Fecl3 Induced Catalytic Activation Prepared Porous Carbon with Carbon Nanotube Skeleton from Coal for Supercapacitor Electrodes

Abstract

Poor conductivity and pore utilization of porous carbon (PC) have limited its use for supercapacitor electrodes. A simple FeCl3 induced catalytic KOH activation method was used to adjust the pore structure and graphitic carbon skeleton of coal-based PC. Under atmosphere of activation, the Fe component can be transformed into Fe3C, and then the Fe3C may act as catalysts for the deposition of activated gases, such as CO and CH4, to form carbon nanotubes (CNTs). As a result, the CNTs as graphite skeleton in situ growth in the PC (PC-CNTs), which enhances the conductivity and stability of the materials. The PC-CNTs sample shows hierarchical porous structure with surface area (SBET) of 2,178.11 m2·g-1. As supercapacitor electrode, it exhibits a specific capacitance of 224.41 F·g-1 at a current density of 1 A·g-1, and maintains 182.66 F·g-1 at 10 A·g-1. Furthermore, a PC-CNTs//PC-CNTs symmetrical supercapacitor retains 98 % of its initial capacitance after 20,000 cycles at 1 A·g-1. This study employed in situ pyrolysis gas from coal as a carbon source to prepare CNTs for adjusting the pore structure and graphitization of PC, which provides new insights for the utilization of low-rank coal in supercapacitor applications.

Keywords: Coal-based porous carbon, carbon nanotube, graphitization, growth mechanism, supercapacitor