Core@Shelled Co/CoO Embedded Nitrogen-Doped Carbon Nanosheets Coupled Graphene as Efficient Cathode Catalysts for Enhanced Oxygen Reduction Reaction in Microbial Fuel Cells

Abstract

High-efficiency oxygen reduction reaction (ORR) catalysts are crucial for facilitating the large-scale exploitation of electrochemical energy storage and conversion technologies. Herein, we demonstrate a carbon-based metal hybrid, which offers a higher electrocatalytic activity than that of the individual composite by optimizing the electronic modulation effect from suitable microstructure. The resulting cobalt@cobalt oxide nanoparticles embedded in N-doped carbon shell couple with hierarchical porous graphene (GCN–Co@CoO), exhibiting a significantly enhanced ORR activity in alkaline solution and highlighting a synergistic effect between N-doped carbon shell and metallic Co species. More precisely, the GCN–Co@CoO hybrid pyrolyzed at 800 °C achieves a more positive half-wave potential of −0.194 V (vs SCE) and superior limiting current of 4.91 mA cm–2. Moreover, the GCN–Co@CoO composite also shows an outstanding tolerance to methanol crossover effects and long-term stability. Furthermore, based on the GCN–Co@CoO cathode catalyst, the self-assembled microbial fuel cells perform a maximum power density of 611 ± 9 mW m–2 at a high current density of 1869 ± 24 mA m–2.