Simultaneous polymerization enabled the facile fabrication of S-doped carbons with tunable mesoporosity for high-capacitance supercapacitors

Abstract

A cationic polymerization of 2-thiophenemethanol (ThM) and a sol–gel polycondensation of tetraethylorthosilicate (TEOS) were simultaneously catalyzed by trifluoroacetic acid in a single process step to produce poly(2-thiophenemethanol)/silica (PThM/SiO₂) composites. S-Doped mesoporous carbon (S-MC) materials were then achieved by high-temperature carbonization of PThM/SiO₂ under an inert atmosphere and subsequent etching off SiO₂ in hydrofluoric acid. This in situ crafting process allows us to tailor the porosity of S-MC in the range of 6 to 30 nm. The specific surface area (278–650 m² g⁻¹) and pore volume (0.15–0.67 cm³ g⁻¹) increase with increasing the feed ratio of TEOS to ThM. Both the specific surface area and pore volume of S-MC are also higher than those of the un-doped mesoporous carbon (MC) materials using furfuryl alcohol as the starting monomer. The S-MC electrodes thus show larger specific capacitance (C_s) values (252 F g⁻¹ at 25 mV s⁻¹ and 125 F g⁻¹ at 0.5 A g⁻¹) compared to the un-doped MC electrode (203 F g⁻¹ at 25 mV s⁻¹ and 110 F g⁻¹ at 0.5 A g⁻¹). The retention of initial C_s for S-MC is 66%, higher than 53% for MC after a 20-fold increase in the scan rate. After 1000 charge/discharge cycles, the C_s retention for S-MC is 97%, also higher than that of MC (93%). As expected, the S-MC electrodes exhibit larger C_s, higher rate performance, and better cycling stability, compared to the MC counterparts and those fabricated in the absence of TEOS by identical experimental processes. Excellent performance can be contributed to the mesoporous morphology in combination with active doping of rich S heteroatoms.