R. Gomez et J. Clavilier, ELECTROCHEMICAL-BEHAVIOR OF PLATINUM SURFACES CONTAINING (110) SITES AND THE PROBLEM OF THE 3RD OXIDATION PEAK, Journal of electroanalytical chemistry [1992], 354(1-2), 1993, pp. 189-208
The voltammetric behaviour of flame-treated Pt(110) electrodes has bee
n studied for different cooling atmospheres. It can be stated that avo
iding thermally adsorbed oxygen during the cooling step gives rise to
samples with the lowest density of surface defects. Electrochemical cr
iteria for checking the cleanliness of this orientation have been prop
osed. They involve the voltammetric characteristics of both hydrogen a
nd oxygen adsorption-desorption processes. The monitoring of surface c
leanliness by the two adspecies is due to the ambiguous interpretation
of hydrogen adsorption-desorption only, whose voltammetric profile is
not affected significantly by surface contaminants, while the change
of the hydrogen electrical charge could be ascribed to two independent
origins, either contamination or reconstruction lifting. Then, the pr
oblem of the so-called peak III is treated by considering Pt(110) prep
ared with different surface conditions and the stepped surfaces contai
ning (110) sites on terraces or steps, respectively. It may be conclud
ed that formation of peak III occurs if surface domains of (110) sites
with a minimum size are present. Conversely, (110) sites far apart on
the surface cannot give rise to peak III. A mechanism for the formati
on of a well defined type of site at high hydrogen coverage is discuss
ed which accounts for the irreversibility of the adsorption desorption
process ascribed to peak Ill where hydrogen is the desorbing species.