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Cathodic NH₄⁺ leaching of nitrogen impurities in CoMo thin-film electrodes in aqueous acidic solutions

Yu, Weilai and Buabthong, Pakpoom and Read, Carlos G. and Dalleska, Nathan F. and Lewis, Nathan S. and Lewerenz, Hans-Joachim and Gray, Harry B. and Brinkert, Katharina (2020) Cathodic NH₄⁺ leaching of nitrogen impurities in CoMo thin-film electrodes in aqueous acidic solutions. Sustainable Energy and Fuels, 4 (10). pp. 5080-5087. ISSN 2398-4902. doi:10.1039/d0se00674b.

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Electrocatalytic reduction of dinitrogen (N₂) to ammonium (NH₄⁺) in acidic aqueous solutions was investigated at ambient temperature and pressure using a cobalt–molybdenum (CoMo) thin-film electrode prepared by magnetron reactive sputtering. Increased concentrations of ammonium ions (NH₄⁺) were consistently detected in the electrolyte using ion chromatography (IC) after constant-potential electrolysis at various potentials (≤−0.29 V vs. RHE). Using a newly developed analytical method based on ammonia derivatization, performing the experiments with ¹⁵N₂-labelled gas led however to the detection of increased ¹⁴NH₄⁺ concentrations instead of ¹⁵NH₄⁺. X-ray photoelectron spectroscopic (XPS) analysis of the electrode surface revealed the presence of Mo N and Mo–NH_x species. Several contamination sources were identified that led to substantial increases in the concentration of ammonium ions, including ¹⁵NH₃ impurities in ¹⁵N₂ gas. The observed ammonium concentrations can be consistently ascribed to leaching of nitrogen (¹⁴N) impurities incorporated in the CoMo film during the sputtering process. Researchers in the field are therefore urged to adopt extended protocols to identify and eliminate sources of ammonia contamination and to very carefully monitor the ammonium concentrations in each experimental step.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Yu, Weilai0000-0002-9420-0702
Buabthong, Pakpoom0000-0001-5538-138X
Dalleska, Nathan F.0000-0002-2059-1587
Lewis, Nathan S.0000-0001-5245-0538
Lewerenz, Hans-Joachim0000-0001-8433-9471
Gray, Harry B.0000-0002-4453-9716
Brinkert, Katharina0000-0002-3593-5047
Additional Information:© 2020 The Royal Society of Chemistry. Submitted 01 May 2020; Accepted 05 Aug 2020; First published 05 Aug 2020. K. B. acknowledges funding from the fellowship program of the German National Academy of Sciences – Leopoldina, grant LPDS 2016-06. Acknowledgment is made to the donors of The American Chemical Society Petroleum Research Fund for partial support of this research. Sample preparation and analyses were performed at the Joint Center for Artificial Photosynthesis, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993, which also provided support for N. S. L., W. Y., P. B. and C. G. R. We acknowledge use of instrumentation in the Molecular Materials Research Center of the Beckman Institute at Caltech. N. F. D. is grateful to the Linde Center for support. The Environmental Analysis Center is supported by the Beckman Institute at Caltech. W. Y. and C. G. R. acknowledge the Resnick Sustainability Institute at Caltech for fellowship support. Dr Fabai Wu and Prof. Victoria Orphan are acknowledged for providing the ¹⁵NH₄Cl standard reagent for UPLC-MS analysis. Mr Christopher Kenseth is thanked for assistance with UPLC-MS analysis. Dr Yuanlong Huang is acknowledged for assistance with chemiluminescence analysis. All authors would like to acknowledge the reviewers for their valuable comments in the first round. There are no conflicts to declare.
Group:JCAP, Resnick Sustainability Institute
Funding AgencyGrant Number
Deutsche Akademie der Naturforscher LeopoldinaLPDS 2016-06
American Chemical Society Petroleum Research FundUNSPECIFIED
Department of Energy (DOE)DE-SC0004993
Caltech Beckman InstituteUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Issue or Number:10
Record Number:CaltechAUTHORS:20200817-095314564
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Official Citation:Cathodic NH₄⁺ leaching of nitrogen impurities in CoMo thin-film electrodes in aqueous acidic solutions. Sustainable Energy Fuels, 2020, 4, 5080-5087; doi: 10.1039/d0se00674b
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104974
Deposited By: Tony Diaz
Deposited On:17 Aug 2020 20:06
Last Modified:16 Nov 2021 18:38

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