1D tungsten oxide nanostructures on a Cu(1 1 0) surface.

Thin epitaxial layers of tungsten oxide on metal substrates are suitable as model systems for investigation of chemical reactivity and catalytic properties. However, the ability to prepare epitaxial tungsten oxide model system in situ is quite rare. Here we present a method to prepare highly ordered tungsten oxide thin film on a Cu(1 1 0) single crystal substrate using physical vapor deposition in a reactive atmosphere of atomic oxygen. The oxygen induced reconstruction of the copper substrate gives rise to unique self-organized 1D structures of tungsten oxide parallel with the Cu[1 -1 0] crystallographic direction. Utilizing a combination of photoemission spectroscopy and density functional theory calculations we reveal emergent physicochemical properties related to the low-dimensionality of the system. Specifically, we observe a support mediated charge redistribution at the interface and a momentum dependent modulation of the valence-band electronic structure. The unusual character of the 1D oxide nanostructures on Cu(1 1 0) surface opens up a unique avenue for preparation of tungsten oxide-based functionalized nanostructures and provides options for further investigation of the fundamental properties of tungsten oxide.

Efficient Ceria-Platinum Inverse Catalyst for Partial Oxidation of Methanol.

Ceria-platinum-based bilayered thin films deposited by magnetron sputtering were developed and tested in regard to their catalytic activity for methanol oxidation by employing a temperature-programmed reaction (TPR) technique. The composition and structure of the samples were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Both conventional (oxide-supported metal nanoparticles [NPs]) and inverse configurations (metal with oxide overlayer) were analyzed to uncover the structural dependence of activity and selectivity of these catalysts with respect to different pathways of methanol oxidation. We clearly demonstrate that the amount of cerium oxide (ceria) loading has a profound influence on methanol oxidation reaction characteristics. Adding a noncontinuous adlayer of ceria greatly enhances the catalytic performance of platinum (Pt) in favor of partial oxidation of methanol (POM), gaining an order of magnitude in the absolute yield of hydrogen. Moreover, the undesired by-production of carbon monoxide (CO) is strongly suppressed, making the ceria-platinum inverse catalyst a great candidate for clean hydrogen production. It is suggested that the methanol oxidation process is facilitated by the synergistic effect between both components of the inverse catalyst (involving oxygen from ceria and providing a reaction site on the adjacent Pt surface) as well as by the fact that the ability of ceria to exchange oxygen (i.e., to alter the oxidation state of Ce between 3+ and 4+) during the reaction is inversely proportional to its thickness. The increased redox capability of the discontinuous ceria adlayer shifts the preferred reaction pathway from dehydrogenation of hydroxymethyl intermediate to CO in favor of its oxidation to formate.