Surface Structure and Electronic Properties

1 Studies of Classy Metals in As-quenched State a) Surface Structure and Electronic Properties 

Similar surface morphology was found by Wul et al. [4.58] for amorphous Fe,MZi, prepared by melt-spinning. They concluded from their STM investigations that the surface of the Fc Zr samples was at least partially crystallized. 

A) STM profile plot of a 2 x 2 nm surface area of Rh,5Zr75 after 45 min sputtering with 5 keV Ar ions [4.57J. B) Image of the local tunneling harrier height, which corresponds to the topographic image in I ig. 4.1 A 

Guczi and coworkers [4.61] studied CO chemisorption on glassy and crystalline FeNiB alloys in the presence and in the absence of hydrogen using XPS and UPS. They found that CO chemisorption at 300 K is characteristic of the surface structure. At S70 K, no difference could be observed in the mode of chemisorption because only dissociative carbon was present. However, the reactivity differences observed in the CO + H2 reaction could be ascribed to the difference in the surface transformation of the carbidic species. The authors suggested that this species can be stabilized by the small ensemble size characteristic for glassy and partially crystallized samples, whereas the main route of the dissociative carbon on crystallized samples is the inactive bulk carbide formation. This phenomenon was found to be influenced by the alloy composition and by the presence of hydrogen. 

Unfortunately, only relatively little studies have been carried out so far where the influence of the electronic structure of a glassy metal substrate on the chemisorption behavior of probe molecules such as CO and N2 has been investigated. However, in view of the high flexibility in the chemical composition 

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Careful characterization of the oxide-electrolyte interface is needed electrochemical area, surface structure, and electronic properties (potential distribution and density of electrical carriers). Chemical and electrochemic-ally induced transformations of the oxide surface in contact with electrolyte can substantially modify the behavior of oxide electrodes. Extrapolation of gas/solid oxide results to oxide electrodes is not always valid since the oxide-electrolyte interface can strongly depend on electrolyte type and applied potential. 

As part of an overall study of the electrode/electrolyte interphase of the electronically conducting polymer, polypyrrole, the surface structure and electronic properties have been investigated. 

A widespread interest for the electrochemical oxygen reduction reaction (ORR) has two aspects. The reaction attracts considerable attention from fundamental point of view, as well as it is the most important reaction for application in electrochemical energy conversion devices. It has been in the focus of theoretical considerations as four-electron reaction, very sensitive to the electrode surface structural and electronic properties. It may include a number of elementary reactions, involving electron transfer steps and chemical steps that can form various parallel-consecutive pathways [1-3]. 

We shall first review the basic principles of VASP and than describe exemplary applications to alloys and compounds (a) the calculation of the elastic and dynamic properties of a metallic compound (CoSi2), (b) the surface reconstruction of a semiconducting compound (SiC), and (c) the calculation of the structural and electronic properties of K Sbi-j, Zintl-phases in the licpiid state. 

In this contribution it is shown that local density functional (LDF) theory accurately predicts structural and electronic properties of metallic systems (such as W and its (001) surface) and covalently bonded systems (such as graphite and the ethylene and fluorine molecules). Furthermore, electron density related quantities such as the spin density compare excellently with experiment as illustrated for the di-phenyl-picryl-hydrazyl (DPPH) radical. Finally, the capabilities of this approach are demonstrated for the bonding of Cu and Ag on a Si(lll) surface as related to their catalytic activities. Thus, LDF theory provides a unified approach to the electronic structures of metals, covalendy bonded molecules, as well as semiconductor surfaces. 

The late 1980s saw the introduction into electrochemistry of a major new technique, scanning tunnelling microscopy (STM), which allows real-space (atomic) imaging of the structural and electronic properties of both bare and adsorbate-covered surfaces. The technique had originally been exploited at the gas/so id interface, but it was later realised that it could be employed in liquids. As a result, it has rapidly found application in electrochemistry. 

Here, we discuss in some detail the DFT implementation in our computer program, since only in the last few years DFT is becoming more familiar to the chemists community, as opposite to the physicists community, where it was used routinely for the last thirty years for obtaining structural and electronic properties of bulk solids and surfaces [19],... 

By controlling the structural and electronic properties of sNPS which are related to the nanocrystallite dimensions and porosity, their surface selectivity and sensitivity to different gases (nitrogen and carbon oxide, vapors of water and organic substances) can be adjusted. This approach for the effective detection of acetone, methanol and water vapor in air was described in [13-15].The minimal detectable acetone concentration was reported to be 12 pg/mL. Silicon sensors for detection of SO2 and some medicines such as penicillin were created [16-18]. sNPS were used for the development of a number of immune biosensors, particularly using the photoluminescence detection. Earlier we developed similar immune biosensors for the control of the myoglobin level in blood and for monitoring of bacterial proteins in air [19-23]. 

This resulted in a need for appropriate characterization of the structural and electronic properties of electrode surfaces and detection of adsorbed intermediates in electrode reactions. 

Activity and selectivity in electrocatalysis are determined, in most cases, by the activity, selectivity, structural, and electronic properties of electrode surfaces and the stability to deactivation of such surfaces. The... 

Jacques Chevallier, Hydrogen Diffusion and Acceptor Passivation in Diamond Jurgen Ristein, Structural and Electronic Properties of Diamond Surfaces John C. Angus, Yuri V. Pleskov and Sally C. Eaton, Electrochemistry of Diamond Greg M. Swain, Electroanalytical Applications of Diamond Electrodes... 

Volumes 50 and 51 of the Advances, published in 2006 and 2007, respectively, were the first of a set of three focused on the physical characterization of solid catalysts in the functioning state. This volume completes the set. The six chapters presented here are largely focused on the determination of structures and electronic properties of components and surfaces of solid catalysts. The first chapter is devoted to photoluminescense spectroscopy it is followed by chapters on Raman spectroscopy ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy X-ray photoelectron spectroscopy X-ray diffraction and X-ray absorption spectroscopy. 

The chemical behavior of monolayer coverages of one metal on the surface of another, i.e., Cu/Ru, Ni/Ru, Ni/W, Fe/W, Pd/W, has recently been shown to be dramatically different from that seen for either of the metallic components separately. These chemical alterations, which modify the chemisorption and catalytic properties of the overlayers, have been correlated with changes in the structural and electronic properties of the bimetallic system. The films are found to grow in a manner which causes them to be strained with respect to their bulk lattice configuration. In addition, unique electronic interface states have been identified with these overlayers. These studies, which include the adsorption of CO and H2 on these overlayers as well as the measurement of the elevated pressure kinetics of the methanation, ethane hydrogenolysis, cyclohexane dehydrogenation reactions, are reviewed. 

We have indicated in Section XVII and XVIII the involvement of oxide films and their surfaces in the electrocatalysis of the anodic Oj and Clj evolution reactions. In this section, we review some of the structures and electronic properties of those important materials, and how such properties are relevant to chemisorption of intermediates. 

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