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Mechanochemistry for ammonia synthesis under mild conditions

Abstract

Ammonia, one of the most important synthetic feedstocks, is mainly produced by the Haber–Bosch process at 400–500 °C and above 100 bar. The process cannot be performed under ambient conditions for kinetic reasons. Here, we demonstrate that ammonia can be synthesized at 45 °C and 1 bar via a mechanochemical method using an iron-based catalyst. With this process the ammonia final concentration reached 82.5 vol%, which is higher than state-of-the-art ammonia synthesis under high temperature and pressure (25 vol%, 450 °C, 200 bar). The mechanochemically induced high defect density and violent impact on the iron catalyst were responsible for the mild synthesis conditions.

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Fig. 1: Schematic illustration of the ammonia synthesis process.
Fig. 2: Reaction kinetics of nitrogen dissociation and ammonia yield.
Fig. 3: Characterization of the iron catalyst.
Fig. 4: Theoretical analysis of the hydrogenation process.

Data availability

The data that support the findings of this study are presented in the main text and the Supplementary Information, and are available from the corresponding author upon reasonable request.

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Acknowledgements

We are grateful for the use of the Pohang Accelerator Laboratory (6D UNIST-PAL beamline, South Korea) and the Mössbauer Effect Data Center (DICP, China). This work was supported by the Creative Research Initiative (CRI, 2014R1A3A2069102) and the Science Research Center (SRC, 2016R1A5A1009405) programmes through the National Research Foundation (NRF) of Korea, the U-K Brand Project (1.200096.01) of UNIST, and the National Natural Science Foundation of China (no. 51631004). S.S. acknowledges support from the University of Calgary’s Canada First Research Excellence Fund programme, the Global Research Initiative in Sustainable Low Carbon Unconventional Resources.

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Contributions

J.-B.B. conceived the project and oversaw all the research phases. J.-B.B. and G.-F.H. designed the project. H.-J.N. conducted the HRTEM experiments. F.L., Z.F. and Y.L. carried out the soft XANES measurements. S.-J.K. performed the GC measurements. J.-B.B., Q.J. and G.-F.H. conceived the theoretical model. Q.J., S.S., Z.-W.C., C.V.S. and C.C. conducted the theoretical calculations. Data collection and analysis were conducted by J.-B.B. and G.-F.H. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Zhi-Wen Chen, Samira Siahrostami, Qing Jiang or Jong-Beom Baek.

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Peer review information Nature Nanotechnology thanks Viktor Colic 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, Figs. 1–16, Tables 1–3 and refs. 1–4.

Supplementary Video 1

Video showing a typical ammonia preparation process via mechanochemistry.

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Han, GF., Li, F., Chen, ZW. et al. Mechanochemistry for ammonia synthesis under mild conditions. Nat. Nanotechnol. 16, 325–330 (2021). https://doi.org/10.1038/s41565-020-00809-9

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