1D Pd-Based Nanomaterials as Efficient Electrocatalysts for Fuel Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 343

Fig. 24 a, b SEM images and c TEM image of silver nanowires with surface coated with Pd/Ag
alloy sheaths. d PC isotherms for hydrogen desorption from the hydrides of the as-synthesized
Ag@PdAg nanocables at 20, 70, and 120 C. Here H/M is the hydrogen-to-metal ratio. Reprinted
from Ref. [ 119 ] with permission by the American Chemical Society
diffusion can be realized from the PdAg alloys with Ag concentration higher than
63 % [ 124 ].
Sun et al. [ 119 ] synthesized silver nanowires with surface coated by thin
sheaths of Pd/Ag alloys through the galvanic replacement reaction. From the SEM
and TEM images shown in Fig. 24 a-c, each Ag nanowire of *60 nm in diameter
is coated with Pd/Ag sheaths and is straight and uniform in diameter along the
entire long axis. It was found that different from the Pd nanotubes formed from
short Ag nanowires, only some segments of the long Ag wire have been converted
to hollow structure after galvanic replacement reaction. The total percentage of Ag
in the final product was determined to be as high as 92.2 wt%. Figure 24 d shows
the pressure-composition (PC) isotherms of the as-synthesized Ag/Pd nanostruc-
ture (Ag@PdAg) at different temperatures (20, 70, and 120 C). It can be seen that
the distinct plateaus were formed similar to those of polycrystalline Pd powders,
indicating the existence of a broad metal-H miscibility gap for the Ag@PdAg
wires. Moreover, the absorption and desorption of hydrogen were reversible and
the reactions at room temperature were very fast for the Ag@PdAg system. By
comparison, the hydrogen solubility of Ag@PdAg wires is larger than that of Pd
powers, which can be ascribed to the unique structure of PdAg alloy sheath formed
on the Ag nanowires.
Recently, Chen and coworkers [ 94 ] reported that the Pd-Cd nanomaterials with
10-15 % Cd exhibit the highest hydrogen storage ability, over 15 times greater
than the pure Pd nanoporous materials. In their study, the hydrogen storage ability