Enriching Oxidation Sites-Based Facets in Lead Chromate to Boost Photoelectrochemical Sensing Response

A key issue in photoelectrochemical applications is the modification of the behavior of photogenerated charge barriers. An effective strategy to improve the photoelectrochemical performance of semiconductor materials is to use the facet effect to promote spatial charge separation. In this work, three different morphologies of lead chromate (PbCrO₄) crystals are prepared by a simple hydrothermal method that used ammonium fluoride as the structure-directing agents. Spatial separation of photogenerated electrons and holes is clearly demonstrated in the (012), (020), and (200) facets of PbCrO₄ crystals. In situ photo-deposition experiments reveal that the oxidation and reduction sites are distributed on the anisotropic (012) and (020)/(200) facets of all the PbCrO₄ crystals. PbCrO₄ synthesized with a high Pb²⁺/F^- ratio with maximum exposure of (012) facet has remarkably better performance in photoelectrochemical detection of ascorbic acid compared with PbCrO₄ synthesized either without ammonium fluoride or with a low Pb²⁺/F^- ratio. The photoelectrochemical detection performance correlates well with the surface photovoltage difference between the anisotropic facets. The study provides fundamental understanding of the facet-dependent activity of PbCrO₄ crystals, which will be beneficial for advancing understanding of spatial charge separation in semiconductor-based photoelectrochemical applications.