Synthesis of mesoporous carbon spheres with a hierarchical pore structure for the electrochemical double-layer capacitor

摘要

Mesoporous carbon spheres with hierarchical foam-like pore structures have been synthesized by a dual-templating strategy using phenolic resol as a carbon source, Pluronic F127 and spherical silica mesocellular foams (Si-MCFs) as the soft and hard template, respectively. The results show that the morphology and mesostructure of the silica template are faithfully replicated. The obtained mesoporous carbon material with spherical diameter size of ca. 3-5 nm exhibits hierarchical pore sizes (from ca. 3.5 to 60 nm), high specific surface area (1320 m~2/g) and large pore volume (3.5 cm~3/g). The carbon surface contains plenty of oxygen-containing groups, resulting in hydrophilic property for an electrode material. In addition, Pluronic F127 plays an important role in the synthesis for maintaining the foam-like mesostructure of the silica templates and faithful replication of the spherical morphology. The electrochemical measurements show that the hierarchically mesoporous carbon spheres as an electrochemical double-layer capacitor (EDLC) electrode present a long cyclic life, excellent rate capability, and high specific capacitance as ca. 208 F/g at 0.5 A/g in (2.0 M) H2SO4 aqueous solution. Its specific capacitance can still remain ca. 146 F/g at a high loading current density of 30 A/g with the retention of ca. 70. Furthermore, this material also exhibits excellent capacitive performance in (C2H5)4NBF4/propylene carbonate electrolyte, and its specific capacitance is 97 F/g at loading current density of 0.5 A/g.