Hierarchical CuO/ZnO Heterojunction with Improved Spectrum Absorption for Interfacial Solar Steam Generation

Interfacial solar steam generation (ISSG) has established itself as an achievable choice for sustainable freshwater production. However, the low evaporation rate hinders its practical application. Developing photothermal materials is one of the most efficient strategies to enhance ISSG performance. Herein, a p-n CuO/ZnO (CZO) heterojunction was created to further improve its nonradiative relaxation and used for the ISSG. The CZO on carbon paper (CP), named as CZO-CP, was prepared by a coelectrodeposition method. The CZO-CP samples were investigated by X-ray diffraction (XRD), photoluminescence (PL), and differential charge density. The results showed that a heterogeneous electric field was formed between CuO and ZnO, leading to enhanced carrier separation and migration. The combination effect of CZO and CP led to an improved light absorption range from visible to infrared wavelengths, resulting in an increased overall light absorption. The CZO-CP exhibited excellent photothermal conversion properties, making it suitable for ISSG use. A specially designed triple-layer structure consisting of a CZO-CP photothermal layer, a medical gauze water delivery layer, and a polystyrene foam thermal insulation layer was utilized in a homemade ISSG system. The rational management of heat and water in this triple-layer structure demonstrated efficient ISSG with an evaporation rate of 2.03 kg·m^-2·h^-1 and a photothermal conversion efficiency of 93.94%. Moreover, the CZO-CP ISSG showed sustainable evaporation in wastewater and seawater purification and desalination, highlighting its potential practical applications. Therefore, this work presents a novel and promising approach for efficient solar energy conversion and ISSG applications that could contribute to mitigating the environmental and energy challenges faced by society.