Crystal facet engineering of polar single crystal BiOCl with improved piezo-photocatalytic activity

It is an effective strategy to enhance the piezoelectric-photocatalytic activity of catalysts by purposefully exposing highly active crystal planes, but the controllable synthesis remains a challenge. In addition, it is also elusive how the crystal planes regulate the activity. In this work, BiOCl with selectively exposed (0 0 1) or (1 0 1) crystal planes was synthesized by a pot of hydrothermal method. The degradation properties of organic dyes with different exposed crystal planes under photocatalysis, piezoelectric catalysis and piezoelectric photocatalysis were investigated. In addition, it is also found that in the process of piezoelectric photocatalysis, the enrichment of reducing active centers also promotes the occurrence of catalytic reactions, and plays a greater role than small-plane charge separation. The BiOCl with a with high exposure (0 0 1) plane not only has a narrow bandgap, high charge separation efficiency, and a significant piezoelectric coefficient, but also is more prone to experience band bending under ultrasonic action, thus significantly enhancing the activity. The findings of this research will deepen our comprehension of the piezoelectric-photocoupler catalytic reactions of crystal plane regulation affecting planar charge separation and active sites.