Molecular scale reactivity at bimetallic surfaces: bridging the pressure gap

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Bimetallic catalysts are widely used for several catalytic processes such as the hydrogenation of unsaturated molecules, or oxidation reactions. These alloy catalysts show an improved selectivity and activity or a higher stability against poisons when compared to the related pure metals. Studies on well defined single crystal surfaces have been performed in UHV or low pressure conditions but there is still little fundamental understanding of the reasons for their beneficial effect under the real pressure and temperature conditions of the catalytic reaction. The purpose of this proposal is to establish a close interaction between experimental techniques and theoretical calculations for a detailed rigorous and quantitative understanding of molecular reaction processes at well defined bimetallic surfaces both under UHV conditions and under high pressure. The group of Bonn will contribute its broad experience in UHV techniques on alloy surfaces. The group of Grenoble will provide its state of the art surface techniques at high pressure (X-ray diffraction at ESRF and laboratory SFG set-up). Moreover, the group of Villeurbanne will bring on one hand its strong expertise in in-situ characterization of catalysis (STM, PM-IRRAS, model reactivity) and on the other hand its knowledge in quantum chemical calculations applied to catalysis. The aim is to create a unique combination of structural techniques (in UHV: STM and LEED, at high pressure: STM and X-ray diffraction), vibrational methods (in UHV: STS and HREELS, at high pressure: IR and SFG), catalysis on model surfaces and quantum calculations (including the influence of gas pressure). The wide combination of approaches, with structural, vibrational, and chemical information, both in UHV and at realistic pressure, should lead to a detailed fundamental understanding of the surface chemistry of unsaturated molecules at alloy surfaces. The target reactions, which have important applications in the chemical industry or for energy production, will be the selective hydrogenation of unsaturated aldehydes and the selective oxidation of CO traces in hydrogen. Such a broad experimental and theoretical approach can only be undertaken in the framework of this collaboration.