The Preparation Of Heteroatom-Doped Porous Carbon Materials And Their Capacitive Behaviour

Supercapacitor is a novel kind of energy storage devices, which is environmental friendly and has large energy density, high power density and long cycle life. Porous carbon materials with the advantages of large specific surface area, environmental friendly and good electronic conductivity, have already became the excellent candidates for the use as electrode materials for supercapacitors. The preparation of porous carbon electrode materials with large special capacitance, high rate capability and cycle stability is still a challenge. Numbers of studies indicated that introducing surface functional groups or heteroatoms on the surface of carbon materials appears to be an effective way of improving the electrode’s capacitance. Thus, this work studies the preparation and electrochemical performance of heteroatom-doped microporous and macroporous carbon materials. The main contents and results are as follows:(1) Nitrogen-doped microporous carbon materials with a three-dimensional network structure were prepared by directly pyrolysis of resorcinol-gelatin-formaldehyde co-polymers, in which biomacromolecules gelatin acted as nitrogen precursor. The nitrogen content of as-prepared porous carbons was tunable by just changing the ratio of gelatin to resorcinol. Since the three-dimensional network structure favored fast electron transportation, and the existence of nitrogen improved the electronic conductivity and wettability of electrode materials, the special capacitance of nitrogen-doped microporous carbons reached149F g-1, which was as twice as that of microporous carbons from resorcinol-formaldehyde resin. After activated with water, the carbon material has a high special capacitance of228F g-1, excellent rate capability and long-term cycle stability, with a specific surface area of1174m2g-1.(2) Boron and nitrogen dual doped porous carbon materials were prepared based on the synthesis of nitrogen-doped microporous carbons, using boric acid as boron precursor. The boron content was tunable by just changing the amount of boric acid. Compared with nitrogen-doped microporous carbons, boron and nitrogen co-doped carbons have better capacitive behavior and higher special capacitance (175F g-1), due to the better electronic conductivity improved by boron doped. After activated with water, the carbon material has a high special capacitance of232F g-1and excellent rate capability, with a specific surface area of1325m2g-1. (3) Nitrogen-doped macroporous carbon materials with open-cell structure and high nitrogen content were synthesized by further increasing the amounts of gelatin and catalyst. The pore structure of as-prepared macroporous carbons can be tuned by controlling the amount of gelatin and malonic acid. Although the special capacitance of nitrogen-doped macroporous carbon reached185F g-1, the cyclic voltammetry curves show a large polarization. After activated with water, the material has a high special capacitance of202F g-1and excellent capacitive behavior.