Photothermal Catalytic Gel Featuring Spectral and Thermal Management for Parallel Freshwater and Hydrogen Production

Abstract Desalination processes often require large amounts of energy to create clean water, and vice versa for the generation of energy. This interdependence creates a tension between the two essential resources. Current research focuses on one or the other, which exacerbates water‐energy stress, while few tackle both issues jointly. Herein, a low‐carbon technology, H 2 O–H 2 co‐generation system that enables concurrent steady freshwater and clean energy output is reported. The water‐energy coupled technology features a spectrally and thermally managed solar harvesting gel for photoredox and photoheating effects. This photothermal catalytic gel exploits interfacial solar heating for heat confinement, and localized plasmonic heating at the catalyst active sites to remarkably improve water and hydrogen production, thus maximizing energy value per area. To this end, a stand‐alone renewable solar desalination system is successfully demonstrated for parallel production of freshwater and hydrogen under natural sunlight. By doing so, the water–energy nexus is transformed into a synergistic bond that offers opportunities to better meet expected demand rather than acting in competition.