Chemical Approaches to Artificial Photosynthesis. 2

Alstrum-Acevedo, James H.; Brennaman, M. Kyle; Meyer, Thomas J.

doi:10.1021/ic050904r

Cited by 910 publications

(891 citation statements)

References 369 publications

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“…The thermodynamic efficiency of this chemistry has never been replicated in any abiotic catalyst of any kind. Unlike the reasonably well understood principles of single-electron and single-proton transfer chemistry, complex multi-electron/proton reactions control the overall energetics and thus the allowed pathway for catalysis [8,9,10]. Interested readers should also consult other recent reviews that cover in vitro and in vivo photoactivation of the WOC [11,12,13].…”

Section: Introductionmentioning

confidence: 99%

Photoassembly of the water-oxidizing complex in photosystem II

Dasgupta

Ananyev

Dismukes

2008

Coordination Chemistry Reviews

165

121

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The light-driven steps in the biogenesis and repair of the inorganic core comprising the O 2 -evolving center of oxygenic photosynthesis (photosystem II water-oxidation complex, PSII-WOC) are reviewed. These steps, known collectively as photoactivation, involve the photoassembly of the free inorganic cofactors to the cofactor-depleted PSII-(apo-WOC) driven by light and produce the active O 2 -evolving core comprised of Mn 4 CaO x Cl y . We focus on the functional role of the inorganic components as seen through the competition with non-native cofactors ("inorganic mutants") on water oxidation activity, the rate of the photoassembly reaction, and on structural insights gained from EPR spectroscopy of trapped intermediates formed in the initial steps of the assembly reaction. A chemical mechanism for the initial steps in photoactivation is given that is based on these data. Photoactivation experiments offer the powerful insights gained from replacement of the native cofactors, which together with the recent X-ray structural data for the resting holoenzyme provide a deeper understanding of the chemistry of water oxidation. We also review some new directions in research that photoactivation studies have inspired that look at the evolutionary history of this remarkable catalyst.

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Section: Introductionmentioning

confidence: 99%

Photoassembly of the water-oxidizing complex in photosystem II

Dasgupta

Ananyev

Dismukes

2008

Coordination Chemistry Reviews

165

121

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“…dye-sensitized photoelectrosynthesis cell | water oxidation | core/shell A lthough promising, significant challenges remain in the search for successful strategies for artificial photosynthesis by water splitting into oxygen and hydrogen or reduction of CO 2 to reduced forms of carbon (1)(2)(3)(4)(5). In a dye-sensitized photoelectrosynthesis cell (DSPEC), a wide band gap, nanoparticle oxide film, typically TiO 2 , is derivatized with a surface-bound molecular assembly or assemblies for light absorption and catalysis (6)(7)(8).…”

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confidence: 99%

Visible photoelectrochemical water splitting into H ₂ and O ₂ in a dye-sensitized photoelectrosynthesis cell

Alibabaei

Sherman

Norris

et al. 2015

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

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141

163

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A hybrid strategy for solar water splitting is exploited here based on a dye-sensitized photoelectrosynthesis cell (DSPEC) with a mesoporous SnO 2 /TiO 2 core/shell nanostructured electrode derivatized with a surface-bound Ru(II) polypyridyl-based chromophore-catalyst assembly. The assembly, [(4, H 2 ) 2 bpy) 2 Ru(4-Mebpy-4'-bimpy)Ru (tpy) (OH 2 dye-sensitized photoelectrosynthesis cell | water oxidation | core/shell A lthough promising, significant challenges remain in the search for successful strategies for artificial photosynthesis by water splitting into oxygen and hydrogen or reduction of CO 2 to reduced forms of carbon (1-5). In a dye-sensitized photoelectrosynthesis cell (DSPEC), a wide band gap, nanoparticle oxide film, typically TiO 2 , is derivatized with a surface-bound molecular assembly or assemblies for light absorption and catalysis (6-8). In a DSPEC, visible light is absorbed by a chromophore, initiating a series of events that culminate in water splitting: injection, intraassembly electron transfer, catalyst activation, and electron transfer to a cathode or photocathode for H 2 production. Sun and coworkers have recently demonstrated visible-light-driven water splitting with a coloading approach combining Ru(II) polypyridyl-based light absorbers and catalysts on TiO 2 (9). The efficiency of DSPEC devices is dependent on interfacial dynamics and competing kinetic processes. A major limiting factor is the requirement for accumulating multiple oxidative equivalents at a catalyst site to meet the 4e − /4H + demands for oxidizing water to dioxygen (2H 2 O -4e − -4H + → O 2 ) in competition with back electron transfer of injected electrons to the oxidized assembly.One approach to achieving structural control of local electron transfer dynamics at the oxide interface in dye-sensitized devices is by use of nanostructured core/shell electrodes (10-12). In this approach, a mesoporous network of nanoparticles is uniformly coated with a thin oxide overlayer prepared by atomic layer deposition (ALD). We have used core/shell electrodes to demonstrate benzyl alcohol dehydrogenation (13). This approach has also been used to enhance the efficiency of dye-sensitized solar cells (14,15). Recently, we described the use of a core/shell consisting of an inner core of a nanoparticle transparent conducting oxide, tin-doped indium oxide (nanoITO), and a thin outer shell of TiO 2 for water splitting by visible light (16 Fig. 1A, provided the basis for a photoanode in a DSPEC application with a Pt cathode for H 2 generation with a small applied bias in an acetate buffer at pH 4.6.Application of the core/shell structure led to a greatly enhanced efficiency for water splitting compared with mesoscopic, nanoparticle TiO 2 but the per-photon absorbed efficiency of the resulting DSPEC was relatively low and problems arose from longterm instability due to loss of the assembly from the oxide surface in the acetate buffer at pH 4.6. The latter is problematic because the rate of water oxidation is enhanced by added buffer bases...

