Design And Properties Of Graphene Based Photothermal Conversion Materials

Solar steam technology is used in seawater desalination,not only to alleviate the shortage of energy,but also to provide clean drinking water.It is of great scientific significance and application value to design and prepare photothermal materials applied to the economic,efficient and stable solar energy steam technology.An excellent solar light-to-heat conversion system should have:1.Efficient light absorption and light-to-heat conversion;2.Effective heat management;3.Good water supply and steam collection.Therefore,in this paper,reduced graphene oxide is used as the photothermal material,and sodium alginate/starch/calcium carbonate three-dimensional aerogel is used as the insulating support substrate,two composite film systems of aluminum foil/graphene/trimanganese tetraoxide and graphene/polyethyleneimine were designed and prepared as light-heat steam conversion materials,the structural composition of the two composite films was studied,the light-heat conversion performance and The efficiency of solar steam generation and the mechanism of light-to-heat conversion were discussed.The main research results obtained are as follows:1)Preparation and photothermal properties of aluminum foil/graphene/manganous oxide(Al/RGO/Mn₃O₄)composite film.The GO/Mn₃O₄ colloid was synthesized by self precipitation method and then the Al/RGO/Mn₃O₄ composite film was prepared with aluminum foil as carrier.The interface evaporator was constructed by the synthesis of alginate/starch/calcium carbonate three-dimensional aerogel as the thermal insulation layer.The water evaporation device can achieve good light absorption,timely water supply and good thermal management.The light absorption capacity of the Al/RGO/Mn₃O₄ composite film is up to 99%.Under the light intensity of 1 KW·m^-2,the water evaporation rate of 1.65kg·m^-2·h^-1is achieved,and the water evaporation efficiency can reach 90%,even at In the more severe seawater,under the light intensity of 1 KW·m^-2,it can also maintain the water evaporation rate of 1.26 kg·m^-2·h^-1,and has good salt corrosion resistance.At the same time,the Al/RGO/Mn₃O₄photothermal conversion composite material showed good cycle stability in the water evaporation cycle test.The water evaporation rate of the entire system in the 20seawater cycle tests remained basically stable,which provided the possibility for large-scale application in the future.2)Preparation and photothermal properties of graphene/polyethylenimine composite film.The reduced graphene oxide/polyethyleneimine composite film is prepared by chemical cross-linking,and the synthetic sodium alginate/starch/calcium carbonate three-dimensional aerogel is used as the heat insulation layer to construct an integrated light-to-heat conversion water evaporation device by freeze drying technology.The composite membrane system has high absorbance properties of graphene absorbable material,high hydrophilicity of polyethylenimine,and ductility and high mechanical strength of 3D aerogel structure.The photothermal vapor rate of the system is 1.35 kg·m^-2·h^-1 and the light absorption capacity is up to 95%.The innovation of the structure is to transform the traditional two-layer structure(upper absorption layer,lower water transmission and insulation layer)into an integrated three-dimensional aerogel structure with high controllability,which can reduce the reflection and refraction of light by optimizing the structure of aerogels,thereby maximizing the absorption efficiency of light.In addition,the micron submicron structure of three-dimensional aerogel makes the salt particles in seawater not aggregate in the channels,so it has a stable solar evaporation rate under high salinity seawater.It provides a feasible scheme for the design of the integrated structure photothermal steam converter.