The oxygen reduction activity and methanol
tolerance of Pt–Bi/C electrocatalysts were studied using
electrochemical voltammetric techniques including rotating
ring-disk electrode. The Pt–Bi/C catalyst was prepared via a
polyol method and subjected to heat treatment to increase the
degree of alloying. X-ray diffraction studies revealed the
unalloyed character of the as-prepared catalyst and alloy
formation upon heat treatment. The electrochemical behaviour
of both catalysts showed different behaviour in dilute
acid electrolytes, namely sulphuric and perchloric acids. In
both electrolytes, the oxygen reduction reaction was found to
occur via the four-electron process revealing that the
mechanism of oxygen reduction is unaltered even in the
presence of excess of methanol. Pt–Bi/C catalyst material
showed dramatically different properties and reactivity with
respect to oxygen reduction activity and methanol tolerance
in perchloric and sulphuric acids. The onset potential for
oxygen reduction reaction (ORR) significantly shifted by
about 100 mV to more negative values and at the same time
the current density was significantly enhanced. This type of
non-ideal methanol-tolerant behaviour among Pt bimetallics
and a ‘‘trade off’’ is common with all the known so-called
methanol tolerant combinations of Pt. In general, the Pt–Bi
surface appeared to have a negligibly lesser sensitivity
towards methanol activity compared to pure platinum