Electrocatalytic Water Oxidation by a Trinuclear Copper(II) Complex

Geer, Ana M. ; Musgrave III, Charles ; Webber, Christopher ; Nielsen, Robert J. ; McKeown, Bradley A. ; Liu, Chang ; Schleker, P. Philipp M. ; Jakes, Peter ; Jia, Xiaofan ; Dickie, Diane A. ; Granwehr, Josef ; Zhang, Sen ; Machan, Charles W. ; Goddard, William A. ; Gunnoe, T. Brent

Resumen: 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.

Idioma: Inglés

DOI: 10.1021/acscatal.1c01395

Año: 2021

Publicado en: ACS CATALYSIS 11, 12 (2021), 7223-7240
ISSN: 2155-5435

Factor impacto JCR: 13.7 (2021)

Categ. JCR: CHEMISTRY, PHYSICAL rank: 19 / 165 = 0.115 (2021) - Q1 - T1

Factor impacto CITESCORE: 20.8 - Chemical Engineering (Q1)

Factor impacto SCIMAGO: 4.202 - Chemistry (miscellaneous) (Q1) - Catalysis (Q1)

Tipo y forma: Article (PostPrint)