Study On Preparation And Evaporation Performance Of Photothermal Evaporator Based On Environmental Heat Absorption

With the gradual deterioration of the problem of water resources shortage,how to obtain clean water with the utilization of new energy sources has become one of the most extensive research hotspots.As an environmentally friendly,economical and efficient renewable resource,solar energy shows great potential in the field of alleviating the shortage of clean water resources.Therefore,solardriven steam generation technology is proposed and developed.Interface solar steam generation technology can display efficient evaporation performance,in which the photothermal materials can harvest and then convert solar irradiation into heat,and locate the heat on the evaporating surface.Effective energy management is the key to optimizing the evaporation performance of the solardriven steam generation,thus the choice of photothermal materials and the structural design of the water evaporator have a significant effect on promoting the evaporation performance.In this work,we prepared two kinds of solar evaporators from two perspectives of materials and structures,which exhibit efficient evaporation performance via absorbing heat from the environment to accelerate water evaporation.Specific research contents are as follows:(1)To better improve the evaporator water evaporation performance,we synthesized a MXene@PVA@cigarette filter(MPCF)solar-driven water evaporator with high evaporation efficiency through combining cellulose acetate based cigarette filter(CF)and MXene.First,the hydrophilicity and quasi ordered structure ensure the excellent water transport capacity of cellulose acetate based cigarette filter.Second,as a new photothermal material,MXene can fully absorb and transform sunlight.Third,in order to improve the stability of the evaporator,we chose polyvinyl alcohol(PVA)as the binder of MXene and CF skeletons and fabricated a MPCF evaporator.To enhance the photothermal water evaporation rate through extracting energy from the environment,we introduced the cold evaporation surface with a certain height between solar evaporation surface and bulk water,and then discussed the influence of the change of height for evaporation performance.The results show that when the height of evaporator exposed to the environment is 6 cm,the evaporation rate of 3.34 kg m^-2h^-1 and the solar-vapor efficiency of 130.0%can be achieved under one sun illumination,which is far above the theoretical limit,confirming the great potential of this strategy for practical applications.(2)To achieve the purpose of efficient evaporation,we prepared a reduced graphene oxide@cigarette filter(RGO@CF)composites,which utilized not only the excellent sunlight absorption performance of reduced graphene oxide but also the hydrophilic and quasi ordered water transfer structure.We selected ascorbic acid to weak reduce graphene oxide(GO)and abundant polar oxygencontaining functional groups are retained consequently,which ensured the hydrophilicity of the RGO@CF composite.To utilize environmental energy,we designed a RGO@CF evaporator with different height,which could obtain larger side area extracting heat from the environment through temperature difference driving.The results show that the RGO@CF evaporator with 5 cm height can exhibit outstanding solar-driven steam generation performance at the light intensity of 1KW m^-2,achieving a evaporation rate of 2.78 kg m^-2h^-1,corresponding to an energy conversion efficiency of 130.4%(well above 100%).