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“…It is also a central reaction in artificial photosynthesis, an example being solardriven splitting of water into hydrogen and oxygen, 2 H 2 O 3 O 2 ϩ 2 H 2 (9)(10)(11). In natural photosynthesis, water oxidation occurs at photosystem II (PSII) through the Kok cycle after absorption of four photons.…”

mentioning

confidence: 99%

Mediator-assisted water oxidation by the ruthenium “blue dimer”cis,cis-[(bpy)₂(H₂O)RuORu(OH₂)(bpy)₂]⁴⁺

Concepcion

Jurss

Templeton

et al. 2008

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

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116

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Light-driven water oxidation occurs in oxygenic photosynthesis in photosystem II and provides redox equivalents directed to photosystem I, in which carbon dioxide is reduced. Water oxidation is also essential in artificial photosynthesis and solar fuelforming reactions, such as water splitting into hydrogen and oxygen (2 H2O ؉ 4 h 3 O2 ؉ 2 H2) or water reduction of CO2 to methanol (2 H2O ؉ CO2 ؉ 6 h 3 CH3OH ؉ 3/2 O2), or hydrocarbons, which could provide clean, renewable energy. The ''blue ruthenium dimer,'' cis,cis-[(bpy)2(H2O)Ru III ORu III (OH2)(bpy)2] 4؉ , was the first well characterized molecule to catalyze water oxidation. On the basis of recent insight into the mechanism, we have devised a strategy for enhancing catalytic rates by using kinetically facile electron-transfer mediators. Rate enhancements by factors of up to Ϸ30 have been obtained, and preliminary electrochemical experiments have demonstrated that mediator-assisted electrocatalytic water oxidation is also attainable.catalysis ͉ redox mediator ͉ electron transfer W ater oxidation is a key reaction in photosynthesis, the basis for most of life as we know it (1-8). It is also a central reaction in artificial photosynthesis, an example being solardriven splitting of water into hydrogen and oxygen, 2 H 2 O 3 O 2 ϩ 2 H 2 (9-11). In natural photosynthesis, water oxidation occurs at photosystem II (PSII) through the Kok cycle after absorption of four photons. Detailed insight into how this reaction occurs is emerging on the basis of theoretical and spectroscopic studies and recent x-ray diffraction and extended x-ray absorption fine structure results to 3.0-Å resolution (12)(13)(14).Given the demands of the half reaction, 2 H 2 O 3 O 2 ϩ 4 H ϩ ϩ 4e Ϫ , with requirements for both 4e Ϫ /4H ϩ loss and OOO bond formation, water oxidation is difficult to achieve at a single catalyst site or cluster. In addition to PSII, water oxidation is also catalyzed by the ruthenium ''blue dimer'' cis,cis-[(bpy) 2 (H 2 O)Ru III ORu III (OH 2 )(bpy) 2 ] 4ϩ (bpy is 2,2Ј-bipyridine) and structurally related derivatives (15-21) (Fig. 1). Other catalysts based on iridium and ruthenium complexes and in rutheniumcontaining polyoxometalates have been reported recently (22-25).The low oxidation state Ru III -O-Ru III form of the ruthenium blue dimer undergoes oxidative activation by proton-coupled electron transfer (PCET) in which stepwise loss of electrons and protons occurs. PCET is essential, because it allows for the buildup of multiple oxidative equivalents at a single site or cluster without building up positive charge (21, 26). As shown by the results of pH-dependent electrochemical studies (16), loss of 4e Ϫ /4H ϩ occurs to give a reactive, transient intermediate followed by O 2 evolution.In the absence of a serendipitous discovery, mechanistic knowledge is required for the design of robust, long-lived catalysts for water oxidation. Such knowledge is also important for the microscopic reverse reaction, oxygen reduction to water, which occurs at the cathode (reducing e...

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Chemical Approaches to Artificial Photosynthesis. 2

Cited by 910 publications

References 369 publications

Photoassembly of the water-oxidizing complex in photosystem II

Photoassembly of the water-oxidizing complex in photosystem II

Visible photoelectrochemical water splitting into H ₂ and O ₂ in a dye-sensitized photoelectrosynthesis cell

Mediator-assisted water oxidation by the ruthenium “blue dimer”cis,cis-[(bpy)₂(H₂O)RuORu(OH₂)(bpy)₂]⁴⁺

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Chemical Approaches to Artificial Photosynthesis. 2

Cited by 910 publications

References 369 publications

Photoassembly of the water-oxidizing complex in photosystem II

Photoassembly of the water-oxidizing complex in photosystem II

Visible photoelectrochemical water splitting into H 2 and O 2 in a dye-sensitized photoelectrosynthesis cell

Mediator-assisted water oxidation by the ruthenium “blue dimer”cis,cis-[(bpy)2(H2O)RuORu(OH2)(bpy)2]4+

Contact Info

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Visible photoelectrochemical water splitting into H ₂ and O ₂ in a dye-sensitized photoelectrosynthesis cell

Mediator-assisted water oxidation by the ruthenium “blue dimer”cis,cis-[(bpy)₂(H₂O)RuORu(OH₂)(bpy)₂]⁴⁺