Layered lithium niobium (III) oxide - LiNbO₂ as a visible-light-driven photocatalyst for H₂ evolution

The search for visible-light photocatalysts is of great significance in clean energy and environmental applications to best utilise solar radiation. Some layered semiconductor photocatalysts have been found to exhibit promising performance levels. Their superior activity has been linked to the layering within the crystal structure, which may facilitate separation of carriers and, hence the reduction and oxidation reactions. Previous investigations on layered materials focused on oxides containing early transition metal cations with d⁰ electronic configurations utilising ultraviolet radiation. Attempts to synthesise layered materials with visible light response have been less successful and the photoactivity of such materials is not very high. Here, we have investigated a layered semiconducting compound, LiNbO₂ with nominal d² electronic configuration (Nb³⁺). As a result of a sub-valence band originating from filled d orbitals, LiNbO₂ exhibits visible light absorption extending to 650 nm and demonstrates interesting photocatalytic activity for hydrogen production.