Publications by authors named "Vincent Artero"

91 Publications

Artificial maturation of [FeFe] hydrogenase in a redox polymer film.

Chem Commun (Camb) 2021 Feb;57(14):1750-1753

CNRS, Aix-Marseille Université, Laboratoire de Bioénergétique et Ingénierie des Protéines, Marseille, France.

We demonstrate that the insertion of the dinuclear active site of [FeFe] hydrogenase into the apo-enzyme can occur when the enzyme is embedded in a film of redox polymer, under conditions of mediated electron transfer. The maturation can be monitored by electrochemistry, and is as fast as under conditions of direct electron transfer. This new approach further clears the way to the implementation of hydrogenases in large scale real life processes.
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http://dx.doi.org/10.1039/d0cc08168jDOI Listing
February 2021

Revisiting amorphous molybdenum sulfide's activity for the electro-driven reduction of dinitrogen and N-containing substrates.

Chem Commun (Camb) 2020 Nov 21;56(90):13975-13978. Epub 2020 Oct 21.

Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, Grenoble 38000, France.

Ammonia (NH) is a major feedstock of the chemical industry. The imperious need to decarbonize its production has stimulated a quest for efficient catalysts able to drive the direct electro-reduction of dinitrogen (N) into NH. A large number of materials have now been proposed for this reaction, including bioinspired molybdenum sulfide derivatives. Here, we revisit the potential of amorphous molybdenum sulfide to drive the electrocatalytic reduction of N and other substrates of nitrogenase. We find that this material exhibits negligible activity towards N but achieves efficient reduction of inorganic azides.
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http://dx.doi.org/10.1039/d0cc05078dDOI Listing
November 2020

Hydrogen evolution reaction mediated by an all-sulfur trinuclear nickel complex.

Chem Commun (Camb) 2020 Sep 19;56(75):11106-11109. Epub 2020 Aug 19.

Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.

We report the synthesis and the characterization of a trinuclear nickel complex. Solid state and solution studies using X-ray diffraction, NMR and UV-vis spectroscopy highlight the square planar geometries around the metal centers and an all-sulfur coordination sphere. It exhibits significant electrocatalytic activity for hydrogen evolution in DMF using EtNHCl as the proton source. DFT studies suggest that sulfur atoms act as proton relay, as proposed in [NiFe] hydrogenases.
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http://dx.doi.org/10.1039/d0cc04174bDOI Listing
September 2020

Noncovalent Integration of a Bioinspired Ni Catalyst to Graphene Acid for Reversible Electrocatalytic Hydrogen Oxidation.

ACS Appl Mater Interfaces 2020 Feb 22;12(5):5805-5811. Epub 2020 Jan 22.

Univ. Grenoble Alpes, CEA, CNRS, IRIG, Laboratoire de Chimie et Biologie des Métaux , F-38000 Grenoble , France.

Efficient heterogeneous catalysis of hydrogen oxidation reaction (HOR) by platinum group metal (PGM)-free catalysts in proton-exchange membrane (PEM) fuel cells represents a significant challenge toward the development of a sustainable hydrogen economy. Here, we show that graphene acid (GA) can be used as an electrode scaffold for the noncovalent immobilization of a bioinspired nickel bis-diphosphine HOR catalyst. The highly functionalized structure of this material and optimization of the electrode-catalyst assembly sets new benchmark electrocatalytic performances for heterogeneous molecular HOR, with current densities above 30 mA cm at 0.4 V versus reversible hydrogen electrode in acidic aqueous conditions and at room temperature. This study also shows the great potential of GA for catalyst loading improvement and porosity management within nanostructured electrodes toward achieving high current densities with a noble-metal free molecular catalyst.
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http://dx.doi.org/10.1021/acsami.9b18922DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7009173PMC
February 2020

Electrocatalytic Hydrogen Evolution with a Cobalt Complex Bearing Pendant Proton Relays: Acid Strength and Applied Potential Govern Mechanism and Stability.

J Am Chem Soc 2020 01 19;142(1):274-282. Epub 2019 Dec 19.

Univ. Grenoble Alpes , CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, UMR 5249, 17 rue des Martyrs, 38000 Grenoble , France.

