Die Phosphorylierung als posttranslationale Modifikation von Proteinen spielt bei Signalwegen in Zellen eine große Rolle. Für die Entschlüsselung des molekularen Mechanismus der circadianen Uhr ist es daher von Interesse, die Phosphorylierungsstellen beteiligter Proteine zu identifizieren. Im Rahmen dieser Arbeit wurden die Proteine Period I und II mittels Flüssigkeitschromatographie und Tandemmassenspektrometrie (LC-MS/MS) auf Phosphorylierungsstellen untersucht. Hierbei lag der Fokus auf der Verbesserung bestehender Methoden, um eine bessere und umfassendere Identifizierung der Phosphorylierungsstellen, insbesondere in Bezug auf mehrfach phosphorylierte Peptide, zu erreichen. Der Arbeitsablauf beinhaltete die Verwendung mehrerer Proteasen, um eine hohe Sequenzabdeckung des Proteins zu erreichen. Nach der Proteolyse wurden die Phosphopeptide mittels Titandioxid angereichert. Hierbei und bei der LC-MS/MS-Analyse wurde Citrat als Additiv verwendet, welches eine bessere Chromatographie multiphosphorylierter Peptide ermöglicht. Bei der MS/MS-Analyse wurden CID und ETD als Fragmentierungsmethoden eingesetzt. Es konnten durch diese Methodik 30 bzw. 42 Phosphorylierungsstellen an den Proteinen Period I und II identifiziert werden, von denen 26 bzw. 14 zuvor nicht beschrieben waren. Nach der qualitativen Identifizierung wurden quantitative Varianten der optimierten Analytik untersucht, um die biologische Funktion der gefundenen Phosphorylierungsstellen untersuchen zu können. Hierbei wurden das metabolische Labeling der Zellen mit 15N-stickstoffhaltigen Aminosäuren und die säurekatalysierte Isotopenmarkierung auf Peptidebene mit 18O-Sauerstoff untersucht. Mit einer optimierten Variante der säurekatalysierten Isotopenmarkierung mit 18O-Sauerstoff lassen sich die Carboxygruppen der Peptide in 5h 30min mit einer Rate von >97% 18O-Sauerstoff markieren. Mit dieser Methode können weitere funktionelle Untersuchungen der Phosphorylierung an den Period-Proteinen durchgeführt werden. / Protein phosphorylation, a posttranslational modification, plays an important role in signal cascades in cells. In order to understand the molecular mechanism of the circadian clock, it is thus of interest to identify the phosphorylation sites on proteins contributing to the system. During the work for this thesis, the proteins Period I and II were analyzed for phosphorylation sites with liquid chromatography and tandem mass spectrometry (LC-MS/MS). Hereby the focus was on improving existing methods in order to better identify multi-phosphorylated peptides. In the workflow, the Period proteins were digested with several proteases in order to archive a high sequence coverage for analysis. After proteolysis the phosphopeptides were subsequently enriched with titanium dioxide. During phosphopeptide enrichment and reversed phase chromatography, citrate was used as an additive for a better chromatography and recovery of multiphosphorylated peptides. During LC-MS/MS analysis, CID and ETD were used as fragmentation mechanisms in the mass spectrometer. Using these methods, 30 and 42 phosphorylation sites could be identified on the proteins Period I and II, respectively, including 26 and 14 which were previously unpublished. In order to unravel the biological function of these phosphorylation sites, quantitative methods for the optimized LC-MS approach were investigated. This included the metabolic labeling of cells with amino acids containing 15N-nitrogen as well as acid catalyzed 18O-oxygen labeling on peptide level. The developed optimized variant of acid catalyzed 18O-oxygen labeling achieves an inclusion of 18O-oxygen at the peptide carboxy groups with a rate of >97% in 5h 30min. This method can be used for further investigation of the biological function of the phosphorylation on the Period proteins.

