The role of sticking and reaction probabilities in hot-atom mediated abstraction reactions of D on metal surfaces by gaseous H atoms

Recent experiments on the abstraction of D adsorbed on metal surfaces with gaseous hydrogen atoms revealed a kinetics of HD formation which is not compatible with the operation of Eley–Rideal (ER) mechanisms. Furthermore, homonuclear products were observed during abstraction, which are not expected through an ER reaction scheme. It was therefore suggested that hot-atom (HA) mechanisms are more appropriate to explain the measured kinetics and products. Random walk calculations of the abstraction kinetics are presented based on a model which exclusively relies on elementary reaction steps which are HA mediated processes. Within this model, the ratio of two variables, the probabilities for hot-atom sticking at empty sites ps and hot-atom reaction with adsorbed species pr, was found to control the kinetics of HD and D2 formation. The essential features of measured kinetic data at Ni(100), Pt(111), and Cu(111) surfaces were reproduced by simple and reasonable assumptions on ps/pr.