[Co(bapbpy)Cl] (: 6,6'-bis(2-aminopyridyl)-2,2'-bipyridine) is a polypyridyl cobalt(II) complex bearing both a redox-active bipyridine ligand and pendant proton relays. This compound catalyzes electro-assisted H evolution in DMF with distinct mechanisms depending on the strength of the acid used as the proton source (p values ranging from 3.4 to 13.5 in DMF) and the applied potential. Electrochemical studies combining cyclic voltammetry and bulk electrolysis measurements enabled one to bring out four distinct catalytic processes. Where applicable, relevant kinetic information were obtained using either foot-of-the-wave analysis (FOWA) or analytical treatment of bulk electrolysis experiments. Among the different catalytic pathways identified in this study, a clear relationship between the catalyst performances and stability was evidenced. These results draw attention to a number of interesting considerations and may help in the development of future adequately designed catalysts.
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http://dx.doi.org/10.1021/jacs.9b10407DOI Listing
January 2020

Tuning the Electron Storage Potential of a Charge-Photoaccumulating Ru Complex by a DFT-Guided Approach.

Chemistry 2019 Nov 30;25(61):13911-13920. Epub 2019 Sep 30.

Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, 38000, Grenoble, France.

Molecular photosensitizers that are able to store multiple reducing equivalents are of great interest in the field of solar fuel production, where most reactions involve multielectronic reduction processes. In order to increase the reducing power of a ruthenium tris-diimine charge-photoaccumulating complex, two structural modifications on its fused dipyridophenazine-pyridoquinolinone ligand were computationally investigated. Addition of an electron-donating oxime group was calculated to substantially decrease the reduction potentials of the complex, thus guiding the synthesis of a pyridoquinolinone-oxime derivative. Its spectroscopic and (spectro)electrochemical characterization experimentally confirmed the DFT predictions, with the first and second reduction processes cathodically shifted by -0.24 and -0.14 V, respectively, compared to the parent complex. Moreover, the ability of this novel artificial photosynthetic system to store two photogenerated electrons at a more reducing potential, via a proton-coupled electron-transfer mechanism, was demonstrated.
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http://dx.doi.org/10.1002/chem.201902312DOI Listing
November 2019

Earth-Abundant Molecular Z-Scheme Photoelectrochemical Cell for Overall Water-Splitting.

J Am Chem Soc 2019 06 11;141(24):9593-9602. Epub 2019 Jun 11.

Laboratoire de Chimie et Biologie des Métaux , Université Grenoble Alpes , CNRS UMR 5249, CEA, 17 rue des Martyrs , F-38054 Grenoble Cedex, France.

A push-pull organic dye and a cobaloxime catalyst were successfully cografted on NiO and CuGaO to form efficient molecular photocathodes for H production with >80% Faradaic efficiency. CuGaO is emerging as a more effective p-type semiconductor in photoelectrochemical cells and yields a photocathode with 4-fold higher photocurrent densities and 400 mV more positive onset photocurrent potential compared to the one based on NiO. Such an optimized CuGaO photocathode was combined with a TaON|CoO photoanode in a photoelectrochemical cell. Operated in this Z-scheme configuration, the two photoelectrodes produced H and O from water with 87% and 88% Faradaic efficiency, respectively, at pH 7 under visible light and in the absence of an applied bias, equating to a solar to hydrogen conversion efficiency of 5.4 × 10%. This is, to the best of our knowledge, the highest efficiency reported so far for a molecular-based noble metal-free water splitting Z-scheme.
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http://dx.doi.org/10.1021/jacs.9b02521DOI Listing
June 2019

A robust ALD-protected silicon-based hybrid photoelectrode for hydrogen evolution under aqueous conditions.

Chem Sci 2019 Apr 12;10(16):4469-4475. Epub 2019 Mar 12.

