Version française
Institutes/ Institute of life sciences research and technologies (iRTSV)/ Unités / Chimie et Biologie des Métaux (CBM)/ Biocatalysis/ Hydrogenases modelisation

Hydrogenases modelisation



Project leader
 
Dr. Vincent Artero
CEA research scientist
iRTSV/LCBM
CEA Grenoble
17 rue des martyrs
38 054 Grenoble cedex 09
Phone: (33) 4 38 78 91 06
Fax: (33) 4 38 78 91 24

Biography
 
Hydrogen Economy
 
Molecular hydrogen is widely considered as a convenient energy vector. Its combustion in a fuel-cell generates electricity with high yield and without any pollutant exhaust, water being the sole reaction product. However although hydrogen is one of the most abundant elements on the Earth, molecular hydrogen exists only as traces in the atmosphere and should thus be produced through processes that require an energy input.

In the perspective of a hydrogen economy, one major issue concerns the availability of economically viable methods for production of H2 from renewable sources.
Reduction of protons is apparently a very simple reaction but in fact requires multi-step catalysis. As a consequence, except on platinum metal electrodes, this reaction does not proceed at appreciable rates which is at the origin of overvoltages and significantly lowers the energetic yield of devices. In the long term replacement of platinum with inexpensive materials is critical to large-scale utilisation of hydrogen as a clean energy vector. An alternative to the use of platinum-loaded carbon as electrode material for this reaction is the combination of a common electrode material with a coordination complex able to catalyse the reaction at a reasonable potential, ie lower the overvoltage.
Another great challenge would consist in exploiting solar energy, mimicking in a way photosynthesis in plants, for the production of fuels such as hydrogen.

This research project is part of the BioHydrogen program of the CEA.
 
Hydrogenases and Biocatalysis
 

Nature widely utilises first-row transition metals in enzymes to catalyse difficult chemistry under ambient conditions. To date, no molecular system but hydrogenases proved to be effective catalysts for proton reduction or hydrogen oxidation.

H2 2H+ + 2e-

These enzymes are divided into two classes depending on the metal content at the active site. The structures of both classes have been recently published by Juan Fontecilla-Camps [Fontecilla-Camps et al., Chem. Rev., 2007]. They have catalytic dinuclear metal centers (Figure 1) in which either one nickel and one iron or two iron atoms are connected through two thiolate bridges. The bridging thiolates have different origins in the two enzymes. In NiFe-hydrogenases, they are provided by two cysteine residues, so that Ni is coordinated by four cysteinates in a non-regular configuration. In FeFe-hydrogenases the bridge is made from a small organic dithiolate ligand. X-ray crystallography and FTIR spectroscopy have clearly shown that the two kinds of hydrogenase are characterized by active sites that contain cyanide (CN-) and carbon monoxide (CO) molecules as ligands of the iron centers. Besides the curiosity for the presence of such toxic molecules as constituents of a native enzyme, these units make hydrogenases some of the extremely rare examples of organometallic centers in biology. In the case of the FeFe-hydrogenase active site the bridging dithiomethylamine ligand plays a very critical function as it participates in proton exchange, facilitating proton reduction to H2 or proton uptake from H2. The proton-exchange site in NiFe-hydrogenases is less clear, but is likely to reside on the terminal Ni-bound cysteinate residues. Finally, what the three-dimensional structures have also revealed is the presence of an array of iron-sulfur clusters (Figure 1), distant from each other by less than 15 Å, allowing an electrical communication between the active site and the protein surface where redox partners are expected to bind for accepting (H2 oxidation) or providing (H2 formation) electrons. At this surface, a so-called distal cluster is exposed to solvent and plays a crucial role in connecting the hydrogenase to its redox partners.



Figure 1: X-ray structure of the NiFe hydrogenase of the oxidised unready form of Desulfibrio fructosovorans (resolution: 1.83 Å, PDB code 1YQW). The iron atoms are depicted in purple, the nickel atom, in green, the sulfur atoms in yellow, the carbon atoms of the diatomic ligands in grey, the nitrogen atoms of cyanide ions in blue and the oxygen atom of the carbonyl and peroxo ligand in red.

