Enhanced Photocatalytic CO2 Reduction in Defect-Engineered Z-Scheme WO3–x/g-C3N4 Heterostructures

Oxygen vacancy-modified WO 3- x nanorods composited with g-C 3 N 4 have been synthesized via the chemisorption method. The crystalline structure, morphology, composition, band structure, and charge separation mechanism for WO 3- x /g-C 3 N 4 heterostructures are studied in detail. The g-C 3 N 4 nanosheets are attached on the surface of WO 3- x nanorods. The Z-scheme separation is confirmed by the analysis of generated hydroxyl radicals. The electrons in the lowest unoccupied molecular orbital of g-C 3 N 4 and the holes in the valence band of WO 3 can participate in the photocatalytic reaction to reduce CO 2 into CO. New energy levels of oxygen vacancies are formed in the band gap of WO 3 , further extending the visible-light response, separating the charge carriers in Z-scheme and prolonging the lifetime of electrons. Therefore, the WO 3- x /g-C 3 N 4 heterostructures exhibit much higher photocatalytic activity than the pristine g-C 3 N 4 .