Probing Molecular-Scale Catalytic Interactions between Oxygen and Cobalt Phthalocyanine Using Tip-Enhanced Raman Spectroscopy

Duc Nguyen, Gyeongwon Kang, Naihao Chiang, Xu Chen, Tamar Seideman, Mark C. Hersam, George C. Schatz, Richard P. Van Duyne

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) is used to investigate adsorption of molecular oxygen (O2) on cobalt(II) phthalocyanine (CoPc) supported on Ag(111) single crystal surfaces, which is the initial step for the oxygen reduction reaction (ORR) using metal Pc catalysts. Two adsorption configurations are primarily observed, assigned as O2/CoPc/Ag(111) and O/CoPc/Ag(111) based on scanning tunneling microscopy (STM) imaging, TERS, isotopologue substitution, and density functional theory (DFT) calculations. Distinct vibrational features are observed for different adsorption configurations such as the 18O-18O stretching frequency at 1151 cm-1 for O2/CoPc/Ag(111), and Co-16O and Co-18O vibrational frequencies at 661 and 623 cm-1, respectively, for O/CoPc/Ag(111). DFT calculations show vibrational mode coupling of O-O and Co-O vibrations to the Pc ring, resulting in different symmetries of oxygen-related normal modes. This study establishes UHV-TERS as a chemically sensitive tool for probing catalytic systems at the molecular scale.

Original languageEnglish
Pages (from-to)5948-5954
Number of pages7
JournalJournal of the American Chemical Society
Volume140
Issue number18
DOIs
Publication statusPublished - May 9 2018

ASJC Scopus subject areas

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

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