Impact of Nickel on Iridium-Ruthenium Structure and Activity for the Oxygen Evolution Reaction under Acidic Conditions
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Proton exchange membrane water electrolysis (PEMWE) is a promising technology to produce hydrogen directly from renewable electricity sources due to its high power density and potential for dynamic operation. Widespread application of PEMWE is, however, currently limited due to high cost and low efficiency, for which high loading of expensive iridium catalyst and high OER overpotential, respectively, are important reasons. In this study, we synthesize highly dispersed IrRu nanoparticles (NPs) supported on antimony-doped tin oxide (ATO) to maximize catalyst utilization. Furthermore, we study the effect of adding various amounts of Ni to the synthesis, both in terms of catalyst structure and OER activity. Through characterization using various X-ray techniques, we determine that the presence of Ni during synthesis yields significant changes in the structure of the IrRu NPs. With no Ni present, metallic IrRu NPs were synthesized with Ir-like structure, while the presence of Ni leads to the formation of IrRu oxide particles with rutile/hollandite structure. There are also clear indications that the presence of Ni yields smaller particles, which can result in better catalyst dispersion. The effect of these differences on OER activity was also studied through rotating disc electrode measurements. The IrRu-supported catalyst synthesized with Ni exhibited OER activity of up to 360 mA mgPGM-1 at 1.5 V vs RHE. This is ∼7 times higher OER activity than the best-performing IrOx benchmark reported in the literature and more than twice the activity of IrRu-supported catalyst synthesized without Ni. Finally, density functional theory (DFT) calculations were performed to further elucidate the origin of the observed activity enhancement, showing no improvement in intrinsic OER activity for hollandite Ir and Ru compared to the rutile structures. We, therefore, hypothesize that the increased activity measured for the IrRu supported catalyst synthesized with Ni present is instead due to increased electrochemical surface area.
Original language | English |
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Journal | ACS Materials Au |
DOIs | |
Publication status | E-pub ahead of print - 2024 |
Bibliographical note
Funding Information:
Part of this study was performed in the RECYCALYSE project which has received funding from the European Union\u2019s Horizon 2020 research and innovation program under grant agreement No. 861960. It was further supported by the Danish National Research Foundation in the Center for High Entropy Alloy Catalysis (CHEAC) DNRF 149. We acknowledge MAX IV Laboratory for time on DanMAX under Proposal 20220789. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496. DanMAX is funded by the NUFI grant no. 4059-00009B. We would like to thank Mads Ry J\u00F8rgensen and Innokenty Kantor at DanMAX for their contributions in performing the PDF measurements. Thanks also to beamline scientist Dr. Adam H. Clarke at the SuperXAS beamline for performing ex situ XAS measurements at the Swiss Lightsource (SLS) at PSI, Villingen/Switzerland, through a send-in service. We also acknowledge access to the Microscopy Imaging Center (MIC) facilities of the University of Bern.
Publisher Copyright:
© 2024 The Authors. Published by American Chemical Society.
- alloyed iridium catalysts, amorphous iridium, hollandite iridium, oxygen evolution reaction, platinum group metal minimization, Proton exchange membrane water electrolysis, supported iridium catalysts
Research areas
ID: 395997899