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

Oxygen vacancy-modified WO3-x nanorods composited with g-C3N4 have been synthesized via the chemisorption method. The crystalline structure, morphology, composition, band structure, and charge separation mechanism for WO3-x /g-C3N4 heterostructures are studied in detail. The g-C3N4 nanosheets are attached on the surface of WO3-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-C3N4 and the holes in the valence band of WO3 can participate in the photocatalytic reaction to reduce CO2 into CO. New energy levels of oxygen vacancies are formed in the band gap of WO3, further extending the visible-light response, separating the charge carriers in Z-scheme and prolonging the lifetime of electrons. Therefore, the WO3-x /g-C3N4 heterostructures exhibit much higher photocatalytic activity than the pristine g-C3N4.