CO adsorbed on the reduced Pt13/TiO2(110) catalyst

A. MALDONADO; G. F. CABEZA; S.B. RAMOS

La Plata

Workshop; IX Workshop Novel Methods for Electronic Structure Calculations; 2021

Facultad de Ciencias Exactas - Universidad Nacional de La Plata

Platinum subnanometer particles adsorbed on oxides like TiO2 (110) are known to play an important role in the CO oxidation process through the interaction of the CO molecule with a lattice oxygen to form CO2. The CO adsorption by a Pt13 cluster deposited on the reduced rutile TiO2(110) surface is here investigated by means of density functional theory calculations (DFT). Using the VASP [1] code we perform DFT calculations including the Hubbard term “U” to correct the coulombic interactions in the oxide, with the aim to provide relevant structural and energetic information of this cluster/substrate system. Previous studies using this methodology let us determine the equibrium configurations of isolated Pt13 clusters; we find that layered clusters are more stable with respect to more compact and symmetrical cubeoctahedral (Oh) and icosahedral (Ih) ones. However, when these compact isomers are adsorbed on the oxide surface they experience a strong restructuration, with the Pt cluster getting oxidated and adopting a more layered structure which increases the interaction with the substrate and a high adsorption energy [2,3]. A recent experimental study based on transmission electron microscopy performed for Pt clusters deposited on a graphite surface, detected Pt13 images in the form of a cuboid structure, consisting of a basic fcc cube, with a Pt atom missing at one corner [4]. In this work, we first analyze the stability of this new configuration observed experimentally, to evaluate its relative stability as compared to the layered and Oh structures of the isolated clusters, previously studied by us. Then, we characterize the cluster/substrate interaction for these isomers deposited on the reduced surface: TiO2 (110) plus an oxygen vacancy (TiO2+Vo), and compare with the previously studied Pt4-rutile system [5]. The last step is to study the adsorption of CO over the Pt13 cluster, in the different geometries considered, investigating the more favorable sites of adsorption of this molecule. We determine the equilibrium geometries, energies of adsorption, charge transfer effects and the electronic density of states, and discuss these results in connection with the possible oxidation of CO by an oxygen of the substrate. [1] G. Kresse, J. Furthmüller, Comput. Mater. Sci. 6, 15 (1996). [2] A. S. Maldonado, G. F. Cabeza, and S. B. Ramos. Journal of Physics and Chemistry of Solids 131, 131 (2019). [3] A. S. Maldonado, G. F. Cabeza, and S. B. Ramos. Topics in Catalysis 62, 989 (2019)