Synthesis of Iodine-Functionalized Graphene Electrocatalyst Using Deep Eutectic Solvents for Oxygen Reduction Reaction and Supercapacitors

Iodine-functionalized reduced graphene oxide (I@RGO) as an active oxygen reduction reaction (ORR) electrocatalyst and energy-storage material for supercapacitors is synthesized. Herein, a novel deep eutectic solvent (DES) of choline chloride and potassium triiodide is prepared. It is applied to reduce GO and for the consequential functionalization of iodine. The metal-free iodine-functionalized graphene is prepared by a facile method, which has a decent electrocatalytic activity for ORR. However, the triiodide structure in I@RGO demonstrates an essential role, considerably indicating electron transfer numbers of 3.87 at a potential of −0.25 V that suggests that the reaction follows a more predominant 4e⁻ (equivalent) pathway. The material also exhibits 242 F g⁻¹ specific capacitance and 27.2 Wh kg⁻¹ energy density at a current density of 1 A g⁻¹. The electrochemical activity of different materials is analyzed and equally compared with a commercial Pt/C electrode. Based on these noteworthy properties, I@RGO is an excellent contender as a metal-free ORR catalyst and energy-storage material for practical applications.