Preparation Of Resorcinol-formaldehyde Resin-based Microporous Carbon Spheres And Their Performance In CO₂ Sorption And Supercapacitors

Microporous carbon materials have shown excellent application prospects in the fields of CO₂ adsorption and supercapacitors.In this thesis,monodispersed phenolic resin spheres are synthesized by the modified St?ber method,and microporous carbon spheres with well-developed micropores and uniform pore size distributions are further prepared by an"in-situ single metal ion activation"method.The prepared microporous carbon spheres are applied to the fields of CO₂ adsorption and supercapacitors.The specific research contents are as follows:1.The phenolic?RF?resinspheres are synthesized by using resorcinol and formaldehyde as raw materials according to St?ber method.Then KOH is used as activator to obtain potassium salts of RF resins by acid-base reaction between-OH groups in RF resins and KOH.The salts are directly carbonized at 700°C to prepare microporous carbon spheres with well-developed micropores and uniform pore size distributions.The results show that monodispersed potassium ions produce an"in situ single metal ion activation"effect in the polymer sphere,which promotes the carbon spheres to have a uniform distribution of developed ultramicropores and maintain good sphere morphology.Theoretically,when-OH is completely converted to-OK group?CS-1 sample?,the activation efficiency is the highest,thus the CS-1 sample has the largest specific surface area(1235 cm² g^-1),micropore specific surface area(1084 cm² g^-1),micropore volume(0.57 cm³ g^-1)and the best CO₂ adsorption performance(7.34 mmol g^-1 and4.83 mmol g^-11 at 0°C and 25°C respectively).The excellent CO₂ adsorption performance of the material is attributed to the developed ultramicroporosity and the uniform distribution of micropore pore size.2.The effect of N doping on the CO₂ adsorption performance of carbon materialsis is one of the debate problem in the field of CO₂ sorption.M-aminophenol formaldehyde?AF?resin spheres are synthesised by the modified St?ber method with m-aminophenol used as N source.N-free and N-doped microporous carbon spheres with similar morphology and uniform pore size distribution are successfully prepared by the method of"in-situ single metal ion activation."The unique pore structure and chemical properties of the microporous carbon spheres is the key for elucidating the role of micropore size and N doping in CO₂ adsorption.By fitting the CO₂ adsorption amounts at different temperatures of the samples with the same average micropore size to the micropore volume and the N content,we find that the CO₂adsorption capacities mainly depends on the micropore volume,and is independent of the N content.The CO₂ adsorption capacitiesof per unit pore volume and the selectivity of CO₂/N₂ are fitted to the micropore pore size and the N content,respectively,and it is found that the CO₂adsorption capacities are related to the micropore pore size,but not related to the N content.The selectivity of CO₂/N₂ is related to both the factors,but the contribution of the micropore size is greater.Compared with the previous research,we realize the single factor study by strictly control the variables,and the conclusion is obtained based on a large amount of experimental data,so it is very reliable.3.The capacitive properties of the prepared microporous carbon spheres with uniform micropore size distribution are studied in KOH electrolyte.The carbon spheres exhibit excellent capacitive performance.Among them,the sample of C-CS-900 has the highest specific capacitance value(258.4 F g^-1 and 128 F g^-1 at 0.1 A g^-1 and 20 A g^-11 respectively).By comparing the specific capacitance per unit area of the sample,we find that the N doping enhances the specific capacitance of the carbon materials.