A Skin-Effect and Ion-Pumping Inspired 3D Solar Evaporator With High Salt Resistance for Sustainable Desalination

Solar-driven interfacial evaporation holds promise for addressing freshwater scarcity, yet its long-term performance is compromised by salt fouling. Herein, we present a 3D dispersed interfacial evaporator that synergistically integrates the "skin effect" and "ion-pumping effect" to enhance vapor generation and salt resistance. The evaporator was prepared by deposition of a chemically crosslinked polyvinyl alcohol/clay composite hydrogel onto polyester aroma sticks to improve hydrophilicity and stabilize capillary channels, and then deposition of Cu-MOF nanocrystals to provide broad-spectrum light absorption (>90%). Under 1 kW m^-2 illumination, the evaporator achieved average evaporation rates of 4.68 and 4.36 kg m^-2 h^-1 during 10 h of continuous operation in 3.5 wt.% and 20 wt.% NaCl solutions, respectively. Further structural optimization using ambient wind flow boosts the evaporation rate to 15.82 kg m^-2 h^-1 at a wind speed of 1 m s^-1. Mechanistic investigations reveal the skin effect mitigates structural degradation by restricting salt crystallization to surface layers, while the ion-pumping effect promotes ion diffusion to prevent salt accumulation. Outdoor tests verify that ion concentrations in the harvested freshwater comply with the WHO drinking water standards. This study demonstrates a viable strategy for robust, high-efficiency, salt-tolerant solar desalination under diverse environmental conditions.