Enhancement of the carbon electrode capacitance by brominated hydroquinones

This paper presents supercapacitors utilizing new redox-active electrolytes with bromine species. Two sources of Br specimen were investigated, i.e. dibromodihydroxybenzene dissolved in KOH and potassium bromide dissolved in KOH with hydroxybenzene additive. KOH-activated carbon, exhibiting a well-developed porosity, was incorporated as an electrode material. The tested systems revealed a capacitance enhancement explained by Br− and partial BrO3− redox activity. The optimisation of the electrolyte concentration resulted in a capacitance value of 314 F g−1 achieved at 1.1 V voltage range. Good cyclability performance (11% capacitance loss) combined with a high capacitance value (244 F g−1) were obtained for the system operating in 0.2 mol L− 1 C6H4Br2O2 in 2 mol L−1 KOH electrolytic solution.