Precious Metal Loading Research Articles

Engineering of lattice defects in supported Cu-Mn-Ce composite oxide catalysts through ultra-low Pd doping and plasma treatment for catalytic oxidation of hexane.

Despite the low cost of supported non-precious metal catalysts, their catalytic activity is significantly lower than that of precious metal catalysts in the catalytic oxidation reaction of volatile organic compounds (VOCs). In order to enhance the catalytic activity of supported non-precious metal catalysts, we introduced an ultra-low loading of palladium into the existing catalytic system and employed a plasma preparation process instead of the conventional impregnation method. The approach significantly improves the catalytic activity of the active sites on the catalyst. The results indicate that, compared to the supported Pd and CuMnCeOx catalysts prepared by conventional impregnation method, the Pd/CuMnCeOx/SiO2-P catalysts prepared via plasma exhibit a higher proportion of lattice defects (oxygen vacancies). Furthermore, the doping of the ultra-low Pd could facilitate the formation of additional lattice defects in the composite oxide. As a result, it can improve the content of surface active oxygen and enhance the adsorptive strength of hexane on the surface of the catalyst. The Pd/CuMnCeOx/SiO2-P catalysts exhibit high catalytic activity and stability in the catalytic oxidation of n-hexane. This work promotes the potential application in the preparation of catalyst with ultra-low precious metal loading.

Baselining Unitized Reversible Fuel Cells with Low Catalyst Loadings: Performance and Durability Insights

Unitized Reversible Fuel Cells (URFCs) combines the functionality of hydrogen fuel cells and water electrolyzers into a single device, offering high energy density for energy conversion and storage. However, their commercial viability is deterred by the high precious group metal (PGM) loadings. Conventional URFCs utilize 1 mg/cm2 of Pt and 1 mg/cm2 of IrO2 in the oxygen electrode, posing economic and sustainability challenges.This study investigates the performance and durability implications of minimizing PGM loadings in oxygen electrode which utilizes a mixture of IrO2 and Pt black to facilitate oxygen evolution and oxygen reduction reaction respectively. We also examine the effect of the porous transport layer (PTL) morphology and wettability on the URFC performance and durability. Accelerated stress test (AST) protocol was developed to evaluate the performance loss across both fuel cell and water electrolyzer mode of URFC operation. Additionally, this research provides a detailed characterization of loss in active area, change in catalyst layer structural, and PTL wettability offering insights into the degradation mechanism in URFCs.This study not only establishes a foundational benchmark for understanding the URFC performance and durability at low catalyst loadings but also highlights the critical need for strategic component selection and activation methods to enhance the system's overall efficiency and durability, marking a significant step towards the realization of more sustainable energy solutions.

Electrospun Micro Porous Layer for Enhanced Proton Exchange Membrane Water Electrolysis

Current porous transport layers (PTLs) utilized in proton exchange membrane water electrolyzers (PEMWEs), suffer from limited interfacial contact area with the catalyst layer which reduces the performance. Although high anode catalyst loadings can mitigate this issue, it contradicts the objective of reducing the loading of precious metals in PEMWEs to lower costs. The combination of poor in-plane conductivity of the anode catalyst and the poor interfacial contact results in increased contact resistance and reduced catalyst utilization which leads to accelerated catalyst degradation due to non-uniform exposure to the applied voltage or current in the catalyst. Micro-porous layers (MPLs) can alleviate the interfacial contact problem. MPLs provide with high surface areas and low pore size, facilitating enhanced contact with the catalyst layer and improving catalyst utilization. Furthermore, the hierarchical MPL morphology can aid in efficient oxygen removal and enhanced water transport to the anode catalyst layer.In this study, titanium-based MPLs were fabricated via electrospinning employing a titanium precursor and a carrier polymer. Electrospun offers a superior control on the morphology of the resulting fibers. The electrospun fibers were subsequently calcined to yield TiO2 fibers, forming the MPL. The MPL was then integrated into a commercial felt based PTL substrate through hot-pressing and sintering to enhance the improved integration between the MPL and substrate. We will present the electrochemical performance evaluation including polarization curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. Surface characterization of the MPL and catalyst layer surface was performed via scanning electron microscopy (SEM) and laser profilometry before and after electrolyzer testing.AcknowledgementThis research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium. Program manager Dave Peterson and Mackenzie Hubert.

