INTEGRATED ELECTROMODULATED IR REFLECTANCE SPECTROSCOPY BANDS .2. METHANOL ADSORBATES AT POLYCRYSTALLINE PLATINUM AND PT(111) SINGLE-CRYSTAL ELECTRODES IN ACID-MEDIUM

Using electromodulated IR reflectance spectroscopy (EMIRS), absorption spectra of adsorbed species resulting from the chemisorption of HCHO, HCOOH and methyl formate, HCOOCH3, on both polycrystalline and (111) platinum surfaces, were first obtained in the range 1400-1900 cm -1, to cover completely the carbonyl stretching mode region. The same experimental conditions were used for all systems. EMIRS bands were integrated and analysed, using the procedure described in Part 1 (B. Beden, J. Electroanal. Chem., 345 (1993) 1). Characteristic frequencies were located precisely, allowing the spectral discrimination of several types of adsorbates. The same procedure was then used to follow the chemisorption of methanol on platinum in perchloric medium with time. As expected, formate species were found to dominate on the two types of platinum surface. However, during the initial stages of chemisorption, and particularly on the Pt(111) electrode, the formation of adsorbed methyl formate is likely. A mechanism is suggested, taking into consideration the possibility of surface reactions between adsorbates.