Clusters and Catalysis
This project is driven by the vision of computational design of cluster-based nanocatalysts. The discovery of the extraordinary activity in catalysis exhibited by small metal-oxide clusters has stimulated considerable research interest to understand the origin of this unusual behavior. It has been found that reducing the number of particles in a cluster reveals the possibility of several interesting size effects. In a range where matter is reduced to sizes of only a few atoms, the intrinsic properties of the so-called clusters are non-scalable from their bulk analogues. Clusters exhibit significant variations as a function of size in their physicochemical nature and electronic properties viz. ionization potentials, electronic affinities, hardness, softness, magnetic moments, and catalytic reactivity. Transition-metal (TM) nanoparticles/clusters are widely used as catalysts for a variety of important chemical processes for the efficient production of value-added commodities. Tailoring novel catalyst with a high degree of selectivity, reactivity, and stability is a subject of considerable current interest. Despite significant efforts, the evolving field of heterogeneous catalysis demands the accurate description of all the (meta-)stable structures of catalysts materials under operational conditions. In the presence of a realistic reactive atmosphere, clusters change their stoichiometry by adsorbing the ligands from the environment, under certain conditions. This new composition may work as active (functional) material. Therefore, one has to understand the functional properties of clusters in a technologically relevant atmosphere. Here, stability is a key element for the desired functioning of any real catalyst. It is a prerequisite to know the most stable phase of a catalyst in a gas phase environment of reactants. Moreover, the nano-particles, containing two or more transition or other metals, tremendously increase the possibilities for tuning the catalytic properties. Together with these possibilities, new challenges arise for the design of more efficient and stable nano-catalysts. In particular, due to the increased complexity, the atomic structure and stability of the nanoparticles are harder to determine. Therefore, it is important to provide theoretical guidance to experiment and technology on the composition and atomic structure of both the catalyst and the reaction intermediates in a reactive atmosphere, in particular in the ubiquitous presence of an additional ligands (in most of the cases it’s oxygen).