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O: Fachverband Oberflächenphysik

O 60: Solid-Liquid Interfaces I: Structure and Spectroscopy

O 60.7: Talk

Wednesday, March 29, 2023, 16:30–16:45, TRE Phy

Influence of Interfacial Water and Cations on the Oxidation of CO at the Platinum/Ionic Liquid Interface — •Björn Ratschmeier, Gina Ross, Andre Kemna, and Björn Braunschweig — University Münster, Institute of Physical Chemistry, Münster, Germany

CO oxidation is fundamental key for complete oxidation of small alcohols on Pt catalysts in fuel cells. So far, room-temperature ionic liquids (RTIL) have been used to modify the selectivity in electrocatalysis. In order to understand the mechanism of CO oxidation in RTIL we have investigated this reaction at the Pt(111)/1-butyl-3-methylimidazolium trifluorosulfonylimide [BMIM][NTf2] electrode/electrolyte interface as a function of H2O concentration and electrode potential using in situ sum-frequency generation (SFG) spectroscopy and infrared absorption spectroscopy (IRAS). Using SFG spectroscopy, we address the changes of CO molecules on Pt(111), while we monitor bulk electrolyte changes with IRAS using vibrational bands from H2O, CO2 and CO. The presence of water in [BMIM][NTf2] shifts the CO onset potential by more than 200 mV with increased H2O concentration from 0.01 to 1.5 M, which we relate to the incorporation and availability of water at the electrode/electrolyte interface. The nature of the RTIL cation has also a large effect on the surface excess of H2O since RTILs which are prone to form closed-packed structures like [BMMIM][NTf2] can block the incorporation of H2O and lead to more sluggish CO oxidation with larger overpotentials and oxidation in a much broader potential.