Self-floating composite hydrogel for simultaneous solar-driven water evaporation and purification

Solar-driven simultaneous clean water production and organic pollutant photodegradation represent an effective strategy for sustainable treatment of organic wastewater. Here, we design a hybrid hydrogel composed of natural down fiber (DF) and Cu co-doped TiO 2 (DF–Cu@TiO 2 ) combined with DF-derived carbon (DFC) within a chitosan–polyvinyl alcohol matrix. The resulting DF–Cu@TiO 2 /DFC hybrid hydrogel achieves exceptional light absorption, sufficient water supply, and visible light-driven catalytic activity. Consequently, under one-sun illumination, the hydrogel demonstrated an evaporation rate of 1.87 kg m −2 h −1 and achieved a concurrent methyl orange (MO) degradation efficiency of 93.50 % within 5 h. Furthermore, the hydrogel exhibited self-floating capability, maintaining buoyancy continuously for over 7 days. Actual outdoor experiments yielded an evaporation rate of 1.21 kg m −2 h −1 at 12:00 p.m. and a simultaneous MO degradation efficiency of 95.71 % over a 10-h operational period (8:00 a.m.–6:00 p.m.). These findings provide valuable insights for designing multifunctional, self-floating evaporators for advanced wastewater treatment applications, particularly for wastewater containing harmful organic contaminants.