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Issue 9, 2009
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Stability of formate species on β-Ga2O3

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Abstract

Gallia (gallium oxide) has been proved to enhance the performance of metal catalysts in a variety of catalytic reactions involving methanol, CO and H2. The presence of formate species as key intermediates in some of these reactions has been reported, although their role is still a matter of debate. In this work, a combined theoretical and experimental approach has been carried out in order to characterize the formation of such formate species over the gallium oxide surface. Infrared spectroscopy experiments of CO adsorption over H2 (or D2) pretreated β-Ga2O3 revealed the formation of several formate species. The β-Ga2O3 (100) surface was modelled by means of periodic DFT calculations. The stability of said species and their vibrational mode assignments are discussed together with the formate interconversion barriers. A possible mechanism is proposed based on the experimental and theoretical results: first CO inserts into surface (monocoordinate) hydroxyl groups leading to monocoordinate formate; this species might evolve to the thermodynamically most stable dicoordinate formate, or might transfer hydrogen to the surface oxidizing to CO2 creating an oxygen vacancy and a hydride group. The barrier for the first step, CO insertion, is calculated to be significantly higher than that of the monocoordinate formate conversion steps. Monocoordinate formates are thus short-lived intermediates playing a key role in the CO oxidation reaction, while bidentate formates are mainly spectators.

Graphical abstract: Stability of formate species on β-Ga2O3

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Publication details

The article was received on 10 Jan 2008, accepted on 25 Nov 2008, published on 19 Jan 2009 and first published online on 19 Jan 2009


Article type: Paper
DOI: 10.1039/B800519B
Citation: Phys. Chem. Chem. Phys., 2009,11, 1397-1405
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    Stability of formate species on β-Ga2O3

    M. Calatayud, S. E. Collins, M. A. Baltanás and A. L. Bonivardi, Phys. Chem. Chem. Phys., 2009, 11, 1397
    DOI: 10.1039/B800519B

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