The role of in situ generated morphological motifs and Cu(i) species in C2+ product selectivity during CO2 pulsed electroreduction

Abstract

The efficient electrochemical conversion of CO2 provides a route to fuels and feedstocks. Copper catalysts are well-known to be selective to multicarbon products, although the role played by the surface architecture and the presence of oxides is not fully understood. Here we report improved efficiency towards ethanol by tuning the morphology and oxidation state of the copper catalysts through pulsed CO2 electrolysis. We establish a correlation between the enhanced production of C2+ products (76% ethylene, ethanol and n-propanol at −1.0 V versus the reversible hydrogen electrode) and the presence of (100) terraces, Cu2O and defects on Cu(100). We monitored the evolution of the catalyst morphology by analysis of cyclic voltammetry curves and ex situ atomic force microscopy data, whereas the chemical state of the surface was examined via quasi in situ X-ray photoelectron spectroscopy. We show that the continuous regeneration of defects and Cu(i) species synergistically favours C–C coupling pathways.

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Fig. 1: Atomic force microscopy images of a Cu(100) electrode after different surface treatments and reaction settings.
Fig. 2: Quasi in situ copper LMM Auger spectra of a Cu(100) electrode after the different pulse protocols indicated.
Fig. 3: CO2 pulsed electrolysis on a Cu(100) single crystal.
Fig. 4: Surface defects versus Cu(i) for C2+ production.
Fig. 5: Defect density versus product selectivity.
Fig. 6: Differential electrochemical mass spectroscopy measurements.

Data availability

The authors declare that the data supporting the findings of this study are available in the paper, Supplementary Information and Source Data. Additional datasets related to this study are available from the corresponding author on reasonable request.

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Acknowledgements

This work was supported by the European Research Council under grant ERC-OPERANDOCAT (ERC-725915) and the German Federal Ministry of Education and Research (BMBF) under grant nos. 033RCOO4D-‘e-Ethylene’ and 03SF0523C-‘CO2EKAT’. S.K. acknowledges financial support from the Max Planck Research School for Interface Controlled Materials for Energy Conversion (IMPRS-SurMat). Funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany´s Excellence Strategy (EXC 2008/1 (UniSysCat)) 390540038 is also appreciated.

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R.M.A.A. designed the electrochemical experiments, analysed the results and wrote the manuscript. F.S. performed the quasi in situ XPS measurements and wrote the corresponding section. S.K. carried out the microscopic characterization by STM and AFM. R.R. performed the DEMS experiments and wrote the corresponding section. B.R.C. co-designed the experiments, guided and supervised the project and co-wrote the manuscript. All authors discussed the results and reviewed the manuscript.

Corresponding author

Correspondence to Beatriz Roldan Cuenya.

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Supplementary Figs. 1–16, Notes 1–4, Tables 1 and 2, and refs. 1–8.

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Arán-Ais, R.M., Scholten, F., Kunze, S. et al. The role of in situ generated morphological motifs and Cu(i) species in C2+ product selectivity during CO2 pulsed electroreduction. Nat Energy 5, 317–325 (2020). https://doi.org/10.1038/s41560-020-0594-9

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