Journal Article

FZJ-2021-05736

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex

Geer, A. M. ; Musgrave III, C. ; Webber, C. ; Nielsen, R. J. ; McKeown, B. A. ; Liu, C. ; Schleker, P. P. M.FZJ* ; Jakes, P.FZJ* ; Jia, X. ; Dickie, D. A. ; Granwehr, J.FZJ*RWTH* ; Zhang, S. ; Machan, C. W. (Corresponding author) ; Goddard, W. A. (Corresponding author) ; Gunnoe, T. B. (Corresponding author)

2021
ACS Washington, DC

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Please use a persistent id in citations: http://hdl.handle.net/2128/30160  doi:10.1021/acscatal.1c01395

Abstract: 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.

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Contributing Institute(s):

1. Grundlagen der Elektrochemie (IEK-9)

Research Program(s):

1. 1223 - Batteries in Application (POF4-122) (POF4-122)

Appears in the scientific report 2021

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Database coverage:
; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Essential Science Indicators ; IF >= 10 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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