Journal Articles (before-1995)
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Item Sorption of Hydrogen by Palladium and Palladium/Silver Alloy Wires(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Couper, Aitken; John, Christopher S.Heats of adsorption q{8), sticking probabilities and temperature programmed desorption spectra are reported for the adsorption of H2 onto clean wire surfaces of Pd, all as functions of coverage 0. Data, principally from temperature programmed desorption, have also been obtained for the inter action of H2 with two Pd/Ag alloys. The low temperature (104 K) sorption properties of Pd were dominated by the occurrence of absorption which limited the applicability of the technique used to determineItem Interaction of diatomic molecules with clean metal wire surfaces. Part 1.—Hydrogen on tungsten(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (06), 1977) Couper, Aitken; John, Christopher S.Heats of adsorption, sticking probabilities and temperature programmed desorption spectra are reported for hydrogen on polycrystalline tungsten at 88 and 290 K. The heats were measured using a fine-wire calorimeter, as invented by J. K. Roberts, but with automatic recording. The initial heat of adsorption onto a clean surface at 290 K was 192 ± 8 kJ mol–1. Three desorption peaks were observed in the range 290–700 K. A discussion of the results is presented in terms of the crystal planes believed to be present at this polycrystalline surface. It is deduced that the heat of adsorption for hydrogen onto the (100) and (110) planes is 137 ± 5 kJ mol–1 and that on these planes there is a repulsive interaction energy between near neighbours of 5.25 ± 0.50 kJ (mol pair)–1. The importance of adatom interaction in this system is emphasised.Item Different Species of Hydrogen Chemisorbed on Raney Nickel Studied by Neutron Inelastic Spectroscopy(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (1), 1977) Renouprez, A. J.; Fouilloux, P.; Coudurier, G.The chemisorption of hydrogen on Raney nickel has been studied by neutron inelastic spectroscopy at high energy transfer. The main vibration levels at 120 and 140 meV are interpreted as being produced by multi-bonded surface species. A weak band also appears around 280 meV, superposed on the harmonic of the 140 meV peak, which can be attributed to the vibration of a linear form Ni—H. This interpretation is supported by the optical spectra of transition metal hydrides of known structure.Item Surface Potential of Hydrogen Adsorbed on Nickel Films and its Dependence on Film Structure(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Dus, RSurface potential changes which take place when hydrogen is adsorbed on nickel films have been measured using the static capacitor technique. By variation of the temperature of deposition of the film, and of the temperature of subsequent adsorption of hydrogen, three different adsorbed species have been identified: a negative adatom β–1, a positive pseudo-hydride species β+2 and a positive molecularly adsorbed species α. Conditions favourable to the formation of the β+2 species are discussed. Surface potential measurements for hydrogen adsorption on Pd and Nb (which easily form hydrides) and on Fe (which does not form a hydride) are consistent with the pseudo-hydride character of the β+2 species.Item Reactions of the O Negative Ion with Hydrogen and the Lower Hydrocarbons(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (4), 1972) Parkes, David A.The reactions between O–, formed by dissociative attachment to oxygen, and H2, D2, CH4, C2H6, C2H4 and C2H2 have been studied using a drift tube and mass filter. Gas densities ranged over a factor of five about 1017 molecule cm–3 and reduced fields were of the order of 3 × 10–16 V cm2 molecule–1. The reaction with the alkanes gave a single pair of products R + OH–, but the remainder produced both negative ions and free electrons. The following rate constants were measured and with the minor exception of OH– production from C2H4 were found to be substantially independent of the reduced field. [graphic omitted] The reaction with C2H4 also produced OH–, C2H–, C2OH– and C2H3O– at rates of 0.5 to 10, 5, 1.5 and 2 % respectively of the combined rate of the two major channels. The upper limits for the rates of the reactions of O–3 with the same molecules were two orders of magnitude lower.Item Electronegativity, Work Function, and Heat of Adsorption of Hydrogen on Metals(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (2), 1972) Trasatti, SA new list of work functions for polycrystallinc metal surfaces is proposed and correlated with Pauling’s electronegativity. Simple linear relationships exist between the above two quantities, which divide metals into four groups, roughly: sp, transition, alkali and alkali earth metals. The difference between the electronegativity for atoms in molecules and that for solid metal surfaces is discussed. The use of these work functions in the Eley-Stevenson method for calculating the adsorption heat of hydrogen on metals shows that the ionic contribution to the bond energy is essentially correct, and better agreement with experimental data than in previous calculations is generally obtained if metal-metal bond energies arc derived from surface tension measurements rather than from atomization heats.Item Chemisorption of Hydrogen on Evaporated Copper Films(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (2), 1972) Alexander, C S; Pritchard, JSurface potentials (s.p.) of atomic hydrogen adsorbed at low temperatures on clean copper films show wide variations from one film to another. This is believed to reflect varying proportions of different crystal planes. Initial adsorption with a negative s.p. may be followed by a weaker adsorption with a positive effect. The negative s.p. corresponds to hydrogen which can be in equilibrium with gaseous molecular hydrogen. This spontaneous dissociative chemisorption has been studied between 242 and 337 K at pressures up to 60 Torr, using vibrating capacitor s.p. measurements to follow the equilibrium concentration of adatoms. Isosteric heats (typically 40-50 kJ mol-1) are almost independent of coverage on some films, and a major part of the adsorption can then be described approximately by the Langmuir isotherm for dissociative adsorption.Item Addition of Formaldehyde to Slowly Reacting Hydrogen + Oxygen Mixtures(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (7), 1972) Baldwin, R R; Fuller, A R; Walker, R WThe effect of HCHO in reducing the induction periods of H2+ O2+ N2 mixtures at 500°C has been examined for a range of mixture composition, using HCHO concentrations in the range 0.05–1.0 %. Computer treatment shows that the marked reduction can only be accounted for by the reaction HO2+ HCHO = H2O2+ HCO(24). A detailed computer analysis of the results for a range of mixtures gives the ratio k24/k½10= 23 (mol l.–1 s)–½. Taking k10(HO2+ HO2= H2O2+ O2)= 1.8 × 109 gives k24= 9.6 × 105 l.mol–1 s–1. With A24= 109, this corresponds to E24= 10.7 kcal mol–1.