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  • 1. Amandusson, H.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dannetun, Helen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Alcohol dehydrogenation over Pd versus PdAg membranes2001In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 217, no 1-2, p. 157-164Article in journal (Refereed)
    Abstract [en]

    The dehydrogenation of methanol and ethanol and the subsequent permeation of hydrogen through Pd and Pd70Ag30 membranes, respectively, have been studied. In order to keep a continuous hydrogen permeation rate, oxygen needs to be added to the alcohol supply. Without oxygen, the decomposition products will form a contaminating layer on the upstream membrane surface. The extraction of hydrogen from ethanol is six times more effective through a Pd70Ag30 membrane than through a pure Pd membrane (at optimum conditions). For methanol, the hydrogen permeation is 30% larger through a Pd70Ag30 membrane than through a membrane of pure Pd. The increased hydrogen permeation yield through Pd70Ag30 compared to Pd can be attributed mainly to a lower upstream consumption of hydrogen due to water formation, but also to an increased conversion of the alcohol in the presence of oxygen. © 2001 Elsevier Science B.V.

  • 2. Amandusson, H.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dannetun, Helen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Effect of CO and O2 on hydrogen permeation through a palladium membrane2000In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 153, no 4, p. 259-267Article in journal (Refereed)
    Abstract [en]

    Hydrogen permeation through a 25-µm thick palladium membrane during continuous exposures of hydrogen together with different combinations of oxygen and carbon monoxide has been studied at membrane temperatures of 100 °C-250 °C (total pressures of 40-150 Torr). Both CO and O2, individually, inhibit hydrogen permeation through the membrane. The cause of the inhibition is, however, somewhat different. CO blocks available hydrogen dissociation sites, while oxygen both blocks dissociation sites and also consumes adsorbed hydrogen through the production of water. When a combination of CO and O2 is supplied together with hydrogen, new reaction pathways will emerge. The carbon dioxide formation will dominate the water forming reaction, and consequently, the blocking effect caused by the formation of water will be suppressed. In a mixture of CO+O2+H2, the hydrogen permeation can become either larger or smaller than that due to only O2+H2 or CO+H2 depending on the CO/O2 ratio. It is thus possible to find a situation where carbon monoxide and oxygen react to form CO2 leaving adsorbed hydrogen free to permeate the membrane.

  • 3. Amandusson, H.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dannetun, Helen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Hydrogen permeation through surface modified Pd and PdAg membranes2001In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 193, no 1, p. 35-47Article in journal (Refereed)
    Abstract [en]

    The hydrogen permeation through surface modified Pd and Pd70Ag30 membranes has been studied at temperatures between 100 and 350°C. Silver has been evaporated on Pd and Pd70Ag30 foils with a thickness of 25µm in order to study the role of the surface composition in comparison with the membrane bulk composition. The Pd70Ag30-based membranes display the largest permeation rates at temperatures below 200°C, while Pd membranes with 20Å silver evaporated on the upstream side show the largest permeation rates above 200°C. There are, consequently, different rate limiting processes above and below 200°C: at temperatures below 200°C, the bulk diffusion through the membrane is rate limiting, while at temperatures above 200°C, the influence of the surface composition starts to become significant. It has further been concluded that a sharp silver concentration gradient from the surface to the bulk is important for the hydrogen permeation rate at temperatures above 200°C. Adding oxygen to the hydrogen supply will almost totally inhibit the hydrogen permeation rate when a pure Pd membrane surface is facing the upstream side, while for silver-containing surfaces the presence of oxygen has almost no effect. On a clean Pd surface, oxygen effectively consumes adsorbed hydrogen in a water forming reaction. With Ag on the surface, no water formation is detected. Co-supplied CO inhibits the permeation of hydrogen in a similar manner on all studied membrane surfaces, independent of surface silver content. © 2001 Elsevier Science B.V. All rights reserved.

