Abstract
The crucial role of electrolyte cations in CO2 electroreduction has received intensive attention. One prevailing theory is that through electrostatic interactions or direct coordination, larger cations such as Cs+ can better stabilize the key intermediate species for CO and multicarbon (C2+) product generation, for example, on silver and copper, respectively. Here we show that smaller, more acidic alkali metal cations greatly enhance CO2-to-methanol conversion kinetics (Li+ > Na+ > K+ > Cs+) on an immobilized molecular cobalt catalyst, unlike the trend observed for CO and C2+. Through electrokinetic analyses and kinetic isotope effect studies along with computational investigations, we show that the hydration shell of a cation serves as a proton donor in the rate-determining protonation step of adsorbed CHO where acidic cations promote the proton-coupled electron transfer. This study reveals the promotional effect of cation solvation environment on CO2 electroreduction beyond the widely acknowledged stabilizing effect of cations.
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Acknowledgements
This work was supported by Niterra Co., Ltd. The authors are grateful to W. Massefski, J. Grimes and B. Adams for their assistance with NMR pulse sequence optimization and data analysis. We thank J. Johnson, A. Wang and B. Liu for access to their freeze dryer. We also thank J. Peng and J. Lunger for discussions on our computational approaches. This work used the Extreme Science and Engineering Discovery Environment, which is supported by National Science Foundation grant number DMR-160163. The authors also acknowledge the MIT SuperCloud and Lincoln Laboratory Supercomputing Center for providing high-performance computing resources.
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S.Y. and Y.S.-H. conceived the research idea. S.Y. and H.Y. performed experiments with assistance from H.X. and D.J.Z. S.W. and A.A. carried out DFT calculations and MD simulations with assistance from K.G., respectively. J.K. conducted electron microscopy characterization. B.H., H.X., D.J.Z., X.W., H.I. and D.M. contributed to discussions. S.Y. and Y.S.-H. wrote the manuscript with feedback from all authors.
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Supplementary Figs. 1–34, Tables 1–6 and Notes 1 and 2.
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Atomic coordinates of optimized structures.
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Initial and final configurations for MD simulations.
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Yu, S., Yamauchi, H., Wang, S. et al. CO2-to-methanol electroconversion on a molecular cobalt catalyst facilitated by acidic cations. Nat Catal (2024). https://doi.org/10.1038/s41929-024-01197-2
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DOI: https://doi.org/10.1038/s41929-024-01197-2