Tailoring Electrolyzer Catalyst Layer Morphology Via Pore Network Modelling

Polymer electrolyte membrane (PEM) water electrolysis is a key technology to produce clean, high purity hydrogen, which can serve as an alternative to carbon-based fuels. However, PEM electrolyzer uptake has been sluggish due to high catalyst costs, which can contribute to up to 47% of total stack costs [1]. Thus, to lower stack costs, the morphology of the catalyst layer must be optimized towards lower precious metal loadings. However, catalyst layer morphology optimization remains a challenge, as the mechanisms linking catalyst morphology to mass and charge transport remain ambiguous in the literature [2], [3]. While the morphology of porous transport layer (PTL) has been extensively explored via stochastic material generation and pore network modelling techniques [4], such an analysis must also be extended to the catalyst layer to design efficient, low-cost materials.In this work, we introduce a method to replicate the pore structure of commercially available PEM electrolyzer catalyst layers using stochastic generation techniques. Our method employs a custom divider to combine regions of varying pore sizes and effectively replicate the range of catalyst layer pore sizes observed in commercial materials. Moreover, we demonstrate that the pore size distribution of stochastically generated materials is statistically indistinguishable from imaged catalyst samples. Pore network modelling techniques were further applied to stochastically generated morphologies to evaluate electrical and mass transport properties. We not only reveal that the transport properties of our stochastically generated materials fall within experimentally measured ranges, but also reveal how tailoring pore size distributions can enhance these properties. The findings from our analysis can be used to identify desirable catalyst morphology targets for manufacturing and enhance the accuracy of electrolyzer transport models via the estimation of catalyst layer transport properties.[1] A. Mayyas, M. Ruth, et al., Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers, United States (2019).[2] Z. Taie, X. Peng, et al., ACS Appl. Mater. Interfaces, 12, 47, 52701–52712 (2020).[3] J. Lopata, Z. Kang, et al., J. Electrochem. Soc., 167. 064507 (2020).[4] J. K. Lee, C. H. Lee, and A. Bazylak, J. Power Sources, 437, 226910 (2019).

Controlling Flooding and Parameter Sensitivity in an Anion Exchange Membrane Fuel Cell Using a Triblock Copolymer Membrane and Matched Ionomers

While there has been much interest in the proton exchange membrane (PEM) fuel cell, its wide spread use has been restricted by cost, durability, fuel versatility issues, and the environmental consequences of using perfluorosulfonic acid polymers as the membrane and ionomer. This is primarily because catalyst based on Pt are nessecary in a PEM fuel cell on both the anode and the cathode and reactive oxygen species chemically degrade the cell. Alkaline catalysis in fuel cells has been demonstrated with non-precious metal catalysts, and a variety of fuels beyond H2 and methanol. Alkaline fuel cells (AFCs), based on aqueous solutions of KOH, have serious drawbacks associated with system complexity, low system power densities and carbonate formation. Anion exchange membrane (AEMs) fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs. Great strides have been made in ionic conductivity and durability in AEMs and fuel cells with reduced precious metal loadings have been demonstrated. However, AEM fuel cells have significant water management issues, as water is both a reactant and a product leading to flooding and control issues.We have developed a triblock copolymer Poly (vinylbenzyl-N-methylpiperidinium carbonate)-b-polyethylene-b-poly(vinylbenzyl-N-methylpiperidinium carbonate)as a robust, high performance, durable, and scalable AEM. We have modified the block ratios and ion exchange capacity of this material to show excellent performance and durability in both electro-desalination and water electrolysis. Despite the materials potential, we have only occasionally tested it as a fuel cell membrane. We have now begun to throughly evaluated the material in 5 cm2 H2/O2 fuel cell. Initial experiments showed good potential performance but were hampered by severe flooding of the electrodes. We will present a materials approach to solving this problem by investigating various related ionomers in the electrodes. Both variations of the polymer used to fabricate the membrane and a random co-polymer derived from polymethylbutylene and poly(vinylbenzyl-N-methylpiperidinium) were investigated. The effect of loading and ionomer ion exchange capacity on the performance of the fuel cell and the relationship between these properties will be reported.

