Synthesis of multiple heteroatom–doped mesoporous carbon/silica composites for supercapacitors

Abstract

In this study we synthesized a series of tunable multiple heteroatom–doped mesoporous carbon/silica composites directly through a facile tricomponent co-assembly approach using a triazine–formaldehyde phenolic resol (N-resol) as the C and N atom source, tetraethyl orthosilicate (TEOS) as the Si atom source, and the diblock copolymer poly(ethylene oxide–b–ε-caprolactone) (EC) as the structure-directing template. Small-angle X-ray scattering and transmission electron microscopy revealed that mesophase transformations of the N-resol/EC/TEOS hybrids, from double-gyroid to cylinder to lamellar structures, occurred upon increasing the TEOS content (i.e., double-gyroid at 60/40/0 and 60/40/5; cylinder at 60/40/10; lamellar at 60/40/20 and 60/40/30; short-range-order structure at 60/40/50). After removing the EC template by heating sequentially at 400 and 700 °C, the resultant multiple heteroatom–doped mesoporous carbon/silica composites had high N atom (up to 13.0 wt%), O atom (up to 21.5 wt%), and Si atom (up to 6.8 wt%) contents and double-gyroid, cylinder, and wormlike mesostructures. These multiple heteroatom–doped mesoporous carbon/silica composites had exceptionally high supercapacitor efficiencies, with excellent electrochemical specific capacitances (up to 827 F g−1 at a current density of 0.5 A g−1) and very high stabilities (up to 96.64% at a current density of 10 A g−1 for up to 10 000 cycles). Such mesoporous carbon/silica composites would appear to have tremendous potential for use as high-performance supercapacitors in energy storage applications.