Combining inorganic catalysts with CO2-fixing microorganisms has displayed a high efficiency for electricity-driven CO2 reduction. However, the maximum throughput can be limited by the low solubility of mediators, such as H2, that deliver reducing equivalents from the electrodes to the microbes. Here we report that the introduction of a biocompatible perfluorocarbon nanoemulsion as a H2 carrier increases the throughput of CO2 reduction into acetic acid by 190%. With the acetogen Sporomusa ovata as a model system, an average acetate titre of 6.4 ± 1.1 g l−1 (107 mM) was achieved in four days with close to 100% Faradaic efficiency. This is equivalent to a productivity of 1.1 mM h−1, among the highest in bioelectrochemical systems. A mechanistic investigation shows that the non-specific binding of perfluorocarbon nanoemulsions promotes the kinetics of H2 transfer and subsequent oxidation by more than threefold. Introducing nanoscale gas carriers is viable to alleviate throughput bottlenecks in the electricity-driven microbial CO2 reduction into commodity chemicals.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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We acknowledge B. Natinsky for the diffusion ordered spectroscopy experiments. We also thank S. Kosuri for the use of flow cytometry facilities and the Molecular Instrumentation Center at the University of California, Los Angeles for sample characterizations. D.A.E. acknowledges the financial support of an NIH training grant (5T32GM067555-12). J.A.I. is supported by a Eugene V. Cota-Robles fellowship. E.M.S. and C.L. acknowledge start-up funds from the University of California, Los Angeles and the financial support of the Jeffery and Helo Zink Endowed Professional Development Term Chair (to C.L.) and the John D. McTague Career Development Term Chair (to E.M.S.).
The authors declare no competing interests.
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Rodrigues, R.M., Guan, X., Iñiguez, J.A. et al. Perfluorocarbon nanoemulsion promotes the delivery of reducing equivalents for electricity-driven microbial CO2 reduction. Nat Catal 2, 407–414 (2019). https://doi.org/10.1038/s41929-019-0264-0
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