Abstract:
Palladium based nano-alloys are well known for their unique electrocatalytic properties. In this work,
a palladium-decorated FeCo@Fe/C core–shell nanocatalyst has been prepared by a new method
called microwave-induced top-down nanostructuring and decoration (MITNAD). This simple, yet efficient
technique, resulted in the generation of sub-10 nm sized FeCo@Fe@Pd nanocatalysts (mainly 3–5 nm)
from a micron-sized (0.21–1.5 mm) FeCo@Fe/C. The electrocatalytic activities of the core–shell nanocatalysts
were explored for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR)
in alkaline medium. A negative shift of 300 mV in the onset potential for MOR was observed, with a
current thrice that of the Pd/C catalysts. A very low resistance to electron transfer (Rct) was observed
while the ratio of forward-to-backward oxidation current (If/Ib) was doubled. The overpotential of ORR
was significantly reduced with a positive shift of about 250 mV and twice the reduction current
density was observed in comparison with Pd/C nanocatalysts with the same mass loading. The kinetic
parameters (in terms of the Tafel slope (b) = 59.7 mV dec 1 (Temkin isotherm) and high exchange
current density ( jo) = 1.26 10 2 mA cm 2) provide insights into the favorable electrocatalytic performance
of the catalysts in ORR in alkaline media. Importantly, the core–shell nanocatalyst exhibited
excellent resistance to possible methanol cross-over during ORR, which shows excellent promise for
application in direct alkaline alcohol fuel cells (DAAFCs).
