Efficient electrically powered CO2-to-ethanol via suppression of deoxygenation

Abstract

The carbon dioxide electroreduction reaction (CO2RR) provides ways to produce ethanol but its Faradaic efficiency could be further improved, especially in CO2RR studies reported at a total current density exceeding 10 mA cm−2. Here we report a class of catalysts that achieve an ethanol Faradaic efficiency of (52 ± 1)% and an ethanol cathodic energy efficiency of 31%. We exploit the fact that suppression of the deoxygenation of the intermediate HOCCH* to ethylene promotes ethanol production, and hence that confinement using capping layers having strong electron-donating ability on active catalysts promotes C–C coupling and increases the reaction energy of HOCCH* deoxygenation. Thus, we have developed an electrocatalyst with confined reaction volume by coating Cu catalysts with nitrogen-doped carbon. Spectroscopy suggests that the strong electron-donating ability and confinement of the nitrogen-doped carbon layers leads to the observed pronounced selectivity towards ethanol.

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Fig. 1: DFT calculations.
Fig. 2: Structural and compositional analyses of the 34% N-C/Cu catalyst on PTFE.
Fig. 3: CO2RR performance comparisons.
Fig. 4: In situ Raman and XAS characterization.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper, Supplementary Information and Source Data files.

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Acknowledgements

This work was supported by Suncor Energy, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and the CIFAR Bio-Inspired Solar Energy programme. Synchrotron measurements were carried out at the Advanced Photon Source, an Office of Science User Facility operated for the US DOE Office of Science by Argonne National Laboratory, and was supported by the US DOE under contract number DE-AC02-06CH11357, the Canadian Light Source and its funding partners, and the CMS beamline of the National Synchrotron Light Source II, a US DOE Office of the Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory. This research also used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract number DE-AC02-05CH1123, as well as the sources of the Canadian Light Source. The focused ion beam analyses and some of the TEM/STEM and SEM analyses were carried out at the CFI-funded Ontario Centre for the Characterization of Advanced Materials at the University of Toronto. STEM measurements and EELS mapping were performed at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, which is a user facility supported by the US DOE BES. M.C. is supported by the US DOE BES, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program. All DFT calculations were performed on the IBM BlueGene/Q supercomputer with support from the Southern Ontario Smart Computing Innovation Platform (SOSCIP) and Niagara supercomputer at the SciNet HPC Consortium. SOSCIP is funded by the Federal Economic Development Agency of Southern Ontario, the Province of Ontario, IBM Canada Ltd., Ontario Centres of Excellence, Mitacs and 15 Ontario academic member institutions. SciNet is funded by the Canada Foundation for Innovation, the Government of Ontario, Ontario Research Fund - Research Excellence and the University of Toronto. We thank T. Wu, Y. Z. Finfrock, L. Ma and G. Sterbinsky for technical support at the 9BM beamline of the Advanced Photon Source. D.S. acknowledges the NSERC E. W. R. Steacie Memorial Fellowship. J.L. acknowledges the Banting Postdoctoral Fellowships Program. We thank M. Wei from the University of Toronto for discussions and help.

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Contributions

E.H.S. supervised the project. X.W. designed and carried out the experiments, analysed the data and wrote the paper. Z.W. carried out DFT simulations and wrote the corresponding section. X.W. and A.O. carried out the MEA measurements. D.-H.N., Y.-S.L., F.L., Y.L. and S.-F.H. performed synchrotron X-ray spectroscopy measurements. Z.C. and M.C. conducted the preparation and characterization of STEM/TEM ultrathin slices of catalyst. B.C., J.T., J.Y.H. and B.S. conducted TEM characterizations. Y.W. and J.T. performed part of the SEM characterizations. J.W., A.P. and P.T. carried out XPS measurements. A.R.K. and L.J.R. carried out the WAXS measurements and analysed the WAXS data. C.M. carried out the local species concentration modelling. C.M.G. and C.P.O. provided help with the MEA measurements. F.P.G.d.A., C.-T.D., Y.C.L., J.L., T.-T.Z., M.L., Y.M., A.X., B. Stephen, B. Sun, A.H.I., S.O.K. and D.S. assisted with the discussions. A.R.K. is a guest researcher. All authors discussed the results and contributed to the preparation of the manuscript.

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Correspondence to Edward H. Sargent.

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A patent application regarding confined electrocatalysis for CO2-to-ethanol is in preparation.

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Supplementary Figs. 1–50, Tables 1–14 and Refs. 1–10.

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Source Data for Fig. 3a, b, c, and d

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Wang, X., Wang, Z., García de Arquer, F.P. et al. Efficient electrically powered CO2-to-ethanol via suppression of deoxygenation. Nat Energy 5, 478–486 (2020). https://doi.org/10.1038/s41560-020-0607-8

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