Leaching-Induced Ti Trapping Stabilizes Amorphous IrO_x for Proton Exchange Membrane Water Electrolysis

Transition metal nitrides are promising conductive support materials in oxygen evolution reaction (OER), whereas it is unclear if their electrochemical oxidation during prolonged test would affect the OER catalysts. Herein, we demonstrate that the leaching-induced Ti trapping effect from TiN supports effectively stabilizes the electrochemically oxidized amorphous IrO_x catalyst. Structural characterizations reveal that the TiN support experiences severe leaching during OER test, leaving minor amounts of Ti-O species trapping on IrO_x clusters, which mitigate the overoxidation of Ir(III) species and elongate the Ir-O bonds. This leads to 70% reduction of lattice oxygen oxidation and the substantially reduced Ir leaching. Additionally, self-thickening of the catalyst layers is found during proton exchange membrane water electrolysis (PEMWE), enabling an ultralow catalyst loading of 87 µg_Ir cm^-2 to obtain a stable operation at 1.0 A cm^-2 for 500 h. This work deepens the understanding of TiN-supported catalysts for long-term stable OER electrocatalysis.