THEORETICAL EXPLANATION OF THE HYDROGEN WAVE ON A PLATINUM SINGLE-CRYSTAL ELECTRODE

Voltammograms observed on basal planes of a Pt single crystal electrod e in 0.1 M HClO4 were analyzed theoretically. Adsorbed hydrogen atoms were assumed to form 2-dimensional (111), (100), and (110) lattices. T hese lattices were treated by applying the Huckel method to an element ary domain consisting of 400x200 lattice points with periodic boundary conditions. Results explained the essential aspects of the butterfly at Pt(111) and the hydrogen waves at Pt(100) and Pt(110). The lateral interactions of the adsorbed hydrogen atoms were attractive in all cas es and their values were estimated. The value at Pt(110) reproduced th e previous one derived from the adsorption isotherm analysis. The squa re-shaped wave observed at Pt(111) in a potential range of 0.05-0.35 V was explained by an entirely different model for a freely moving part icle. The analysis suggested that the square wave is due to electrons which move freely in the adsorption layer. The Huckel method was furth er applied to S-dimensional lattices having 2 to 3 layers. Results sug gested a striking effect of the absorbed hydrogen beneath the surface on the hydrogen wave.