Interaction of gaseous H atoms with Cu(100) surfaces: adsorption, absorption, and abstraction

Reactions of gas-phase H atoms with atomically and molecularly adsorbed oxygen on Pt(111)

“…24 The cleanness was verified by hydrogen and oxygen TPD spectra. 16 O 2 ͑Messer Griesheim, 99.998%͒, 18 O 2 ͑Promochem, 95%͒, and H 2 18 O ͑Aldrich, 95%͒ were adsorbed by either backfilling the main chamber through a leak valve or by using a capillary doser to reduce the gas load to the chamber. The exposures indicated in this paper were calculated from uncorrected ion gauge readings ͑1 L ϭ10 Ϫ6 Torr s͒.…”

“…The first reaction step, the hydrogenation of oxygen adatoms, H(g)ϩO(a)→OH(a), has been shown to be the rate limiting reaction step of the water formation on Ru͑001͒, 13,14 Ir͑111͒, 15 Ni͑100͒, 16 and Cu͑111͒, 17 whereas the hydrogenation of the intermediate hydroxyl ͑OH͒ hydroxyl was found to be rate limiting on Cu͑100͒. 18 Several investigations of the interaction of gas-phase H atoms with chemisorbed oxygen molecules on Pt͑111͒ have been reported. [10][11][12] Kim ciation of chemisorbed O 2 via the transition state HO 2 , H(g)ϩO 2 (a)→HO(a)ϩO(a), followed by further hydrogenation of adsorbed atomic oxygen and hydroxyl.…”

“…[11][12][13][14][15][16][17][18] Generally, it was observed that oxygen ada-toms are readily hydrogenated by gas-phase H atoms via two consecutive reaction steps to water, even if the metal surface does not catalyze the LH reaction between coadsorbed hydrogen and oxygen. Therefore, the reaction seems to proceed via a ''direct'' interaction between impinging hydrogen atoms and oxygen adatoms.…”

“…The reactions of gas-phase hydrogen atoms with adsorbed atomic [12][13][14][15][16][17][18] and molecular oxygen 10-12 discussed above were explained without exception by operation of an Eley-Rideal ͑ER͒ mechanism, i.e., a direct reaction between incident hydrogen atoms and adsorbed species. However, recent experimental data [19][20][21] and quantum mechanical calculations 22 suggest that hot-atom ͑HA͒ processes dominate in the presence of a deep adsorption well for incident hydrogen atoms, e.g., on metallic substrates.…”

Communication: Hot-atom abstraction dynamics of hydrogen from tungsten surfaces: The role of surface structure

“…Large effects are also experimentally and theoretically observed in the initial sticking probability of N 2 on tungsten surfaces [7][8][9][10] and O 2 on the three low-index crystal faces of silver. [11][12][13][14][15][16][17] Molecular recombination is also affected by the crystal face as revealed, for instance, by the experiments on hydrogen formation at metals carried out by Küppers et al [18][19][20][21][22][23][24][25] and Winkler et al [26][27][28][29] The observed kinetics for H(D)+D(H)/metal recombination has been rationalized via models that required a significant variation of the rate constants for H 2 , HD, and D 2 formations for the three low-index faces of Pt [19][20][21][22] and also for Cu(111) and Cu(100). 23,24 On the sub-picosecond time scale, recombinations proceed via Eley-Rideal (ER) or Hot-Atom (HA) abstractions.…”