Catalytic Water Oxidation by Single-Site Ruthenium Catalysts

Concepcion, Javier J.; Jurss, Jonah W.; Norris, Michael R.; Chen, Zuofeng; Templeton, Joseph L.; Meyer, Thomas J.

doi:10.1021/ic901437e

Cited by 298 publications

(350 citation statements)

References 14 publications

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“…The light blue nanoITO films were prepared with an average thickness of 5 μm with a resistance of ∼200 Ω across a 1-cm section of the film. Synthesis of 1 has been previously reported (41). Stable phosphonate surface binding of 1 on nanoITO electrodes occurred following immersion of the films in solutions containing 0.1 mM catalyst in methanol.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation

Vannucci

Alibabaei

Losego

et al. 2013

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

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127

152

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Enhancing the surface binding stability of chromophores, catalysts, and chromophore-catalyst assemblies attached to metal oxide surfaces is an important element in furthering the development of dye sensitized solar cells, photoelectrosynthesis cells, and interfacial molecular catalysis. Phosphonate-derivatized catalysts and molecular assemblies provide a basis for sustained water oxidation on these surfaces in acidic solution but are unstable toward hydrolysis and loss from surfaces as the pH is increased. Here, we report enhanced surface binding stability of a phosphonate-derivatized water oxidation catalyst over a wide pH range (1-12) by atomic layer deposition of an overlayer of TiO 2 . Increased stability of surface binding, and the reactivity of the bound catalyst, provides a hybrid approach to heterogeneous catalysis combining the advantages of systematic modifications possible by chemical synthesis with heterogeneous reactivity. For the surface-stabilized catalyst, greatly enhanced rates of water oxidation are observed upon addition of buffer bases −H 2 PO − 4 /HPO 2− 4 , B(OH) 3 /B(OH) 2 O − , HPO 2− 4 /PO 3− 4 − and with a pathway identified in which O-atom transfer to OH − occurs with a rate constant increase of 10 6 compared to water oxidation in acid.electrocatalysis | surface stabilization H eterogeneous catalysis plays an important role in industrial chemical processing, fuel reforming, and energy-producing reactions. Examples include the Haber-Bosch process, steam reforming, Ziegler-Natta polymerization, and hydrocarbon cracking (1-8). Research in heterogeneous catalysis continues to flourish (9-15) but iterative design and modification are restricted by limitations in materials preparation and experimental access to surface mechanisms. By contrast, synthetic modification of molecular catalysts is possible by readily available routes; a variety of experimental techniques is available for monitoring rates and mechanism in solution for the investigation of homogeneous catalysis (16-23). Transferring this knowledge and the reactivity of homogeneous molecular catalysts to a surface could open the door to heterogeneous applications in fuel cells, dye sensitized photoelectrochemical cells, and multiphase industrial reactions.Procedures are available for immobilization of organometallic and coordination complexes on the surfaces of solid supports. Common strategies include surface derivatization of metal oxides by carboxylate, phosphonate, and siloxane bindings (24-27), carbongrafted electrodes (28-30), and electropolymerization (31-33). These approaches provide a useful bridge to the interface and a way to translate mechanistic understanding and ease of synthetic modification of solution catalysts to heterogeneous applications with a promise of higher reactivity under milder conditions. A significant barrier to this approach arises from the limited stability of surface binding. Surface-bound carboxylates are typically unstable to hydrolysis in water, whereas phosphonates are unstable in neutral or basic...

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Section: Methodsmentioning

confidence: 99%

“…2 is initiated by accumulating multiple oxidative equivalents at the catalyst through stepwise proton coupled electron transfer (PCET) reactions, Ru II - (22,25,41).…”

Section: Ru-oh 2 2+mentioning

confidence: 99%

Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation

Vannucci

Alibabaei

Losego

et al. 2013

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

Self Cite

127

152

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“…Synthesis of catalyst 1 was reported elsewhere (38). Briefly, it was obtained by reaction of the monocationic carbene precursor ligand with RuðtpyÞCl 3 in ethylene glycol at 150°C in the presence of NEt 3 .…”

