Quantitative Control of Pore Size of Mesoporous Carbon Nanospheres through the Self-Assembly of Diblock Copolymer Micelles in Solution.

Abstract

This paper reports facile synthesis of nitrogen-doped mesoporous carbon nanospheres (MCNSs) with average diameters of around 300 nm and well-controlled pore sizes ranging from 8 to 38 nm, by employing polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblocks with different PS block lengths as the soft templates and dopamine as the carbon-rich precursor. For the first time, a linear equation is achieved for the quantitative control of the average pore size of MCNSs by simply adjusting a block length of diblock copolymer. The resultant MCNSs possess high surface areas of up to 450 m(2) g(-1) and nitrogen doping contents of up to ≈3 wt%. As electrode materials of supercapacitors, the MCNSs exhibit excellent electrochemical performance with high specific capacitances of up to 350 F g(-1) at 0.1 A g(-1) , superior rate capability, and cycling stability. Interestingly, the specific capacitance of the MCNSs reduces linearly with increasing pore size, whereas the normalized capacitance by specific surface area remains invariable. This represents a new spectrum of the relationship between electrochemical capacitance and pore size (>5 nm) for porous carbons, which makes a complement to the existing spectra focusing on pore diameters of <5 nm.