Unraveling the mechanisms of O 2 activation by size-selected gold clusters: Transition from superoxo to peroxo chemisorption

Rhitankar Pal, Lei Ming Wang, Yong Pei, Lai Sheng Wang, Xiao Cheng Zeng

Research output: Contribution to journalArticlepeer-review

115 Scopus citations

Abstract

The activation of dioxygen is a key step in CO oxidation catalyzed by gold nanoparticles. It is known that small gold cluster anions with even-numbered atoms can molecularly chemisorb O 2 via one-electron transfer from Au n - to O 2, whereas clusters with odd-numbered atoms are inert toward O 2. Here we report spectroscopic evidence of two modes of O 2 activation by the small even-sized Au n - clusters: superoxo and peroxo chemisorption. Photoelectron spectroscopy of O 2Au 8 - revealed two distinct isomers, which can be converted from one to the other depending on the reaction time. Ab initio calculations show that there are two close-lying molecular O 2-chemisorbed isomers for O 2Au 8 -: the lower energy isomer involves a peroxo-type binding of O 2 onto Au 8 -, while the superoxo chemisorption is a slightly higher energy isomer. The computed detachment transitions of the superoxo and peroxo species are in good agreement with the experimental observation. The current work shows that there is a superoxo to peroxo chemisorption transition of O 2 on gold clusters at Au 8 -: O 2Au n - (n = 2, 4, 6) involves superoxo binding and n = 10, 12, 14, 18 involves peroxo binding, whereas the superoxo binding re-emerges at n = 20 due to the high symmetry tetrahedral structure of Au 20, which has a very low electron affinity. Hence, the two-dimensional (2D) Au 8 - is the smallest anionic gold nanoparticle that prefers peroxo binding with O 2. At Au 12 -, although both 2D and 3D isomers coexist in the cluster beam, the 3D isomer prefers the peroxo binding with O 2.

Original languageEnglish (US)
Pages (from-to)9438-9445
Number of pages8
JournalJournal of the American Chemical Society
Volume134
Issue number22
DOIs
StatePublished - Jun 6 2012

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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