Lower oxygen vacancy concentration in BiPO₄ with unexpected higher photocatalytic activity

Defect engineering has been demonstrated to be an appealing strategy to boost the photocatalytic activity of materials. However, can higher defect concentration bring about higher photocatalytic activity? This is an open question. In this work, BiPO₄ photocatalysts with controllable oxygen vacancy concentrations were successfully synthesized. The photocatalytic activity of the obtained BiPO₄ photocatalysts was determined by the removal of ciprofloxacin and 4-chlorophenol, as well as CO₂ photoreduction. The BiPO₄ materials with lower oxygen vacancy concentration could display unexpected higher photocatalytic efficiency. Through the investigation of different factors which may affect the photocatalytic performance, such as crystal structure, morphology, specific surface area, defect, and energy band structure, it can be found that the energy band structure difference was responsible for the enhanced photocatalytic activity.