Université Grenoble Alpes , CNRS , CEA , Laboratoire de Chimie et Biologie des Métaux , 17 rue des Martyrs , 38000 Grenoble , France . Email:

Hydrogen production through direct sunlight-driven water splitting in photo-electrochemical cells (PECs) is a promising solution for energy sourcing. PECs need to fulfill three criteria: sustainability, cost-effectiveness and stability. Here we report an efficient and stable photocathode platform for H evolution based on Earth-abundant elements. A p-type silicon surface was protected by atomic layer deposition (ALD) with a 15 nm TiO layer, on top of which a 300 nm mesoporous TiO layer was spin-coated. The cobalt diimine-dioxime molecular catalyst was covalently grafted onto TiO through phosphonate anchors and an additional 0.2 nm ALD-TiO layer was applied for stabilization. This assembly catalyzes water reduction into H in phosphate buffer (pH 7) with an onset potential of +0.47 V RHE. The resulting current density is -1.3 ± 0.1 mA cm at 0 V RHE under AM 1.5 solar irradiation, corresponding to a turnover number of 260 per hour of operation and a turnover frequency of 0.071 s.
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http://dx.doi.org/10.1039/c8sc05006fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6482884PMC
April 2019

A Non-Heme Diiron Complex for (Electro)catalytic Reduction of Dioxygen: Tuning the Selectivity through Electron Delivery.

J Am Chem Soc 2019 05 7;141(20):8244-8253. Epub 2019 May 7.

Université Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble , France.

In the oxygen reduction reaction (ORR) domain, the investigation of new homogeneous catalysts is a crucial step toward the full comprehension of the key structural and/or electronic factors that control catalytic efficiency and selectivity. Herein, we report a unique non-heme diiron complex that can act as a homogeneous ORR catalyst in acetonitrile solution. This iron(II) thiolate dinuclear complex, [Fe(LS)(LSH)] ([Fe]) (LS = 2,2'-(2,2'-bipyridine-6,6'-diyl)bis(1,1-diphenylethanethiolate)) contains a thiol group in the metal coordination sphere. [Fe] is an efficient ORR catalyst both in the presence of a one-electron reducing agent and under electrochemically assisted conditions. However, its selectivity is dependent on the electron delivery pathway; in particular, the process is selective for HO production under chemical conditions (up to ∼95%), whereas HO is the main product during electrocatalysis (less than ∼10% HO). Based on computational work alongside the experimental data, a mechanistic proposal is discussed that rationalizes the selective and tunable reduction of dioxygen.
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http://dx.doi.org/10.1021/jacs.9b02011DOI Listing
May 2019

Insights into the mechanism and aging of a noble-metal free H-evolving dye-sensitized photocathode.

Chem Sci 2018 Aug 10;9(32):6721-6738. Epub 2018 Jul 10.

Laboratoire de Chimie et Biologie des Métaux , Université Grenoble Alpes , CNRS UMR 5249, CEA , 17 rue des Martyrs , F-38054 Grenoble , Cedex , France . Email: ; http://www.solhycat.com.

Dye-sensitized photo-electrochemical cells (DS-PECs) form an emerging technology for the large-scale storage of solar energy in the form of (solar) fuels because of the low cost and ease of processing of their constitutive photoelectrode materials. Preparing such molecular photocathodes requires a well-controlled co-immobilization of molecular dyes and catalysts onto transparent semiconducting materials. Here we used a series of surface analysis techniques to describe the molecular assembly of a push-pull organic dye and a cobalt diimine-dioxime catalyst co-grafted on a p-type NiO electrode substrate. (Photo)electrochemical measurements allowed characterization of electron transfer processes within such an assembly and to demonstrate for the first time that a Co species is formed as the entry into the light-driven H evolution mechanism of a dye-sensitized photocathode. This co-grafted noble-metal free H-evolving photocathode architecture displays similar performances to its covalent dye-catalyst counterpart based on the same catalytic moiety. time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of these photoelectrodes after extensive photoelectrochemical operation suggested decomposition pathways of the dye and triazole linkage used to graft the catalyst onto NiO, providing grounds for the design of optimized molecular DS-PEC components with increased robustness upon turnover.
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http://dx.doi.org/10.1039/c8sc00899jDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6115630PMC
August 2018

Hydrogen Evolution from Aqueous Solutions Mediated by a Heterogenized [NiFe]-Hydrogenase Model: Low pH Enables Catalysis through an Enzyme-Relevant Mechanism.

