Photothermal performance of polymer hydrogels via solar vapor generation for clean water production: a comprehensive review

Abstract

Solar vapor generation (SVG) is an innovative and sustainable technology that plays a vital role in tackling the pressing issue of global water scarcity. By harnessing solar energy, SVG offers an effective solution to improve water access and sustainability. Polymeric hydrogels, with their innate hydrophilicity and tunable water transport properties, have emerged as a leading material platform for this application. However, their native limitations in solar absorption and thermal conductivity constrain overall solar-to-vapor conversion efficiency. This review critically analyzes the material design strategies employed to transform passive hydrogel matrices into efficient photothermal materials. The primary focus is on methodologies to maximize light absorption and optimize thermal management. Key approaches include the integration of photothermal nanoabsorbers, the synthesis of intrinsically absorptive copolymer networks, and the fabrication of interpenetrating or composite structures. Furthermore, engineering the polymeric hydrogel network by precisely tuning cross-linking density, porosity, and effectively localize thermal energy at the evaporation front. By synthesizing recent advances, this review establishes a clear connection between material-level modifications and enhanced system-level performance, providing a roadmap for the rational design of next-generation hydrogel evaporators. Advancing these material strategies is essential for transitioning SVG from a promising concept into a practical, scalable technology for sustainable water production.