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 Ma ss Spectrometry (DEMS), Fourier-Transform Infrared Spectroscopy (FTIRS ) and cyclic voltammetry. DEMS and FTIRS show that only a very small a mount of N2O is formed in the reduction of the adsorbate, indicating t hat mainly non-volatile products are formed. FTIRS shows, in addition, vibrations of NO at wavenumbers characteristic of adsorbed NO on Pt(1 00) and Pt(110) sites. These two different adsorption sites are charac terized by separate reduction peaks in the cyclic voltammogram. Furthe r, 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 irrevers ible adsorbates demonstrates that coadsorbates are present next to NO. The coadsorbates consist of adsorbed nitrogen atoms, formed by the di ssociation of NO. This view is supported by previously reported studie s 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 .