Section: Methodsmentioning

confidence: 99%

Splitting CO ₂ into CO and O ₂ by a single catalyst

Chen

Concepcion

Brennaman

et al. 2012

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

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169

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The metal complex ½ðtpyÞðMebim-pyÞRu II ðSÞ 2þ (tpy ¼ 2,2 0 : 6 0 ,2 0 0 -terpyridine; Mebim-py ¼ 3-methyl-1-pyridylbenzimidazol-2-ylidene; S ¼ solvent) is a robust, reactive electrocatalyst toward both water oxidation to oxygen and carbon dioxide reduction to carbon monoxide. Here we describe its use as a single electrocatalyst for CO 2 splitting, CO 2 → CO þ 1∕2 O 2 , in a two-compartment electrochemical cell.artificial photosynthesis | polypyridyl Ru complexes | proton coupled electron transfer | single-site catalysis | solar fuels R ising energy prices, diminishing reserves of petroleum, and environmental concerns are driving new thinking about our energy future. Given its availability, with approximately 10,000 times the daily energy input required to meet current energy consumption, solar energy could be the ultimate answer. However, solar energy is diffuse, spread over the earth's surface, and requires vast collection areas for large-scale applications (1). A more difficult challenge is the intermittency of the sun as an energy source. Meeting the challenge of providing power at night will require energy storage on massive scales at levels exceeding the ability of existing or foreseeable energy storage technologies (2, 3). The only realistic alternative is energy storage in chemical bonds and the increasingly popular concept of "solar fuels." Solar fuels mimic natural photosynthesis in using solar energy and artificial photosynthesis to convert readily available sources, water and carbon dioxide, into highenergy fuels. Target reactions include water splitting into hydrogen and oxygen and reduction of carbon dioxide to carbon monoxide, other oxygenates, or hydrocarbons (Eqs. 1-3), as follows:Carrying out these reactions presents a major challenge in chemical reactivity given their multiphoton, multielectron, multiatom character. It is reassuring that similar hurdles have been overcome in natural photosynthesis, in which light-driven reduction of CO 2 to carbohydrates by water occurs (Eq. 4). However, photosynthesis in green plants took 2-3 billion years to evolve and utilizes a complex architecture that utilizes thousands and thousands of atoms and multiple integrated assemblies (4, 5).A simplifying factor, suggesting a mechanistic approach, comes with recognition that the target energy storage reactions can be split into constituent "half reactions" which are shown for CO 2 splitting in Eqs. 5 and 6. Photosynthesis in green plants occurs in the thylakoid membrane and uses physically separated molecular assemblies for light-driven water oxidation (Photosystem II) and CO 2 reduction (Photosystem I and the Calvin cycle) (6, 7). Electron/proton equilibration occurs by intra-or transmembrane electron/proton transfer channels driven by free energy gradients.Application of a "half-reaction" strategy in artificial photosynthesis poses similar challenges. In both water oxidation and CO 2 reduction, mechanisms involving one-electron reactions are energetically untenable. They result in • OH on oxidation or CO 2•− o...

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“…Single-site water oxidation catalysis has progressed rapidly [58][59][60]. Multiple Ru-based catalysts have been identified and characterized based on a variety of ligand sets.…”

Section: Single-site Water Oxidationmentioning

confidence: 99%

“…9 on nanoITO has been studied in detail [59,61]. NanoITO, a new material, developed in the UNC Energy Frontier Research Center (EFRC), is both optically transparent and conductive.…”

Section: Single-site Water Oxidationmentioning

confidence: 99%

Making solar fuels by artificial photosynthesis

Song

Chen

Brennaman

et al. 2011

Pure and Applied Chemistry

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110

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Abstract:In order for solar energy to serve as a primary energy source, it must be paired with energy storage on a massive scale. At this scale, solar fuels and energy storage in chemical bonds is the only practical approach. Solar fuels are produced in massive amounts by photosynthesis with the reduction of CO 2 by water to give carbohydrates but efficiencies are low. In photosystem II (PSII), the oxygen-producing site for photosynthesis, light absorption and sensitization trigger a cascade of coupled electron-proton transfer events with time scales ranging from picoseconds to microseconds. Oxidative equivalents are built up at the oxygen evolving complex (OEC) for water oxidation by the Kok cycle. A systematic approach to artificial photo synthesis is available based on a "modular approach" in which the separate functions of a final device are studied separately, maximized for rates and stability, and used as modules in constructing integrated devices based on molecular assemblies, nanoscale arrays, self-assembled monolayers, etc. Considerable simplification is available by adopting a "dyesensitized photoelectrosynthesis cell" (DSPEC) approach inspired by dye-sensitized solar cells (DSSCs). Water oxidation catalysis is a key feature, and significant progress has been made in developing a single-site solution and surface catalysts based on polypyridyl complexes of Ru. In this series, ligand variations can be used to tune redox potentials and reactivity over a wide range. Water oxidation electrocatalysis has been extended to chromophorecatalyst assemblies for both water oxidation and DSPEC applications.

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Catalytic Water Oxidation by Single-Site Ruthenium Catalysts

Cited by 298 publications

References 14 publications

Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation

Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation

Splitting CO ₂ into CO and O ₂ by a single catalyst

Making solar fuels by artificial photosynthesis

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Catalytic Water Oxidation by Single-Site Ruthenium Catalysts

Cited by 298 publications

References 14 publications

Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation

Crossing the divide between homogeneous and heterogeneous catalysis in water oxidation

Splitting CO 2 into CO and O 2 by a single catalyst

Making solar fuels by artificial photosynthesis

Contact Info

Product

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Splitting CO ₂ into CO and O ₂ by a single catalyst