CO2 Photoreduction Catalyzed by Cu-Deficient Cu1.95S@CuS: Enhanced Performance via Boosted Directional Interfacial Charge Transfer

Heterojunction construction and defect engineering are regarded as a strategy for improving photogenerated charge carrier transfer and enhancing photocatalytic performances. In this work, we combined defect engineering with heterojunctions to improve the CO2 photoreduction activity of Cu1.95S@CuS. Benefiting from the unique structure, the internal electric field of the Z-scheme Cu1.95S@CuS heterostructure was built, reducing the photogenerated charge carrier recombination and boosting the directional carrier transfer from CuS to the surface Cu vacancies on Cu1.95S, thus strengthening the activation of CO2 and photoreduction activity of CO2 to CO with a 100% product selectivity. The CO2 photoreduction pathway was fully explored and analyzed by in situ Fourier transform infrared spectroscopy. In addition, it could be concluded from density functional theory calculation results that the surface Cu vacancies and heterojunction interfaces could lower the energy barrier of the rate-determining step, enabling a spontaneous reduction reaction. This work provides a strategy of designing heterojunction and deficient photocatalysts for solar energy conversion.