A hybrid hydrogel with protonated g-C ₃ N ₄ and graphene oxide as an efficient absorber for solar steam evaporation

Carbon-based composites have gained renewed research interest in solar steam generation due to their low cost, durability and high photo-thermal efficiency. However, large-scale applications of carbon-based composites are restricted due to their high-emissivity in a high temperature condition. Here, by using melamine and graphene oxide as raw materials, the protonated g-C ₃ N ₄ /graphene hybrid hydrogel is prepared via a simple hydrothermal co-assembly method. The obtained self-floating hydrogel can convert the most of solar energy into thermal energy as well as pumping the underneath water to produce steam continuously. Furthermore, the existence of protonated g-C ₃ N ₄ decreases the emissivity of the composites. As a result, an average evaporation rate of 4.11 kg m ⁻² h ⁻¹ and a superb solar steam generation efficiency of 94.5% under 3-sun illumination are achieved. This hybrid hydrogel is highly promising to provide a solution to enhance solar water evaporation and desalination performance.