Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces

Raber, McKenzie M.; Brady, Matthew D.; Troian‐Gautier, Ludovic; Dickenson, John C.; Marquard, Seth L.; Hyde, Jacob T.; Lopez, Santiago J.; Meyer, Gerald J.; Meyer, Thomas J.; Harrison, Daniel P.

doi:10.1021/acsami.8b04587

Cited by 17 publications

(16 citation statements)

References 55 publications

(75 reference statements)

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“…The following materials were purchased from the indicated supplier and used without further purification: acetonitrile (CH 3 CN, Brudick and Jackson, spectrochemical grade), lithium perchlorate (LiClO 4 , Aldrich, 99.99%), argon (Airgas, 99.999%), titanium(IV) isopropoxide (Aldrich, 97%), zirconium(IV) isopropoxide (Aldrich, 99.9%), tin(IV) dioxide nanoparticles (15 wt % in H 2 O, 15 nm diameter, Alfa Aesar); In 2 O 3 :Sn (ITO) nanoparticles (TC8 DE, 20 wt % in ethanol, Evonik Industries); fluorine-doped tin(IV) oxide-coated glass (FTO, Hartford Glass Co., Inc., 2.3 mm thick, 15Ω/□). The following compounds were synthesized as previously described: [Ru(bpy) 2 (P)]Br 2 (RuP) and [Ru(bpz) 2 (P)]Br 2 [Ru(bpz)], where bpy is 2,2′-bipyridine, bpz is 2,2′-bipyrazine, and P is 2,2′-bipyridyl-4,4′-diphosphonic acid (Scheme ).…”

Section: Methodsmentioning

confidence: 99%

Factors that Control the Direction of Excited-State Electron Transfer at Dye-Sensitized Oxide Interfaces

Bangle

Meyer

2019

J. Phys. Chem. C

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Molecular excited states at conductive and semiconductive interfaces were found to transfer an electron to the oxide (injection) or accept an electron from the oxide (hole transfer). The direction of this electron transfer was determined by the energetic overlap of the metal oxide and sensitizer redox-active states and their electronic coupling. Potentiostatically controlled mesoporous thin films based on a nanocrystalline conductive metal oxide [tin-doped indium oxide (ITO)] and semiconducting metal oxides (TiO2 and SnO2) were utilized with the sensitizers (S) [Ru(bpy)2(P)]Br2 and [Ru(bpz)2(P)]Br2, where bpy is 2,2′-bipyridine, bpz is 2,2′-bipyrazine, and P is 2,2′-bipyridyl-4,4′-diphosphonic acid. For dye-sensitized TiO2, excited-state injection [TiO2|S* → TiO2(e–)|S+] was exclusively observed, and the injection yield decreased at negative applied potentials. In contrast, evidence for both injection [ITO|S* → ITO(e–)|S+] and hole transfer ([ITO|S* → ITO(h+)|S–] is reported for ITO and SnO2. Hole transfer became more efficient with negative applied potentials. The direction of electron flow between the metal oxide and excited state sensitizer was correlated with the energetic overlap and the electronic coupling as predicted by Marcus−Gerischer theory. The data reveal that control of the Fermi level enables conductive oxides to function as a photocathode or as a photoanode for solar energy conversion applications.

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Section: Methodsmentioning

confidence: 99%

Factors that Control the Direction of Excited-State Electron Transfer at Dye-Sensitized Oxide Interfaces

Bangle

Meyer

2019

J. Phys. Chem. C

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“…Past pH ∼ 11, cyclic voltammetry measurements revealed a rapid and irreversible loss in current response for the surfacebound catalyst during electrochemical scans between 0.2 and 1.6 V (vs. NHE). The loss of catalytic activity was not due to surface detachment from hydrolysis but, rather, arises from ligand decomposition or other degradation pathways involving the complex (40)(41)(42)(43). To avoid complexities at higher pH, subsequent detailed investigations were conducted at pH ∼ 7.5.…”

Section: O(h)h-b!mentioning

confidence: 99%

Crossing the bridge from molecular catalysis to a heterogenous electrode in electrocatalytic water oxidation

