A Spectroelectrochemical Flow Cell Setup for <i>Operando</i> ATR-SEIRAS Investigations Combined with Online Reaction Product Quantification

Attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is becoming a widely-used technique in electrocatalysis thanks to its ability to track surface species during electrochemical reactions, providing valuable insights into the dynamic behavior of reaction intermediates. Here, a new design of a spectroelectrochemical ATR-SEIRAS flow cell is presented, offering a thin (≈300 μm) electrolyte layer at the working electrode side to enhance mass transport (e.g., bubble detachment), coupled with a gas chromatograph, mass spectrometer, and a custom-made liquid distribution system for real-time analysis of gaseous and liquid reaction products. To test this setup, we studied the electrochemical CO 2 reduction reaction (CO 2 RR) on carbon-supported palladium nanoparticles by performing linear sweep voltammograms in CO 2 -saturated 0.1 M KHCO 3 . Thereby, we were able to monitor the formation and oxidative stripping of surface-adsorbed CO. Additionally, when performing potential holds in a range favorable for formate production (from −100 to −400 mV vs. the reversible hydrogen electrode), the progressive formation of this CO adsorption layer was found to correlate with the concomitant decrease in formate activity over time. Results emphasize the importance of combining time-resolved monitoring of the formation and depletion of surface intermediates with quantification of reaction products to gain a better understanding of catalytic mechanisms.