15 Feb 2021
15 Feb 2021
An Electrochemical cell for in operando 13C NMR investigations of carbon dioxide/carbonate processes in aqueous solution
- 1Forschungszentrum Jülich, Institute of Energy and Climate Research, Fundamental Electrochemistry (IEK-9), Jülich, Germany
- 2Forschungszentrum Jülich, Central Institute of Engineering and Analytics, Electronic Systems (ZEA-2), Jülich, Germany
- 3Department of Heterogeneous Reactions, Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
- 4RWTH Aachen University, Institute of Physical Chemistry, Aachen, Germany
- 5RWTH Aachen University, Institute of Technical and Macromolecular Chemistry, Aachen, Germany
- 1Forschungszentrum Jülich, Institute of Energy and Climate Research, Fundamental Electrochemistry (IEK-9), Jülich, Germany
- 2Forschungszentrum Jülich, Central Institute of Engineering and Analytics, Electronic Systems (ZEA-2), Jülich, Germany
- 3Department of Heterogeneous Reactions, Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
- 4RWTH Aachen University, Institute of Physical Chemistry, Aachen, Germany
- 5RWTH Aachen University, Institute of Technical and Macromolecular Chemistry, Aachen, Germany
Abstract. In operando NMR spectroscopy is a method for the online investigation of electrochemical systems and reactions. It allows a real-time observation of the formation of products and intermediates, and it grants insight into the interactions of substrate and catalyst. An in operando NMR setup for the investigation of the electrolytic reduction of CO2 on silver electrodes has been developed. The electrolysis cell consists of a three-electrode setup using a working electrode of pristine silver, a chlorinated silver wire as reference electrode, and a graphite counter electrode. The setup can be adjusted for the use of different electrode materials and fits inside a 5 mm NMR tube, Additionally, a shielding setup was employed to minimize noise caused by interference of external radio frequency (RF) waves with the conductive components of the setup. The electrochemical performance of the in operando electrolysis setup was investigated in comparison to a standard CO2 electrolysis cell. The small cell geometry impedes the release of gaseous products, and thus it is primarily suited for current densities below 1 mA/cm2. The effect of conductive components on 13C NMR experiments was studied using a CO2 saturated solution of aqueous bicarbonate electrolyte. Despite the B0 field distortions caused by the electrodes, line widths of ca. 1 Hz could be achieved. This enables the investigation of interactions in the sub-Hertz range by NMR spectroscopy. It was found that the dynamics of the bicarbonate electrolyte change due to interaction with the electrochemical setup, by catalyzing the exchange reaction between CO2 and HCO3− and affecting the formation of an electrical double layer.
Sven Jovanovic et al.
Status: open (until 20 Mar 2021)
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RC1: 'Comment on mr-2021-18', Anonymous Referee #1, 17 Feb 2021
reply
This is clearly a very challenging subject, to quantitatively characterize the evolution of 13 C NMR signals in the presence of conductive metals, electrochemical processes and various sources of noise and artifacts.
I believe, there are many unknowns left in this study, and questions raised by the authors in the manuscript need to be addressed and verified by them in a systematic manner., e.g., the relaxation measurement inconsistencies, unexpected CO2 signal decay during OCV and effects of bubbles on homogeneity and susceptibility.
If authors promote this cell design as an advantageous one, there should be a clear evidence of that in terms of quantitative data. I suggest a major revision, which should include troubleshooting addressing the questions raised by the authors, may be with the use of simplified cell design.
Assessment criteria during the full review:
The English needs to be improved quite a bit. A number of errors were noted and paper requires extensive proofreading… e.g. “Lorantzian line shape” – line 365;
What is ppb (line 368 ), did authors mean “ppm” or “part per billion” ? It is hard to see that from the spectra.
The units of concentration are M, or mM… (mmol/L would be mM, line 387);
Line 381: to use “was observed”.
Line 13: “dynamics of the bicarbonate electrolyte changes”
Line 35: “chemical and reaction analysis” … not clear wording... is it “chemical reaction analysis” ?
Line40: “Several experiment setups … were published”
Line 80: references should appear in chronological or alphabetic order.
Line91 to use: “A three-electrode electrolysis cell that fits a standard 5 mm NMR tube has been build.”
Define “iR” in the text.
Line 275: what is “small geometry” ? "compact design " ?
Line 298: “After introducing the …widths became..”
Kind regards
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AC1: 'Reply on RC1', Sven Jovanovic, 18 Feb 2021
reply
Dear reviewer,
thank you for your comments. We will address all the remarks, open questions and language in our revision.
Kind regards, Sven Jovanovic
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AC1: 'Reply on RC1', Sven Jovanovic, 18 Feb 2021
reply
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RC2: 'Comment on mr-2021-18', Anonymous Referee #1, 17 Feb 2021
reply
Assessment criteria during the full review
Does the paper address relevant scientific questions within the scope of MR?
YES
Does the paper present novel concepts, ideas, tools, or data? All submitted papers are assumed to report on new observations and/or new theory; there is no need to draw attention to the novelty in title, abstract, or conclusions.
YES
Are substantial conclusions reached?
No
Are the results sufficient to support the interpretations and conclusions?
No
Is the description of experiments and calculations sufficiently complete and precise to allow their reproduction by fellow scientists with reasonable effort?
YES
Are numerical data accompanied by error estimates with a description of the methods used to obtain these estimates?
No
For papers reporting molecular dynamics simulations, is it clearly stated how the MD simulations support the experimental evidence and vice versa?
N/A
Do the authors give proper credit to related work and clearly indicate their own new/original contribution?
YES
Does the title clearly reflect the contents of the paper?
YES
Does the abstract provide a concise and complete summary?
YES
Is the overall presentation well-structured and clear?
Is the language fluent and precise?
Yes
Should any parts of the paper (text, formulae, figures, tables) be clarified, reduced, combined, or eliminated?
YES (repetitive statements noticed).
Fig.4 needs to be more clearly presented.
Are the number and quality of references appropriate?
It appears, the number of references is excessive.
Is the amount and quality of the supporting information and supplementary material appropriate?
N/A
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AC2: 'Reply on RC2', Sven Jovanovic, 18 Feb 2021
reply
Dear reviewer,
we will adjust figure 4 for clarity in our revision.
Kind regards, Sven Jovanovic
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AC2: 'Reply on RC2', Sven Jovanovic, 18 Feb 2021
reply
Sven Jovanovic et al.
Sven Jovanovic et al.
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