Single-stage reverse-structured solar evaporator from two to three dimensional by transparent hydrogel

Reverse-structured solar evaporators are lauded for high water collection efficiency but the clean water yield is constrained by the two-dimensional evaporation in single-stage design. To address this limitation, the evaporation process was expanded into three-dimensional space by incorporating transparent hydrogels as a layer for solar energy transmission and evaporation enhancement. Thermal management in these evaporators was meticulously designed to localize heat at the evaporation region, thereby minimizing convective and radiative energy losses. Through this approach, a water collection rate of 1.73 kg·m −2 ·h −1 and a collection efficiency of 76.8 % were attained under one sun illumination, which are among the highest values reported for single-stage solar evaporators. Outdoor testing confirmed the design's efficacy, achieving a water collection rate exceeding 1.2 kg·m −2 ·h −1 during a long time period, thus validating its practical application in real-world environments.