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