Abstraction of D adsorbed on Pt(111) surfaces with gaseous H atoms

Abstract

The impact of gaseous H atoms at D covered Pt(111) surfaces at 85 K leads to the formation of gaseous HD and D2 products. The kinetics of formation of these products was measured simultaneously with H exposure for different initial D coverages. The HD and D2 rates as a function of H fluence from the reaction start exhibit common characteristics; a rate step, a rate maximum, and a subsequent exponential rate decay. The HD and D2 rate steps were observed not to scale linear with the D coverage and to increase if on D covered surfaces H was coadsorbed prior to reaction. Of the observed phenomena, only the exponential decay of the HD rate is in line with expectations if an Eley–Rideal mechanism acts in the present reaction. D2 formation, the HD rate step as a function of D coverage, and the presence of a H coadsorbate contradict the Eley–Rideal picture. The results suggest that the reactions towards HD and D2 proceed via hot atom type mechanisms.