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.