Dans la problématique de l'utilisation de nouvelles énergies non polluantes, l'hydrogène est l'un des principaux carburants verts du futur. Les dérivés d'hydrazine et de borane sont potentiellement intéressants pour le stockage chimique de l'hydrogène. Les complexes entre hydrazines ou nitriles avec des boranes ou des alanes sont à la base de cette étude. Ces composés ont été synthétisés afin d'étudier leur structure électronique avant et après la création de la liaison entre les acides et les bases de Lewis. La spectroscopie photoélectronique à rayonnement UV (UV-SPE) est utilisée comme outil principal de caractérisation fournissant des énergies d'ionisation (IE). L’interprétation des résultats expérimentaux est supportée par des calculs quantiques comme ΔSCF + TD-DFT, OVGF, P3 et SAC-CI. Des simulations et des expériences par Flash Vacuum Thermolysis (FVT) ont été effectuées, portant sur l’élimination d'hydrogène à partir de dérivés d'hydrazine borane. / Within the problematic of the use of new non-polluting energies, hydrogen is one of the main green fuels of the future. Hydrazine borane derivatives are potentially interesting chemical hydrogen storage materials. Complexes between hydrazines or nitriles with boranes or alanes are the basis of this study. These compounds were synthesized in order to study their electronic structure before and after creation of the bond between the Lewis acids and bases. Ultraviolet Photoelectron Spectroscopy (UV-PES) is used as a main characterization tool, providing Ionization Energies (IE). The interpretation of the experimental results is supported by Quantum Chemical Calculations as ΔSCF+TD-DFT, OVGF, P3 and SAC-CI methods. Simulations and experiments by Flash Vacuum Thermolysis (FVT) were carried out on hydrogen release from hydrazine borane derivatives.

Made available in DSpace on 2014-10-09T12:42:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:55Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

L’utilisation des combustibles fossiles est responsable de l’augmentation de la concentration en gaz à effet de serre dans l’atmosphère. Parmi les solutions de remplacement envisagées, l’hydrogène constitue un vecteur d’énergie très intéressant. Toutefois, cette solution ne sera envisageable que lorsque les problématiques liées à la production de l’hydrogène et à son stockage seront résolues.Le premier objectif de cette thèse porte sur la synthèse et la caractérisation de composés ternaires à base de magnésium dans le système ternaire TR-M-Mg (avec TR = Terres Rares et M = métaux de transition) qui pourraient être de bons candidats pour le stockage de l’hydrogène. Ces composés pourraient de plus avoir d’autres applications, notamment comme matériaux de structure, du fait de leur très faible densité. La composition NdNiMg15 a fait l’objet d’une étude complète. Cette phase cristallise selon une symétrie quadratique avec a= 10,0602(1) et c= 7,7612(2) Å et un groupe d’espace P4/nmm. Un ordre antiferromagnétique à 9 K est observé et la capacité massique de stockage réversible est de 4 %mass. Cette nouvelle phase a montré un effet durcissant sur le magnésium.Le deuxième objectif de cette thèse concerne la production d’hydrogène par hydrolyse i) des composés ternaires TR-M-Mg qui pourrait être considérée comme une possibilité économique et énergétique pour valoriser les déchets de ces composés et ii) des mélanges ternaires TR-M-Mg élaborés par broyage mécanique. Le broyage a permis la création des défauts favorisant ainsi la corrosion des métaux. De plus, la production d'hydrogène par hydrolyse des composites Mg-NdNiMg15 (70, 80 et 90 %mass. Mg) a été réalisée et comparée à celle du composé NdNiMg15 (64 %mass. en Mg). Le mécanisme de corrosion principal déduit des essais électrochimiques sur les composites est la corrosion galvanique. / The use of fossil fuels (non-renewable energy) is responsible for the increase of the concentration of greenhouse gases in the atmosphere. Among the considered alternatives, hydrogen is seen as the most attractive energy vector. Production and storage of hydrogen is one of the key challenges in developing the hydrogen economy.The first objective of this thesis deal with the synthesis and characterization of magnesium-based ternary compounds in the RE-TM-Mg ternary system (with RE = Rare Earth and TM = transition metals) which could be good candidates for hydrogen storage. These compounds could also have other applications than the hydrogen storage in the future such as light structured material. The NdNiMg15 compound has been the subject of a completed study. This phase crystallizes with a tetragonal symmetry (a= 10.0602(1) and c= 7.7612(2) Å and a space group P4/nmm). It showed an antiferromagnetic ordering at 9 K and a reversible hydrogen storage capacity of 4 %mass. This phase exhibited a hardening effect respect to magnesium compound.The second objective of this thesis concerns the hydrogen production by hydrolysis of i) RE-TM-Mg ternary compounds, which could be considered as an economic and energetic possibility to valorize the waste of these compounds and ii) RE-TM-Mg ternary mixtures prepared by ball milling. The grinding creates defects thus promoting the corrosion of the metals. In addition, the hydrogen production by hydrolysis of the Mg-NdNiMg15 composites (70, 80 and 90 %mass. Mg) was carried out and compared with that of the NdNiMg15 compound (64 %mass. Mg). The main corrosion mechanism determined from the electrochemical measurements of the composites is the galvanic corrosion.

