Why does F-doping enhance the photocatalytic water-splitting performance of mBiVO4? - a density functional theory study

By means of density functional theory (DFT) computations, we investigated the variations in the geometric structures and electronic properties, as well as the adsorption behavior of water on the (010) and (110) surfaces, introduced by an F dopant in a monoclinic BiVO4 system. For the bulk phase, F atoms are easier to substitute O atoms as they form a stable geometric structure. With F-doping, the band gap is narrowed and the separation efficiency of the photogenerated carriers is improved. On both (010) and (110) surfaces, F atoms prefer to substitute the two-coordinated O atoms at the outermost layer. Besides, F-doping on the surfaces can also reduce the band gap, which may enhance the visible light utilization. Due to hydrogen bonds between the F dopant and the O atom of water, the interactions between the F-doped surface and the absorbed water molecules are increased, which is favorable for water splitting under visible light.