Properties of Isolated and TiO₂(110) Supported Pt₁₃ Clusters: A Theoretical Study

Metallic subnanoparticles deposited over supports such as TiO₂ play an important role for the design of model catalysts for heterogeneous catalysis applications. In this work we study the structure and energetic of Pt₁₃ clusters deposited on TiO₂(110) surfaces, using an ab initio DFT + U modeling method. We first examine the structural and dynamical stability of the isolated Pt₁₃ nanoclusters by considering as initial configurations symmetrical Ih and Oh structures and new layered isomers. We determine their equilibrium geometries, cohesive energies, magnetic moments, electronic and vibrational density of states. The analysis of the vibrational modes reveal that the Oh and Ih structures are dynamically unstable unlike the layered structures that have lower energies. We then examine the Pt₁₃-titania system to characterize the cluster/substrate interaction for both the stoichiometric and reduced surfaces. We characterize different aspects of the metal-oxide interaction by determining their equilibrium geometries, adsorption energies, charge transfer effects and electronic density of states. We find that the Pt₁₃ cluster suffers a strong restructuration when adsorbed on the surface, it deforms towards increasing the interaction of the platinum atoms with the surface, leading to a high value of the adsorption energy and getting oxidized. The Pt₁₃-rutile system is semiconductor; for the stoichiometric system a localized state in the band gap is predicted. The calculated surface oxygen vacancy formation energy is prefered by the cluster deposition as a fact that favours the use of this system in the CO oxidation reactions from a surface oxygen, an important step in the water gas shift reaction.