Made available in DSpace on 2014-10-09T12:42:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:55Z (GMT). No. of bitstreams: 0 / O hidrogênio pode ser considerado um importante e promissor vetor energético, podendo ser utilizado para substituir os combustíveis fósseis no setor de transportes por meio de células a combustível. Existem muitos métodos de se produzir hidrogênio. Estes métodos incluem a reforma de gás metano, a eletrólise e processos termo químicos. Uma grande quantidade de energia é necessária para se produzir hidrogênio. Em muitos processos de produção de hidrogênio, a energia de entrada necessária é na forma de calor ou eletricidade. O objetivo deste trabalho é analisar a viabilidade da produção de hidrogênio eletrolítico, utilizando-se energia disponível do sistema interligado nacional da cidade de São Paulo. Para atingir este objetivo estudou-se o sistema elétrico brasileiro, a tecnologia de produção, armazenamento e transporte do hidrogênio, analisando-se os custos e a avaliação ambiental de cada item. Calculou-se as externalidades negativas da poluição ambiental causada pela frota de ônibus movidos a diesel e por meio das análises e estimativas mostrou-se a viabilidade de substituição dos ônibus a diesel por ônibus a hidrogênio e a consequente melhora na qualidade socioambiental da população da cidade de São Paulo. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Neste trabalho, avaliou-se inicialmente o efeito da substituição de elementos em ligas à base de LaMgAlMnCoNi do tipo AB5 com adição de estanho (Sn) e cobre (Cu) em substituição ao cobalto (Co), para utilização em ligas absorvedoras de hidrogênio e em eletrodos negativos de baterias de Ni-HM. Avaliou-se a influência desta substituição na microestrutura do material. Notou-se que o aumento da concentração de estanho promove a formação da fase LaNiSn nas ligas, bem como a diminuição das duas fases principais: LaNi5 e (La,Mg)Ni3. Adicionalmente, utilizou-se o refinamento de Rietveld para quantificar as fases em cada composição. Posteriormente, propôs-se um estudo da absorção de hidrogênio. Notou-se que a liga com cobalto apresentou a melhor capacidade de absorção de hidrogênio. Ademais, verificou-se o comportamento destas ligas na capacidade de descarga, estabilidade cíclica e na alta taxa de descarga de baterias de Ni-HM. A maior capacidade de descarga medida foi para a liga de cobalto, atingindo 337,1 mAh/g. Notou-se, posteriormente uma melhora na estabilidade cíclica das baterias com o aumento do teor de cobre. Além disso, observou-se que a alta taxa de descarga apresenta melhores valores com a adição de cobre na composição. Por fim, avaliou-se o efeito da susceptibilidade a corrosão. Notou-se que o estanho promove um aumento na resistência à corrosão das ligas em eletrólito alcalino. / In this work, it has firstly been evaluated the effect of tin (Sn) and copper (Cu) substituting cobalt (Co) in LaMgAlMnCoNi AB5-type alloys for use in hydrogen storage materials and negative electrodes of Ni-MH batteries. The influence of this substitution on the microstructure of these materials has been evaluated. It could be noted that increasing the tin concentration promotes the formation of LaNiSn phase and decrease of two main phases of these alloys: LaNi5 and (La,Mg)Ni3. Additionally, the Rietveld refinement has been evaluated to quantify phases in each composition. Subsequently, it has been proposed a study of the hydrogen absorption in these alloys. It could be observed that the cobalt alloy showed the best hydrogen absorption capacity. Moreover, the behavior of these alloys has been investigated in the discharge capacity, cyclic stability and high rate dischargeability of Ni-MH batteries. The highest discharge capacity has been measured for cobalt alloy, reaching 337.1 mAh/g. It has been noted, further improvement in the cyclic stability batteries with increasing copper content in the alloys. Furthermore, it has been observed that the high rate dischargeability has better values with the addition of copper in the composition. Finally, it has been evaluated the effect of susceptibility to corrosion. It has been noted that tin promotes an increase in corrosion resistance of the alloys in an alkaline electrolyte.

