Rational Construction of a 0D/1D S-Scheme CeO2/CdWO4 Heterojunction for Photocatalytic CO2 Reduction and H2 Production

In this work, CeO2 quantum dots were anchored on the surface of oxygen defected CdWO4 nanorods through a simple precipitation procedure to construct an efficient S-scheme heterojunction. The as-fabricated pristine and hybrid photocatalysts were thoroughly characterized by XRD, BET, SEM, HRTEM, and XPS analyses and applied for the photoreduction of CO2 and photocatalytic hydrogen evolution under simulated sunlight irradiation. The results revealed that CH4 and CO were the major products and CH3OH was detected as the side product from the photoreduction of CO2. The photoreduction yield of the heterojunction was substantially improved with the addition of CeO2 as compared to the pure samples, and the heterojunction containing 40 mol % CeO2 showed the highest efficiency. This improvement could be mainly ascribed to the higher reduction potential of the separated electrons and exceptional mobility of charge carriers. Additionally, the adsorption of CO2 and hydroxyl groups was increased due to the increased density of oxygen vacancy sites at the interfacial contacts acting as trapping centers for photoexcited electrons. Based on the experimental and theoretical results, S-scheme charge transfer was proposed for the fabricated CdWO4-CeO2 heterojunction.