Soft-template assisted hydrothermal synthesis of size-tunable, N-doped porous carbon spheres for supercapacitor electrodes

Porous carbon spheres ranging in size from nanometer to micrometer have been attracting worldwide attention owing to their excellent performance and wide application. In this paper, nitrogen-doped porous carbon spheres (NPCSs) are successfully prepared by a facile hydrothermal strategy under the assistance of triblock copolymer F108 as soft template. The effect of the ethanol/water volume ratios, concentration of F108 and ammonia, and the alkyl chain of alcohol on the morphologies and particle size of the resulted NPCSs are investigated systematically. Results show that the particle size can be tuned from 160 to 2000 nm by adjusting the synthesis parameters. The obtained NPCSs exhibit a large specific surface area (1481 m(2) g(-1)) and suitable nitrogen-doped concentration (2.4 at%). As electrode material for supercapacitors, the NPCSs present a high specific capacitance of 365 F g(-1) at 0.5 A g(-1) and outstanding cycling stability with 93.9% retention after 10 000 cycles.