Enhanced capacitance characteristic of microporous carbon spheres through surface modification by oxygen-containing groups

Abstract The synthesis of porous carbon spheres with good dispersity and oxygen-rich content from phenolic resin remains challenging due to weak interactions between carbon precursors and soft templates, as well as fast cross-linking rate of precursors. Herein, we demonstrate a facile and efficient organic-organic self-assembly hydrothermal method to prepare microporous carbon spheres (MCSs) with perfect dispersity and rich oxygen-containing groups under highly acidic conditions. Both the precursors and templates are partly protonated by high concentration acid and thus provide an additional Coulombic interactions between resol and F108 via the I+X−S+ mechanism. Such enhanced interaction improve the self-assembly ability of resol and F108, lead to more matching the cross-linking rate of resol, which efficient avoid macroscopic phase separation and aggregate. Results indicate that the MCSs are modified with a considerable number of oxygen-containing functional groups (hydroxyl and carbonyl) under acidic conditions, and the oxygen content increases with the concentration of HCl. The optimal MCSs with a high specific surface area of 1449 m2 g−1, large pore volume of 0.77 cm3 g−1 and high oxygen content of 8.5 at%, exhibits an enhanced specific capacitance of 361 F g−1 and excellent long-term stability (93.8% retention after 10 000 cycles) when used as the electrode materials for supercapacitors. Furthermore, the MCSs based symmetrical supercapacitors delivers a maximum energy density of 18.5 W h kg−1 at power density of 750 W kg−1. This feasible hydrothermal method develops a new strategy for the fabrication of functionalized porous carbon spheres.