Photo-induced conversion of type-II CoPc/BiOBr-NSs to S-scheme heterostructure for boosting CO2 photoreduction

With efficient charge separation, S-scheme heterostructures are very attractive for photocatalytic carbon dioxide reduction, but their construction is still facing challenge. Herein, cobalt phthalocyanine (CoPc) was combined with BiOBr nanosheets (NSs) as type-II heterostructure CoPc/BiOBr-NSs. It is more interesting that light-induced oxygen vacancies on BiOBr-NSs can convert type-II CoPc/BiOBr-NSs to S-scheme structures for CO2 reduction. The optimal CoPc/BiOBr-NSs exhibited significantly enhanced CO generation with rate of 59.9 μmol g−1 h−1 (selectivity of 90.4 %), which was 25-fold higher than that of BiOBr-NSs, and much higher than most reported photocatalysts. Photo-induced oxygen vacancies on BiOBr-NSs can generate defect states on bottom of conduction band (CB), which can trap the electrons to have a recombination with holes left on HOMO band of CoPc, boosting charge separation for efficient CO2 reduction. Moreover, the central Co2+ of CoPc can accept the excited electrons from the ligand to act as active site for CO2 reduction. This work provides a new strategy of constructing metal-complex/semiconductor S-scheme photocatalyst for boosting CO2 photoreduction.