Silver polycrystalline

M. Stoukides, and C.G. Vayenas, The effect of Electrochemical Oxygen Pumping on the Rate and Selectivity of Ethylene Oxidation on Polycrystalline Silver, J. Catal. 70, 137-146(1981). 

GP 2] [R 2] Initial work with a steel multi-plate-stack micro reactor with micro-structured platelets made of polycrystalline silver (OAOR modified) confirmed a selectivity of up to 49% at conversions of about 12% (3 vol.-% ethylene, 50 vol.-% oxygen, balance nitrogen 5 bar 41 h 277 °C) [4, 26, 40]. 

Cuesta A, Lopez N, Gutierrez C. 2003. Electrolyte electroreflectance study of carbon monoxide adsorption on polycrystalline silver and gold electrodes. Electrochim Acta 48 2949-2956. Date M, Hamta M. 2001. Moisture effect on CO oxidation over Au/Ti02 catalyst. J Catal 201 221-224. 

The catalytic activity and selectivity of polycrystalline silver catalysts used for ethylene2epoxidation can be affected significantly by electrochemical 0 pumping. This new phenomenon was studied in the solid electrolyte cell... 

The activity and ethylene oxide selectivity of porous polycrystalline silver catalysts can be altered significantly by using... 

Figure 3.15 O Is / Ag 3d5/2 XPS intensity ratio as a function of take-off angle for two oxygen species on polycrystalline silver. The data corresponding to an O 1 s binding energy of 528.4 eV are attributed to subsurface oxygen in Ag, the other with a binding energy of 530.5 eV to oxygen atoms adsorbed on the Ag surface (data from Baschenko et al. (39J).

Charge-Transfer Reaction Inverse Photoemission at Gold(lll) and Polycrystalline Silver Electrodes... 

Figure 1. The current (a) and the second harmonic signal (b) obtained during the potential cycling (10 mV s"1 scan rate) from a polycrystalline silver electrode in a 0.1M LiClC>4 aceto nitrile solution.

All SERS experiments were conducted with a polycrystalline silver working electrode prepared by press-fitting a 6 mm diameter cylinder of silver into one end of a 0.375 inch diameter Teflon rod through which a 6 nm diameter concentric hole had been drilled. Electrical contact was made via a copper wire soldered to the silver. The geometric area of the silver disk was 0.28 cm2. 

Figure6.6. (a) ARUPS spectra(F 150K,n 20eV)ofTTF-TCNQalongthe chain direction. The dashed line outlines the dispersion of the main spectral feature, (b) ARUPS spectra along the perpendicular a-direction. (c) Selected spectra from (a), after background subtraction. The asterisks mark the main dispersive peak, and the arrows mark emission not accounted for by band theory. Energies are referred to E-p, determined to 1 meV accuracy on an evaporated, polycrystalline silver film. Reprinted with permission from F. Zwick, D. Jdrome, G. Margaritondo, M. Onellion, J. Voit and M. Grioni, Physical Review Letters, 81, 2974 (1998). Copyright (1998) by the American Physical Society.

Figure 6.25. Valence band photoemission spectra of 1 ML Ceo on a Ag(lOO) surface as a function of potassium doping. Also shown are the spectra of the clean Ag(lOO) surface and of a Ceo multilayer (bottom). All binding energies are referred to the L f of polycrystalline silver. Reprinted from Surface Science, Vols. 454-456, C. Cepek, M. Sancrotti, T. Greber and J. Osterwalder, Electronic structure of K doped Ceo monolayers on Ag(OOl), 467 71, Copyright (2000), with permission from Elsevier.

Person 1 Calcnlate the self-diffusivity in polycrystalline silver (grain boundary diffusion), Dgb, at 500°C in m /s. What is the activation energy for this process in kJ/mol ... 

One of the reasons that the full study of UPD was delayed until the mid-1970s (Lorenz, 1973) is that it is much more sharply seen on well-defined single-crystal planes than on polyciystals. There was widespread use of single crystals in metal deposition work in the 1970s. This is exemplified in Fig. 7.141, which shows the less sharp peaks for Pb2+ depositing on polycrystalline silver. In contrast are the corresponding phenomena for Pb2+ depositing on Ag (111) in Fig. 7.142. 

This additional contribution was first noted by Lee et al. [24] for polycrystalline silver and examined in more detail later by several groups on polycrystalline silver [44, 54, 58-60], single crystal bulk silver electrodes [7, 42, 43, 56, 127], and on thin silver films [55, 57, 101, 128]. For the early single crystal work [42, 43, 56] the studies were performed at a fixed electrode geometry with the crystal axis direction unknown relative to the incident beam. 

Several other studies have appeared for T1 deposition on polycrystalline Ag which are pertinent to this discussion. The work of Furtak et al. [148] shows the sensitivity to the deposition of thallium on mechanically polished silver surfaces. They attribute a decrease in observed intensity prior to T1 deposition to a physisorbed state of T1 on the silver surface. In another study, Robinson and Richmond [54] performed time-resolved measurements on the deposition of T1 on electrochemically polished polycrystalline silver. Sharper UPD peaks were observed in this study compared to the previous work. The interesting aspect of this work was the sequential nature by... 

For these experiments, a polycrystalline silver foil (Alfa Products, m3N, 0.127 mm thick) cleaned by multiple Ar+ sputtering/thermal annealing cycles [54] was used as a substrate. 

In order to increase the resolution, a heterodyne circuit may be used, which consists of two oscillators the quartz crystal microbalance and a second reference crystal. The frequency difference in the kilohertz range can be measured with a universal counter and the same resolution and gate time discussed above are valid however if the period of the differential wave is measured, the accuracy can be highly increased and a 1 Hz resolution is easily attainable for a 1 ms gate time. This approach has been used by Sheng-li Chen et al. [19] to measure the kinetics of silver oxide formation on polycrystalline silver. These authors reported a resolution of 0.1 Hz in 1 ms which corresponds to 0.44 ng cm"2 in the mass sensitivity. 

FIGURE 17 Variation of the PTRMS signal from ethylene oxide with temperature, measured in reaction mixtures with Pc2h — 0.1 mbar + P0 = 0.25 mbar in the presence of a polycrystalline silver foil. The last parts of the curves were measured after stopping the oxygen flow. 

Ardizzone, S., Cappelletti, G., Mussini, P.R., Rondinini, S. and Doubova, L.M. (2003a) Electrode-posited polycrystalline silver electrodes Surface control for electrocatalytical studies. Russ. J. Electrochem. (translation of Elektrokhimija) 39, 170-176. 

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