Poly(ionic liquid)-derived, N, S-codoped ultramicroporous carbon nanoparticles for supercapacitors

Abstract

We demonstrate a highly efficient strategy to synthesize N, S-codoped ultramicroporous carbon nanoparticles (N/S-UCNs) via simple polymerization and carbonization of an ionic liquid (IL). By chemical oxidative polymerization of p-phenylenediamine sulfate ([pPD][2HSO4]) using ammonium persulfate as an initiator, poly(ionic liquid) (PIL) of p[pPD][2HSO4] is obtained, and it acts not only as carbon, nitrogen and sulfur sources, but also as a self-template to generate regular ultramicropores during carbonization. As-prepared N/S-UCNs have nanoscale morphology, uniform ultramicropores (0.50–0.59nm), high surface area (505–1018m2g−1), and high doping content of heteroatoms (N and S). The N/S-UCN carbonized at 600°C (denoted as N/S-UCN600) achieves an optimum balance between specific surface area and high heteroatom doping content, which exhibits good electrochemical performance when it was used as electrode for supercapacitors. N/S-UCN600 electrode shows a high specific capacitance (225Fg−1 at 2.0Ag−1), long-term cycle stability (90.8% retention after 10,000 cycles), and excellent rate capability (160Fg−1 at 20Ag−1) in alkaline electrolyte. The present PIL-derived strategy to fabricate carbon nanoparticles can be easily carried out without any pretreatment, template or activation procedure, which highlights new opportunity to design heteroatom-doped carbons for advanced energy storage applications.