Im Rahmen dieser Arbeit wurde ein Niedertemperatur Sol-Gel Spin-Coating Verfahren entwickelt, mit dem sich Metalloxide und -fluoride in Form von Nanometer-dicken Schichten abscheiden lassen. Ziel dieses Verfahrens ist die Herstellung von anti- (AR) und hoch reflektierenden (HR) Schichtsystemen, die aus einem alternierenden Aufbau von niedrig brechenden und hoch brechenden Materialien bestehen. Zur Darstellung der Metallfluoride wurde dabei eine neuartige nichtwässrige Sol-Gel Synthese ausgehend von Metallalkoxiden und in Alkoholen einkondensiertem Fluorwasserstoff angewendet. Die abgeschiedenen Schichten, die bei 100 °C getrocknet wurden, sind mit REM, TEM und AFM auf ihre morphologische Struktur, mit EDX und XPS auf ihre chemische Zusammensetzung und mit Ellipsometrie und UV-vis Transmissionsspektroskopie auf ihre optischen Eigenschaften hin untersucht worden. Mit diesem Verfahren gelang die Präparation von homogenen MgF2- und TiO2-Schichten mit geringen Rauheiten (Ra < 2,0 nm) auf Si- und SiO2-Substraten. Die MgF2-Schichten haben einen Brechungsindex von n500 = 1,36. Die TiO2-Schichten weisen einen Brechungsindex von n500 = 2,05 auf. Die Dicken der MgF2- und TiO2-Schichten sind zwischen 25 nm und 500 nm einstellbar. Durch einen alternierenden Aufbau von MgF2- und TiO2-Schichten gelang außerdem erstmalig die Herstellung von Metallfluorid- und Metalloxid-basierten Schichtsystemen über einen Niedertemperatur Sol-Gel Prozess. Mit Hilfe der bestimmten optischen Eigenschaften der MgF2- und TiO2-Einzelschichten wurden einfache AR und HR Designs entwickelt und aufgebaut. Die Transmissionsspektren der Designs und der jeweiligen Schichtsysteme zeigten dabei gute Übereinstimmungen, gleiches galt für die mit Hilfe der Spektralellipsometrie aufgenommenen Reflexionsspektren. In dieser Arbeit konnte erstmals gezeigt werden, dass sich das Niedertemperatur Sol-Gel Verfahren prinzipiell zur Herstellung von einfachen AR und HR Schichtsystemen eignet. / This work deals with the development of a low temperature sol-gel spincoating process for thin films with thicknesses in the nanometer range based on metal oxides and metal fluorides. Optical films such as anti-reflective (AR) or high reflective coatings are of much interest and consist of alternating dielectric layers of low and high refractive index materials. Regarding the general procedure for the metal fluorides a novel nonaqueous sol-gel synthesis starting from metal alkoxides and alcohol-dissolved HF was used. The coatings were dried and calcined at 100 °C. The morphology of these films was characterised with REM, TEM and AFM. EDX and XPS were used to indentify the chemical composition and ellipsometry and UV-vis spectroscopy to determine the optical properties of the films. This new process allows the preparation of homogeneous magnesium fluoride and titanium dioxide layers with low roughness (Ra < 2.0 nm) on Si and SiO2 substrates. The thicknesses of the MgF2 and TiO2 single layers were adjustable between 25 nm and 500 nm depending on the number of coating steps and on the concentration of the used sols. The MgF2 layers had a refractive index of n500 = 1.36 and the TiO2 layers a refraction index of n500 = 2.05. For the first time, an alternating metal fluoride and oxide multilayer system was produced with a low temperature sol-gel method (consisting of MgF2 and TiO2). Based on the determined optical constants of the MgF2 and TiO2 single layers, AR and HR multilayer systems were calculated and fabricated. The transmission spectra of the designs and the corresponding multilayer were in good agreement. Similar results were obtained with the reflection spectra determined with spectral ellipsometry. The presented investigations were able to show that the developed low temperature sol-gel process using the spin-coating technique is suitable for the preparation of simple AR and HR multilayer systems.

