Facile fabrication of sandwich-structured Co3O4/N-rGO/AB hybrid with enhanced ORR electrocatalytic performances for metal–air batteries
Exploring alternative catalysts with low cost and high catalytic performance to the existing Pt and Pt-based catalysts used in oxygen reduction reactions (ORR) is crucial for the extensive commercial application of metal–air batteries and fuel cells. Herein, we have rationally designed and facilely synthesized a sandwich-structured Co3O4/N-reduced graphene oxide (rGO)/acetylene black (AB) hybrid as a novel ORR catalyst for these renewable energy conversion/storage devices. With N doped to rGO, the size of the Co3O4 nanoparticles decreases pronouncedly and the ORR activity enhances significantly when compared to Co3O4/rGO/AB and Co3O4/rGO. At the same time, rotating-disk electrode measurements reveal that the electrocatalytic reduction process using Co3O4/N-rGO/AB is a 4e transfer pathway, while Co3O4/rGO/AB and Co3O4/rGO hybrids possess a reduction process of dominant 4e with partial 2e. Remarkably, Co3O4/N-rGO/AB displays superior electrochemical performance including activity and durability in comparison with commercially available Pt/C, which is further confirmed by the full cell tests for aluminum–air batteries with them as the electrocatalysts, suggesting that Co3O4/N-rGO/AB is a promising candidate as an alternative to Pt and Pt-based catalysts.