Size dependent electronic, structural and catalytic properties of nanostructured supported metal oxide clusters

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One of the most important applications of nanoparticles / clusters is that of heterogeneous catalysis, for which the large surface-to-volume ration can be exploited. Most often, the clusters are then deposited on some substrate, which makes detailed theoretical and/or experimental studies of the details of the catalytic reactions very difficult. One of the most important classes of catalytic reactions is the oxidation of some system. For those reactions, it can be of advantage to use metal oxides as catalysts.The goal of the proposed project is to develop an atomistic understanding of a simple model reaction, the oxidation of CO. As catalysts, titanium and vanadium oxide clusters will be studied that in turn are deposited on either graphene or silica. Different M(x)O(y) clusters with N = x+y up to around 50 shall be studied. Both stoichiometric clusters (y/x = 2 for M = Ti, y/x = 2.5 for M = V) as well as near-stoichiometric either O rich or O poor shall be studied. The first challenge will be to determine the structures of the clusters. To this end, we shall apply the unbiased methods that we have been used for isolated nanoparticles in the gas phase since several years. As one approach we shall use exactly those methods for the particles in the gas phase that subsequently shall be deposited on the substrate. As an alternative we shall determine the optimal structures for such clusters when created directly on the substrate.Subsequently, we shall study the oxidation of CO. This part shall be done in close collaboration with an Indian colleague, Dr. Neetu Goel, whose experience will be of great benefit to the project. Since several years she has been working on theoretical studies of the catalysis, an experience that in excellent way complements our own. The catalytic reaction shall be studied for different types of catalysts: isolated clusters in the gas phase, such clusters deposited on the substrate, and clusters grown directly on the substrate.The project is expected to address the following issues: does oxygen of the metal oxide clusters play an active role in the catalytic reaction, are stoichiometric or near-stoichiometric (oxygen-poor or -rich) clusters the better catalysts, how important are the substrates for the catalytic reaction.