Stable electrode material for use in supercapacitor with iodine doping after sulfonation of mesoporous activated carbon particles based on microalgae biomass

Abstract Developing appropriate electrode materials is crucial for achieving supercapacitors with high power output and extended cycle life. Among these, biomass-derived carbon electrodes hold a prominent position in supercapacitor applications. However, these electrodes need to be modified by appropriate methods to increase their performance. In this study, sulphur and iodine heteroatom functionalization was performed using a hydrothermal method on activated carbon (SPAC) derived from a microalgae precursor through potassium hydroxide activation, resulting in iodine- and sulphur-doped SPAC (iodine@S-doped SPAC). Characterization was carried out with Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), energy-dispersive X-ray spectroscopy (EDS), and nitrogen adsorption/desorption analyses. The electrochemical properties of the resulting composite material as a supercapacitor were examined. A specific capacitance of 208.95 F/g was achieved with the iodine@S-doped SPAC supercapacitor. The maximum energy density and power density of the supercapacitor, derived from the iodine@S-doped SPAC sample, were calculated as 5.11 Wh/kg and 2000 W/kg, respectively. Additionally, the coulombic efficiency of this supercapacitor was calculated to be 87.57% at a current density of 0.06 A/g. It also exhibited a capacity retention of up to 89.72% over 1000 cycles.