Preparation Of Activated Carbon Electrode Material Based On Anaerobic Digester Residues And Research For Its Electrochemical Properties

As a new type of energy storage component between traditional dielectric capacitors and batteries,supercapacitors have attracted widely attention due to their high power density,long cycle life,fast charge/discharge and environmental friendliness.They have broad applications prospects and huge economic value in the energy field.The performance of a supercapacitor depends primarily on its electrode materials.Carbon materials are widely used in supercapacitor electrode materials because of their low cost,high specific surface area,simple preparation process,easy adjustment of microstructure,various forms,good electrical conductivity and electrochemical stability.Recyclable waste biomass with low cost,abundant raw materials and green recycling is a preferred choice for the preparation of carbon materials.In this paper,activated carbons are successfully prepared by chemical activation and N-doping with biomass biogas residue as carbon source.The structure and morphology of the obtained materials were characterized,and the electrochemical properties of the materials as supercapacitor electrodes were investigated.The main conclusions are as follows:?1?The anaerobic digester residue based activated carbon is prepared by pre-carbonization+KOH activation and the materials which have a graded pore structure and a high specific surface area are prepared by adjusting the activation temperature and the alkali carbon ratio.The results show that the activated carbon obtained after activation increases with the increase of activation temperature and the ratio of alkali carbon,and the specific surface area increases first and then decreases.The micropore is gradually transitioning to the middle pore.When the alkali carbon ratio is 3 and the activation temperature is 600°C,the activated carbon prepared is the best.Under this condition,the anaerobic digester residues based activated carbon has the largest specific surface area,up to 942 m²g^-1and pore capacity is 0.712 cm³ g^-1,and has an ideal multilevel pore carbon structure.When the current density is 1 A g^-11 in the 6 M KOH electrolyte,the specific capacitance is 198.42 F g^-1,and the specific capacitance of 158.48 F g^-1can be maintained even when the current density reaches 10 A g^-1,and the electrochemical performance is excellent.In addition,ADR-600-3 also exhibits good electrochemical cycle stability in alkaline electrolyte.After 5000 constant current charge/discharge cycles at current density of 10 A g^-1,the specific capacitance retention is 94.67%.?2?For the activated carbon with high specific surface area and excellent electrochemical performance,the doping of N element is carried out.The effects of different doping ratios on the morphology,specific surface area,pore size distribution and capacitance characteristics of activated carbon are studied.Nitrogen doping with melamine as a nitrogen-doping agent not only does not destroy the microstructure of the soybean meal activated carbon,but also introduces nitrogen-containing functional groups to increases the electrical conductivity and the wettability of the activated carbon and introduces pseudo-capacitance,and the internal resistance of the electrode material is lowered.When the doping ratio is 0.3:1,under this condition,the anaerobic digester residues based activated carbon has the largest specific surface area,up to 1506 m² g^-11 and pore capacity 0.825 cm³ g^-1,and the obtained N-doped activated carbon in a 6 M KOH electrolyte has a specific capacitance of 248.85 F g^-11 at a current density of 1 A g^-1,which is better than the sample NADR-0.The capacitance is increased by 25.42%.And after 5000 cycles of charge and discharge,the specific capacitance retention rate is also improved to 96.01%.