The study of NO adsorbate layers on platinized platinum in the liquid phase with cyclic voltammetry, DEMS and FTIRS

The irreversible adsorbates formed after exposure of platinum to an NO-containing solution were studied with Differential Electrochemical Mass Spectrometry (DEMS), Fourier-Transform Infrared Spectroscopy (FTIRS) and cyclic voltammetry. DEMS and FTIRS show that only a very small amount of N2O is formed in the reduction of the adsorbate, indicating that mainly non-volatile products are formed. FTIRS shows, in addition, vibrations of NO at wavenumbers characteristic of adsorbed NO on Pt(100) and Pt(110) sites. These two different adsorption sites are characterized by separate reduction peaks in the cyclic voltammogram. Further, it was established with FTIRS that the adsorbate is transformed to N2O and NH4+ in the reduction, and to NO3- in the oxidation. Analysis of the charges involved in the reduction and oxidation of the irreversible adsorbates demonstrates that coadsorbates are present next to NO. The coadsorbates consist of adsorbed nitrogen atoms, formed by the dissociation of NO. This view is supported by previously reported studies in Ultra High Vacuum (UHV). A new mechanism for the reduction of NO to N2O in the liquid phase is proposed on the basis of NO dissociation.