Proving The Existence Of Mn Porphyrin-Like Complexes Hosted In Reduced Graphene Oxide With Outstanding Performance As Oxygen Reduction Reaction Catalysts

The lack of low-cost, durable and highly efficient electrocatalysts to perform oxygen reduction reaction (ORR) still represents a significant challenge for the development of fuel cells cathodes. Recently, Pt-free metalloporphyrins supported on N-doped reduced graphene oxide (N-rGO) have been proposed as innovative ORR catalysts characterized by notable stability and superior performance. In this paper, we propose a fast and green microwave-assisted method to synthetize manganese-nitrogen co-doped rGO, characterized by catalytic activity comparable to Pt-containing materials and improved long-term stability. Theoretical calculations and experimental results showed that our synthetic method produces N-rGO matrices which coordinate Mn2+ ions in porphyrin-like structures. These Mn/N-rGO complexes are responsible for the outstanding performance of the proposed catalyst, being able to weaken O-O molecular bond, thus effectively reducing the activation energy towards oxygen catalytic reaction. Our findings open the path to a green co-doping process of graphene for the production of low-cost and efficient alternatives to noble metals-based ORR catalysts.