Catalytic Mechanism of Water Oxidation with Single-Site Ruthenium–Heteropolytungstate Complexes

Murakami, Masato; Hong, Dachao; Suenobu, Tomoyoshi; Yamaguchi, Satoru; Ogura, Takashi; Fukuzumi, Shunichi

doi:10.1021/ja2024965

Cited by 201 publications

(215 citation statements)

References 112 publications

Supporting

Mentioning

203

Contrasting

Unclassified

Order By: Relevance

“…Indeed a single-site Ru-POM molecule was recently shown to catalyze the oxidation of water in the homogeneous phase (34), suggesting that cycle D could be a common mechanism at play on both single-and multicenter catalysts. Although the thermodynamic efficiency of the Ru 4 -POM can be controlled by only one or two sites, the presence of multiple metal centers clearly plays an important function, as shown by the significantly superior performance of Ru 4 -POM (13,14) compared with the single center catalysts (34).…”

Section: Atomistic and Thermodynamic Origins Of Catalytic Efficiency:mentioning

confidence: 99%

“…Although the thermodynamic efficiency of the Ru 4 -POM can be controlled by only one or two sites, the presence of multiple metal centers clearly plays an important function, as shown by the significantly superior performance of Ru 4 -POM (13,14) compared with the single center catalysts (34). The difference in their efficiency is likely to arise from the local environment around the active sites, shaped and reinforced by the metal-oxo connectivity among them.…”

Section: Atomistic and Thermodynamic Origins Of Catalytic Efficiency:mentioning

confidence: 99%

See 1 more Smart Citation

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium–oxo molecular complex

Piccinin

Sartorel

Aquilanti

et al. 2013

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

106

View full text Add to dashboard Cite

Solar-to-fuel energy conversion relies on the invention of efficient catalysts enabling water oxidation through low-energy pathways. Our aerobic life is based on this strategy, mastered by the natural Photosystem II enzyme, using a tetranuclear Mn-oxo complex as oxygen evolving center. Within artificial devices, water can be oxidized efficiently on tailored metal-oxide surfaces such as RuO 2 . The quest for catalyst optimization in vitro is plagued by the elusive description of the active sites on bulk oxides. Although molecular mimics of the natural catalyst have been proposed, they generally suffer from oxidative degradation under multiturnover regime. Here we investigate a nano-sized Ru 4 -polyoxometalate standing as an efficient artificial catalyst featuring a totally inorganic molecular structure with enhanced stability. Experimental and computational evidence reported herein indicates that this is a unique molecular species mimicking oxygenic RuO 2 surfaces. Ru 4 -polyoxometalate bridges the gap between homogeneous and heterogeneous water oxidation catalysis, leading to a breakthrough system. Density functional theory calculations show that the catalytic efficiency stems from the optimal distribution of the free energy cost to form reaction intermediates, in analogy with metal-oxide catalysts, thus providing a unifying picture for the two realms of water oxidation catalysis. These correlations among the mechanism of reaction, thermodynamic efficiency, and local structure of the active sites provide the key guidelines for the rational design of superior molecular catalysts and composite materials designed with a bottom-up approach and atomic control.artificial photosynthesis | ab initio simulations | X-ray absorption spectroscopy | electrocatalysis P hotocatalytic water splitting offers a bioinspired strategy for replacing fossil fuels with clean energy vectors (1-3). The overall reaction entails a sequence of light-promoted electron and proton transfers coupled with cleavage and formation of molecular bonds, ultimately splitting H 2 O molecules into O 2 and H 2 . The application of such technology for a viable solar-fuel economy is at the forefront of a very intense research effort. The main issue is the design and optimization of innovative catalysts enabling the half reaction of water oxidation (2H 2 O → O 2 + 4H + + 4e − ) (1) at low overpotential, high turnover frequencies, and longterm operation stability. Considering its high thermodynamic cost [E 0 = −1.23 V at pH = 0 vs. normal hydrogen electrode (NHE)] and mechanistic complexity, water oxidation catalysis (WOC) poses severe challenges for artificial photosynthesis applications.In plants, water oxidation is catalyzed by the Mn 4 CaO 4 oxygen evolving complex of Photosystem II (PSII) enzymes. The natural catalyst exhibits a functional asset of four redox active metal centers with adjacent μ-oxo bridges to enable water oxidation with a maximal turnover frequency of 400 s −1 per O 2 molecule (4). The drawback lies in the intrinsic weakness of the biol...

