CuS Nanosheet-Coated PVA Sponge for Desalination and Wastewater Purification

Interfacial solar steam generation (ISSG) utilizing polymeric hybrid evaporators has emerged as a promising strategy for sustainable freshwater production from seawater and wastewater, addressing one of the most pressing global challenges: the freshwater crisis. Despite significant progress, practical deployment is hindered by the lack of compact, low-cost, and portable ISSG systems that combine high evaporation efficiency with salt-resistance and antimicrobial performance. In this study, a straightforward solar light-induced deposition technique was employed to uniformly coat CuS nanosheets onto a commercial poly(vinyl alcohol) (PVA) sponge, creating a three-dimensional (3D) CuS nanosheet-coated PVA sponge (CuS@PVA) solar evaporator. By optimizing the viscosity of the coating suspension, a homogeneous distribution of the photoactive layer was achieved throughout the sponge architecture without clogging its microporous structure. The resulting 3D CuS@PVA solar evaporator exhibited a significantly reduced water evaporation enthalpy (1833.07 kJ kg – 1 ) compared to pure water (2422.16 kJ kg – 1 at 33.5 °C), attributed to synergistic hydrogen bonding interactions among water molecules, PVA hydroxyl groups, and the CuS nanosheet interfaces. This structural design led to an impressive evaporation rate of 3.18 kg m – 2 h – 1 and a solar-to-vapor conversion efficiency of 162% under 1 sun irradiation. Long-term outdoor testing confirmed robust antisalt fouling behavior, with no visible salt accumulation after sustained exposure to seawater (2.34 kg m – 2 evaporated in 1 h). A spontaneous ion-gradient-driven exchange mechanism within the porous matrix supports continuous desalination without clogging. Furthermore, the system demonstrated superior sewage purification capabilities alongside antibacterial properties, paving the way for practical real-world implementation. Altogether, the low-cost, recyclable, and multifunctional CuS@PVA evaporator presents a highly scalable pathway toward decentralized, sustainable freshwater production in remote or resource-limited settings.