Ultra-Low Loaded Platinum Via Plasma-Enhanced Atomic Layer Deposition for the Fuel Electrode Active Layer in Steam Reversible Solid Oxide Cells

Reversible solid oxide cells (rSOCs) are crucial energy devices in sustainable energy systems, offering efficient energy conversion and storage solutions through hydrogen. Conventional SOFC/SOEC operating temperatures are above 700°C; at these temperatures, the cells benefit from high energy conversion efficiencies due to facilitated electrochemical reactions and effective waste heat utilization. Despite their advantages, commercial rSOCs face hurdles including suboptimal performance in the intermediate temperature range of 500-700°C, limited lifespan, and elevated operational costs. Addressing these issues, significant progress has been made in electrode fabrication, particularly through advanced semiconductor fabrication methods such as atomic layer deposition (ALD).In this study, we explore the application of plasma-enhanced ALD (PEALD) for depositing exceptionally low loadings of platinum on Ni-yttria stabilized zirconia (Ni-YSZ) fuel electrodes, aiming to enhance both performance and stability. Employing this novel approach, we achieved precise control over the Pt nanoparticle deposition process, resulting in a catalyst loading of only 0.2 µg/cm2.Experimental results demonstrated that rSOC samples with 10 cycles of PEALD Pt exhibited a 20% increase in maximum power density (548 vs. 479 mW/cm2 at 700°C) and an 18% increase in current density (1260 vs. 1070 mA/cm2 at 1.5 V) compared to the bare samples. Notably, these improvements were achieved without any observable performance degradation over 50 hours of operation at 700°C with 50% humidified hydrogen. Density functional theory (DFT) simulations were employed to elucidate the mechanisms contributing to the enhanced activity, revealing that the nano-scale Pt deposition promotes efficient hydrogen oxidation and evolution reactions.These findings highlight the potential of PEALD for rSOC manufacturing, enabling the creation of highly active and stable electrodes with minimal precious metal loading. The outcomes of this study suggest that such advancements could lead to more economically viable and sustainable hydrogen energy solutions, aligning with broader goals of energy security and environmental sustainability. This work provides a compelling case for the wider application of nano-engineered catalysts in high-performance electrochemical systems at intermediate temperature ranges.

Electrospun Pt Nanowires as a Highly Conductive Support for Ir for the Electrochemical Oxygen Evolution Reaction

The electrochemical Oxygen Evolution Reaction (OER) is a critically important reaction towards realizing a sustainable energy economy through the utilization of hydrogen as an environmentally friendly fuel. However, the relatively low conductivity of conventional IrOx catalysts hinders their performance and necessitates use of high Ir loadings.[1, 2] To counteract this insufficiency, utilizing highly conductive catalyst layer supports has become an effective strategy for maintaining optimal conductivity.[3-7] While they have allowed for improved stability, TiO2-based fibers typically possess poor conductivity. Thus, the inclusion of an additional components (Pt, Nb, Au, etc.) has been shown to improve the catalyst layer conductivity, thereby enhancing the OER activity for this class of catalyst.[8, 9] Herein, we utilize electrospinning as a method for producing conductive Pt-based nanowires with customizable porosity and diameter on the scale of tens of nanometers to be utilized as a support for active Ir-based catalysts. By controlling the electrospinning solution and operating parameters, the characteristics of as-spun Pt-CNFs may be controlled before high-temperature treatment to obtain Pt-NWs with regulated diameter.[10] Following the fabrication of Pt-NWs, we analyze the electrochemical performance and properties of the resulting Ir@Pt-NWs electrocatalyst.AcknowledgmentFinancial support from the Laboratory Directed Research and Development Program at Los Alamos National Laboratory through project 20240061DR is gratefully acknowledged.References Fu, C., et al., Metallic-Ir-based anode catalysts in PEM water electrolyzers: Achievements, challenges, and perspectives. Current Opinion in Electrochemistry, 2023. 38: p. 101227.Moriau, L., et al., Supported Iridium-based Oxygen Evolution Reaction Electrocatalysts - Recent Developments. ChemCatChem, 2022. 14(20): p. e202200586.Bele, M., et al., Towards Stable and Conductive Titanium Oxynitride High-Surface-Area Support for Iridium Nanoparticles as Oxygen Evolution Reaction Electrocatalyst. ChemCatChem, 2019. 11(20): p. 5038-5044.Bernsmeier, D., et al., Oxygen Evolution Catalysts Based on Ir–Ti Mixed Oxides with Templated Mesopore Structure: Impact of Ir on Activity and Conductivity. ChemSusChem, 2018. 11(14): p. 2367-2374.Chueh, L.-Y., et al., WOx nanowire supported ultra-fine Ir-IrOx nanocatalyst with compelling OER activity and durability. Chemical Engineering Journal, 2023. 464: p. 142613.Bernicke, M., et al., Tailored mesoporous Ir/TiOx: Identification of structure-activity relationships for an efficient oxygen evolution reaction. Journal of Catalysis, 2019. 376: p. 209-218.Karade, S.S., et al., IrO2/Ir Composite Nanoparticles (IrO2@Ir) Supported on TiNxOy Coated TiN: Efficient and Robust Oxygen Evolution Reaction Catalyst for Water Electrolysis. ChemCatChem, 2023. 15(4): p. e202201470.Regmi, Y.N., et al., Supported Oxygen Evolution Catalysts by Design: Toward Lower Precious Metal Loading and Improved Conductivity in Proton Exchange Membrane Water Electrolyzers. ACS Catalysis, 2020. 10(21): p. 13125-13135.Hu, W., S. Chen, and Q. Xia, IrO2/Nb–TiO2 electrocatalyst for oxygen evolution reaction in acidic medium. International Journal of Hydrogen Energy, 2014. 39(13): p. 6967-6976.Shui, J. and J.C.M. Li, Platinum Nanowires Produced by Electrospinning. Nano Letters, 2009. 9(4): p. 1307-1314. Figure 1

