Enhanced Photocatalytic CO₂ Reduction in Defect-Engineered Z-Scheme WO_3–<i>x</i>/g-C₃N₄ Heterostructures

Abstract

Oxygen vacancy-modified WO_3-<i>x</i> nanorods composited with g-C₃N₄ have been synthesized via the chemisorption method. The crystalline structure, morphology, composition, band structure, and charge separation mechanism for WO_3-<i>x</i> /g-C₃N₄ heterostructures are studied in detail. The g-C₃N₄ nanosheets are attached on the surface of WO_3-<i>x</i> 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 WO_3-<i>x</i> /g-C₃N₄ heterostructures exhibit much higher photocatalytic activity than the pristine g-C₃N₄.