A remarkable property of these enzymes, in pure isolated form, is that they can function when adsorbed on a carbon electrode surface as excellent electrocatalysts for H2 oxidation or H+ reduction without any overvoltage (the extra energy required for the reaction over that defined by the standard potential of the redox H+/H2 couple; in other words, the difference between the potential that needs to be applied to the system to allow it to function and the standard potential of the redox H+/H2 couple) and at very high rates (one molecule of hydrogenase produces 1500 to 9000 molecules of H2 per second at pH 7 and 37°C in water), thus rivalling Pt performances.
 
Chemical mimicks
 
Based on structural information of the enzyme metal centers, the synthetic analogue strategy, as defined by Holm [Ibers JA and Holm RH, Science, 1980], allows defining the minimal structure required for a catalyst to achieve the biological function. The aim is both to better understand at the molecular level the catalytic mechanism of native hydrogenases and to develop new electrocatalysts to be used in fuel-cells for hydrogen uptake or in electrolytic/photosynthetic cells for hydrogen production. Significant synthetic achievements were achieved and the new biomimics of FeFe and NiFe hydrogenases show proton reduction activity: In our group, we focus on NiFe hydrogenase modelisation. We initially reported on the catalytic activity of a series of bio-inspired dinuclear nickel-ruthenium complexes in which various electron-rich organometallic ruthenium moieties were introduced as subrogates for the {Fe(CO)(CN)2} fragment. DFT calculations were carried out out on these systems in collaboration with Martin Field of the Dynamics and kinetics of molecular processes Group (IBS) and, coupled with electrochemical measurements, allowed a heterolytic mechanism for H2 evolution to be proposed. A bridging hydride derivative was identified as the active intermediate, with a structure similar to that of the Ni-C active state of NiFe hydrogenases (Figure 2). Recently, we prepared noble-metal free nickel-manganese and nickel-iron model compounds that also proved active for hydrogen evolution in non-aqueous solvents.



Figure 2: Top: Cristallographic structure of the active site of NiFe hydrogenase and the model complex [Ni(xbsms)FeCp(CO)]-. Bottom: Structure of the catalytically competent Ni-C state of NiFe hydrogenase and DFT-calculated structure of the key intermediate in heterolytic H2 evolution catalyzed by a Ni-Ru model compound.
A purely structural approach may not be the most adequate one for the elaboration of highly active catalysts. It could be worth taking the problem from another angle, starting from an active or potentially active non-biomimetic system (different ligands, different metals) and introducing new structural or electronic properties inspired from the structure of the active sites of the enzymes.
 
   
Figure 3: [Co(dmgBF2)2L2] (L=H2O, CH3CN and has been omitted for clarity, left) [Co(DO)(DOH)pn Br2] (bromide ligands have been omitted for clarity, right)

Cobaloxime is a class of such catalysts. We have reported on the activity of various cobaloximes as electrocatalysts for the reduction of protons in organic solvents and demonstrated that the active species is a CoIII-hydride formed by protonation of the CoI complex. The water-soluble {BF2}-bridged cobaloxime [Co(dmgBF2)2L] (L = CH3CN or DMF) (figure 3) which is quite stable under acidic conditions was shown to be one of the most efficient catalysts for hydrogen evolution in non-aqueous solvent in term of potential and turnover frequency. We recently discovered that diimine-dioxime complexes of cobalt (Figure 3, right) catalyze hydrogen evolution with similar performances. These new catalysts contain a tetradentate ligand that makes them significantly more stable against hydrolysis. In addition, the diimine-dioxime ligand has an open oxime bridge susceptible to proton exchange, which provides the catalyst with a mechanism to adjust its electrocatalytic potential for hydrogen evolution to the acido-basic conditions of the solution and keeps the overvoltage for the reduction of acids within reasonable values over a wide range of pKas. The importance of a basic site in the second coordination sphere of the catalytic metal center has been highlighted above in the case of hydrogenases. This example thus nicely demonstrates that increased understanding of the chemical principles on which the reactivity of a biological active site and fine utilization of the synthetic power of chemistry allow minor modifications of a bioinspired catalyst resulting in considerable functional improvements.
Cobaloxime-Based Photocatalytic Devices for Hydrogen Production
 

In collaboration with Dr Murielle Chavarot-Kerlidou.
 
