Simultaneous activity and stability gains in PEM electrolyzer via targeted Cr ³⁺ occupation in spinel Co ₃ O ₄ octahedral lattices

Abstract Iridium-based materials are less studied in proton exchange membrane water electrolyzers (PEMWEs), which are crucial for the generation of green hydrogen, due to their rarity and high cost. Herein, doping Cr with cobalt oxide resulted in rich oxygen vacancies with the Co2+/Cr3+ redox couples and surface hydroxyl groups, which considerably enhance the capacity of the material to adsorb and activate oxygen intermediates. Due to its structural and electrical characteristics, CrCo8Ox has proven to be a stable and effective catalyst for acidic oxygen evolution reaction (OER) and high-performance PEMWEs applications. A high current density of 100 mA·cm−2 was attained by the CrCo8Ox anode catalyst and maintained for 130 h, whereas a current density of 300 mA·cm−2 was maintained for 20 h. In situ Fourier transform infrared (FT-IR) spectroscopy combined with density functional theory (DFT) calculations corroborate the oxide path mechanism (OPM) over pristine Co3O4 rather than the associative electron mechanism (AEM) over Cr-doped CrCo8Ox composites. Such outstanding results indicate a bright future for industrial deployment and provide broad recommendations for developing PEMWEs with high efficiency.