Page 103 - MODERN ASPECTS OF ELECTROCHEMISTRY

Claude LamyAet al.
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oxidized groups, the strength of the Pt–O bonds on the particle surface can
be modified. From this point of view, adsorbed OH species are necessary
for the rate-determining step of methanol oxidation; the particle size
effects, as observed in the results of this study, are quite valuable.
Another convenient way to disperse platinum-based electrocatalysts
is to use electron-conducting polymers, such as polyaniline (PAni) or
polypyrrole (PPy), which play the role of a three-dimensional elec-
trode. 50,51 In such a way very dispersed electrocatalysts are obtained, with
particle sizes on the order of a few nanometers, leading to a very high
activity for the oxidation of methanol (Fig. 10).
Finally, a simple method for a rapid evaluation of the activity of high
surface area electrocatalysts is to observe the electrocatalytic response of
a dispersion of carbon-supported catalyst in a thin layer of a recast proton
52
exchange membrane. This type of electrode can be easily obtained from
a solution of Nafion. As an example, Fig. 11 gives the comparative

Figure 10. Electrocatalytic oxidation of 1 M CH OH in
3
0.5 M HClO 4 on a platium electrode dispersed in polanil-
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ine (Pt loading 5 mg cm ,sweep rate 5 mV s ).
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