Grafting Catalysts for Hydrogen production/Uptake on nanostructured electrodes
 
Incorporating the new synthetic catalysts in devices for hydrogen production/uptake is the final goal of this project. As stated in the introduction, the covalent grafting onto an electrode material such as carbon or the incorporation of catalyst into a polymer coating an electrode would lead to new electrocatalytic materials for hydrogen production or uptake. We have developed an original strategy, combining the above biomimetic molecular approach with nanochemical tools and shown that the covalent attachment of a nickel-bisdiphosphine mimic of the active site of hydrogenase enzymes on carbon nanotubes results in a nickel-based cathode nanomaterial with remarkable performances under the strongly acidic conditions required in the expanding proton exchange membrane (PEM) technology. This material incorporated in a membrane-electrode assembly indeed evolves H2 from aqueous sulphuric acid solution without overvoltage and proves exceptionally stable (> 100,000 turnovers). This Pt-free catalyst is also very efficient for hydrogen oxidation under the same conditions with current densities similar to those observed for hydrogenase-based materials. In addition the catalytic activity for H2 uptake displayed by this novel molecular engineered electrocatalytic material is sustained in the presence of carbon monoxide (CO), a major impurity in H2 fuels derived from reformed hydrocarbons or biomass. This constitutes a major breakthrough for Nafion-based PEM fuel cells technology since CO poisoning limits the commercialization of devices based on Pt electrocatalysts. We also recently developed a straightforward and highly convenient preparation of these new electrocatalytic materials compatible with standard deposition/printing of an ink containing the electro-active material with tunable catalyst loading.

This research project has been initiated through the NanoSciences transversal program of the CEA and was carried out in collaboration with the Laboratory of Chemistry of Surfaces and Interfaces (Serge Palacin and Bruno Jousselme, Matter Science Division of the CEA, IRAMIS, SPCSI) and the Laboratory for Innovation in Energetic Technologies and Nanomaterials (Nicolas Guillet and Nicolas Bardi, LITEN/DTH/LCPEM).
 
Artificial enzymes
 
Hydrogen production catalyzed by bio-inspired catalysts is still associated with high overvoltages so that optimization need to be achieved. For that, it is crucial to better understand how the interactions with peptidic residues stabilize and beyond control the reactivity and catalytic activity of soft organometallic centers in aqueous solutions. In this perspective, a bio-synthetic approach, i.e using peptides or proteins as coordinates instead of synthetic ligands, is very attractive but remains to be investigated regarding the design of artificial hydrogenases.

In a first study, in collaboration with Christine Cavazza (IBS), we have investigated the reactivity of a variety of water-soluble iron, ruthenium and manganese carbonyl complexes towards lysozyme. This protein was selected on the basis of its reported ability to incorporate a {Ru(Ρ-cymene)}2+ center [McNae IW et al., Chem. Comm., 2004]. In most cases however, binding to lysozyme was not specific and no defined adduct could be isolated but we could purify and characterize, at the spectroscopic and structural level, a {Mn(CO)3}+ derivative of lysozyme. Furthermore, we have found that this compound is able to transfer the {Mn(CO)3}+ group to a nickel complex, thus forming a structural mimic of [NiFe] hydrogenases active site similar to the functional nickel-ruthenium electrocatalyst described above.



Figure 4: Structure of the covalent adduct [lysozyme-{MnI(CO)3}] and recativity with the nickel complex [Ni(xbsms)].
 
Publications
 
2012 
    Zhang P, Jacques PA, Chavarot-Kerlidou M, Wang M, Sun L, Fontecave M and Artero V
Phosphine coordination to a cobalt diimine-dioxime catalyst increases stability during light-driven H2 Production.
Inorganic Chemistry, 2012, 51(4): 2115-2120
2011 
  Andreiadis ES, Chavarot-Kerlidou M, Fontecave M and Artero V
Artificial photosynthesis: From molecular catalysts for light-driven water splitting to photoelectrochemical cells.
Photochemistry and Photobiology, 2011, 87: 946–964
This article was the cover of this journal.
 
