Preparation Of Heteroatom-doped Porous Carbon Nanosheets By Sugar Blowing And Its Electrochemical Properties

Traditional supercapacitors are increasingly widely used in electric cars and electronic products,but with the rapid development of new flexible electronics and wearable devices,the market is in urgent need of research and development of high-performance micro-supercapacitors.Currently,carbon materials based on traditional graphene or three-dimensional graphene/carbon nanotube composites are difficult to meet the requirements of high-performance micro-supercapacitors,so new carbon materials need to be further developed.Heteroatom-doped porous carbon materials because of its high porosity and specific surface area,and doped N,B,P,S and O heteroatoms to into porous carbon skeleton as constraint capacitor active site.Thus,using green biomass raw material to prepare heteroatom-doped porous carbon materials with high doping efficiency in a control and convenient way have become one of the highlights in agro-scientific research of the supercapacitor electrode materials.For this reason,this paper used a new deep eutectic solvent system and combined with sugar blowing method to prepare heteroatom-doped carbon nanosheets,and studied the effects of composition ratio,carbonization temperature and heating rate on the base N-doped carbon nanosheets.In order to enhance the performance of pseudocapacitance,N/S co-doped carbon nanosheets were prepared by composite technology.Moreover,in order to increase the pore volume and specific surface area of the based N-doped carbon nanosheets to obtain the porous structure,the N-doped porous carbon nanosheets was prepared with different activators,and its morphology,structure and electrochemical performance were analyzed and tested.In addition,N-doped porous carbon nanosheets were prepared as micro-supercapacitors to test their specific capacitance and cyclic stability.The main contents and conclusions of this thesis are as follows:1.The influence factors of composition ratio,carbonation temperature and heating rate of N-doped carbon nanosheets prepared by glucose-urea deep eutectic solvent system were studied:?1?When the molar ratio of glucose to urea is 20:80,heating at a rate of 4?/min up to 1000?for 3 h.The obtained N-doped carbon nanosheets has the best performance,with the nitrogen content of 4.58 wt%.When the current density is 0.5 A g^-1,the specific capacitance is 45.1 F g^-1.?2?Replacing some urea in the system with thiourea, when the molar ratio of glucose:urea:thiourea is 20:70:10 and 30mg Fe?OH?3 is added,a new deep eutectic solvents system can still be formed when the four compounds are mixed,N/S co-doped carbon nanosheets were prepared by heating up to 1000?at a rate of 4?/min up to 1000?for 3 h. Fe increases the graphitization degree of carbon materials,with the content of N is 4.97 wt%and S is 0.32 wt%.When the current density is 0.5 A g^-1,the specific capacitance is 107.6 F g^-1.2.In order to increase the porosity effectively,three different activators KOH, Ca Cl₂and H₃PO₄were used to activate the N-doped carbon nanosheets for pore making.The experimental results showed that KOH had the best effect, and the specific surface area of the obtained carbon material could reach 1169.9 m²g^-1.When the current density is 0.5 A g^-1,the specific capacitance is 298 F g^-1.Furthermore,the N-doped carbon nanosheets of different component proportions were activated by KOH,and it was found that the activation process did not affect the law of specific capacitance,which proved that the formation structure of the precursor had a crucial effect on the performance of the product.3.The electrochemical performance of N-doped porous carbon nanosheets treated by KOH activation was measured by laser method.When the current density is 0.2 m A cm^-2,the area ratio capacitance reaches 23.2 m F cm^-2, which is far better than the performance results of most micro-supercapacitors made of carbon materials on the market.Moreover,it displays an excellent cycling stability with 90.2%retention even after 5000 cycles.