show abstract

Section: Atomistic and Thermodynamic Origins Of Catalytic Efficiency:mentioning

confidence: 99%

Section: Atomistic and Thermodynamic Origins Of Catalytic Efficiency:mentioning

confidence: 99%

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium–oxo molecular complex

Piccinin

Sartorel

Aquilanti

et al. 2013

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

106

View full text Add to dashboard Cite

show abstract

“…1], both in solution and on surfaces, reveal mechanisms in which stepwise oxidative activation of aqua precursors to Ru V =O is followed by rate-limiting O-O bond formation (10)(11)(12)(13)(14)(15). The results of kinetic and mechanistic studies have revealed the importance of concerted atom-proton transfer (APT) in the O-O bond-forming step.…”

mentioning

confidence: 99%

Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

Song

Concepcion

Binstead

et al. 2015

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

129

166

View full text Add to dashboard Cite

In aqueous solution above pH 2.4 with 4% (vol/vol) CH 3 CN, the complex [Ru II (bda)(isoq) 2 ] (bda is 2,2′-bipyridine-6,6′-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [Ru II (CO 2 -bpy-CO 2 − )(isoq) 2 (NCCH 3 )], as shown by 1 H and 13 C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO 4 3-, the calculated half-time for water oxidation is ∼7 μs. The key to the rate accelerations with added bases is direct involvement of the buffer base in either atom-proton transfer (APT) or concerted electron-proton transfer (EPT) pathways. [Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy is 2,2′-bipyridine; Fig. 1], both in solution and on surfaces, reveal mechanisms in which stepwise oxidative activation of aqua precursors to Ru V =O is followed by rate-limiting O-O bond formation (10-15). The results of kinetic and mechanistic studies have revealed the importance of concerted atom-proton transfer (APT) in the O-O bond-forming step. In APT, the O-O bond forms in concert with H + transfer to water or to an added base (11,12,(16)(17)(18)(19). APT can promote dramatic rate enhancements. In a recent study on surface-bound [Ru(Mebimpy)(4,4′-((HO) 2 OPCH 2 ) 2 bpy)(OH 2 )] 2+ [4,4′-((HO) 2 OPCH 2 ) 2 bpy is 4,4′-bis-methlylenephosphonato-2,2′-bipyridine] stabilized by atomic layer deposition, a rate enhancement of ∼10 6 was observed with 0.012 M added PO 4 3− at pH 12 compared with oxidation at pH 1 (20).Sun and coworkers (21, 22) have described the Ru single-site water oxidation catalysts, [Ru II (bda)(L) 2 ] (H 2 bda is 2,2′-bipyridine-6,6′-dicarboxylic acid, HCO 2 -bpy-CO 2 H; L is isoquinoline, 4-picoline, or phthalazine). They undergo rapid and sustained water oxidation catalysis with added Ce IV . A mechanism has been proposed in which initial oxidation to seven coordinate Ru IV is followed by further oxidation to Ru V (O) with O-O coupling to give a peroxo-bridged intermediate, Ru IV O-ORu IV , which undergoes further oxidation and release of O 2 (21, 22). We report here the results of a rate and mechanistic study on electrochemical water oxidation by complex [1], [Ru II (CO 2 -bpy-CO 2 )(isoq) 2 ] (isoq is isoquinoline) (Fig. 1). Evidence is presented for water oxidation by a chelate open form in acidic solutions. The chelate open form displays dramatic rate enhancements with added buffer bases, and the results of a detailed mechanistic study are reported here. − /HPO 4 2− phosphate buffer, I = 0.5 M (NaClO 4 )] in 4% (vol/vol) CH 3 CN at a glassy carbon electrode (GC) (0.071 cm 2 ). The Ag/AgCl [3 M NaCl, 0.21 V vs. normal hydrogen electrode (NHE)] reference electrode was isolated with an electrolyte filled bridge to avoid chloride ion diffusion into the anode compartment. The sample was purged with argon to remove O 2 before each scan, with only O 2 freshly produced in oxidative scans detected on reverse scans at -0.3 V vs. NHE, a...

show abstract

“…[3,6] Seitdem wurden einige Strukturvariationen entwickelt, [7] und außer Stickstoffdonoren wurden auch stabile Carbenliganden [8] sind ebenfalls in der Wasseroxidation aktiv. [14] Trotz des Fehlens organischer Liganden, die anfällig für oxidative Zersetzung sind, waren die Turnover-Zahlen niedrig (50).…”

Section: Rutheniumkomplexeunclassified

Einkernige Katalysatoren zur Wasseroxidation

Hetterscheid

Reek

2012

Angewandte Chemie

View full text Add to dashboard Cite

Vor Kurzem wurde eine Reihe einkerniger Wasseroxidationskatalysatoren beschrieben – ein Durchbruch angesichts der Lehrmeinung, dass mindestens zwei Metallzentren für eine effiziente Wasseroxidation erforderlich wären. Dieser Kurzaufsatz bietet einen Überblick über die einkernigen Katalysatoren, die innerhalb der letzten fünf Jahre beschrieben wurden. Vorgestellt wird auch ihr Einsatz in einem Prototyp, der eine Kopplung der Bildung von molekularem Sauer‐ und Wasserstoff ermöglicht.

show abstract

Catalytic Mechanism of Water Oxidation with Single-Site Ruthenium–Heteropolytungstate Complexes

Cited by 201 publications

References 112 publications

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium–oxo molecular complex

Water oxidation surface mechanisms replicated by a totally inorganic tetraruthenium–oxo molecular complex

Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

Einkernige Katalysatoren zur Wasseroxidation

Contact Info

Product

Resources

About