Preparation Of Bionic Through-Hole Structure And Its Light-to-Heat Conversion Performance By Ice Template Method

The shortage of clean fresh water is a global concern,and the use of solar energy to generate water vapor to obtain clean fresh water is considered to be an environmentally friendly,low-cost production method.As a green and sustainable source of renewable energy,solar energy has made progress in the fields of photocatalysis,photovoltaics and photothermal conversion.In terms of photothermal conversion,extensive research has been conducted on power generation,desalination,sewage treatment and solar water heating systems.Among the factors that affect the efficiency of solar evaporation,the evaporation rate of water is particularly important,so the transportation and evaporation of water are highly valued.There are many bionic strategies for directional water transport in nature.Trees play a key role in the global water cycle by relying on water transport from xylem blood vessels and channels and water transpiration through leaves under solar radiation.The internal pipes of trees can transport a large amount of water in a direction.Inspired by this,many bionic designs have been proposed to obtain pure water through solar energy collection and thermal management systems.For water evaporation driven by solar radiation,enhanced sunlight absorption and heat management,local heat generation can improve water evaporation efficiency.However,there are still great challenges in the rapid transportation of large amounts of water and the rapid local heating of photothermal materials.Therefore,there is an urgent need for the orientation,rapid and continuous transportation of water,and rapid heat evaporation on the surface.In this thesis,the ice template method was used to prepare wood-like ordered porous material,which has attracted more and more attention due to its rapid,scalable,low-cost,and environmentally friendly characteristics.Here,the directional freezing ice template method was used to prepare chitosan/graphene oxide composite aerogels and double-layer chitosan/Ti₃C₂Tx-PEI with an ordered porous structure and wood-like structure.The directional water delivery characteristics facilitated to improve the evaporation rate and light-to-heat conversion performance under sunlight.In the first part of the thesis,a simple physical blending method was used to uniformly mix graphene oxide and chitosan solution.After directional freezing,a chitosan/graphene oxide composite aerogel was successfully prepared,and different CSs were explored.The influence of GO content on its mechanical stability,porosity,thermal insulation and wettability was studied.Chemical reduction method by hydrazine hydrate was employed to prepare CS/r GO composite aerogel with excellent light-to-heat conversion ability,which ensured its feasibility as a solar steam generator by studying its light absorption capacity,heating rate,and evaporation rate.In the second part of the thesis,a polyethyleneimine-coated MXene layer(Ti₃C₂Tx-PEI)was sprayed onto the CS aerogel as a solar absorber to drive water evaporation under solar radiation.Polyethyleneimine can be stably wrapped on the surface of Ti₃C₂Tx sheet due to static electricity in solution.The protection of polyethyleneimine can also prevent Ti₃C₂Tx from being oxidized to Ti O₂.The structural characteristics of such a double-layer CS/Ti₃C₂Tx-PEI aerogel can achieve strong anti-gravity water transport through highly ordered through pores,and the double-layer structure design can ensure the thermal insulation of the aerogel while reducing light irradiation.The heat conversion process is concentrated on the evaporation surface to improve the efficiency of light-to-heat conversion.Due to the aligned channels and micron holes,the transportation distance in 15 s is>2 cm,and the high water evaporation rate of 3.99 kg m^-2 h^-1 under the irradiation of three sunlight intensities,the light-to-heat conversion efficiency reaches 90%.The ordered porous material showed great advantages in solving the problem of water transportation and evaporation of clean fresh water.