Influence of hydroxyls on Pd atom mobility and clustering on rutile TiO2(011)-2 × 1

Rafik Addou, Thomas P. Senftle, Nolan O'Connor, Michael John Janik, Adri Van Duin, Matthias Batzill

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Understanding agglomeration of late transition metal atoms, such as Pd, on metal oxide supports, such as TiO2, is critical for designing heterogeneous catalysts as well as for controlling metal/oxide interfaces in general. One approach for reducing particle sintering is to modify the metal oxide surface with hydroxyls that decrease adatom mobility. We study by scanning tunneling microscopy experiments, density functional theory (DFT) calculations, and Monte Carlo (MC) computer simulations the atomistic processes of Pd sintering on a hydroxyl-modified TiO2(011)-2 × 1 surface. The formation of small 1-3 atom clusters that are stable at room temperature is achieved on the hydroxylated surface, while much larger clusters are formed under the same conditions on a hydroxyl-free surface. DFT shows that this is a consequence of stronger binding of Pd atoms adjacent to hydroxyls and increased surface diffusion barriers for Pd atoms on the hydroxylated surface. DFT, kinetic MC, and ReaxFF-based NVT-MC simulations show that Pd clusters larger than single Pd monomers can adsorb the hydrogen from the oxide surface and form Pd hydrides. This depletes the surface hydroxyl coverage, thus allowing Pd to more freely diffuse and agglomerate at room temperature. Experimentally, this causes a bimodal cluster size distribution with 1-3 atom clusters prevalent at low Pd coverage, while significantly larger clusters become dominant at higher Pd concentrations. This study demonstrates that hydroxylated oxide surfaces can significantly reduce Pd cluster sizes, thus enabling the preparation of surfaces populated with metal clusters composed of single to few atoms.

Original languageEnglish (US)
Pages (from-to)6321-6333
Number of pages13
JournalACS Nano
Volume8
Issue number6
DOIs
StatePublished - Jun 24 2014

Fingerprint

rutile
Hydroxyl Radical
Atoms
atoms
Oxides
Metals
Density functional theory
metal oxides
density functional theory
sintering
Sintering
titanium dioxide
Adatoms
oxides
Diffusion barriers
Surface diffusion
Scanning tunneling microscopy
room temperature
metal clusters
surface diffusion

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Materials Science(all)
  • Physics and Astronomy(all)

Cite this

Addou, Rafik ; Senftle, Thomas P. ; O'Connor, Nolan ; Janik, Michael John ; Van Duin, Adri ; Batzill, Matthias. / Influence of hydroxyls on Pd atom mobility and clustering on rutile TiO2(011)-2 × 1. In: ACS Nano. 2014 ; Vol. 8, No. 6. pp. 6321-6333.
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Influence of hydroxyls on Pd atom mobility and clustering on rutile TiO2(011)-2 × 1. / Addou, Rafik; Senftle, Thomas P.; O'Connor, Nolan; Janik, Michael John; Van Duin, Adri; Batzill, Matthias.

In: ACS Nano, Vol. 8, No. 6, 24.06.2014, p. 6321-6333.

Research output: Contribution to journalArticle

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