method for shaped controlled catalysts to be applied on PEMFCs.
Crystallography of Intermetallic Pt Nanoparticle Catalysts on Engineered Carbon Supports
Authors: Payne Michael , Bernal Diego , Klein Molly , Lenhart Brian , Ostraat Michele
Published: December 2024

Platinum-based electrocatalysts represent the state-of-the-art for many fuel cell and electrolyzer applications due to their relatively high activity for both the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR). Due to the high cost of Pt metal, Pt utilization is maximized by dispersing the Pt on a carbon support as nanoparticles, but further improvements to catalyst activity and durability, as well as further cost reductions, are required for commercialization of fuel cell and electrolyzer technologies. Essential to the improvement of such catalysts is the design and preparation of Pt-based crystalline nanostructures, which can enhance the activity and durability of an electrocatalyst without increasing Pt loading. Furthermore, by alloying Pt with other, more earth-abundant transition metals, ordered intermetallic nanoparticles can be prepared which display not only enhanced electrocatalytic properties, but also require less of the expensive Pt metal for fabrication. Here, we crystallographically describe various intermetallic Pt catalysts supported on a new class of carbon materials developed by Pajarito Powder known as the Engineered Catalyst Support (ECS). ECS materials can disperse up to 50% Pt by weight of the catalyst by virtue of the high support surface area (400-900 m2/g), ideal for structural study by bulk crystallographic methods. Through correlation of crystalline Pt structures with electrochemical performance data, structure/function relationships are established to inform the high performance of Pt/ECS catalysts.
Robust Fuel Cell Electrodes: Pt Thin Film Catalysts for Anode Reversal Tolerance
Authors: Liyanage Wipula Priya Rasika , Ince Alper Can , Komini Babu Siddharth , Borup Rod L. , Spendelow Jacob S.
Published: December 2024

In recent years, polymer electrolyte membrane fuel cells (PEMFCs) have garnered significant attention due to their remarkable attributes including high power density, energy efficiency, and zero-emission characteristics. This surge in interest has primarily been driven by the potential of PEMFC-powered fuel cell electric vehicles (FCEVs) to substantially reduce carbon dioxide emissions in the transportation sector, thereby propelling the advancement of the hydrogen economy on a global scale. However, the widespread commercialization of FCEVs hinges upon addressing key challenges surrounding the durability and resilience of fuel cell systems.

One critical issue that has emerged is the phenomenon of hydrogen starvation in the anode, particularly during start-up/shutdown or cold start scenarios, which can lead to rapid and severe degradation of PEMFC performance and durability through cell reversal. This degradation manifests quickly, often within minutes, resulting in abrupt cell failure. Extensive prior research has been devoted to unraveling the mechanisms underlying degradation induced by hydrogen starvation and cell reversal in PEMFCs, with the goal of identifying effective mitigation strategies to minimize damage to membrane electrode assembly (MEA) components.

In this study, we introduce an innovative materials approach aimed at mitigating cell damage by employing a thin film Pt anode catalyst supported on Nafion nanowires in a co-axial configuration, referred to as coaxial nanowire electrode (CANE). Leveraging the high roughness of Nafion nanowires, CANE eliminates the need for conventional carbon support and exhibits exceptional tolerance to reversal-induced stress. We present a comprehensive evaluation of CANE as a reversal-tolerant anode, comparing its performance to that of conventional supported catalysts (Pt/C). Furthermore, we explore the potential for further enhancing durability by integrating iridium with the CANE anode. Finally, we will delve into our efforts to evaluate the feasibility of implementing this concept in structures that can be manufactured at scale. This research contributes to the ongoing efforts to enhance the robustness and longevity of PEMFC systems, thereby advancing the prospects of FCEVs as a sustainable and viable solution for future transportation needs.

