Oxygen Reduction Reaction on Graphene in an Electro‐Fenton System: In Situ Generation of H 2 O 2 for the Oxidation of Organic Compounds

Fenton oxidation using an aqueous mixture of Fe 2+ and H 2 O 2 is a promising environmental remediation strategy. However, the difficulty of storage and shipment of concentrated H 2 O 2 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 H 2 O 2 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 Fe 2+ . The π bond of the oxygen is broken whereas the σ bond is generally preserved on the metal‐free reduced graphene oxide owing to the high free energy change. Consequently, the oxygen is reduced to H 2 O 2 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 H 2 O 2 . 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 H 2 O 2 .