Abstract
Amino acids have wide application in the food and pharmaceutical industries. Current biotic and chemical syntheses suffer from low efficiency, complex purification operations and high energy consumption. Here we report a sustainable electrocatalytic synthesis of alanine from NO and pyruvic acid over oxide-derived Ag with low-coordination sites under ambient conditions. Mechanistic studies reveal a cascade NO → NH2OH → pyruvate oxime → alanine pathway. The quick pyruvate oxime formation and slow pyruvate oxime reduction steps cause various side reactions, leading to low alanine production. Then, a spatially decoupled two-pot electrosynthesis system using flow reactors loaded with oxide-derived Ag is designed for pyruvate oxime formation and reduction reactions. This decoupled system delivers 3.85 g of easily purified alanine with a total Faradaic efficiency of 70% and a purity of >98% at 100 mA cm−2. Further techno-economic analysis demonstrates the potential. This method is suitable for solar-energy-driven alanine electrosynthesis from polylactic acid wastes and for the fabrication of other amino acids.
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The DFT-optimized atomic coordinates are available in the Zenodo data repository at https://doi.org/10.5281/zenodo.8157625. The spreadsheets used for the cost analyses are available in Supplementary Data 1. Source data are provided with this paper.
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Acknowledgements
We acknowledge the National Natural Science Foundation of China (no. 22271213 to B.Z.) for financial support. M.L. thanks H. Li and J. Liu for discussions. We thank Y. Huang for differential electrochemical mass spectrometry tests. We also appreciate the kind help from Y. Liu with the ATR-FTIR measurements.
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B.Z. conceived the idea and directed the project. B.Z., M.L. and Y.W. designed the experiments. M.L. and Y.W. carried out most of the experiments, analysed the data and wrote the draught of the manuscript. C.C. performed the DFT calculations. B.-H.Z. conducted the techno-economic analysis. M.L. and B.-H.Z. explored the reaction mechanism. J.Z. and C.L. assisted with some experiments and data analysis. B.Z. and M.L. wrote the manuscript. C.L. revised the paper. All authors discussed the results and commented on the paper.
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Nature Catalysis thanks Magda Barecka, Wooyul Kim, Tao Wang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Supplementary Information
Supplementary Figs. 1–66, Notes 1–14, Tables 1–10 and refs. 1–18.
Supplementary Data 1
Source data of techno-economic analysis.
Source data
Source Data Fig. 2
Validation of the electrosynthesis of alanine.
Source Data Fig. 3
Mechanistic studies.
Source Data Fig. 4
Performance of the two-step electrosynthesis of alanine.
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Li, M., Wu, Y., Zhao, BH. et al. Electrosynthesis of amino acids from NO and α-keto acids using two decoupled flow reactors. Nat Catal 6, 906–915 (2023). https://doi.org/10.1038/s41929-023-01012-4
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DOI: https://doi.org/10.1038/s41929-023-01012-4
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