The Research On The Capacitive Performance Of Lignocellulose Carbon Materials Prepared By Salt Activation

Carbon materials have good application prospects in adsorption materials,catalytic materials,electrode materials,biological carrier fields as the result of superior electroconductibility,thermal stability,high specific area and high mechanical strength,and have recently received extensive concern of many scholars from the world.At this stage,the raw materials of carbon mainly rely on the mineral resource such as oil,coal etc.With the increasing consumption of these non-renewable resource,the exploitable years of these resource is falling very sharply.Therefore,looking for an alternative renewable resource to prepare active carbon material is imminent.Biomass resources such as crop straw,forestry residues,poultry droppings,not only possess the advantages of low-cost,easily available and environment friendly,but also contain rich oxygenic functional groups such as hydroxyl or carboxyl.It plays an important role in catalytic materials,electrode materials,biological carrier fields and has received extensive attention from academic circles.In last decade,scientists have made systemic research in the matter of biomass source,preparing methods and activation mechanism of biomass carbon.They discovered that the specific surface area of biomass carbon prepared from simple carbonizing process was still low and couldn't meet the requirements of adsorption materials and electrode materials.The activating agent was always needed in the preparation process of biomass carbon.Common activator such as alkali,acid and alkaline salt will corrode industrial equipment and increase the cost of enterprise,which is always the problem of manufacturing enterprise.In order to solve this problem,we use lignocellulose as carbon source and explore the influence of NaH2PO4,ZnCl2 and its mixed solution in carbon morphology,pore structure and capacitive performance.The results show that(1)NaH2PO4 solution can increase the capacitive performance of biomass carbon by improving the degree of graphitization and wettability and conductivity in electrolyte solution.The degree of graphitization has close relationship with concentration of NaH2PO4 solution.When the concentration of NaH2PO4 solution is 200 mg/mL,the capacitive performance of biomass carbon is the most significant and it can reach to 123 F g-1 at the current density of 1 A g-1.(2)ZnCl2 solution can improve the capacitive performance of biomass carbon by increasing specific surface area(SSA),introducing the oxygen-containing functional groups and accelerating the charge transferring in porous carbon materials.The inside pore structure of biomass carbon is also closely linked to concentration of ZnCl2 solution.When the concentration of ZnCl2 solution is 100 mg/mL,the capacitive performance of biomass carbon is the most outstanding and it can reach to 141.4 F g-1 at the current density of 1 A g-1.(3)NaH2PO4-ZnCl2 solution can further optimize the capacitive performance of biomass carbon by adjusting the microporous-mesoporous proportion and forming a phosphor-doped hierarchically porous carbon structure.When the concentration of NaH2PO4 and ZnCl2 are 100 mg mL-1,the capacitive performance of biomass carbon is the most optimized and it can reach to 195.1 F g-1 at the current density of 1 A g-1.(4)We chose the optimized PZCC100 as electrodes and assembled a symmertrical supercapacitor.Our as-assembled PZCC-SSC device is able to deliver a maximum energy density of 4.7 Wh kg-1,which is apparently higher than recently reported carbon-based symmetric supercapacitors.Meanwhile,it also performs excellent electrochemical durability,which could retain more than 96.7%of its initial capacitance after 10000 cycles.