A skin-effect-inspired 3D solar evaporator for simultaneously achieving highly efficient steam generation and ultra-high salt resistance

Solar-driven interfacial evaporation is regarded as a very promising strategy to alleviate the pressing freshwater scarcity. However, owing to the trade-off between thermal localization and ion transport, simultaneously achieving remarkable evaporation performance and ultra-high salt resistance is challenging. In this work, inspired by the skin effect of currents in wires, we constructed a skin-effect-inspired three-dimensional solar evaporator (SEISE) by controlling the porosity of the evaporator structure based on the principle of division of responsibilities and collaborative matching. Specifically, the SEISE with non-uniform porosity can realize the localization of water transport through its surface layer with low porosity, precisely matched with the thermal localization resulting from the internal body with high porosity and extremely low thermal conductivity, thereby greatly enhancing the interfacial evaporation performance. The maximum evaporation rate of the SEISE can remarkably reach 6.0 kg m−2 h−1 under 1 sun. Furthermore, the diffusion and convection of ions in the SEISE were significantly enhanced because of the rapid water transport within its surface layer. No salt crystals were observed on the evaporation surface after continuous operation in ultra-high salinity brine (25 wt%) for 48 h. This work demonstrates a highly efficient and feasible strategy for developing next-generation solar evaporators.