Band engineering of AgSb1−xBixO3 for photocatalytic water oxidation under visible light

Abstract

Ag-based oxides, particularly AgSbO₃, have attracted attention in photocatalytic O₂ evolution from water splitting. Employing state-of-the-art DFT calculations and a statistical mechanical approach, we investigated the incorporation of Bi into AgSbO₃ to form a AgSb_1−xBi_xO₃ solid-solution for tuning the band gap to the optimum (around 2.0 eV) for the photocatalysis of water splitting under sunlight. A phase transition from the pyrochlore to ilmenite phase was predicted at x ≈ 0.21. The band gap decreases almost linearly with increasing Bi concentration for each phase. The decreased band gap is attributed to the lower energy of the Bi s–O p antibonding orbitals than that of the Sb s–O p antibonding orbitals in the conduction bands. Excitingly, a band gap of around 2.0 eV was obtained at x = 0.1875. The combination of a strong oxidizing potential and an optimal band gap for solar light absorption makes the pyrochlore AgSb_0.8125Bi_0.1875O₃ solid-solution a promising candidate for the production of oxygen in a Z-scheme water-splitting system.