Angew Chem Int Ed Engl 2018 12 11;57(49):16001-16004. Epub 2018 Nov 11.

Université Grenoble Alpes, UMR CNRS 5249, CEA, Laboratoire de Chimie et Biologie des Métaux, 38000, Grenoble, France.

[NiFe]-hydrogenase enzymes are efficient catalysts for H evolution but their synthetic models have not been reported to be active under aqueous conditions so far. Here we show that a close model of the [NiFe]-hydrogenase active site can work as a very active and stable heterogeneous H evolution catalyst under mildly acidic aqueous conditions. Entry in catalysis is a Ni Fe complex, with electronic structure analogous to the Ni-L state of the enzyme, corroborating the mechanism modification recently proposed for [NiFe]-hydrogenases.
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http://dx.doi.org/10.1002/anie.201808215DOI Listing
December 2018

Electron transfer in a covalent dye-cobalt catalyst assembly - a transient absorption spectroelectrochemistry perspective.

Chem Commun (Camb) 2018 Sep 3;54(75):10594-10597. Epub 2018 Sep 3.

Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany and Department Functional Interfaces, Leibniz Institute of Photonic Technology Jena (IPHT), Albert-Einstein-Straße 9, 07745 Jena, Germany. and Center for Energy and Environmental Chemistry, Friedrich Schiller University Jena, Philosophenweg 8, 07743 Jena, Germany.

Various oxidation states of the catalytically active cobalt center in a covalent dyad were electrochemically prepared and the light-induced excited-state processes were studied. Virtually identical deactivation processes are observed, irrespective of the oxidation state of the cobalt center, varying from Co to Co, indicating the absence of oxidative quenching within the dye-catalyst assembly.
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http://dx.doi.org/10.1039/c8cc05556dDOI Listing
September 2018

A protocol for quantifying hydrogen evolution by dye-sensitized molecular photocathodes and its implementation for evaluating a new covalent architecture based on an optimized dye-catalyst dyad.

Dalton Trans 2018 Aug 30;47(31):10509-10516. Epub 2018 May 30.

Laboratoire de Chimie et Biologie des Métaux, Université Grenoble Alpes, CNRS, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 17 rue des Martyrs, Grenoble 38000, France.

A protocol that combines gas chromatography and a high-sensitivity micro Clark-type electrode is described to quantify hydrogen production across gas and solution phases for systems operating at very low currents such as dye-sensitized H-evolving photocathodes. Data indicate that a significant fraction of H remains in aqueous solution even after several hours of experiments. Using this protocol, re-evaluation of a dye-sensitized H-evolving photocathode based on a dye-catalyst dyad showed a reproducible 66% increase of the faradaic efficiency compared with previously reported headspace GC measurements [Kaeffer et al., J. Am. Chem. Soc., 2016, 138, 12308-12311]. This dyad was based on an organic push-pull dye where donor and acceptor are separated by one thiophene group. Insertion of a second thiophene group between the donor and acceptor led to a more efficient system with 30% improved faradaic efficiency for H evolution.
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http://dx.doi.org/10.1039/c8dt01210eDOI Listing
August 2018

An artificial photosynthetic system for photoaccumulation of two electrons on a fused dipyridophenazine (dppz)-pyridoquinolinone ligand.

Chem Sci 2018 May 2;9(17):4152-4159. Epub 2018 Apr 2.

Laboratoire de Chimie et Biologie des Métaux , Univ. Grenoble Alpes , CNRS , CEA , 38000 Grenoble , France . Email:

Increasing the efficiency of molecular artificial photosynthetic systems is mandatory for the construction of functional devices for solar fuel production. Decoupling the light-induced charge separation steps from the catalytic process is a promising strategy, which can be achieved thanks to the introduction of suitable electron relay units performing charge accumulation. We report here on a novel ruthenium tris-diimine complex able to temporarily store two electrons on a fused dipyridophenazine-pyridoquinolinone π-extended ligand upon visible-light irradiation in the presence of a sacrificial electron donor. Full characterization of this compound and of its singly and doubly reduced derivatives thanks to resonance Raman, EPR and (TD)DFT studies allowed us to localize the two electron-storage sites and to relate charge photoaccumulation with proton-coupled electron transfer processes.
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http://dx.doi.org/10.1039/c7sc04348aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5941200PMC
May 2018

Hydrogen Evolution Reactions Catalyzed by a Bis(thiosemicarbazone) Cobalt Complex: An Experimental and Theoretical Study.

