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Detection of catalytic intermediates at an electrode surface during carbon dioxide reduction by an earth-abundant catalyst


The electrocatalytic reduction of CO2 offers a sustainable route to the many carbon fuels and feedstocks that society relies on. [fac-Mn(bpy)(CO)3Br] (bpy, 2,2-bipyridine) is one of the most promising and intensely studied CO2 reduction electrocatalysts. However, the catalytic mechanism remains experimentally unproven and many key intermediates of the prototypical catalyst have not been observed. Here we report the use of vibrational sum-frequency generation spectroscopy to study the catalytic intermediates during CO2 reduction in situ at the electrode surface. We explore the complex applied-potential and acid-dependent mechanistic pathways and provide evidence of the theoretically derived mechanisms. Demonstrating the ability to detect the key species that are only transiently present at the electrode surface is important as the need for an improved mechanistic understanding is a common theme throughout the field of molecular electrocatalysis.

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Fig. 1: Proposed electrocatalytic pathways for the reduction of CO2 by 1.
Fig. 2: CVs of 1 under argon and CO2 in the presence or absence of TFE.
Fig. 3: VSFG spectra of 1 recorded during two successive CVs under Ar.
Fig. 4: VSFG spectra under CO2 and TFE that show new bands assigned to catalytic intermediates.
Fig. 5: VSFG spectra that show the potential dependence of the new CO2 reduction intermediate ν(CO) mode.
Fig. 6: VSFG spectra of the CO2 reduction intermediate recorded using labelled CO2VSFG spectra that show the potential dependence of the new CO2 reduction intermediate ν(CO) mode.
Fig. 7: Fragment-resolved analysis of the contributions to the computed infrared modes (normalized eigenvectors) for 6–9.
Fig. 8: Computed Stark shifts of the vibrational modes of 8 and 9.

Data availability

Raw data for all figures within the paper are freely available from the University of Liverpool Research Data Catalogue at


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We are grateful to C. Smith (University of Liverpool) for the synthesis of 1. This work was carried out at the Ultra facility of the UK Central Laser Facility during experiments 15130005, 16130016 and 16230052. A.J.C. and G.N. acknowledge support from EPSRC (EP/K006851/1, EP/P034497/1 and EP/N010531/). G.T. acknowledges support from EPSRC (EP/I004483/1, EP/K013610/1, EP/P022189/1 and EP/P022189/1). This work made use of the ARCHER (via the UKCP Consortium, EPSRC UK EP/K013610/1 and EP/P022189/1) and UK Materials and Molecular Modelling Hub (EPSRC UK EP/P020194/1) High-Performance Computing facilities.

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G.N., A.J.C., P.M.D. and J.J.W. carried out the experimental work. G.T. carried out the computational work. A.J.C. and G.T. wrote the manuscript. All the authors contributed to the editing of the manuscript.

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Correspondence to Paul M. Donaldson or Alexander J. Cowan.

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Supplementary Methods, Supplementary Figures 1–15, Supplementary Tables 1–22, Supplementary References

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Neri, G., Walsh, J.J., Teobaldi, G. et al. Detection of catalytic intermediates at an electrode surface during carbon dioxide reduction by an earth-abundant catalyst. Nat Catal 1, 952–959 (2018).

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