Light-Driven Water Oxidation with the Ir-blue Catalyst and the Ru(bpy)3 2+/S2O8 2- Cycle: Photogeneration of Active Dimers, Electron-Transfer Kinetics, and Light Synchronization for Oxygen Evolution with High Quantum Efficiency

Andrea Volpe, Cristina Tubaro, Mirco Natali, Andrea Sartorel, Gary W. Brudvig, Marcella Bonchio

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish
JournalInorganic Chemistry
DOIs
Publication statusAccepted/In press - Jan 1 2019

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Quantum efficiency
Dimers
quantum efficiency
synchronism
Synchronization
electron transfer
dimers
Oxygen
catalysts
Oxidation
oxidation
cycles
Catalysts
Kinetics
Electrons
Water
kinetics
oxygen
water
Quantum yield

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

@article{54a5ad7566804b62abb765cbe0a720f9,
title = "Light-Driven Water Oxidation with the Ir-blue Catalyst and the Ru(bpy)3 2+/S2O8 2- Cycle: Photogeneration of Active Dimers, Electron-Transfer Kinetics, and Light Synchronization for Oxygen Evolution with High Quantum Efficiency",
abstract = "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.",
author = "Andrea Volpe and Cristina Tubaro and Mirco Natali and Andrea Sartorel and Brudvig, {Gary W.} and Marcella Bonchio",
year = "2019",
month = "1",
day = "1",
doi = "10.1021/acs.inorgchem.9b02531",
language = "English",
journal = "Inorganic Chemistry",
issn = "0020-1669",
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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

PY - 2019/1/1

Y1 - 2019/1/1

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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