Preparation And Properties Of Carbon Aerogel Electrode Materials For Wood Cellulose Nanofibers

Under the background that the concept of sustainable development has become a global consensus,more and more attention has been paid to the rational development and utilization of biomass materials.Cellulose,widely existing in the cell wall of biomass materials,is the most abundant natural polymer in nature.Cellulose nanofiber(CNF)was prepared by nanocrystallization of cellulose.Then,a three-dimensional network structure carbon aerogel(CA)material with high electrical conductivity,high specific surface area and wide pore size distribution was constructed.It is a good choice for supercapacitor electrode materials.However,due to the low capacitance of carbon aerogels,the low energy density used in supercapacitors hinders the development of CA in supercapacitors.Therefore,carbon materials need to be modified to improve their capacitive properties.Among them,nitrogen doping can not only improve the surface properties of carbon materials,enhance the wettability of carbon materials,but also improve the conductivity of carbon materials,so as to improve the electrochemical performance of CA.Therefore,this experiment uses cellulose as raw material and urea as nitrogen source to obtain a low cost and high specific capacitance supercapacitor electrode material by nitrogen doping treatment of cellulose carbon material.The experimental results show that:(1)Using cellulose powder as raw material,different sizes of CNF were obtained by grinding,high-pressure homogenization and other methods.Different sizes nanocellulose has an important influence on self-assembly performance.At the same time,the electrochemical properties of CNF aerogels prepared by high temperature carbonization under different treatment conditions are also quite different.When the cellulose was homogenized 20 times,the aerogels had the best self-assembly performance and the highest electrochemical performance.(2)Using cellulose powder as raw material,CA were obtained at different carbonization temperatures.The carbonization temperature not only affected the degree of carbonization and conductivity of CA,but also had an important effect on the internal morphology and structure of CA.With the increase of carbonization temperature,the lamellar structure of CA decreased,fibrous structure increased,and carbon aeration occurred.The specific surface area and pore volume of the areogel increased.When the carbonization temperature reached 800?,the mesoporous pore volume of the CA was the largest.When the current density was 0.5 A g-1,the specific capacitance of the CA-800 could reach 172.7 F g-1,and the cyclic stability was stable.After 5000 cycles of cyclic voltammetry,the specific capacitance of the CA remained 89.43%of the initial capacitance.The electrochemical properties of gel electrode materials are very important.CA prepared from CNF of different concentrations at the same temperature have different electrochemical properties due to their different internal structures.(3)A nitrogen-doped carbon material with simple preparation,low cost,high nitrogen doping content and environmental protection is provided.Using CNF powder as raw material and urea as nitrogen source,nitrogen doping treatment of CA through gas phase cycling is an effective way to further enhance the electrochemical performance of CNF carbon materials.Urea has a crucial effect on the pore structure and specific surface area of CNF aerogels and CA,because of nitrogen atoms,the CA-N has a multi-stage pore structure.It also can increase the surface wettability of the carbon material.Urea has different effects on the treatment of CNF aerogels and CA,because the bonding structure inside the carbon materials is weak,and nitrogen atoms are more easily bound to the carbon materials when nitrogen doping is applied.The quality of the nitrogen doped urea is about that of the CNF aerogels and CA.When the quality of nitrogen doped urea is 3g,the specific capacitance of nanocellulose aerogel and carbon aerogel condensate can reach the best performance.When the current density is 1 A g-1,the specific capacitance of the sample CA-N can reach 253.7 F g-1.Finally,the nitrogen doped carbon aerogel material is assembled into a simple supercapacitor.In this paper,the wood cellulose derived from green and sustainable development is used as precursor.The CNF obtained by acid hydrolysis,grinding and high pressure homogenization has a great influence on the properties of the self-assembled aerogels.Carbonization of CA at different temperatures is not only in the degree of carbonization,but also in the internal structure of CA.At the same time,the internal structure of CA has a great relationship with their electrochemical properties.Nitrogen doped CA prepared with urea as nitrogen source have better electrochemical properties,while nitrogen doping at different stages of nitrogen treatment is different.Nitrogen doped CA can be used as an excellent electrode material for supercapacitors.