LiXO₂(X = Co, Rh, Ir) and solar light photocatalytic water splitting for hydrogen generation

Alkali metal transition oxide LiCoO₂ has been successfully commercialized as a lithium-ion battery material, and some attention is paid to its homologous derivatives LiRhO₂ and LiIrO₂. However, the photocatalytic properties have not been explored yet for these compounds. Using the first-principles calculations, we carry out investigations on the electronic properties, light absorption, and mobility to understand the feasibility of LiXO₂(X = Co, Rh, Ir) for solar light photocatalytic hydrogen generation from water-splitting. The results show that the band edges of LiCoO₂ and LiRhO₂ meet the redox potential requirements of the water-splitting hydrogen evolution reaction. In addition, the enhanced absorptions of LiXO₂(X = Co, Rh, Ir) in the visible light range imply that they could well respond to solar light, while the significant difference in the mobilities of electrons or holes can strengthen spatial charge separation of the photoexcited electron-hole pairs. The solar-energy-to-hydrogen conversion efficiencies of LiCoO₂ and LiRhO₂ can reach 11.2% and 15.5%, respectively. The results support LiCoO₂ and LiRhO₂ as promising candidates for visible-light photocatalytic hydrogen production from water-splitting.