Nitrogen-doped activated carbons derived from a co-polymer for high supercapacitor performance

Abstract

Nitrogen-doped activated carbons (N-ACs) with controlled nitrogen doping and analogous microporous structures were prepared by pyrolysis of poly[(pyrrole-2,5-diyl)-co-(benzylidene)] (PPCB). The obtained N-ACs were thoroughly characterized using HRTEM, FESEM, BET, FTIR and XPS for their morphology, surface area and chemical composition. The N-ACs were further used to fabricate supercapacitors, and their comprehensive electrochemical properties, such as cyclic voltammograms, galvanostatic charge–discharge, electrochemical impedance spectrum, electrochemical capacitive performance, power density and long cyclic stability, were studied. The galvanostatic charge–discharge (GC) measurements on N-ACs produced at 700 °C and 800 °C show a high specific capacitance (up to 525.5 F g⁻¹ and an energy density of ca. 262.7 W h kg⁻¹ at 0.26 A g⁻¹) in alkaline media (2 M KOH). More importantly, the capacitance remains practically identical when the scan rate was increased from 0.26 to 26.31 A g⁻¹. The observed capacitance retention (∼99.5%) of N-ACs is remarkably stable for electrodes even after 4000 cycles, due to the presence of nitrogen at the surface and in the graphitic edge planes. The nitrogen content plays a significant role in producing micropore dominated ACs and in facilitating the transfer of ions through pores on the surface. The precursor (PPCB) used is cheap and can easily be prepared, making it promising for the large-scale production of N-ACs as excellent electrode materials for supercapacitors.