Surface oxygen vacancy and graphene quantum dots co-modified Bi2WO6 toward highly efficient photocatalytic reduction of CO2

Abstract

Weak light-harvesting capability and low electron-hole separation efficiency remain significant problems unresolved in the design of high-efficient photocatalyst. This work designed and prepared a surface oxygen vacancy (Vo) and graphene quantum dots (GQDs) co-modified Bi2WO6 (GQDs/BWO6−x). It exhibited enhanced photocatalytic conversion of CO2 to CO with a yield of 43.9 μmol·g−1·h−1, which is 1.7-fold higher than Bi2WO6 (BWO). The photogenerated electrons over GQDs/BWO6−x had a longer average fluorescence lifetime (3.3 ns) than BWO (2.7 ns), implying a high electron-hole separation efficiency. The DFT calculation results revealed that the electrons in GQDs/BWO6−x flow from the Vo-remote atoms to the Vo-neighboring atoms instead of confining in the GQDs molecules. Easy transformation of *COOH to *CO, a rate-limiting step, was suggested by an energy barrier calculation result (0.16 eV for GQDs/BWO6−x, 1.12 eV for BWO).