Volatile Hydrogen Intermediates of CO₂ Methanation by Inelastic Neutron Scattering

Round 1

Reviewer 1 Report

This is a very good paper that describes the details of CO2 methanation on catalysts and characterization of the process using complimentary techniques. The motivation, theory, methods and results are well described and significant results are presented. For the lead-in with DRIFTS, I was expecting to see some INS results from deuterated samples as well. Perhaps the authors could provide more information as to why it was not necessary to perform INS on deuterated samples. Overall, the results and conclusions are sound and provide new insights into the catalytic behavior.

Listed below are some edits that the authors may consider in the final version.

Line 14: research efforts

18: but is restricted

23: C-based article

24: a result that needs…

30: nanometers to millimeters

107: replace living with lived

194: replace falsify with refute

215: H-methanation

235: replace “At the same” with Similarly

239: replace “reflecting electrons” with “reflection electron”

277-284: the figure caption is too long…these lines should be places in the text at the end of line 273.

Line 308: A disadvantage of ….

Author Response

We thank the reviewer for her/his kind comments. His/her question is very valid, as the labelling of hydrogen containing compounds by deuterium can give meaningful insights. However, deuterium has a considerably lower neutron incoherent cross section coefficient (σ_tot (D) = 2 barn) than hydrogen (80 barn) and even than Ni (5 barn). Thus in addition to the worsened signal to noise ratio, the hydrogen selectivity of inelastic neutron scattering (INS) is practically lost. As INS is a very time-consuming method (each spectrum is several hours), we did not run INS experiments on deuterium exchanged samples.

We corrected the various typos (to be uploaded once finally accepted). We hope that with this the manuscript is acceptable in the present form.

Sincerely

On behalf of the co-authors

Andreas Borgschulte

Reviewer 2 Report

It is interesting that the combination of DRIFTS and INS techniques allows us to discuss possible adsorbed species as reaction intermediates that cannot be obtained by infrared spectroscopy alone. Although INS is not actually OPERANDO, the concept of quenched-OPERANDO proposed by the authors is expected to further be improved in the future. The results in this study, which indicate –H and -O adsorbed species during CO2 methanation over Ni catalyst, is valuable and may give important information to relating fields. I consider this article worthy of being published in this journal.

Author Response

We thank the reviewer for her/his kind comments. The manuscript was partially written, commented and proof read by an experienced native English speaker. We hope it is acceptable in the current form (to be uploaded later).

Sincerely

On behalf of all authors

Andreas Borgschulte