  • 4. Amandusson, H.
    et al.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Dannetun, Helen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Isotopic study of ethanol dehydrogenation over a palladium membrane2000In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 195, no 2, p. 376-382Article in journal (Refereed)
    Abstract [en]

    The dehydrogenation of ethanol and the subsequent permeation were studied on a Pd membrane in a continuous ethanol supply. Hydrogen could not be extracted as efficiently from ethanol as from methanol. In ethanol, at least four of the six hydrogen atoms were not available for permeation because of methane formation. Hydrogens bonded to a carbon atom in a C-O group were available for permeation, while hydrogen atoms bonded to a carbon atom without oxygen were not. The efficiency of hydrogen permeation from ethanol was 5% compared to that of pure hydrogen, which could be compared to 25% for methanol compared to pure hydrogen. The hydrogen permeation could be enhanced by adding CO to the EtOH + O2 supply. The permeation probability of the hydrogen bonded to the methylene hydrogen increased while the water formation with this hydrogen atom decreased. Acetic acid was formed upstream when oxygen was in excess. The differently bonded hydrogen atoms in an ethanol molecule experienced different reaction pathways. The results did not contradict the models made from surface experiments in ultrahigh vacuum by Davis and Barteau, Holroyd and Bowker, or Bowker et al.

  • 5.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hydrogen extraction from methanol over a palladium membrane1997Conference paper (Refereed)
  • 6.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hydrogen permeation through modified palladium and palladium-silver2000Conference paper (Refereed)
  • 7.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hydrogen permeation through surface modified Pd and PdAg membranes and the effect of co-supplied O2 and CO2000Conference paper (Refereed)
  • 8.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Identification of Pd membrane permeated hydrogen from ethanol1999Conference paper (Refereed)
  • 9.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Influence of carbon monoxide and oxygen on hydrogen permeation through a palladium membrane -and its effect on dehydrogenation of methanol and ethanol1999Conference paper (Refereed)
  • 10.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Jämförelse av alkohol-dehydrogenering över palladium respektive palladium-silver membran2000Conference paper (Other academic)
  • 11.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Methanol induced hydrogen permeation through a Pd membrane1999In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 442, no 2, p. 199-205Article in journal (Refereed)
    Abstract [en]

    The dehydrogenation of methanol and the subsequent permeation of hydrogen through a 25 μm thick palladium film has been studied in a catalytic membrane reactor. At the temperature studied, 350°C, the decomposition pathway for methanol on clean palladium surfaces is believed to lead to Had and a carbonaceous overlayer. The released hydrogen can either desorb or permeate the palladium membrane. During a continuous supply of methanol hydrogen permeation is reduced and, eventually, totally quenched by the growing carbon monoxide/carbon coverage. Adding oxygen in the methanol supply can balance the increasing carbonaceous coverage through the production of carbon dioxide. In such a case, it is concluded that no CO bond scission occurs. The methanol/oxygen ratio is crucial for the hydrogen permeation rate. Isotope-labelled methanol, CH3OH, CH3OD, CD3OH and CD3OD, shows that it is preferentially the methyl (or methoxy) hydrogen that permeates the membrane.

  • 12.
    Amandusson, Helena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Permeation of methyl hydrogen in isotopically labelled methanol through palladium membranes1998Conference paper (Refereed)
  • 13.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Dehydrogenation of acetylene and ethylene studied on clean and oxygen covered palladium surfaces1986In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 173, p. 148-Article in journal (Refereed)
    Abstract [en]

    The interaction of acetylene and ethylene with a clean and oxygen covered Pd surface has been studied at a temperature of 473 K. The measurements were performed on a hydrogen sensitive Pd-MOS structure making it possible to obtain direct information on the dissociation of both hydrogen and oxygen containing species on a palladium surface. Desorption studies were also performed as well as ultraviolet photoelectron spectroscopy and work function measurements. The studies show that both acetylene and ethylene adsorb dissociatively at this temperature leaving mainly carbon on the surface. When an oxygen covered Pd surface is exposed to C2H2 or C2H4 carbon dioxide and water will be formed and desorb until the surface is oxygen free. In the case of acetylene the presence of preadsorbed oxygen does not block or prevent the C2H2 dissociation on the surface. For C2H4, a large preadsorbed oxygen coverage ( 0.45) will have an impeding effect on the dissociation. The CO2 desorption is oxygen coverage dependent contrary to the H2O desorption. This is due to the fact that hydrogen has a large lateral mobility on the surface while carbon has not. Both the CO2 and H2O reactions are, however, due to the same type of mechanisms.

