Preparation Of Biomass-derived Porous Carbon Based On Hydrodynamic Cavitation And Its Performance In Supercapacitor

Supercapacitor(SC),a new type of energy storage device,have been widely concerned,researched and applied in the past few decades due to their excellent power density,good rate performance,long-term cycling stability and safety.Key issues such as high production cost,underdeveloped pore structure,low specific surface area,and cycling stability are studied in this paper.In this paper,garlic peel was used as the precursor material and treated by different methods to explore the influence of the pore structure and electrochemical performance of porous biochar under different preparation conditions.In addition,the porous carbon was doped with heteroatom by using melamine as nitrogen source and different pretreatment methods to obtain high-performance nitrogen-doped porous biochar carbon(PBC),which provides a valuable reference for the research of porous biochar carbon in accordance with.By using garlic peel as the precursor and KOH as the activator,the method of hydrodynamic cavitation(HC)-assisted synthesis of PBC was verified.By comparing the effects of different preparation methods on the pore structure,surface properties,graphitization degree of PBC,and the electrochemical properties of the prepared SC,it was found that HC combined with alkali activation had a great influence on the specific surface area and pore volume of garlic skin-based PBC,the specific surface area of PBC under the optimal preparation conditions reached 3071 cm3 g-1.The total pore volume reaches 2.7 cm3g-1,it proves that the HC process has obvious results on the modification of PBC,and the surface impurities of the samples treated with HC are removed,which proves that HC is an excellent pretreatment method.Moreover,the electrochemical properties of the samples treated with HC are significantly improved.Among them,the "KOH(1:8)+HC" sample has the best effect.At a current density of 1 A g-1,the specific capacitance reaches a maximum of 240 F g-1.After 5000 charge-discharge cycles at a current density of 5 A g-1,the capacitance retention rate of "KOH(1:8)+HC" is as high as 96%,indicating its good cycling characteristics.Taking garlic peel as precursor,KOH as activator,melamine as nitrogen source,and HC as auxiliary treatment.The properties of the PBCs were distinguished,and electrochemical tests were performed on the as-prepared SC.The pore volume of the sample treated with HC combined with nitrogen doping increased by 12%(from 0.48 cm3 g-1 to 0.6 cm3 g-1)compared with the sample without HC treatment but with the same nitrogen doping.The specific surface area of micropores increased by 20.1%(from 1207 m2 g-1 to 1450 m2 g-1),and the microporosity increased from 30%to 42%.The introduction of melamine increased the microporosity and microporosity by HC treatment.The volume and specific surface area of micropores proved that HC combined with melamine had a great influence on the amount of micropores of PBC.Under the two-electrode system(6 M KOH),the specific capacitance of the SC of the "KOH(1:6)+HC+C3H6N6" sample at a current density of 1 A g-1 is 305 F g-1,which has the highest specific capacitance,as well as the highest energy density and excellent pore structure.After 5000 charge-discharge cycles(with a current density of 5 A g-1),the capacitance retention rate of the "KOH(1:6)+HC+C3H6N6" sample SC was as high as 100%,showing extremely excellent cycling characteristics.