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Fig. 10 Cyclic
voltammograms of Pt film
electrode, E-TEK PtRu
(33 wt%)/C electrode and Pd/
Pt core-shell NWAs electrode
in a a 0.5 M H
2
SO
4
solution
and b in a 1.0 M methanol
+0.5 M H
2
SO
4
solution at
298 K under a scan rate of
50 mV s
-1
. Pt loading of the
electrodes was
0.03 mg cm
-2
. Reprinted
from Ref. [
72
] with
permission by Elsevier
makes the NWs less subject to dissolution, Ostwald ripening, and aggregation in
acidic solution.
Compared to methanol, ethanol is less toxic and can be produced in large
quantities from agricultural products. Moreover, ethanol is the major renewable
biofuel from the fermentation of biomass. Recent studies have shown that Pd-based
nanomaterials are electrocatalytically active for ethanol oxidation in alkaline med-
ium, representing an important alternative to Pt-based catalysts for direct ethanol
AFCs [
69
,
80
,
105
]. For instance, Jiang and coworkers [
69
] successfully synthesized
highly ordered Pd nanowires arrays (Pd NWA) through the anodized aluminum
oxide (AAO) template-electrodeposition method. The SEM characterizations in
Fig.
12
show that the as-synthesized Pd NWAs after AAO template fully dissolved
are highly ordered with uniform diameter ca. 80 nm and length ca. 800 nm. The
uniform porous structure of the nanowires can effectively improve their ECSA and
thus enhance the active sites for the electrocatalytic reaction. Electrochemical
experiments demonstrated that the as-synthesized Pd NWA exhibited excellent
electrocatalytic activity and stability for ethanol oxidation in alkaline media com-
pared to the conventional Pd film electrodes and the well-established commercial
E-TEK PtRu/C electrocatalysts. As can be seen from Fig.
13
, the onset potential for
the ethanol oxidation on the Pd NWA electrode is -0.62 V, which is 150 mV more
negative than the -0.45 V observed on the Pd film electrode and 40 mV
more negative than the -0.58 V obtained from the conventional E-TEK PtRu/C
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