Preparation And Application Study Of Micro/Nano Sized Materials Based On Photothermal Conversion Effect

Solar energy is a green,renewable and most widely distributed energy source.In recent years,photothermal derived applications have attracted the interest of many researchers and great efforts have been made to expand the application areas of solar energy conversion and improve the conversion efficiency.Thermal energy is utilized for desired purposes such as water purification,desalination,power generation,photothermal anti-icing/de-icing,photocatalysis,sterilization,and so on.Among all the applications,photo-thermal evaporation for desalination and water purification has received the most attention because it can directly utilize solar energy to produce fresh water and can solve the challenge of fresh water shortage in many countries.However,compared with photothermal water evaporation,research on other applications has received less attention,and photothermal de-icing technology is still in its infancy,with related research remaining only at the laboratory research stage and ignoring practical operating conditions.In response to the two urgent problems raised above,this work proposes corresponding coping strategies,respectively.An aerogel evaporator for seawater desalination and wastewater treatment through photothermal evaporation is developed,which can still perform stably in various harsh environments while ensuring the preparation cost;a photothermal superhydrophobic coating that can be used as a passive anti-icing/active de-icing coating in low-temperature environments is also prepared,which can not only cope with the problem of icing,but also carry out the application of oil-water separation,as well as photothermal evaporation,and so on.The specific research work is respectively:（1）Composite diatomite/acidified carbon nanotube aerogel for efficient solar vapor generation and wastewater purification.Using agar powder as a gel agent,diatomite and acidified multi-walled carbon nanotubes were combined by freeze-drying method to make an interfacial contact aerogel solar evaporator.By observing its micro-morphology,optical absorption properties,and water-absorption properties;and taking the evaporator as a research object,its wide range of applications is proved by adjusting the evaporation rate in different light intensities and simulating different sea areas.The experimental results show that the light absorption rate of the interfacial evaporator can reach 95%,and can be further improved under wetting conditions.Under the irradiation of 1 sun intensity,the water evaporation rate of the aerogel was 1.67 kg m^-2h^-1,and the photothermal conversion efficiency was 91%.The heat loss is further reduced by the addition of an insulating layer,and the evaporation rate of the evaporator is further increased to 1.72 kg m^-2h^-1under the same light conditions.It is also possible to produce potable water from seawater,lake water,and even strongly acidic/alkaline water,with a removal rate of organic dyes close to 100%.Most importantly,the cost of producing this aerogel is only$6.67.（2）Carbonized/hydrophobically modified bilayer diatomite aerogel for efficient solar-driven water evaporation.Carbonized diatomite was utilized as a light-absorbing material,and the diatomite was hydrophobized by aminosilicone oil,while water channels for water transport were prepared by a secondary casting process.The water evaporation rate was further enhanced by limiting the temperature diffusion from the evaporator surface to the water body.The photothermal evaporation performance was optimized by investigating different thicknesses of the insulation layer,and the temperature of the light-absorbing layer was verified using finite element simulations.The experimental results show that the evaporation rate of the evaporator with a 10mm thickness of the thermal insulation layer can reach 1.76 kg m^-2h^-1with a photothermal conversion efficiency of 93.5%under 1 sun intensity,meanwhile,it can show good evaporation rate in water bodies under various harsh conditions,and also performs well for the removal of microbiota in the water body,and exhibits a good cyclic stability The system has a good evaporation rate in all kinds of harsh conditions.（3）Micro-and nanosized MnO₂composite superhydrophobic coatings for anti-icing/de-icing and various photothermal applications.Superhydrophobic photothermal coatings with surface micro-and nanostructures were prepared by spraying double-sized MnO₂with PDMS.The hydrophobicity angles of the coatings were investigated on different substrates and in response to different kinds of liquids,while the anti-icing and de-icing performance of the coatings were tested at an ambient temperature of-15℃ using the thermal response of the coatings under light.The experimental results show that the coating can be heated from room temperature to high temperatures above 80℃in 300 s under 1 sun intensity simulated light.At the same time,the coating can effectively extend the icing time to 655 s.30μl of small ice droplets can be completely melted in 42 s,and 300μl of large ice droplets can be melted in 186 s.In addition,based on the photothermal effect,the coating can also be used to prevent icing and de-icing.In addition,based on the photothermal effect,the coating can be extended to oil-water separation,personal thermal management,as well as seawater desalination,waste water treatment and other applications.The Janus-type solar evaporator made by spraying the coating on melamine sponge can reach an evaporation rate of 1.70 kg m^-2h^-1and photothermal conversion efficiency of92.6%.（4）Flexible MnO₂/Fe₃O₄composite superhydrophobic photothermal coating for anti-icing/de-icing and various photothermal applications.The photothermal coating was made of magnetically responsive Fe₃O₄nanoparticles and MnO₂composite,which was applied to solve the problem of ice accumulation on curved substrates such as power lines by spraying on PDMS or fabric substrates,which endowed the coating with flexibility so that it could be tightly adhered to curved substrates under a magnetic field without the need of any adhesive.The experimental results show that the coating has good thermal cycling stability under 1 sun intensity simulation,the icing time is extended to 674 s at-15℃,and 3 mm thick ice can be melted in 223 s,while the ice adhesion strength is 32.4 KPa.The coating is sprayed on the steel mesh to make a"ship-shaped"structure,and a vacuum pump can be connected to realize the fast and easy adhesion of the coating on the curved substrate.A vacuum pump can be connected to realize rapid and continuous oil-water separation.Similarly,a Janus-type solar evaporator made of melamine sponge sprayed with the coating achieved an evaporation rate of 1.73 kg m^-2h^-1at 1 sun intensity,with a photothermal conversion efficiency of 92.9%.