Defect-induced visible-light-driven photocatalytic and photoelectrochemical performance of ZnO–CeO2 nanoheterojunctions

The construction of heterojunctions based on metal oxide semiconductors is an emerging approach for enhancing the charge-carrier dynamics of photocatalysts. The current study focuses on building heterojunctions of Zn and Ce oxides to effectively catalyze photoinduced degradation of organic dyes, such as methylene blue (MB). To obtain a suitable ZnO–CeO2 heterojunction, photocatalysts with different Zn:Ce ratios of 3:1, 1:1, and 1:3 were synthesized using a hydrothermal method. The optimized ZnO–CeO2 heterojunction with a 1:1 ratio exhibited superior photocatalytic performance for MB degradation under solar and visible-light irradiation. This can be ascribed to the formation of oxygen vacancies with suitable trap levels induced by the readily interconvertible Ce3+/Ce4+ ions in CeO2. Owing to its low rate of charge-carrier recombination and enhanced photoinduced charge-carrier lifetime, the rate of MB degradation using the optimized photocatalyst was 6.4 times that using pristine ZnO under visible-light illumination. Moreover, photoelectrochemical analysis demonstrated that the optimized catalyst exhibited a significant visible-light response with a high charge-carrier separation efficiency. Thus, such ZnO–CeO2 heterojunctions with improved visible-light-driven photocatalytic and photoelectrochemical properties can be potentially used for wastewater treatment and other catalytic applications.