Hollowing of nanoparticle membrane by sacrificing phase-inversion-formed nanohydrogel to enhance solar-steam generation efficiency

Photothermal materials play vital roles in solar-steam generation. However, a large number of photothermal nanoparticle (NP) materials with high performances are not suitable for solar-steam generation owing to common defects such as light reflection and leakage. Therefore, it is necessary to rationally assemble photothermal NPs into a membrane with a hierarchical structure to localize heat at the liquid surface and trap light. Herein, we report a simple and effective method of dissolving a phase-inversion-formed nanohydrogel (NH) inside an originally compacted photothermal NP membrane to enable multiple reflections and light-trapping, referred to as sacrificial NP template with phase inversion (SNTPI). The reflectance of the fabricated light-trapping membrane was 4.88 times lower than that of the compacted membrane, resulting in an average absorptance of 97.75 %. Based on this high absorptance, the membrane showed good performances in solar desalination and indoor dehumidification. Because the NH fabrication process only requires the addition of the diluted polymer solution to its nonsolvent, and the amorphous polymer NH can be readily dissolved in its solvent, we believe that the proposed SNTPI method will facilitate the sustainable development of solar-steam devices.