Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

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.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

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.

Similar content being viewed by others

Data availability

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


  1. Dey, S. et al. Molecular electrocatalysts for the oxygen reduction reaction. Nat. Rev. Chem. 1, 0098 (2017).

  2. DuBois, D. L. Development of molecular electrocatalysts for energy storage. Inorg. Chem. 53, 3935–3960 (2014).

    Article  CAS  PubMed  Google Scholar 

  3. Costentin, C., Robert, M. & Savéant, J.-M. Catalysis of the electrochemical reduction of carbon dioxide. Chem. Soc. Rev. 42, 2423–2436 (2013).

    Article  CAS  PubMed  Google Scholar 

  4. Lee, K. J., Elgrishi, N., Kandemir, B. & Dempsey, J. L. Electrochemical and spectroscopic methods for evaluating molecular electrocatalysts. Nat. Rev. Chem. 1, 0039 (2017).

  5. Shen, Y. R. Surface properties probed by second-harmonic and sum-frequency generation. Nature 337, 519–525 (1989).

    Article  CAS  Google Scholar 

  6. Shen, Y. R. Basic theory of surface sum-frequency generation. J. Phys. Chem. C 116, 15505–15509 (2012).

    Article  CAS  Google Scholar 

  7. Lambert, A. G., Davies, P. B. & Neivandt, D. J. Implementing the theory of sum frequency generation vibrational spectroscopy: a tutorial review. Appl. Spectrosc. Rev. 40, 103–145 (2005).

    Article  CAS  Google Scholar 

  8. Rey, N. G. & Dlott, D. D. Studies of electrochemical interfaces by broadband sum frequency generation. J. Electroanal. Chem. 800, 114–125 (2017).

    Article  CAS  Google Scholar 

  9. Baldelli, S. Probing electric fields at the ionic liquid−electrode interface using sum frequency generation spectroscopy and electrochemistry. J. Phys. Chem. B 109, 13049–13051 (2005).

    Article  CAS  PubMed  Google Scholar 

  10. Liu, W.-T. & Shen, Y. R. In situ sum-frequency vibrational spectroscopy of electrochemical interfaces with surface plasmon resonance. Proc. Natl Acad. Sci. USA 111, 1293–1297 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. Tadjeddine, A. et al. Sum and difference frequency generation at the electrochemical interface. Phys. Status Solidi 175, 89–107 (1999).

    Article  CAS  Google Scholar 

  12. Anfuso, C. L. et al. Orientation of a series of CO2 reduction catalysts on single crystal TiO2 probed by phase-sensitive vibrational sum frequency generation spectroscopy (PS-VSFG). J. Phys. Chem. C 116, 24107–24114 (2012).

    Article  CAS  Google Scholar 

  13. Ge, A. et al. Surface-induced anisotropic binding of a rhenium CO2-reduction catalyst on rutile TiO2(110) surfaces. J. Phys. Chem. C 120, 20970–20977 (2016).

    Article  CAS  Google Scholar 

  14. Anfuso, C. L., Ricks, A. M., Rodríguez-Córdoba, W. & Lian, T. Ultrafast vibrational relaxation dynamics of a rhenium bipyridyl CO2–reduction catalyst at a Au electrode surface probed by time-resolved vibrational sum frequency generation spectroscopy. J. Phys. Chem. C 116, 26377–26384 (2012).

  15. Wang, J. et al. Short-range catalyst–surface interactions revealed by heterodyne two-dimensional sum frequency generation spectroscopy. J. Phys. Chem. Lett. 6, 4204–4209 (2015).

    Article  CAS  PubMed  Google Scholar 

  16. Neri, G., Donaldson, P. M. & Cowan, A. J. The role of electrode–catalyst interactions in enabling efficient CO2 reduction with Mo(bpy)(CO)4 as revealed by vibrational sum-frequency generation spectroscopy. J. Am. Chem. Soc. 139, 13791–13797 (2017).

    Article  CAS  PubMed  Google Scholar 

  17. Tory, J., Setterfield-Price, B., Dryfe, R. A. W. & Hartl, F. [M(CO)4 (2,2′-bipyridine)] (M = Cr, Mo, W) complexes as efficient catalysts for electrochemical reduction of CO2 at a gold electrode. ChemElectroChem 2, 213–217 (2015).

    Article  CAS  Google Scholar 

  18. Bourrez, M., Molton, F., Chardon-Noblat, S. & Deronzier, A. [Mn(bipyridyl)(CO)3Br]: an abundant metal carbonyl complex as efficient electrocatalyst for CO2 reduction. Angew. Chem. Int. Ed. 50, 9903–9906 (2011).

