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

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 junctions, formed by co-exposing anisotropic facets with matchable band structures, emerge as a promising strategy 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 junctions to switching the water splitting photoredox preference by using layered Bi₄TaO₈Cl single crystals as a model. The exposure ratio of oxidative {001} front facets to reductive {110} lateral facets of Bi₄TaO₈Cl can be continuously controlled by a flux-mediated geometric modulation method, allowing this facet junction to regulate the redox-site distribution. When increasing the {001}/{110} facets ratio, the water splitting preference switches decisively from proton-reduction dominance (H₂ yield: 50.1 µmol h⁻¹; O₂ yield: 13.6 µmol h⁻¹) to water-oxidation dominance (H₂ yield: 11.5 µmol h⁻¹; O₂ yield: 36.9 µmol h⁻¹), presenting strict facet reactivity dependence. This work provides a new perspective for photocatalyst design, emphasizing that managing the inventory of surface redox sites is as important as optimizing charge separation, while also offering a generalizable methodology to tailor catalytic preference for redox reactions.