1D Pd-Based Nanomaterials as Efficient Electrocatalysts for Fuel Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 316

the\110[growth direction of the nanowires [ 82 ]. It is well known that the catalytic
activities of metal nanomaterials are strongly dependent on their exposed surface
facets. Earlier studies have shown that the Pd(100) plane exhibits the highest cat-
alytic activity for formic acid oxygen among the three low-index faces Pd(111),
Pd(100), and Pd(110) [ 83 , 84 ]. On the other hand, the single-crystalline 1D
nanomaterials with structural anisotropy contain fewer surface defect sites in
comparison with the corresponding zero-dimensional nanoparticles. When used as
electrocatalysts, the electron transport properties of catalyst materials are of
importance for the electrochemical reactions. Compared to metal nanoparticles, 1D
nanomaterials can provide more efficient electron transfer, thus lowering the elec-
tronic resistance and enhancing the fuel oxidation or Oxygen reduction reactions
[ 76 , 85 ]. Meanwhile, for nanoparticle-based electrocatalysts, the electrochemical
scanning process may lead to the particle aggregation, dissolution, and Oswald
ripening, which is one of the biggest challenges in designing efficient fuel cell
electrocatalysts. However, for 1D nanomaterials, the asymmetric structure nature
can effectively prevent their structure destruction from aggregation, dissolution, and
ripening [ 75 , 86 , 87 ]. From above, the large surface area, high electrochemical
stability, efficient electron transport, and excellent CO-tolerance of 1D Pd-based
nanomaterials would be highly advantageous for their applications in fuel cells as
anode and cathode catalysts.
Among the fuels fed to the anode of fuel cells, hydrogen is considered to be one of
the most promising clean energy carriers due to its light weight, high energy density,
and no harmful chemical by-products from its combustion. Hydrogen can be gen-
erated from renewable sources, such as water splitting via photolysis [ 88 - 92 ]. For
hydrogen powered fuel cells, despite prodigious efforts, how to develop a safe and
easy storage method is still a remaining significant challenge for the widespread
application of hydrogen as the fuel of choice in mobile transportation. The efficient
and safe storage of hydrogen is crucial for promoting the ''hydrogen economy''. The
safety and cost issues of conventional hydrogen storage as compressed gas or liquid
largely limit the practical use of these methods. Other developed methods for
hydrogen storage by physical adsorption on materials with large surface area or
formation of chemical bonds have been proved to be efficient, convenient, and safe
approaches [ 93 ]. Among the hydrogen storage materials, Pd-based nanomaterials
exhibited excellent storage capacity and their storage properties are strongly related
to the morphologies, composition, and size of the nanostructures [ 94 ].
In this chapter, we highlight the recent progress of one-dimensional Pd-based
nanomaterials, including the synthetic techniques and their application in fuel cells
as electrocatalysts on both anode and cathode sides. With different preparation
routes, various structured nanomaterials with different surface morphologies can be
realized. Since the composition and surface structure of Pd-based alloy materials
play decisive roles in determining their electrocatalytic properties, the structure and
properties of 1D Pd materials can be manipulated by changing synthetic conditions
to meet the scientific and technological demands of fuel cell catalysts. In addition,
the application of one-dimensional Pd-based nanomaterials in the hydrogen storage