Neste trabalho investigou-se a obtenção do composto TiFe a partir da moagem de alta energia de misturas de pós de TiH2 e Fe, seguida de aquecimento sob vácuo para a reação de síntese. No lugar do Ti, o TiH2 foi escolhido como precursor em razão de sua fragilidade, benéfica para a diminuição da aderência dos pós ao ferramental de moagem. Foram preparados dois lotes de misturas obedecendo-se a relação Ti:Fe de 50:50 e 56:44. Ambos foram processados em um moinho do tipo planetário por tempos que variaram de 5 até 40 horas, sob atmosfera de argônio de elevada pureza. Em todos os experimentos foram mantidos constantes a velocidade de rotação do prato do moinho, a quantidade de amostra, o diâmetro e o número de bolas. As amostras moídas foram caracterizadas por calorimetria exploratória diferencial (DSC), termogravimetria (TG), microscopia eletrônica de varredura (MEV), difração de raios X (DRX) e fluorescência de raios X por dispersão de energia (EDXRF). Apenas TiH2 e Fe foram observados nas amostras moídas, com um grau crescente de mistura em função do tempo de moagem. O composto TiFe nanoestruturado (12,5 a 21,4nm) foi obtido de forma majoritária em todas as amostras após a reação de síntese promovida pelo tratamento térmico a 600ºC (873K). As amostras reagidas foram caracterizadas por microscopia eletrônica de transmissão (MET) e DRX. Um equipamento do tipo Sievert, operando sob um fluxo constante (modo dinâmico), foi utilizado para levantar as curvas termodinâmicas de absorção e dessorção de hidrogênio. Todas as amostras absorveram hidrogênio à temperatura ambiente (~298K) sem a necessidade de ciclos térmicos de ativação. Os melhores resultados foram obtidos com as amostras moídas por 25 e 40 horas, de composição não estequiométrica 56:44. Tais amostras absorveram e dessorveram hidrogênio à temperatura ambiente, sob os platôs de aproximadamente 6,4 e 2,2bar (~0,6 e 0,2MPa), respectivamente. A capacidade máxima de armazenamento foi de 1,06% em massa de hidrogênio (H:M~0,546), sob pressão de até 11bar (1,1MPa), com reversão de até 1,085% em massa de hidrogênio (H:M~0,559), sob pressão de até 1bar (0,1MPa). Estas amostras também apresentaram maior cinética de absorção e dessorção de hidrogênio com fluxos de 1,23 (25h) e 2,86cm3/g.min. (40h). Tais resultados são atribuídos à variação composicional da fase TiFe e à maior quantidade de TiH2 livre. / In this work high-energy ball milling from TiH2 and Fe powder mixtures, followed by post-heating under vacuum, were performed for the reaction synthesis of TiFe compound. TiH2 was used instead of Ti due to its brittleness, preventing strong particles adhesion to the grinding balls and vial walls. Two mixtures batches were prepared following Ti:Fe ratios of 50:50 and 56:44. Both of them were dry-milled in a planetary mill for times ranging from 5 to 40 hours, under high purity argon atmosphere. The speed of main disk rotation, the amount of sample, number and diameter of the balls were kept constant in all experiments. As-milled samples were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray fluorescence (EDXRF). As-milled materials presented only Fe and TiH2 phases showing increased mixture degree with the milling time. After heat treatment at 600ºC (873K), nanostructured TiFe compound (12.5 to 21.4nm) was mostly formed in all samples. Reacted samples were characterized by transmission electron microscopy (TEM) and XRD. Hydrogen absorption and desorption thermodynamics curves were determined in a Sievert-type apparatus operating at constant flow (dynamic mode). All samples absorbed hydrogen at room temperature (~298K) requiring no thermal activation cycles. Best results were seen on samples milled at 25 and 40 hours, with non-stoichiometric composition 56:44. Those samples absorbed and desorbed hydrogen at plateaus of 6.4 and 2.2bar (~0.6 and 0.2MPa), respectively. Maximum hydrogen storage capacity was 1.06 wt% (H:M~0,546) at 11bar (1.1MPa), with reversion of 1.085 wt% (H:M~0,559) at 1bar (0.1MPa). Higher hydrogen absorption and desorption kinetics were observed in those samples, as well, with flows of 1.23 (25h) and 2.86cm3/g.min. (40h). Such results were assigned to the compositional variation of TiFe phase and to the largest amount of free TiH2.

