Highlights from Momentom
Cu2O cubic and polyhedral structures versus commercial powder: Shape effect on photocatalytic activity under visible light
Journal of Saudi Chemical Society (2019), DOI: 10.1016/j.jscs.2019.05.007
Abstract: A simple precipitation-reduction method was used to prepare cubic and polyhedral Cu2O structures. Their morphological, structural, optical and electronic properties were analyzed and compared with those of commercial Cu2O by means of SEM, TEM, XRD, UV–vis DRS, Photoluminescence Spectroscopy and Time Resolved Microwave Conductivity. Methyl orange (MO) photodegradation with visible light (blue-light LEDs, λ = 450–470 nm) was taken as a model reaction to study the photocatalytic activity. According to the results, Cu2O edge-and corner-truncated polyhedral particles significantly decreased the MO initial concentration by adsorption and photocatalysis, whereas, Cu2O cubic particles did not show MO adsorption but slightly higher photocatalytic activity than the polyhedral particles. Commercial Cu2O showed MO adsorption and high electron mobility but it was completely inactive. These results were explained in terms of the crystalline defects that influence both, the adsorption capacity and the photocatalytic activity.
Engineering a cobalt clathrochelate/glassy carbon interface for the Thydrogen evolution reaction
Joumada Al Cheikh, Angel Villagra, Alireza Ranjbari, Alexandre Pradon, Manuel Antuch, Diana Dragoe, Pierre Millet, Loïc Assaud⁎
Applied Catalysis B: Environmental 250 (2019) 292–300, DOI:10.1016/j.apcatb.2019.03.036
Abstract: The purpose of this work was to investigate the electrocatalytic activity of a molecular clathrochelate, containing cobalt as active centre, for the hydrogen evolution reaction (HER) in aqueous acidic media. The electrocatalytic activity of this cobalt complex has been measured using a glassy carbon working electrode, with the complex either dissolved in the electrolyte (homogeneous phase) or electro-grafted at the surface (heterogeneous phase). The complex was electrografted via diazonium derivatives reduction, in an attempt to form a surface monolayer of cobalt clathrochelate, covalently bonded to the glassy carbon substrate. The chemical composition and morphology of the modified electrode have been characterized by electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The HER kinetics on the two electrodes has been analyzed by cyclic voltammetry and electrochemical impedance spectroscopy in two different media: in acetonitrile (by adding increasing amounts of equivalent protons) and in 0.1 M H2SO4 aqueous solution. Tafel slopes and exchange current density values have been determined on both electrodes, in both media, and compared. It was found that the onset of the HER requires a significantly lower overpotential (≈ 800 mV less) when the complex is elec- trografted at the surface of the working electrode. The hydrogen production rate, determined by gas chroma- tography, is reported.
Photocatalytic degradation of organic pollutant with polypyrrole Tnanostructures under UV and visible light
Xiaojiao Yuan, Dita Floresyona, Pierre-Henri Aubert, Thanh-Tuân Bui, Samy Remita, Srabanti Ghosh, François Brisset, Fabrice Goubard, Hynd Remita⁎
Applied Catalysis B: Environmental 242 (2019) 284–292 DOI: 10.1016/j.apcatb.2018.10.002
Abstract: Conjugated polymer nanostructures (CPNs) emerge as a new class of photocatalysts for organic pollutant de- gradation under UV and visible light. Polyprrole (PPy), as a conjugated polymer, exhibits a wide range of ap- plications. We present here the first demonstration of employing pure PPy nanostructures as a very efficient photocatalyst for water depollution. PPy nanostructures were synthesized in hexagonal mesophases (used as soft templates) by chemical polymerization (PPy-NS-c), obtained by radiolysis (PPy-NS-γ), and synthesized without any template via chemical method (PPy-bulk) as bulk. The different PPy samples were characterized by SEM, TEM, FTIR and UV–vis absorption spectroscopy. The photocatalytic activity of both PPy nanostructures (PPy-NS- c and PPy-NS- γ), which remain very stable after several cycles, was evaluated for the degradation of organic pollutant in aqueous solution (phenol and methyl orange were taken as a model pollutant). PPy nanostructures show high photocatalytic activity under both UV and visible light while bulk PPy (PPy-bulk) has no appreciable activity. PPy-NS-c present the highest activity for photodegradation of phenol under UV light, while PPy-NS-γexhibit the best photocatalytic activity under visible light. We demonstrate here that the nanostructuration of these polymers is an important factor for their application in photocatalysis.
