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Efficient conversion of low-concentration nitrate sources into ammonia on a Ru-dispersed Cu nanowire electrocatalyst

Abstract

Electrochemically converting nitrate ions, a widely distributed nitrogen source in industrial wastewater and polluted groundwater, into ammonia represents a sustainable route for both wastewater treatment and ammonia generation. However, it is currently hindered by low catalytic activities, especially under low nitrate concentrations. Here we report a high-performance Ru-dispersed Cu nanowire catalyst that delivers an industrial-relevant nitrate reduction current of 1 A cm–2 while maintaining a high NH3 Faradaic efficiency of 93%. More importantly, this high nitrate-reduction catalytic activity enables over a 99% nitrate conversion into ammonia, from an industrial wastewater level of 2,000 ppm to a drinkable water level <50 ppm, while still maintaining an over 90% Faradaic efficiency. Coupling the nitrate reduction effluent stream with an air stripping process, we successfully obtained high purity solid NH4Cl and liquid NH3 solution products, which suggests a practical approach to convert wastewater nitrate into valuable ammonia products. Density functional theory calculations reveal that the highly dispersed Ru atoms provide active nitrate reduction sites and the surrounding Cu sites can suppress the main side reaction, the hydrogen evolution reaction.

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Fig. 1: Synthesis and characterizations of Ru-CuNW.
Fig. 2: Electrocatalytic NO3RR performance.
Fig. 3: Structural analysis of Ru-CuNW.
Fig. 4: DFT calculations.
Fig. 5: Practical ammonia products synthesis.

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 authors upon reasonable request.

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Acknowledgements

This work was supported by Rice University, the National Science Foundation Nanosystems Engineering Research Center for Nanotechnology Enabled Water Treatment (NEWT EEC 1449500) and a Welch Foundation Research Grant (C-2051-20200401). We acknowledge the use of the Electron Microscopy Center (EMC) at Rice University. Y.H. acknowledges the support from the Welch Foundation (C-2065-20210327). This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by the Argonne National Laboratory under contract no. DE-AC02-06CH11357. A portion of this research was performed at the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility sponsored by the Biological and Environmental Research program under Contract No. DE-AC05-76RL01830. Aberration-corrected STEM research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. Part of the research described in this article was performed at the Canadian Light Source, a national research facility of the University of Saskatchewan, which is supported by the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council (NSERC), the National Research Council (NRC), the Canadian Institutes of Health Research (CIHR), the Government of Saskatchewan and the University of Saskatchewan.

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F.-Y.C., Z.-Y.W. and H.W. conceptualized the project. H.W. and C.L.M. supervised the project. Z.-Y.W. and F.-Y.C. developed the synthesis of the catalysts. F.-Y.C., Z.-Y.W. and S.P. performed the catalyst synthesis, catalyst characterization, electrochemical tests and the related data processing. S.G. and D.J.R. performed the DFT simulation. J.Y.K. and P.Z. assisted the product characterization. Y.Z.F., D.M.M. and H.Z. helped with the testing and analysis of XAS characterization. W.X. helped with the testing of the HEXRD characterization. G.G., Y.H. and D.A.C. assisted with the TEM characterization. S.V.L. and D.E.P. performed the APT analysis. F.-Y.C., Z.-Y.W., S.G., D.J.R., H.W. and C.L.M. co-wrote the manuscript. All the authors discussed the results and commented on the manuscript.

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Correspondence to Daniel E. Perea, Christopher L. Muhich or Haotian Wang.

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Nature Nanotechnology thanks Emma Lovell and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–49, Tables 1–7 and Notes 1–4.

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Chen, FY., Wu, ZY., Gupta, S. et al. Efficient conversion of low-concentration nitrate sources into ammonia on a Ru-dispersed Cu nanowire electrocatalyst. Nat. Nanotechnol. (2022). https://doi.org/10.1038/s41565-022-01121-4

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