The oxidation of CO by Au/Fe2O3 and Au/ZnO catalysts is compared in the very early stages of the reaction using a temporal analysis of products (TAP) reactor. For Au/Fe2O3 pre-dosing the catalyst with 18O labelled water gives an unexpected evolution order for the labelled CO2 product with the C18O2 emerging first, whereas no temporal differentiation is found for Au/ZnO. High pressure XPS experiments are then used to show that CO bond cleavage does occur for model catalysts consisting of Au particles deposited on iron oxide films but not when deposited on ZnO films. DFT calculations, show that this observation requires carbon monoxide to dissociate in such a way that cleavage of the CO bond occurs along with dynamically co-adsorbed oxygen so that the overall process of Au oxidation and CO dissociation is energetically favourable. Our results show that for Au/Fe2O3 there is a pathway for CO oxidation that involves atomic C and O surface species which operates along side the bicarbonate mechanism that is widely discussed in the literature. However, this minor pathway is absent for Au/ZnO.

A Raman investigation has been carried out on samples of ion irradiated highly-oriented pyrolytic graphite (HOPG). Irradiation is carried out under ultra-high vacuum (UHV), at room temperature, with 5 keV He+, Ne+, Ar+ and Xe+ ions so as to create a damaged layer, with the doses administered being higher than those previously reported. Modern Monte Carlo simulations (SRIM 2008) are utilised to provide an insight into the ion–graphite interactions, and the effects of varying ion penetration depths are considered when analysing the observed damage.

The interaction of nitric oxide, nitrogen dioxide and nitrous oxide with a polycrystalline uranium surface has been investigated at 298 K. The surface composition and electronic structure of the developing oxide films were studied using X-ray and ultraviolet photoelectron spectroscopy. Nitrous oxide adsorbs dissociatively leaving only oxygen adsorbed on the uranium surface. Nitric oxide and nitrogen dioxide also adsorb dissociatively but in these cases both oxygen and nitrogen remain on the surface. We propose the formation of uranium oxynitride (UOxNy). For exposures >350 L the rate of reaction of NO with the oxynitride surface decreases significantly. In contrast, NO2 continues to react with the surface and a further increase in surface oxygen concentration is observed.

The adsorption of cyanogen on clean and oxygen pre-treated graphite supported copper films, and a polycrystalline copper surface, and the co-adsorption of cyanogen and oxygen on graphite supported copper films, and a polycrystalline copper surface has been studied using X-ray photoelectron spectroscopy. Cyanogen dissociates on the copper surfaces at 300 K, yielding an adsorbed cyano group, CN(a). On the oxygen pre-treated copper surface cyanogen reacts quantitatively with the adsorbed oxygen at 300 K to form a surface cyanate species, NCO. On annealing to 600 K this species decomposes, leaving only N adatoms and residual adsorbed CN on the surface. The co-adsorption of cyanogen and oxygen from a cyanogen–oxygen mixture enhances the formation of NCO to the extent that all available surface oxygen is consumed to form NCO on annealing at 450 K. In the absence of available atomic surface oxygen NCO does not decompose at temperatures up to 600 K. NCO and NCO2 are shown to be the intermediates in the oxidation of cyanogen on copper films and a polycrystalline copper foil.

The effect of alkali metals on the thermal, photon and electron induced chemistry of nitric oxide at metal oxide surfaces is investigated, using XPS, TPD and IRAS. Alkali nitrosyl salts are observed on both NiO(1 1 1) and Cr2O3(0 0 0 1) surfaces, with evidence in the latter case for the presence of a hyponitrite species. Nitrite species are only formed via photon or electron induced reactions.

The adsorption of cyanogen, (CN)2, on graphite and graphite-supported copper films has been investigated using X-ray photoelectron spectroscopy. X-ray irradiation is shown to effect a polymerisation of condensed cyanogen overlayers on both graphite and graphite supported copper film surfaces via a substrate-mediated secondary electron process.

The interaction of lithium, sodium and potassium with an oxidised Ni(110) single crystal surface has been investigated using X-ray photoelectron spectroscopy (XPS). Incorporation of the alkali metal into the oxide layer at room temperature results in the suppression of the intrinsic Ni(2p) satellite structure of stoichiometric NiO, confirming its origin in an inter-site screening process in accordance with a recent theoretical model. In addition, the reaction of the alkali metal with NiO at higher temperatures gives rise to a divalent or trivalent nickelate species. The effect of water vapour on nickelate formation and the reactivity of the nickelate to carbon monoxide is also investigated.

The oxidation of CO by Au/Fe2O3 and Au/ZnO catalysts is compared in the very early stages of the reaction using a temporal analysis of products (TAP) reactor. For Au/Fe2O3 pre-dosing the catalyst with 18O labelled water gives an unexpected evolution order for the labelled CO2 product with the C18O2 emerging first, whereas no temporal differentiation is found for Au/ZnO. High pressure XPS experiments are then used to show that CO bond cleavage does occur for model catalysts consisting of Au particles deposited on iron oxide films but not when deposited on ZnO films. DFT calculations, show that this observation requires carbon monoxide to dissociate in such a way that cleavage of the CO bond occurs along with dynamically co-adsorbed oxygen so that the overall process of Au oxidation and CO dissociation is energetically favourable. Our results show that for Au/Fe2O3 there is a pathway for CO oxidation that involves atomic C and O surface species which operates along side the bicarbonate mechanism that is widely discussed in the literature. However, this minor pathway is absent for Au/ZnO.