Transition-metal-
and nitrogen-codoped carbide-derived carbon/carbon
nanotube composites (M-N-CDC/CNT) have been prepared, characterized,
and used as cathode catalysts in anion-exchange membrane fuel cells
(AEMFCs). As transition metals, cobalt, iron, and a combination of
both have been investigated. Metal and nitrogen are doped through
a simple high-temperature pyrolysis technique with 1,10-phenanthroline
as the N precursor. The physicochemical characterization shows the
success of metal and nitrogen doping as well as very similar morphologies
and textural properties of all three composite materials. The initial
assessment of the oxygen reduction reaction (ORR) activity, employing
the rotating ring–disk electrode method, indicates that the
M-N-CDC/CNT catalysts exhibit a very good electrocatalytic performance
in alkaline media. We find that the formation of HO
2
–
species in the ORR catalysts depends on the specific
metal composition (Co, Fe, or CoFe). All three materials show excellent
stability with a negligible decline in their performance after 10000
consecutive potential cycles. The very good performance of the M-N-CDC/CNT
catalyst materials is attributed to the presence of M-N
x
and pyridinic-N moieties as well as both micro-
and mesoporous structures. Finally, the catalysts exhibit excellent
performance in in situ tests in H
2
/O
2
AEMFCs,
with the CoFe-N-CDC/CNT reaching a current density close to 500 mA
cm
–2
at 0.75 V and a peak power density (
P
max
) exceeding 1 W cm
–2
. Additional
tests show that
P
max
reaches 0.8 W cm
–2
in an H
2
/CO
2
-free air system
and that the CoFe-N-CDC/CNT material exhibits good stability under
both AEMFC operating conditions.
We study the physico-chemical properties and electrocatalytic activity towards oxygen reduction of two Fe–N–C catalysts based on carbide derived carbon.
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