On the behavior of Pt(111)-Bi in acid and alkaline electrolytes

We studied the base voltammetry of Pt(111) modified by irreversibly adsorbe d Bi in both 0.1 M HClO4 and 0.1 M NaOH. By comparing the cyclic voltammogr ams in both electrolytes for the same Bi-ir coverages, we found the followi ng. (i) For highly Bi-ir covered surfaces, significantly higher ll pd cover ages are found in alkaline solution, indicating that the H-upd charge canno t be unambiguously correlated to the Bi-ir coverage. (ii) In line with our previous model of enhanced adsorption of OHad on Pt sites adjacent to Bi-ir , we also propose the enhanced formation of surface oxide layers on Pt(111) -Bi-ir electrodes. CO stripping experiments on surfaces with different Bi-i r surface coverages in perchloric acid showed that on a highly Bi covered P t(111) surface the CO oxidation starts at higher potentials than On a surfa ce with lower Bi coverage. This finding implies that in the Langmuir-Hinshe lwood surface reaction for CO oxidation both reaction partners compete for the same adsorption sites, that is, Pt(111)-Bi-ir does not represent a bifu nctional surface.