Photocatalytic hydrogen production from water in self-assembled supramolecular iridium–cobalt systems

Jasimuddin, Sk.; Yamada, Tomoko; Fukuju, Kazunori; Otsuki, Joe; Sakai, Ken

doi:10.1039/c0cc02486d

Cited by 97 publications

(63 citation statements)

References 22 publications

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“…[150] In the presence of TEOA, these systems mediate light-driven H 2 production in CH 3 CN/H 2 O mixtures with a TON of up to 20 (Table 3, entries 9-12). H 2 generation is significantly affected by the CH 3 CN/H 2 O ratio, the TEOA concentration, and the nature of the spacer between the PS and the Co core.…”

Section: Supramolecular Cobaloximebased Photocatalystsmentioning

confidence: 99%

Splitting Water with Cobalt

2011

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The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable, and efficient systems for the conversion and storage of renewable energy sources, such as solar energy. The production of hydrogen, a fuel with remarkable properties, through sunlight-driven water splitting appears to be a promising and appealing solution. While the active sites of enzymes involved in the overall water-splitting process in natural systems, namely hydrogenases and photosystem II, use iron, nickel, and manganese ions, cobalt has emerged in the past five years as the most versatile non-noble metal for the development of synthetic H(2)- and O(2)-evolving catalysts. Such catalysts can be further coupled with photosensitizers to generate photocatalytic systems for light-induced hydrogen evolution from water.

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Section: Supramolecular Cobaloximebased Photocatalystsmentioning

confidence: 99%

Splitting Water with Cobalt

2011

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“…39 In addition to cobaloxime complexes, tris(2,2 0 -bipyridine)cobalt-(II) complex was used as catalyst in several hydrogen production systems in combination with Ru II -and Ir III -containing PSs. 27,28,40 The Journal of Physical Chemistry C ARTICLE We tried to replace the expensive noble-metal-containing PSs in these systems with commercially available cheap organic dyes, Rose Bengal (RB 2À ) and Eosins (EY 2À and EB 2À ), to build new noblemetal-free molecular catalyst systems (Figure 1). Besides the merits of being inexpensive and readily obtained, the more important advantage of these systems is that an electrostatically attractive interaction of the negatively charged xanthene dyes and the [Co(bpy) 3 42 were prepared according to the literature procedures.…”

Section: Introductionmentioning

confidence: 99%

Promoting Effect of Electrostatic Interaction between a Cobalt Catalyst and a Xanthene Dye on Visible-Light-Driven Electron Transfer and Hydrogen Production

et al. 2011

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The readily obtained noble-metal-free molecular catalyst systems, with xanthene dyes (Rose Bengal, RB 2À ; Eosin Y, EY 2À ; and Eosin B, EB 2À ) as photosensitizers, [Co(bpy) 3 ]Cl 2 as catalyst, and triethylamine as sacrificial electron donor, are highly active for visible-light-driven (λ > 450 nm) hydrogen production from water. The turnover frequency is up to 54 TON/ min versus RB 2À with a RB 2À /[Co(bpy) 3 ]Cl 2 molar ratio of 1:10 in CH 3 CN/ H 2 O under optimal conditions in the first half hour of irradiation (λ > 450 nm), and the turnover number is up to 2076 versus RB 2À . Comparative studies show the following: (1) The photocatalytic H 2 -evolving activity of the cationic cobalt complex [Co(bpy) 3 ]Cl 2 is apparently higher than the neutral cobaloxime complexes with xanthene dyes as potosensitizers, and also much higher than the analogous system of [Ru(bpy) 3 ]Cl 2 /[Co(bpy) 3 ]Cl 2 . (2) The UVÀvis absorptions of xanthene dyes are red-shifted to different extents upon addition of [Co(bpy) 3 ]Cl 2 to the aqueous or CH 3 CN/H 2 O solutions of these dyes, while no change was observed in the UVÀvis absorptions of photosensitizer with addition of the cobaloximes to the aqueous solution of RB 2À or addition of [Co(bpy) 3 ]Cl 2 to the aqueous solution of [Ru(bpy) 3 ]Cl 2 . (3) The fluorescence of RB 2À is significantly quenched by [Co(bpy) 3 ]Cl 2 , but not by the cobaloximes. These special performances of [Co(bpy) 3 ]Cl 2 are attributed to the electrostatically attractive interaction between the anionic organic dyes and the cationic cobalt catalyst. The probable mechanism for photoinduced hydrogen production catalyzed by the system of RB 2À , [Co(bpy) 3 ]Cl 2 , and triethylamine is discussed in detail on the basis of fluorescence and transient absorption spectroscopic studies.

