Effect of Redox Electrolyte on the Specific Capacitance of SrRuO3–Reduced Graphene Oxide Nanocomposites

In this work, we studied the effect of adding a redox electrolyte on the specific capacitance of SrRuO 3 –reduced graphene oxide (SRGO) nanocomposite electrode. Two redox systems were considered, quinone/hydroquinone and triiodide/iodide (I 3 – /I – ) in acidic (H 3 PO 4 ) and neutral (NaNO 3 ) solutions. The employment of reduced graphene oxide reduces the amount of Ru loading to the surface down to 20% to achieve a specific capacitance ( C s ) of 62.4 F·g –1 in 1.0 M NaNO 3 and 101 F·g –1 in 1.0 M H 3 PO 4 . The C s of the electrode increased by 21.6 folds in KI-containing NaNO 3 solutions compared with the NaNO 3 electrolyte. The presence of the redox system in the electrolyte enhanced the cycling stability of the electrode to 173% compared with its initial value after 1000 galvanic charging/discharging (GCD) cycles compared with 93% in its absence. The presence of redox-intermediates including iodine (I 2 ) participate in the surface reaction and contribute to the observed enhancement in both C s and cycling GCD. A maximum C s value of 1037 F·g –1 (733 mF·cm –2 ) at 5 A·g –1 was obtained by using SRGO/0.08 M KI–1.0 M NaNO 3 .