Porous transport layers with low Pt loading having Nb–Ta alloy as interlayer for proton exchange membrane water electrolyzers

Titanium (Ti), commercially used as substrate for porous transport layers (PTLs) in proton exchange membrane water electrolyzers (PEMWEs), tends to form passivating oxide layer, increasing interfacial contact resistance (ICR) and reducing performance and durability; practice of using precious metal coatings for mitigation significantly increases costs. This study investigates niobium-tantalum (Nb–Ta) alloys as cost-effective interlayer coatings on Ti-felt to reduce precious metal loading. Nb–Ta coated samples significantly increase corrosion potential, lower current densities by 3–4 orders of magnitude, reduce ICR by 3.5 times, and improve durability. The best performance sample with an ultra-low amount of platinum, shows 8 times greater durability, 12.5% reduction in ohmic resistance and 28% increase in current density at +2.0 V than the commercial PTL in a single cell stack. Improved contact angle, electrical, and thermal conductivity highlight Nb–Ta interlayer coatings for PTLs, offering a cost-effective strategy to enhance PEMWE performance and durability for green hydrogen production.

Emission control in a dual fuel low temperature combustion engine at intermediate loads

Intermediate to high load operation in dual fuel reactivity controlled compression ignition (RCCI) techniques is restricted due to uncontrolled combustion that causes engine knocking. Dual fuel strategies with advanced pilot injection and near-top dead center (TDC) main injection timings are reported to enhance combustion control, albeit with increased soot emissions, reduction of thermal efficiency, and emergence of an intricate trade-off between total hydrocarbon (THC) and oxides of nitrogen (NOx) emissions. In order to address these conflicting issues, an intermediate engine load, corresponding to 6 bar gross indicated mean effective pressure at 1500 and 2200 rev/min engine speeds was investigated in this work. The main objectives of this work are (1) to obtain combination of control parameters to achieve near-zero engine-out NOx and soot emissions and high thermal efficiency while minimizing THC and CO emissions; (2) to understand the effectiveness of diesel oxidation catalysts (DOCs) for the oxidation and reduction of exhaust gas species in the dual fuel mode; and (3) to understand the oxidation characteristics of the soot generated from the dual fuel mode. Optimum dual fuel low temperature combustion strategies, in terms of diesel injection timings, quantity and exhaust gas recirculation levels, were identified using the statistical multi response signal to noise (MRSN) ratio method in which NOx, soot and indicated efficiency were response variables. The performance of commercial DOCs, with different precious metal (Pt and/or Pd) loadings, were also studied at optimum dual fuel strategies for gasoline-diesel dual fuel operations. High DOC outlet temperatures (>∼340°C), due to the exotherm generated by the oxidation of high concentrations of THC and carbon monoxide (CO) emissions from dual fuel operations, resulted in greater than 90% THC conversion efficiency. The exotherm decreased the nitric oxide (NO) oxidation whereas the nitrogen dioxide (NO2) reduction reactions were favored over the DOC in the dual fuel mode at the intermediate load operating condition. Thermogravimetric analysis of the soot showed higher activation energy (177.2 kJ/mol), formed at the dual fuel optimum condition, relative to the activation energy (162.7 kJ/mol) of the soot formed in conventional diesel combustion (CDC).

Niobium Interlayer Coating: Is it a Practical Approach to Tune the Protective Pt Loading in PEM Water Electrolyzers?

