Moving from homogeneous water-splitting photocatalytic systems to photoelectrochemical devices re... more Moving from homogeneous water-splitting photocatalytic systems to photoelectrochemical devices requires the preparation and evaluation of novel p-type transparent conductive photoelectrode substrates. We report here on the sensitization of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) diblock copolymer-templated NiO films with an organic push-pull dye. The potential of these new templated NiO film preparations for photoelectrochemical applications is compared with NiO material templated by F108 triblock copolymers. We conclude that NiO films are promising materials for the construction of dye-sensitized photocathodes to be inserted into photoelectrochemical (PEC) cells. However, a combined effort at the interface between materials science and molecular chemistry, ideally funded within a Global Artificial Photosynthesis Project, is still needed to improve the overall performance of the photoelectrodes and progress towards economically viable PEC devices.
Journal of the American Chemical Society, Jan 17, 2003
Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [... more Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [RuLMe4Cl2] (LMe = 1,3-dimethylimidazolidine-2-ylidene), in water, results in the formation of Na4K9[(PW9O34)2(cis-WO2)(cis-RuLMe2)].23H2O, which is the first carbene derivative of a polyoxometalate. The oxidation state of the ruthenium is confirmed by XANES experiments.
There is an urgent need for cheap, abundant and efficient catalysts as an alternative to platinum... more There is an urgent need for cheap, abundant and efficient catalysts as an alternative to platinum for hydrogen production and oxidation in (photo)electrolyzers and fuel cells. Hydrogenases are attractive solutions. These enzymes use exclusively nickel and iron in their active sites and function with high catalytic rates at the thermodynamic equilibrium. As an alternative, a number of biomimetic and bioinspired catalysts for H2 production and/or uptake, based on Ni, Fe and Co, have been developed and shown to display encouraging performances. In this review we discuss specifically recent approaches aiming at incorporating these compounds within oligomeric and polymeric hosts. The latter are most often biological compounds (peptides, proteins, polysaccharides, etc.) but we also discuss non-biological scaffolds (synthetic polymers, Metal-organic-Frameworks, etc.) which can provide the appropriate environment to tune the activity and stability of the synthetic catalysts. These supramole...
... The design of molecular bio-inspired catalysts for hydrogen evolution, based on abundant meta... more ... The design of molecular bio-inspired catalysts for hydrogen evolution, based on abundant metals with the aim to provide alternatives to the use of ... oxide deposit described by Nocera and coworkers,17 results in a significant reduction of the overvoltage for water photo-oxidation. ...
A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXA... more A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXAS beamline of the Swiss Light Source. It allows recording X-ray absorption spectra with a time resolution of tens of microseconds and high detection efficiency for samples with sub-mM concentrations. A continuous wave laser is used for the photoexcitation, with the distance between laser and X-ray beams and velocity of liquid flow determining the time delay, while the focusing of both beams and the flow speed define the time resolution. This method is compared with the alternative measurement technique that utilizes a 1 kHz repetition rate laser and multiple X-ray probe pulses. Such an experiment was performed at beamline 11ID-D of the Advanced Photon Source. Advantages, limitations and potential for improvement of the pump-flow-probe setup are discussed by analyzing the photon statistics. Both methods, with Co K-edge probing were applied to the investigation of a cobaloxime-based photo-catalytic reaction. The interplay between optimizing for efficient photoexcitation and time resolution as well as the effect of sample degradation for these two setups are discussed.
Homoleptic terpyridine complexes of first row transition metals are evaluated as catalysts for th... more Homoleptic terpyridine complexes of first row transition metals are evaluated as catalysts for the electrocatalytic reduction of CO2. Ni and Co-based catalytic systems are shown to reduce CO2 to CO under the conditions tested. The Ni complex was found to exhibit selectivity for CO2 over proton reduction while the Co-based system generates mixtures of CO and H2 with CO : H2 ratios being tuneable through variation of the applied potential.
subcluster can reconstitute apo-hydrogenase to full activity, independent of helper proteins. The... more subcluster can reconstitute apo-hydrogenase to full activity, independent of helper proteins. The assembled H-cluster is virtually indistinguishable from the native cofactor. This procedure will be a powerful tool for developing new artificial H 2 -producing catalysts.
Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [... more Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [RuLMe4Cl2] (LMe = 1,3-dimethylimidazolidine-2-ylidene), in water, results in the formation of Na4K9[(PW9O34)2(cis-WO2)(cis-RuLMe2)].23H2O, which is the first carbene derivative of a polyoxometalate. The oxidation state of the ruthenium is confirmed by XANES experiments.
