Hydroxylation of IrO2 via La doping enhances oxygen evolution reaction performance for PEM water electrolysis

Rationally designing the catalyst structure is one of the important challenges to improve the activity and stability of IrO₂ in proton exchange membrane water electrolyzer (PEMWE). Herein, we designed a locally crystallized porous IrO₂ composed of crystalline nanoneedles and amorphous IrO_x via La doping and L-cysteine regulation. L-Cysteine promotes the formation of crystalline nanowire structures of IrO_2. The local amorphization induced by La doping helps to improve the adsorption capacity of OH groups, which promoting the transformation of Ir⁴⁺ to Ir⁵⁺, and the interface between crystalline and amorphous phases enhances the catalytic layer by diminishing both mass transport loss and electronic resistance, which improves the OER performance with an overpotential of 245 mV@10 mA·cm⁻². La doping can limit the dissolution of Ir sites in IrO₂-9La, and the surface hydroxylated IrO₂-9La follows the adsorbate evolution mechanism (AEM), which can be stable for more than 140 h at the current density of 10 mA/cm². Moreover, the membrane electrode assembly in single-cell PEMWE based on local amorphization of IrO₂ exhibits high catalytic activity at ampere-level current densities (1.749 V@1 A·cm⁻²) and remains stable for more than 200 h. Our research results provide structural design ideas and methods for improving the activity and stability of IrO₂ under high currents.