High-Density Iridium Single Atoms on Vanadium-Doped TiO2 for Electrochemical Water Oxidation Catalysis

Abstract Water oxidation in proton exchange membrane water electrolysis (PEMWE) uses IrO2 nanoparticles supported on corrosion-resistant TiO2. However, the low conductivity of TiO2 imposes electronic transport limitations that necessitate high Ir loadings for effective catalysis. Here, we present a catalyst design strategy that couples a heavily V-doped TiO2 support with high-density Ir single atoms, enabling water oxidation at minimal Ir loading. In this design, Ti-site-substituted V provides n-type doping, and selective V leaching creates cation vacancies that anchor Ir as isolated atoms. TEM with convolutional neural network (CNN)-based analysis shows Ir single-atom density increases with V content, accompanied by lower charge-transfer resistance and higher Ir-specific activity. The density functional theory indicates that cation-site Ir introduces a midgap state below V 3d levels and shifts neighboring V 3d orbitals toward the Fermi level. Ir1/V-TiO2 achieves 1480 A gIr–1 at 1.55 V vs RHE (1.3 wt % Ir) and demonstrates device-level PEMWE operation at an Ir loading as low as 0.027 mgIr cm–2.