Nitrogen-self-doped mesoporous carbons synthesized by the direct carbonization of ferric ammonium citrate for high-performance supercapacitors

Abstract

We report a simple method of synthesizing nitrogen-self-doped mesoporous carbons by the direct carbonization of ferric ammonium citrate (FAC) in an inert atmosphere. The resulting materials stacked by nanospherical particles exhibited a large the Brunauer–Emmett–Teller (BET) surface area of up to 1021 m2 g−1, bimodal porosity (pores centered at approximately 2 and 9 nm), and nitrogen self doping (3.86 %). The electrochemical properties of the nitrogen-self-doped mesoporous carbons were evaluated in 1 M H2SO4 aqueous solutions by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). Results showed that FBNC-700 (FB represents FAC brown (CAS Reg. No. 1332-98-5), N represents “nitrogen-self-doped,” C represents mesoporous-carbon materials, and 700 represents carbonization temperature), as an electrode for supercapacitors, exhibited a high specific capacitance of 225 F g−1 at a current density of 1 A g−1. This specific capacitance may be maintained at 162 F g−1 and 10 A g−1. The pair of oxidation and reduction peaks at approximately 0.4 V (quinone-type species (C = O)) was broad and extended to lower potentials (down to 0 V; N functionalities), indicating the excellent pseudocapacitive behavior of nitrogen-self-doped mesoporous carbons. The nitrogen-self-doped mesoporous carbons had good stability, with 93.92 % capacitance retention after 5000 cycles at a current density of 2 A g−1.