Efficient and Durable Oxygen Reduction Electrocatalyst\nBased on CoMn Alloy Oxide Nanoparticles Supported Over N‑Doped\nPorous Graphene

Abstract

Transition\nmetal oxide derived materials are very important for\nvarious applications, such as electronics, magnetism, catalysis, electrochemical\nenergy conversion, and storage. Development of efficient and durable\ncatalysts for the oxygen reduction reaction (ORR), an important reaction\nin fuel cells and metal–air batteries, is highly desirable.\nMoreover, the futuristic catalysts for these applications need to\nbe cost-effective in order to ensure a competitive edge for these\ndevices in the energy market. This article describes the synthesis\nof a cost-effective and efficient electrocatalyst for ORR. It is based\non supporting CoMn alloy oxide nanoparticles on N-doped porous graphene\nthrough a simple and scalable microwave irradiation method. Microwave\nirradiation was found to be very crucial for the fast creation of\npores in the graphene framework with a concomitant formation of the\nCoMn alloy oxide nanoparticles. A series of catalysts have been synthesized\nby varying the Co:Mn ratio, among which, the one with the Co:Mn ratio\nof 2:1 [designated as CoMn/pNGr(2:1)] displayed remarkably higher\nORR activity in 0.1 M KOH solution. It showed a ∼60 mV potential\nshift with a low Tafel slope of 74 mV/decade, which is comparable\nto that derived from the commercial Pt/C catalyst. This high activity\nof CoMn/pNGr(2:1) has been credited to the cooperative effect arising\nfrom the metal entities and the defects present in the N-doped porous\ngraphene. Finally, real system-level validations of the use of CoMn/pNGr(2:1)\nas cathode catalyst could be performed by fabricating and testing\nsingle-cells of an anion-exchange membrane fuel cell (AEMFC) and a\nprimary Zn–air battery, which successfully demonstrated the\nefficiency of the catalyst to facilitate ORR in real integrated systems\nof the single-cell assemblies.