Co3O4 Nanoparticles Anchored on Selectively Oxidized Graphene Flakes as Bifunctional Electrocatalysts for Oxygen Reactions

Abstract Herein, we report the preparation of Co 3 O 4 nanoparticles anchored on the surface of selectively oxidized graphene flakes with KMnO 4 and O 3 ‐ Co 3 O 4 @GF_KMnO 4 and Co 3 O4@GF_O 3 nanocomposites ‐ and the study of their electrocatalytic performance towards the oxygen reduction (ORR) and oxygen evolution reactions (OER). Both nanocomposites displayed ORR and OER electrocatalytic activity in alkaline medium. For ORR, onset potentials of 0.79 V and 0.82 V vs. RHE were achieved for Co 3 O 4 @GF_ KMnO 4 and Co 3 O 4 @GF_O 3 , respectively. Both nanocomposites presented excellent tolerance to methanol and, in the case of Co 3 O 4 @GF_O 3 , a superior long‐term stability with a current retention of 96.8% after 20 000 s. For OER, the overpotential was 0.44 and 0.45 V for Co 3 O 4 @GF_KMnO 4 and Co 3 O 4 @GF_O 3 , respectively. Additionally, Co 3 O 4 @GF_O 3 presented higher current densities, Faradaic efficiencies, and long‐term stability (current loss of 32% after 15 000 s). The superior bifunctional ORR/OER electrocatalytic activity displayed by Co 3 O 4 @GF_O 3 arises from the stronger chemical coupling between Co 3 O 4 nanoparticles and specific oxygen surface groups of GF_O 3 flakes.