1D Pd-Based Nanomaterials as Efficient Electrocatalysts for Fuel Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 331

Fig. 13 CVs measured on a
Pd film electrode (curves a,
Pd loading: 1.1 mg cm -2 ),
E-TEK PtRu (2:1 by weight)/
C electrode (curves b,Pt
loading: 0.24 mg cm -2 ), and
Pd NWA electrode (curves c,
Pd loading: 0.24 mg cm -2 )in
1.0 M KOH + 1.0 M
C 2 H 5 OH (upper panel) and
1.0 M KOH (lower panel)
solution at a scan rate of
50 mV s -1 . Reprinted from
Ref. [ 69 ] with permission by
Wiley-VCH
electrocatalyst. The negative shift of onset potential indicates the significant
enhancement in the kinetics of the ethanol oxidation reaction on Pd NWAs. Similarly
to methanol oxidation on Pt-based electrocatalysts in acid media, ethanol oxidation
on Pd NWA electrode is also characterized by well-separated anodic peaks in the
forward and reverse scans. The anodic peak current density on the Pd NWA elec-
trode is seven times of that on the Pd film electrode and almost twice of that on the
PtRu/C electrode. The obtained electrochemical results indicate that the 1D Pd
NWA nanomaterials could be an efficient anode electrocatalysts for direct ethanol
AFCs.
Interface formed in a bimetallic system plays an important role in the catalytic
promotional effect and studies on bimetallic interface are also critical to investi-
gate the fundamental mechanism of enhanced electrocatalytic activity for fuels
oxidation. Recently, Yu et al. [ 80 ] designed unsupported Pd-Au bimetallic tubular
nanostructures through one-step nonaqueous solvent electrodeposition method and
studied their catalytic activity for electrooxidation of ethanol. With the electro-
deposition method, tubular, dispersed, and unsupported Pd-Au bimetallic het-
erostructure tubes (BHTs) were formed with controlled atom percentage of Pd and
with several micrometer-sized lengths as measured by SEM (Fig. 14 a, b). The
TEM image in Fig. 14 c indicates the uniform wall thickness of the nanotubes,
composed of many flocky-like spheres. Moreover, the unique porous structure of
the BHTs could promote the mass transfer and effectively expose their inner and
outer surfaces. From the HRTEM images shown in Fig. 14 d-f, the single Au
nanoparticle and the interfaces of Au-Pd and Au-Au can be observed clearly. The
resultant tubular materials demonstrated high surface area, high stability, and