Browsing by Author "Eley, Daniel D."

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Hydrogen Sorption by Palladium-Gold Wires
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Eley, Daniel D.; Pearson, Edward J.
    Hydrogen sorption was studied on PdAu wires carefully cleaned in ultra high vacuum, at a hydrogen pressure of 6.25 µPa and wire temperatures of 100, 150, 200 and 304 K. For Pd at 100 K the initial sticking coefficient was 0.16, falling to 0.006 at a fractional monolayer coverage θ= 0.8. Sorption against time curves at 100 K for hydrogen continued smoothly to coverages θ > 3.0. Deuterium for the same collision number (pD2=√2pH2) gave a similar rate up to θ∼ 1.0 when the uptake became slower. Temperature programmed desorption gave one peak and desorption activation energies, which extrapolated to a θ= 0 value of 100 kJ mol–1 for Pd, 90Pd10Au and 70Pd30Au and 45 kJ mol–1 for 55.2Pd44.8Au. These activation energies decreased sharply with coverage, to a value for the three Pd rich alloys of ∼20 kJ mol–1, comparable with the heat of solution. Hydrogen sorptions for a given exposure increased slightly from Pd to 90Pd10Au, decreasing sharply towards zero at 40Pd60Au, where the holes in the d band have disappeared. The results are discussed critically in relation to earlier data, and a tentative model advanced involving (mainly)β chemisorbed H (on Pd atoms, immobile at 100 K), α chemisorbed H2(weakly held on octahedral holes in 100 planes) and dissolved H atoms under the surface. Although it is concluded that holes in the d band are necessary for strongly chemisorbed β-H, a role for PdnAum surface ensembles cannot be ruled out.
  • No Thumbnail Available
    Item
    Infra-red Study of the Reactions between Ethyl Isocyanate and the Surface of Magnesium Oxide
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Eley, Daniel D.; Kiwanuka, Gerald M.; Rochester, Colin H.
    Ethyl isocyanate reacts at 306 K with isolated hydroxyl groups on the surface of magnesium oxide to form a urethane. The adsorption reaction is reversed by evacuation at high temperatures. Adjacent interacting hydroxyl groups and molecular water on magnesium oxide react with ethyl isocyanate to give 1,3-diethylurea which is adsorbed on the oxide as a perturbed “carboxylate-type complex” and carbon dioxide which with water gives a surface bicarbonate species. The 1,3-diethylurea complex decomposes to surface ethyl magnesium carbonate on evacuation at elevated temperatures. The latter species is also formed when ethyl isocyanate reacts with the surface of magnesium oxide at 673 K. Other products of the high temperature reaction include cyanide and isocyanate groups as ligands of surface magnesium ions, adsorbed carbonate ions, and products of the polymerization reactions of ethyl isocyanate, isocyanic acid, and hydrogen cyanide.