Silkworm Excrement Derived Carbon Material And Its Capacitance Properties

Natural biomass silkworm sand is a renewable carbon source material.In this paper,the capacitance characteristics of silkworm sand carbon materials prepared in different process conditions for supercapacitors are studied.The main contents are as follows:(1)Preparation of silkworm sand carbon: The biomass raw material silkworm sand is carbonized in an inert atmosphere,and then activated with potassium hydroxide to prepare a supercapacitor electrode material.The effects of different process conditions such as carbonization temperature,carbonization time,activation temperature,activation time,alkali-carbon ratio,and inert gas shielding gas on the surface structure and physical properties of silkworm sand carbon materials were investigated.Thermogravimetric analysis,XRD,XPS,BET,SEM,TEM and other methods were used to analyze the surface structure and properties of silkworm carbon material.(2)Capacitance characteristics study: Using the prepared silkworm sand carbon material as a supercapacitor electrode material,the three-electrode system was used to test the silkworm sand carbon in 1mol/L Li2SO4,1 mol/L Na2SO4,and 6mol/L KOH electrolyte.The effects of the cyclic voltammetry,DC charge and discharge,and AC impedance of the material electrodes on the electrochemical performance have established the best process conditions for preparing silkworm sand carbon materials.Thermogravimetric analysis research shows that the carbonization process of the silkworm biomass,a biomass raw material,mainly includes four stages: free water evaporation,combined with water precipitation,pyrolysis,and slow weightlessness.A phase change occurs between 370?and 500?.At this stage,cellulose and lignin undergo thermal decomposition,and C-O,C-C bonds are broken.Starting at 600? and slowly losing weight at 900?,the total weight loss rate of silkworm sand was 90%.XRD analysis of silkworm sand with different carbonization temperatures showed that: as the temperature increased,the peak intensity of silkworm sand carbon material increased,and the peak width gradually narrowed,indicating that the size and number of graphite crystallites in silkworm sand carbon material changed with The increase of carbonization temperature showed an increasing trend.Raman analysis shows that carbonized silkworm sand material has a lot of C atom defects,and the activated carbonized silkworm sand material has been treated.The analysis shows that the C atomic crystal has fewer defects and a high degree of graphitization.Scanning electron microscopy analysis showed that the particle size of silkworm sand carbon material after carbonization and activation treatment was on average between 1-2 ?m,and the particle size of silkworm sand carbon material after activation was thinner and the layers were clearer.Transmission electron microscopy analysis shows that the carbonized carbon material has obvious impurities,while the activated silkworm carbon material has increased pore size and enhanced graphitization.The analysis of specific surface area showed that the specific surface area of the activated silkworm sand carbon material increased greatly,up to 2958.2 cm2/g,and its pore diameter decreased due to the increase of specific surface area.The optimal process conditions are carbonization temperature 600 ?,carbonization time 2h,alkali-carbon ratio 4:1,activation time 2h,and activation temperature 700?.The silkworm sand carbon material obtained in different protective atmospheres is in 1mol/L Li2SO4 electrolyte The specific capacities are: 577.9 F/g under nitrogen protection,517.5 F/g under argon protection,and 464.1 F/g under hydrogen-argon mixed gas(5% hydrogen).The cyclic voltammetry curve is rectangular-like,indicating that it is an electric double layer capacitor,has a certain symmetry,and has no redox peak.The silkworm electrode material prepared under the optimal process conditions has a very low impedance and a standard oblique line at about 45° in the high frequency region,which indicates that the silkworm carbon material has a rich pore structure,which increases the ion passing rate and reduces its internal resistance.The silkworm sand electrode material prepared under the optimal process conditions has good cycle stability,and the capacity efficiency is maintained at 71.4% when it is circulated for 12000 cycles in a 6mol/L KOH electrolyte.