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.