A flexible photothermal cotton-CuS nanocage-agarose aerogel towards portable solar steam generation

Solar-steam generation provides an economically efficient pathway to produce clean water by using solar irradiation as an energy source. While this strategy is highly suitable for portable and small scale water purification for individuals, families and those living in remote areas, the development of highly efficient and flexible photothermal materials which can be easily transported for storage and deliver is required. In this study, a commercial degreasing cotton, photothermal CuS yolk-shell nanocages and agarose were combined to produce a highly flexible photothermal aerogel which delivered a high energy efficiency (94.9%) for solar-steam generation under 1.0 sun irradiation, corresponding to a water evaporation rate of 1.63 kg m−2 h−1. The preparation of the photothermal aerogel can be easily scaled up due to the simplicity of the applied casting method. The obtained aerogel showed excellent stability for solar steam generation with no degradation in performance after at least 15 cycles. The salinity of the clean water produced during solar-thermal desalination of seawater was only 0.54 ppm. The raw materials of cotton, agarose and CuS are all cost effective, thus this flexible photothermal aerogel has showed great potential for practical application in portable solar-thermal evaporators.