LAUSR

Abstract Based on a meta-organic framework (MOF) formulated as [Co4(phen)4Cl8] (phen = 1, 10-phenanthroline) as precursor, Cl/O doped C/CoO material (C/CoO-200) was synthesized by a one-step calcining method at a low temperature of 200 °C. In C/CoO-200, CoO nanoparticles with an average size of 25 nm were linked by carbon matrix into particles with the diameter of 200 nm ∼ 1 μm. The sample possessed a very low atomic percentage of CoO (CoO: 1.9%; C: 86.8%) due to the large amount of carbon from the organic ligand, phen in the precursor. However, it still exhibited a large specific capacitance of 1052 F g−1 at 0.5 A g−1 in 2 M KOH electrolyte with a 79.6% capacitance retention at 10 A g−1. After successive etched in acid, Cl/O doped carbon nanoparticles were obtained. C-300 was composed by individual nanoparticles with size of 100–500 nm, it showed a specific capacitance of 207 and 164 F g−1 in 2 M KOH at a current density of 0.5 and 1 A g−1, respectively, which was comparable to the commercial activated carbon (AC) (199 and 179 F g−1 for AC at 0.5 and 1 A g−1, respectively). An asymmetric supercapacitor based on the positive electrode of C/CoO-200 and the negative electrode of C-300 exhibited a stable performance with a 61% retention of specific capacitance after 10,000 charging-discharging cycles at 1.5 A g−1.