Highly active and tunable catalysts for O2 evolution from water based on mononuclear ruthenium(ii) monoaquo complexes

Yagi, Masayuki; Tajima, Shunji; Komi, Manabu; Yamazaki, Hirosato

doi:10.1039/c0dt01826k

Cited by 101 publications

(122 citation statements)

References 38 publications

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“…Using the [Ru II (tpy)(bpy)(H 2 O)] 2+ scaffold, Berlinguette et al [19,40] and Yagi et al [41] provided direct evidence of how catalytic water oxidation is affected by modified electronic properties of mononuclear aqua-Ru polypyridyl complexes. Electronic modification of the [Ru II (tpy)(bpy)(H 2 O)] 2+ scaffold was achieved by decorating the bpy and tpy ligands with various electron-withdrawing and donating substituents (Chart 5, complexes 11-22).…”

Section: Ruthenium Complexes With An Axial Aqua Ligandmentioning

confidence: 98%

Role of ligands in catalytic water oxidation by mononuclear ruthenium complexes

Zeng

Lewis

Harwood

et al. 2015

Coordination Chemistry Reviews

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Section: Ruthenium Complexes With An Axial Aqua Ligandmentioning

confidence: 98%

Role of ligands in catalytic water oxidation by mononuclear ruthenium complexes

Zeng

Lewis

Harwood

et al. 2015

Coordination Chemistry Reviews

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“…Although water oxidation catalyst is necessary to extract electrons from water (as an electron source) for producing high energy compounds in artificial photosynthesis, development of an efficient and robust water oxidation catalyst is a bottleneck and very important task to bring a breakthrough in the field. In a recent decade, a variety of metal complexes based on manganese, [4][5][6][7][8] ruthenium [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and iridium [29][30][31][32], iron [33,34], cupper [35][36][37] and cobalt [38][39][40][41] have been reported as active catalysts for water oxidation. The catalyses by ruthenium complexes are studied most extensively.…”

Section: Introductionmentioning

confidence: 99%

“…Results and discussion CV of a 1 aqueous solution provided two redox waves at E 1/2 = 0.54 and 0.66 V [48] at pH = 5.3 in a potential range from 0.4 to 0.9 V (Figure 1), both of which are pH-dependent in a range of pH = 2.0 ~ 10.5. The both redox waves are assigned to the 7proton-coupled redox reactions of Ru II -OH 2 / Ru III -OH and Ru III -OH / Ru IV =O according to Pourbaix Diagram of 1 reported earlier, respectively [24]. The anodic current density rose at 1.1 V due to water oxidation (theoretical potential for water oxidation at pH 5.3, 0.68 V vs SCE), and the current density reached 2.8 mA cm -2 at 1.5 V, which was 8 times higher than that (0.36 mA cm -2 ) of the blank (without complex).Bulk electrolysis was conducted in the 1 solution at 1.5 V(Figure 2).…”

mentioning

confidence: 99%

Spectroelectrochemical investigation of electrocatalytic water oxidation by a mononuclear ruthenium complex in a homogeneous solution

Honta

Tajima

Sato

et al. 2015

Journal of Photochemistry and Photobiology A: Chemistry

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investigation of electrocatalytic water oxidation by a mononuclear ruthenium complex in a homogeneous solution, Journal of Photochemistry and Photobiology A: Chemistry http://dx.2 Highlight • Electrocatalytic water oxidation was studied by Potential-step chronocoulospectrometry. • [Ru(EtOtpy)(bpy)OH 2 ] 2+ can work for electrocatalytic water oxidation under weakly acidic conditions. • The rate-determining step for the electrocatalysis is oxidation of Ru IV =O to Ru V =O species. Abstract Electrochemical water oxidation by [Ru(EtOtpy)(bpy)OH 2 ] 2+ (1) (EtOtpy = 4'-ethoxy-2,2':6'2''-terpyridine, bpy = 2,2'-bipydidine) was investigated in a homogeneous solution under weakly acidic conditions (pH = 5.3). The cyclic voltammogram of a 1 aqueous solution showed that successive proton-coupled electron transfer reactions of Ru II -OH 2 / Ru III -OH and Ru III -OH / Ru IV =O redox pairs and high anodic current above 1.1 V vs SCE. Electrocatalytic water oxidation was corroborated by the bulk electrolysis at 1.5 V; the significant amount of O 2 was evolved compared with the blank during the electrolysis. Potential-step chronocoulospectrometry (PSCCS) from 0.0 V to 1.52 V vs SCE was conducted to observe the change of 1 in solution during the electrocatalysis. The in situ UV visible spectral change showed oxidation of 1 (Ru II -OH 2 ) to Ru III -OH and to further oxidation of Ru III -OH to Ru IV =O, and that the Ru IV =O species mainly exists in a steady state after 200 s in the electrocatalysis. The in situ UV visible spectral change in a reverse potential step from 1.52 V to 0.22 V vs SCE exhibited that Ru II -OH 2 completely recovers by 2 electron re-reduction process from the steady state in the electrocatalysis. The observation of Ru IV =O in a steady state suggests that a rate determining step in the catalytic cycle is oxidation of Ru IV =O to Ru V =O rather than the O-O bonding formation by nucleophilic attack of water to Ru V =O in the 3 electrocatalysis in a homogeneous solution.

