The Design Of Plasma Resonance Enhanced Composite Films And Their Applications For Solar Photothermal

Solar energy plays an important role in various energy fields,and the energy needed by human beings is no longer dependent on fossil fuels only.It is very important to develop solar devices that have competitive advantages and can meet with various application requirements in the future.Some semiconductor materials and noble metal nanoparticles with plasmon resonance effect,such as copper sulphide,gold nanoparticles and so on,can produce good photothermal effect.By compounding with thin film substrate,plasmon resonance enhanced photothermal conversion films can be obtained,which can be used in seawater desalination,agriculture and other fields.Seawater desalination technology based on photothermal conversion materials can theoretically provide infinite and stable quality water without damaging the natural freshwater ecosystem.In addition,the use of energy has the problem of time matching,it is of great significance to collect energy in advance and use it at the right time.Therefore,photothermal conversion films with heat storage performance are expected to have a wider use in the future,such as agricultural greenhouses,temperature-adjusted buildings/clothes and other fields.In this paper,three kinds of films which can achieve good thermal management in the solar energy field were prepared,including Copper sulfide-Polyethylene composite film,Copper sulfide-Cellulose composite film and Polyethylene glycol-Polyvinyl alcohol-Gold nanoparticles composite film.At the same time,their preparation methods,structure characterization and applications in photothermal conversion,seawater desalination and agriculture were studied.The first is the study of Copper sulfide-Polyethylene photothermal conversion film for seawater desalination.Based on the strategy of enhancing water evaporation at the interface,a Copper sulfide-Polyethylene composite film with high light absorbance(>93%),low thermal conductivity(0.067 W m-1 k-1),self-floating,hydrophilic and porous properties was prepared by hydrothermal method.Copper sulfide is a kind of p-type multifunctional semiconductor.Due to the plasma resonance effect on its surface,the band transition of nano copper sulfide can generate absorption to the special band of near-infrared light,and the infrared band in the solar spectrum directly generates thermal effect,so it can be used as an ideal solar energy absorption material.Besides,the black surface of the porous polyethylene film can absorb most of the sunlight and reduce the loss of sunlight due to reflection.The simulated seawater surface temperature covered with Copper sulfide-Polyethylene photothermal conversion film can reach 37.6 ? and the efficiency of solar photothermal evaporation water can reach 63.9%under simulated solar irradiation with a power density of 1 kW m-2.At the same time,the film had good stability.In addition,based on the interface heating,a simple solar distillation unit was designed and assembled to simulate the desalination process of solar seawater desalination.Due to the excellent photothermal conversion effect of the Copper sulfide-Polyethylene composite porous film and the small heat loss of the solar distillation device,the Copper sulfide-Polyethylene composite porous film is expected to be applied in the strategy of large-scale production of fresh water in the future.The second is the study of Copper sulfide-Cellulose composite photothermal conversion film for seawater desalination.At present,cellulose films on the market have excellent mechanical properties,high porosity and good chemical reaction activity.The preparation method has the advantages of simple synthesis,large-scale preparation,environmental friendliness.In addition,cellulose has low thermal conductivity and good hydrophilicity,which facilitates effective water transport.Therefore,cellulose can be used as an auxiliary material to realize interface heating,and can be used as a substrate for in-situ growth of photothermal conversion materials to realize the application of seawater desalination and so on.In this paper,a large number of hollow copper sulfide nanoparticles were successfully grown on the surface of carbon-containing black cellulose film by hydrothermal method through pretreatment.Under simulated sunlight irradiation with a power density of 1 kW m-2,the temperature can be raised to 70 ?.For seawater desalination process,the efficiency of solar photothermal evaporation water is close to 85%.The third is Polyethylene glycol-Polyvinyl alcohol-Gold nanoparticles solid-solid phase change composite film with photothermal conversion and thermal energy storage and release functions.The composite film is based on polyvinyl alcohol,trace gold nanoparticles with surface plasmon resonance function are added into the polyvinyl alcohol to realize photothermal conversion,and polyethylene glycol is added as a phase change energy storage material.When external illumination is applied,the film is firstly photothermal converted by gold nanoparticles,and then the converted heat energy is stored by polyethylene glycol phase change material,so that the energy storage efficiency is improved by 201%.By limiting the movement of polyethylene glycol molecular chain in the three-dimensional network of polyvinyl alcohol,the solid-solid phase change is realized,and the problems of encapsulation,leakage existing in the use process of the traditional phase change material are solved.In the process of latent heat storage,the temperature change is small,the energy storage density is high,and the stability of composite film is high,and has wide application in the aspects of heat preservation of agricultural vegetable greenhouses,temperature regulating buildings/clothes,photothermal power generation devices and so on.The films were characterized by XRD,TEM,SEM,IR and DSC.