Hierarchical-nanofiber structure of biomass-derived carbon framework with direct CO2 activation for symmetrical supercapacitor electrodes

Biomass-based activated carbon materials provide a new approach for the development of high-performance electrodes for supercapacitor cells. They are inexpensive and sustainable for the large-scale production of electrode materials. Therefore, this study aims to produce carbon electrodes from date seeds with a hierarchical-nanofiber architecture activated using KOH and CO2. The results showed that the carbon electrode had a framework of interconnected pores in the presence of nanofibers and exhibited excellent electrochemical performance. The pore size distribution can be adjusted with the increased CO2 activation temperature. Furthermore, the hierarchical-nanofiber architecture contained a gradient distribution from nanopores to micropores which has optimal connectivity and increased the capacitance of the electrical bilayer as well as abundant oxygen on the surface or edges of the carbon matrix. The highest specific capacitance was obtained at 258.88 Fg(-1) with a current density of 1 Ag-1 in a symmetrical two-electrode system. The symmetrical supercapacitor cell circuit had an energy density of 7.11 Wkg(-1) with a power density of 125.46 Wkg(-1) in an H2SO4 electrolyte. These results offer an efficient strategy for the preparation of high-performance carbon electrodes based on date seeds biomass.