Nayak

Shao

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Significant progress has been made in designing single-site molecular Ru(II)-polypyridyl-aqua catalysts for homogenous catalytic water oxidation. Surface binding and transfer of the catalytic reactivity onto conductive substrates provides a basis for heterogeneous applications in electrolytic cells and dye-sensitized photoelectrosynthesis cells (DSPECs). Earlier efforts have focused on phosphonic acid (-PO3H2) or carboxylic acid (-CO2H) bindings on oxide surfaces. However, issues remain with limited surface stabilities, especially in aqueous solutions at higher pH under conditions that favor water oxidation by reducing the thermodynamic barrier and accelerating the catalytic rate using atom-proton transfer (APT) pathways. Here, we address the problem by combining silane surface functionalization and surface reductive electropolymerization on mesoporous, nanofilms of indium tin oxide (ITO) on fluorine-doped tin oxide (FTO) substrates (FTO|nanoITO). FTO|nanoITO electrodes were functionalized with vinyltrimethoxysilane (VTMS) to introduce vinyl groups on the electrode surfaces by silane attachment, followed by surface electropolymerization of the vinyl-derivatized complex, [RuII(Mebimpy)(dvbpy)(OH2)]2+ (12+; Mebimpy: 2,6-bis(1-methyl-1H-benzo[d]imidazol-2-yl)pyridine; dvbpy: 5,5′-divinyl-2,2′-bipyridine), in a mechanism dominated by a grafting-through method. The surface coverage of catalyst 12+ was controlled by the number of electropolymerization cycles. The combined silane attachment/cross-linked polymer network stabilized 12+ on the electrode surface under a variety of conditions especially at pH > ∼6. Surface-grafted poly12+ was stable toward redox cycling at pH ∼ 7.5 over an ∼4-h period. Sustained heterogeneous electrocatalytic water oxidation by the electrode gave steady-state currents for at least ∼6 h with a Faradaic efficiency of ∼68% for O2 production.

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“…The oxidized photocatalyst is then regenerated through halide oxidation. Recently, a relationship between stability of the oxidized photocatalyst and E 1/2 has been revealed under conditions that mimic photocatalyst regeneration in DSSCs and DSPECs. , The two electrodes are separated by a proton-exchange membrane, allowing for selective H + diffusion and preventing X 2 to reach the platinum electrode.…”

Section: Introduction Background and Motivationmentioning

confidence: 99%

Halide Photoredox Chemistry

et al. 2019

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Halide photoredox chemistry is of both practical and fundamental interest. Practical applications have largely focused on solar energy conversion with hydrogen gas, through HX splitting, and electrical power generation, in regenerative photoelectrochemical and photovoltaic cells. On a more fundamental level, halide photoredox chemistry provides a unique means to generate and characterize one electron transfer chemistry that is intimately coupled with X−X bond-breaking and -forming reactivity. This review aims to deliver a background on the solution chemistry of I, Br, and Cl that enables readers to understand and utilize the most recent advances in halide photoredox chemistry research. These include reactions initiated through outer-sphere, halide-to-metal, and metal-toligand charge-transfer excited states. Kosower's salt, 1-methylpyridinium iodide, provides an early outer-sphere charge-transfer excited state that reports on solvent polarity. A plethora of new inner-sphere complexes based on transition and main group metal halide complexes that show promise for HX splitting are described. Long-lived charge-transfer excited states that undergo redox reactions with one or more halogen species are detailed. The review concludes with some key goals for future research that promise to direct the field of halide photoredox chemistry to even greater heights. CONTENTS 1. Introduction, Background, and Motivation

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Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces

Cited by 17 publications

References 55 publications

Factors that Control the Direction of Excited-State Electron Transfer at Dye-Sensitized Oxide Interfaces

Factors that Control the Direction of Excited-State Electron Transfer at Dye-Sensitized Oxide Interfaces

Crossing the bridge from molecular catalysis to a heterogenous electrode in electrocatalytic water oxidation

Halide Photoredox Chemistry

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