Abstract
Nitrogen (N) fertilizer plays a crucial role in agriculture. The conventional production and use of solid nitrogenous fertilizers results in substantial energy consumption and severe groundwater pollution. Here we propose an absorption‒electroreduction relay strategy capable of the distributed production of directly accessible liquid N fertilizer (NH4NO3 solution) from NOx, a common constituent of exhaust gases. When combined with plasma-driven N fixation, the raw feedstock in this strategy can be further extended to air. NOx is first absorbed by an aqueous solution. The NOx− produced as well as the residual NOx are selectively reduced to NH4NO3 by a ruthenium‒cobalt electrocatalyst (Ru9Co91). Through the N balance established between the absorption and electroreduction processes, NH4NO3 solutions are produced continuously without any other additive ions. We successfully constructed an 8-l membrane-free system that outputs 8.5 l h−1 of NH4NO3 solution at a constant concentration (840 mg l−1 of N) to meet the N fertilizer requirements for 20 m2 of farmland. This work offers an alternative route for obtaining N fertilizers, with the potential to improve the sustainability of the N fertilizer supply.
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Acknowledgements
We acknowledge the National Natural Science Foundation of China (Grant Nos. 22071173 to Y.Y., 22271213 to Bin Zhang and 224B2908 to K.Y.) and the Fundamental Research Funds for the Central Universities of China (Bin Zhang). We thank the Haihe Laboratory of Sustainable Chemical Transformations for financial support (Grant No. 24HHWCSS00009 to Y.Y.). We thank Y. Liu in the Analysis and Testing Center at Tianjin University for her assistance with the in situ ATR-FTIR.
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Y.Y. and Bin Zhang conceived the idea and supervised the project. S.H. designed the experiments. S.H., K.Y. and J. Zhou synthesized the materials and carried out the electrochemical measurements. S.H., T.L. and Y.H. carried out the in situ experiments. S.H. and J. Zhou drew the schematic diagram. K.Y. and Baoshun Zhang conducted the magnification experiment. L.G. and J. Zhu performed the COMSOL simulations. Y.Y. and S.H. wrote the paper. Bin Zhang revised the paper with comments from all authors.
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Nature Sustainability thanks Mohan Qin, Chuan Xia, Ke Xie, Gong Zhang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Supplementary Figs. 1–32, Notes 1–8 and Tables 1 and 2.
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Videos for the plasma process.
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Videos for the plasma-electrocatalyst process.
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Han, S., Yang, K., Gao, L. et al. Synthesis of liquid nitrogenous fertilizer via a nitrogen conversion balance. Nat Sustain 8, 1068–1076 (2025). https://doi.org/10.1038/s41893-025-01619-4
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DOI: https://doi.org/10.1038/s41893-025-01619-4
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