In‐Situ Infrared Spectroscopy Applied to the Study of the Electrocatalytic Reduction of CO₂: Theory, Practice and Challenges

Abstract

The field of electrochemical CO2 conversion is undergoing significant growth in terms of the number of publications and worldwide research groups involved. Despite improvements of the catalytic performance, the complex reaction mechanisms and solution chemistry of CO2 have resulted in a considerable amount of discrepancies between theoretical and experimental studies. A clear identification of the reaction mechanism and the catalytic sites are of key importance in order to allow for a qualitative breakthrough and, from an experimental perspective, calls for the use of in‐situ or operando spectroscopic techniques. In‐situ infrared spectroscopy can provide information on the nature of intermediate species and products in real time and, in some cases, with relatively high time resolution. In this contribution, we review key theoretical aspects of infrared reflection spectroscopy, followed by considerations of practical implementation. Finally, recent applications to the electrocatalytic reduction of CO2 are reviewed, including challenges associated with the detection of reaction intermediates.

Electrochemical CO2 reduction on nanostructured metal electrodes: fact or defect?

“…Ex situ or preferably in situ spectroscopic methods such as surface enhanced infrared and Raman spectroscopy might be necessary to elucidate the structure of the thin carbon layer formed on the electrode surface during electrolysis. 33 Surface re-construction or changes in the morphology as a result of oxide reduction, dissolution and re-deposition might alter the selectivity towards CO 2 reduction products or hydrogen. 34,35 Further, the selectivity changes might occur at the very early stage of the electrolysis or can span hours.…”

In-situ Spectroscopic Techniques as Critical Evaluation Tools for Electrochemical Carbon dioxide Reduction: A Mini Review

“…This work provided important insights into the molecular pathway of CO 2 RR on Cu surfaces. Kas et al summarized that in-situ IR techniques are vital probing techniques to expound the reaction mechanisms of chemical and electrochemical CO 2 RR, as the technique can provide extremely valuable information on the nature of reaction intermediates, the significance of double layer effects in manipulating the activity and selectivity, and the nature of the species causing deactivation of the electrocatalysts (Kas et al, 2019). In addition to the above IR-based techniques, the intermediates of CO 2 RR have also been probed using insitu techniques such as surface-enhanced Raman spectroscopy (SERS) and UV-Vis absorption.…”

Versatile Spectroelectrochemical Cell for In Situ Experiments: Development, Applications, and Electrochemical Behavior**

“…Particularly interesting for this cell are electrodes embedded in PTFE or PEEK, as the electrochemical response will come only from the noncovered part at the top of the electrode (it will be thoroughly discussed in the next sections). Vitreous carbon electrodes, which are relatively inert for several applications, are useful as a 7; chamber for the electrolyte, the CE and the RE (8); electrolyte inlet and outlet (9,11,13), WE inlet (10); RE inlet (12); RE (14); CE inlet (15); bolt (18); SEC body -part 2 (19); WE (20). support of a myriad of electroactive materials, for example, nanoparticles made of metals or semiconductors.…”

“…For details about the technique we refer the reader to the vast specialized literature in this field. [18][19][20] Thus, to perform this measurement we must insert a suitable window in our SEC (CaF 2 , ZnSe, etc.) and set it upside-down on the Specular Reflectance Accessory.…”

“…However, unfortunately, the ATR configurations have others limitations that make this approach much less versatile. [19] In Situ RAMAN Figure 3 shows the SEC positioned close to the objective lenses of a Raman microscope. Again, the same SEC used for FTIR in figure 2 was used in this measurement.…”