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Electrochemical nitrate reduction to ammonia with cation shuttling in a solid electrolyte reactor

Nature Catalysis (2024)Cite this article

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Abstract

While electrochemical nitrate reduction to ammonia represents a promising route for water treatment and ammonia generation, one critical challenge in the field is the need for high-concentration supporting electrolytes in this electrochemical system. Here we report a three-chamber porous solid electrolyte reactor design coupled with cation shielding effects for efficient nitrate reduction reaction without supporting electrolytes. By feeding treated water from the cathode chamber to the middle porous solid electrolyte layer, we can realize an alkali metal cation shuttling loop from the middle layer back into the cathode chamber to boost the nitrate reduction selectivity and suppress the hydrogen evolution side reaction. This reactor system can deliver high ammonia Faradaic efficiencies (>90%) at practical current densities (>100 mA cm−2) under a typical wastewater nitrate concentration of 2,000 ppm, enabling a high-purity water effluent and NH3(g) as products with no need for electrolyte recovery processes.

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Fig. 1: Recycling NH3.
Fig. 2: Reactor design for improved NO3RR performance.
Fig. 3: Process design for NO3− conversion and its NO3RR performance.
Fig. 4: Long-term stability test for direct NO3− conversion.
Fig. 5: TEA of NO3− conversion using a PSE reactor.

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Data availability

The data supporting the findings of this study are available in the main text, Supplementary Information, and Source data provided with this paper. Additional data related to this study may be requested from the corresponding author. Source data are provided with this paper.

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Acknowledgements

This work was supported by the National Science Foundation Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment (NEWT EEC 1449500). The authors acknowledge the use of the Shared Equipment Authority and Electron Microscopy Center at Rice University for their contributions to this research. F.-Y.C. gratefully acknowledges the support from the Riki Kobayashi Fellowship Award from the Department of Chemical and Biomolecular Engineering at Rice University.

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Authors and Affiliations

  1. Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, USA

    Feng-Yang Chen, Ahmad Elgazzar, Stephanie Pecaut, Chang Qiu, Yuge Feng, Sushanth Ashokkumar, Zhou Yu, Chase Sellers, Shaoyun Hao, Peng Zhu & Haotian Wang

  2. Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA

    Haotian Wang

  3. Department of Chemistry, Rice University, Houston, TX, USA

    Haotian Wang

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  1. Feng-Yang Chen
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Contributions

The project was conceptualized by F.-Y.C. and H.W., with H.W. providing project supervision. Catalyst synthesis was performed by F.-Y.C. and S.P. F.-Y.C. and C.Q. carried out the catalyst characterization. The reactor system was designed by F.-Y.C. and H.W. Electrochemical tests and data processing were conducted by F.-Y.C., A.E., S.P., Y.F., S.A., S.H., Z.Y. and C.S. TEA was done by F.-Y.C. and P.Z. The manuscript was co-written by F.-Y.C. and H.W. All authors participated in result discussions and provided comments on the manuscript.

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Correspondence to Haotian Wang.

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Nature Catalysis thanks Mahinder Ramdin, David Hickey and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Chen, FY., Elgazzar, A., Pecaut, S. et al. Electrochemical nitrate reduction to ammonia with cation shuttling in a solid electrolyte reactor. Nat Catal (2024). https://doi.org/10.1038/s41929-024-01200-w

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