Thermoelectric-Field-Enabled Salt-Resistant Interfacial Evaporation for Sustainable Water Purification

Solar-driven interfacial evaporation offers a promising route for decentralized water purification, yet its practical deployment is fundamentally limited by salt accumulation under high salinity and prolonged operation. Here, we report a thermoelectric-responsive evaporator that integrates photothermal localization, vertical temperature-gradient engineering, and redox-mediated thermoelectric conversion within a single, energy-autonomous architecture. By coupling a superhydrophobic photothermal top layer with a Fe(CN)64-/3- doped hydrogel bottom, a stable temperature gradient under solar irradiation generates a thermally induced interfacial electric field without external bias. This electric field simultaneously elevates the nucleation energy barrier for salt crystallization and dynamically repels salt nuclei from the evaporation surface via negative dielectrophoretic forces, even under highly saline conditions. As a result, the evaporator maintains a high evaporation rate of 2.5 kg m-2 h-1 with only a 6.9% performance loss at 10 wt % NaCl, far exceeding conventional photothermal systems. Long-term outdoor tests demonstrate stable operation over 20 days without salt fouling or material degradation, while techno-economic analysis yields a levelized cost of water of ∼1-3 US$ m-3, competitive with small-scale solar desalination technologies. This work establishes thermoelectric field engineering as a general and scalable strategy to overcome salt accumulation, bridging the gap between laboratory-scale photothermal evaporation and real-world environmental water treatment.