Abstract
A chemical process was developed to prepare N-doped micro-nano carbon spheres with multi-scale pore structures via carbonization of N-PF/PMMA interpenetrating polymer networks, which contain melamine resin as the nitrogen source, PF as the carbon source, and polymethylmethacrylate (PMMA) as the pore-former. The N-content of N-doped micro-nano carbon spheres was controlled by adjusting the mass ratio of melamine and phenol before polymerization. The N-doped micro-nano carbon spheres as electrode materials possess appropriate pore size distribution, higher specific surface area (559 m(2) g(-1)) and consistently dispersed nitrogen atoms with adjustable doping content. These distinct characteristics endow the prospective electrode materials with excellent performance in electrochemical capacitors. In particular, N-CS-IPN-4 exhibits the highest specific capacitance of 364 F g(-1) at 0.5 A g(-1) in 6 M KOH aqueous electrolyte in a three-electrode system. It also possesses superior rate capability (57.7% retention at current densities ranging from 0.5 to 50 A g(-1)) and excellent cycling performance at 2 A g(-1) (100% retention after 10 000 cycles). All these results confirm that the N-doped micro-nano carbon spheres are promising electrochemical capacitor materials, which possesses the advantages of simple preparation procedure, multi-scale pore structures, higher specific surface areas, easy adjustment of N-content and excellent electrochemical properties.