  • 14.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dehydrogenation rate of some unsaturated hydrocarbons on clean and oxygen covered palladium1987Conference paper (Refereed)
  • 15.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Detection of hydrogen from the photodissociative splitting of water through hydrogen-oxygen separation over a thin Pd film1991In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 70, p. 453-Article in journal (Refereed)
    Abstract [en]

    The photodissociative splitting of water has been studied in gas phase on a plane solid surface. A hydrogen sensitive Pd‐metal‐oxide‐semiconductor (MOS) structure was coated with 1–2 nm TiOx and exposed to water vapor and ultraviolet light. A natural separation of the produced hydrogen and oxygen occurs over the Pd film of the structure and the produced hydrogen is monitored by the electric behavior of the MOS device. The results suggest that suitably treated thin Pd membranes may be of interest for studying the continuous photodissociation of water.

  • 16.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Hydrocarbon dissociation on palladium studied with a hydrogen sensitive MOS structure1988In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 63, p. 207-Article in journal (Refereed)
    Abstract [en]

    The polycrystalline Pd surface of a hydrogen sensitive palladium‐silicon dioxide‐silicon [Pd‐MOS (metal‐oxide‐semiconductor)] structure has been exposed to small unsaturated hydrocarbons in the temperature range 300–500 K. Apart from the hydrogen response of the Pd‐MOS structure also work function (ΔΦ) and electron energy‐loss studies were performed. At 500 K the hydrocarbons dissociate completely upon adsorption and produce a surface with atomically adsorbed carbon. The Pd‐MOS structure can be used to observe both the dehydrogenation of the hydrocarbon molecules and the process of carbon adsorbing on the palladium surface. The sticking coefficient at this temperature for all hydrocarbons is close to unity. Furthermore, the hydrogen sensitivity of the structure is not drastically reduced by the adsorbed carbon. If the hydrocarbon adsorption is performed at 300 K there is still, at least on the initially clean surface, a large dehydrogenation. The dissociation is, however, not at all complete and there are considerable amounts of hydrocarbon species adsorbed for each gas. The induced work function shifts due to the different hydrocarbons vary from -1.0 to -1.7 eV. The hydrogen sensitivity of the Pd‐MOS structure is reduced for growing hydrocarbon coverages and disappears completely for work function shifts of -1.7 eV.

  • 17.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Reactions between hydrocarbon and an oxygen covered palladium surface1988In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 193, p. 109-Article in journal (Refereed)
    Abstract [en]

    Isothermic desorption studies where an oxygen covered polycrystalline Pd surface (T = 325–575 K) is exposed to small unsaturated hydrocarbons have been performed. The studied gases were acetylene, propene, propadiene, propyne, butene, butadiene, butyne, and also for comparison hydrogen. Electron energy loss spectroscopy (EELS) was available for adsorbate studies and a hydrogen sensitive Pd-MOS structure was used as a sample. The temperature limit for total dissociation is observed to decrease slightly for an oxygen covered surface compared to the clean surface. On an oxygen covered surface the dissociation is complete above 400 K and the reaction products are H2O, CO2, and adsorbed C. Varying the adsorption temperature, the carbon dioxide production is not detectable at room temperature, where all carbon is adsorbed and only water is formed, but increases to reach a constant level above 475 K. For temperatures above 400 K the licking coefficient is close to unity and there is no blocking due to preadsorbed oxygen (as there is for H2). Both the water and carbon dioxide formations are of Langmuir-Hinshelwood type but while the H2O desorption rate is found to depend only on impinging hydrocarbon flux the CO2 desorption rate depends also on the oxygen coverage.

  • 18.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    The relative ionization gauge sensitivity of some unsaturated hydrocarbons1987In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 29, p. 331-Article in journal (Refereed)
    Abstract [en]

    By studying the water desorption rate from an oxygen covered Pd surface which is exposed to some unsaturated hydrocarbons (and hydrogen) the relative ionization gauge sensitivity of the hydrocarbons: acetylene, ethylene, propene, 1- and 2-butene, propadiene, 1,3-butadiene, propyne and butyne has been determined.

