IrOx@In2O3 Heterojunction from Individually Crystallized Oxides for Weak‐Light‐Promoted Electrocatalytic Water Oxidation

Abstract 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 In 2 O 3 semiconductor is employed for the first time to load IrO x species (Ir‐In 2 O 3 mass ratio: 17.6 %). Consequently, the IrO x @In 2 O 3 heterojunction, which exhibits outstanding OER performance promoted by weak‐light irradiation, is formed. Notably, IrO x (approximately 1.7 nm in size) and In 2 O 3 are observed to crystallize independently during heterogeneous nucleation with no Ir atoms doped in the In 2 O 3 lattice. This avoids Ir loss and ensures the full exposure of all Ir‐based sites. The IrO x @In 2 O 3 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.