Dual Doping of Ruthenium and Iridium in Octahedral Sites of Spinel Co ₃ O ₄ Nanoflowers for Enhanced PEM Water Electrolysis

In acid proton exchange membrane water electrolysis (PEMWE), exploring highly active and durable oxygen evolution reaction (OER) electrocatalysts remains a great challenge. Herein, a durable Ru and Ir co-doped spinel cobalt oxide (RuIr-Co₃O₄) nanoflower electrocatalyst with low precious metal loading (Ru 2.7 wt% and Ir 0.25 wt%) is designed for acidic water splitting. The RuIr-Co₃O₄ electrocatalyst exhibits low overpotential of 220 mV to deliver 10 mA cm^-2 along with outstanding stability without significant deterioration for 600 h of operation. X-ray absorption spectra analysis indicates an increase in the valence state of the Co site, along with stabilizing the metal-oxygen bond, due to the introduction of both Ru and Ir, thus enhancing catalytic stability. Further, theoretical calculations confirm that the OER reaction process follows the oxygen path mechanism (OPM) with a significantly reduced energy barrier for the rate-determining step than that in the adsorbate evolution mechanism (AEM). Interestingly, the PEM electrolyzers constructed with this anode can deliver a current density of 500 mA cm^-2 at 1.67 V with outstanding stability for continuous 500 h operation at 100 mA cm^-2, showing a great promise toward next-generation green hydrogen energy production.