Preparation Of Biomass Based Carbon Aerogel And Its Application In Energy Harvesting

Carbon aerogel is a type of carbon nanomaterial with special three-dimensional network structure.Due to various characteristics such as light weight,high specific surface area,high porosity,excellent electrical conductivity and thermal conductivity,etc.,it has great application potential in the fields of electrode materials,electromagnetic shielding materials,phase change stored energy materials,electrocatalytic carriers,adsorption carriers,etc.However,the raw materials of the conventional organic carbon aerogel are derived from non-renewable coal,coke,etc.,which lead to high cost and great pollution.In this paper,the biomass waste bagasse,which is abundant in reserves and could be quickly regenerated,is used as raw material.The bagasse nanocellulose carbon aerogel is prepared,and the microstructure and properties of carbon aerogel are studied systematically.The composite phase change materials were prepared by combining bagasse nanocellulose carbon aerogel with paraffin.The thermal conductivity and photothermal conversion properties of the composite phase change materials under different process conditions were studied.Specifically,the main content includes the following three aspects:?1?In this work,the bagasse was utilized to prepare carbon aerogel.First,the bagasse was alkaline-hydrolyzed and bleached repeatedly by NaOH solution and hydrogen peroxide,respectively,to obtain bagasse cellulose nanofibrils with higher aspect ratio.And then a certain concentration of nanocellulose solution was prepared.After that,the carbon aerogel with a certain of strength was finally obtained through lyophilizing and high-temperature carbonizing under nitrogen atmosphere.This preparation process realized“turning waste into treasure”in the utilization of raw materials,and fully exerted the use value of bagasse,and avoided the use of dangerous chemicals in the preparation process,which meets the requirements of green chemistry.The prepared carbon aerogel has a density of only 3.2 mg·cm^-33 and can be restored to its original state when the volume is compressed to 40%.The BET specific surface area is371m²·g^-11 and the total pore volume is 0.21 cm³·g^-1.?2?The effects of different activation conditions on the degree of graphitization,microstructure and pore structure of bagasse nanocellulose carbon aerogel were studied.Results showed that the activated carbon aerogel has a richer internal pore structure,which leads to an increase of 137%in BET specific surface area,a total pore volume increase of 167%,and an increase of 148%in specific capacitance compared to the unactivated one.?3?The composite phase change material was prepared by compounding carbon aerogel with paraffin.The effects of carbon aerogel prepared at different carbonization temperatures on the adsorption of paraffin and the paraffin content on the composite phase change material were studied.The effect of leak rate and photothermal conversion efficiency.Results showed that the carbon aerogel has high adsorption to paraffin,and its maximum adsorption capacity could reach 100 times its own mass.Furthermore,the thermal conductivity of composites is raised from 0.245 W·m^-1·K^-11 to 0.441 W·m^-1·K^-1through the addition of carbon aerogel.Meanwhile,the introduction of carbon aerogel also significantly improved the photothermal conversion efficiency of the material.