A SNIFTERS STUDY OF THE DIFFUSE DOUBLE-LAYER AT SINGLE-CRYSTAL PLATINUM-ELECTRODES IN ACETONITRILE

In situ reflection infrared spectroscopy with electrochemical modulati on has been used to investigate the structure of the double layer for the system: Pt(hkl)/acetonitrile. The electrolytes used were tetraethy lammonium perchlorate and sodium perchlorate. It has been found that a cetonitrile is preferentially chemisorbed on the surface either throug h the non-bonding electrons on the nitrogen atom at potentials positiv e of the point of zero charge, or on its side in a rehybridized form a t negative potentials. The transition between these orientations can b e followed by the present technique. The experiments were also used to study the accumulation of solvated cations in the double layer. The s pectroscopic data are discussed with respect to the orientation of the solvent and location of the electrolyte ions in the double layer.