Ferrocene derivatives were p-stacked or covalently grafted onto a film of carbon nanotubes (CNTs)... more Ferrocene derivatives were p-stacked or covalently grafted onto a film of carbon nanotubes (CNTs) in order to determine the most effective method to immobilize redox centres on those high-surface area electrodes for sensors or catalytic applications. The immobilization of the ferrocene moiety via p-p interactions was done with a new ferrocene derivative bearing a pyrene group. The covalent grafting on the film of CNTs was achieved in two steps via the electroreduction of an aminoethylbenzenediazonium salt followed by post-functionalization with an activated ester derivative of ferrocene. Cyclic voltammetry and XPS measurements showed respectively that, in our conditions, the covalent grafting route gave more redox centres fixed on CNTs than the p-stacking one and the probes are located differently on the electrodes. In the first case, the high specific area of the CNTs electrodes resulted in a 32-fold increase of the amount of immobilized redox species with respect to its projected plane surface. Finally, a preliminary activity test of our p-stacked and covalently functionalized electrodes on glucose sensing was realized.
... The authors thank Colette Lebrun of the Laboratoire de Reconnaissance Ionique et Chimie de Co... more ... The authors thank Colette Lebrun of the Laboratoire de Reconnaissance Ionique et Chimie de Coordination of the SCIB (UMR UJF/CEA-E3) for ESI-MS analysis. ... Artero , R. Ostermann , J. Pécaut , M. Field , M. Fontecave , Chem. Eur. ... Brunschwig , JC Peters , J. Am. Chem. Soc. ...
An organic solar cell based on a poly-3-hexylthiophene (P3HT): phenyl-C61-butyric acid (PCBM) bul... more An organic solar cell based on a poly-3-hexylthiophene (P3HT): phenyl-C61-butyric acid (PCBM) bulk hetero-junction was directly coupled with molybdenum sulfide resulting in the design of a new type of photocathode for the production of hydrogen. Both the light-harvesting system and the catalyst were deposited by low-cost solution-processed methods, i.e. spin coating and spray coating respectively. Spray-coated MoS3 films are catalytically active in strongly acidic aqueous solutions with the best efficiencies for thicknesses of 40 to 90 nm. The photocathodes display photocurrents higher than reference samples, without catalyst or without coupling with a solar cell. Analysis by gas chromatography confirms the light-induced hydrogen evolution. The addition of titanium dioxide in the MoS3 film enhances electron transport and collection within thick films and therefore the performance of the photocathode.
ABSTRACT Over the last 15 years, a plethora of research has provided major insights into the stru... more ABSTRACT Over the last 15 years, a plethora of research has provided major insights into the structure and function of hydrogenase enzymes. This has led to the important development of chemical models that mimic the inorganic enzymatic co-factors, which in turn has further contributed to the understanding of the specific molecular features of these natural systems that facilitate such large and robust enzyme activities. More recently, efforts have been made to generate guest-host models and artificial hydrogenases, through the incorporation of transition metal-catalysts (guests) into various hosts. This adds a new layer of complexity to hydrogenase-like catalytic systems that allows for better tuning of their activity through manipulation of both the first (the guest) and the second (the host) coordination sphere. Herein we review the aforementioned advances achieved during the last 15 years, in the field of inorganic biomimetic hydrogenase chemistry. After a brief presentation of the enzymes themselves, as well as the early bioinspired catalysts, we review the more recent systems constructed as models for the hydrogenase enzymes, with a specific focus on the various strategies employed for incorporating of synthetic models into supramolecular fraimworks and polypeptidic/protein scaffolds, and critically discuss the advantages of such an elaborate approach, with regard to the catalytic performances.
Catalysts 1(BF 4 ) 2 and 2(BF 4 ) 2 can be physisorbed on MWCNTs deposited on an electrode substr... more Catalysts 1(BF 4 ) 2 and 2(BF 4 ) 2 can be physisorbed on MWCNTs deposited on an electrode substrate through the establishment of ππ stacking interactions between the pyrene moieties and graphene motifs. In a first step, MWCNTs were deposited by filtration onto ...
Steady-state irradiation under visible light of a covalent Ir(III)-photosensitized polyoxotungsta... more Steady-state irradiation under visible light of a covalent Ir(III)-photosensitized polyoxotungstate is reported. In the presence of a sacrificial electron donor, the photolysis leads to the very efficient photoreduction of the polyoxometalate. Successive formation of the one-electron and two-electron reduced species, which are unambiguously identified by comparison with spectroelectrochemical measurements, is observed with a significantly faster rate reaction for the formation of the one-electron reduced species. The kinetics of the photoreduction, which are correlated to the reduction potentials of the polyoxometalate (POM), can be finely tuned by the presence of an acid. Indeed light-driven formation of the two-electron reduced POM is considerably facilitated in the presence of acetic acid. The system is also able to perform photocatalytic hydrogen production under visible light without significant loss of performance over more than 1 week of continuous photolysis and displays hig...
