%0 Journal Article
%A Geer, Ana M.
%A Musgrave III, Charles
%A Webber, Christopher
%A Nielsen, Robert J.
%A McKeown, Bradley A.
%A Liu, Chang
%A Schleker, P. Philipp M.
%A Jakes, Peter
%A Jia, Xiaofan
%A Dickie, Diane A.
%A Granwehr, Josef
%A Zhang, Sen
%A Machan, Charles W.
%A Goddard, William A.
%A Gunnoe, T. Brent
%T Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex
%J ACS catalysis
%V 11
%N 12
%@ 2155-5435
%C Washington, DC
%I ACS
%M FZJ-2021-05736
%P 7223 - 7240
%D 2021
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000664333800044
%R 10.1021/acscatal.1c01395
%U https://juser.fz-juelich.de/record/904166