Chemical co-activated modified small mesoporous carbon derived from nature anthracite toward enhanced supercapacitive behaviors

Abstract

Chemical co-activation is a valid avenue to achieve the surface chemical modification and pore configuration regulation of carbon electrode materials, thus greatly facilitating their capacitive behaviors. In the study, ultrapure anthracite-derived porous carbons (PCs) with small mesopore development are synthesized via KOH pre-etching of natural coal for pore-creating, closely followed by H3PO4 deep activation for pore-expanding and carbon surface stabilization. Phosphoric acid post-activation under increased temperature not only creates abundant small mesopores for fast ions transport, but improves the surface chemistry on carbon skeleton to boost the capacitance reversibility. When assessed as electro-chemical double-layer capacitor (EDLC) electrodes in KOH electrolyte, the resulting co-activated PC demonstrates low internal resistance of less than 2.50 mΩ, high specific capacity of up to 212F g−1, and superior rate capability of 71.82% at 10 A g−1. More importantly, due to the enhancement of oxidation stability of optimal electrode by the reduction of unstable chemical groups on carbon surface, the constructed organic supercapacitor can be quickly charged or discharged for a long period in 1 m (C2H5)4NBF4 electrolyte, so as to deliver an excellent cycling stability of 97.52% capacitance retention. This study realizes the high value-added and efficiently clean utilization of anthracite as a non-renewable resource, as well as offering profound electrochemical insights for large scale application of small mesoporous carbon towards next-generation high-power smart devices.