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Exploring CO2 reduction and crossover in membrane electrode assemblies

Nature Chemical Engineering volume 1, pages 340–353 (2024)Cite this article

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Abstract

Electrochemical CO2 reduction (CO2R) using renewable electricity is a key pathway toward synthesizing fuels and chemicals. In this study, multi-physics modeling is used to interpret experimental data obtained for CO2R to CO using Ag catalysts in a membrane electrode assembly. The one-dimensional model is validated using measured CO2 crossover and product formation rates. The kinetics of CO formation are described by Marcus–Hush–Chidsey kinetics, which enables accurate prediction of the experimental data by accounting for the reorganization of the solvent during CO2R. The results show how the performance is dictated by competing phenomena including ion formation and transport, CO2 solubility, and water management. The model shows that increasing the ion-exchange capacity of the membrane and surface area of the catalyst increases CO formation rates by >100 mA cm–2 without negatively impacting CO2 utilization. Here we provide insights into how to manage the trade-off between productivity and CO2 utilization in CO2 electrolyzers.

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Fig. 1: Electrolyzer architecture and model domain.
Fig. 2: Model validation with polarization data and CO2 crossover measurements.
Fig. 3: Concentration profiles in the CO2 electrolyzer.
Fig. 4: Coupled ion and water transport in the MEA.
Fig. 5: Effect of catalyst-layer SSA and thickness on CO2R.
Fig. 6: Effect of membrane IEC on CO2R.

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Data availability

The experimental data are available as an excel file in the Supplementary Information.

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Acknowledgements

The authors acknowledge A. J. King for graphic design and interpretation of the CO2R reorganization energy, and J. G. Petrovick for assistance with implementing the electro-osmotic coefficients in the model. Transmission electron microscopy and powder X-ray diffraction were performed by D. Lee in H. Zheng’s group, supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (BES), Materials Sciences and Engineering Division under contract no. DE-AC02-05-CH11231 within the in situ TEM programme (KC22ZH). The authors gratefully acknowledge Lawrence Berkeley National Laboratory’s Laboratory Directed Research and Development (LDRD) grant for funding. This material is also partially based upon work performed by support from the DOE EERE Bioenergy Technologies Office under contract no. DE-AC02-05CH11231 (A.Z.W). E.W.L. acknowledges support from the National Science and Engineering Research Council (NSERC) postdoctoral fellowship. J.C.B. was supported in part by a fellowship award under contract FA9550-21-F-0003 through the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program, sponsored by the Army Research Office (ARO).

Author information

Authors and Affiliations

  1. Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Eric W. Lees, Oyinkansola Romiluyi & Adam Z. Weber

  2. Department of Chemical and Biomolecular Engineering, University of California Berkeley, Berkeley, CA, USA

    Justin C. Bui, Oyinkansola Romiluyi & Alexis T. Bell

Authors
  1. Eric W. Lees
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Contributions

E.W.L. conceived the study, developed the model and wrote the initial manuscript draft. J.C.B. helped implement the Marcus–Hush–Chidsey kinetics and provided modeling support. O.R. performed all the experiments in the study. A.T.B. and A.Z.W. supervised the study, contributed to theory and model development, helped analyze the experimental data and managed the project. All authors contributed to writing and editing the manuscript.

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Correspondence to Adam Z. Weber.

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Nature Chemical Engineering thanks Haotian Wang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Notes 1–6, Figs. 1–23, model parameters and nomenclature.

Supplementary Data.

Experimental CO and H2 partial current densities and CO2 crossover measurements.

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Source Data Fig. 2

Data in Fig. 2 of main text.

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Data in Fig. 3 of main text.

Source Data Fig. 4

Data in Fig. 4 of main text.

Source Data Fig. 5

Data in Fig. 5 of main text.

Source Data Fig. 6

Data in Fig. 6 of main text.

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Lees, E.W., Bui, J.C., Romiluyi, O. et al. Exploring CO2 reduction and crossover in membrane electrode assemblies. Nat Chem Eng 1, 340–353 (2024). https://doi.org/10.1038/s44286-024-00062-0

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