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Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex

Geer, Ana M. and Musgrave, Charles, III and Webber, Christopher and Nielsen, Robert J. and McKeown, Bradley A. and Liu, Chang and Schleker, P. Philipp M. and Jakes, Peter and Jia, Xiaofan and Dickie, Diane A. and Granwehr, Josef and Zhang, Sen and Machan, Charles W. and Goddard, William A., III and Gunnoe, T. Brent (2021) Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex. ACS Catalysis, 11 (12). pp. 7223-7240. ISSN 2155-5435. doi:10.1021/acscatal.1c01395.

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We report a trinuclear copper(II) complex, [(DAM)Cu₃(μ³-O)][Cl]₄ (1, DAM = dodecaaza macrotetracycle), as a homogeneous electrocatalyst for water oxidation to dioxygen in phosphate-buffered solutions at pH 7.0, 8.1, and 11.5. Electrocatalytic water oxidation at pH 7 occurs at an overpotential of 550 mV with a turnover frequency of ∼19 s⁻¹ at 1.5 V vs NHE. Controlled potential electrolysis (CPE) experiments at pH 11.5 over 3 h at 1.2 V and at pH 8.1 for 40 min at 1.37 V vs NHE confirm the evolution of dioxygen with Faradaic efficiencies of 81% and 45%, respectively. Rinse tests conducted after CPE studies provide evidence for the homogeneous nature of the catalysis. The linear dependence of the current density on the catalyst concentration indicates a likely first-order dependence on the Cu precatalyst 1, while kinetic isotope studies (H₂O versus D₂O) point to involvement of a proton in or preceding the rate-determining step. Rotating ring-disk electrode measurements at pH 8.1 and 11.2 show no evidence of H₂O₂ formation and support selectivity to form dioxygen. Freeze-quench electron paramagnetic resonance studies during electrolysis provide evidence for the formation of a molecular copper intermediate. Experimental and computational studies support a key role of the phosphate as an acceptor base. Moreover, density functional theory calculations highlight the importance of second-sphere interactions and the role of the nitrogen-based ligands to facilitate proton transfer processes.

Item Type:Article
Related URLs:
URLURL TypeDescription
Geer, Ana M.0000-0003-1115-6759
Musgrave, Charles, III0000-0002-3432-0817
Nielsen, Robert J.0000-0002-7962-0186
Liu, Chang0000-0002-7568-0608
Schleker, P. Philipp M.0000-0002-6366-0693
Jia, Xiaofan0000-0003-0425-5089
Dickie, Diane A.0000-0003-0939-3309
Zhang, Sen0000-0002-1716-3741
Machan, Charles W.0000-0002-5182-1138
Goddard, William A., III0000-0003-0097-5716
Gunnoe, T. Brent0000-0001-5714-3887
Additional Information:© 2021 American Chemical Society. Received: March 26, 2021; Revised: May 15, 2021; Published: June 4, 2021. This work was supported by the U.S. National Science Foundation (CBET-1805022) and the MAXNET Energy effort. EPR experiments were supported by the Max Planck Society, and the EPR instrument was funded by the Helmholtz Energy Materials Foundry (HEMF). The authors declare no competing financial interest.
Funding AgencyGrant Number
Max Planck SocietyUNSPECIFIED
Helmholtz Energy Materials FoundryUNSPECIFIED
Subject Keywords:water oxidation, copper, electrocatalysis, dioxygen, trinuclear, DFT calculations
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Issue or Number:12
Record Number:CaltechAUTHORS:20210607-115055397
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Official Citation:Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex. Ana M. Geer, Charles Musgrave III, Christopher Webber, Robert J. Nielsen, Bradley A. McKeown, Chang Liu, P. Philipp M. Schleker, Peter Jakes, Xiaofan Jia, Diane A. Dickie, Josef Granwehr, Sen Zhang, Charles W. Machan, William A. Goddard, and T. Brent Gunnoe. ACS Catalysis 2021 11 (12), 7223-7240; DOI: 10.1021/acscatal.1c01395
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109421
Deposited By: George Porter
Deposited On:07 Jun 2021 20:04
Last Modified:16 Nov 2021 19:36

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