  • 19.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    NO dissociation on polycrystalline Pd studied with a Pd-metal-oxide-semiconductor (Pd-MOS) structure1989In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 66, p. 1397-Article in journal (Refereed)
    Abstract [en]

    The dissociation probability of NO when adsorbed on polycrystalline Pd as a function of temperature (323–523 K) has been studied with a Pd‐metal‐oxide‐semiconductor (Pd‐MOS) structure. For comparison the same experiments were also carried out with O2, which adsorbs dissociatively in the whole temperature region, and with CO, which adsorbs molecularly. It was found that the Pd‐MOS structure can be used as a very sensitive sensor for NO dissociation and that dissociation of NO starts to be significant at temperatures around 400 K. The results are also compared with electron‐energy‐loss spectroscopy, ultraviolet photoemission spectroscopy, work‐function, and desorption studies.

  • 20.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Photodissociative splitting of water on surface modified metal-oxide-semiconductor (MOS) structures1990Conference paper (Refereed)
  • 21.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Unsaturated hydrocarbons on palladium1987Conference paper (Refereed)
  • 22.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Söderberg, D.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    A hydrogen-sensitive Pd-MOS structure working over a wide pressure range1984In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 17, p. 259-Article in journal (Refereed)
    Abstract [en]

    A Pd-MOS structure has been developed which has proven to be sensitive to hydrogen both in air at atmospheric pressures and in UHV. The ability to work over a wide pressure range makes it an interesting component in, e.g., the study of catalytic reactions involving hydrogen on metal surfaces. Here we demonstrate the hydrogen sensitivity of such a structure over a pressure range of 5x10-11 to 2 Torr.

  • 23.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Söderberg, Dennis
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University. Linköping University, The Institute of Technology.
    The H2-O2 reaction on palladium studied over a large pressure range1984Conference paper (Refereed)
  • 24.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Söderberg, Dennis
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, L.-G.
    The H2-O2 reaction on palladium studied over a large pressure range: Independence of the microscopic sticking coefficients on surface condition1985In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 152/153, p. 559-Article in journal (Refereed)
    Abstract [en]

    We have studied the H2---O2 reaction on Pd over a large pressure range by letting the reaction take place on the Pd gate of a Pd-MOS structure. By measuring shifts in the capacitance versus voltage (C(V)) curve of the structure, the variation of the “free” hydrogen atom concentration can be monitored during the reaction. By combining these results with surface potential measurements and with photoelectron spectroscopy, we find a critical ratio of 0.4 where the surface turns from being oxygen dominated to being hydrogen dominated. The critical ratio is independent of the absolute pressures and of surface condition and shows no significant temperature dependence in the temperature range 50–200°C. This implies that hydrogen and oxygen have similar sticking coefficients at both clean and technical Pd surfaces. The conclusion is drawn that hydrogen (and oxygen) dissociation on Pd is a property of the Pd atom or cluster of Pd atoms and is not critically dependent on any long-range order parameter such as the surface electronic density of states.

  • 25.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Wilzén, L.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    The study of alcohol induced hydrogen permeation in a catalytic membrane reactor1996In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 357, p. 804-808Article in journal (Refereed)
    Abstract [en]

    We have studied dehydrogenation and subsequent permeation of hydrogen from some small alcohols and hydrocarbons over a 20 μm thin Pd membrane at temperatures between 523 and 623 K. It is only for the smaller alcohols that significant amounts of hydrogen permeate the membrane. An addition of oxygen in the alcohol supply is needed to prevent a slow quenching of the permeation. The ratio of oxygen to alcohol is critical. For the right balance between methanol and oxygen permeation is very effective, and comparable to permeation caused by pure hydrogen. Studies of CH3OD and C2H5OD further show that the permeation is dependent on the hydrogen origin, i.e. the methyl and hydroxyl hydrogen have different reaction pathways and permeation probabilities.

