1D Pd-Based Nanomaterials as Efficient Electrocatalysts for Fuel Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 327

Fig. 8 Typical SEM images of a AAO template, b surface of Pd nanowire arrays (NWAs) with
the diameter of 50 nm, c cross-section of Pd NWAs and d TEM image and EDX (inset)ofPd
NWAs. Reprinted from Ref. [ 71 ] with permission by Elsevier

(EAA) of Pd/Pt core-shell NWAs electrode is 51 and 20 times larger than that of Pt
thin film and PtRu/C electrode, respectively. This extremely high EAA from Pd/Pt
core-shell NWAs shows that Pd/Pt core-shell NWAs nanostructure can substantially
increase the effective electrochemical active sites most likely due to the very high
surface-to-volume ratio of the highly ordered NWA core nanostructure and the high
roughness of the Pt shell. By comparing the CVs in Fig. 10 b, the Pd/Pt core-shell
NWAs exhibit superior performance for methanol oxidation. It can be seen that the
onset oxidation potential on Pd/Pt core-shell NWAs (0.19 V vs. SCE) is more
negative than those on PtRu/C (0.21 V) and Pt thin film (0.39 V). The electrocata-
lytic activity, as measured by the peak current density in the forward scan is
22.7 mA cm -2 for the Pd/Pt core-shell NWAs, which is nearly 4.2 and 8.7 times
higher than that of the E-TEK PtRu/C and Pt thin film electrodes. On the other hand,
the peak potential for methanol oxidation on the Pd/Pt core-shell NWAs electrode is
170 mV more negative than that on the conventional PtRu/C electrode, indicating
the enhanced electrode kinetics. Moreover, the Pt mass specific current peak density
is 756 : 7mAmg 1

Pt for the Pd/Pt core-shell NWAs electrode, which is four times
higher than the E-TEK PtRu/C electrode (180 : 0mAmg 1

Pt ). Since Pd is electrocat-
alytically inactive in acidic media, the high EAA and mass specific current for
methanol oxidation can be mainly attributed to the Pt shell sputtered on the surface of
Pd NWAs core.