In dieser Arbeit wurde ein Modell-Katalysator-Ansatz angewandt um Mischoxide mit Molybdän und Titan zu untersuchen. Die Schichten wurden auf TiO2(110) Einkristallen durch Verdampfen der Metalle in einer O2 Atmosphäre und in UHV und Nachbehandlung der Filme vorbereitet. Verschiedene Präparationen wurden in der Studie untersucht und diese werden in sechs Kategorien dargestellt. Wenn Mo und Ti in O2 gemeinsam aufgedampft wurden, wurde das meiste Mo an der Oberfläche abgeschieden mit einer nur geringen Mo-Konzentration in tieferen Schichten. Eine Mischung von Mo in TiO2 war sehr begrenzt, und die stimmt mit dem Phasendiagramm MoO2 und TiO2 überein. Mo6+ und Mo4+ sind die dominierenden Oxidationsstufen in den meisten der Schichten, wobei Mo6+ stets näher an der Oberfläche war als Mo4+. Schichten, in denen Mo vollständig in TiO2 gelöst ist, konnten durch Abscheidung von Metallen in UHV und Post-Oxidation der Filme erstellt werden. Im Inneren des TiO2 Gitters hat Mo die Oxidationsstufe 4+. Aufdampfen von Mo in O2 bei Raumtemperatur und anschließendes Tempern in UHV führte zur Bildung zweier Arten von Merkmalen in den STM-Bildern. Diese waren im UHV stabil bis mindestens 1000 K. Die Schichten mit hoher Mo-Konzentrationen erschienen uneinheitlich in den STM-Bildern aber sie zeigte das TiO2(110)-(1x1) LEED-Muster. Der Anstieg in der Mo-Konzentration führte zur Blockierung der Überbrückung Sauerstoffleerstellen (BOVs), was durch STM und Wasser-TPD nachgewiesen wurde. Die Reaktivitäten der Schichten wurden mit Methanol- und Ethanol-TPD getestet. Eine unerwartete Formaldehyd/Methanbildung bei hohen Temperaturen (~650 K) wurde bei der Methanol-TPD von reinem TiO2(110) beobachtet und mit BOVs in Verbindung gebracht. Der Anstieg der Mo-Konzentration unterdrückte diesen Effekt sowie die Ethylenbildung (~600 K) beim Durchführen von Ethanol-TPD. Sowohl in Ethanol als auch Methanol-TPD wurden neue Reaktionswege zu Ethylen und Methan-Bildung bei ~500 K beobachtet. / In this work, a model-catalyst approach has been taken to study oxide mixtures containing molybdenum and titanium. The layers were prepared on TiO2(110) single crystals by evaporating the metals in an O2 atmosphere or in UHV and post treating the deposited material. Different preparation procedures were employed in the study and these are presented in six categories. When Mo and Ti were co-deposited in O2, most of the molybdenum stayed at the surface with only a small Mo concentration in deeper layers. Mixing of Mo into TiO2 was very limited, consistent with the phase diagram of MoO2 and TiO2. Mo6+ and Mo4+ were the dominant oxidation states in most of the layers and Mo6+ was always nearer to the surface than Mo4+. Layers where Mo was completely mixed into TiO2 could be prepared by depositing metals in UHV and post-oxidizing the deposited material. Inside the TiO2 lattice, Mo had an oxidation state of 4+. Depositing Mo in O2 at room temperature and post annealing in UHV led to the formation of two types of features in the STM images. These features were stable in UHV up to at least 1000 K. The layers with high Mo concentrations appeared patchy in the STM images but they still exhibited the TiO2(110)-(1x1) LEED pattern. The increase in Mo concentration led to the blocking of the bridging oxygen vacancies (BOVs) as evidenced by STM and water TPD. The reactivities of the layers were tested by methanol and ethanol TPD. An unprecedented high temperature (~650 K) formaldehyde/methane formation channel was observed in the methanol TPD of clean TiO2(110) and was associated with BOVs. The increase in the Mo concentration led to the vanishing of this channel as well as the ethylene formation channel (~600 K) in the case of ethanol TPD. In both ethanol and methanol TPD, new reaction channels towards ethylene and methane formation at ~500 K appeared.

