Low-Cost Nanomaterials for High-Performance Polymer Electrolyte Fuel Cells (PEMFCs) - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 371

Fig. 9 Comparison of the transient current density curves of Pt/C-multipod, Pt/C-disc, Pt/C-
hexagon and Pt/C towards a formic acid oxidation and b ethanol oxidation (adapted from Ref.
[ 113 ] with permission from American Chemical Society)
might be helpful for some special applications like molecular interconnects, where
directional control of electron transfer is important. It is, however, possible to tune
these parameters by controlling the template design strategies. Similarly, the
fabrication of other potential junction structures such as X and T is possible by a
slight modification of the above template-design strategy.
In order to correlate the structure with activity, electrochemical oxidation
reactions of formic acid and ethanol have been studied at different shaped Pt
structures such as Pt multipods, Pt discs and Pt hexagons synthesized through the
template-assisted route (vide supra) [ 113 ]. Accordingly, Fig. 9 a reveals the com-
parison of the transient current density responses of these structures and
commercial platinized carbon (Pt/C) towards formic acid oxidation at a particular
potential, where the oxidation current density of Pt hexagons is significantly higher
than those of Pt multipods, Pt discs and Pt/C. In contrast, for ethanol oxidation
(Fig. 9 b) the observed order of oxidation current density is as follows: Pt/C-
multipods [ Pt/C-discs [ Pt/C-hexagons [ Pt/C. Interestingly, the R value for
these structures with respect to that of Pt/C is calculated from the steady-state
current density at different potentials. The value of R for formic acid oxidation
ranges up to 2,000 % for hexagons, whereas for multipods and disc, it is about 700
and 300 % respectively. Similarly, for ethanol oxidation, the calculated value of R
varies up to 600 % for multipods, while for discs and hexagons this is 500 and
200 % respectively.
Hence, it is clear that for formic acid oxidation, Pt hexagons show better
catalytic activity compared to other shapes. The origin of this shape-dependent
electrocatalytic activity arises mainly due to the higher density ratio of (111)/(100)
crystallographic planes present in Pt hexagons compared to that in other structures
and commercial platinized carbon (calculated from XRD results). This could be
correlated to the structural effect of Pt single crystal electrodes on formic acid
oxidation, which reveal that formic acid oxidation to CO 2 proceeds favourably on