A robust chromium–iridium oxide catalyst for high-current–density acidic oxygen evolution in proton exchange membrane electrolyzers†

Developing electrocatalysts with superior activity and durability at high current densities is crucial for proton exchange membrane electrolyzers. However, the dissolution of electrocatalysts in oxidative acidic electrolytes results in performance degradation, especially at high current densities. Here, we report a chromium–iridium oxide electrocatalyst with strong coupling interfaces, endowing it with high activity and stability. The electrocatalyst has an ultralow overpotential of 425 mV to reach 2 A cm⁻² for acidic oxygen evolution and operates stably for 100 h with a negligible degradation rate at 1 A cm⁻². A proton exchange membrane electrolyzer using this catalyst needs only 1.63 V to reach 1 A cm⁻² and 1.73 V to reach 2 A cm⁻² under industrial conditions. The corresponding electricity cost of hydrogen production is calculated to be US$0.87 per kg of H₂, which fulfills the requirement of the US Department of Energy by 2026 (US$2.0 per kg of H₂). This work not only introduces a new strategy to produce efficient and stable electrocatalysts, but also indicates their potential use in industrial electrolyzers.