Molybdenum single crystals

D.G. Kelly, M. Salmeron, and G.A. Somorjai, The adsorption and reactions of hydrocarbons on molybdenum single crystal surfaces when clean and in presence of coadsorbed sulfur or carbon, Surf. Sci. 175,465 (1986). 

The present paper reviews the physical and chemical evidence for the above rules obtained over the last several years from ultrahigh vacuum surface science studies of molybdenum single crystals chemically modified by 0, C, S, and B. Additionally, the results of recent studies of methylcyclopropane hydrogenolysis will be presented which illustrate the influence of surface acid/base sites on catalytic hydrocarbon conversions. The surface coverage of each modifier was determined by quantitative Auger electron spectroscopy or x-ray photoelectron spectroscopy (XPS). The atomic structure of oxygen, carbon, and sulfur adlayers below one monolayer (ML)... 

This contradicts, however, the HDS activity of sulfides including M0S2, observed by a high number of authors (see e.g., Refs. 20-25) long before this study on molybdenum single crystals. The loss of activity upon the long thiophene treatment was possibly a consequence of the formation of carbonaceous deposits, the by-products of thiophene HDS. 

Salvador P, Chaparro AM, Mir A (1996) Digital imaging of the effect of photoetching on the photoresponse of n-type tungsten diselenide and molybdenum diselenide single crystal electrodes. J Phys Chem 100 760-768... 

We begin with the structure of a noble metal catalyst. The emphasis is on the preparation of rhodium on aluminum oxide and the nature of the metal-support interaction. Next we focus on a promoted surface in a review of potassium on noble metals. This section illustrates how single crystal techniques have been applied to investigate to what extent promoters perturb the surface of a catalyst. The third study deals with the sulfidic cobalt-molybdenum catalysts used in hydrotreating reactions. Here we are concerned with the composition and structure of the catalytically active... 

Several approaches were investigated for the synthesis of the model catalyst, and the procedure resulting in the most homogeneous sample in terms of cluster size and morphology can essentially be divided into two steps Initially, metallic molybdenum is deposited on a single-crystal Au(l 11) substrate in an atmosphere of H2S at... 

The Mo(IV) aqua ion was first reported by Souchay et al. as a monomeric species in 1966 (93), and the Mo3044+ core structure has been confirmed by single-crystal X-ray structure analyses, as described in this review, 95Mo NMR (94), EXAFS structure analysis (95), and 180-labeling experiments (96), after the appearance of many contradictory reports (97). Information on the reduction products of the Mo(IV) aqua ion is also available (98), Richens and Sykes have summarized the preparation of the different aqua ions of molybdenum in oxidation states II to V (99). 

X-Ray diffraction showed that the molybdenum disulfide powder used in this experiment has a hexagonal layer structure. A remarkable feature of such layer compounds is that the powder is composed of small single crystal particles. In view of these facts, an interesting question arises as to whether... 

Molybdenum(IV) Oxide and Tungsten(IV) Oxide Single Crystals 149... 

MOLYBDENUM(IV) OXIDE AND TUNGSTEN(IV) OXIDE SINGLE CRYSTALS... 

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