Facile wet mechanochemistry coupled K2FeO4 activation to prepare functional coal-derived hierarchical porous carbon for supercapacitors

Abstract

The high power characteristics of supercapacitors (SC) are attractive for grid scale energy storage. The core to achieve the large scale application of SC lies in the preparation of high performance electrode materials. Herein, a facile wet mechanochemistry (WMC) coupled K2FeO4 activation is used to fabricate O/N/S doped coal-derived hierarchical porous carbon (CHPC). K2FeO4 generates high-energy sputtering O2 under mechanical force to impact precursor, leading to an increase in lattice defects, and full exposure of active sites, which facilitates activation of precursor and coupling of heteroatoms. Furthermore, K2FeO4 has the pore forming ability of K-based component and the catalytic graphitization effect of Fe-based component, which could synergistically regulate pore structure and graphitization of CHPC. Experimental exploration combined with density functional theory calculation showed that the unique micro-mesopores structure of CHPC provides a fast ion transport channel and a large ion accessible specific surface area (SSSA). Meanwhile, the high heteroatom doping and graphitization synergistic promote ion storage (high adsorption energy, Eads) and electron transport. The specific capacitance (C) of optimized CHPC900 can obtain 335 F g−1 under 0.5 A g−1. The C retention is 96.2% after 10,000 cycles at 1 A g−1. CHPC900//CHPC900 delivers remarkable energy/power characteristics (9.9 Wh kg−1 of 125 W kg−1).