TY - JOUR
T1 - Light-Driven Water Oxidation with the Ir-blue Catalyst and the Ru(bpy)3 2+/S2O8 2- Cycle
T2 - Photogeneration of Active Dimers, Electron-Transfer Kinetics, and Light Synchronization for Oxygen Evolution with High Quantum Efficiency
AU - Volpe, Andrea
AU - Tubaro, Cristina
AU - Natali, Mirco
AU - Sartorel, Andrea
AU - Brudvig, Gary W.
AU - Bonchio, Marcella
N1 - Funding Information:
A.S. thanks the Department of Chemical Sciences at the University of Padova and Fondazione Cassa di Risparmio di Padova e Rovigo for funding (Project PHOETRY, P-DiSC #10BIRD2018-UNIPD, and Project SYNERGY, Ricerca Scientifica di Eccellenza 2018). G.W.B. is thankful for funding from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award DE-SC0001059 as part of the Center for Light Energy Activated Redox Processes (LEAP), Energy Frontier Research Center.
PY - 2019/12/16
Y1 - 2019/12/16
N2 - Light-driven water oxidation is achieved with the Ru(bpy)3 2+/S2O8 2- cycle employing the highly active Ir-blue water oxidation catalyst, namely, an IrIV,IV 2(pyalc)2 μ-oxo-dimer [pyalc = 2-(2′-pyridyl)-2-propanoate]. Ir-blue is readily formed by stepwise oxidation of the monomeric Ir(III) precursor 1 by the photogenerated Ru(bpy)3 3+, with a quantum yield φ of up to 0.10. Transient absorption spectroscopy and kinetic evidence point to a stepwise mechanism, where the primary event occurs via a fast photoinduced electron transfer from 1 to Ru(bpy)3 3+, leading to the Ir(IV) monomer I1 (k1 ∼108 M-1 s-1). The competent Ir-blue catalyst is then obtained from I1 upon photooxidative loss of the Cp∗ ligand and dimerization. The Ir-blue catalyst is active in the Ru(bpy)3 2+/S2O8 2- light-driven water oxidation cycle, where it undergoes two fast photoinduced electron transfers to Ru(bpy)3 3+ [with kIr-blue = (3.00 ± 0.02) × 108 M-1 s-1 for the primary event, outperforming iridium oxide nanoparticles by ca. 2 orders of magnitude], leading to a IrV,V 2 steady-state intermediate involved in O-O bond formation. The quantum yield for oxygen evolution depends on the photon flux, showing a saturation regime and reaching an impressive value of φ(O2) = 0.32 ± 0.01 (corresponding to a quantum efficiency of 64 ± 2%) at low irradiation intensity. This result highlights the key requirement of orchestrating the rate of the photochemical events with dark catalytic turnover.
AB - Light-driven water oxidation is achieved with the Ru(bpy)3 2+/S2O8 2- cycle employing the highly active Ir-blue water oxidation catalyst, namely, an IrIV,IV 2(pyalc)2 μ-oxo-dimer [pyalc = 2-(2′-pyridyl)-2-propanoate]. Ir-blue is readily formed by stepwise oxidation of the monomeric Ir(III) precursor 1 by the photogenerated Ru(bpy)3 3+, with a quantum yield φ of up to 0.10. Transient absorption spectroscopy and kinetic evidence point to a stepwise mechanism, where the primary event occurs via a fast photoinduced electron transfer from 1 to Ru(bpy)3 3+, leading to the Ir(IV) monomer I1 (k1 ∼108 M-1 s-1). The competent Ir-blue catalyst is then obtained from I1 upon photooxidative loss of the Cp∗ ligand and dimerization. The Ir-blue catalyst is active in the Ru(bpy)3 2+/S2O8 2- light-driven water oxidation cycle, where it undergoes two fast photoinduced electron transfers to Ru(bpy)3 3+ [with kIr-blue = (3.00 ± 0.02) × 108 M-1 s-1 for the primary event, outperforming iridium oxide nanoparticles by ca. 2 orders of magnitude], leading to a IrV,V 2 steady-state intermediate involved in O-O bond formation. The quantum yield for oxygen evolution depends on the photon flux, showing a saturation regime and reaching an impressive value of φ(O2) = 0.32 ± 0.01 (corresponding to a quantum efficiency of 64 ± 2%) at low irradiation intensity. This result highlights the key requirement of orchestrating the rate of the photochemical events with dark catalytic turnover.
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U2 - 10.1021/acs.inorgchem.9b02531
DO - 10.1021/acs.inorgchem.9b02531
M3 - Article
C2 - 31774669
AN - SCOPUS:85076169207
VL - 58
SP - 16537
EP - 16545
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 24
ER -