Proton exchange membrane (PEM) water electrolysis is a pioneering and promising method for sustainable green hydrogen generation. However, the high cost of PEM water electrolyzer components poses a significant barrier to the commercialization and widespread application of this technology. In this research, a novel Niobium-Platinum coating is developed for the porous transport layer (PTL) to reduce the precious metal loading. Niobium (Nb)-based coating was applied as an interlayer between Pt and titanium (Ti) felt substrates to increase the adhesion of Pt. For this study, pulsed laser deposition (PLD) technique was applied for the first time to coat Nb and Pt multilayers onto Ti felt substrates. The results demonstrate that incorporating a Nb coating as an interlayer lead to reducing the Pt loading, which holds promise for the practical application of PTLs in PEM water electrolyzers.

Low loading of Pt on MoB Constructed by microwave Quasi-solid approach with solvent Regulation for hydrogen evolution reaction

The interaction between metal nanoclusters and the carrier can enhance the electron transfer rate to optimize the hydrogen evolution reaction (HER) performance, but the common synthesis approaches often lead to metal particle agglomeration, and then blocking active sites. Herein, highly-dispersed Pt nanoclusters supported onto molybdenum boride (MoB) is developed through microwave approach with various solvent to regulate the catalytic performance. The synthesized electrocatalyst with the addition of methanol (Pt/MoB-M) exhibits excellent electrocatalytic performance towards HER with low overpotential (13 mV at 10 mA cm−2), small Tafel slope (24 mV dec−1), and high mass activity (10.06 A/mgPt at 50 mV). This work presents a novel approach to prepare highly-efficient electrocatalysts for renewable energy-related applications of non-carbon supported low loading of precious metals.

Isolated Octahedral Pt-Induced Electron Transfer to Ultralow-Content Ruthenium-Doped Spinel Co3O4 for Enhanced Acidic Overall Water Splitting.

The development of a highly active and stable oxygen evolution reaction (OER) electrocatalyst is desirable for sustainable and efficient hydrogen production via proton exchange membrane water electrolysis (PEMWE) powered by renewable electricity yet challenging. Herein, we report a robust Pt/Ru-codoped spinel cobalt oxide (PtRu-Co3O4) electrocatalyst with an ultralow precious metal loading for acidic overall water splitting. PtRu-Co3O4 exhibits excellent catalytic activity (1.63 V at 100 mA cm-2) and outstanding stability without significant performance degradation for 100 h operation. Experimental analysis and theoretical calculations indicate that Pt doping can induce electron transfer to Ru-doped Co3O4, optimize the absorption energy of oxygen intermediates, and stabilize metal-oxygen bonds, thus enhancing the catalytic performance through an adsorbate-evolving mechanism. As a consequence, the PEM electrolyzer featuring PtRu-Co3O4 catalyst with low precious metal mass loading of 0.23 mg cm-2 can drive a current density of 1.0 A cm-2 at 1.83 V, revealing great promise for the application of noniridium-based catalysts with low contents of precious metal for hydrogen production.

Insights to the differences in catalytic performance of under-rib and under-channel regions for PEM water electrolysis

The difference in catalyst utilization in different regions of proton exchange membrane electrolyzer cell (PEMEC) is often overlooked, yet it holds significant implications for understanding the electrochemical reactions in electrolysis and designing novel electrode structures. In this study, we creatively designed catalyst coated membrane (CCM) with non-uniform distribution of catalytic layers in the under-rib and under-channel regions. Combined with the gradient design method of catalytic layers, the electrochemical reactions in the different regions were explored experimentally. The difference in reactant supply between the under-rib and under-channel catalytic layer was revealed by the water starvation experiment. Moreover, a three-dimensional two-phase non-isothermal model was constructed to study the differences in the current density distribution between ribs and channels. The results show that the current density under the rib is higher than under the channel. At the rib: channel catalyst loading of 3:1, the CCM performance is optimal. Based on the findings, the CCM with non-uniform, gradient catalytic layer was designed, which can achieve an 18.33 % reduction in precious metal loading without significant performance loss. This study reveals the genuine differences in catalysis reactions within PEMEC, thus providing new insights for realizing the electrode designs with high electrolysis performance and low catalyst loading.

