Optimizing the Electronic Structure of IrOx Sub-2 nm Clusters via Tunable Metal Support Interaction for Acidic Oxygen Evolution Reaction

Abstract

Iridium-based electrocatalysts are the most promising candidates for the acidic oxygen evolution reaction (OER). Considering their high cost and scarcity, it is imperative to maximize atom utilization and enhance the intrinsic activity of iridium. In this work, IrO_x sub-2 nm clusters are stabilized on TiO₂ supports via metal support interaction (MSI) induced by vacancy defects in TiO₂. The strength of MSI is readily tuned by the type of vacancies: oxygen vacancies in TiO₂ (V_O-TiO₂) induce the adsorbed MSI with relatively weak strength, while titanium vacancies in TiO₂ (V_Ti-TiO₂) lead to the strong embedded MSI. The tunable MSI further modulates the electronic structure of IrO_x sub-2 nm clusters. IrO_x/V_O-TiO₂ with adsorbed MSI exhibits an optimized electronic structure with a downshifted d-band center of IrO_x, resulting in a reduced binding energy with oxygen and a low energy barrier of the rate-determining step for OER. Consequently, IrO_x/V_O-TiO₂ delivers an activity twice that of commercial IrO₂ and a good stability for 120 h in a practical proton exchange membrane water electrolyzer. Our study provides a guideline for the rational design of acidic OER catalysts based on modulating the electronic structure of IrO_x sub-2 nm clusters via tunable MSI.