Preparation Of Biomass-derived Activated Carbon With Heteroatom-doped And Study Of Their Supercapacitors And Oxygen Reduction Reaction

With increasing global demand for environment protection and energy saving,the development of clean,sustainable and high performance energy storage devices,including supercapacitors,fuel cells and metal air batteries,has inspired numerous significant investigations.Recently,the synthesis of activated carbon materialsderived from biomass for supercapacitors has aroused wide concern.In this paper,we select pomelo peel as carbon precursor.Potassium hydroxide(KOH)acts as pore-forming and activating reagent that improves the porosity and specific surface area of biomass carbon.Melamine acts as low cost and high nitrogen content precursor.Metal,acting as process modifier during pyrolysis process improves the graphitization of carbon during pyrolysis process.Firstly,the dried PP was pyrolyzed and carbonized to obtain pomelo peel carbon(denoted as PC).PAC was activated by the chemical etching agent KOH.Meanwhile,the influences of the different temperature and the different mass ratio of KOH were studied.Then,NPAC was prepared by thermal pyrolysis of pomelo peel with KOH and melamine/glucosamine.And the influences of melamine and glucosamine on NPAC were studied.Further,the catalyst effect of metal(Fe/Co)at high temperature was investigated to enhance the capacitive property of NPAC.NPACmetai was prepared,and the property and electrochemical performance of NPACmetai was studied.Compare these four materials(PC,PAC,NPAC and NPACmetai)by physical characterization analysis and electrochemical performance evaluation,we can choose the optimal materials biomass based activated carbon material(called NPACCo).The prepared material NPACCo shows high content of quaternary-N(2.5%)and pyridinic-N(1.7%),co-existences of amorphous and short-range ordered carbon,high specific surface area(SSA,2091 m2 g-1)and favorable pore structure with majority of micropores and small mesopores(diameter<5 nm).These are favorable for improving capacitance value and oxygen reduction reaction activity.As electrode material of supercapacitors,NPACCo exhibits high specific capacitance of 325 F g-1 at 1 A g-1,which remains 83.4%at much higher current density of 20 A g-1,showing good rate capability.At ultrahigh rate of 50 A g-1,the capacitance of NPACCo remains 246 F g-1,which is 6.3,1.9 and 3.2 times as high as that of other three materials(PC,PAC and NPAC).The as-assembled symmetric supercapacitor fabricated by using NPACCo delivers high energy density of 12.5 Wh kg-1 at power density of 250 W kg-1,which still retains 7.3 Wh kg-1 at as high as 8200 W kg-1 in alkaline aqueous electrolyte,exhibiting high power density and satisfactory energy density.Because NPACCo possesses high SSA,ample pore structure and high content of quatermnary-N and pyridinic-N.Further,we discussed the oxygen reduction reaction properties.NPACCo possesses high onset potential(0.87 V),high half-wave potential(0.78 V),excellent methanol tolerance and low yield of byproduct(H202).These properties are comparable or superior to those of commercial Pt/C.The admirable supercapacitor behavior and excellent ORR performance indicate that pomelo peel-based NPACCo is a promising candidate material for electrochemical energy storage and conversion.