Advanced Porous Transport Electrode for High-Performance Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolyzers (PEMWEs) hold great potential for supplying green hydrogen to support extensive energy storage and mobility in a future energy landscape centered on renewable energy sources.1,2 However, their contribution to global hydrogen production is currently limited, mainly due to their comparatively high cost.3 To improve the economic competitiveness of green hydrogen and foster broader market penetration, the Department of Energy (DOE) has launched the Hydrogen Earthshots, aiming for a substantial cost reduction to $2 per kilogram by 2025 and $1 per kilogram for green hydrogen by 2030.4 The high efficiency and prolonged durability are pivotal for the overall performance and cost reduction of the PEMWEs. This requires careful consideration of the interfacial contact between the porous transport layer (PTL) and the anode catalyst layer.5 One option for PEMWEs is to directly coat the anode catalyst layer onto the PTL, forming porous transport electrodes (PTEs). Recent literature suggests that it is feasible to manufacture PTEs with low precious metal loading, demonstrating both high performance and durability.6,7 In this study, an innovative reactive spray deposition technology (RSDT) is used to fabricate PTEs with low PGM loading (0.2 - 0.3 mgPGM cm-2) in both catalyst layers. The RSDT is a flame-based method that combines the synthesis and deposition of the catalyst in a single step, significantly reducing the fabrication time and cost of the membrane electrode assembly (MEA).8–11 The RSDT-fabricated PTEs are coupled with various membranes, and their performance has been assessed and compared to the state-of-the-art MEAs for PEMWEs. In addition, the performance loss in each cell has been studied and discussed in detail. Furthermore, a standard accelerated stress test (AST) protocol has been applied to assess the durability of the RSDT-fabricated MEAs, with one order of magnitude lower PGM loading in their catalyst layers in comparison to the commercial MEAs for PEMWEs.Reference1. Pham, C. Van, Escalera-López, D., Mayrhofer, K., Cherevko, S. & Thiele, S. Essentials of High Performance Water Electrolyzers – From Catalyst Layer Materials to Electrode Engineering. Adv. Energy Mater. 11, (2021).2. Carmo, M., Fritz, D. L., Mergel, J. & Stolten, D. A comprehensive review on PEM water electrolysis. Int. J. Hydrogen Energy 38, 4901–4934 (2013).3. Buttler, A. & Spliethoff, H. Current status of water electrolysis for energy storage, grid balancing, and sector coupling via power-to-gas and power-to-liquids: A review. Renew. Sustain. Energy Rev. 82, 2440–2454 (2018).4. Styapal, S. et al. DOE Update on Hydrogen Shot, RFI Results, and Summary of Hydrogen Provisions. (2021).5. Peng, X. et al. Insights into Interfacial and Bulk Transport Phenomena Affecting Proton Exchange Membrane Water Electrolyzer Performance at Ultra-Low Iridium Loadings. Adv. Sci. 8, (2021).6. Xie, Z. et al. Ionomer-free nanoporous iridium nanosheet electrodes with boosted performance and catalyst utilization for high-efficiency water electrolyzers. Appl. Catal. B Environ. 341, 123298 (2024).7. Lee, J. K. et al. Ionomer-free and recyclable porous-transport electrode for high-performing proton-exchange-membrane water electrolysis. Nat. Commun. 14, 1–11 (2023).8. Zeng, Z. et al. Advanced nickel-based catalysts for the hydrogen oxidation reaction in alkaline media synthesized by reactive spray deposition technology: Study of the effect of particle size. Int. J. Hydrogen Energy 1–12 (2023) doi:10.1016/j.ijhydene.2023.03.249.9. Zeng, Z. et al. Degradation Mechanisms in Advanced MEAs for PEM Water Electrolyzers Fabricated by Reactive Spray Deposition Technology. J. Electrochem. Soc. 169, 054536 (2022).10. Xing, J. et al. Long-term durability test of highly efficient membrane electrode assemblies for anion exchange membrane seawater electrolyzers. J. Power Sources 558, 232564 (2023).11. Mirshekari, G. et al. High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment. Int. J. Hydrogen Energy 46, 1526–1539 (2021).

IrO2 Oxygen Evolution Catalysts Prepared by an Optimized Photodeposition Process on TiO2 Substrates.

