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[en] These two thematic issues of Comptes Rendus Chimie (February and April-May 2006) contain papers contributed to the 15. International conference on Photochemical Conversion and Storage of Solar Energy (IPS-15), held from 4 to 7 July 2004 at the Pharmacy Faculty in Paris (France). With nearly 400 individuals attending, representing academics, national laboratories, industry from 33 countries, and with several exhibitions in the vendor section, the conference was most certainly a well attended success. Among the 340 presentations given during the meeting (plenary and invited lectures, oral and poster presentations), 59 will be found in this publication. The goal of this thematic issue was to provide a broad overview of the various topics covered by the IPS series, and happily the conference committee did not need to press participants at all to provide written versions of their research. A thorough review process insured that this publication represents the most novel and well-received contributions of the conference, in keeping with the high standards of the Comptes rendus. In this issue, we cover a range of topics, including photo-generated electron and energy transfer, bio-mimetic systems, dye-sensitized and polymer solar cells, environmental chemistry and design of nano-materials for photo-conversion. From the included prints, we can see the advanced knowledge base accumulated in the past 3 years regarding the structure and function of photosystem II, providing a more complete understanding of the architecture of the center for photosynthetic oxygen evolution. Today, we apply photo-catalysis in numerous applications, from air and water purification to the production of self-cleaning surfaces on windows and street lamps. These applications have attracted the interest of a wide variety of industrial sectors, especially to those using TiO2-coated materials that make it possible to maintain clean, hydrophilic conditions on a surface without the addition of any chemicals in the process. In recent years, the intensive research and development of dye-sensitized solar cells has been established to understand the mechanisms of electron transfer, to improve the energetic efficiency and to expand the limits of cell durability in more extreme environmental conditions. (author)
[en] Anaerobic disintegration of organic matter is a particular phenomenon in the Black Sea because of the set up of deposits of hydrogen sulphide, H2S, having high concentrations. The formation of such deposits is due to the absence of upward streams at depths larger than 100 meters. In Black Sea there is an oxic layer located roughly between 50 and 200 meters from which downwards begins the anoxic layer. If the equilibrium in Black Sea is not kept under control, an ecological disaster is possible. The first signals will be observed in surface waters, than, if the equilibrium is further disturbed the depth sulphides and the hydrogen sulphide deposits can develop up to inflammable and even explosive phases. This paper presents some solutions to reduce the hydrogen sulphide from Black Sea with a particular stress upon the electrochemical method. (authors)
[en] In the study, the authors prepared four heterogeneous catalysts with thiophene oligomers (organic semiconductor) by oxidative polymerization of thiophene with FeCl_3. Photocatalyst Fe-ZSM-5-en-ULT was tested for the ability to reduce CO_2 in the water under VIS light. After the reaction, the reaction mixture was analyzed by gas chromatography (Head Space GC-MS). Organic compounds originate in the reaction mixture. To clarify the mechanism of CO_2 reduction, the authors performed also EPR measurements due to detection of reactive radical intermediate products in the reaction system. (Authors)
[en] Commercial nanocrystalline titania (titanium dioxide, TiO2) has been used to make TiO2 films, which were employed to photodegrade several organic substances under photocatalytic (PC) or photoelectrochemical (PEC) operation. Hydrogen was produced during both operations while electricity was additionally produced during the PEC operation. Both processes were studied as typical examples of the current trend in the effort to produce useful forms of energy by photodegradation of organic waste materials. (authors)
[en] Picosecond laser spectroscopy has been used to study two photo-activated electron transfer reactions: - a bimolecular electron transfer reaction between a sensitizer, DODCI, and an electron acceptor, methylviologen. The two radical ions created with an electron transfer efficiency γ ≅ 0.07 have been identified in picosecond and nanosecond laser absorption spectroscopy by adding selective solutes such as para-benzoquinone (an electron acceptor) or L(+) ascorbic acid (an electron donor). - an intramolecular electron transfer reaction in a triad molecule consisting of a tetra-aryl-porphyrin covalently linked to both a carotenoid and a quinone. The photoinduced charge separation occurs within 30 ps and leads, with a yield of 25 pc, to the formation of a zwitterion whose half-life is 2.5 μs. The experimental results obtained in these two studies show an effective decrease in the recombination rate of the two radical ions created in the encounter pair. (author)
[fr]Ce memoire presente l'etude, par spectroscopie laser picoseconde, de deux reactions de photo-transfert d'electron: - une reaction bimoleculaire de transfert d'electron entre un photosensibilisateur, le DODCI, et un accepteur d'electron, le methylviologene, dans laquelle les deux radicaux ions crees avec un rendement de 7 pc ont ete mis en evidence. L'identification des especes formees a ete confirmee en photolyse laser nanoseconde par addition dans le milieu reactionnel de solutes selectifs, accepteur d'electron comme la parabenzoquinone ou donneur d'electron comme l'acide L(+) ascorbique. - une reaction intramoleculaire de transfert d'electron dans une molecule triade constituee d'une carotenoporphyrine liee a une quinone dans laquelle la separation photoinduite de charges est realisee en un temps voisin de 30 ps et conduit a la formation d'un zwitterion de duree de vie microseconde avec un rendement de 25 pc. Les resultats obtenus lors de ces deux etudes indiquent un ralentissement effectif de la reaction de recombinaison des radicaux ions crees dans la paire de rencontre. (auteur)
[en] In this chapter author deals with the light and photochemical reactions as photosynthesis, visions, ozone layer depletion, photodynamic therapy, laser and its applications and photochromism. Principle of solar cells and solar energy conversion are presented.
