From Dead Pine Needles to O, N Codoped Activated Carbons by a One-Step Carbonization for High Rate Performance Supercapacitors

Dead pine needle derived O, N codoped activated carbons were prepared by an easy one-step carbonization without adding any chemical reagents. The as-obtained PN-X samples had a high rate performance as electrodes for supercapacitors. It was due to the unique structure of cells in dead pine needles, abundant contents of metal elements (K, Na, Ca, Mg) and a large number of heteroatom contents (O, N). The role of different metal atoms and air for the formation of pores, and the mechanism of one-step carbonization were proposed. Micro/Meso/Macropores are beneficial to ion adsorption and transportation, and the doping O and N can improve physical and chemical properties of the carbon surface and increase electrochemical active sites to generate additional pseudocapacitance. All chemical and physical properties of PN-X samples were provided in detail. Especially, the PN-1000 showed a high specific capacitance of 223 F g–1 (178 F cm–3) at 0.5 A g–1 while it still had 150 F g–1 (120 F cm–3) even at 100 A g–1. The results suggested the unique PN-1000 to be a promising electrode material for supercapacitors in many practical applications.