Phase Inversion-Based foam hydrogels for highly efficient Solar-Powered interfacial desalination

Innovative materials are required to promote the development of solar-powered interfacial desalination and purification technologies to address global freshwater scarcities. To this end, evaporators using polymeric hydrogels have been widely studied. However, these systems are slow, energy-intensive, complex, and difficult to operate. New strategies are in urgent need. The present work employs polymeric phase inversion to develop poly (vinyl alcohol) (PVA)-based foam hydrogels, wherein the air bubble phase served as the matrix and cross-linked PVA hydrogel acted as the dispersed phase. In addition, we utilize Ti3C2Tx nanosheets-based MXene as the photothermal agent to facilitate the fabrication of hierarchical pore-in-pore structures. The prepared PVA/MXene foam hydrogels exhibit > 95% porosity, as well as high compressibility (>7000 cycles) and very rapid water transport. Importantly, these materials also exhibit remarkably low water evaporation enthalpies. Combined with a new heat supply model, those foam hydrogels achieve an evaporation rate of 4.1 ± 0.1 kg m−2h−1 with energy efficiency up to 128.8% ± 2.0% under 1 sun irradiation, which is the highest value for MXene-based nanocomposites reported so far. This study demonstrates a significant advancement in solar desalination system by combining phase inversion to make innovative foam materials with optimal external heat management.