INTERACTIONS OF ADSORBED ORGANIC LAYERS WITH HYDROGEN ATOMS ON PLATINUM ELECTRODES.
Abstract
Coverages of smooth Pt foils with H-atoms in presence of CO and 'reduced CO2' were investigated in 1 M H2SO4 at 40C. Compared with H-H interactions, H-CO interactions are repulsive above 0.15 V vs. R.H.E. When Theta-CO is expressed in terms of adsorbed CO molecules, there is apparently no net interaction for potentials < or = 0.15 V. When Theta-CO is expressed in terms of sites occupied, the H-CO interaction is repulsive at all potentials. The H-'CO2' interaction is repulsive above 0.20 V but attractive below this potential. The data suggest that the 'uniform heterogeneity' model of H-adsorption on Pt is inadequate and that there are at least two distinct kinds of H-atom sites. Within these adsorption regions, the 'heterogeneity' cannot be explained solely on the basis of an a priori site energy distribution; on type II ('strongly bonding') H-sites, the observations are consistent with 'induced' heterogeneity. The H-'CO2' interaction at high hydrogen coverages must result from lateral interactions; probably hydrogen-bond formation. Because of these interactions, H-atom charging methods of estimating organic coverage on Pt must be used with caution. The cathodic method is least suspect. Although 'conventional' electrochemical techniques show them to be identical, their interactions with H-atoms prove CO-ads and 'reduced CO2' to be different species. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1968
- Accession Number
- AD0663903
Entities
People
- Kathleen Cahill
- S. B. Brummer