Chemistry 2018 Jun 6;24(35):8779-8786. Epub 2018 Jun 6.

Aix Marseille Univ, CNRS, Centrale Marseille, iSm2, Marseille, France.

The synthesis and characterization of a dinuclear bis(thiosemicarbazone) cobalt complex [Co L (NCS) ] is reported. This complex exhibits significant catalytic activity for hydrogen production in DMF by using triethylammonium (Et NHBF ) as the proton source. Cyclic voltammetry data allowed a maximum turnover frequency of 130 s for 1 m proton concentration to be determined. The catalytic nature of the process and the production of dihydrogen were confirmed by gas analysis during controlled potential electrolysis experiments. Quantum chemical calculations show that the complex displays a ligand-assisted metal-centered reactivity and supports a catalytic mechanism involving ligand-based reduction and protonation steps followed by metal-centered processes.
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http://dx.doi.org/10.1002/chem.201801155DOI Listing
June 2018

Engineering an [FeFe]-Hydrogenase: Do Accessory Clusters Influence O Resistance and Catalytic Bias?

J Am Chem Soc 2018 04 17;140(16):5516-5526. Epub 2018 Apr 17.

Laboratoire de Chimie des Processus Biologiques , Collège de France, Université Pierre et Marie Curie, CNRS UMR 8229, PSL Research University , 11 place Marcelin Berthelot , 75005 Paris , France.

[FeFe]-hydrogenases, HydAs, are unique biocatalysts for proton reduction to H. However, they suffer from a number of drawbacks for biotechnological applications: size, number and diversity of metal cofactors, oxygen sensitivity. Here we show that HydA from Megasphaera elsdenii (MeHydA) displays significant resistance to O. Furthermore, we produced a shorter version of this enzyme (MeH-HydA), lacking the N-terminal domain harboring the accessory FeS clusters. As shown by detailed spectroscopic and biochemical characterization, MeH-HydA displays the following interesting properties. First, a functional active site can be assembled in MeH-HydA in vitro, providing the enzyme with excellent hydrogenase activity. Second, the resistance of MeHydA to O is conserved in MeH-HydA. Third, MeH-HydA is more biased toward proton reduction than MeHydA, as the result of the truncation changing the rate limiting steps in catalysis. This work shows that it is possible to engineer HydA to generate an active hydrogenase that combines the resistance of the most resistant HydAs and the simplicity of algal HydAs, containing only the H-cluster.
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http://dx.doi.org/10.1021/jacs.8b01689DOI Listing
April 2018

Heterogenization of a [NiFe] Hydrogenase Mimic through Simple and Efficient Encapsulation into a Mesoporous MOF.

Inorg Chem 2017 Dec 1;56(24):14801-14808. Epub 2017 Dec 1.

Département de Chimie Moléculaire, Univ. Grenoble Alpes, CNRS , 38000 Grenoble, France.

In the quest for new, efficient, and noble-metal-free H-evolution catalysts, hydrogenase enzymes are a source of inspiration. Here, we describe the development of a new hybrid material based on a structural and functional [NiFe]-hydrogenase model complex (NiFe) incorporated into the Zr-based MOF PCN-777. The bulk [email protected] material was synthesized by simple encapsulation. Characterization by solid-state NMR and IR spectroscopy, SEM-EDX, ICP-OES, and gas adsorption confirmed the inclusion of the guest. FTO-supported thin films of the [email protected] composite were obtained by electrophoretic deposition of the bulk material and characterized by SEM-EDX, ICP-OES, and cyclic voltammetry. The average surface concentration of electroactive NiFe catalyst in the film was found to be ∼9.6 × 10 mol cm, implying that a surprisingly high fraction (37%) of NiFe units incorporated in the MOF are electroactive. By cyclic voltammetry, we showed that NiFe maintains its electrocatalytic capabilities for H reduction inside the MOF cavities, even if under controlled-potential electrolysis conditions the activity of NiFe cannot be discerned from that of free PCN-777 and FTO.
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http://dx.doi.org/10.1021/acs.inorgchem.7b01824DOI Listing
December 2017

Aqueous Photocurrent Measurements Correlated to Ultrafast Electron Transfer Dynamics at Ruthenium Tris Diimine-Sensitized NiO Photocathodes.