  • 26.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wilzén, Lars
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Johansson, M.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hydrogen production from methanol over a palladium membrane1996Conference paper (Refereed)
  • 27.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wilzén, Lars
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Alcohol dehydrogenation by a palladium membrane1995Conference paper (Refereed)
  • 28.
    Dannetun, Helen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wilzén, Lars
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dehydrogenation of alcohols on a palladium membrane1995Conference paper (Refereed)
  • 29. Fogelberg, J.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    A hydrogen sensitive palladium metal-oxide-semiconductor device as sensor for dissociating NO in H2-atmospheres1990In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 41, p. 705-Article in journal (Refereed)
    Abstract [en]

    A Pd-MOS structure can be used as a sensitive analytical tool in the study of dissociating oxygen containing molecules. Nitric oxide has been studied as a test case. Initially NO adsorbs very effectively and dissociatively on polycrystalline Pd at temperatures above 473 K. At this temperature H2O, N2O and N2 desorbs during an NO exposure in a hydrogen background. After such exposure the surface is probably left with only residual nitrogen atoms adsorbed on the surface. Below 390 K the dissociation probability is insignificant.

  • 30.
    Fogelberg, J.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    H2-D2 exchange on an oxygen covered Pd-film: A study of the backreaction on a hydrogen sensitive MOS device1992Conference paper (Refereed)
  • 31. Fogelberg, J.
    et al.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Kinetic modelling of hydrogen ad/absorption in thin films of hydrogen sensitive field effect devices: Observation of large hydrogen induced dipoles at the Pd/SiO2 interface1995In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, ISSN 0021-8979, Vol. 78, p. 988-Article in journal (Refereed)
    Abstract [en]

    A kinetic modeling of the hydrogen interaction with a Pd‐SiO2‐Si (Pd‐MOS) device is reported. The model is fitted to a number of experimental results, mainly from mass spectrometric desorption measurements. The new results verify an older description of the energetics of hydrogen adsorption states at the Pd/SiO2 interface in the sense that the adsorption may be described by a so‐called Temkin isotherm; however, several new findings have to be incorporated into the model in order to obtain a consistent picture. The initial heat of adsorption at the interface is around 0.8 eV/hydrogen atom. The number of adsorption sites at the interface is considerably smaller than at the surface, 6×1017 m−2 versus 1.5×1019 m−2. Furthermore, the interface hydrogen atoms are strongly polarized. An average value of 2 Debye is obtained. It is the large hydrogen polarization at the Pd/SiO2 interface and not a large concentration of adsorbed hydrogen atoms per se which accounts for the very high sensitivity of a Pd‐MOS device as hydrogen sensor

  • 32.
    Fornander, H.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Ekedahl, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    A comparison of the CO and D2 oxidation reactions on Pd supported on MgO(100), MgO(110) and MgO(111)1999In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 440, no 3, p. 375-386Article in journal (Refereed)
    Abstract [en]

    Oxidation of D2 and CO on oxygen pre-exposed 200 nm thick Pd films, epitaxially grown on MgO(100), MgO(110) and MgO(111), has been investigated in the temperature range 100–300°C. Oxygen initial sticking coefficients have been determined to be close to 1 for the 100 and 110 films, and around 0.8 for the 111 film. The sticking coefficient and reactive sticking coefficient for CO oxidation on Pd/MgO(100) is also close to 1, and the maximum reactive sticking coefficient for hydrogen oxidation is determined to be around 0.9 at temperatures above 200°C. It is shown that the reactivities for the different surfaces vary strongly with surface and oxygen coverage, and the consequence of this for supported particle catalysts is pointed out.

  • 33.
    Fornander, H.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Oxidation of carbon monoxide and deuterium on a Pd (100) film1999In: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879X, Vol. 59, p. 107-113Article in journal (Refereed)
    Abstract [en]

    For Pd/MgO(100) pre-exposed to oxygen, the catalytic oxidation of CO and D2, respectively, has been studied in the temperature range 100–300 _C. At temperatures >200 _C, the CO2 desorption rate is independent of oxygen coverage, _O, and the reactive sticking coefficient for CO is close to unity. The D2O desorption rate is strongly dependent on _O. D2 adsorption is blocked by adsorbed oxygen and the maximum D2O desorption rate is reached when almost all oxygen has been consumed (_O < 0:03). The formation of an oxygen c(2 _ 2) structure, coexisting with the initial p(2 _ 2) phase, is reflected in the oxidation rates.

