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 language | English (US) |
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Pages (from-to) | 5948-5954 |
Number of pages | 7 |
Journal | Journal of the American Chemical Society |
Volume | 140 |
Issue number | 18 |
DOIs | |
State | Published - May 9 2018 |
Funding
D.N., N.C, G.C.S, and R.P.V.D. acknowledge support from the National Science Foundation Center for Chemical Innovation dedicated to Chemistry at the Space-Time Limit (CaSTL) Grant CHE-1414466. D.N., G.K., X.C., G.C.S, and R.P.V.D. acknowledge support from the Air Force Office of Scientific Research MURI (FA9550-14-1-0003). G.K. and G.C.S. acknowledge support from Northwestern University Information Technology (NUIT) team and the Center for Nanoscale Materials (CNM) at Argonne National Laboratory for the computational resources. N.C., T.S., M.C.H., and R.P.V.D. acknowledge support from the National Science Foundation Materials Research Science and Engineering Center (NSF Grant DMR-1121262).
ASJC Scopus subject areas
- Catalysis
- General Chemistry
- Biochemistry
- Colloid and Surface Chemistry