Striking capacitance of carbon/iodide interface

Exceptional electrochemical behavior of carbon/iodide interface has been demonstrated and successfully used in supercapacitor application. This efficient charge storage is based on specific sorption of iodide ions as well as stable reversible redox reactions connected with various possible oxidation states of iodine from −1 to +5. An intriguing effect of iodide ions has been observed for positive electrode operating in a narrow range of potential and giving extremely high capacitance values exceeding 1840 F/g. As opposed to typical pseudocapacitance effects, which are often characterized by some diffusion limitations and observed only at moderate regimes, our two-electrode system can be loaded until 50 A/g supplying still 125 F/g. Amazing capacitance of carbon/iodide interface has also been confirmed during long-term cycling (over 10 000 cycles). For the first time, such an innovative electrochemical system was successfully used for supercapacitor performance. The iodide ions play a useful dual role, i.e. electrolytic solution with a good ionic conductivity as well as a source of pseudo-capacitive effects.