Dramatically promoted photocatalytic water splitting over InVO₄ via extending hole diffusion length by surface polarization

Indium vanadate (InVO₄) is considered to be a promising photocatalyst due to its strong absorption in the visible light region and potential to overall split water. However, it is hardly used for water splitting on account of its short diffusion length of holes. In this work, surface polarization based on inorganic acid modification was adopted to deal with above issue. The results show that the modified acid with hydroxyl groups would ionize in water, making InVO₄ carry more negative charges. Such a surface polarization remarkably enhanced the activities, of which up to 21.74 μmol·g⁻¹·h⁻¹ for hydrogen generation and 13.18 μmol·g⁻¹·h⁻¹ for oxygen generation, respectively. The enhanced activities are mainly attributed to the induction of surface-carried negative electrostatic field, by which the holes were driven to the surface and its diffusion length was extended from ∼ 10 nm to ∼ 50 nm, while the electron tend to be transport to the inner. Thus, the charge carrier recombination was inhibited and more holes could arrive at the surface to generate oxygen, which is the rate-determining step of water splitting.