In der Entwicklung von Technologien für die nachhaltige Erzeugung, Speicherung und Umwandlung von Energie werden Hochleistungskatalysatoren benötigt. Im Rahmen dieser Arbeit werden verschiedene Übergangsmetall-basierte Katalysatoren, namentlich TiO2/Kohlenstoff-Komposite, anorganisch-organische Hybridsysteme auf Basis von NiFe Phosphonaten sowie Ni Phosphide, synthetisiert, charakterisiert und hinsichtlich ihrer photo- und elektrokatalytischen Eigenschaften untersucht. Es wird gezeigt, dass die Grenzflächeneigenschaften der TiO2/C-Komposite signifikant durch die Gestaltung des Heizvorgangs während der Synthese beeinflusst werden. Insbesondere der Einsatz von Mikrowellenstrahlung vermag die Synthese von Kohlenstoff-basierten Materialien positiv zu beeinflussen. Schnelles Erwärmen führt zu stärkeren Wechselwirkungen zwischen Nanopartikeln und Kohlenstoff, einheitlicheren Beschichtungen und kleineren Partikeln mit schmaleren Partikelgrößenverteilungen, wodurch die photokatalytische Aktivität verbessert wird. Schichtartige, hybride NiFe-Phenylphosphonat-Materialien werden ausgehend in Benzylalkohol dargestellt und ihre Aktivität in der OER im basischen Milieu untersucht. Die Hybridpartikel werden in-situ in NiFe-Hydroxid Nanoschichten umgewandelt. Röntgenspektroskopische Untersuchungen deuten auf eine induzierte, teilweise verzerrte Koordinationsumgebung der Metallzentren im Katalysator hin. Die Kombination der synergistischen Effekte zwischen Ni und Fe mit den strukturellen Eigenschaften des Hybridmaterials ermöglicht einen effizienten Katalysator. Weiterhin werden Nickel-Phosphide durch die thermische Behandlung der Phenyl- oder Methylphosphonate des Nickels, welche Schichtstrukturen aufweisen, in H2(5%)/Ar-Atmosphäre synthetisiert. Ni12P5, Ni12P5-Ni2P und Ni2P Nanopartikel, die mit einer dünnen Schicht aus Kohlenstoffmaterial beschichtet sind, werden erhalten. Ni12P5-Ni2P und Ni2P Nanopartikel katalysieren die Wasserstoffentwicklungsreaktion (HER) im Sauren effektiv. / High-performance catalysts play a key role in the development of technologies for sustainable production, storage, and conversion of energy. In this thesis, transition-metal-based catalysts, including TiO2/carbon composites, hybrid organic-inorganic NiFe phosphonates, and Ni phosphides are synthesized, characterized, and investigated in photocatalytic or electrocatalytic reactions. TiO2 is frequently combined with carbon materials, such as reduced graphene oxide (rGO), to produce composites with improved properties. TiO2 is more efficiently stabilized at the surface of rGO than amorphous carbon. Rapid heating of the reaction mixture results in a stronger coupling between the nanoparticles and carbon, more uniform coatings, and smaller particles with narrower size distributions. The more efficient attachment of the oxide leads to better photocatalytic performance. Layered hybrid NiFe-phenylphosphonate compounds are synthesized in benzyl alcohol, and their oxygen evolution reaction (OER) performance in alkaline medium is investigated. The hybrid particles transformed in situ into NiFe hydroxide nanosheets. X-ray absorption spectroscopy measurements suggest the metal sites in the active catalyst inherited partly the distorted coordination. The combination of the synergistic effect between Ni and Fe with the structural properties of the hybrid results in an efficient catalyst that generates a current density of 10 mA cm-2 at an overpotential of 240 mV. Moreover, nickel phosphides are synthesized through thermal treatment under H2(5%)/Ar of layered nickel phenyl- or methylphosphonates that act as single-source precursors. Ni12P5, Ni12P5-Ni2P and Ni2P nanoparticles coated with a thin shell of carbonaceous material are produced. Ni12P5-Ni2P and Ni2P NPs efficiently catalyze the hydrogen evolution reaction (HER) in acidic medium. Co2P and CoP NPs are also synthesized following this method.

