Spectroelectrochemical Studies of the Pt(111)/Nafion Interface Cast Electrode

Abstract

Understanding the structure and molecular processes at the electrode/membrane interfaces constitutes an important topic in PEFC as well as in electrochemistry. In this work, the Pt(111)/Nafion model interface in HClO4 acid solutions is studied by IRRAS and cyclic voltammetry. It was found that the presence of an electric field mainly promotes deprotonation of sulfonic groups and structuring of water inside the membrane (polar molecules), especially near the electrode surface, with a sudden change of system optical properties at the Pt(111)/membrane interface at 0.9 V, possibly due to clustering within the polymer. Furthermore, the performance of the Pt(111)/Nafion in a typical electrochemical reaction as CO oxidation has been also analyzed. It is shown that there are notable differences between the characteristics of CO adsorption and oxidation at Pt(111) with and without polymer electrolyte membrane, like a continual wavenumber increase with the potential for the on-top CO band, even during CO oxidation, which proceeds at higher potentials at the electrode covered by the polymer. The spectroscopic features suggest enhanced proton mobility inside the membrane concomitantly with the deprotonation of sulfonic groups near the electrode surface and with higher potentials, possibly due to oriented morphologies inside the membrane induced by high fields.