Biomass-based Synthesis Of Mesoporous Carbon Materials And Their Electrochemical Application

Mesoporous carbon materials have attracted much attention in the fields of catalytic reaction,energy storage,drug carrier and so on because of their large specific surface area,adjustable pore structure parameters and easily modified interface characteristics.As an electrode material,it has also received extensive attention in the field of electrochemistry.However,when it is used as electrode material,it still has the problems of poor wettability and few active sites,resulting in poor capacitance,rate performance and cycle life of the capacitor.The incorporation of heteroatoms will change the problem of mesoporous carbon materials as electrode materials;The incorporation of nitrogen atoms is a common strategy to improve the wettability of carbon materials.The incorporation of metal atoms will improve the active sites of materials.Using SBA-16 and block copolymer as templates,selecting appropriate precursor molecules and heteroatoms to crosslink the block copolymer,and then removing the template,heteroatom doped mesoporous carbon materials can be obtained.The heteroatom content and morphology of mesoporous carbon materials can be controlled by controlling the amount of raw materials.Moreover,the content of heteroatoms and pore structure can be regulated by means of ultrasound.In addition,the best method of synthesizing mesoporous carbon was explored through different interaction forces.Based on this idea,mesoporous carbon materials with different morphological structures were designed and synthesized in this paper.At the same time,the relationship between the electrochemical properties of mesoporous carbon materials and their structure,element morphology and content was systematically studied.The results are as follows:（1）By changing the quality and roasting temperature of ammonium molybdate,the pore structure and heteroatom content can be effectively controlled to improve the capacitance,rate performance and cycle life.The results show that with the increase of the mass ratio of starch to ammonium molybdate,the specific surface area and heteroatom content first increase and then decrease,indicating that agglomeration will occur when the amount of ammonium molybdate is high,which is not conducive to entering the pore.With the increase of calcination temperature,the specific surface area and heteroatom content first increase and then decrease,indicating that when the temperature is too high,the carbon material collapses and the pore structure is seriously damaged.The electrochemical evaluation results show that the specific capacitance increases with the increase of specific surface area and heteroatom content.When the mass ratio of starch to ammonium molybdate is 3 and the calcination temperature is 800℃,the carbon material NMC/Mo-3-800 has the most suitable specific surface area(240.164 m²g^-1),nitrogen element（3.18 at%）and molybdenum element（6.65 at%）,and it has the highest specific capacitance(that is,under the current density of 0.5 A·g^-1,the specific capacitance is 356 F·g^-1),And when the current density is 20 A·g^-1 for 5000 cycles of charge and discharge,there is still 71%capacitance retention,showing good cycle stability.（2）By changing the power and time of ultrasound,the pore structure and heteroatom content can be effectively controlled to improve the capacitance,enhance the magnification performance and cycle life.The results show that with the increase of ultrasonic power and time,the specific surface area and heteroatom content first increase and then decrease,indicating that ultrasound has a strong influence on the crosslinking of precursor,heteroatom and block copolymer,and the interaction force will be enhanced under a certain ultrasonic power and time.The electrochemical evaluation results show that the specific capacitance increases with the increase of specific surface area and heteroatom content.When the ultrasonic power is 1KW and the ultrasonic time is 10min,the carbon material NMC/Fe/Co-1-10 has the most suitable specific surface area(352.72 m²g^-1),nitrogen（12.91 at%）,iron（1.79 at%）and cobalt（1.41 at%）,It has the highest specific capacitance(413 F·g^-1 at 0.5 A·g^-1),and it still has 86%capacitance retention after 5000 cycles of charge and discharge at the current density of 10 A·g^-1,showing excellent cycle stability.（3）The pore structure and nitrogen content can be effectively controlled by changing the of templates providing different bond energy and different halogen atoms under the same bond energy,so as to improve the capacitance,optimize the rate performance and cycle life.The results showed that the specific surface area and nitrogen content reached the highest under the action of hydrogen bond,ionic bond and ionic bond provided by chloride ion.The electrochemical evaluation shows that the specific capacitance increases with the increase of specific surface area and nitrogen content.The carbon material Cl-HINMC prepared by hydrogen bond and ion bond（chloride ion provides ion bond）has high specific surface area(606.10m²g^-1)and nitrogen content（2.32 at%）,which shows the highest specific capacitance(313.2F·g^-1 at 0.5 A·g^-1),and performs cyclic charge and discharge 5000 times at 20 A·g^-1current density,The capacitance retention rate is still 84.36%,showing good cycle stability.