Facile and low-cost heteroatom-doped activated biocarbons derived from fir bark for electrochemical capacitors

Chinese fir bark was selected as a precursor, and a chemical activation method was used to prepare high surface area activated biocarbon materials with heteroatom doping. The impacts of the activation temperature on pore structure and chemical characteristics were studied. Activated biocarbon electrodes with heteroatoms of N (1.00–1.60%) and O (3.60–12.87%) were then fabricated for electrochemical performance analysis, and the relationships among the pore structure, chemical characters and specific capacitance were discussed. The results show that the specific capacitance of activated carbon electrodes from both the cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests obviously increased with increasing activation temperature in the range of 500 °C to 700 °C. The electrode fabricated with the activated carbon prepared at 700 °C exhibited the highest specific capacitance of 320 F/g at a scan rate of 2 mV/S by CV test and 342 F/g at a current density of 0.5 A/g by GCD test, which is comparable to or higher than that of most carbon-based capacitors. The favorable electrochemical performance may be attributed to the synergistic effect of the hierarchically suitable porous structure and dual doping of nitrogen and oxygen heteroatoms.