Boosting photocatalytic water oxidation on lead chromate through crystal facet engineering

Although crystal facet engineering of semiconductor crystals has been demonstrated to be effective in particulate photocatalysts for solar energy conversion, it is imperative to rationally regulate the exposed crystal facets and their configurations to improve charge separation efficiency. In this study, focusing on visible-light-driven water oxidation photocatalyst lead chromate (PbCrO4), we find that a flux-assisted treatment enables the precise tuning of the hole-accumulating facets of anisotropic PbCrO4 crystal, transitioning the top surface from {−101} to {001} facets while preserving its spatial charge separation characteristics. Owing to the superior hole-accumulating property and water oxidation kinetics of the {001} facets, the resulting Flux-PbCrO4 crystals achieve a charge separation efficiency exceeding 75%, leading to a remarkable improvement in photocatalytic water oxidation activity. Further incorporation of cocatalysts onto the Flux-PbCrO4 crystals results in an apparent quantum efficiency of 18.5% at 500 nm for photocatalytic water oxidation. [Display omitted] •Regulating facet configurations improves charge separation efficiency in PbCrO4•Flux-assisted treatment tunes the top facets of PbCrO4 from {−101} to {001}•Flux-PbCrO4 with cocatalysts achieves an AQE of 18.5% at 500 nm for water oxidation Photocatalytic water oxidation on semiconductor photocatalysts is primarily hindered by the inefficient separation of photogenerated charges and the sluggish kinetics of the water oxidation reaction. Although spatial charge separation among various facets of semiconductor crystals has been proven to promote charge separation and regulate surface catalytic reactions, challenges remain in effectively regulating hole-accumulating facets to both amplify the difference between hole-accumulating and electron-accumulating facets and accelerate water oxidation kinetics. Herein, we demonstrated that a flux-assisted treatment allows for the rational regulation of hole-accumulating facets on PbCrO4 crystals transitioning from {−101} to {001} facets while maintaining their spatial charge separation properties. Such crystal facet engineering not only enhances the driving force for charge separation among the anisotropic facets but also reduces the overpotential for water oxidation. Spatial charge separation between different facets of semiconductor photocatalysts has emerged as a general strategy in photocatalysis. Focusing on visible-light-driven water oxidat