J Phys Chem C Nanomater Interfaces 2017 Mar 20;121(11):5891-5904. Epub 2017 Feb 20.

Laboratoire de Chimie et Biologie des Métaux, UMR 5249 University Grenoble Alpes, CNRS, CEA, 17 rue des Martyrs, 38000 Grenoble, France.

Understanding the structural and electronic factors governing the efficiency of dye-sensitized NiO photocathodes is essential to optimize solar fuel production in photoelectrochemical cells (PECs). For these purpose, three different ruthenium dyes, bearing either two or four methylphosphonate anchoring groups and either a bipyridine or a dipyridophenazine ancillary ligand, were synthesized and grafted onto NiO films. These photoelectrodes were fully characterized by XPS, ToF-SIMS, UV-vis absorption, time-resolved emission and femtosecond transient absorption spectroscopies. Increasing the number of anchoring groups from two to four proved beneficial for the grafting efficiency. No significant modification of the electronic properties compared to the parent photosensitizer was observed, in accordance with the non-conjugated nature of the grafted linker. The photoelectrochemical activity of the dye-sensitized NiO electrodes was assessed in fully aqueous medium in the presence of an irreversible electron acceptor and photocurrents reaching 190 μA.cm were recorded. The transient absorption study revealed the presence of two charge recombination pathways for each of the sensitizers and evidenced a stabilized charge separated state in the dppz derivative, supporting its superior photoelectrochemical activity.
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http://dx.doi.org/10.1021/acs.jpcc.6b12536DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493983PMC
March 2017

Proton reduction reaction catalyzed by homoleptic nickel bis-1,2-dithiolate complexes: Experimental and theoretical mechanistic investigations.

ChemCatChem 2017 Jun 21;9(12):2308-2317. Epub 2017 Apr 21.

Inorganic Chemistry Laboratory, Chemistry Department, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou 157 71, Greece.

A series of homoleptic monoanionic nickel dithiolene complexes [Ni(bdt)](NBu), [Ni(tdt)](NBu), and [Ni(mnt)](NBu) containing the ligands benzene-1,2-dithiolate (bdt), toluene-3,4-dithiolate (tdt) and maleonitriledithiolate (mnt), respectively, have been employed as electrocatalysts in the hydrogen evolution reaction with trifluoroacetic acid as proton source in acetonitrile. All complexes were active catalysts with TONs reaching 113, 158 and 6 for [Ni(bdt)](NBu), [Ni(tdt)](NBu), and [Ni(mnt)](NBu), respectively. Faradaic yield for hydrogen evolution reaction reaches 88 % for , which also displays the minimal overpotential requirement value (467 mV) within the series. Two pathways for H evolution can be hypothesized that differ on on the sequence of protonation and reduction steps. DFT calculations are in agreement with experimental data and indicate that protonation at sulfur follows reduction to the dianion. Hydrogen evolves from the direduced-diprotonated form via a highly distorted nickel hydride intermediate. The effects of acid strength and concentration in the hydrogen-evolving mechanism are also discussed.
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http://dx.doi.org/10.1002/cctc.201601399DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5490785PMC
June 2017

Structural and functional characterization of the hydrogenase-maturation HydF protein.

Nat Chem Biol 2017 Jul 29;13(7):779-784. Epub 2017 May 29.

Laboratoire de Chimie des Processus Biologiques, Collège de France, Université Pierre et Marie Curie, CNRS UMR 8229, Paris, France.