  • 34.
    Fornander, H.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ekedahl, L.-G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Structural effects of supported Pd particles in D2 and CO oxidation experiments1999In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 441, no 2-3, p. 479-492Article in journal (Refereed)
    Abstract [en]

    In the temperature range 100–300°C, isothermic D2 and CO titration experiments have been performed on oxygen pre-exposed 1.5, 4, 20 and 200 nm thick Pd films, epitaxially cube-on-cube grown on MgO(100). The oxygen pre-exposures varied from 0.2 to 150 L. The three thinnest films consisted of faceted particles, mainly bounded by Pd(111) and Pd(100) surfaces, while the 200 nm sample was a continuous, flat Pd(100) film with atomic steps. Atomic force microscopy demonstrated that the titration experiment did not affect the structure of the (large) Pd particles in the 20 nm film. The reaction behavior of the 1.5 nm film can be understood by assuming that the film consists of (111)-bounded Pd particles, where O2 and D2 dissociate and spill over to the oxide support, whereas CO adsorbs and reacts both on the Pd and on the oxide. The CO oxidation thus occurs in parallel on Pd and on MgO, while the D2 oxidation is sequential, first occurring on the Pd and then on the MgO. To explain the D2O desorption curves for the 4 and 20 nm films, spillover to the MgO support as well as reactions on the Pd(111) and Pd(100) facets have to be taken into account. The greater the oxygen pre-exposure, the higher the probability that the D2 molecules dissociate primarily on the Pd(111) surfaces.

  • 35. Nielsen, A.T.
    et al.
    Amandusson, H.
    Bjorklund, R.
    Dannetun, Helen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Ejlertsson, J.
    Ekedahl, Lars-Gunnar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Svensson, Bo
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Hydrogen production from organic waste2001In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 26, no 6, p. 547-550Article in journal (Refereed)
    Abstract [en]

    The extraction of pure hydrogen from the fermentation of household waste by a mixed anaerobic bacterial flora is demonstrated. Simulated household waste (600 g) was fermented in a bioreactor, which was continuously sparged with nitrogen (30 ml/min) fed in from the bottom. The gas stream from the biorector passes through a sulphide trap (ZnO) and then through a heated palladium-silver membrane reactor to separate hydrogen from the gas stream. In this way, waste remediation and biological hydrogen production is combined in a process where a large proportion of the hydrogen produced can be collected, free of other gaseous species from the fermentation. © 2001 International Association for Hydrogen Energy.

  • 36.
    Petersson, L.-G.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Fogelberg, J.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Demonstration of high sticking coefficients for various molecules on palladium1989Conference paper (Refereed)
  • 37.
    Petersson, L.-G.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Fogelberg, J.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Sticking and dissociation of NO on Pd surfaces in H2 atmospheres at low pressures1992Conference paper (Refereed)
  • 38. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Fogelberg, J.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Hydrogen adsorption states at the external and internal palladium surfaces of a Palladium-Silicondioxide-Silicon structure1985In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 58, p. 404-Article in journal (Refereed)
    Abstract [en]

    The hydrogen adsorption states at the external and internal Pd surfaces of a hydrogen sensitive Pd‐SiO2‐Si (Pd‐MOS) structure have been studied in high and ultrahigh vacuum. The steady‐state response of the Pd‐MOS structure (due to the hydrogen present at the Pd‐SiO2 interface) shows a logarithmic dependence on hydrogen pressure, independent of external surface condition. The heat of adsorption of the internal surface is coverage dependent and described by ΔHiH0(1‐aθi) giving ΔH0≊1.4 eV/molecule with a=1. Thus, there are always hydrogen adsorption states available at the internal surface independent of the applied pressure. This is why the Pd‐MOS structure works as a hydrogen sensor over a large pressure range. The importance of a surface cleaning procedure in order to obtain an atomically clean Pd surface after Ar sputtering is pointed out. It is observed that a, probably carbon, contaminated Pd surface has hydrogen adsorption properties similar to those of the palladium‐oxide interface. A clean Pd surface has adsorption sites with smaller heat of adsorptions than those at the interface. Furthermore, these adsorption sites give an increase in work function, whereas a decrease in work function is observed at the interface. It is pointed out that the difference in the heat of adsorption between surface and interface hydrogen adsorption sites means that hydrogen atoms are detected at the interface even when the hydrogen coverage at the clean surface is very small.

