In Situ Assembled ZnWO4/g-C3N4 S-Scheme Heterojunction with Nitrogen Defect for CO2 Photoreduction

Abstract

Reforming CO₂ into storable solar fuels via semiconductor photocatalysis is considered an effective strategy to solve the greenhouse effect and resource shortage. Unfortunately, the problem of rapid photogenerated carriers severely limits the CO₂ reduction capability of one-component catalysts. The fabrication of S-scheme heterojunctions with defects can result in efficient spatial separation of photo-generated charge carriers and increase adsorption and activation of nonpolar molecules. Herein, ZnWO₄/g-C₃N₄ S-scheme heterojunctions with defects are constructed through in situ growth method. The experiments show that the generation rate of CO from CO₂ reduction is up to 232.4 μmol∙g⁻¹∙h⁻¹ with a selectivity close to 100%, which is 11.6 and 8.5 times higher than those of pristine ZnWO₄ and g-C₃N₄, respectively. In situ XPS and work function analyses demonstrate the S-scheme charge transport pathway, which facilitates the spatial segregation of photogenerated carriers and promotes CO₂ reduction. In situ ESR illustrates that CO₂ molecules are adsorbed by nitrogen vacancies, which act as photoelectron acceptors during the photocatalytic reaction and are favorable for charge trapping and separation. The S-scheme charge transport mode and nitrogen vacancy work together to stimulate the efficient conversion of CO₂ to CO. This work presents significant insights to the cooperative influence of the S-scheme charge transport mode and defects in regulating CO₂ reduction activity.

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