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. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (2020200DR).
Benchmarking Electrocatalyst Stability Tests Using Lab-Scale Alkaline Water Electrolyzers
Authors: Marquez Raul A. , Espinosa Michael , Kalokowski Emma , Son Yoon Jun , Kawashima Kenta , Le Thuy Vy , Chukwuneke Chikaodili E. , Mullins C Buddie
Published: December 2024

Green hydrogen from low-temperature water electrolysis has received significant attention, with a projected thousand-fold global capacity expansion by 2030. Electrocatalyst research is crucial for advancing water electrolysis. However, despite a surge in publications showing novel electrocatalytic materials, few studies have scaled these to more realistic setups. This gap primarily stems from the inadequacy of testing environments and operating conditions in academic research. The prevalent use of three-electrode cell configurations fails to mimic practical electrolyzer conditions accurately. Therefore, implementing stability tests in realistic device configurations is essential to assess compounded instability.

Our group has developed and optimized a lab-scale electrochemical flow cell for alkaline water electrolysis (AWE), refined over four years of dedicated research (Figure 1a). This work outlines the operation of this device in a laboratory environment, focusing on accelerating the evaluation of electrocatalytic materials and their durability. We examined the performance of this electrolyzer under industrially relevant conditions, including varying temperatures (Figure 1b). We examined the stability of three standard electrocatalytic materials to demonstrate the electrolyzer performance under fluctuating current conditions, including a benchmark NiFe anode (Figure 1c) and a nickel nitride (Ni3N) precatalyst (Figure 1d). We propose a standardized protocol for assessing electrocatalysts under fluctuating and reverse currents, contributing to the understanding of catalyst deactivation. This initiative marks a significant advancement in AWE electrocatalysis research. We aim to establish a practical and straightforward protocol for evaluating and validating electrocatalysts in AWE, fostering accurate performance comparisons.

Figure 1
Development of Binder Free Fe Substituted NiCo2O4 Electrocatalyst Using Electrostatic Spray Deposition for Efficient Oxygen Evolution Reaction
Authors: OH JunSeok , Tamboli Asiya M. , KIM Wan Sik , IM Sejin , Sim Junseok , Jung Younghan , Kim Chang-Hee
Published: December 2024

Development of energy efficient electrocatalysts of oxygen evolution reaction (OER) is one of the most important challenges for the development of green hydrogen production by water electrolysis. In general, the use of binders for electrode fabrication may result in limited contact areas between catalyst and electrolyte decreasing electroactive sites, thus reducing electrocatalytic activities. To overcome these challenges, spinel-type ternary transition metal oxides, focusing on Fe substituted NiCo2O4, were fabricated using the electrostatic spray deposition (ESD) method without any binder. The various characterizations techniques such as XRD, XPS, and SEM were employed to explore morphological and structural features. The electrochemical OER properties were investigated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 1 M KOH. The optimized sample exhibited excellent operational stability under continuous and dynamic operating conditions without any significant performance decay. This study reveals that binder free electrocatalyst is a good candidate for inexpensive and durable electrocatalyst for commercial application.
Self-Supported Transition Metal Based-Textile Electrodes through Interfacial Assembly for Overall Water Splitting in Alkaline Media
Authors: Mo Jeongmin , Cho Jinhan
Published: December 2024

Water splitting holds significant promise for sustainable hydrogen production without carbon emissions. To develop electrodes suitable for large-scale hydrogen generation, characteristics such as large surface area, low electrical resistance, high electrocatalytic activity, and enduring operational stability are paramount. In our investigation, we've engineered high-performance water-splitting electrodes (WSEs) with exceptionally low overpotentials and robust stability through a process integrating carbonization and interfacial assembly-induced electrodeposition. These electrodes feature high-quality electrocatalytic structures based on transition metals (Ni, Fe, and Co), facilitated by strong electronic interactions. They exhibit low sheet resistance akin to bulk metals, a porous 3D architecture with ample specific surface area, and robust interfacial adhesion between the textile-based support and electrocatalysts. Our methodology begins with textiles, transformed into hydrophilic conductive substrates via carbonization and acid treatment, with additional amine molecule incorporation to enhance support-electrocatalyst interactions. Notably, our hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrodes demonstrate extremely low overpotentials (12 mV at 10 mA cm−2 for HER, 186 mV at 50 mA cm−2 for OER) under alkaline conditions. Furthermore, our full-cell electrodes exhibit sustained water-splitting activity at diverse current density from 10 to 2000 mA cm−2 for at least 2100 hours in 1 M KOH solution. We anticipate that our methodology lays a foundational framework for the development of commercially viable, high-performance WSEs.
Improvement of Mass Activity of IrOx Electrocatalyst in Acidic Oxygen Evolution Reaction Using Bi3TaO7 Support
Authors: Yun Young Hwa , Lee Changsoo , Koo Bonjae
Published: December 2024

