Structure of Iridium Oxides and Their Oxygen Evolution Electrocatalysis in Acidic Media

Lam, Alexandria; Sun, Qiang; Polus, Zachary; Buek, Connor; McCrea, Kellie; Mahoney, Irene; Wegge, Linnea; Zeng, Zhiqiao; McGowan, Michael; Yu, Haoran; Yang, Fan; Valdez, Thomas; Hamdan, Monjid; Jia, Qingying

doi:10.1021/acscatal.5c01659

Structure of Iridium Oxides and Their Oxygen Evolution Electrocatalysis in Acidic Media

Journal Article · Mon May 05 00:00:00 UTC 2025 · ACS Catalysis

DOI:https://doi.org/10.1021/acscatal.5c01659· OSTI ID:2572170

Lam, Alexandria ^[1]; Sun, Qiang ^[2]; Polus, Zachary ^[3]; Buek, Connor ^[2]; McCrea, Kellie ^[2]; Mahoney, Irene ^[2]; Wegge, Linnea ^[2]; Zeng, Zhiqiao ^[2]; McGowan, Michael ^[2]; ^[4]; Yang, Fan ^[2]; Valdez, Thomas ^[2]; Hamdan, Monjid ^[2]; ^[2]

Plug Power, Inc., Concord, MA (United States); Columbia Univ., New York, NY (United States)
Plug Power, Inc., Concord, MA (United States)
Plug Power, Inc., Rochester, NY (United States)
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)

Proton exchange membrane water electrolyzers (PEMWEs) have emerged as one of the most promising technologies for the large-scale production of clean hydrogen. Gigawatt scale deployment of PEMWEs requires substantial reduction in the loading of iridium (Ir), which is one of the most expensive and rarest elements. Substantial reduction in Ir loading calls for the development of innovative Ir-based anodes, which requires a clear understanding of how iridium oxides accelerate the sluggish oxygen evolution reaction (OER) in acidic media. Herein, we studied the structure and OER electrocatalysis of three representative iridium oxides ─ hydrous, amorphous, and rutile ─ by employing a combination of physicochemical and electrochemical characterization. Additionally, we found that the hydrous iridium oxide had a different local structure of IrO₆ octahedra and a superior OER intrinsic activity compared with the other two, and that the OER activities of all three types decreased with decreasing pH of acidic solution. We proposed that the OER process of these iridium oxides is limited by water nucleophilic attack on the OER intermediate oxygenated adsorbates. Based on this mechanism, we attributed the superior OER activity of hydrous iridium oxides to their longer Ir–O bonds and the pH-dependent OER activity of iridium oxides to the pH-dependent oxidation of Ir.

View Accepted Manuscript (DOE)

Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: US Army; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Hydrogen Fuel Cell Technologies Office (HFTO); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)

Grant/Contract Number:: AC05-00OR22725; SC0012704

OSTI ID:: 2572170

Journal Information:: ACS Catalysis, Journal Name: ACS Catalysis Journal Issue: 10 Vol. 15; ISSN 2155-5435

Publisher:: American Chemical Society (ACS)Copyright Statement

Country of Publication:: United States

Language:: English

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