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  • 1985-1989  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Steady and nonsteady rates of reaction in a heterogeneously catalyzed reaction: Oxidation of CO on platinum, experiments and simulations (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4949-4960 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate of reaction for oxidation of CO over (210) and (111) single-crystal surfaces of platinum has been studied as a function of reactant pressures (PO2,PCO) and sample temperature (T), both experimentally and by computer simulation. Experimental results on both surfaces show regions with a steady high rate of reaction followed by a nonsteady transition region and, at high CO pressures, a region with low reactivity caused by CO poisoning of the surface. At constant sample temperature, the transition region can be narrow and depends critically on the ratio of the gas phase concentration of reactants (PCO/PO2). The temperature dependences of the experimental data indicate that the critical ratio and the details for the occurrence of CO poisoning are strongly affected by surface processes such as adsorption, desorption, and diffusion ordering and reconstruction phenomena. A computer simulation model of the Langmuir–Hinshelwood surface reaction as developed by Ziff et al. was used for the simulation of the reaction under flow conditions. The initial fair agreement between this model and the experiment can be significantly improved if processes such as adsorption, desorption, and diffusion are taken into account in an extended simulation model which in turn provides an insight into the kinetics of adsorbate poisoning and the effect of adsorbate-induced processes on the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456736
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The adsorption of hydrogen on a ruthenium (101¯0) surface (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3729-3743 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Video-LEED, HREELS, TDS, and Δcursive-phi measurements were used to investigate the adsorptive, structural, and vibrational properties of the Ru(101¯0)/H system between 100 and 500 K. At all temperatures investigated hydrogen adsorbs dissociatively with very high initial sticking probability (s0(approximate)1.0) with apparent precursor mechanism. The saturation coverage at 100 K is extraordinarily high (aitch-thetamax =2(approximately-equal-to)1.728×1015 H atoms cm−2), up to this coverage four H binding states α, β1, β2, and β3 can be distinguished having desorption energies between 56 KJ/mol (α) and 80 KJ/mol (β3). The H binding states are intimately correlated with the four observable ordered H phases: At aitch-theta=1 a c(8×2) or "1×2'' structure with weak split spots appears which transforms at higher coverages into a clear 1×2 phase with likewise weak spots and with maximum intensity at aitch-theta=1.2. It follows a c(2×2)-3H phase (I maximum at aitch-theta=1.5) with rather more intense ‘extra' spots which fade away with increasing coverage until at aitch-theta=2.0 a (1×1)-2H pattern is reached. The (positive) H-induced work function change Δcursive-phi runs through two maxima and saturates at ∼250 mV. The vibrational loss spectra which were measured in two perpendicular azimuths exhibit a variety of bands which can be correlated with the ordered H phases and point to H species bound in two different kinds of threefold coordinated sites. Our data suggest several structural similarities with the neighboring system in the periodic table, Rh(110)/H, but also interesting differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456856
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction of acetonitrile and benzonitrile with the gold (100) surface (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 7199-7208 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100357a035
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Isotope effects in the interaction of hydrogen and deuterium with a rhodium (110) surface (1987)
    Springer
    Applied physics 44 (1987), S. 87-91 
    Details
    ISSN: 1432-0630
    Keywords: 82.20Tr ; 82.65Jv ; 82.65Nz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The adsorption of H2 and D2 on a Rh (110) surface at 100 K leads to a sequence of ordered phases, among others 1×2 phases atθ H =0.5 and atθ H =1.5 which likely involve a partial surface reconstruction consisting of a small perpendicular displacement of Rh surface atoms. The structure of the adsorbate phases is strongly correlated with the binding energy of the adsorbed phases. Three H (D) binding states (α1,α2 andβ) are populated at saturation as determined by thermal desorption spectroscopy (TDS). Whereas the peak temperature of theβ state is invariant with the hydrogen isotope, the D α1 state appears at a ∼8 Klower and theD α2 state at a ∼5 Khigher temperature than the respective H states. Generally the D phases exhibit a better long-range order than the H phases. The rate of adsorption is identical for the first three adsorbed phases but D2 adsorbs appreciably faster in the 1×2–3H and the final l×1–2H phases. Zero point energy effects as well as a H coverage dependent local interaction model could account for the observed effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617896
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    Paper (German National Licenses)
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