PROBIEN   20416
INSTITUTO DE INVESTIGACION Y DESARROLLO EN INGENIERIA DE PROCESOS, BIOTECNOLOGIA Y ENERGIAS ALTERNATIVAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Ab initio study of Pt clusters on TiO2 (110)
Autor/es:
A. MALDONADO; S.B. RAMOS; C.I.N. MORGADE; G. F. CABEZA
Lugar:
La Plata
Reunión:
Workshop; VI Workshop on Novel Methods for Electronic Structure Calculations; 2015
Institución organizadora:
Departamento de Electrotecnia - Universidad Nacional de La Plata
Resumen:
TiO2is a widely used material due to its electronic and catalytic properties, whichare of interest for technological applications. In catalysis it is generallyused as support for different catalyzers, such as for example Pt, which isimportant for the water shift reaction (WSR) for H2 production [1]. Dueto the high catalytic activity of Pt nanoclusters (NCs), they are placed overTiO2 in search for improving the sensibility of the material.In this workwe use an ab initio modeling method based on the DFT+U, previously used [2], toinvestigate the structural, cohesive and magnetism of Pt4, withplanar and tetrahedral geometries, and Pt13 with octahedral symmetrydeposited over (110) of TiO2 in its rutile phase. We use theprojected augmented wave (PAW) method and the Vasp code [3], combined withexchange and correlation functions. We determine the equilibrium structure, energyof adsorption, charge transfer effects and electronic density of states, tocharacterize different aspects of the metal-oxide interaction. We evaluate therelative stability of both isolated and supported geometries over the surface,the electronic densities and charge transfer effects, comparing with previoustheoretical results [4]. For the isolated Pt4 cluster thetetrahedral geometry is more stable than the planar one. However when depositedover TiO2 the relative stability is reversed; this effect iscorrelated with the higher number of Pt-Ti bonds that tend to stabilize thesystem. This result is in good agreement with Jiang et al. [4] who used a similarstudy based on exchange and correlation potentials of the type PBE. However, animportant difference is observed for the electronic behavior; according to [4]the system Pt4/TiO2 is semiconductor, while our resultsindicate that the system has metallic character. In our case the use of XCpotential of the type PBE + U let us correctly treat the gap for TiO2(110),and therefore better results are expected.Besides,our results for Pt4/TiO2 are also in line with theexperimental observations of Watanabe etal. [5], who find planar configurations for clusters with sizes lower than7. For Pt13/TiO2, our results predict a strongrestructuration of the cluster, that evolves from an initial octahedralconfiguration, to a more disordered configuration in more contact to thesurface in the sense of increasing the Pt-Ti bonds. References[1] C. Vignatti, M. Avila, C. Apesteguía, T. Garetto,Inter. J. of Hyd. Energy 35 (2010) 7302.[2]C. I. N. Morgade, Ch. I. Vignatti, M. S. Avila, G. F. Cabeza, J. of Mol. Cat.A: Chemical 407 (2015) 102.[3] G.Kresse, J. Joubert, Phys. Rev. B 59 (1999) 1758.[4]D. Jiang, S. H. Overbury, Sheng Dai, J. Phys. Chem. C 116 (2012) 21880.[5]Y. Watanabe, X. Wu, H. Hirata and N. Isomura, Catal. Sci. Technol. 1(2015) 1490.