Preparing high-performance oxygen evolution reaction (OER) catalysts with low precious metal loadings for water electrolysis applications (e.g., for green hydrogen production) is challenging and requires electrically conductive, high-surface-area, and stable support materials. Combining the properties of stable TiO2 with those of active iridium oxide, we synthesized highly active electrodes for OER in acidic media. TiO2 powders (both commercially available Degussa P-25® and hydrothermally prepared in the laboratory from TiOSO4, either as received/prepared or following ammonolysis to be converted to titania black), were decorated with IrO2 by UV photodeposition from Ir(III) aqueous solutions of varied methanol scavenger concentrations. TEM, EDS, FESEM, XPS, and XRD measurements demonstrate that the optimized version of the photodeposition preparation method (i.e., with no added methanol) leads to direct deposition of well-dispersed IrO2 nanoparticles. The electroactive surface area and electrocatalytic performance towards OER of these catalysts have been evaluated by cyclic voltammetry (CV), Linear Sweep Voltammetry (LSV), and Electrochemical Impedance Spectroscopy (EIS) in 0.1 M HClO4 solutions. All TiO2-based catalysts exhibited better mass-specific (as well as intrinsic) OER activity than commercial unsupported IrO2, with the best of them (IrO2 on Degussa P-25® ΤiO2 and laboratory-made TiO2 black) showing 100 mAmgIr-1 at an overpotential of η = 243 mV. Chronoamperometry (CA) experiments also proved good medium-term stability of the optimum IrO2/TiO2 electrodes during OER.

Advanced polymer electrolyte membrane water electrolysis for power to gas applications

Abstract Water electrolysis fed by renewable energy is the foremost technology to generate green hydrogen. Relevant challenges regard decrease of precious metal loadings and performance enhancement while maintaining cutting edge efficiency. Next generation electrolysers must provide dynamic behaviour to improve grid-balancing services and thus integrate with the grid the intermittent renewable energy sources. The HPEM2GAS project developed a low-cost optimised PEM electrolyser for grid management through both stack and balance of plant innovations.

Simultaneously improving the pore structure and electron conductive network of the anode catalyst layer via SnO2 doping for proton exchange membrane water electrolysis.

Proton exchange membrane water electrolysis (PEMWE) is a promising technology for green hydrogen production. However, its large-scale commercial application is limited by its high precious metal loading, because low catalyst loading leads to reduced electron transport channels and decreased water transportation, etc. Herein, we study the electrode level strategy for reducing Ir loading by the optimization of the micro-structure of the anode catalyst layer via SnO2 doping. The pore structure and electron conductive network of the anode catalyst layer can be simultaneously improved by SnO2 doping, under appropriate conditions. Therefore, mass transfer polarization and ohmic polarization of the single cell are reduced. Moreover, the enhanced pore structure and improved electron conduction network collectively contribute to a decreased occurrence of charge transfer polarization. By this strategy, the performance of the single cell with the Ir loading of 1.5 mg cm-2 approaches the single cell with the higher Ir loading of 2.0 mg cm-2, which means that SnO2 doping saves about 25% loading of Ir. This paper provides a perspective at the electrode level to reduce the precious metal loading of the anode in PEMWE.

Tailoring surface morphology on anatase TiO2 supported Au nanoclusters: implications for O2 activation.

Strong interaction between the support surface and metal clusters activates the adsorbed molecules at the metal cluster-support interface. Using plane-wave DFT calculations, we precisely model the interface between anatase TiO2 and small Au nanoclusters. Our study focusses on the adsorption and activation of oxygen molecules on anatase TiO2, considering the influence of oxygen vacancies and steps on the surface. We find that the plane (101) and the stepped (103) surfaces do not support O2 activation, but the presence of oxygen vacancies results in strong adsorption and O-O bond length elongation. Modifying the TiO2 surface with supported small Au n nanoclusters (n = 3-5) also significantly enhances O2 adsorption and stretches the O-O bond. We observe that manipulating the cluster orientation through discrete rotations results in improved O2 adsorption and promotes charge transfer from the surface to the molecule. We propose that the orientation of the supported cluster may be manipulated by making the cluster adsorb at the step-edge of (103) TiO2. This results in activated O2 at the cluster-support interface, with a peroxide-range bond length and a low barrier for dissociation. Our modeling demonstrates a straightforward means of exploiting the interface morphology for O2 activation under low precious metal loading, which has important implications for electrocatalytic oxidation reactions and the rational design of supported catalysts.

Ultralow-content Pt nanodots/Ni3Fe nanoparticles: interlayer nanoconfinement synthesis and overall water splitting.

