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 (PbCrO 4 ) as an example, we conducted the morphology tailoring from parallelepiped (p-PbCrO 4 ) to truncated decahedron (t-PbCrO 4 ) and elongated rhombic (r-PbCrO 4 ), 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-PbCrO 4 and r-PbCrO 4 . The charge-separation efficiencies exhibit a quasilinear relation with the surface photovoltage difference between anisotropic facets. The r-PbCrO 4 gives an apparent quantum efficiency of 6.5 % at 500 nm for photocatalytic water oxidation using Fe 3+ ions as electron acceptors. Moreover, the oxidation reverse reaction from Fe 2+ to Fe 3+ ions was completely blocked with ∼100 % of Fe 3+ conversion achieved on the anisotropic PbCrO 4 crystals.