Chemical activation of carbon materials for supercapacitors: Elucidating the effect of spatial characteristics of the precursors

Abstract

Chemical activation has been extensively investigated in various activated carbons, however, the effect of spatial characteristics of carbon precursors on the chemical activation has been rarely reported. Herein, we employed identical KOH activation to activate three carbon precursors including one-dimensional (1D) carbon nanotube (CNT), two-dimensional (2D) reduced graphene oxide (RGO), and three-dimensional (3D) mesoporous carbon (MC). To elucidate the key role of the spatial characteristics of carbon precursors, we compared their evolution of morphology, pore feature as well as supercapacitive performance upon the KOH activation. It was observed that the dimensionality features of the three carbons remained unchanged after activation. With regard to the pore structure, small pores (0.7 ∼ 4 nm) were generated in the CNT walls, and the mesopore derived from the CNT entanglement became smaller after activation. Numerous micropores were generated in the basal plane of RGO, but the meso-macroporous structure was totally destructed by the activation. By contrast, the mesoporous structure of MC was retained except for the enlarged mesopores, and abundant micropores were generated in the pore walls. When applied as supercapacitor electrodes, the various pore structure and spatial characteristics also make the activated carbons perform significantly differently, in which the activated MC own the highest capacitance value of 202 F g−1 at 1 A g−1 and the activated RGO own the highest capacitance retention of 95 % at 10 A g−1. Our results may provide valuable references to the chemical activating of carbon materials for optimizing the supercapacitive performance.