Preparation Of Liquefied Larch-based Porous Carbon Spheres By Spray Pyrolysis And Their Electrochemical Properties

Due to its high specific surface area,large pore volume,developed pore structure,good electrical conductivity and chemical stability,porous spherical carbon has a good application prospect in the field of electrochemistry.In this paper,the main afforestation species of larch in northeast China was used as raw material,and the macromolecules in larch were converted into small molecular substances by phenol as liquefaction agent.In turn,the larch-based carbon spheres were fabricated by resinification and spray pyrolysis.The effects of solution concentration,pyrolysis temperature,soft template F127 and metal salts of Na2WO4 and Na2MoO4 on the morphology and pore structure of the carbon spheres were studied.The structural characteristics and electrochemical properties of the prepared porous carbon spheres were analyzed.The following is the main work of this paper:Using larch powder as raw material,larch liquefaction was obtained by phenol liquefaction technology,then larch-based resin obtained by reaction with formaldehyde was used as carbon precursor,and larch-based carbon spheres(CSs)were prepared by spray pyrolysis.The effects of different pyrolysis temperatures and solution concentrations on the particle size,specific surface area,pore structure and electrochemical properties of carbon spheres were investigated.The results show that the prepared carbon spheres are amorphous and regular spherical structures.The specific surface area of the carbon spheres prepared at 900℃ and 1%concentration is as high as 626.6 m2/g,and the pore volume is 0.34 cm3/g.In the 6 M KOH electrolyte,the specific capacitance is 309 F/g at a current density of 0.2 A/g,and the specific capacitance is 56%when the current density is increased to 5 A/g,showing excellent rate capability.Using larch-based resin as carbon precursor and triblock copolymer F127 as soft template,carbon spheres(PCSs)with multi-order pore structure were prepared by spray pyrolysis.The morphology and pore structure of PCSs were regulated by adjusting the ratio of F127 to carbon precursor.The results show that with the increase of F127,the surface morphology of PCSs gradually becomes rough and concave,and the particle sizes tend to be uniform.When the ratio reaches 0.075,the sample PCSs-0.075 has a specific surface area of 760.3 m2/g and a pore volume of 0.59 cm3/g.The pore structure consists of micropores,mesopores and macropores.Due to the high specific surface area and the developed multi-stage pore structure,the PCSs-0.075 has a specific capacitance of 338.8 F/g at a current density of 0.2 A/g and a capacitance retention of 48.7%at a current density of 5 A/g,showing good rate capability.Porous carbon spheres(PCSs)were prepared by spray pyrolysis using larch-based resin as carbon precursor and metal salt Na2WO4 as catalyst.The results show that the morphology of the material gradually forms a porous carbon sphere with a regular spherical structure with the addition of Na2WO4.At the same time,the specific surface area and pore volume of the carbon spheres increased gradually.When the addition ratio is 4,the specific surface area of the sample PCSs-4 reaches 528.5 m2/g,the pore volume reaches 0.42 cm3/g,and the Smicro/SBET is only 39.8%,indicating that the addition of Na2WO4 can increase the mesoporous content of the material.Through constant current charge and discharge test,the specific capacitance of sample PCSs-4 can reach 209.8 F/g when the current density is 0.2 A/g.When the current density increases to 5 A/g,the specific capacitance can still reach 139.7 F/g,which is 66.6%when at a current density of 0.2 A/g,showing good rate capability.The hollow porous carbon spheres(HPCSs)was prepared by spray pyrolysis using larch-based resin as carbon precursor,F127 as soft template,Na2MoO4 as porogen and catalyst.The effects of different contents of Na2MoO4 on the spherical morphology and pore structure of carbon spheres were studied.The results show that the specific surface area and pore volume of the material have been significantly improved with the addition of Na2MoO4.When the addition ratio reached 4,the specific surface area of the sample HPCSs-4 was as high as 1062.5 m2/g,the pore volume was 0.87 cm3/g,and the Smicro/SBET was only 31.1%,indicating that the addition of Na2MoO4 promoted the formation of mesoporous structure.At the same time,the material shows good electrochemical performance.When the current density is 0.2 A/g,the specific capacitance is 253.7 F/g.When the current density increased to 5 A/g,the specific capacitance is 226.6 F/g,and the capacitance retention rate is as high.89.3%.