1D Pd-Based Nanomaterials as Efficient Electrocatalysts for Fuel Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 324

Fig. 6 ORR polarization
curves of commercial Pt/C
(black curve), Pd/C (self-
prepared by EG method, red
curve), Pd 1 -NL/C (green
curve), and Pd 2 -NL/C (blue
curve) in oxygen saturated
0.1 M NaOH (conditions:
10 mV s -1 , 2500 rpm, and
room temperature). Reprinted
from Ref. [ 74 ] with
permission by the American
Chemical Society
the tips and ends are predominated by Pd(110) and Pd(100) facets. The mor-
phology of PdFe-NLs is distinctively different from the Pd nanorods with larger
diameter (5-10 nm) prepared using PVP as a stabilizer. The varied Pd nano-
structures suggest that the different synthesis conditions, i.e., different surfactants,
presence/absence of Fe, etc., can affect the growth mechanisms of 1D nanoma-
terials. By etching away the enveloping Fe-rich sheets using an organic acid, the
Pd-rich NWs are exposed on the surfaces of the nanoleaves, and they demonstrated
high reactivity toward electrocatalytic reduction of oxygen in a 0.1 M NaOH
electrolyte. The ORR polarization curves obtained from different catalysts are
shown in Fig. 6 . It can be observed that the Pd-NLs show a remarkable
improvement in ORR activity with the half-wave potential shifting positively by
*38 mV, compared to commercial Pt/C catalyst. Moreover, the mass activity of
Pd 1 -NL and Pd 2 -NL are 0.159 and 0.157 A mg P -1 , respectively, which are twice
higher than that of Pd/C (0.0735 A mg P -1 ) and *2.7 times higher than that of Pt/C
(0.0585 A mg P -1 ) at 0 V versus Hg/HgO. For the specific activity, the Pd 1 -NLs and
Pd 2 -NLs at 0 V are 312 and 305 lAcm P -2 , respectively, which are higher than that
of Pd/C (207 lAcm P -2 ) and Pt/C (103 lAcm P -2 ). The enhanced electrocatalytic
activity of Pd NLs may be attributed to the unique nanoleave structure, which
provides more Pd(111) facets, a large surface area, and more resistance to oxide
formation.
More recently, Xu et al. [ 77 ] prepared a novel PdCu bimetallic nanotubes with
hierarchically hollow structures via a galvanic displacement reaction by using
dealloyed nanoporous copper as both a template and reducing agent and found
that the PdCu nanocomposites exhibit enhanced ORR activity. In this study,
three-dimensional nanoporous copper (Fig. 7 a, b) was firstly synthesized by
dealloying Cu/Al alloy foils in NaOH. PdCu bimetallic hollow structures were
then produced through a galvanic replacement reaction between nanoporous
copper and K 2 PdCl 4 . The SEM and TEM measurements (Fig. 7 c-f) show that the