Preparation of porous carbon electrode materials from potassium hydroxide extract of lignite doped with nitrogen

Lignite is cheap, easy to obtain and rich in pores, so it was used as an electrode material for supercapacitors early. In this paper, Yimin lignite (YM) was used as raw material, and KOH was used to extract organic components. Melamine was adulterated into the extracted material for thorough mixing. The reaction mechanism and structural changes in it were explored. Experimental results and density functional theory (DFT) calculations showed that introducing nitrogen atoms into the coal-based activated carbon leads to a rearrangement of the carbon skeleton structure and changes the surface chemical environment. In this process, we adjust the porosity, specific surface area and discharge specific capacity of the produced carbon materials by changing nitrogen doping ratio, activation time and activation temperature. The excellent N-doped porous carbon material At-120 (activation time:120 min) was prepared with a high specific surface area (SBET: 3020 m2/g), abundant micropores (Vmic: 1.242 cm3/g), proper mesopores (Vmes: 0.182 cm3/g, Vmes ratio: 12.6 %), low impurity content, and high amount of N doping (6.43 wt%). These characteristics of At-120 enabled it to have a high specific capacitance value of 433.5 F/g at a current density of 1 A/g. The enhanced At-120 has 42.18 % higher specific capacitance than the undoped lignite alkali extract(LC).