Preparation And Electrochemical Application Of Heteroatom-doped Porous Carbon Materials

Supercapacitor is a kind of energy storage devices between conventional batteries and capacitors.Due to the higher power density than traditional battery and higher energy density than capacitor（10¹00 times）,supercapacitor has attracted great interests of researchers.Importantly,electrode materials have a great effect for supercapacitor to obtain the good cycle stability,high power density and energy density.Due to the good conductivity,stability and low cost,carbon materials have become the focus in electrochemical fields.The porosity and heteroatom doping of carbon materials were the main factors to affect the electrochemical properties.Porous structures can provide the channels to delivery electrolyte ions fast;Heteroatoms can enhance the wettability of electrode materials and provide pseudocapacitors.Therefore,it is benefitial for preparing the high specific capacitors by rational design the pore structures and heteroatom contents of carbon materials for application in the supercapacitors.In this paper we designed and synthesized the heteroatom doped porous carbon materials as the electrodes of supercapacitors by screening carbon precursors,heteroatom doping agent and pore forming agent,optimizing the conditions of carbonization,and further expand the applications of heteroatom doped porous carbon materials in oxygen reduction reaction（ORR）.The main works are as follows:（1）The heteroatom doped porous carbon materials were prepared via carbonizing the precursor of ionic liquids（ILs）doped alkali metal organic salt.The alkaline metal organic salts（sodium glutamate,sodium tartrate and sodium citrate）serve as the carbon source and the ILs（1-butyl-3-methylimidazolium chloride salt and 3-butyl-4-methyl thiazole bromide salt）serve as the heteroatom dopant.Due to the molecular structure of ILs are designable,different kinds of heteroatom doped porous carbon materials can be obtained.The interaction of anions and cations between ILs and alkaline metal organic salts may inhibit the decomposition of ILs during carbonization,which can increase the carbon yield in a certain extent.In addition,the porosity and heteroatom content of the carbon materials can be tuned by adjusting the feed ratio of ILs.The electrode of supercapacitor prepared by carbon materials exhibited high charge storage capacity with a specific capacitance of 287 F g^-1 and good stability in 6 M KOH at a current density of 1 A g^-1 for supercapacitors.（2）This work reports a facile strategy for the preparation ofNitrogen-doped porous carbons via carbonization of a mixture containing ferric citrate（FC）and ammonium chloride（NH₄Cl）.FC provides carbon and iron element sources,while ammonium chloride acts as both the porogen and nitrogen dopant during the carbonization process.Fe₃C nanoparticles formed in the process of carbonization can be covered in the carbon layer and provide the electrochemical activity.The formed hierarchical porous structures and nitrogen-doping may contribute to both oxygen reduction reaction（ORR）and supercapacitor applications.Compared with KOH and NaCl,the carbon prepared by NH₄Cl shows the best ORR performance in this work,which might due to the dual functions of NH₄Cl.When used for supercapacitor,the electrode prepared by carbon material shows good electrochemical performance.