Developing highly conductive and durable support materials for Ir-based electrocatalysts in acidic oxygen evolution reactions (OER) is one of the challenges to overcoming corrosion conduction during the anodic process. In this study, we develop an oxide-type support material(Bi3TaO7) for IrOx electrocatalyst in acidic OER to minimize the amount of iridium loading level. Through a combination of various physical and chemical analyses(XRD, TEM, XRF, EIS, XPS, XAS, etc.), it is demonstrated that the IrOx/Bi3TaO7 electrocatalyst showed remarkable OER performances and enhanced mass activity compared to unsupported IrOx electrocatalysts. Bi on the surface of Bi3TaO7 suppresses the change in oxidation state of Ir element, maintains activity of IrOx electrocatalyst during electrochemical reaction and induces chemical and physical stability of the IrOx/Bi3TaO7 electrocatalyst. These findings can provide further insight into a new category of anode support materials for proton exchange membrane water electrolyzers.
Study on Effect of Activation Procedure on Anion Exchange Membrane Water Electrolyzer Using Ni-Mo Electrocatalyst for Hydrogen Evolution Reaction
Authors: Lee Wonjae , Yun Hyebin , Kim Yongmin , Jeon Sun Seo , Chung Hoon Taek , Han Byungchan , Lee Hyunjoo
Published: December 2024

Hydrogen Evolution Reaction (HER) in Anion Exchange Membrane Water Electrolyzer(AEMWE) requires fewer electrons compared to the oxygen evolution reaction, which is why research on it started later. However, when using an anion exchange membrane, the hydrogen evolution reaction occurs in multiple steps, and the dissociation of water is requisite first. The water splitting is challenging, hence catalysts that enhance water decomposition are essential. Currently, Platinum supported by carbon is used as the most stable and efficient material for HER. However, due to Platinum is rare and expensive, leading to significant research into alternative materials. Among various non-precious metal candidates, Nickel is known for its superior hydrogen evolution performance. Yet, the performance of Nickel alone is inferior to that of Platinum. Nickel exhibits enhanced performance and durability when combined with other metals due to a synergistic effect. The second metal, such as Copper, Cobalt, Iron, or Molybdenum, shows improved performance when alloyed with Nickel . Amon them Ni–Mo catalyst has shown high activity for HER in AEMWE. Among various Ni/Mo molar ratios, the catalyst showed the highest activity when it was 3. With Ni3Mo as the cathode, a single cell was fabricated using non-noble metal catalysts exclusively. Interestingly, the activation procedure significantly affected the cell performance. The single cell performed better than that with the Pt/C catalyst when the Ni3Mo catalyst was activated at 50 mA/cm2. Molybdenum tends to dissolve once the reaction begins the distribution of Mo in electrodes, membrane, and electrolytes was estimated, confirming Mo dissolution from the cathode. Once the cell was activated, the cell performance was stable without degradation in long-term chronopotentiometry operation, but the performance was degraded by sudden voltage change such as imposing open circuit voltage . The surface structure and reaction mechanism were studied with density functional theory: the Mo-dissolved Ni3Mo(101) surface could promote H2O dissociation, while MoO3 stably adsorbed on the surface weakened H* adsorption, promoting HER. This study provides important insights into the development of efficient catalysts for large-scale hydrogen production.
Investigating Activity and Stability of Mixed-Metal Oxides (M-NiO) for Anion Exchange Membrane Electrolysis
Authors: Ha Mai-Anh , Hansen Mitchell , Mercer Emily , Norman Andrew , Miller-Link Elisa , Volk Emily K. , González Héctor , Alia Shaun M
Published: December 2024