[FeFe] hydrogenase (HydA) catalyzes interconversion between 2H and H at an active site composed of a [4Fe-4S] cluster linked to a 2Fe subcluster that harbors CO, CN and azapropanedithiolate (adt) ligands. HydE, HydG and HydF are the maturases specifically involved in the biosynthesis of the 2Fe subcluster. Using ligands synthesized by HydE and HydG, HydF assembles a di-iron precursor of the 2Fe subcluster and transfers it to HydA for maturation. Here we report the first X-ray structure of HydF with its [4Fe-4S] cluster. The cluster is chelated by three cysteines and an exchangeable glutamate, which allows the binding of synthetic mimics of the 2Fe subcluster. [Fe(adt)(CO)(CN)] is proposed to be the true di-iron precursor because, when bound to HydF, it matures HydA and displays features in Fourier transform infrared (FTIR) spectra that are similar to those of the native HydF active intermediate. A new route toward the generation of artificial hydrogenases, as combinations of HydF and such biomimetic complexes, is proposed on the basis of the observed hydrogenase activity of chemically modified HydF.
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http://dx.doi.org/10.1038/nchembio.2385DOI Listing
July 2017

Porous dendritic copper: an electrocatalyst for highly selective CO reduction to formate in water/ionic liquid electrolyte.

Chem Sci 2017 Jan 20;8(1):742-747. Epub 2016 Sep 20.

Laboratoire de Chimie des Processus Biologiques , CNRS UMR 8229 , Collège de France , Université Pierre et Marie Curie , 11 Place Marcelin Berthelot , 75231 Paris Cedex 05 , France . Email: ; Tel: +33 0144271372.

Copper is currently extensively studied because it provides promising electrodes for carbon dioxide electroreduction. The original combination, reported here, of a nanostructured porous dendritic Cu-based material, characterized by electron microcopy (SEM, TEM) and X-ray diffraction methods, and a water/ionic liquid mixture as the solvent, contributing to CO solubilization and activation, results in a remarkably efficient (large current densities at low overpotentials), stable and selective (large faradic yields) electrocatalytic system for the conversion of CO into formic acid, a product with a variety of uses. These results provide new directions for the further improvement of Cu electrodes.
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http://dx.doi.org/10.1039/c6sc03194cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5299793PMC
January 2017

CuAAC-based assembly and characterization of a ruthenium-copper dyad containing a diimine-dioxime ligand framework.

Faraday Discuss 2017 06;198:251-261

Laboratoire de Chimie et Biologie des Métaux, Univ. Grenoble Alpes, CNRS UMR 5249, CEA, 17 rue des martyrs, F-38054, Grenoble Cedex 9, France.

The design of molecular dyads combining a light-harvesting unit with an electroactive centre is highly demanded in the field of artificial photosynthesis. The versatile Copper-catalyzed Azide-Alkyne Cycloaddition (CuAAC) procedure was employed to assemble a ruthenium tris-diimine unit to an unprecedented azide-substituted copper diimine-dioxime moiety. The resulting RuCu dyad 4 was characterized by electrochemistry, H NMR, EPR, UV-visible absorption, steady-state fluorescence and transient absorption spectroscopies. Photoinduced electron transfer from the ruthenium to the copper centre upon light-activation in the presence of a sacrificial electron donor was established thanks to EPR-monitored photolysis experiments, opening interesting perspectives for photocatalytic applications.
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http://dx.doi.org/10.1039/c6fd00204hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493982PMC
June 2017

Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid.

J Am Chem Soc 2017 03 3;139(10):3685-3696. Epub 2017 Mar 3.

Laboratoire de Chimie et Biologie des Métaux, Université Grenoble Alpes , CEA, CNRS, 17 rue des Martyrs, 38000 Grenoble, France.

We report here on a new series of CO-reducing molecular catalysts based on Earth-abundant elements that are very selective for the production of formic acid in dimethylformamide (DMF)/water mixtures (Faradaic efficiency of 90 ± 10%) at moderate overpotentials (500-700 mV in DMF measured at the middle of the catalytic wave). The [CpCo(PN)I] compounds contain diphosphine ligands, PN, with two pendant amine residues that act as proton relays during CO-reduction catalysis and tune their activity. Four different PN ligands with cyclohexyl or phenyl substituents on phosphorus and benzyl or phenyl substituents on nitrogen were employed, and the compound with the most electron-donating phosphine ligand and the most basic amine functions performs best among the series, with turnover frequency >1000 s. State-of-the-art benchmarking of catalytic performances ranks this new class of cobalt-based complexes among the most promising CO-to-formic acid reducing catalysts developed to date; addressing the stability issues would allow further improvement. Mechanistic studies and density functional theory simulations confirmed the role of amine groups for stabilizing key intermediates through hydrogen bonding with water molecules during hydride transfer from the Co center to the CO molecule.
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http://dx.doi.org/10.1021/jacs.6b11474DOI Listing
March 2017

Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cells.

