Cobalt complexes as artificial hydrogenases for the reductive side of water splitting

Eckenhoff, William T.; McNamara, William R.; Du, Pingwu; Eisenberg, Richard

doi:10.1016/j.bbabio.2013.05.003

Cited by 181 publications

(135 citation statements)

References 102 publications

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“…This system also was found to function via reductive quenching of PS* by the electron donor, rather than by direct electron transfer from PS* to the catalyst or an electron mediator (37). A significant number of reviews provide detailed accounts of the various systems studied and their effectiveness with regard to H 2 generation (1,(58)(59)(60)(61)(62)(63)(64). However, all of them, which contain molecular light absorbers [charge transfer (CT) metal complexes and organic dyes], suffer from photoinstability during prolonged irradiation.…”

Section: Significancementioning

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.

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129

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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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Section: Significancementioning

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.

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129

139

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“…To differentiate our article from other reviews, [19][20][21][22][23][24][25][26][27][28][29][30][31] we emphasize elucidation of mechanisms employed by homogeneous catalysts, especially those incorporating cobalt. Additionally, we discuss recent work on Ni-Mo composites as earth-abundant heterogeneous catalysts for solar-driven hydrogen evolution.…”

Section: 17mentioning

confidence: 99%

Earth-abundant hydrogen evolution electrocatalysts

et al. 2014

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Splitting water to hydrogen and oxygen is a promising approach for storing energy from intermittent renewables, such as solar power. Efficient, scalable solar-driven electrolysis devices require active electrocatalysts made from earth-abundant elements. In this mini-review, we discuss recent investigations of homogeneous and heterogeneous hydrogen evolution electrocatalysts, with emphasis on our own work on cobalt and iron complexes and nickel-molybdenum alloys.

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“…As a redox reaction, water splitting has been studied primarily in terms of its two halfreactions, the reduction of aqueous protons to H 2 and the oxidation of water to O 2 (2-13). Whereas some of these studies date back more than 30 y (14-22), recent progress on each halfreaction has been notable, particularly with regard to catalyst development and mechanistic understanding of each transformation (6,(23)(24)(25)(26)(27)(28)(29). In this paper, we focus on efforts dealing with the lightdriven generation of H 2 , which in its simplest form requires a light absorber or photosensitizer (PS) for electron-hole creation, a means or pathway for charge separation and electron transfer, an aqueous proton source, a catalyst for collecting electrons and protons and promoting their conversion to H 2 , and an ultimate source of electrons in the form of an electron donor.…”

mentioning

confidence: 99%

Light-driven generation of hydrogen: New chromophore dyads for increased activity based on Bodipy dye and Pt(diimine)(dithiolate) complexes

Zheng

Sabatini

et al. 2015

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

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New dyads consisting of a strongly absorbing Bodipy (dipyrromethene-BF 2 ) dye and a platinum diimine dithiolate (PtN 2 S 2 ) charge transfer (CT) chromophore have been synthesized and studied in the context of the light-driven generation of H 2 from aqueous protons. In these dyads, the Bodipy dye is bonded directly to the benzenedithiolate ligand of the PtN 2 S 2 CT chromophore. Each of the new dyads contains either a bipyridine (bpy) or phenanthroline (phen) diimine with an attached functional group that is used for binding directly to TiO 2 nanoparticles, allowing rapid electron photoinjection into the semiconductor. The absorption spectra and cyclic voltammograms of the dyads show that the spectroscopic and electrochemical properties of the dyads are the sum of the individual chromophores (Bodipy and the PtN 2 S 2 moieties), indicating little electronic coupling between them. Connection to TiO 2 nanoparticles is carried out by sonication leading to in situ attachment to TiO 2 without prior hydrolysis of the ester linking groups to acids. For H 2 generation studies, the TiO 2 particles are platinized (Pt-TiO 2 ) so that the light absorber (the dyad), the electron conduit (TiO 2 ), and the catalyst (attached colloidal Pt) are fully integrated. It is found that upon 530 nm irradiation in a H 2 O solution (pH 4) with ascorbic acid as an electron donor, the dyad linked to Pt-TiO 2 via a phosphonate or carboxylate attachment shows excellent light-driven H 2 production with substantial longevity, in which one particular dyad [4(bpyP)] exhibits the highest activity, generating ∼40,000 turnover numbers of H 2 over 12 d (with respect to dye).photochemistry | solar energy conversion | hydrogen | spectroscopy | synthesis W ater splitting into hydrogen and oxygen is the key energystoring reaction of artificial photosynthesis (AP) and one of the most promising long-term strategies for carbon-free energy on a potentially global scale (1). As a redox reaction, water splitting has been studied primarily in terms of its two halfreactions, the reduction of aqueous protons to H 2 and the oxidation of water to O 2 (2-13). Whereas some of these studies date back more than 30 y (14-22), recent progress on each halfreaction has been notable, particularly with regard to catalyst development and mechanistic understanding of each transformation (6,(23)(24)(25)(26)(27)(28)(29). In this paper, we focus on efforts dealing with the lightdriven generation of H 2 , which in its simplest form requires a light absorber or photosensitizer (PS) for electron-hole creation, a means or pathway for charge separation and electron transfer, an aqueous proton source, a catalyst for collecting electrons and protons and promoting their conversion to H 2 , and an ultimate source of electrons in the form of an electron donor.Dating from the earliest work on the light-driven generation of H 2 , the photosensitizer has most often been a Ru(II) complex with 2,2′-bipyridine (bpy) and/or related heterocyclic ligands having a long-lived triplet metal-to-ligand ...

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Cobalt complexes as artificial hydrogenases for the reductive side of water splitting

Cited by 181 publications

References 102 publications

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

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

Earth-abundant hydrogen evolution electrocatalysts

Light-driven generation of hydrogen: New chromophore dyads for increased activity based on Bodipy dye and Pt(diimine)(dithiolate) complexes

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