INDEX single

Cumulative Subject Index Single electron transfer reactions... 

In situ Fourier transform infrared and in situ infrared reflection spectroscopies have been used to study the electrical double layer structure and adsorption of various species at low-index single-crystal faces of Au, Pt, and other electrodes.206"210 It has been shown that if the ions in the solution have vibrational bands, it is possible to relate their excess density to the experimentally observed surface. 

Markovic NM, Grgur BN, Ross PN. 1997. Temperature-dependent hydrogen electrochemistry on platinum low-index single-crystal surfaces in acid solutions. J Phys Chem B 101 5405-5413. 

Xia XH, Liess HD, Iwasita T. 1997. Early stages in the oxidation of ethanol at low index single crystal platinum electrodes. J Electroanal Chem 437 233-240. 

Markovic NM, Adzic RR, Cahan BD, Yeager EB. 1994. Structural effects in electrocatalysis— Oxygen reduction on platinum low-index single-crystal surfaces in perchloric-acid solutions. J Electroanal Chem 377 249-259. 

Feddrix s used similar single crystal techniques and concluded that the three low index single crystal siufaces are ranked as ... 

Figure 5. (A) Voltammograms on Ir and Pt low-index single crystals at 50 mV s in O.SM H2SO4. Solid curves are for Ir and dotted ones for Pt. (B) Anodic voltammograms on various iridium single crystals. (From Ref. 32.)...

Cyclic voltammograms of Pb on low-index single-crystal Au were obsaved in HC104. Voltammograms of Pb underpotential deposition on various index Au faces were observed in 0.01 M HCIO4-1- ImM Pb solution. Since the voltammograms of Pb underpotential deposition are... 

Underpotential deposition of Zn on R was seen as adsorption of Zvi ions in 1970, since is as high as 1V, a value that well exceeds the one expected from previous results on various metal combinations of underpotential deposition systems. Recently, Zn underpotential deposition on R was reported in acidic solutions, and then in alkaline solutions. Zn underpotential deposition on Pd was also found in acidic and alkaline solutions. Then cyclic voltammograms of underpotential deposition on three low-index, single-crystal Rs were observed in sulfuric and perchloric acid solutions, as shown in Figs. 27 and 28. " In comparing Figs. 27 and 28, Zn underpotential deposition on R seans to take place only on Pt(llO), but not on Pt(lll) and Pt(lOO). Therefore it can be said that a cyclic voltammogram on polycrystalline R was observed on a R(110)-like surface. 

In partly ionized plasmas, where both the charged and neutral particles are in concentrations large enough to make measurable contributions to the refractive index, single wavelength interferometry cannot separate that part of refractivity resulting from the neutral components. 

Recently, Kuzume et al. [408] have studied copper UPD at high-index single-crystal Au surfaces. 

Rate Constants for 02 Reduction on Low-Index Single-Crystal Electrodes in... 

Several groups report that the dynamic behavior of formic acid oxidation on low-index single crystal planes exhibits structural effects [119, 120, 124, 127], According to these studies, current oscillations were easily observed on Pt(100), seemed to exist in only a small parameter interval on Pt(110), and proved to be even more difficult... 

Still most dynamical simulations of reactions at surfaces are limited to rather simple systems, such as the adsorption of diatomic molecules on low-index single crystal surfaces. With the development of more efficient algorithms and the improvement of computer power, more and more complex systems will be able to be addressed. One recent example is the ab initio molecular dynamics simulation of the soft-landing of Pd clusters on oxide surfaces [127] where up to n = 13 Pd atoms have been taken into account in the calculations. 

In recent years, many papers have been published dealing with the interaction of acetylene with the low index single crystal copper (lll)[6-8, 13-15], (110)[9,16,17] and (100)[ 17-29] surfaces. 

We mentioned above three types of optical fibers step index single mode, step index multimode, and gradient index multimode. The last two types can carry more light that the step index single mode fiber. Lightness is a very important feature. Among the important features for such a system are the following (Oare, 1995) ... 

However, this assumption is not necessarily justified. Even for a well-faceted nanoparticle there are a number of nonequivalent adsorption sites. For example, in addition to the low-index facets, the palladium nanoparticle exhibits edges and interface sites as well as defects (steps, kinks) that are not present on a Pd(l 1 1) or Pd(lOO) surface. The overall catalytic performance will depend on the contributions of the various sites, and the activities of these sites may differ strongly from each other. Of course, one can argue that stepped/kinked high-index single-crystal surfaces (Fig. 2) would be better models (64,65), but this approach still does not mimic the complex situation on a metal nanoparticle. For example, the diffusion-coupled interplay of molecules adsorbed on different facets of a nanoparticle (66) or the size-dependent electronic structure of a metal nanoparticle cannot be represented by a single crystal with dimensions of centimeters (67). It is also shown below that some properties are merely determined by the finite size or volume of nanoparticles (68). Consequently, the properties of a metal nanoparticle are not simply a superposition of the properties of its individual surface facets. 

The last topic to comment is the difference between the optimum compositions in Ru of the Pt-Ru alloys for the oxidation of CO (50 at.% Ru) and methanol (10-20 at.% Ru). Gasteiger et al. " proposed an explanation based on a statistical modelization of the surface of an alloy containing x at.% Ru. The stmctural atomic model proposed by these authors needs a maximum number of 3-fold platinum sites for the adsorption of the CH3OH molecule, and adjacent to 1 Ru atom to adsorb the OH species. This would correspond to a surface with 8-14 at.% Ru depending on the orientation of the low index single crystal planes, 8% for (111), 10% for (100)... 

Ferrare R. A., Meffi S. H., Whiteman D. N., Evans K. D., Poellot M., and Kaufman Y. J. (1998b) Raman hdar measurements of aerosol extinction and backscattering 2. Derivation of aerosol real refractive index, single-scattering albedo, and humidification factor using Raman hdar and aircraft size distribution measurements. J. Geophys. Res. 103, 19673-19689. 

Several groups have emphasized that the dynamic behavior of formic acid oxidation on low-index single-crystal planes exhibits stmctural effects. According to these studies, current oscillations were easily... 

Thiophene HDS Activities have been reported by Bussell et al. over three low Miller index single-crystal surfaces of Mo and four of Re (104-106). The reaction over Mo was insensitive to the surface structure. The Re(0001) surface showed about the same activity as the Mo surfaces, but Re( 1121) was twice as active, and the (1120) and (1010) surfaces were approximately sixfold more active (106). While Mo surfaces were covered with a near monolayer of partially hydrogenated carbon after reaction, the Re was not moderated by a carbon overlayer. The product distribution over Mo(100) was similar to that reported for powder MoS2 catalysts, although the single-crystal surface of pure Mo was much more active (104). Measurements of the rate of hydrogenation of 35S on Mo(100) suggest that sulfur adatoms are not intermediates in thiophene HDS (104). 

The influence of the surface structure of electrodes on electrochemical processes has been a central topic of basic electrochemical research in recent years. Advances were mainly achieved due to the utilization of structurally defined electrodes, usually low-index single-crystal surfaces, and to the development of surface-sensitive analytical techniques for the in-situ characterization of electrodes [1, 2]. Most of the advances can be attributed to the application of the latter, the new techniques, to the former, namely the well-defined surfaces. This approach has proven very powerful and its... 

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