[en] It is universally apparent that environmental and energy transition must evolve in order to meet the needs of a growing world population while still heeding environmental constraints. This change over time will be based on a sustainable energy mix, and consequently the use of renewable energy sources is likely to intensify over the coming decades in respond to rising demand for electricity worldwide. The International Energy Agency (IEA) predicts that 40% of electricity will come from renewable sources by 2050. Some of these renewable forms of energy generate power on an irregular and intermittent basis, and energy storage offers one solution for deploying these intermittent energy sources more widely as part of an efficient smart grid. (authors)
[en] In this study, Fe-ZSM-5-PT photocatalyst was synthesized and were evaluated for CO2 reduction under UV-VIS and visible light irradiation. In this work, Fe-ZSM-PT photocatalyst was synthesized by oxidative polymerization of thiophene with FeCl3. Prepared photocatalyst is thermal stable and his absorption edge is around 650 nm. The activity of Fe-ZSM-PT for CO2 photoreduction with water under UV-VIS and visible light was tested. In both cases we observe production of lower alcohols and under UV-VIS irradiation were detected higher alcohols too.
[en] Within the framework of researches on the conversion of solar energy into a storable chemical energy through the production of hydrogen, this thesis more particularly addresses the system based on the use of semi-conductive electrodes in contact with an electrolytic solution. The author first proposes a review of the theoretical backgrounds of photo-electrochemical conversion (PEC), and more particularly outlines the difference between an electrolyte-semiconductor junction and a metal-semiconductor junction, discusses the various parameters which govern the selection of a semiconductor for a PEC cell (stability, electronic affinity, forbidden bandwidth). Then, he describes experimental assemblies used in this research, and gives results obtained on p-type gallium phosphide, describes a TiO2-n/GaP-p battery which has been developed. In the next parts, he describes the preparation modes of alpha-hematite, and presents and discusses results obtained on these single crystals. Impedance measurements and the photo-electrochemical behaviour of hematite are explained. (author)
[fr]Dans le premier chapitre nous passons en revue les bases theoriques de la conversion PEC. Nous montrons en particulier ce qui differencie la jonction electrolyte-semiconducteur de la jonction metal-semiconducteur, ainsi que les divers parametres qui guident le choix d'un semiconducteur pour une cellule PEC: stabilite, affinite electronique, largeur de la bande interdite. Le second chapitre est consacre a la description des montages experimentaux utilises dans cette etude. Le chapitre III donne les resultats obtenus sur le phosphure de gallium de type p. Nous y decrivons en particulier la pile TiO2-n/GaP-p que nous avons realisee, et discutons l'important decalage observe entre les valeurs du potentiel de bande plate et le seuil de photocourant. Au chapitre IV sont decrits les modes de preparation des monocristaux d'hematite-alpha dopee. Enfin les resultats obtenus sur ces monocristaux sont rassembles dans le cinquieme et dernier chapitre. Nous y montrons que la pile Fe2O3-n/GaP-p que nous avions projetee n'a pas pu etre realisee. Les mesures d'impedance ainsi que le comportement photoelectrochimique de l'hematite sont attribues a la presence d'un niveau localise qui peut etre mis en evidence par des mesures d'absorption optique et de photocourant. (auteur)