Recent experimental studies suggest mixed oxides of Ni, Co, and Fe operated in basic media may be the strongest alternative to iridium.1, 2 However, the efficiency of these catalysts is strongly synthesis-dependent and there is no established understanding of the role of the different metals in operation with ionomers. Notably, Trotochaud, et al. observed catalyst efficiency in the order Ni0.9Fe0.1Ox > NiOx > NiyCo1-y, whereas Morales-Guio, et. al. ranked FeNiOx, CoFeNiOx > CoNiOx > NiOx.1, 2 Anderson et al. found in their RDE studies of commercial catalysts that NiFe2O4outperformed NiO, Co3O4 by 7 times kinetically. In low concentrations, these mixed-oxide materials may behave more closely to doped-catalysts, where dopants can increase activity, change selectivity, and even improve resistance to poisoning of active sites.3-6 Understanding how and why these catalysts work, and do not work, is critical to enabling these materials to achieve the Hydrogen Shot goal of $1/kg H2 in 1 decade. For our theoretical model, we limited our mixed material model to a single dopant to fully examine the geometric and electronic effects of a nearby transition metal e.g., Fe and Co dopants. Plane-wave density functional theory calculations elucidated the dopant-effects on both activity (the oxygen evolution reaction) and stability in anion exchange membrane electrolysis in the presence of experimentally-relevant ionomers (Georgia Tech, Nafion, Versogen, and Sustainion).

(1) Trotochaud, L.; Ranney, J. K.; Williams, K. N.; Boettcher, S. W. Solution-cast metal oxide thin film electrocatalysts for oxygen evolution. Journal of the American Chemical Society
2012, 134 (41), 17253-17261.

(2) Morales-Guio, C. G.; Liardet, L.; Hu, X. Oxidatively electrodeposited thin-film transition metal (oxy) hydroxides as oxygen evolution catalysts. Journal of the American Chemical Society
2016, 138 (28), 8946-8957.

(3) Ha, M.-A.; Dadras, J.; Alexandrova, A. Rutile-deposited Pt–Pd clusters: A hypothesis regarding the stability at 50/50 ratio. ACS Cat.
2014, 4(10), 3570-3580.

(4) Baxter, E. T.; Ha, M.-A.; Cass, A. C.; Alexandrova, A. N.; Anderson, S. L. Ethylene Dehydrogenation on Pt4, 7, 8 Clusters on Al2O3: Strong Cluster Size Dependence Linked to Preferred Catalyst Morphologies. ACS Cat.
2017, 7 (5), 3322-3335.

(5) Ha, M.-A.; Baxter, E. T.; Cass, A. C.; Anderson, S. L.; Alexandrova, A. N. Boron switch for selectivity of catalytic dehydrogenation on size-selected Pt clusters on Al2O3. Journal of the American Chemical Society
2017, 139 (33), 11568-11575.

(6) Halder, A.; Ha, M.-A.; Zhai, H.; Yang, B.; Pellin, M. J.; Seifert, S.; Alexandrova, A. N.; Vajda, S. Oxidative Dehydrogenation of Cyclohexane by Cu vs Pd Clusters: Selectivity Control by Specific Cluster Dynamics. ChemCatChem
2020, 12 (5), 1307-1315. DOI: 10.1002/cctc.201901795.

Figure 1
Mechanical Alloying of Nickel-Based Catalysts for Alkaline Water Electrolysis
Authors: Phan Thu Pham Anh , Kraglund Mikkel Rykær , Lakhotiya Harish , Jensen Jens Oluf
Published: December 2024

We have explored the catalytic properties of various Raney nickel alloys for alkaline water electrolysis (AWE), addressing the technology's challenge of low current-density operation. Different alloy compositions were successfully synthesized by high-energy ball milling under optimized conditions, resulting in a high yield (>95%) and ability to tune particle sizes, ranging from micron to submicron, within a short synthesis duration. Nickel-aluminum alloys, as precursors for Raney Ni, were synthesized. Additionally, the incorporation of third metal elements such as molybdenum (Mo), chromium (Cr), vanadium (V), was investigated, indicating the flexibility and efficiency of the synthesis method.

The crystallinity and phase composition of the alloys were analyzed by X-ray powder diffraction (XRD) as shown in Figure 1A. Thermal effects on alloy phase changes were investigated through in-situ XRD analysis. The finding revealed significant alterations in crystallinity and phase composition of Ni-Al alloy at temperatures exceeding 700 oC, consequently impacting catalytic performance.

Subsequently, the synthesized catalyst powders were applied onto electrode substrates using an airbrushing technique (Figure 1B). Following an activation procedure, the catalysts were evaluated through half-cell electrochemical measurements, with selected samples tested for stability in a flow cell setup. Catalytic performance of electrodes prepared with the synthesized Raney Ni catalyst exhibited substantial enhancement towards the hydrogen evolution reaction (HER) compared to bare Ni substrate. With catalyst loading of 3 mg/cm2, a notably low overpotential of 59 mV was achieved at current density of 50 mA/cm2 in 1M KOH.

The research is funded by Stiesdal Hydrogen A/S.

Figure 1
Iridium Oxide and Niobium-Doped Iridium Oxide Anodes for PEM Water Electrolysis: Towards Sustainable Hydrogen Production with Superior Performance
Authors: Lenhart Brian , Nguyen Van , Wagner Lindsay , Mckinney Samuel , Ostraat Michele
Published: December 2024

The global push towards cleaner energy sources has heightened the demand for high-performing, durable proton exchange membrane water electrolyzer (PEMWE) electrocatalysts. Green hydrogen, generated through water electrolysis powered by renewable energy, stands as a prominent solution in this endeavor to transition away from fossil fuels. Among various electrolyzer technologies, PEMWE systems currently offer the most competitive pathway for green hydrogen production. These systems typically employ a platinum on carbon supported (Pt/C) cathodic electrocatalyst for the hydrogen evolution reaction (HER) and an iridium oxide (IrOx) anodic electrocatalyst for the oxygen evolution reaction (OER). Efforts to enhance PEMWE performance primarily focus on improving the kinetics of the OER process, which accounts for the majority of activation overpotential during operation. To address cost concerns associated with IrOx, researchers are exploring alternative formulations, including doping with materials like niobium (Nb), aiming for comparable performance at reduced Ir loading [1], [2], [3]. It is argued that higher surface area and lower crystalline IrOx catalysts lead to lower activation overpotentials and enhanced durability, respectively. In this study, we investigate the performance of high-surface-area IrOx electrocatalysts (>200 m2/g) and Nb-doped IrOx variants, comparing them with commercially available benchmarks. Through rigorous examination utilizing Rotating Disk Electrode (RDE), Gas Diffusion Electrode (GDE) half-cell, and Membrane Electrode Assemblies (MEAs), we report on the performance and stability of our in-house prepared materials. Preliminary results examining various loadings of IrOx suggest that lower loadings lead to durable and active electrocatalyst layers. Our findings underscore the potential of Nb-doped IrOx as a cost-effective alternative for PEMWE electrocatalysts, offering promising advancements in the pursuit of efficient and sustainable hydrogen production.

References:

[1] C. Baik, S. W. Lee, and C. Pak, “Glycine-induced ultrahigh-surface-area IrO2@IrOx catalyst with balanced activity and stability for efficient water splitting,” Electrochim Acta, vol. 390, Sep. 2021, doi: 10.1016/j.electacta.2021.138885.

[2] K. Zhang et al., “Status and perspectives of key materials for PEM electrolyzer,” Nano Research Energy, vol. 1, no. 3. Tsinghua University Press, Dec. 01, 2022. doi: 10.26599/NRE.2022.9120032.

