Response surface optimization of coal tar-based porous carbon and its supercapacitor performance analysis

Abstract

Coal tar-based pores carbon (PC) is a widely studied electrode material for supercapacitors. However, coal tar-based PC has fewer oxygen-containing groups on the surface, less developed pores, and poor wettability limits its electrochemical performance. Therefore, it is necessary to modulate the structural characteristics of PC by changing the activation conditions, which in turn improves their electrochemical properties, and to explore the applicable environments for PC electrode materials. Here in the paper, coal tar-based PC was prepared by low-temperature solvothermal and activation methods using microcrystalline cellulose-HCl as an additive, based on single-factor results as a basis for designing response optimization experiments. The optimized PC was characterized by SEM, TEM, FT-IR, XPS, XRD, and nitrogen adsorption and detestation tests for its morphology and structure, and oxygen-rich, hierarchical PC with larger layer spacing was obtained. Meanwhile, three-electrode and two-electrode performance tests were performed on different electrolytes. Among them, the three-electrode system in an alkaline environment has good electrochemical performance. The current was increased from 0.3 A g⁻¹ to 10 A g⁻¹, the specific capacitance was decreased from 317 F g⁻¹ to 220 F g⁻¹, and the capacitance retention was as high as 95.2 % after 10,000 cycles at 5 A g⁻¹. In the two-electrode system in a neutral environment, the energy density was 23.4 Wh kg⁻¹ at an output power of 296.0 W kg⁻¹. The capacity retention was 68.7 % after 5000 cycles at 2 A g⁻¹. The results demonstrated that coal tar-based PC has some application value in supercapacitor electrode materials.