Substitution and oxygen vacancy double defects on Bi2MoO6 induced efficient conversion of CO2 and highly selective production of CH4

A series of novel iodine substitution and oxygen vacancy double defects Bi2MoO6 nanosheets for enhanced photocatalytic reduction of CO2 is reported, which exhibited superior CO2 photocatalytic activity and CH4 selectivity under full solar spectrum illumination. Bi2MoO6-I2 (the molar ratio of I to Mo is 0.13) has the highest photocatalytic activity, its CO yield is 2.0 times that of pure Bi2MoO6, the CH4 yield is 12.2 times that of pure Bi2MoO6, and the CH4 selectivity reaches 5.3 times that of pure Bi2MoO6. Its structure and physicochemical properties were investigated by material characterizations, photoelectrochemical tests and DFT calculations. The enhancement in CO2 conversion and CH4 selectivity benefit from: (1) Larger specific surface areas and smaller nanosheets thicknesses facilitate carrier migration; (2) More suitable band structure promotes the reduction of CO2; (3) Insertion of impurity energy levels in the band gap enables efficient jumping of photogenerated electrons; (4) Double defects contribute to efficient CO2 adsorption and activation; (5) Promoting highly selective conversion of CO2 to CH4 by optimising the formation energy of reaction intermediates.