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O: Fachverband Oberflächenphysik

O 67: Solid-Liquid Interfaces III: OER, ORR, CO2RR, etc.

O 67.10: Vortrag

Mittwoch, 18. März 2020, 13:00–13:15, WIL C107

In Operando Spectroscopy of CO2 Reduction Reactions at Pt/Ionic Liquid Interfaces — •Andre Kemna, Björn Ratschmeier, and Björn Braunschweig — Institute of Physical Chemistry, WWU Münster, 48149 Münster, Germany

CO2 reduction reactions (CO2RR) at Pt(poly)/[BMIM][BF4] interfaces were studied with cyclic voltammetry and in operando with IR absorption (IRAS) as well as sum frequency generation (SFG) spectroscopy to get mechanistic insights into CO2RR. IRAS revealed a vibrational band centered at 1670 cm^-1 at an onset potential of -0.65V vs SHE. We attribute the latter to the carbonyl stretching mode of an imidazolium carboxylic acid, which is generated via a carbene intermediate, for which we also present spectroscopic evidence. Via SFG spectroscopy we demonstrates that CO is formed in addition to [BMIM]-COOH on the Pt catalyst surface, at an onset potentials of -1.05 V. We therefore assume that the [BMIM]-COOH species is one reactive intermediate that results in low overpotentials for CO2RRs. The [BMIM]-COOH species can be further catalyzed to formic acid during an anodic potential sweep. At an electrode potential of 1.6 V, a vibrational band at 1750 cm^-1 arises in the IR spectra and is accompanied by a decrease of the imidazolium carboxylate band. We tentatively assign the former vibrational modes to C=O vibrations of formic acid. This indicates that electrocatalysis of CO2 to formic acid may be possible in a two-step reaction process.
A. Kemna, N. García Rey, B. Braunschweig, ACS Catal. 2019, 9, 7, 6284-6292.