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

N-doped porous carbon (NPC)/iron oxide (Fe x O y ) 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/Fe x O y , 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. Fe x O y 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 m 2 /g and 3.8 nm, respectively. NPC/Fe x O y 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/Fe x O y from the pyrolysis of coal or polyaniline, NPC/Fe x O y 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.