    Article  CAS  Google Scholar 

  19. Stanbury, M., Compain, J.-D. & Chardon-Noblat, S. Electro and photoreduction of CO2 driven by manganese–carbonyl molecular catalysts. Coord. Chem. Rev. 361, 120–137 (2018).

    Article  CAS  Google Scholar 

  20. Sampson, M. D. & Kubiak, C. P. Manganese electrocatalysts with bulky bipyridine ligands: utilizing Lewis acids to promote carbon dioxide reduction at low overpotentials. J. Am. Chem. Soc. 138, 1386–1393 (2016).

    Article  CAS  PubMed  Google Scholar 

  21. Ngo, K. T. et al. Turning on the protonation-first pathway for electrocatalytic CO2 reduction by manganese bipyridyl tricarbonyl complexes. J. Am. Chem. Soc. 139, 2604–2618 (2017).

    Article  CAS  PubMed  Google Scholar 

  22. Walsh, J. J., Neri, G., Smith, C. L. & Cowan, A. J. Electrocatalytic CO2 reduction with a membrane supported manganese catalyst in aqueous solution. Chem. Commun. 50, 12698–12701 (2014).

    Article  CAS  Google Scholar 

  23. Walsh, J. J. et al. Improving the efficiency of electrochemical CO2 reduction using immobilized manganese complexes. Faraday Discuss. 183, 147–160 (2015).

    Article  CAS  PubMed  Google Scholar 

  24. Reuillard, B. et al. Tuning product selectivity for aqueous CO2 reduction with a Mn(bipyridine)–pyrene catalyst immobilized on a carbon nanotube electrode. J. Am. Chem. Soc. 139, 14425–14435 (2017).

    Article  CAS  PubMed Central  PubMed  Google Scholar 

  25. Hartl, F., Rossenaar, B. D., Stor, G. J. & Stufkens, D. Role of an electron-transfer chain reaction in theunusual photochemical formation of five-coordinated anions [Mn(CO)3 (α-diimine)] from fac-[Mn(X)(CO)3 (α-diimine)] (X = halide) at low temperatures. Recl. Trav. Chim. Pays-Bas 114, 565–570 (1995).

    Article  CAS  Google Scholar 

  26. Bourrez, M. et al. Pulsed-EPR evidence of a manganese(ii) hydroxycarbonyl intermediate in the electrocatalytic reduction of carbon dioxide by a manganese bipyridyl derivative. Angew. Chem. Int. Ed. 53, 240–243 (2014).

    Article  CAS  Google Scholar 

  27. Rossenaar, B. D. et al. Electrochemical and IR/UV−vis spectroelectrochemical studies of fac-[Mn(X)(CO)3(iPr-DAB)]n (n = 0, X = Br, Me, Bz; n = +1, X = THF, MeCN, nPrCN, P(OMe)3; iPr-DAB = 1,4-diisopropyl-1,4-diaza-1,3-butadiene) at variable temperatures: relation between electrochemical and photochemical generation of [Mn(CO)3(α-diimine)]. Organometallics 16, 4675–4685 (1997).

    Article  CAS  Google Scholar 

  28. Franco, F. et al. Local proton source in electrocatalytic CO2 reduction with [Mn(bpy-R)(CO)3Br] complexes. Chem. Eur. J. 23, 4782–4793 (2017).

    Article  CAS  PubMed  Google Scholar 

  29. Hartl, F., Rosa, P., Ricard, L., Le Floch, P. & Záliš, S. Electronic transitions and bonding properties in a series of five-coordinate ‘16-electron’ complexes [Mn(CO)3(L2)] (L2 = chelating redox-active π-donor ligand). Coord. Chem. Rev. 251, 557–576 (2007).

    Article  CAS  Google Scholar 

  30. Hawecker, J., Lehn, J.-M. & Ziessel, R. Electrocatalytic reduction of carbon dioxide mediated by Re(bipy)(CO)3Cl (bipy = 2,2′-bipyridine). J. Chem. Soc. Chem. Commun. 0, 328–330 (1984).

    Article  CAS  Google Scholar 

  31. Riplinger, C., Sampson, M. D., Ritzmann, A. M., Kubiak, C. P. & Carter, E. A. Mechanistic contrasts between manganese and rhenium bipyridine electrocatalysts for the reduction of carbon dioxide. J. Am. Chem. Soc. 136, 16285–16298 (2014).

    Article  CAS  PubMed  Google Scholar 

  32. Riplinger, C. & Carter, E. A. Influence of weak Brønsted acids on electrocatalytic CO2 reduction by manganese and rhenium bipyridine catalysts. ACS Catal. 5, 900–908 (2015).