[3] X. Duan et al., “Boosting the efficiency of IrOx nanoparticles with micron-flower Nb4N5 support for oxygen evolution reaction in polymer electrolyte membrane water electrolyzer,” Electrochim Acta, vol. 470, Dec. 2023, doi: 10.1016/j.electacta.2023.143271.
The Role of Porous Transport Layer in Enabling Low Anode Catalyst Loadings
Authors: Wrubel Jacob A , Parimuha Makenzie , Young James L. , Bender Guido
Published: December 2024

Hydrogen (H2) is a focal point of the U.S. Department of Energy’s (DOE) plan for a future energy economy that is secure, resilient, and environmentally friendly [1]. And proton exchange membrane water electrolysis (PEMWE) is a promising technology for renewable H2 production. Yet, state-of-the-art PEMWEs use significant amounts of expensive platinum group metals (PGMs), namely, Pt and Ir, which leads to large capital expenses (CapEx). Techno-economic analysis has shown that CapEx is just as, if not more, important as operating expenses (OpEx) for enabling $1/kgH2.

In recent years, the price of Ir has significantly increased, even compared to Pt. Reducing the Ir loading in a PEMWE cell or stack is a straightforward way to reduce CapEx. However, anode catalyst layers (ACLs) with reduced Ir loadings tend to suffer from poor electrical in-plane conductivity and low utilization, leading to significantly higher overpotentials. Supported catalyst materials, i.e., Ir decorated onto a conductive substrate material, could help address these drawbacks, but the catalyst support material must also be stable at the elevated potentials seen by the anode. To date there is no suitable support material that offers both stability and good performance. Therefore, strategies to improve performance using unsupported Ir are of great value.

In this work, we studied 6 different commercial porous transport layer (PTL) materials to observe their effect on cell performance as the anode Ir content was reduced. The PTL is responsible for conducting electrons from the ACL. The morphology of the PTL and the structure of the ~2D interface it creates with the ACL can strongly affect overpotentials associated with in-plane electronic resistance and impact catalyst utilization. All PTLs studied were made from pure Ti. They included both fibrous and sintered particle archetypes. Beginning of life and 1000 h durability results from studies with both 0.1 mgIr/cm2 and 0.4 mgIr/cm2 loadings will be discussed in the presentation. For example, as seen in Figure 1, we found that the PTL greatly influences cell performance at ACL loadings of 0.1 mgIr/cm2, though the effect was less pronounced at 0.4 mgIr/cm2. Changes in both ohmic and kinetic overpotentials were observed.

References:

[1] Pivovar B, Rustagi N, Satyapal S. Hydrogen at Scale (H2@Scale): Key to a Clean, Economic, and Sustainable Energy System. Electrochem. Soc. Interface 2018; 27:47–52.

Figure 1
Sputter-Coated Catalyst Layers for Low Loading Anodes for Proton Exchange Membrane Water Electrolysis
Authors: Beltran Diana E. , Chao Bennett A. , Parimuha Makenzie , Duarte Ricardo P. M. , Wrubel Jacob A , Bender Guido , Young James L.
Published: December 2024

Hydrogen technology offers a clean energy solution for industries and transportation, with PEM water electrolyzers playing a pivotal role in its production. These electrolyzers are efficient and can utilize renewable energy sources, producing hydrogen without carbon emissions. However, challenges such as high capital costs, limited durability, and supply chain constraints need to be addressed for widespread adoption. Efforts to reduce costs include reducing platinum group metal catalyst loadings, specifically iridium (Ir) in the anode and/or as the protective coating on porous transport layer (PTL). Changes in ink composition for fabricating catalyst layers can pose integration challenges related to compatibility, electrochemical performance, and manufacturability. Sputter-depositing these catalyst layers is a promising alternative fabrication method that can streamline production. It offers precise control over thickness, uniformity, and composition, as well as potentially eliminating the need for ionomer in the catalyst layer. In this presentation, we will report on the effects of sputter-deposited anode catalyst layers on two different commercially available PTL and microporous transport layer (MPL). The effects of loadings on performance will be discussed. Preliminary results show that performance decreases as loading decreases with the extent of performance loss depending on the choice of MPL or PTL.

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The Electrochemical Kinetics of the H-Upd and O-Upd on Polycrystalline Platinum
Authors: Brandes Benedikt Axel , Moretti Enzo
Published: December 2024

Underpotential depositited hydrogen on different platinum surfaces has been studied for over a century, yet we know very little about its nature. This is due to a combination of experimental limitations of surface characterisation, attributed to most techniques being virtually blind to adsorbed hydrogen atoms through the present electrolyte layer.

