Preparation of Three-dimensional Graphene-based Sponge as Photo-thermal Conversion Material to Desalinate Seawater

Water shortage has become one of the major threats to human society over the past centuries. The new interfacial solar evaporation is undoubtedly an attracting technology to solve this problem. Herein, graphene aerogel(GA) and graphene oxide/melamine sponge composite material(GO-MS) were prepared through a two-step reduction and one-step freezing method as photo-thermal materials to evaporate pure water and seawater. The proper concentrations of the graphene oxide(GO) dispersion for their preparation were investigated, which is 7 mg/mL for GA, and 5 mg/mL for GO-MS. The evaporation rates of GA are 1.40 kg/(m(2)center dot h) for pure water and 1.21 kg/(m(2)center dot h) for seawater, while for GO-MS it is 1.63 kg/(m(2)center dot h) for pure water and 1.45 kg/(m(2)center dot h) for seawater, respectively. The composite material not only reduces the usage of GO, but also shows better photo-thermal conversion properties. Furthermore, the heat loss of evaporation system was calculated and the method of further enhancing photo-thermal conversion efficiency was deduced, which will provide a strong basis for guiding the design and development of graphene based three-dimensional materials and further exploration in this field.