A significant issue affecting the aquaculture and water industries is the presence of off-flavour compounds in water, which cause problems by imparting an undesirable earthy/musty flavour and smell to water and fish. Two predominant off-flavour compounds are geosmin (GSM) and 2-methylisoborneol (MIB). These compounds are produced by several varieties of cyanobacteria and actinomycetes as metabolic products and can be detected by humans at concentrations as low as 0.015 mg L-1. Removal of GSM and MIB from potable waters has proven to be inefficient using standard water treatment such as filtration, coagulation, flocculation, sedimentation and chlorination. Activated carbon and membrane processes can physically remove GSM and MIB, but do not destroy them, and ozone treatment can be expensive. Titanium dioxide (TiO2) photocatalysis has recently been demonstrated to rapidly degrade GSM and MIB. When the semiconductor catalyst is illuminated with ultraviolet light simultaneous oxidation and reduction reactions occur. Pollutants are broken down into mineral acids, carbon dioxide and water. This study was conducted to determine if TiO2 photocatalysis, using a pelleted form of TiO2 called Hombikat K01/C, was a suitable method for the treatment of potable water. Additionally an analytical method was developed to rapidily analyse the large number of samples generated. Two reactors, a bench scale batch reactor and pilot scale flow reactor, were developed and used to evaluate the efficacy of Hombikat K01/C TiO2 photocatalysis in degrading GSM. The batch reactor, containing Hombikat K01/C, was used to investigate the effect of numerous experimental variables on the photocatalysis of GSM, including initial substrate concentration, pH, light intensity, aeration rate, the presence of additional reactants, and catalysis conducted in deuterated water. GSM was rapidly degraded using the TiO2 batch reactor, with the rate of GSM degradation most affected by light intensity and additional reactants, though pH also had a notable effect. A kinetic isotope effect of 1.61 was observed for the destruction of GSM using Hombikat K01/C TiO2. The flow reactor was also found to efficiently degrade GSM in raw waters. The rate of GSM destruction was found to be significantly lowered by UV shielding of the catalyst, caused by constituents of raw the water used, and the presence of additional reactants. The pilot scale flow reactor was also successfully evaluated in Denmark using gesomin contaminated water from an eel farm

L'objectif de cette étude était de réaliser des revêtements de TiO2 présentant une large variété de morphologies et d'établir des corrélations entre la structure de ces couches et leurs propriétés fonctionnelles, notamment la photocatalyse. Deux voies de synthèse employant le même précurseur, le tétra-isopropropoxide (TTIP) de titane, ont été utilisées, le procédé sol-gel et le dépôt chimique en phase vapeur (MOCVD). L'emploi de ces deux techniques permet de produire TiO2 sous une large gamme de morphologies mais avec des variétés polymorphiques similaires. Les revêtements synthétisés ont été caractérises afin de déterminer leur composition polymorphique, la taille des cristallites, la surface spécifique, la rugosité et l'épaisseur. Puis leur activité photocalytique pour la dégradation du bleu de méthylène a été déterminée. Par voie sol-gel, des dispersions de nano-cristallites de TiO2 dans l'eau, stables sur une longue durée (plus d'un an) en termes de composition polymorphique, taille d'agglomérats et de cristallites ont été synthétisées. Les revêtements ont été réalisés par tape-casting et dip-coating. Pour la synthèse en MOCVD, un plan d'expérience (PeX) a été utilisé, à notre connaissance pour la première fois. Il a permis de déterminer, d'une manière efficace et économique (avec un nombre minimum de tests expérimentaux), les paramètres les plus importants du procédé contrôlant les diverses propriétés quantifiables du revêtement. Il a aussi permis de mettre en évidence les interactions entre les paramètres de synthèse et leur effet sur la structure du revêtement. Les conclusions tirées du PeX sont en accord avec les résultats obtenus lors des études précédentes. L'analyse en composantes principales (ACP) a été réalisée pour avoir une vue globale de la façon dont les diverses propriétés des revêtements sont reliées entre elles / The overall objectives of this study was to find an environmental-friendly and simple procedure to synthesize titanium-dioxide, as well as, to determine the relation between the structural and functional properties of titanium dioxide coatings. Both of these objective have been attained in this study. By the sol-gel technique, titanium dioxide sols were synthesized by the hydrolysis of titanium(IV)isopropoxide. Nanocrystalline dispersions of TiO2 in water were prepared that were suitable for coatings and having long-term stability (more than 1 year) in terms of polymorphic composition, crystallite and agglomerate size. A design of experiments (DoE) was utilised, to our knowledge, for the first time in MOCVD for the synthesis of TiO2 