    Artero V, Canaguier S and Fontecave M
Cp*--ruthenium-nickel-based H2-evolving electrocatalysts as bio-inspired models of NiFe hydrogenases.
European Journal of Inorganic Chemistry, 2011, 2011(7): 1094-1099
 
  Artero V, Chavarot-Kerlidou M and Fontecave M
Splitting water with cobalt.
Angewandte Chemie International Edition, 2011, 50(32): 7238-7266
    Artero V and Fontecave M
Light-driven bioinspired water splitting: Recent developments in photoelectrode materials.
Comptes Rendus Chimie, 2011, 14(9): 799-810

Canaguier S, Fontecave M and Artero V
Cp*--ruthenium-nickel-based H2-evolving electrocatalysts as bio-inspired models of NiFe hydrogenases.
European Journal of Inorganic Chemistry, 2011, 7: 1094-1099

Fontecave M and Artero V
Bioinspired catalysis at the crossroads between biology and chemistry: A remarkable example of an electrocatalytic material mimicking hydrogenases.
Comptes Rendus de Chimie, 2011, 14(4): 362-371

Fourmond V, Canaguier S, Golly B, Field MJ, Fontecave M and Artero V
A nickel–manganese catalyst as a biomimic of the active site of NiFe hydrogenases: A combined electrocatalytical and DFT mechanistic study.
Energy & Environmental Science, 2011, 4: 2417-2427

Hijazi A, Kemmegne-Mbouguen JC, Floquet S*, Marrot J, Mayer C, Artero V and Cadot E
Capture of the complex [Ni(dto)2]2- (dto2- = dithiooxalato ligand) in a Mo12-ring: Synthesis, characterizations and application toward the reduction of protons.
Inorganic Chemistry, 2011, 50(18): 9031-9038

Tran PD, Le Goff A, Heidkamp J, Jousselme B, Guillet N, Palacin S, Dau H, Fontecave M and Artero V
Noncovalent modification of carbon nanotubes with pyrene-functionalized nickel complexes: Carbon monoxide tolerant catalysts for hydrogen evolution and uptake.
Angewandte Chemie International Edition, 2011, 50(6): 1371-1374

2010 
    Canaguier S, Field M, Oudart Y, Pecaut J, Fontecave M and Artero V
A structural and functional mimic of the active site of NiFe hydrogenases.
Chemical Communications, 2010, 46(32): 5876-5878

Fourmond V, Jacques PA, Fontecave M and Artero V
H2 evolution and molecular electrocatalysts: Determination of overpotentials and effect of homoconjugation.
Inorganic Chemistry, 2010, 49: 10338–10347

Le Goff A, Artero V, Metayé R, Moggia F, Jousselme B, Razavet M, Tran PD, Palacin S and Fontecave M
Immobilization of FeFe hydrogenase mimics onto carbon and gold electrodes by controlled aryldiazonium salt reduction: an electrochemical, XPS and ATR-IR study.
International Journal of Hydrogen Energy, 2010, 35(19): 10790-10796

Le Goff A, Moggia F, Debou N, Jegou P, Artero V, Fontecave M, Jousselme B and Palacin S
Facile and tunable functionalization of carbon nanotube electrodes with ferrocene by covalent coupling and [pi]-stacking interactions and their relevance to glucose bio-sensing.
Journal of Electroanalytical Chemistry, 2010, 641(1-2): 57-63

Tran PD, Artero V and Fontecave M
Water electrolysis and photoelectrolysis on electrodes engineered using biological and bio-inspired molecular systems.
Energy and Environmental Science, 2010, 3(6): 727-747

Vaccaro L, Artero V, Canaguier S, Fontecave M and Field MJ
Mechanism of hydrogen evolution catalyzed by NiFe hydrogenases: Insights from a Ni-Ru model compound.
Dalton Transactions, 2010, 39(12): 3043-3049

2009 
    Canaguier S, Vaccaro L, Artero V, Ostermann R, Pecaut J, Field MJ and Fontecave M
Cyclopentadienyl ruthenium-nickel catalysts for biomimetic hydrogen evolution: Electrocatalytic properties and mechanistic DFT studies.
Chemistry A European Journal, 2009, 15(37): 9350-9364