In this work I present a thourough mathematical derivation of the kinetics of the H-upd, the O-upd, and mass transport phenomena from the Butler-Volmer model. Through a new measurement approach I am then able to estimate the local pH on the Pt surface allowing me to determine the rate constant of the process behind the H-upd. An extensive survey in a wide range of electrolytes reveals a astonishing consistency of the rate constant but also a surprsing dependency of the the presence of molecular hydrogen. I wish to start a debate if the extracted kinetic parameters truly represent the rate constant of the H-upd or are mere artefact of the employed measurement method.

Eventually I will illuminate the debate on the origin of the observed CV patterns, notably the role of cations and anions, and provide insights into the role of the H-upd in respect to the HOR/HER and how its study can advance the development of new electrocatalysts.

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Poly(pyrrolidinium)-Based Anion Exchange Membranes and Ionomers for Anion Exchange Membrane Water Electrolyzers
Authors: Lee Albert S
Published: December 2024

Anion exchange membranes and ionomers are a critical technology for next generation energy conversion devices such as fuel cells, water electrolyzers, and CO2 electrolyzers. However, alkaline stability and poor understanding of performance and durability limiting descriptors have limited the development of a commercial benchmark membrane and ionomer, as is the case for Nafion and other perfluorinated ionomers in proton exchange membranes. In this talk, the chemistry of some new poly(pyrrolidinium)-functionalized membranes and ionomers will be introduced, including their simple membrane chemistry based on radical cyclopolymerization of diallylammonium functionalized aryl-ether-free backbones and benzene-free polydiallylammonium ionomeric binders. Synergistically integrated membranes and ionomers exhibit excellent alkaline stability, tunable IEC and crosslink density, controllable water uptake, which help elucidate critical performance-defining features of anion exchange membrane water electrolyzer membrane electrode assemblies.
Radical-Mediated Cross-Linked Anion Exchange Membranes for Efficient Alkaline Water Electrolysis Cells
Authors: Mahmoud Ahmed Mohamed Ahmed , Miyatake Kenji
Published: December 2024

The has been a strong demand for eco-friendly energy conversion and storage devices.1 Anion exchange membrane water electrolyzers (AEMWEs) which produce pure hydrogen and oxygen by water splitting, have gained considerable attention owing to their high efficiency and possible utilization of low-cost nonprecious metals (e.g., Ni, Co, and Fe) as electrocatalysts, separators, and gas diffusion layers.1,2 Anion exchange membranes (AEMs) as an indispensable key component in AEMWEs play several crucial roles including hydroxide ion and water transportation as well as gas separation.1,2 Furthermore, AEMs should possess multiple characteristics such as excellent thin membrane forming capability, mechanical and dimensional stability (or low swelling) in water, and alkaline stability under operating conditions.2 In this work,3 we investigate the effect of cross-linking on partially fluorinated AEMs tethered with trimethylpropyl side chain via radical-mediated cross-linking reaction (Figure 1). The one-pot cross-linking and quaternization reactions were successful as confirmed through NMR spectra. Transparent membranes (xQPAF-C3-VB) were obtained with 9.1-36.0% degree of cross-linking (DOC). TEM images revealed smaller hydrophilic/hydrophobic phase-separated morphology. As well as the suppressed water uptake in the cross-linked membranes, the hydroxide ion conductivity decreased slightly. Among them, xQPAF-C3-VB with 17.4% DOC (ion exchange capacity of 1.16 meq g-1) exhibited the highest hydroxide ion conductivity (56 mS cm-1 at 30 ℃) which was comparable to that of the pristine (uncross-linked) membrane. In addition, the cross-linking strategy helped to improve the thermomechanical properties resulting in higher glass transition temperature. The cross-linked xQPAF-C3-VB was utilized as membrane in AEMWEs to achieve high efficiency (74%) and reasonable performance (1.67 V at 1.0 A cm-2) (Figure 1).

References:

Vincent, D. Bessarabov Renew. Sustain.
Energy Rev. 2018, 81, 1690–1704.