coatings. It was employed to determine, in a timely and economical manner, the most significant process parameters for any quantifiable property of the coating and to highlight the interaction between these operating parameters, as well as, the correlation between the structure of the coating and the process. The conclusions drawn from the DoE were compared to results obtained by previous studies and were found to concur. Therefore, the DoE was successful in screening the most important process parameters, with a minimum number of experimental trials. For most of the properties that were under investigation, the DoE showed that, the deposition temperature and reactor pressure were, often-times, the most significant. Therefore, to change the microstructure and composition of MOCVD coatings, changing these process parameters will ensure the highest impact. It has to be stressed that the conclusions drawn from the DoE are restricted to the experimental range that was under investigation. Principal Component Analysis (PCA) was conducted to have an overall view of how the different properties of the coatings related with one another. The interpretations made from this analysis were that the photocatalytic (PC) activity of the coatings produced did not relate strongly to the polymorphic composition, which is contrary to literature review and is explained to be a result of the different morphologies that lead to different porosities and specific surface area. The PC activity did not depend on the mass over a critical mass. With this analysis it appeared to be clear that the porosity and specific surface area played a larger role than polymorphic composition. This hypothesis has to be verified because we did not succeed in determining the specific surface area of our coatings during this study. However, some preliminary tests have been conducted showing that cyclic voltametry could be used to evaluate the surface area of our films

[pt] No presente trabalho foi realizada a síntese do anatásio nanométrico partindo de um precursor comercial de baixo custo, passando pelo estágio intermediário de nanotubos de titanatos (TTNTs). Após a síntese alcalina hidrotérmica os TTNTs foram tratados termicamente a 550 graus Celsius em atmosferas de ar (Amostras AM-1) e em vácuo (Amostra AM-2). As amostras AM-1 e AM-2 foram caracterizadas pelas técnicas de MET, DRX, BET, XPS, EPR, Potencial Zeta, TG, como também foram testadas as propriedades fotocataliticas para o gás inorgânico NO e o corante orgânico têxtil Rodamina B. A amostra AM-1 foi imobilizada em suportes de vidro de soda-cal por meio das técnicas de impregnação, fazendo uso de uma solução contendo o precursor em etanol e imersão através da solução feita com PVA em água. Os revestimentos também foram caracterizados pelas técnicas de MET, DRX, MEV-FEG, UV-Vis, Ângulo de contato, testes de aderência, qualitativo e quantitativo de acordo com a norma ASTM D3359 - 09, além das suas propriedades fotocatalíticas terem sido testadas para o gás NO e o corante Rodamina B. A caraterização das amostras AM-1 e AM-2 conferiu a formação do anatásio nanométrico nas condições de síntese empregadas. A amostra AM-1 exibe uma excepcional atividade fotocatalítica para a degradação do gás NO em relação às amostras AM-2 e especialmente ao padrão fotocatalítico internacional, P-25 (Degussa). Foi possível imobilizar o nanopó AM-1em substratos de vidro de soda-cal em condições de tratamento térmico em atmosfera de ar, obtendo-se revestimentos de ótima aderência, alta uniformidade, porosidade e elevada super-hidrofilicidade. / [en] In the present work the synthesis of nanometric anatase was carried out from a low cost commercial precursor, which passes through an intermediary stage of titanate nanotubes (TTNTs). After the alkaline hydrothermal synthesis, the TTNTs were thermal treated at 550 celsius in air atmosphere (AM-1 sample) and vacuum (AM-2 sample). AM-1 and AM-2 samples were characterized by TEM, XRD, BET, XPS, EPR, zeta potential and TGA as well as the photocatalytic degradation of NO gas and Rhodamine B organic textile dye were studied. AM-1 sample was immobilized onto soda-lime glass substrates by impregnation and immersion techniques using solutions of PVA-ethanol and PVA-water, respectively. The coatings were also characterized by TEM, XRD, SEM-FEG, UV-Vis spectroscopy, contact angle measurements and both qualitative and quantitative adherence tests based on ASTM D3359-09. Furthermore, the catalytic properties of the coatings were evaluated for NO and Rhodamine B dye degradation. The characterization of AM-1 and AM-2 samples confirmed the formation of nanometric anatase under the synthesis conditions used in this work. The AM-1 sample showed an exceptional photocatalytic activity for the NO degradation when compared with AM-2 sample and especially with the international photocatalytic standard: Degussa P-25. AM-1 nanopowder were immobilized on soda-lime glass substrates by the thermal treatment performed in an air atmosphere leading to the formation of coatings with excellent adherence, homogeneity, porosity and super-hydrophilicity.

