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Electrocatalytic Ammonia Oxidation Mediated by a Polypyridyl Iron Catalyst

Zott, Michael D. and Garrido-Barros, Pablo and Peters, Jonas C. (2019) Electrocatalytic Ammonia Oxidation Mediated by a Polypyridyl Iron Catalyst. ACS Catalysis, 9 (11). pp. 10101-10108. ISSN 2155-5435. doi:10.1021/acscatal.9b03499.

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Electrocatalytic ammonia oxidation (AO) mediated by iron(II) tris(2-pyridylmethyl)amine (TPA) bis-ammine triflate, [(TPA)Fe(NH₃)₂]OTf₂, is reported. Interest in (electro)catalytic AO is growing rapidly, and this report adds a first-row transition metal (iron) complex to the known Ru catalysts recently reported. The featured system is well behaved and has been studied in detail by electrochemical methods. Cyclic voltammetry experiments in the presence of ammonia indicate an onset potential corresponding to ammonia oxidation at 0.7 V vs Fc/Fc⁺. Controlled potential coulometry (CPC) at an applied bias of 1.1 V confirms the generation of 16 equiv of N₂ with a Faradaic efficiency for N₂ of ∼80%. Employing ¹⁵NH₃ yields exclusively ³⁰N₂, demonstrating the conversion of ammonia to N₂. A suite of electrochemical studies is consistent with an initial EC step that generates an Fe^(III)–NH₂ intermediate (at 0.4 V) followed by an anodically shifted catalytic wave. The data indicate a rate-determining step that is first order in both [Fe] and [NH₃] and point to a fast catalytic rate (k_(obs)) of ∼10⁷ M⁻¹·s⁻¹ as computed by foot of the wave analysis (FOWA).

Item Type:Article
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URLURL TypeDescription
Zott, Michael D.0000-0003-0535-0512
Garrido-Barros, Pablo0000-0002-1489-3386
Peters, Jonas C.0000-0002-6610-4414
Additional Information:© 2019 American Chemical Society. Received: August 17, 2019; Revised: September 16, 2019; Published: September 19, 2019. This work was supported by Caltech, the Gordon and Betty Moore Foundation, and in part the Department of Energy, Office of Basic Energy Science, Catalysis Program (DOE-0235032) for general materials and supplies. We are grateful for access to the X-ray Facility and the Molecular Materials Research Center within the Beckman Institute and acknowledge Dr. Michael Takase and Larry Henling for assistance with XRD analysis. The authors thank Matthew J. Chalkley for helpful discussions. Author Contributions: M.D.Z. and P.G.-B.: These authors contributed equally. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. The authors declare no competing financial interest.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Department of Energy (DOE)DOE-0235032
Issue or Number:11
Record Number:CaltechAUTHORS:20191014-102537841
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Official Citation:Electrocatalytic Ammonia Oxidation Mediated by a Polypyridyl Iron Catalyst. Michael D. Zott, Pablo Garrido-Barros, and Jonas C. Peters. ACS Catalysis 2019 9 (11), 10101-10108. DOI: 10.1021/acscatal.9b03499
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99248
Deposited By: Tony Diaz
Deposited On:14 Oct 2019 17:35
Last Modified:16 Nov 2021 17:45

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