12053-70-2Relevant academic research and scientific papers
Effect of the support on the nature of metal-promoter interactions in Ru-Cs+/MgO and Ru-Cs+-Al2O3 catalysts for ammonia synthesis
Larichev,Moroz,Moroz,Zaikovskii,Yunusov,Kalyuzhnaya,Shur,Bukhtiyarov
, p. 891 - 899 (2005)
The Ru-Cs+/MgO and Ru-Cs+/γ-Al 2O3 catalysts, which were prepared by an impregnation method using RuOHCl3 and Cs2CO3 as precursor compounds and reduced with H2 at 450°C, are characterized by X-ray diffraction, high-resolution transmission electron microscopy (with X-ray microanalysis), and X-ray photoelectron spectroscopy (XPS). The Cs +/MgO(Al2O3) systems, Ru-Cs+ black, and model systems prepared by cesium sputtering onto polycrystalline ruthenium foil are studied as reference samples. It is found that, in the Ru-Cs +/MgO sample, cesium is present as a Cs2 + xO cesium suboxide, which weakly interacts with the support, localized on the surface of Ru particles or near them. In the case of Ru-Cs+/γ-Al 2O3, cesium occurs as a species that is tightly bound to the support; this is likely surface cesium aluminate, which prevents promoter migration to Ru particles. The Ru-Cs+/MgO sample exhibits a considerable shift of the Ru3d line in the XPS spectra toward lower binding energies, as compared to the bulk metal. It is hypothesized that this shift is due to a decrease in the electron work function from the surface of ruthenium because of the polarizing effect of Cs+ ions in contact with Ru particles. Based on the experimental results, the great difference between the catalytic activities of the Ru-Cs+/MgO and Ru-Cs+/γ- Al2O3 systems in ammonia synthesis at 250-400°C and atmospheric pressure is explained.
Bad-Metal-Layered Sulfide Oxide CsV2S2O
Valldor, Martin,Merz, Patrick,Prots, Yurii,Schnelle, Walter
, p. 23 - 27 (2016)
Through a solid-state reaction between stoichiometric amounts of a mixed cesium oxide Cs2O1.3, VS, S, and V2O5, a polycrystalline powder of CsV2S2O was obtained. Small single crystals could be grown in a CsCl melt by allowing Cs2SO4, V metal and S powders to react. The crystals have a plate-like morphology, consistent with the tetragonal crystal-structure symmetry [P4/mmm, a = 3.9455(1), c = 7.4785(1) ?]. Magnetic measurements suggest that CsV2S2O is a temperature-independent paramagnet, and resistivity data concur with a bad metal. The mixed oxidation state of V on one crystallographic site offers a tentative explanation of the electronic properties of the title compound. CsV2S2O has a tetragonal crystal structure and contains Cs-separated V-S-O layers with relatively short V-V distances of 2.790 ?. V has formally a charge of +2.5, resulting in temperature-independent paramagnetism and bad-metal-like electric conductivity.
Characterization of oxides of cesium
Band,Albu-Yaron,Livneh,Cohen,Feldman,Shimon,Popovitz-Biro,Lyahovitskaya,Tenne
, p. 12360 - 12367 (2004)
Cesium oxides are materials of great interest to the photodetection industry because of their relatively low work function (a??1 eV). Used mainly as coating films for photoemissive devices, they provide high wavelength thresholds and high photocurrents. However, they are unstable, air-sensitive, and hygroscopic, rendering them short-lived and limiting their applications. Although the technology of these devices is highly developed, their characterization on the micro- and nanoscale suffers from their poor chemical stability and poor crystallinity. In the present study, cesium oxides were synthesized from the elements and were characterized using a combination of chemical and structural analysis techniques. Because the reaction products were extremely sensitive to humidity, sample analysis without atmospheric exposure was essential, and techniques were developed for the transfer of the samples to the measurements systems. Extensive data obtained from X-ray energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and Raman microscopy were obtained. Raman spectra with bands at 103, 742, and 1134 cm-1 strongly confirmed the presence of the oxide, peroxide, and Superoxide ions, respectively, as well as the absence of carbonate as an impurity. The A1g mode of Cs2O was detected as an anti-Stokes band at 103 cm-1. This study provides further insight into the reactivity of the various cesium oxides.
Oxidation of Cs2Te with superficial Te clusters studied by XPS
Soriano, L.,Galan, L.,Rueda, F.
, p. 1075 - 1080 (1991)
The oxidation of alkali-metal (Cs, K) tellurides at room temperature and low oxygen pressure has been studied by X-ray photoelectron and Auger electron spectroscopies (XPS, XAES). The oxidation kinetics is faster than logarithmic and does not saturate for the exposures studied, while a migration of alkali ions to the surface is detected. These effects are strongly enhanced in a sample of overcaesiated telluride with elemental Te clusters on the surface. A strong gradient of the oxidation state (Te2-, Te0, Te4+, Te6+) is formed in a depth of the order of the XPS analysis depth. The oxygen concentration shows a similar gradient. Cs2O2 is formed too. The surface layer remains as Cs2Te; the Te clusters also remain unreactive at the surface; they only transform into telluride when heavy oxidation of the Cs2Te film is reached.
