Facile synthesis of hierarchical mesopore-rich activated carbon with excellent capacitive performance

Mesoporous carbons attract increasing attention owing to their potential applications in supercapacitors. So far, controlled synthesis of mesoporous carbons with a narrow pore size distribution relies largely on the complicated template methods. To avoid the use of templates, a surfactant-free emulsion polymerization method is presented for the fabrication of a melamine-modified phenolic resin microrod (MPRR) assembled by micron-sized spherical cells and thin walls. In addition, one-step KOH activation strategy is adopted to synthesize hierarchical mesoporous activated carbon with 2-10 nm narrow mesopores by using MPRR as carbon precursors. The as-prepared mesoporous activated carbon has a high specific surface area of about 2758 m² g^-1 and a mesopore volume of 0.54 cm³ g^-1 (calculated by density functional theory), comprising ∼43.5% of total pore volume (∼1.43 cm³ g^-1). Hierarchical mesopores can significantly accelerate ion transfer and increase micropore accessibility, which endow the carbon with high specific capacitance equal to 409 F g^-1 at 0.1 A g^-1 and 268 F g^-1 at 100 A g^-1 in 6 M KOH electrolyte, with a high capacitance retention of 66%. Moreover, the assembled symmetric supercapacitor also exhibits good cycling stability in KOH electrolyte and delivers high power density equal to 12080 W kg^-1 when energy density is 5.02 Wh kg^-1. This finding provides an insight into directional tailoring of mesoporous structures of phenolic resin-based carbon materials at the molecular level for high-performance supercapacitors.