Subnanometer palladium particles synthesized by atomic layer deposition

Hao Feng, Joseph A. Libera, Peter C. Stair, Jeffrey T. Miller, Jeffrey W. Elam

Research output: Contribution to journalArticle

72 Citations (Scopus)

Abstract

Monodispersed palladium nanoparticle catalysts were synthesized by atomic layer deposition (ALD) using alternating exposures of Pd hexafluoroacetylacetonate (Pd(hfac)2) and formalin on an alumina support. The size of the ALD Pd particles could be tuned by adjusting the preparation conditions. Conventional ALD conditions produced Pd particles with an average size of 1.4 nm. Removal of surface hydroxyls from the alumina support by a chemical treatment using trimethyl aluminum (TMA) before performing Pd ALD led to nanoparticles larger than 2 nm. Ultrasmall (subnanometer) Pd particles were synthesized using low-temperature metal precursor exposures, followed by applying protective ALD alumina overcoats. The ALD Pd particles were characterized by transmission electron microscopy, extended X-ray absorption fine structure, and diffuse reflectance infrared Fourier transform spectroscopy techniques. The Pd loadings were measured by X-ray fluorescence. The catalytic performance of ALD Pd particles of different sizes was compared in the methanol decomposition reaction. The specific activity (normalized by Pd loading) of the ultrasmall Pd particles was higher than those of the larger particles. Considering the metal dispersion factor, the turnover frequency (TOF) of the ultrasmall Pd particles is comparable to that of the medium-sized (1.4 nm, on average) Pd particles synthesized under standard ALD conditions. The large Pd particles (>2 nm) are a factor of 2 less active than the smaller Pd particles.

Original languageEnglish
Pages (from-to)665-673
Number of pages9
JournalACS Catalysis
Volume1
Issue number6
DOIs
Publication statusPublished - Jun 3 2011

    Fingerprint

Keywords

  • atomic layer deposition (ALD)
  • nanoparticle catalyst
  • palladium (Pd) particles

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Cite this