A structural effect in direct reactions: Kinetics of D abstraction from Pt(110) 1 x 2 surfaces with gaseous H atoms

Deuterium-covered Pt(110) surfaces were subjected to a flux of thermal H atoms at 100K. The rates of product formation, HD and D-2, were measured simultaneously with H atom exposure as a function of D coverage. D-2 as a product and the kinetics of HD formation contradict the operation of Eley-Rideal type mechanisms in these reactions. More appropriate seems the assumption that a hot-atom type mechanism operates in abstraction of adsorbed D by gaseous H. The H/D abstraction kinetics at Pt(110) surfaces are completely different from that observed previously at Pt(111) surfaces. This structural effect puts a further question mark on the validity of the Eley-Rideal mechanisms in abstraction reactions and is interpreted in the present work as a consequence of the interrelation between a hot-atom mechanism and the surface structure of the reconstructed substrate. (C) 1998 Elsevier Science B.V.