Angew Chem Int Ed Engl 2017 02 12;56(7):1845-1849. Epub 2017 Jan 12.

Univ. Grenoble Alpes, CNRS, DCM UMR 5250, 38000, Grenoble, France.

A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H /2 H interconversion from pH 0 to 9, with catalytic preference for H oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm , only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm , a new efficiency record for a hydrogen biofuel cell with base metal catalysts.
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http://dx.doi.org/10.1002/anie.201611532DOI Listing
February 2017

Nickel-centred proton reduction catalysis in a model of [NiFe] hydrogenase.

Nat Chem 2016 11 18;8(11):1054-1060. Epub 2016 Jul 18.

Univ. Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France.

Hydrogen production through water splitting is one of the most promising solutions for the storage of renewable energy. [NiFe] hydrogenases are organometallic enzymes containing nickel and iron centres that catalyse hydrogen evolution with performances that rival those of platinum. These enzymes provide inspiration for the design of new molecular catalysts that do not require precious metals. However, all heterodinuclear NiFe models reported so far do not reproduce the Ni-centred reactivity found at the active site of [NiFe] hydrogenases. Here, we report a structural and functional NiFe mimic that displays reactivity at the Ni site. This is shown by the detection of two catalytic intermediates that reproduce structural and electronic features of the Ni-L and Ni-R states of the enzyme during catalytic turnover. Under electrocatalytic conditions, this mimic displays high rates for H evolution (second-order rate constant of 2.5 × 10 M s; turnover frequency of 250 s at 10 mM H concentration) from mildly acidic solutions.
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http://dx.doi.org/10.1038/nchem.2575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493981PMC
November 2016

Molecular engineered nanomaterials for catalytic hydrogen evolution and oxidation.

Chem Commun (Camb) 2016 Nov;52(95):13728-13748

Laboratoire de Chimie et Biologie des Métaux, Université Grenoble Alpes, CNRS UMR 5249, Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), 17 rue des Martyrs, Grenoble 38000, France.

The active sites of hydrogenases have inspired the design of molecular catalysts for hydrogen evolution and oxidation. In this feature article, we showcase key elements of bio-inspiration before embarking on a tour of a representative series of molecular hydrogen evolving catalysts (HECs) and describing the toolbox available for benchmarking their performances. We then show how such catalysts can be immobilized on conducting substrates to prepare electrode materials active for hydrogen evolution and oxidation with a special emphasis on cobalt diimine-dioxime complexes and DuBois' nickel diphosphine compounds. We finally discuss the optimization required for implementing molecular-engineered materials into operational devices and illustrate how such molecular approaches can be expanded to other fuel-forming processes such as the electrochemical valorisation of carbon dioxide and the oxygen reduction or water oxidation reactions.
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http://dx.doi.org/10.1039/c6cc06311jDOI Listing
November 2016

Supramolecular assembly of cobaloxime on nanoring-coated carbon nanotubes: addressing the stability of the pyridine-cobalt linkage under hydrogen evolution turnover conditions.

Chem Commun (Camb) 2016 Sep;52(79):11783-11786

Laboratoire de Chimie et Biologie des Métaux, Université Grenoble Alpes, CNRS, CEA, 17 rue des Martyrs, F-38000 Grenoble, France.

A carbon nanotube-cobaloxime nanohybrid was prepared through supramolecular assembly of tailored polymerizable amphiphiles, leading to the coordination of cobalt on pyridine-coated nanotubes. This material was used as a catalyst for hydrogen evolution in fully aqueous media. This study provides a definitive asset regarding the stability of the pyridine-cobalt axial bond under H evolution turnover conditions.
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http://dx.doi.org/10.1039/c6cc06059eDOI Listing
September 2016
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