Du, C. Roy, R. Peach, M. Turnbull, S. Thiele, C. Bock, Chem. Rev. 2022, 122, 11830–11895.

M. A. Mahmoud, K. Miyatake, F. Liu, V. Yadav, L. Guo, C. Y. Wong, T. Iwataki, K. Kakinuma, M. Uchida Adv. Energy Sustainability Res.
2024, 5, 2300236.

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Approaches to Mitigate Electrochemical Ionomer Oxidation
Authors: Kim Yu Seung , Lim Jihoon , Klein Jeffrey Michael , Lee Seung Geol , Park Eun Joo , Kang Sun Young , Maurya Sandip , Mustain William Earl , Boettcher Shannon W.
Published: December 2024

Hydrogen production through anion-exchange membrane water electrolyzers (AEMWEs) presents cost advantages compared to proton-exchange membrane equivalents, thanks to the heightened oxygen evolution reaction (OER) efficiency of platinum-group-metal-free catalysts in alkaline environments. However, the electrochemical oxidation of ionomers at the OER catalyst interface leads to a decrease in local electrode pH, which hampers AEMWE performance. Various strategies at the single-cell level have been explored to tackle this challenge. This article delves into the current understanding of electrochemical ionomer oxidation and its alleviation methods, offering our perspective on each approach. Our analysis emphasizes the efficacy of the competitive adsorption strategy in mitigating ionomer oxidation. This perspective piece also outlines future pathways for advancing high-performance alkaline AEMWEs and other energy devices utilizing hydrocarbon ionomers.
Investigation on the Interaction of Catalyst and Ionomer in AEM Electrolysis
Authors: Chan Ai-Lin , Clauser Arielle L , Kreider Melissa E , Volk Emily K. , Sugar Josh D , Alia Shaun M
Published: December 2024

In low temperature electrolysis, anion exchange membrane (AEM) systems combine the advantages of alkaline and proton exchange membrane (PEM) electrolysis in generating high purity hydrogen and reducing material costs from catalysts and component coatings [1]. Recent studies in AEM electrolysis have focused on improving cell performance, minimizing catalyst dissolution and mitigating ionomer/membrane degradation with different operating conditions. Ionomers play a critical role in the electrode because they provide ion conductivity, enhance mechanical support, and create preferred morphologies for electrolyte and produced gas to move [2, 3]. Optimizing catalyst-ionomer interactions by varying ionomer content, chemistries, and forms can accelerate the development of AEM electrolysis in terms of performance enhancement, cost and lifetime.

In this work, different forms of ionomer (powdered and dispersed) with two polymer backbones were evaluated in AEM electrolysis cell testing. Ni- and Co-based oxides and IrO2 were applied as anode catalysts. In Figure 1, the anodes with powdered ionomer outperform the dispersed samples. With Co3O4 catalyst, the overpotential can be improved by 0.9 V at 1 A/cm2 (iR-free voltage of Co3O4 with powdered ionomer: 1.68 V at 1 A/cm2). By electrochemical diagnostic and modeling methods, the improved performance with powdered ionomer is attributed to better reaction kinetic from more active area between catalysts and ionomers, less ohmic overpotentials due to better contact between the electrode and the transport layer and preferred transport properties with higher porosity created by powdered ionomer. Scanning electron microscopy data verifies that the anodes with powdered ionomer provide more homogeneous distribution of catalysts and ionomer in the electrode, while dispersed samples have the issues of agglomerates and uneven coverage of catalysts, which could worsen the catalyst utilization and trigger mass transport issues.

[1] Ayers, Katherine, et al. "Perspectives on low-temperature electrolysis and potential for renewable hydrogen at scale." Annual review of chemical and biomolecular engineering 10 (2019): 219-239.

[2] Lee, Sol A., et al. "Anion exchange membrane water electrolysis for sustainable large‐scale hydrogen production." Carbon Neutralization 1.1 (2022): 26-48.

[3] Favero, Silvia, Ifan EL Stephens, and Maria‐Magdalena Titirci. "Anion Exchange Ionomers: Design Considerations and Recent Advances‐An Electrochemical Perspective." Advanced Materials 36.8 (2024): 2308238.

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