    Article  CAS  Google Scholar 

  33. Lam, Y. C., Nielsen, R. J., Gray, H. B. & Goddard, W. A. A Mn bipyrimidine catalyst predicted to reduce CO2 at lower overpotential. ACS Catal. 5, 2521–2528 (2015).

    Article  CAS  Google Scholar 

  34. Grills, D. C. et al. Mechanism of the formation of a Mn-based CO2 reduction catalyst revealed by pulse radiolysis with time-resolved infrared detection. J. Am. Chem. Soc. 136, 5563–5566 (2014).

    Article  CAS  PubMed  Google Scholar 

  35. Lagutchev, A., Lozano, A., Mukherjee, P., Hambir, S. A. & Dlott, D. D. Compact broadband vibrational sum-frequency generation spectrometer with nonresonant suppression. Spectrochim. Acta A 75, 1289–1296 (2010).

    Article  CAS  Google Scholar 

  36. Bishop, D. M. The vibrational Stark effect. J. Chem. Phys. 98, 3179–3184 (1993).

    Article  CAS  Google Scholar 

  37. Ohno, P. E., Wang, H. & Geiger, F. M. Second-order spectral lineshapes from charged interfaces. Nat. Commun. 8, 1032 (2017).

    Article  PubMed Central  CAS  PubMed  Google Scholar 

  38. Sampson, M. D. et al. Manganese catalysts with bulky bipyridine ligands for the electrocatalytic reduction of carbon dioxide: eliminating dimerization and altering catalysis. J. Am. Chem. Soc. 136, 5460–5471 (2014).

    Article  CAS  PubMed  Google Scholar 

  39. Borovkov, V. Y., Kolesnikov, S. P., Kovalchuk, V. I. & D’Itri, J. L. Probing adsorption sites of silica-supported platinum with 13C16O + 12C16O and 13C18O + 12C16O mixtures: a comparative Fourier transform infrared investigation. J. Phys. Chem. B 109, 19772–19778 (2005).

    Article  CAS  PubMed  Google Scholar 

  40. Scheiring, T., Kaim, W. & Fiedler, J. Geometrical and electronic structures of the acetyl complex Re(bpy)(CO)3(COCH3) and of [M(bpy)(CO)4](OTf), M = Mn, Re. J. Organomet. Chem. 598, 136–141 (2000).

    Article  CAS  Google Scholar 

  41. Franco, F., Pinto, M. F., Royo, B. & Lloret-Fillol, J. A highly active N-heterocyclic carbene Mn(i) complex for selective electrocatalytic CO2 reduction to CO. Angew. Chem. Int. Ed. 57, 4603–4606 (2018).

    Article  CAS  Google Scholar 

  42. Smieja, J. M. & Kubiak, C. P. Re(bipy-tBu)(CO)3Cl-improved catalytic activity for reduction of carbon dioxide: IR-spectroelectrochemical and mechanistic studies. Inorg. Chem. 49, 9283–9289 (2010).

    Article  CAS  PubMed  Google Scholar 

  43. Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Article  Google Scholar 

  44. Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    Article  CAS  Google Scholar 

  45. Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    Article  CAS  Google Scholar 

  46. Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    Google Scholar 

  47. Perdew, J., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    Article  CAS  PubMed  Google Scholar 

  48. Grimme, S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 27, 1787–1799 (2006).

    Article  CAS  PubMed  Google Scholar 

  49. Amft, M., Lebègue, S., Eriksson, O. & Skorodumova, N. V. Adsorption of Cu, Ag, and Au atoms on graphene including van der Waals interactions. J. Phys. Condens. Matter 23, 395001 (2011).

    Article  CAS  PubMed  Google Scholar 

  50. Wu, Y. et al. Electrode–ligand interactions dramatically enhance CO2 conversion to CO by the [Ni(cyclam)](PF6)2 catalyst. ACS Catal. 7, 5282–5288 (2017).

    Article  CAS  Google Scholar 

  51. Keith, J. A., Grice, K. A., Kubiak, C. P. & Carter, E. A. Elucidation of the selectivity of proton-dependent electrocatalytic CO2 reduction by fac-Re(bpy)(CO)3Cl. J. Am. Chem. Soc. 135, 15823–15829 (2013).

    Article  CAS  PubMed  Google Scholar 

Download references


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.

Author information

Authors and Affiliations



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.

Corresponding authors

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

Ethics declarations

Competing interests

The authors declare no competing interests

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

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

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

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).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing