A simple strategy toward cost-effective and scalable hydrogel/melamine foam evaporator for sustainable and stable fresh water generation

Interfacial solar vaporization has emerged as a promising technology for freshwater generation, attracting significant attention in recent years. Hydrogels, with their inherent hydrophilicity and low enthalpy of evaporation, are considered ideal materials for interfacial solar-driven evaporation. However, their practical deployment remains hindered by complex fabrication processes and high costs. Herein, we report the development of facile, low-cost hydrogel/melamine foam composite evaporators (HMFs) that enable highly efficient and stable interfacial solar vaporization. The HMFs were fabricated by spray-coating the carbon black-infused hydrogel onto the upper surface of the MF. Under 1.0 sun, HMFs achieved an evaporation rate of 2.51 kg·m⁻ 2 ·h⁻ 1 with an evaporation efficiency of 89.5 %. Notably, the HMF exhibited robust stability and durability under harsh environmental conditions, maintaining its structural integrity and steady evaporation performance even after 30 days of continuous outdoor operation. Furthermore, the spent HMFs can be recycled, and the SA-CB hydrogel would not cause pollution even if left in the environment. These findings establish HMFs as a highly competitive candidate for scalable and sustainable solar-driven freshwater production.