Oxysulfide photocatalyst breaking the 60 % quantum efficiency barrier for visible-light-driven hydrogen production from water

To achieve a high efficiency in solar powered photocatalytic water splitting, the inorganic semiconducting photocatalysts are supposed to have i) a narrow bandgap for harvesting solar light sufficiently, ii) an intrinsic built-in electric field to enable efficient electron-hole separation, and iii) precise surface modifications to accelerate redox reactions. Y 2 Ti 2 O 5 S 2 (YTOS), a cost-effective oxysulfide photocatalyst, is believed to be a promising candidate by meeting all these requirements. However, the existing studies on YTOS overlook the synergistic interaction between facets exposure, built-in electric fields, and interfacial reaction kinetics, hindering the rational design of highly efficient photocatalysts. Herein, we present a flux-mediated morphology control to synchronize oxidation reactions on hole-rich {001} facets and reduction reactions on electron-rich {101} facets within individual YTOS particles. In-situ cocatalysts modification of the facets further enhances the built-in electric field intensity while promoting surface redox kinetics. These comprehensive operations significantly improve both the activity and stability of YTOS, achieving a record apparent quantum yield of 60 % among oxysulfide photocatalysts. Such a value grants the YTOS particle a qualified photocatalyst to approach the targeted solar-to-hydrogen conversion efficiency of 10 % that is required for practical implementation of solar-powered water splitting. This work not only demonstrates the great potential of oxysulfide photocatalysts for water splitting but also provides a top-level design strategy by engineering charge migration and transition kinetics.