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O: Fachverband Oberflächenphysik

O 84: Poster Session - Solid-Liquid Interfaces: Reactions and Electrochemisty

O 84.6: Poster

Mittwoch, 18. März 2020, 18:15–20:00, P2/EG

Effects of H2O on CO2 Electroreduction Reactions at Platinum/Imidazolium Based Ionic Liquid Interfaces — •Björn Ratschmeier, Andre Kemna, and Björn Braunschweig — Institute of Physical Chemistry, Münster, Germany

CO2 reduction reactions (CO2RR), which are interesting for power-to-x applications, have been studied on polycrystalline Pt electrodes in the following room-temperature ionic liquids (RTIL): [EMIM][DCA], [EMIM][BF4] and [OMIM][BF4]. Because water can play an important role as cosolvent and coreactant, we have addressed CO2RR as a function of water concentration. Cyclic voltammetry (CV) indicates a strong rise of activity for CO2RR when the water concentration was increased. In order to provide molecular-level details, we have additionally applied in operando IR Absorption spectroscopy (IRAS) to reveal reaction products in the bulk electrolyte and in situ vibrational sum-frequency generation (SFG) to address surface-adsorbed species. From IRAS, we show that the formation of a imidazolium-COOH intermediate takes place at electrode potentials of -0.9 V vs SHE when the water concentration was as low as 31 mM, but is shifted to lower overpotentials at 1 M H2O for all studied ionic liquids. In addition, SFG spectroscopy provides clear evidence for the formation of CO on Pt atop surface sites, which was used to determine the onset potential for the formation of CO. While in [OMIM][BF4] no CO is formed even at very low potentials of -1.5 V, a significant decrease of the onset potential for CO formation with increasing water concentration is seen for the other RTIL.