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Adsorption Structure (adsorption + structure)

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Chemistry	100%

Selected Abstracts

Carbon Dioxide Activation by Surface Excess Electrons: An EPR Study of the CO2, Radical Ion Adsorbed on the Surface of MgO

CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2007
Mario Chiesa Dr.
Abstract The CO2, radical anion has been generated at the surface of MgO by direct electron transfer from surface trapped excess electrons and characterized by electron paramagnetic resonance spectroscopy. Both 13C and 17O hyperfine structures have been resolved for the first time, leading to a detailed mapping of the unpaired electron spin density distribution over the entire radical anion. The magnetic equivalence of the two O nuclei has been ascertained allowing a side-on adsorption structure at low-coordinate Mg2+ ions to be proposed for the surface stabilized radical. [source]

Redox Activity and Structural Transition of Heptyl Viologen Adlayers on Cu(100),

CHEMPHYSCHEM, Issue 7 2010
Min Jiang Dr.
Abstract The redox behaviour and potential-dependent adsorption structure of heptyl viologen (1,1,-diheptyl-4,4,-bipyridinium dichloride, DHV2+) on a Cu(100) electrode was investigated in a chloride-containing electrolyte solution by cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC,STM). The dicationic DHV molecules generate a few pairs of current waves in CV measurements which are ascribed to two typical one-electron transfer steps. STM images obtained in a KCl-containing electrolyte solution disclose a well-ordered c(2×2) chloride adlayer on a Cu(100) electrode surface. After injecting DHV2+ molecules into the KCl electrolyte solution, a highly ordered 2D "dot-array" structure in STM images emerges on the c(2×2)-Cl modified Cu(100) electrode surface. DHV2+ molecules spontaneously arrange themselves with their molecular planes facing the electrode surface and their long molecular axis parallel to the step edge. Such adsorption structure can be described by mirror domains and rotational domains which stably exist between 200 mV and ,100 mV. One-electron reduction of the dications DHV2+ around ,150 mV causes a phase transition from a ,dot-array' assembly to a stripe pattern formed by DHV.+ radical monocations in STM images which has a bilayer structure. With a further decrease of the applied electrode potential, the structure of the DHV.+ adlayer undergoes a change from a loose stripe phase to a more compact stripe phase, a subsequent decay of the compact structure, and finally the formation of a new dimer phase. A further electron transfer reaction at ,400 mV causes the formation of an amorphous phase on the chloride free electrode surface. In a reverse anodic sweep, the reproduction of the ordered DHV.+ stacking phase occurs again on top of the chloride lattice. [source]

CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical Investigation

CHEMPHYSCHEM, Issue 11 2008
Song Han Dr.
Abstract Density functional theory calculations are carried out to study CO adsorption on the (001) surface of a LaNi5 hydrogen storage alloy. At low coverages, CO favors adsorption on NiNi bridge sites. With an increase in CO coverage, the decrease in the adsorption energy is much larger for NiNiCO bridge adsorption than that for NiCO on-top adsorption. Thus, the latter sites in the relatively stable adsorption structure are preferentially utilized at high CO coverages. The nature of the bonding between CO and the LaNi5 (001) surface is analyzed in detail. [source]