Accession Number : AD0663903

Title :   INTERACTIONS OF ADSORBED ORGANIC LAYERS WITH HYDROGEN ATOMS ON PLATINUM ELECTRODES.

Descriptive Note : Interim technical rept.,

Corporate Author : TYCO LABS INC WALTHAM MASS

Personal Author(s) : Brummer,S. B. ; Cahill,Kathleen

Report Date : JAN 1968

Pagination or Media Count : 31

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)

Descriptors :   (*PLATINUM, *ELECTROCHEMISTRY), ORGANIC COMPOUNDS, FILMS, ELECTRODES, HYDROGEN, CARBON MONOXIDE, ADSORPTION

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE