Preparation And Electrochemical Performance Study Of Sugarcane Tip-based Carbon Materials

Supercapacitor（SC）is a newly emerged energy storage element.It has received extra attention due to its unique advantages such as long life,high efficiency in charging and discharging,good cycle stability,and safe and stable operation.Electrode material is the key element of supercapacitors.Green and renewable biomass as the raw material for preparing electrodes can not only improve the utilization value of biomass and avoid wasting resources,but also reduce the preparation cost,which has become a research hotspot in the field of supercapacitors.Sugarcane tip is the agricultural waste left in the field after sugarcane harvest.The annual production of sugarcane tip is huge,but the utilization rate is very low,resulting in the waste of resources.In this paper,sugarcane tip is used as raw material to prepare sugarcane tip-based carbon material for supercapacitor electrode material.Urea was used to modify the nitrogen doping of the sugarcane tip-based carbon material and further prepare the activated carbon flexible membrane electrode to study the electrochemical performance The details of the study are as follows:（1）Sugarcane tip-based activated carbon was prepared using sugarcane tip as the precursor,supplemented with KOH powder as the activator.The structure and electrochemical properties of the prepared sugarcane tip-based carbon were investigated as influenced by the activation temperature and the ratio of activator The sugarcane tip-based activated carbon has a layered structure and rich pores.The optimum process conditions were 600℃activation temperature and 1:2activator ratio.The prepared sugarcane tip-based activated carbon（ACST-600-2）has 1206.85 m²/g and a pore volume of 0.58 cm³/g,and the pore size is mainly micro-pores below 2 nm.The electrochemical results showed that in the three-electrode system,the ACST-600-2 electrode reached a specific capacitance of 259F/g at a current density of 0.5 A/g.In the two-electrode system,the specific capacitance of the ACST-600-2 sample was 228.3 F/g at 0.2 A/g,and the energy density of the electrode was 7.93 Wh/kg with a power density of 100 W/kg.（2）On the basis of KOH activation,the research idea of preparing sugarcane tip-based nitrogen-doped activated carbon by KOH activation coupled with urea nitrogen doping modification was proposed.The surface of the prepared carbon material is rich in nitrogen-containing functional groups,and the pore structure changes,with more mesopores,forming a more obvious hierarchical porous structure.Nitrogen-containing functional groups can provide pseudocapacitance,and the hierarchical porous structure promotes ion transport and diffusion,which is conducive to improving electrochemical performance.The influence of nitrogen doping ratio on the properties of activated carbon was discussed.Under the optimum conditions,the sugarcane tip-based nitrogen doped activated carbon（NACST-2）prepared with urea doping ratio of 1:2 has the best electrochemical performance.The specific capacitance reaches 333 F/g at the current density of0.5 A/g and 273.9 F/g at the current density of 10 A/g,with a capacitance retention of 82.3%.（3）The preparation of activated carbon flexible electrodes was investigated.The idea of preparing membrane electrode by co-mixed extraction of MXene（Ti₃C₂）solution and NACST dispersion was proposed.NACST was introduced into the MXene sheet layer as an intercalator,which effectively alleviated the MXene sheet layer stacking and increased the layer distance,promoted the ion diffusion and improved the electrochemical performance.The MXene/NACST-5%membrane electrode prepared under the optimal conditions has the best electrochemical performance:the specific capacitance value is 272.7 F/g at the current density of 0.5 A/g.