Green Preparation And Supercapacitance Properties Of Biomass-Based Porous Carbon Materials

Nowadays,supercapacitors as a new type of energy storage device with high power density,long cycle life,fast charge and discharge,and green environmental protection have entered the stage of high-speed development and application.However,its relatively low energy density limits its further application.The performance of supercapacitors is mainly affected by electrode materials,and carbon materials are one of the most widely used electrode materials.The methods of preparing biomass porous carbon was used strong acid and alkali,and the preparation steps are complicated,the cost is high and it is bad for environment.How to improve the electrochemical properties of carbon materials,and how to use environmentally friendly preparation methods to reduce costs has become an important issue to be solved urgently.In this paper,we propose two green environmental methods to prepare porous carbon materials by using natural bio-based materials pistachio shell and loofah as carbon source,and testing their properties as supercapacitor electrode materials,we offer new ways to prepare porous carbon electrode materials in a low cost.The main research contents are as follows:1、We use the pistachio shell as the carbon source to prepare porous carbon materials by the method of supercritical hydrothermal and KOH activation,and then we perform physical characterization and electrochemical testing of materials.The method greatly reduces the usage of strong alkali compared to the traditional activation methods.The test results show that the sample S1 shows the best electrochemical performance,and has a high capacitance of 232 Fg-1(260 Fcm-3)at 0.5 Ag-1.100Ag-1 still has a capacitance of 144 Fg-1(161 Fcm-3).After 10000 cycles,the specific capacitance retention rate is above 90%.The two-electrode symmetrical battery test shows the potential application value of the material on the supercapacit or.2、We use walnut shells as the carbon source and the phytic acid as the activator to prepare phosphorus doped porous carbon material by the method of calcination nnder nitrogen.The results show that the degree of graphitization and the pore structure of the prepared material is increased with the addition of proper amount of phytic acid,However,when the amount of phytic acid added is too more,the degree of graphitization is decreased,and the planar structure of graphite is destroyed.The Sample A1 exhibited the best electrochemical performance with a specific surface area of 762 m2g-1 and a specific pore surface area of 581 m2g-1,showing a high specific capacitance(320 Fg-1,0.5 Ag-1 in the 1M H2SO4 electrolyte three-electrode system)and excellent rate performance,still having a retention of 73% at 20 Ag-1.The AC impedance test results show that the material has a lower resistance.The capacitance retention rate is 98% after 10000 cycles at 10 Ag-1 current density,which indicates that the material has good cycling performance.