Synergistic Energy Nanoconfinement and Water Activation in Hydrogels for Efficient Solar Water Desalination.

Precisely controlled distribution of energy in solar-to-thermal energy conversion systems could allow for enhanced energy utilization. Light-absorbing hydrogels provide a means for evaporating water by using solar energy, yet targeted delivery of solar thermal energy to power the water evaporation process remains challenging. Here, we report a light-absorbing sponge-like hydrogel (LASH) that is created by in situ gelation of a light-absorbing nanoparticle-modified polymer, leading to synergistic energy nanoconfinement and water activation. By experimental demonstration and theoretical simulation, the LASH presents record high vapor generation rates up to ∼3.6 kg m-2 h-1 and stable long-term performance under 1 sun (1 kW m-2) irradiation. We investigate the energy confinement at the polymer-nanoparticle interphases and the water activation enabled by polymer-water interaction to reveal the significance of such effects for high-rate solar vapor generation. The water vaporization enabled by LASHs can remove over 99.9% of salt ions in seawater through solar water desalination. The fundamental design principle, scalable fabrication route, and superior performance offer possibilities for portable solar water purification, industrial solar-powered water treatment, and other advanced solar thermal applications.