Minimizing precious metal loading into electrocatalysts for water splitting is vital to promoting hydrogen energy technology toward practical applications. Low-content loading of precious-metal electrocatalysts is achieved by decorating precious metal nanostructures on co-electrocatalysts typically via surface confinement. Here, an electrocatalyst of ultralow-content Pt nanodots (0.71 wt%)/Ni3Fe nanoparticles on reduced oxidation graphene (Pt/Ni3Fe/rGO) is constructed for overall water splitting by pyrolyzing a single-source precursor PtCl63- guest-intercalated MgNiFe-layered double hydroxide (MgNiFe-LDH) host via a distinctive interlayer confinement. Consequently, Pt/Ni3Fe/rGO demonstrates attractive overpotentials of 240 and 76 mV at 10 mA cm-2 for the oxygen and hydrogen evolution reactions (OER and HER), respectively, outperforming those of its /Ni3Fe/rGO counterpart. Moreover, the Pt/Ni3Fe/rGO∥Pt/Ni3Fe/rGO electrolyzer generates a current density of 10 mA cm-2 at 1.55 V, with a retention of 92.4% after 50 h. Furthermore, the measured specific activity and low transfer resistance, as well as the density functional theory (DFT) calculations, indicate that the active Pt/Ni3Fe in Pt/Ni3Fe/rGO can optimize the adsorption/desorption of reaction intermediates and thus boost OER/HER kinetics, all of which lead to enhanced performance. The results demonstrate that such an interlayer confinement-based synthesis strategy can allow for the design of cost-effective precious nanodots as potential electrocatalysts.

Transient Characteristics of the Low-Temperature PEMFC: A Comparative Analysis Using a Physics-Based Model

Low-temperature proton exchange membrane fuel cells (LT-PEMFCs) have experienced a considerable technological leap in the last few decades for transportation and stationary applications. Specifically, the precious metal loading in the catalyst layers (CLs) is notably decreased while enhancing the overall cell performance.1 However, the durability and cost remain major factors that affect the widespread commercialization of the LT-PEMFC. Though this can be achieved with further material development, some existing issues may be resolved by implementing effective design and control strategies. A good understanding of fuel cell water dynamics is required to improve durability and performance. Although some dynamic characteristics can be observed from the experiments, a physics-based model of the LT-PEMFC is necessary to study in-depth transient responses under various conditions like current profiles, operating temperatures, pressure, and humidification levels. Lately, the transient analysis of the fuel cell has gained more attention to elucidate the complex transport phenomena.2 Several transient models of the LT-PEMFC are reported to capture the two-phase behavior inside the cell. Usually, these models are 1D, 2D, or single channel 3D with assumptions like isothermal operation, vapor-equilibrated membrane, simplified reaction kinetics, and more.3–5 Hence, they do not provide spatio-temporal insights into the cell performance containing water dynamics with various flow configurations.The current study focuses on a transient physics-based model of the LT-PEMFC for dynamic analysis across its thickness and flow channels. The membrane used in LT-PEMFC requires humidification to enhance the ionic conductivity and function properly.6 This study considers Schroeder’s paradox for the membrane, which exhibits a different water uptake behavior in the presence of saturated water vapor and liquid water.7 The water uptake property is strongly dependent on the temperature. Therefore, we have developed a single polynomial expression for the membrane water uptake, including temperature and water activity dependency. Using the governing equations & empirical correlations from the numerical and experimental studies, we develop a comprehensive 3D, multiphase, non-isothermal, transient physics-based model of the LT-PEMFC that can closely approximate the liquid water transport under various operating conditions. It is a Multiphysics model that couples electrochemical reactions, porous media flow, transport of reactant species, liquid water transport, heat generation, charge transfer, and ionomer water transport. COMSOL Multiphysics is used to solve the model. It provides a spatio-temporal water distribution inside the membrane, CL, microporous layer, gas diffusion layer, and flow channels. Experiments are performed on 32 cm2 LT-PEMFC with the hybrid flow configuration at 75 °C and 80% RH to validate the physics-based model in the steady state condition. The validation study suggests that the present multiphase model estimates the LT-PEMFC performance with an acceptable RMS current density error of 15 mA/cm2. The simulations are operated in the Galvano-dynamic mode, and the corresponding LT-PEMFC response for the hybrid configuration is shown in Figure 1(a) at various operating pressures. Also, the preliminary results of the liquid water saturation under the channel and rib are incorporated in Figure 1(b). It shows that the water accumulation under the rib is more than the channel due to lower local temperature and weaker convection under the rib, promoting water vapor condensation. Further, the comparison between hybrid and parallel configurations is performed and illustrated in this presentation. Another objective is to study how quickly the liquid water saturation and membrane water content react upon changing the load cycle, RH, operating temperature, and flow configuration. This work is an important step toward understanding the impact of various flow configurations and operating conditions on the water dynamics and membrane water content inside the LT-PEMFC. The developed physics-based model would be extended further by considering the membrane deformation due to the shrinking-swelling under the humidification and thermal cycling, which is critical for the performance and degradation.