New insight on the behaviour of the irreversible adsorption and underpotential deposition of thallium on platinum (111) and vicinal surfaces in acid electrolytes

We report, for the first time, the electrochemical behaviour of thallium irreversibly adsorbed on Pt (111) and platinum stepped surfaces composed of (111) terraces and monoatomic steps. Similar to the case of thallium UPD, the voltammograms obtained after thallium irreversible adsorption present three characteristic features. After a careful analysis of the effect of the thallium concentration, the concentration and nature of the anion of the supporting electrolyte and the pH of the solution on these voltammetric features, we have been able to ascribe these processes to Tl/Tl oxidation and anion adsorption on the Tlmodified surface. In addition, the results obtained with stepped surfaces, indicate that some of the features are clearly associated to the presence of (111) surface domains, and thus they could be used for the quantification of these sites.