Surface Modifications of Layered Perovskite Oxysulfide Photocatalyst Y2Ti2O5S2 to Enhance Visible-Light-Driven Water Splitting.

Abstract

Increasing the efficiency of visible-light-driven water splitting systems will require improvements in the charge separation characteristics and redox reaction kinetics associated with narrow-bandgap photocatalysts. Although the traditional approach of loading a single cocatalyst on selective facets provides reaction sites and reduces the reaction overpotential, pronounced surface charge carrier recombination still results in limited efficiency increases. The present study demonstrates a significant improvement in the hydrogen evolution activity of the layered single-crystal photocatalyst Y₂Ti₂O₅S₂. Increased performance is obtained through sequential loading of Pt cocatalysts using a two-step process followed by photodeposition of Cr₂O₃ nanolayers. The stepwise deposition of Pt involved an impregnation-reduction pretreatment with subsequent photodeposition and produced numerous hydrogen production sites while promoting electron capture. The Cr₂O₃ shells formed on Pt nanoparticles further promoted electron transfer from the Pt to the water and inhibited surface carrier recombination. Importantly, it is also possible to construct a Z-scheme overall water splitting system using the optimized Y₂Ti₂O₅S₂ in combination with surface-modified BiVO₄ in the presence of [Fe(CN)₆]^3-/4-, yielding a solar-to-hydrogen energy conversion efficiency of 0.19%. This work provides insights into precise surface modifications of narrow-bandgap photocatalysts as a means of improving the solar water splitting process.