Tuning the Anisotropic Facet of Lead Chromate Photocatalysts to Promote Spatial Charge Separation

A crucial issue in artificial photosynthesis is how to modulate the behaviors of photogenerated charges of semiconductor photocatalysts. Here, using lead chromate (PbCrO4) as an example, we conducted the morphology tailoring from parallelepiped (p‐PbCrO4) to truncated decahedron (t‐PbCrO4) and elongated rhombic (r‐PbCrO4), resulting in exposed anisotropic facets. The spatial separation of photogenerated charges closely correlates to the anisotropic facets of crystals, which can only be realized for t‐PbCrO4 and r‐PbCrO4. The charge‐separation efficiencies exhibit a quasilinear relation with the surface photovoltage difference between anisotropic facets. The r‐PbCrO4 gives an apparent quantum efficiency of 6.5 % at 500 nm for photocatalytic water oxidation using Fe3+ ions as electron acceptors. Moreover, the oxidation reverse reaction from Fe2+ to Fe3+ ions was completely blocked with ∼100 % of Fe3+ conversion achieved on the anisotropic PbCrO4 crystals. Spatial separation of photogenerated electrons and holes correlates closely with the anisotropic facets of PbCrO4 crystals. Charge‐separation efficiencies exhibit a quasilinear relationship with the surface photovoltage difference between anisotropic facets. An apparent quantum efficiency (AQE) of 6.5 % at 500 nm for photocatalytic water oxidation was achieved after optimizing the anisotropic facets of the PbCrO4 crystals.