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“…With a view toward the possible long-term utilization of hydrogen from solardriven water splitting, efforts have expanded over the past decade to use components that contain only earth-abundant elements and thus to remove Pt, Pd, Ru, Ir, and Rh from such systems. In this regard, photochemical proton reduction systems have been reported in which complexes of cobalt, nickel, and iron are found to function as catalysts for hydrogen generation (18,(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41). A number of these complexes were inspired by the active sites of hydrogenase enzymes in which Fe is, and Ni may be, present, and a pendant organic base is thought to help as a proton shuttle to a postulated metal-hydride intermediate for H 2 formation (30,31,35,37,42,43).…”

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confidence: 99%

Photogeneration of hydrogen from water using CdSe nanocrystals demonstrating the importance of surface exchange

Das

Han

Haghighi

et al. 2013

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

130

139

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Unique tripodal S-donor capping agents with an attached carboxylate are found to bind tightly to the surface of CdSe nanocrystals (NCs), making the latter water soluble. Unlike that in similarly solubilized CdSe NCs with one-sulfur or two-sulfur capping agents, dissociation from the NC surface is greatly reduced. The impact of this behavior is seen in the photochemical generation of H 2 in which the CdSe NCs function as the light absorber with metal complexes in aqueous solution as the H 2 -forming catalyst and ascorbic acid as the electron donor source. This precious-metalfree system for H 2 generation from water using [Co(bdt) 2 ]− (bdt, benzene-1,2-dithiolate) as the catalyst exhibits excellent activity with a quantum yield for H 2 formation of 24% at 520 nm light and durability with >300,000 turnovers relative to catalyst in 60 h.photochemistry | solar energy | catalysis | water splitting | quantum dots A rtificial photosynthesis (AP) represents an important strategy for energy conversion from sunlight to storage in chemical bonds (1-4). Unlike natural photosynthesis in which CO 2 + H 2 O are converted into carbohydrates and O 2 , the key energy-storing reaction in AP is the splitting of water into its constituent elements of hydrogen and oxygen (5-16). As a redox reaction, water splitting can be divided into two half-reactions, of which the light-driven generation of H 2 is the reductive component. Many systems for the photogeneration of H 2 have been described over the years and they typically consist of a light absorber, a catalyst for H 2 formation, and sources of protons and electrons. For systems that function in aqueous media, the protons are provided by water, whereas for nonaqueous systems, the protons are provided by weak, generally organic acids. The source of electrons in these photochemical systems is generally a sacrificial electron donor-that is, a compound that decomposes following one electron oxidation.Reports of the light-driven generation of hydrogen date back more than 30 y, beginning with a multicomponent system containing [Ru(bpy) 3 ] 2+ (where bpy is 2,2′-bipyridine) as the chromophore or photosensitizer (PS) and colloidal Pt as the catalyst for making H 2 from protons and electrons (17). In these and many subsequent systems, electron mediators were used to accept an electron from the excited chromophore, PS*-thereby serving as an oxidative quencher-and transfer it to the catalyst. Whereas two of the initial mediators were bpy complexes of rhodium and cobalt (17, 18), the overwhelming majority of electron mediators in these systems were dialkylated 2,2′-and 4,4′-bipyridines and their derivatives (19)(20)(21)(22). The most extensively used of these mediators was methyl viologen (MV 2+ , dimethyl-4,4′-bipyridinium, usually as its chloride salt). These mediators were subsequently found to undergo deactivation in their role by hydrogenation (23, 24). The sacrificial electron donors used in these studies depended on system pH and were generally based on compounds having tertiary amine func...

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Photocatalytic hydrogen production from water in self-assembled supramolecular iridium–cobalt systems

Cited by 97 publications

References 22 publications

Splitting Water with Cobalt

Splitting Water with Cobalt

Promoting Effect of Electrostatic Interaction between a Cobalt Catalyst and a Xanthene Dye on Visible-Light-Driven Electron Transfer and Hydrogen Production

Photogeneration of hydrogen from water using CdSe nanocrystals demonstrating the importance of surface exchange

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