Preparation And Electrochemical Properties Of Heteroatom-doped Porous Carbon Materials

Supercapacitors,also known as electrochemical capacitors,are of great concern because of their long cycle life,simple principle,and high dynamic charge propagation.Carbon material is a kind of electrode material,showing the electric double layer capacitor.It is widely used in the preparation of supercapacitor electrode materialsbecause of its ideal physical and chemical properties.At the same time,carbon materials have low cost,wide range of sources,various forms and easy processing and so on.The carbon material introduces the heteroatoms?such as phosphorus,sulfur,nitrogen atoms?,so the pseudo-capacitance can be introduced in the electric double layer capacitor.Pseudostructure will work with the electric double layer capacitor to improve the electrochemical properties of the material.At the same time,the carbon material can be treated by physical activation and chemical activation,in which the effect of chemical activation is better.KOH is the most commonly used chemical activator,through the activation of the hole,the specific surface area of the material will be significantly improved,shortening the ion transport path,speed up the electron transfer,and further improve the electrochemical properties of carbon materials.The main research contents of this paper are as follows:1.Polyurethane was used as the carbon precursor and pre-carbonized at 500 ^oC and activated by the activator KOH.The morphology and structure of the samples were characterized by TEM,SEM,XRD,FTIR,XPS and nitrogen adsorption.The results of nitrogen adsorption show that the specific surface area of the sample after activation can reach 2216 m2g^-1.The electrochemical results show that when the mass ratio of KOH to polyurethane is 2:1,the activation effect is the best,and the specific capacitance of sample PUC-2:1 at 1 A g^-1 is 395 F g^-1.Moreover,the specific capacitance of PUC-2:1 is still 95.3%of the initial capacitance after 4000 cycles of charge and discharge at a current density of 10 A g^-1.The energy-power density of the sample was obtained by two-electrode testing.The energy density of the sample PUC-2:1 at the power density of 1080 W kg^-1is 24.4 Wh kg^-1.2.Nitrogen and sulfur elements was doped in glucose through hydrothermal method with glucose as the carbon precursor and thiourea as a nitrogen source and sulfur source.Then,at the high temperature of 750^oC,the activated glucose was activated by the activator KOH,and the nitrogen-sulfur co-doped glucose-based porous carbon material was successfully obtained.The electrochemical test results show that the doping effect is the best when the molar ratio of glucose to thiourea is20:1.When the mass ratio of KOH to carbon-based material is 1:1,the activation is best and the electrochemical best performance.The specific capacitance of the sample ADGC-1:1 at 1 A g^-1 current density is 281 F g^-1,and at the current density of 5 A g^-1,the specific capacitance increases about 7%than the initialcapacitance,indicating that the sample has a good cycle rate stability.3.In the methanol environment,with glacial acetic acid as the initiator and ethylenediamine on the amination of glucose,heteroatom nitrogen introduced in the glucose.Then,the material was activated by the activator KOH at a high temperature of 750 ^oC to obtain a nitrogen-doped porous carbon material.It was found that the specific surface area of the sample AGC-1:1 was up to 1106 m2g^-1,which was much higher than that of the unactivated sample 100 m2g^-1 after activation.The results of electrochemical performance test show that the mass ratio of KOH to the sample is 1:1,the best performance of the sample is obtained in all aspects.At the current density of 1 A g^-1,the sample AGC-1:1 is larger than the capacitance to 324 F g^-1,higher than the capacitance value,and at 10 A g^-1 current density,its specific capacitance value can still reach 171 F g^-1,indicating that the sample has a good rate performance.At the current density of 10 A g^-1,the specific capacitance of sample AGC-1:1 is slightly improved compared with the initial specific capacitance after 5000 cycles of charge and discharge,which indicates that the cycle stability of the sample is good.