  • 39. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Fogelberg, J.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Oxygen as a poison or promoter in the catalytic dissociation of H2, C2H2, C2H4, and NH3 on palladium1986In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 27, p. 275-Article in journal (Refereed)
    Abstract [en]

    The dissociation rates of H2, C2H4, C2H4, and NH3 have been studied on oxygen covered Pd surfaces by measuring the water desorption rates during exposure to each of the molecules. These results are correlated with the hydrogen response of a Pd-MOS structure. The measurements show a trend (at 473 K) where oxygen blocks H2 dissociation, blocks C2H4 dissociation only above a certain oxygen coverage, has no influence on C2H2 dissociation, and promotes NH3 dissociation.

  • 40. Petersson, L-G
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Karlsson, S.-E.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Hydrogen dissociation on clean and contaminated Pd studied with a Pd-MOS structure.1982In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 117, p. 676-Article in journal (Refereed)
    Abstract [en]

    We show how a new combination of methods can be used in order to gain information on hydrogen dissociation on Pd and on its dependence on the electronic structure. With this method we can also detect changes in hydrogen pressure of about 1×10−11 Torr H2 corresponding to hydrogen coverages on the Pd surface of about 0.001 of a monolayer.

  • 41. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Karlsson, S.-E.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Surface reactions on Pd studied with a hydrogen sensitive MOS-structure and photoelectron spectroscopy1982In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 25, no 6A, p. 818-825Article in journal (Refereed)
    Abstract [en]

    During the last couple of years catalytic reactions on Pd surfaces have been studied at our department by means of a hydrogen sensitive Pd-MOS structure and work function measurements. These studies have been performed at atmospheric pressures with Ar and O2 as carrier gases. We have now extended this type of measurements to the ultra-high vacuum (UHV) region and also combined them with both UV and, in certain cases, X-ray photoelectron spectroscopy (UPS, XPS) studies. With this technique we are able to detect about 0.001 of a monolayer of hydrogen, and changes in rate or equilibrium constants corresponding to changes in an energy coordinate of less than 10 meV. Furthermore, results from a Cd contaminated Pd-MOS structure indicates that the ability of Pd to dissociate H2 is related to a microscopic parameter and not to any general metal-like parameter.

  • 42. Petersson, L-G
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Karlsson, S-E
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Surface reactions on Pd studied with a hydrogen sensitive MOS-structure andphotoelectron spectroscopy1982In: Physica scripta. T, ISSN 0281-1847, Vol. 25, p. 818-Article in journal (Refereed)
    Abstract [en]

    During the last couple of years catalytic reactions on Pd surfaces have been studied at our department by means of a hydrogen sensitive Pd-MOS structure and work function measurements. These studies have been performed at atmospheric pressures with Ar and O2 as carrier gases. We have now extended this type of measurements to the ultra-high vacuum (UHV) region and also combined them with both UV and, in certain cases, X-ray photoelectron spectroscopy (UPS, XPS) studies. With this technique we are able to detect about 0.001 of a monolayer of hydrogen, and changes in rate or equilibrium constants corresponding to changes in an energy coordinate of less than 10 meV. Furthermore, results from a Cd contaminated Pd-MOS structure indicates that the ability of Pd to dissociate H2 is related to a microscopic parameter and not to any general metal-like parameter.

