Interaction of Hydrogen with a Cobalt(0001) Surface
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Zita Huesges
Abstract
The interaction of hydrogen and deuterium with the Co(0001) surface has been studied in UHV between 90 and 500 K by means of LEED, temperature-programmed thermal desorption (TPD) and work function change (ΔΦ) measurements. Hydrogen adsorbs spontaneously and dissociatively in two atomic binding states denoted as β1 and β2 with a high initial sticking probability. The adsorption energies E(β1) and E(β2) are 80 and 100 kJ/mol, respectively, if a first-order desorption kinetics is assumed (a second-order kinetic analysis yields unreasonably low values for both the desorption energies and frequency factors). At sufficiently low temperatures, the adsorbed H atoms form a faint (2 × 2) LEED superstructure, which is best developed after an exposure of ∼20 L. From the temperature dependence of the fractional-order beam intensity at different exposures we determine the critical temperature of the (2 × 2) phase as ∼ 243 ( ± 10) K. Similar to the H-on-Ni(111) system the existence range of the (2 × 2) phase in the temperature–coverage plane is asymmetric; i.e., below the critical coverage Θcrit the respective long-range order has a higher range of stability than above Θcrit. By analogy with H/Ni(111), we assume a similar honeycomb H structure also for the H-on-Co(0001) system and suggest the critical coverage Θcrit to be 0.5, i.e., half a monolayer of H atoms. The H-induced work function change is surprisingly small; it decreases, forms a shallow minimum of −18 meV after ∼20 L exposure around the optimum coverage of the (2 × 2) phase and reaches a saturation value of −10 meV. Our data are discussed and compared with previous work on H/Co(0001) and other close-packed transition metal surfaces, especially with the H-on-Ni(111) system.
© by Oldenbourg Wissenschaftsverlag, München, Germany
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Articles in the same Issue
- Editorial
- Biography of Prof. Dr. Hans-Heinrich Limbach
- Alumni and long term guests of the Limbach group
- NMR and FT-IR Studies on the Association of Derivatives of Thymidine, Adenosine, and 6-N-Methyl-Adenosine in Aprotic Solvents
- Competition between Hydrogen Bonds and Lewis Acid-Base Interactions in the Equilibria between Bis(pentafluorophenyl)borinic Acid and Pyridine: Insights from NMR, Diffractometric and Computational Studies
- Energy Analysis of Competing Non-Covalent Interaction in 1:1 and 1:2 Adducts of Collidine with Benzoic Acids by Means of X-Ray Diffraction
- A TT Dinucleotide with a Nonionic Silyl Backbone: Impact on Conformation and H-Bond Mediated Base Pairing as Studied by Low-Temperature NMR
- Oxygen and Hydrogen Isotopic Preference in Hydration Spheres of Chloride and Sulfate Ions
- Ab Initio Study of Cooperative Effects in Complexes X:HBO:Z, with X, Z=LiH, HNC, HF, HCN, HCl, ClF, and HBO: Structures, Binding Energies, and Spin-Spin Coupling Constants across Intermolecular Bonds
- The Structure and Dynamic Properties of 1H-Pyrazole-4-Carboxylic Acids in the Solid State
- Acridine – a Promising Fluorescence Probe of Non-Covalent Molecular Interactions
- First Example of Hydrogen Bonding to Platinum Hydride
- Interaction of Hydrogen with a Cobalt(0001) Surface
- Immobilization and Characterization of RuCl2(PPh3)3 Mesoporous Silica SBA-3
- Secondary Isotope Effects on 13C and 15N Chemical Shifts of Schiff Bases Revisited
- Analysis of Nutation Patterns in Fourier-Transform NMR of Non-Thermally Polarized Multispin Systems
- The Structure of Supercooled Water and the Mechanism of Homogeneous Nucleation of Ice Ih
- Probing Small Protonated Water Clusters in Acetonitrile Solutions by 1H NMR
- Double Hydrogen Transfer in Low Symmetry Porphycenes
- Nuclear Spin Selective Torsional States: Implications of Molecular Symmetry