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“…5). This large TON number is about 100 times higher than ½RuðterpyÞðbpyÞðOH 2 Þ 2þ (terpy ¼ 2; 2 0 ∶6 0 ; 2 00 -terpyridine; bpy ¼ 2; 2 0 -bipyridine) type complexes (26)(27)(28), the Ru-Hbpp [Hbpp ¼ 2; 6-bis(pyridyl)pyrazole] WOC (29), and our Ru-pdc (pdc ¼ 2; 6-pyridinedicarboxylate) complexes (30), and five times higher than the robust Ir-Cp* (Cp Ã ¼ C 5 Me 5 ) WOCs (8) and our dinuclear Ru complex (31). The specific lifetime of selected Ru-bda complexes under the given conditions as well as the free energy values of the ligand exchange reaction are collected in Table 1 and plotted in Fig.…”

Section: Vs Nhementioning

confidence: 99%

Highly efficient and robust molecular ruthenium catalysts for water oxidation

Duan

Araújo

Ahlquist

et al. 2012

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

213

199

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Water oxidation catalysts are essential components of light-driven water splitting systems, which could convert water to H 2 driven by solar radiation (H 2 O þ hν → 1∕2O 2 þ H 2 ). The oxidation of water (H 2 O → 1∕2O 2 þ 2H þ þ 2e − ) provides protons and electrons for the production of dihydrogen (2H þ þ 2e − → H 2 ), a clean-burning and high-capacity energy carrier. One of the obstacles now is the lack of effective and robust water oxidation catalysts. Aiming at developing robust molecular Ru-bda (H 2 bda ¼ 2,2 0 -bipyridine-6,6′-dicarboxylic acid) water oxidation catalysts, we carried out density functional theory studies, correlated the robustness of catalysts against hydration with the highest occupied molecular orbital levels of a set of ligands, and successfully directed the synthesis of robust Ru-bda water oxidation catalysts. A series of mononuclear ruthenium complexes ½RuðbdaÞL 2 (L ¼ pyridazine, pyrimidine, and phthalazine) were subsequently synthesized and shown to effectively catalyze Ce IV -driven ½Ce IV ¼ CeðNH 4 Þ 2 ðNO 3 Þ 6 water oxidation with high oxygen production rates up to 286 s −1 and high turnover numbers up to 55,400.catalysis | density function theory | seven coordination | photosystem II | solar fuels I n pursuit of sustainable energy systems such as solar fuels, much effort has been spent on water splitting to hydrogen and oxygen since hydrogen is a potential clean energy carrier and water is an abundant and environmentally benign resource (1-5). Water splitting consists of two half reactions: (i) water oxidationIn practice, an overpotential is always present, leading to an even higher applied potential. The former half reaction requires strongly oxidizing conditions and is generally considered as the bottleneck of the whole water-splitting process due to the multiple protonelectron transfers and the formation of the O─O bond. Over the last few years, there has been an increasing development of water oxidation catalysts (WOCs) and many transition metal-based catalysts, including Ru (4, 5), Ir (6-8), Co (9-13), Fe (14,15), and Mn (16-18), have been reported with oxygen production rates (OPRs: mole oxygen produced per mole catalyst per second) ≤5 s −1 . Very recently, we reported a family of highly active Ru-based WOCs ½RuðbdaÞL 2 (H 2 L ¼ 2;2 -bipyridine-6,6′-dicarboxylic acid; L ¼ 4-picoline, A; L ¼ isoquinoline, B) ( Fig. 1) with OPRs up to 300 s −1 (19, 20); a seven-coordinate dimeric Ru IV intermediate (D7Ru IV ) (Fig. 1) is involved in the O─O bond formation step (20,21).A general problem encountered in molecular WOCs is the decomposition of catalysts. Ligand dissociation and oxidative decomposition have been considered as the major deactivation pathways. The groups of Llobet, Meyer, and Sun have demonstrated an improved durability of their catalysts by immobilizing catalysts on the electrode/material surface and thereby dramatically suppressing the intermolecular oxidative decomposition pathway (22-25).For our Ru-bda catalysts, the main deactivation pathway has been found to b...

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Highly active and tunable catalysts for O2 evolution from water based on mononuclear ruthenium(ii) monoaquo complexes

Cited by 101 publications

References 38 publications

Role of ligands in catalytic water oxidation by mononuclear ruthenium complexes

Role of ligands in catalytic water oxidation by mononuclear ruthenium complexes

Spectroelectrochemical investigation of electrocatalytic water oxidation by a mononuclear ruthenium complex in a homogeneous solution

Highly efficient and robust molecular ruthenium catalysts for water oxidation

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