A novel path towards synthesis of nitrogen-rich porous carbon nanofibers for high performance supercapacitors

A facile and efficient nitrogen doping strategy is proposed to improve the nitrogen content, increase surface area, and tune the configuration of nitrogen-related defects in the carbon nanostructures for application as super capacitors. To this end, carbon nanofibers (CNFs) were fabricated via pyrolysis of polyacrylonitrile (PAN) nanofibers with sacrificial polymers (PMMA). By lowering the interfacial tension between PAN and PMMA in DMF with the aid of surfactants, the size of the sacrificial PMMA islands in the continuous PAN phase was significantly reduced, promoting the formation of pores and increase the specific surface area (SSA) of the host CNF during pyrolysis. The synthesis of N-doped CNF with a controlled N-bonding structure was achieved by pyrolysis of precursor on Ni surface in the presence of melamine as a nitrogen source. We showed that the concentration and configuration of N-related defects in CNFs can be respectively enhanced and controlled by absorption of the oxygen-containing sites onto a metallic substrate. Furthermore, the surface area was also increased by absorbing oxygen on the Ni surface. The synthesized porous nitrogen-rich CNFs as a binder-free and free-standing electrode for supercapacitors demonstrated remarkable electrochemical capacitance, superb rate capability, and possessed excellent long-term stability over 10,000 cycles (capacitance retention of 94%).