Electrochemical reactions require specialized devices to facilitate specific chemical processes. However, researchers often face significant challenges in device development due to the unpredictable performance of materials. While these materials may exhibit ideal properties in controlled laboratory settings, their behavior often differs when integrated into an actual device.
To tackle this issue, there is a growing emphasis on in operando measurements, aiming to replicate actual operating conditions. However, conducting these measurements using standard spectroscopic and analytic techniques can be difficult due to compatibility issues between sample delivery systems and measurement instruments. Thus, the development of special cells and devices is often necessary to enable a wide range of analytical measurements.
Recent progress includes the development of a novel in operando NMR spectroscopy approach, specifically applied to studying the electrolytic reduction of carbon dioxide CO2) on silver electrodes.1 This technique, known for identifying chemical species, has proven valuable. Utilizing the in operando cell, researchers were able to closely observe and identify products and intermediates in the catalytic cycle, marking a significant advancement in electrochemical research.
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Importance of CO2 Reduction
Given the role of CO2 production in driving anthropogenic climate change, there is a growing need to explore methods for reducing CO2 emissions and developing innovative approaches to utilize CO2 as a chemical feedstock.2 Many are concerned that, despite many positive actions taken by governments and individuals to minimize CO2 emissions, there are still a number of socioeconomic factors that are hindering global CO2 reduction efforts.3
For instance, many chemical manufacturing processes still rely on petrochemical feedstocks for starting materials. However, several demonstrations have showcased the use of CO2 as a starting material for producing hydrocarbons and alcohols.4 Typically, these transformations are facilitated using a bicarbonate electrode. Additionally, various potential reduction reactions, such as those generating CO, utilize silver or gold electrodes.
Enhancing the efficiency of CO2 reduction on a larger scale necessitates a thorough understanding of all the steps involved in the reduction process, especailly considering that the process of CO2 electrochemical reduction is exceptionally intricate and extremely sensitive to environmental factors like species concentration, pH, and temperature.
Methodology
In addressing the challenges posed by electrochemical CO2 reduction, the aforementioned study focused on leveraging the distinct chemical signatures of the products and intermediates identifiable through NMR analysis. However, conducting in operando 13C NMR measurements presented a unique obstacle: the radio fields necessary for NMR interfered with the fields within the electrochemical cells.
To overcome this hurdle, the research team needed to design a novel electrochemical cell that would be small enough to fit into the NMR coil on the instrument. Their innovative solution comprised a three-electrode system, which fit snuggly into a standard 5 mm NMR tube.
To assess the cell's functionality, the team conducted experiments using CO2 in 1 M KHCO3 solution with and without the use of the electrochemical setup. A crucial aspect of their development was the integration of shielding mechanisms, vital to preventing disruption of NMR fields and distortion of NMR spectra resulting from the interaction between the cell-generated fields and the instrumentation. Notably, silver and silver chloride electrodes played pivotal roles in this experimental setup.
Conclusions
The study successfully showcased the effectiveness of their innovative electrochemical cells, demonstrating comparable measurement quality to those obtained from bulk cells. While slight discrepancies in behavior between cell types were observed, these variances were linked to inhomogeneities in potential between the electrodes.
Crucially, the research pinpointed that specific potential drops create spatially favorable zones for electrolysis, enabling more efficient CO2 reduction. This finding suggests promising avenues for further exploration. By harnessing a tailored electrode design, these identified reaction conditions could potentially be leveraged to enhance the efficiency of CO2 reduction processes.
Bruker Biospin's advanced NMR instruments and software played a vital role in enabling these measurements. For more information on how these tools can enhance research, contact Bruker Biospin today.
References and Further Reading
- Jovanovic, S., Schleker, P., Streun, M., Merz, S., & Jakes, P. (2021). An Electrochemical cell for in operando 13 C NMR investigations of carbon dioxide / carbonate processes in aqueous solution. Magnetic Resonance Discussion, 1–24.
- Liu, D., Shadike, Z., Lin, R., Qian, K., Li, H., Li, K., ... & Li, B. (2019). Review of recent development of in situ/operando characterization techniques for lithium battery research. Advanced Materials, 31(28), 1806620. https://doi.org/10.1002/adma.201806620
- Rockstrom, J., Steffen, W., Noone, K., Persson, A., III, F. S. C., Lambin, E. F., Lenton, T. M., Scheffer, M., Folk, C., Schnellnhuber, H. J., Nykvist, B., Wit, C. A. de, Hughers, T., Leeuw, S. van der, Rodhe, H., Sorlin, S., Snyder, P. k., Constanza, R., Svedin, U., … Foley, J. A. (2009). A safe operating space for humanity. Nature, 461, 472–475. https://doi.org/10.1038/461472a
- Grundmann, R. (2016). Climate change as a wicked social problem. Nature Geoscience, 9, 562-563. https://doi.org/10.1038/ngeo2780
- Hori, Y. I. (2008). Electrochemical CO2 reduction on metal electrodes. Modern aspects of electrochemistry, 89-189. https://doi.org/10.1007/978-0-387-49489-0_3
This information has been sourced, reviewed and adapted from materials provided by Bruker BioSpin - NMR, EPR and Imaging.
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