Spongy polyelectolyte hydrogel for efficient Solar-Driven interfacial evaporation with high salt resistance and compression resistance

The hydrogel-based evaporator for interface evaporation provides a method for sustainable freshwater production. However, salt accumulation on the surface of the steam generator affects light absorption and reduces steam generation efficiency. Achieving a high-performance, salt-resistant steam generator remains challenging. Here, sponge-like polyelectrolyte composite hydrogel-based solar steam generator (MPS) is reported. The steam generator is designed with an interpenetrating network topology and is made by in-situ polymerizing sodium polyacrylate (P(SA)) in a sponge-like polyvinyl alcohol (PVA) hydrogel framework, using molybdenum disulfide (MoS2) as a photothermal conversion material. Through the foaming process, MPS achieves self-floating and good water transportation performance, which enhances the thermal localization effect on the hydrogel surface and improves energy utilization efficiency (92.95 %), enabling efficient evaporation (3.22 kg m- 2h-1). Meanwhile, due to the coupling of P(SA), MPS exhibits excellent salt resistance, maintaining a long-term evaporation rate of 2.8 kg m- 2h-1 in high concentration saltwater (20 wt%). The porous structure and interconnected polymer chains enhance the mechanical performance of MPS, making it highly compressible and convenient for collecting freshwater marine and wilderness environments. The preparation strategy of MPS provides a feasible method to simultaneously improve the performance and durability of the interface steam generator in practical applications.