Porous Carbon Spheres Derived From Melamine And Phenolic Resin And Their Capacitance Deionization Performance

Capacitive deionization(CDI)is a method that can efficiently remove charged ions from brackish water.Porous carbon has high specific surface area,good pore size distribution and electrical conductivity,and is widely used to manufacture of CDI electrodes.The structure of porous carbon is the key to determine the adsorption capacity,desalination rate,and energy consumption of CDI.In this thesis,melamine-formaldehyde resin(MF)spheres were used as template and a series of porous carbon spheres were prepared by coating and modifying them,and the relationship between the preparation conditions and its structure,and desalting performance was studied.The main research contents are listed as follows:1.In this chapter,carbon microspheres with core-shell structure were derived from a polymer precusor that were prepared by solvothermal synthesis method with MF as a template.The shell thickness of the polymer microspheres was controlled by adjusting the molar concentration of urea and citric acid in the solvent.After optimization,MF@0.2CSs has the largest specific surface area of 2667.44 m~2/g and abundant of mesopores and micropores of 2-6 nm.Thus,their specific capacitance was 203.83 F/g in the Na Cl solution of 1.0 M and their maxium salt adsorption capacity(SAC)was 19.8 mg/g when Na Cl concentration was 1000 mg/L.After 17cycles of CDI adsorption-desorption,the SAC of MF@0.2CSs electrode showed no significant attenuation,indicating their stable deionization performance.2.In this chapter,melamine/phenolic core-shell microspheres were prepared in a water-ethanol system with MF as a template,resorcinol formaldehyde resin as carbon precursor,and cetyltrimethylammonium bromide as the surfactant.After calcination and activation,the high specific surface area of the hollow carbon spheres(MF@RF-1-2)was 2141.84 m~2/g.The specific capacitance of MF@RF-1-2 in 1.0 M Na Cl solution reached 169.56 F/g.Additionally,their SACs reached 13.20 mg/g and23.00 mg/g in the Na Cl solutions with the initial concentrations of 100 mg/L and 500mg/L,respectively.After 14 cycles,their SAC does not show an obvious reduction,which indicates that the sample has a good stability as the electrode material in CDI.3.To further analyze the influence of the morphology of the MF template on the morphology and pore size distribution of prepared carbon spheres,this chapter firstly synthesized MF spheres with the particle sizes from 1.8?m to 700 nm using F127 as the morphology regulator.Then,hierarchical porous hollow carbon spheres were prepared by using these MF spheres as the template,phenolic resin as carbon precursor,and F127 as a surfactant.NHCSs-0.3 exhibits the best electrochemical properties of 176.72 F/g in 1.0 M Na Cl solution,the largest specific surface area of2395.60 m~2/g and hierarchical porous structure.Their SAC could reach as high as11.76 mg/g and 25.20 mg/g in the acqueous Na Cl of 100 and 500 mg/L,respectively.A satble performance could be observed after 15 adsorption-desorption cycles.