Water oxidation catalysed by quantum-sized BiVO4

Abstract

Bismuth vanadate BiVO₄ is one of the most promising materials for photoelectrochemical water splitting, with recent work highlighting the improved photocatalytic activity of quantum sized BiVO₄ compared with the crystalline phase. Herein, we report a theoretical investigation of the structural, optical and catalytic properties of the (BiVO₄)₄ clusters through a combination of density functional theory methods (ab initio molecular dynamics, time-dependent density functional theory, transition state theory). The enhanced solar water oxidation efficiency of BiVO₄ quantum-sized clusters is linked with the localisation of the spin density on the cluster surface, and the dramatic reduction, compared with the crystalline BiVO₄ phase, of the Gibbs energy of activation and Gibbs energy of reaction associated with the hydrogen transfer process between water and BiVO₄. Our results illustrate the main effects associated with the reduction of dimensions (from bulk to quantum-size) on the main steps of water oxidation mechanisms. This understanding can contribute to the design of efficient BiVO₄ quantum sized water-splitting photocatalysts.