N-, P-, and Ni-Co-doped Porous Carbon from Poplar Powder and Graphene Oxide Composites as Electrode Materials for Supercapacitors

Poplar powder was used as a raw material to prepare an electrode material in supercapacitors by doping modification, carbonization, and activation. The lignin-removed poplar powder was mixed with graphene oxide, melamine, and diammonium hydrogen phosphate and then compounded with nickel sulfate. Upon carbonization and activation with KOH, the composite becomes a hierarchical porous carbon material with a pore volume of 0.93 cm3 g-1 and a surface area of 1214.1 m2 g-1. At 0.5 A g-1 current per square meter, the specific capacitance was 407.5 F g-1. In addition, 92.6% of the capacitance remained even after 3000 charging and discharging cycles. There was an outstanding power and energy density of 12.32 W h kg-1 at 499.99 W kg-1 for a symmetric supercapacitor in 6 M KOH. Co-doped porous carbon with nitrogen, phosphorous, and nickel could be a good electrode material for energy storage devices.