Excessive CO2 emissions can negatively impact society and our planet. Reduction of CO2 is one potential avenue for its abatement. One of the most significant challenges to reducing CO2 is its extremely stable linear form. Experimentally, Cu/TiO2 has shown promise for CO2 photocatalytic reduction. Dispersed atomic catalysts can achieve high catalytic efficiency on a per atom basis. Active sites also typically having lower coordination number, and therefore may be more reactive. Using density functional theory and experimental techniques, we have investigated the role of surface oxygen vacancies (Ov) and photoexcited electrons on supported single atom catalysts and CO2 reduction. Cu atoms with Ov have shown to aid in the process of bent, anionic CO2 formation. In the first step involving CO2 dissociation (CO2* --> CO* + O*), a single Cu atom in Ov lowered the activation barrier to 0.10 - 0.19 eV, which could enable fast reduction of CO2 even at room temperature, in agreement with experimental findings. A photoexcited electron model was shown to readily promote Cu binding to the surface vacancy, and CO2 adsorption and direct dissociation. Finally, we briefly compare our results to calculations of supported single Pt atoms to determine how metals besides Cu may behave as photocatalysts for CO2 reduction, and we found a single Pt with Ov can promote CO2 dissociation. Our results show that tailoring TiO2 surfaces with defects in conjunction with atomic catalysts may lead to useful catalysts in the photoreduction of CO2.

Parmi les différents systèmes de stockage d’énergie électrique étudiés depuis plus de 2 siècles, le stockage électrochimique de type batterie Li-Ion est vraisemblablement le plus pertinent et le plus efficace. Des verrous demeurent cependant pour avoir des batteries Li-Ion répondants aux besoins actuels, et une des limitations provient des matériaux d’électrodes. Le silicium est un candidat de choix pour répondre aux problématiques batteries posées, cependant sa tenue au cyclage est courte et les méthodes de synthèse sont souvent très contraignantes. Associant deux laboratoires de recherche acteurs majeurs dans le domaines des nanosciences (le LRN à l’URCA) et des matériaux et batteries (le LRCS à l’UPJV) le projet pluridisciplinaire NanoSiBL d’une durée de 36 mois se fixe pour objectif d’apporter des solutions aux deux points précédents par : 1, la réalisation d’électrodes négatives en Silicium par une voie de synthèse bas coût originale et innovante développée au LRN (l’électrodépôt en milieu liquide ionique), 2 un accroissement de la durée de vie de l’électrode grâce à deux types de structuration (soit une électrode constituée de nanofils/nanotubes de Si monolithique soit une électrode nanostructurée composite de Si/TiO2). L’expertise dans le domaine des batteries du LRCS devrait permettre sur ce deuxième point de déterminer la géométrie et configuration idéale de l’électrode en termes de performance. Basé des méthodes d’élaboration par électrochimie bas coût et originale, NanoSiBL a pour objectif, grâce au partage de compétences et de technologie entre physiciens et chimistes impliqués, d’initier une nouvelle thématique inter-établissement axée sur la valorisation de nanostructures de silicium et silicium composite nanostructuré. L’intérêt scientifique de ce projet réside dans la mise en œuvre et le contrôle des propriétés intrinsèques de ces nanostructures à base de silicium pour la réalisation d’électrodes négatives performantes de batterie Li-Ion. Dans la littérature, les électrodes négatives à base silicium ou silicium composite (type Si/TiO2) ont déjà démontré une amélioration par rapport aux électrodes de silicium massif. Néanmoins, le passage à des dispositifs opérationnels reste peu fréquent car les voies permettant de contenir l’expansion en volume du silicium restent à éprouver et car les méthodes utilisées pour élaborer ces nanofils de silicium (Chemical Vapor Deposition, évaporation réactive…) restent très contraignantes, tant au niveau des conditions de croissance (nécessité d’utiliser des précurseurs métalliques et des gaz très toxiques) que des coûts de fabrication (travail sous ultra-vide, nombreuses étapes pour la réalisation des dispositifs avec la nécessité de réaliser des contacts post-croissance…). NanoSiBL propose donc une alternative en réelle rupture technologique avec les méthodes de synthèse actuelles. Les techniques de croissance (électrodépôt en liquide ionique) et de nanostructuration (au sein de membranes polycarbonates ou nanotubes de TiO2) utilisées dans le projet permettront la mise au point d’électrodes à bas coût performantes pour l’application batterie Li-Ion visée. En outre la variété conséquente de géométries possibles proposées par les membranes nanoporeuses qui seront utilisées dans le projet (polycarbonate ou nanotubes de TiO2) permettra d’établir un comparatif essentiel de l’impact de la nanostructuration ou encore de la composition des électrodes pour contenir l’expansion en volume du silicium lors du cyclage et ainsi améliorer la durée de vie de telles électrodes (batterie). / Among the various electric energy storage systems studied for more than two centuries, the electrochemical storage battery type Li-Ion is probably the most relevant and most effective. however locks remain for Li-Ion batteries respondents to current needs, and limitations comes from the electrode materials. Silicon is a prime candidate to meet the challenges posed batteries, however its resistance to cycling is short and synthesis methods are often very restrictive. Combining two research laboratories major players in the fields of nanoscience (the LRN to URCA) and materials and batteries (the LRCS to UPJV) the multidisciplinary project NanoSiBL a period of 36 months set the objective of provide solutions to the above two points: 1, the realization of negative electrodes in silicon by a synthetic route down original and innovative cost developed LRN (electrodeposition in ionic liquid medium), 2 increased lifetime of the electrode through two types of structuring (or one electrode made of nanowires / nanotubes Si monolithic or a composite nanostructured electrode Si / TiO2). The expertise in the field of LRCS of batteries should allow this second point to determine the geometry and ideal configuration of the electrode in terms of performance. Based methods developed by electrochemistry low cost and original NanoSiBL aims, through the sharing of expertise and technology between physicists and chemists involved, to initiate an inter-establishment new theme focused on valuation and silicon nanostructures composite nanostructured silicon. The scientific interest of this project lies in the implementation and control of the intrinsic properties of these nanostructures based on silicon for making efficient negative electrodes of Li-Ion battery. In the literature, the negative electrodes based on silicon or silicon composite (type Si / TiO2) have already demonstrated improvement compared to bulk silicon electrodes. However, the transition to operational devices remains uncommon for ways to contain the expansion in volume of the silicon are experiencing and because the methods used to develop these silicon nanowires (chemical vapor deposition, reactive evaporation ...) remain very restrictive both in terms of growth conditions (the need to use metal precursors and highly toxic gases) that manufacturing costs (labor UHV, many steps for the realization of devices with the need for contacts post- growth…). NanoSiBL proposes an alternative in real technological break with the current methods of synthesis. growth techniques (electrodeposition in ionic liquid) and nanostructuring (in polycarbonates or TiO2 nanotube membranes) used in the project will enable the development of electrodes at low cost efficient for application referred Li-Ion battery. Furthermore the consequent variety of possible geometries offered by the nanoporous membranes to be used in the project (polycarbonate or TiO2 nanotubes) will establish a critical comparison of the impact of the nanostructure or composition of electrodes to contain expansion by volume of the silicon during the cycling and improve the life of such electrodes (battery).

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