Influence of adsorbates on the electronic structure, bond strain, and thermal properties of an alumina-supported pt catalyst

Matthew W. Small, Sergio I. Sanchez, Nebojsa S. Marinkovic, Anatoly I. Frenkel, Ralph G. Nuzzo

Research output: Contribution to journalArticlepeer-review

Abstract

Figure Persented: We describe the results of an X-ray absorption spectroscopy (XAS) study of adsorbate and temperature-dependent alterations of the atomic level structure of a prototypical, noble metal hydrogenation and reforming catalyst: ∼1.0 nm Pt clusters supported on gamma alumina (Pt/γ-Al 2O 3). This work demonstrates that the metal-metal (M-M) bonding in these small clusters is responsive to the presence of adsorbates, exhibiting pronounced coverage-dependent strains in the clusters' M-M bonding, with concomitant modifications of their electronic structures. Hydrogen and CO adsorbates demonstrate coverage-dependent bonding that leads to relaxation of the M-M bond strains within the clusters. These influences are partially compensated, and variably mediated, by the temperature-dependent electronic perturbations that arise from cluster-support and adsorbate-support interactions. Taken together, the data reveal a strikingly fluxional system with implications for understanding the energetics of catalysis. We estimate that a 9.1 ± 1.1 kJ/mol strain exists for these clusters under H 2 and that this strain increases to 12.8 ± 1.7 kJ/mol under CO. This change in the energy of the particle is in addition to the different heats of adsorption for each gas (64 ± 3 and 126 ± 2 kJ/mol for H 2 and CO, respectively).

Original languageEnglish (US)
Pages (from-to)5583-5595
Number of pages13
JournalACS Nano
Volume6
Issue number6
DOIs
StatePublished - Jun 26 2012

Keywords

  • γ- Al O
  • carbon monoxide
  • catalyst
  • hydrogen
  • nanoparticle
  • platinum
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

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

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