Photoluminescence Tuning Through Irradiation Defects in CH3NH3PbI3 Perovskites
Olivier Plantevin*, Stéphanie Valère, Driffa Guerfa, Ferdinand Lédée, Gaëlle Trippée-Allard, Damien Garrot, and Emmanuelle Deleporte
Phys. Status Solidi B, 2019, 1900199, Doi: 10.1016/j.apcatb.2018.10.002
Abstract: Defect engineering is applied to hybrid (CH3NH3)PbI3 organic–inorganic perovskites. These materials have become one of the most promising low- cost alternatives to traditional semiconductors in the field of photovoltaics and light emitting devices. Here Helium ion irradiation at low energy has been used as a tool for the controlled introduction of point defects in both single crystals and polycrystalline thin films. The irradiation defects modify the opto-electronic properties as probed using photoluminescence (PL) spectroscopy from 10 K to room-temperature. Contrary to usual semiconduc- tors, a very good resilience of the PL properties with irradiation is observed, even associated to an enhancement of the optical emission at low temperature. These results are discussed in relation with the tetragonal to orthorhombic low-temperature phase transition below T 1⁄4 160 K. A compari- son between spectra from single crystals and polycrystalline films, both with and without irradiation defects, allows a better understanding of the light emission mechanisms in both kinds of samples. The authors thereby evidence radiation hardness of these materials and the specificity of defects and their impact on light emission properties.
Time-Resolved Interception of Multiple-Charge Accumulation in a Sensitizer–Acceptor Dyad
Angew. Chem. Int. Ed. 2017, 56, 1 – 6, DOI: 10.1002/anie.201706564
Abstract: Biomimetic models that contain elements of photo- synthesis are fundamental in the development of synthetic systems that can use sunlight to produce fuel. The critical task consists of running several rounds of light-induced charge separation, which is required to accumulate enough redox equivalents at the catalytic sites for the target chemistry to occur. Long-lived first charge-separated state and distinct electronic signatures for the sequential charge accumulated species are essential features to be able to track these events on a spectroscopic ground. Herein, we use a double-excitation nanosecond pump–pump–probe experiment to interrogate two successive rounds of photo-induced electron transfer on a molecular dyad containing a naphthalene diimide (NDI) linked to a [Ru(bpy)3]2+ (bpy = bipyridine) chromophore by using a reversible electron donor. We report an unprecedented long-lived two-electron charge accumulation (t = 200 ms).
A new long-range sub-structure found in the tetragonal phase of CH3NH3PbI3 single crystals
V L R Jacques*, A Gallo-Frantz, A Tejeda, D Le Bolloc’h, F Lédée, G Trippé-Allard, D Garrot, P Fertey, E Deleporte and O Plantevin
Journal of Physics D: Applied Physics, 52 (2019) 314001 (9pp) DOI: 10.1088/1361-6463/ab202e
Abstract: Hybrid organic–inorganic perovskites have become one of the most promising low-cost alternatives to traditional semiconductors in the field of photovoltaics and light emitting devices. They combine the attractive features of both organic and inorganic materials within a single composite, for instance with excellent electronic properties. We used x-ray diffraction to reveal a sub-structure within CH3NH3PbI3 single crystals. We could observe the presence of additional peaks with a square symmetry in several monocrystalline samples. We discuss these results in terms of two different models: a super-structure modulated in two in-plane orthogonal directions, and a model with tilted domains with a shallow angle of ~0.6°. In both cases, the modulated or tilted domains appear in regions with small lattice expansion. We show that this last model appears to be the most likely to explain our observations.
Keywords: methylammonium lead triiodide, x-ray diffraction, tetragonal structure, sub-structure
Surface Modification of TiO2 with Au Nanoclusters for Efficient Water Treatment and Hydrogen Generation under Visible Light
M. G. Méndez-Medrano, E. Kowalska, A. Lehoux, A. Herissan, B. Ohtani, S. Rau, C. Colbeau-Justin, J. L. Rodríguez-López,* and H. Remita*
J. Phys. Chem. C, 2016, 120 (43), pp 25010–25022; DOI: 10.1021/acs.jpcc.6b06854
Abstract: Small gold nanoparticles (Au-NPs) were used to modify the surface of titanium dioxide as visible-light absorbers and thermal redox active centers. Au-NPs were synthesized on commercial TiO2 (P25) by reduction with tetrakis(hydroxymethyl)phosphonium chloride. The Au/P25 composites were characterized by different techniques including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). Time-resolved microwave conductivity (TRMC) was used to study the charge-carrier dynamics. The photocatalytic activity of Au/TiO2 was evaluated for the degradations of phenol, 2-propanol, and acetic acid and for H2 production from aqueous methanol solution. The modification of TiO2-P25 with Au-NPs with preferential localization on the anatase phase led to an increase in its photocatalytic activity under UV and visible-light. TRMC signals showed the injection of electrons from Au-NPs into the conduction band of TiO2 under visible-light excitation, as a result of the activation of the localized surface plasmon resonance (LSPR) of the Au-NPs. The action spectra (AS) correlated with the absorption spectra, confirming that the decomposition of acetic acid occurs by a photocatalytic mechanism. The modified TiO2-P25 was also found to provide promising results for hydrogen generation under visible-light. The stability of these plasmonic photocatalysts was also investigated, and the results showed that they can be reused several times without appreciable loss of activity.
