Oxygen Reduction Reaction on Graphene in an Electro-Fenton System: In Situ Generation of H2O2 for the Oxidation of Organic Compounds

Fenton oxidation using an aqueous mixture of Fe2+ and H2O2 is a promising environmental remediation strategy. However, the difficulty of storage and shipment of concentrated H2O2 and the generation of iron sludge limit its broad application. Therefore, highly efficient and cost-effective electrocatalysts are in great need. Herein, a graphene catalyst is proposed for the electro-Fenton process, in which H2O2 is generated in situ by the two-electron reduction of the dissolved O-2 on the cathode and then decomposes to generate OH in acidic solution with Fe2-. The a bond of the oxygen is broken whereas the G bond is generally preserved on the metal-free reduced graphene oxide owing to the high free energy change. Consequently, the oxygen is reduced to H2O2 through a two-electron pathway. The thermally reduced graphene with a high specific surface area (308.8 m(2)g(-1)) and a large oxygen content (10.3 at%) exhibits excellent reactivity for the two-electron oxygen reduction reaction to H2O2. A highly efficient peroxide yield (64.2%) and a remarkable decolorization of methylene blue (12 mg L-1) of over 97% in 160 min are obtained, The degradation of methylene blue with hydroxyl radicals generated in situ is described by a pseudo first-order kinetics model. This provides a proof-of-concept of an environmentally friendly electro-Fenton process using graphene for the oxygen reduction reaction in an acidic solution to generate H2O2.