Hydrogen evolution on platinum in the presence of lead, cadmium and thallium adatoms
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Hydrogen evolution on rotating platinum electrode has been measured in the presence of Pb, Tl and Cd adatoms. At low coverages of these adatoms (θM < 0.5) the mechanism of H2 evolution is the same as that for Pt, giving rise to the Tafel slope of 30 mV with recombination of H adatoms as a rate controlling step. However, H2 evolution decreases with θM to the fourth power, due to a simple blocking of Pt surface and a decrease of number of pairs of Pt atoms necessary for a recombination reaction. At higher coverages of foreign metal adatoms (θM ≥ 0.5), when the activation energy for the recombination of H adatoms becomes too high, the ion-plus atom reaction begins to control the rate of reaction. The Tafel slope acquires a value of 120 mV. Now, a decrease of H2 evolution has been found proportional to the coverage of metal adatoms. A quantitative analysis based on above model agrees very well with the experiment. Some information on underpotential deposition of above metal on Pt has al...so been obtained. © 1979.
Извор:Electrochimica Acta, 1979, 24, 5, 569-576
- Pergamon Press
- Council of Yugoslav Academies of Sciences
- National Academy of Science.
- Research Fund of Serbia
- Serbian Academy of Sciences