Synergetic effect of Ni and Au nanoparticles synthesized on titania particles for efficient photocatalytic hydrogen production
Ana L. Luna, Ekaterina Novoseltceva, Essyllt Louarn, Patricia Beaunier, Ewa Kowalska, Bunsho Ohtani, Miguel A. Valenzuela, Hynd Remita,* and Christophe Colbeau-Justin*
Appl. Catal., B, 2016, 191, pp 18−28; DOI: https://doi.org/10.1016/j.apcatb.2016.03.008
Abstract: Au and/or Ni nanoparticles were synthesized by radiolysis on TiO2 (commercial P25) at various composition (metal content). The modified photocatalysts were characterized by High Resolution Transmission Microscopy (HRTEM), Energy-Dispersive X-ray Spectroscopy (EDS), UV–vis Diffuse Reflectance Spectroscopy (DRS) and X-ray Photoelectron Spectroscopy (XPS). The charge-carrier mobility was studied by Time Resolved Microwave Conductivity (TRMC). The photocatalytic activities were tested under UV–vis irradiation using polychromatic and monochromatic light (action spectrum analysis of apparent quantum efficiency). Surface modified TiO2 with Au and Ni nanoparticles showed high photocatalytic activity for hydrogen evolution from aqueous methanol solution. The enhanced hydrogen evolution rate was obtained for TiO2 co-modified with Au and Ni, where synergetic effect of the two metals was revealed. A very small amount of gold associated to nickel (atomic ratio Ni:Au 5:1 with a total optimized metal loading of 0.5 at%) can induce a significant increase in H2 formation.
Photocatalytic Hydrogen Evolution Using Ni−Pd/TiO2: Correlation of Light Absorption, Charge-Carrier Dynamics, and Quantum Efficiency
Ana L. Luna, Diana Dragoe, Kunlei Wang, Patricia Beaunier, Ewa Kowalska, Bunsho Ohtani, Daniel Bahena Uribe, Miguel A. Valenzuela, Hynd Remita,* and Christophe Colbeau-Justin*
J. Phys. Chem. C, 2017, 121 (26), pp 14302–14311; DOI: 10.1021/acs.jpcc.7b01167
Abstract: TiO2 surface modification with bimetallic nanoparticles (NPs) has demonstrated to be a strategy to enhance the hydrogen generation via photocatalysis and to minimize the use of expensive noble metals. A better understanding of the role of bimetallic NPs is of crucial importance to design efficient photocatalysts. Here, we show a systematic study of surface modification of commercial TiO2 (P25) with mono- and bimetallic (Ni, Pd, and Ni–Pd) NPs synthesized by radiolysis. The photocatalysts were characterized by High Resolution Transmission Microscopy (HRTEM), Scanning Transmission Electron Microscope (STEM), X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), and UV–vis Diffuse Reflectance Spectroscopy (DRS). The charge-carrier dynamics was studied by Time Resolved Microwave Conductivity (TRMC). The photocatalytic activity was evaluated for hydrogen generation under UV–vis irradiation using polychromatic and monochromatic lights (action spectra analysis of apparent quantum efficiency). TiO2 modified with Pd–Ni bimetallic NPs exhibits a high activity for H2 generation, and a synergetic effect of the two metals was obtained. The study of light absorption, charge-carrier dynamics, and photocatalytic activity revealed that the main role of the metal NPs is to act as catalytic sites for recombination of atomic hydrogen.
Photocatalyse : des matériaux nanostructurés aux réacteurs photocatalytiques
Delphine Schaming, Christophe Colbeau-Justin, Hynd Remita
Techniques de l'ingénieur, août 2017. http://www.techniques-ingenieur.fr/base-documentaire/procedes-chimie-bio-agro-th2/chimie-verte-et-nouvelle-gestion-des-dechets-42495210/photocatalyse-des-materiaux-nanostructures-aux-reacteurs-photocatalytiques-nm3600/
Abstract: Photocatalysis has attracted a lot of interest because of its large application in the environmental field. Therefore, development of stable photocatalysts with activity under solar irradiation is a big challenge. Titanium dioxide (TiO2 ) is a semi-conductor widely used. In this article, the possibilities to extend its activity domain in the visible domain and the importance of its nanostructuration will be particularly described. Other photocatalytic materials as well as the possibility to insert them in reactors for applications at the industrial scale will be also presented in the article.
