IrO_x @In₂ O₃ Heterojunction from Individually Crystallized Oxides for Weak-Light-Promoted Electrocatalytic Water...

Multi-field coupling, especially photo-assisted electrocatalysis, has recently been studied to further improve the oxygen evolution reaction (OER). In this study, an n-type cubic In₂ O₃ semiconductor is employed for the first time to load IrO_x species (Ir-In₂ O₃ mass ratio: 17.6 %). Consequently, the IrO_x @In₂ O₃ heterojunction, which exhibits outstanding OER performance promoted by weak-light irradiation, is formed. Notably, IrO_x (approximately 1.7 nm in size) and In₂ O₃ are observed to crystallize independently during heterogeneous nucleation with no Ir atoms doped in the In₂ O₃ lattice. This avoids Ir loss and ensures the full exposure of all Ir-based sites. The IrO_x @In₂ O₃ heterojunction exhibits enhanced electrocatalytic water oxidation with overpotential values of 190 and 231 mV at current densities of 10 and 50 mA cm^-2 , surpassing all IrO_x -based catalyst results reported to date. Nano-sized IrO_x on the surface, irradiated by the weak-light beam of LED-365 (1.8 mW cm^-2 ), can be fully activated as an OER site. Moreover, the overpotential is further reduced to 176 and 210 mV to deliver the corresponding current. This work is anticipated to aid in the design of more efficient multi-field coupling OER systems.