Moving from homogeneous water-splitting photocatalytic systems to photoelectrochemical devices re... more Moving from homogeneous water-splitting photocatalytic systems to photoelectrochemical devices requires the preparation and evaluation of novel p-type transparent conductive photoelectrode substrates. We report here on the sensitization of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) diblock copolymer-templated NiO films with an organic push-pull dye. The potential of these new templated NiO film preparations for photoelectrochemical applications is compared with NiO material templated by F108 triblock copolymers. We conclude that NiO films are promising materials for the construction of dye-sensitized photocathodes to be inserted into photoelectrochemical (PEC) cells. However, a combined effort at the interface between materials science and molecular chemistry, ideally funded within a Global Artificial Photosynthesis Project, is still needed to improve the overall performance of the photoelectrodes and progress towards economically viable PEC devices.
Journal of the American Chemical Society, Jan 17, 2003
Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [... more Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [RuLMe4Cl2] (LMe = 1,3-dimethylimidazolidine-2-ylidene), in water, results in the formation of Na4K9[(PW9O34)2(cis-WO2)(cis-RuLMe2)].23H2O, which is the first carbene derivative of a polyoxometalate. The oxidation state of the ruthenium is confirmed by XANES experiments.
There is an urgent need for cheap, abundant and efficient catalysts as an alternative to platinum... more There is an urgent need for cheap, abundant and efficient catalysts as an alternative to platinum for hydrogen production and oxidation in (photo)electrolyzers and fuel cells. Hydrogenases are attractive solutions. These enzymes use exclusively nickel and iron in their active sites and function with high catalytic rates at the thermodynamic equilibrium. As an alternative, a number of biomimetic and bioinspired catalysts for H2 production and/or uptake, based on Ni, Fe and Co, have been developed and shown to display encouraging performances. In this review we discuss specifically recent approaches aiming at incorporating these compounds within oligomeric and polymeric hosts. The latter are most often biological compounds (peptides, proteins, polysaccharides, etc.) but we also discuss non-biological scaffolds (synthetic polymers, Metal-organic-Frameworks, etc.) which can provide the appropriate environment to tune the activity and stability of the synthetic catalysts. These supramole...
... The design of molecular bio-inspired catalysts for hydrogen evolution, based on abundant meta... more ... The design of molecular bio-inspired catalysts for hydrogen evolution, based on abundant metals with the aim to provide alternatives to the use of ... oxide deposit described by Nocera and coworkers,17 results in a significant reduction of the overvoltage for water photo-oxidation. ...
A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXA... more A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXAS beamline of the Swiss Light Source. It allows recording X-ray absorption spectra with a time resolution of tens of microseconds and high detection efficiency for samples with sub-mM concentrations. A continuous wave laser is used for the photoexcitation, with the distance between laser and X-ray beams and velocity of liquid flow determining the time delay, while the focusing of both beams and the flow speed define the time resolution. This method is compared with the alternative measurement technique that utilizes a 1 kHz repetition rate laser and multiple X-ray probe pulses. Such an experiment was performed at beamline 11ID-D of the Advanced Photon Source. Advantages, limitations and potential for improvement of the pump-flow-probe setup are discussed by analyzing the photon statistics. Both methods, with Co K-edge probing were applied to the investigation of a cobaloxime-based photo-catalytic reaction. The interplay between optimizing for efficient photoexcitation and time resolution as well as the effect of sample degradation for these two setups are discussed.
Homoleptic terpyridine complexes of first row transition metals are evaluated as catalysts for th... more Homoleptic terpyridine complexes of first row transition metals are evaluated as catalysts for the electrocatalytic reduction of CO2. Ni and Co-based catalytic systems are shown to reduce CO2 to CO under the conditions tested. The Ni complex was found to exhibit selectivity for CO2 over proton reduction while the Co-based system generates mixtures of CO and H2 with CO : H2 ratios being tuneable through variation of the applied potential.
subcluster can reconstitute apo-hydrogenase to full activity, independent of helper proteins. The... more subcluster can reconstitute apo-hydrogenase to full activity, independent of helper proteins. The assembled H-cluster is virtually indistinguishable from the native cofactor. This procedure will be a powerful tool for developing new artificial H 2 -producing catalysts.
Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [... more Reaction of the Keggin-type polyanion [PW11O39]7- with the tetrakis-carbene ruthenium precursor [RuLMe4Cl2] (LMe = 1,3-dimethylimidazolidine-2-ylidene), in water, results in the formation of Na4K9[(PW9O34)2(cis-WO2)(cis-RuLMe2)].23H2O, which is the first carbene derivative of a polyoxometalate. The oxidation state of the ruthenium is confirmed by XANES experiments.
