Reaction of Br2 with adsorbed CO on Pt, studied by the surface interrogation mode of scanning electrochemical microscopy

Qian Wang, Joaquín Rodríguez-López, Allen J. Bard

Research output: Contribution to journalArticlepeer-review

Abstract

(Chemical Equation Presented) Scanning electrochemical microscopy surface interrogation (SI-SECM) in the cyclic voltammetry mode was successfully used to detect and quantify adsorbed CO on a Pt electrode by reaction with electrogenerated Br2. The two-electrode setup used in this new technique allowed the production of Br2 on an interrogator tip, which reported a transient positive feedback above a Pt substrate at open circuit as an indication of the reactivity of this halogen with CO(ads). Br - and CO2 are shown to be the main products of the reaction (in the absence of O2), which may involve the formation of bromophosgene as a hydrolyzable intermediate. Under saturation conditions, CO(ads) was reproducibly quantified at the polycrystalline Pt surface with θCO ≈ 0.5. The reaction is shown to be blocked by the action of pre-adsorbed cyanide, which demonstrates the surface character of the process. The formation of CO2 as an end product was further tested in a bulk experiment: addition of Pt black to a mixture of Br2 in 0.5 M H2SO4 through which CO was bubbled gave a precipitate of BaCO3 in a saturated solution of Ba(OH)2. The use of SI-SECM allowed access to a reaction that would otherwise be difficult to prove through conventional electrochemistry on a single electrode.

Original languageEnglish (US)
Pages (from-to)17046-17047
Number of pages2
JournalJournal of the American Chemical Society
Volume131
Issue number47
DOIs
StatePublished - Dec 2 2009
Externally publishedYes

ASJC Scopus subject areas

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

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