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

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 photo catalytic conversion of CO2 to CO with a yield of 43.9 mu mol & BULL;g(-1)& BULL;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 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).