  • 43.
    Petersson, L.-G.
    et al.
    Linköping University.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Karlsson, S.-E.
    Linköpings universitet.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    The influence of small amounts of Ag on a hydrogen sensitive Pd-MOS structure1982Conference paper (Refereed)
  • 44.
    Petersson, L.-G.
    et al.
    Linköpings universitet.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    A Pd-MOS structure as a hydrogen sensor in catalytic reactions1983Conference paper (Refereed)
  • 45. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    A Pd-MOS structure as a hydrogen sensor in catalytic reactions1984In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. A2, p. 1032-Article in journal (Refereed)
    Abstract [en]

    By letting a catalytic reaction involving hydrogen occur on the Pd gate metal of a Pd–MOS structure the amount of hydrogen atoms on the surface can be monitored without any external probes by measuring the dipole induced by the hydrogen atoms that have diffused to the Pd–SiO2 interface. The ability to work over a wide pressure range (10-11 Torr to atm) makes the Pd–MOS structure an interesting device in the study of catalytic reactions. In this article, we will give a short review of some of the many applications of this component. We have combined this technique with other surface sensitive techniques such as UPS, XPS, work function measurements and mass spectrometry and, e.g., studied how the hydrogen adsorption–desorption processes are influenced by alloying the Pd surface with various amounts of Ag, thereby also changing the distribution of d states close to Fermi energy. We have also studied the H2+O→H2O reaction on Pd. It, e.g., turns out that the water reaction rate reaches a maximum when the oxygen coverage approaches zero and that the hydrogen atoms on the surface have a larger lateral mobility.

  • 46. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Hydrogen desorption versus electronic structure studies on Ag covered Pd with photoemission and a hydrogen sensitive MOS structure1984In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 30, p. 3055-Article in journal (Refereed)
    Abstract [en]

    With a hydrogen-sensitive Pd metal-oxide-semiconductor structure we have investigated how Ag overlayers affect the hydrogen adsorption and desorption properties of Pd. By varying the concentration of Ag in the top layer, we have continuously changed the distribution of d states close to the Fermi energy as determined by photoemission. For moderate amounts of Ag, only blocking of active hydrogen sites on the Pd surface occurs and no effects due to the variation in the electronic density of states can be detected.

  • 47. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Hydrogen detection during catalytic surface reactions: Evidence for activated lateral hydrogen mobility in the water forming reaction on Pd1984In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 52, p. 1806-Article in journal (Refereed)
    Abstract [en]

    By use of a Pd-SiO2-Si structure as a hydrogen sensor, very small changes in the hydrogen pressure can be detected. Furthermore, such a structure can be used to detect hydrogen with perfect discrimination during a catalytic surface reaction. By using this technique, together with work-function and desorption measurements, in the study of the water-forming reaction on Pd, we conclude that hydrogen has an activated lateral mobility on Pd.

  • 48.
    Petersson, L.-G.
    et al.
    Linköpings universitet.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    The influence of Ag on the hydrogen desorption properties of Pd studied with photoemission and a hydrogen sensitive MOS structure1983Conference paper (Refereed)
  • 49.
    Petersson, L.-G.
    et al.
    Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    The water forming reaction on palladium studied with work function, photoemission, and mass spectrometry on a hydrogen sensitive MOS structure1983Conference paper (Refereed)
  • 50. Petersson, L.-G.
    et al.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    The water-forming reaction on Pd1985In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 161, p. 77-Article in journal (Refereed)
    Abstract [en]

    The water-forming reaction on Pd has been studied on a Pd---SiO2---Si (Pd-MOS) structure in the temperature range 323–473 K. The reaction is found to be of the Langmuir-Hinshelwood type with the formation of OH beeing rate limiting. Since the Pd-MOS structure works as a sensitive hydrogen detector unique information on the behaviour of hydrogen during this catalytic reaction has been obtained. The reaction can be described in a model where the hydrogen atoms on the Pd surface have a large temperature activated lateral mobility and with no evidence of beeing in hot precursor states. At T = 473 K this means that for oxygen coverages 0.01 monolayers all hydrogen adsorbed will also react with oxygen. For smaller oxygen coverages unreacted hydrogen will not initially desorb towards the vacuum but towards the internal Pd surface of the Pd-MOS structure. Futhermore, hydrogen adsorption is blocked by adsorbed oxygen. The sticking coefficient for hydrogen on the bare Pd surface is, however, close to one and only weakly temperature dependent. An effect giving rise to a hysteresis in the work function versus oxygen coverage curve during oxygen adsorption - desorption is also discussed.

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