Modulating internal electric field by oxygen vacancy engineering and consequent forming quantum wells for boosted selective CO2 photoreduction

Although internal electric field of photocatalysts is considered as the potent driving force for efficient charge separation, modulating the internal electric field intensity remains a challenge. Herein, we considered that the internal electric field intensity of Sillén-structured bimetallic oxyhalide PbBiO2Cl could be modulated by tuning surface oxygen vacancy concentration, thereby influencing the corresponding charge transfer. In comparison to bulk PbBiO2Cl and PbBiO2Cl with deficient oxygen vacancies, the PbBiO2Cl with rich oxygen vacancies possessed enhanced internal electric field intensity due to its high oxygen vacancy concentrations, resulting in the primary charge separation spatially. Then the surface oxygen vacancies captured more dissociative electrons as quantum wells to promote the photocatalytic selective CO2-CO conversion. The mechanism was researched and verified by in-situ FTIR and DFT calculations. Using defect engineering to simultaneously modulate internal electric field and form quantum wells for promoting charge separation is an efficient strategy to rationally improve photocatalytic performances.