Time-Resolved Interception of Multiple-Charge Accumulation in a Sensitizer–Acceptor Dyad
Stéphanie Mendes Marinho, Minh-Huong Ha-Thi, Van-Thai Pham, Annamaria Quaranta, Thomas Pino, Christophe Lefumeux, Thierry Chamaillé, Winfried Leibl, and Ally Aukauloo
Angew. Chem. Int. Ed. 2017, 56, pp. XX. DOI: https://doi.org/10.1002/anie.201706564
Abstract: Biomimetic models that contain elements of photosynthesis are fundamental in the development of synthetic systems that can use sunlight to produce fuel. The critical task consists of running several rounds of light-induced charge separation, which is required to accumulate enough redox equivalents at the catalytic sites for the target chemistry to occur. Long-lived first charge-separated state and distinct electronic signatures for the sequential charge accumulated species are essential features to be able to track these events on a spectroscopic ground. Herein, we use a double-excitation nanosecond pump–pump–probe experiment to interrogate two successive rounds of photo-induced electron transfer on a molecular dyad containing a naphthalene diimide (NDI) linked to a [Ru(bpy)3]2+ (bpy=bipyridine) chromophore by using a reversible electron donor. We report an unprecedented long-lived two-electron charge accumulation (t=200 (micro)s).
Ex situ solid electrolyte interphase synthesis viaradiolysis of Li-ion battery anode–electrolyte system for improved coulombic efficiency
Fanny Varenne, John P. Alper, Frédéric Miserque, Chandra Sekhar Bongu, Adrien Boulineau, Jean-Frédéric Martin, Vincent Dauvois, Alexandre Demarque, Mickaël Bouhier, Florent Boismain, Sylvain Franger, Nathalie Herlin-Boimea and Sophie Le Caër *
Sustainable Energy Fuels, 2018, 2, 2100 DOI: 10.1039/c8se00257f
Abstract: The radiolysis of a mixed solvent electrolyte–carbon anode material is investigated for the first time. The present work demonstrates the radiolytic growth of an SEI with a chemical composition similar to that formed during electrochemical cycling, as determined by XPS. The quantity of the SEI increases with increasing irradiation dose. Degradation products formed in the liquid and gas phase are also identified as matching those formed during electrochemical cycling. TEM results support the XPS results of increasing SEI content with increasing irradiation dose. Electrochemical characterization by galvanostatic cycling of test cells indicates that the radiolysis generated SEI greatly improves first cycle efficiency of the materials assembled in half cells, and impedance spectroscopy supports the result with an increase in resistivity observed for irradiated samples. This first study opens the door to the use of irradiation tools for the artificial generation of an SEI and for producing LIB anode materials with improved performance.
Optimal feed-in-tarifs for Household Photovoltaic Panels in France
Anna Creti*, Maria Eugenia Sanin
Optimal Policy and Network E ects for the Deployment of Zero Emission Vehicles
Guy Meunier, Jean-Pierre Ponssard
Policies and deployment for Fuel Cell Electric Vehicles an assessment of the Normandy project
Julien Brunet, Jean-Pierre Ponssard*
Defining the Abatement Cost in Presence of Learning-by-Doing: Application to the Fuel Cell Electric Vehicle
Anna Creti, Alena Kotelnikova, Guy Meunier, Jean-Pierre Ponssard
Abstract: We consider a partial equilibrium model to study the optimal phasing out of polluting goods by green goods. The unit production cost of the green goods involves convexity and learning-by-doing. The total cost for the social planner includes the private cost of production and the social cost of carbon, assumed to be exogenous and growing at the social discount rate. Under these assumptions the optimization problem can be decomposed in two questions: (i) when to launch a given schedule; (ii) at which rate the transition should be completed that is, the design of a transition schedule as such. The first question can be solved using a simple indicator interpreted as theMAC of the whole schedule, possibly non optimal.
The case of hydrogen vehicle (Fuel Cell Electric Vehicles) offers an illustration of our results. Using data from the German market we show that the 2015–2050 trajectory foreseen by the industry would be consistent with a carbon price at 52€/t. The transition cost to achieve a 7.5 M car park in 2050 is estimated at 21.6 billion € that is, to JEl 4% discount rate, 115 € annually for each vehicle which would abate 2.18 tCO2 per year.
Spatial Heterogeneity of Sustainable Transportation Offer Values: A Comparative Analysis of Nantes Urban and Periurban/Rural Areas
Julie Bulteau*, Thierry Feuillet and Rémy Le Boennec
Optimal Policy and Network Effects for the Deployment of Zero Emission Vehicles
Guy Meunier, Jean-Pierre Ponssard