Structural and Electrical Factors of the Photocatalytic Activity of Bi₂WO₆ and Bi₂MoO₆ in Water-Splitting Applications

Artificial photosynthesis is a sustainable technological option to store solar energy through the photocatalytic conversion of carbon dioxide and water into chemical fuels. The main challenges with this photocatalytic process include tuning the band gap of the material to match the solar spectrum and ensuring its stability in aqueous environments. An appealing approach for developing such photocatalysts consists of intercalating functional layers into metal oxides, as is the case for perovskite-derived compounds of the Aurivillius (Bi₂A_n-1B_nO_3n+3) family, which have been shown to be photoactive under visible light. Using density-functional theory, we predict the nanosheet morphology of Bi₂WO₆ and Bi₂MoO₆ under applied voltage, and we provide a molecular description of the charged interface under controlled pH and applied voltage. This study offers a molecular interpretation of the competing structural and electrical factors that underlie the facet-dependent photocatalytic activity of layered Bi₂A_n-1B_nO_3n+3 compounds.