Facile synthesis and capacitance properties of N-doped porous carbon/iron oxide composites through the single-step pyrolysis of coal-based polyaniline

Abstract

N-doped porous carbon (NPC)/iron oxide (FexOy) composites with rich nanoscale meso–macropores and high specific capacitances are successfully synthesized through a facile single-step pyrolysis approach, using coal-based polyaniline prepared through an in-situ polymerization method as a carbon and nitrogen source, and ferric citrate aqueous solution as a catalyst precursor. In NPC/FexOy, porous carbon mainly presents in the amorphous state. Nitrogen is successfully doped into NPC in the form of graphitic N, pyrrolic N, and pyridinic N. FexOy sphere particles with the diameter of 50–500 nm are embedded in the pores or on the surface of porous carbon. The NPC yield is about 65.4% and the nitrogen content is 0.122 wt%. The BET specific surface area and average pore width are 224.6 m2/g and 3.8 nm, respectively. NPC/FexOy composites demonstrate a high specific capacitance of 449 F/g at a current density of 1 A/g, good cycling stability, high capacitance retention of 88.2% at 5.0 A/g after 5000 cycles of charge and discharge, and good rate capability. Compared with NPC/FexOy from the pyrolysis of coal or polyaniline, NPC/FexOy from coal-based polyaniline possesses much better capacitance properties for owning a large number of evenly distributed and nanoscale meso–macropores greatly contributed by some interpenetrating network structures of coal-based polyaniline. This study will provide a facile and promising approach for the value-added applications of low-rank coal.