Jacques PA, Artero V, Pécaut J and Fontecave M
Cobalt and nickel diimine-dioxime complexes as molecular electrocatalysts for hydrogen evolution with low overvoltages.
Proceedings of the National Academy of Sciences USA, 2009, 106(49): 20627–20632

Le Goff A, Artero V, Jousselme B, Dinh Tran P, Guillet N, Métayé R, Fihri A, Palacin S and Fontecave M
From hydrogenases to noble metal-free catalytic nanomaterials for H2 production and uptake.
Science, 2009, 326(5958): 1384-1387

Oudart Y, Artero V, Norel L, Train C, Pécaut J and Fontecave M
Synthesis, crystal structure, magnetic properties and reactivity of a Ni-Ru model of NiFe hydrogenases with a pentacoordinated triplet (S = 1) NiII center.
Journal of Organometallic Chemistry, 2009, 694(17): 2866-2869

2008 
   

Artero V and Fontecave M
Hydrogen evolution catalyzed by {CpFe(CO)2}-based complexes.
Comptes Rendus Chimie, 2008, 11(8): 926-931

Canaguier S, Artero V and Fontecave M
Modelling NiFe hydrogenases: Nickel-based electrocatalysts for hydrogen evolution.
Dalton Transactions, 2008, 315-325

Fihri A, Artero V, Pereira A and Fontecave M
Efficient H2-producing photocatalytic systems based on cyclometalated iridium- and tricarbonylrhenium-diimine photosensitizers and cobaloxime catalysts.
Dalton Transactions, 2008, (41): 5567-5569

Fihri A, Artero V, Razavet M, Baffert C, Leibl W and Fontecave M
Cobaloxime-based photocatalytic devices for hydrogen production.
Angewandte Chemie International Edition, 2008, 47(3): 564-567

2007 
    Baffert C, Artero V and Fontecave M
Cobaloximes as functional models for hydrogenases. 2. Proton electroreduction catalyzed by difluoroborylbis(dimethylglyoximato)cobalt(II) complexes in organic media.
Inorganic Chemistry, 2007, 46: 1817-1824
 

Oudart Y, Artero V, Pécaut J, Lebrun C and Fontecave M
Dinuclear nickel-ruthenium complexes as functional bio-inspired models of [NiFe] hydrogenases.
European Journal of Inorganic Chemistry, 2007, 18: 2613-2626
This article made the cover of a special edition of European Journal of Inorganic Chemistry, « celebrating 10 years of excellence »
    Razavet M, Artero V, Cavazza C, Oudart Y, Lebrun C, Fontecilla-Camps JC and Fontecave M
Tricarbonylmanganese(I)-lysosyme complex: A structurally characterized organometallic protein.
Chemical Communications, 2007, 2007(27): 2805-2807

2006 
    Oudart Y, Artero V, Pecaut J and Fontecave M
[Ni(xbsms)Ru(CO)2Cl2]: A bioinspired nickel-ruthenium functional model of [NiFe] hydrogenase.
Inorganic Chemistry, 2006, 45(11): 4334-4336

2005 
    Artero V and Fontecave M
Some general principles for designing electrocatalysts with hydrogenase activity.
Coordination Chemistry Review, 2005, 249(15-16): 1518-1535

Razavet M, Artero V and Fontecave M
Proton electro-reduction catalyzed by cobaloximes: Functional models for hydrogenases
Inorganic Chemistry, 2005, 44(13): 4786-4795
 
PhD theses
 
Sigolène Canaguier.
Modelling the active site of NiFe hydrogenases: new catalysts for the electro-production of H2 and mechanistic studies. (24 septembre 2009, Université Joseph Fourier)
[Abstract] - [Thesis on line]

Yohan Oudart.
Modèles structuraux et fonctionnel du site actif des hydrogénases [NiFe] : de nouveaux catalyseurs bio-inspirés pour la production d'hydrogène. (28 septembre 2006, Université Joseph Fourier)
[Abstract] - [Thesis on line]