Mesoporous size controllable carbon microspheres and their electrochemical performances for supercapacitor electrodes

Abstract

In this paper, size controllable SiO₂ nanoparticles synthesized by adjusting the hydrolysis–condensation time and the concentration of tetraethyl orthosilicate (TEOS) in ethanol–water solution in the presence of ammonia as a catalyst were encapsulated within resorcinol–formaldehyde polymer microspheres which were fabricated in the same ethanol–water–ammonia system. After carbonization and following etching with NaOH solution, a series of mesoporous carbon microspheres (MCMs) with an average diameter of 500 nm, a mesopore size of 3.2–14 nm and surface areas of 659–872 m² g⁻¹ are obtained. As electrode materials for supercapacitors, typical samples of MCMs with a mesopore size of 3.2 nm and 13.5 nm show an initial specific capacitance of 289 and 268 F g⁻¹ under a current density of 1.0 A g⁻¹. After 10 000 charge–discharge cycles, the specific capacity remains 261 and 254 F g⁻¹ with the retention of 90.3% and 94.7%. Besides, electrochemical performances influenced by the mesopore size were investigated.