High-Performance Solar Desalination of Seawater Using a Hydrophilic WS2/Poly(vinyl alcohol) Sponge Evaporator

Abstract Interfacial solar steam generation (ISSG) has emerged as an attractive technology for sustainable seawater desalination. However, overcoming salt accumulation, enhancing water transport, and ensuring long-term operational stability remain key challenges for its practical deployment. In this study, we report a simple, scalable, and cost-effective fabrication strategy in which hydrothermally synthesized WS2 microsheets are uniformly integrated onto a commercially available poly(vinyl alcohol) (PVA) sponge to construct a three-dimensional porous photothermal evaporator. The unique WS2/PVA architecture synergistically combines the excellent photothermal properties of WS2 with the intrinsic hydrophilicity and interconnected water-transport channels of the PVA sponge, resulting in efficient thermal localization and continuous water supply. The optimized 3 wt % WS2/PVA evaporator exhibited excellent broadband solar absorption (85.48%) across the UV–visible–NIR region and achieved a high photothermal conversion efficiency of 96.82%. Under solar light illumination, the optimized WS2/PVA evaporator delivered an evaporation rate of 2.78 kg m–2 h–1, representing the highest reported performance among WS2-based ISSG materials. This value surpasses those of previously reported CS/WS2 (2.10 kg m–2 h–1) and WS2–O-graphene (2.11 kg m–2 h–1) systems and is substantially higher than that of pristine PVA (0.37 kg m–2 h–1). The enhanced performance is attributed to the reduced evaporation enthalpy (1398 kJ kg–1), excellent hydrophilicity (water contact angle 19.1°), and strong interfacial hydrogen-bonding interactions between WS2 and PVA, which collectively facilitate rapid water transport and efficient heat confinement. Furthermore, the evaporator demonstrated excellent operational stability over 10 consecutive cycles without observable salt accumulation during 8 h of continuous operation. Desalination experiments using real seawater collected from Dwarka achieved an evaporation rate of 2.58 kg m–2 h–1, with the conductivity decreasing from 37.9 mS cm–1 to 823 μS cm–1 confirming effective salt rejection. These findings demonstrate that the 3D WS2/PVA photothermal evaporator provides a low-cost, scalable, and environmentally sustainable platform for high-efficiency solar desalination and freshwater production.