We demonstrate a simple and highly efficient strategy to synthesize MnO2/nitrogen-doped ultramicroporous carbon nanospheres（MnO2/N-UCNs） for supercapacitor application.MnO2/N-UCNs were fabricated via a template-free polymerization of resorcinol/formaldehyde on the surface of phloroglucinol/terephthalaldehyde colloids in the presence of hexamethylenetetramine,followed by carbonization and then a redox reaction between carbons and KMnO4.As-prepared MnO2/N-UCNs exhibits regular ultramicropores,high surface area,nitrogen heteroatom,and high content of MnO2.A typical MnO2/N-UCNs with 57 wt.%MnO2 doping content（denoted as MnO2（57%）/N-UCNs） makes the most use of the synergistic effect between carbons and metal oxides.MnO2（57%）/N-UCNs as a supercapacitor electrode exhibits excellent electrochemical performance such as a high specific capacitance（401 F/g at 1.0 A/g） and excellent charge/discharge stability（86.3%of the initial capacitance after 10,000 cycles at 2.0 A/g） in 1.0 mol/L Na2SO4 electrolyte.The well-designed and high-performance MnO2/N-UCNs highlight the great potential for advanced supercapacitor applications.

Chinese chemical letters

MnO2; Supercapacitor; Nitrogen-doping; Electrode; Ultramicroporous carbon nanosphere; MnO2; Supercapacitor; Nitrogen-doping; Electrode; Ultramicroporous carbon nanosphere