Switching water splitting photoredox preference by geometric modulation of charge consumption sites in Bi4TaO8Cl single crystal

Abstract

Solar-driven catalysis represents a significant route for solar fuel synthesis, but its efficiency is severely restricted by rapid charge recombination and sluggish reaction kinetics. Facet junction by co-exposing anisotropic facets with matchable band structures emerges promisingly for achieving spatial separation of photogenerated charges on the surface of single-crystalline catalysts, while the facet-dependent reactivity among redox reactions remains unexplored. Herein, we extend the function of facet junction to switching the water splitting photoredox preference by using layered Bi 4 TaO 8 Cl single crystal as a model. The exposure ratio of oxidative {001} front facets to reductive {110} lateral facets of Bi4TaO8Cl can be continuously controlled by a fluxmediated geometric modulation method, allowing this facet junction regulatable charge separation and redox sites distribution. With increasing the {001}/{110} facets ratio, the water splitting preference switches decisively from proton-reduction dominance (H2 yield: 50.1 μmol/h; O2 yield: 13.6 μmol/h) to water-oxidation dominance (H2 yield: 11.5 μmol/h; O2 yield: 36.9 μmol/h), presenting strict facet reactivity dependence rather than charge separation efficiency. This work transforms the crystalline photocatalyst design paradigm from pursuing optimal charge separation to managing active sites, offering a generalizable methodology to tailor catalytic selectivity for redox reactions.