A theoretical analysis of small Pt particles on rutile TiO$_2$(110) surfaces

TL;DR

This study uses advanced DFT+U calculations to analyze how small platinum clusters interact with different types of rutile TiO2(110) surfaces, revealing effects on electronic structure and surface relaxation.

Contribution

It provides a systematic theoretical analysis of Pt clusters on various TiO2 surfaces, highlighting the importance of surface stoichiometry and electronic correlation effects.

Findings

Pt clusters distort on reduced surfaces with oxygen vacancies.

Adsorption induces band gap narrowing or widening depending on surface type.

No metallization occurs even with Pt4 clusters on rutile.

Abstract

The adsorption profiles and electronic structures of Pt$_n$ (n = 1--4) clusters on stoichiometric, reduced and reconstructed rutile TiO$_2$(110) surfaces were systematically studied using on site d-d Coulomb interaction corrected hybrid density functional theory calculations. The atomic structure of small Pt cluster adsorbates mainly depend on the stoichiometry of the corresponding titania support. The cluster shapes on the bulk terminated ideal surface look like their gas phase low energy structures. However, for instance, they get significantly distorted on the reduced surfaces with increasing oxygen vacancies. On non-stoichiometric surfaces, Pt--Ti coordination becomes dominant in the determination of the adsorption geometries. The electronic structure of Pt$_n$/TiO$_2$(110) systems can not be correctly described by pure DFT methods, particularly for non-stoichiometric cases, due to the inappropriate treatment of the correlation for $d$ electrons. We performed DFT+U calculations to give a reasonable description of the reconstructed rutile (110) surface. Pt clusters induce local surface relaxations that influence band edges of titania support, and bring a number of band-gap states depending on the cluster size. Significant band gap narrowing occurs upon Pt$_n$--surface interaction due to adsorbate driven states on the bulk terminated and reduced surfaces. On the other hand, they give rise to a band gap widening associated to partial reoxidation of the reconstructed surface. No metallization arises even for Pt$_4$ on rutile.