Eley–Rideal reactions between H atoms on metal and graphite surfaces: The variation of reactivity with substrate

Results are presented for the reaction of gas-phase H atoms with H atoms adsorbed onto a variety of substrates. Time-dependent quantum methods are used to compute reaction cross sections and product H2 rotational and vibrational distributions for a large number of model potential energy surfaces. The potentials which model reactions on metals exhibit a wide range of reactivity. In addition, the single-collision Eley–Rideal reaction cross sections are generally small, suggesting that hot-atom processes should in general play an important role in H2 formation on metal surfaces. These observations are consistent with recent experiments. Eley–Rideal reactivity is shown to increase as the strength of the H-substrate bond decreases, and H atom trapping becomes less favorable. The cross sections for the reaction of H(g) with H adsorbed onto model graphite surfaces are generally large (5–10 Å2).