Figure 5. (a) Rechargeable energy density of the redox capacitor (TCHQ-DCAQ) in 0.5 M H₂SO₄ aqueous solution at 0.26 A/g as a function of cycle time, and (b) the evolution profiles of the potential corresponding to the positive (TCHQ) and negative (DCAQ) electrodes at the 100^th and 1000^th cycles.