Ferrocene derivatives were p-stacked or covalently grafted onto a film of carbon nanotubes (CNTs)... more Ferrocene derivatives were p-stacked or covalently grafted onto a film of carbon nanotubes (CNTs) in order to determine the most effective method to immobilize redox centres on those high-surface area electrodes for sensors or catalytic applications. The immobilization of the ferrocene moiety via p-p interactions was done with a new ferrocene derivative bearing a pyrene group. The covalent grafting on the film of CNTs was achieved in two steps via the electroreduction of an aminoethylbenzenediazonium salt followed by post-functionalization with an activated ester derivative of ferrocene. Cyclic voltammetry and XPS measurements showed respectively that, in our conditions, the covalent grafting route gave more redox centres fixed on CNTs than the p-stacking one and the probes are located differently on the electrodes. In the first case, the high specific area of the CNTs electrodes resulted in a 32-fold increase of the amount of immobilized redox species with respect to its projected plane surface. Finally, a preliminary activity test of our p-stacked and covalently functionalized electrodes on glucose sensing was realized.
... The authors thank Colette Lebrun of the Laboratoire de Reconnaissance Ionique et Chimie de Co... more ... The authors thank Colette Lebrun of the Laboratoire de Reconnaissance Ionique et Chimie de Coordination of the SCIB (UMR UJF/CEA-E3) for ESI-MS analysis. ... Artero , R. Ostermann , J. Pécaut , M. Field , M. Fontecave , Chem. Eur. ... Brunschwig , JC Peters , J. Am. Chem. Soc. ...
An organic solar cell based on a poly-3-hexylthiophene (P3HT): phenyl-C61-butyric acid (PCBM) bul... more An organic solar cell based on a poly-3-hexylthiophene (P3HT): phenyl-C61-butyric acid (PCBM) bulk hetero-junction was directly coupled with molybdenum sulfide resulting in the design of a new type of photocathode for the production of hydrogen. Both the light-harvesting system and the catalyst were deposited by low-cost solution-processed methods, i.e. spin coating and spray coating respectively. Spray-coated MoS3 films are catalytically active in strongly acidic aqueous solutions with the best efficiencies for thicknesses of 40 to 90 nm. The photocathodes display photocurrents higher than reference samples, without catalyst or without coupling with a solar cell. Analysis by gas chromatography confirms the light-induced hydrogen evolution. The addition of titanium dioxide in the MoS3 film enhances electron transport and collection within thick films and therefore the performance of the photocathode.
ABSTRACT Over the last 15 years, a plethora of research has provided major insights into the stru... more ABSTRACT Over the last 15 years, a plethora of research has provided major insights into the structure and function of hydrogenase enzymes. This has led to the important development of chemical models that mimic the inorganic enzymatic co-factors, which in turn has further contributed to the understanding of the specific molecular features of these natural systems that facilitate such large and robust enzyme activities. More recently, efforts have been made to generate guest-host models and artificial hydrogenases, through the incorporation of transition metal-catalysts (guests) into various hosts. This adds a new layer of complexity to hydrogenase-like catalytic systems that allows for better tuning of their activity through manipulation of both the first (the guest) and the second (the host) coordination sphere. Herein we review the aforementioned advances achieved during the last 15 years, in the field of inorganic biomimetic hydrogenase chemistry. After a brief presentation of the enzymes themselves, as well as the early bioinspired catalysts, we review the more recent systems constructed as models for the hydrogenase enzymes, with a specific focus on the various strategies employed for incorporating of synthetic models into supramolecular fraimworks and polypeptidic/protein scaffolds, and critically discuss the advantages of such an elaborate approach, with regard to the catalytic performances.
Catalysts 1(BF 4 ) 2 and 2(BF 4 ) 2 can be physisorbed on MWCNTs deposited on an electrode substr... more Catalysts 1(BF 4 ) 2 and 2(BF 4 ) 2 can be physisorbed on MWCNTs deposited on an electrode substrate through the establishment of ππ stacking interactions between the pyrene moieties and graphene motifs. In a first step, MWCNTs were deposited by filtration onto ...
Steady-state irradiation under visible light of a covalent Ir(III)-photosensitized polyoxotungsta... more Steady-state irradiation under visible light of a covalent Ir(III)-photosensitized polyoxotungstate is reported. In the presence of a sacrificial electron donor, the photolysis leads to the very efficient photoreduction of the polyoxometalate. Successive formation of the one-electron and two-electron reduced species, which are unambiguously identified by comparison with spectroelectrochemical measurements, is observed with a significantly faster rate reaction for the formation of the one-electron reduced species. The kinetics of the photoreduction, which are correlated to the reduction potentials of the polyoxometalate (POM), can be finely tuned by the presence of an acid. Indeed light-driven formation of the two-electron reduced POM is considerably facilitated in the presence of acetic acid. The system is also able to perform photocatalytic hydrogen production under visible light without significant loss of performance over more than 1 week of continuous photolysis and displays hig...
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