La demande en énergie ne cesse d'augmenter et elle satisfaite essentiellement par les énergies fossiles qui présentent une contrainte environnementale vue ses émissions de gaz à effet de serre. Considéré comme vecteur énergétique, l'hydrogène possède l'immense avantage de ne pas émettre de gaz à effet de serre et notamment du CO2. Son stockage dans des intermétalliques permet d’obtenir des capacités massiques et volumiques supérieures à celles obtenues en voie liquide ou sous pression. Dans ce travail, nous avons élaboré le composé intermétallique quaternaire LaCaMgNi9 par mécanosynthèse et ce selon différents schémas réactionnels. Ce procédés de synthèse est employé pour la première fois, pour la synthèse de cet intermétallique, afin de s'affranchir des difficultés que présentent les autres techniques de synthèse (co-fusion, frittage). Les caractérisations structurales et morphologiques des alliages obtenus ont été réalisées afin de tester leurs performances en tant que matériaux pour électrode négative d’accumulateur Ni-MH par divers techniques de caractérisation électrochimiques et solide-gaz / The increasing energy demand is mainly supplied by fossil sources which had environmental drawback essentially greenhouse gas emission. Considered as an energy carrier, hydrogen has the huge advantage to be clean. Its storage in intermetallic compound leads too higher hydration capacities than liquid and compressed storage. In this work, LaCaMgNi9 quaternary type alloy has been synthesized, for the first time, by mechanical alloying in order to avoid the inherent difficulties of the fusion technique. The structural and morphological characterization of the obtained alloys were performed. Their hydrogen related properties were examined (solid-gas and electrochemical reactions) in order to study their performance as negative electrode material in Ni-MH batteries

Les batteries Ni-MH sont utilisées dans diverses applications, aussi bien stationnaires (panneaux solaires) que mobiles (véhicules hybrides). La matière active des électrodes négatives des batteries actuellement commercialisées est un alliage intermétallique de type AB5 (A = terres rares, B = métaux de transition). La demande croissante en énergie nécessite d'améliorer la capacité massique de ces accumulateurs. Pour cette raison, nous étudions de nouveaux matériaux d'électrode de type ABy (y = 3,5 ou 3,8). La structure d'empilement particulière de ces alliages composés d'unités [AB5] et [A2B4] leur confère une capacité plus importante. L'unité [A2B4] est en effet capable d'absorber davantage d'hydrogène que l'unité [AB5]. Cependant, sa stabilité au cyclage lui fait défaut. Dans cette thèse nous avons, dans un premier temps, mené une étude sur les composés binaires de type ANi3,5 et ANi3,8 (A Æ Gd, Sm ou Y) puis nous avons étudié l'évolution des propriétés thermodynamiques, électrochimiques et de corrosion et après substitutions successives de la terre rare (ou yttrium) par du magnésium puis du lanthane / Ni-MH batteries are used in both stationary (solar panels) and mobile (hybrid vehicles) applications. The active material of negative electrodes currently on the market is an AB5-type alloy (A = rare earth, B = transition metal). The continuously increasing demand for energy requires improving the mass capacity of these batteries. For this reason, we study new type of electrode materials ABy (y Æ 3.5 or 3.8). The particular stacking structure of these alloys composed of [AB5] and [A2B4] units give them more capacity. Indeed, [A2B4] unit is able to absorb more hydrogen than [AB5] unit. However, stability in cycling is lowered. In this phD work we have, at first, conducted a study of binary compounds type ANi 3.5 and ANi3.8 (A = Gd, Sm ou Y), then we studied the evolution of the thermodynamic properties, electrochemical and corrosion after successive substitutions of the rare earth (or yttrium) with magnesium and lanthanum

Depuis une quinzaine d’années, les matériaux poreux de type Metal Organic Frameworks (MOFs) offrent de nouvelles perspectives dans le cadre du stockage d’hydrogène par adsorption. Ces matériaux possèdent une structure et un réseau de pores particulièrement bien adaptés à l’adsorption des gaz. Ainsi, le téréphtalate de Chrome (III) (MIL-101(Cr)), composé chimiquement très stable, possède une grande capacité de stockage de l’hydrogène, du dioxyde de carbone et du méthane. Afin de renforcer sa capacité de stockage d’hydrogène, un dopage au charbon actif (AC) du matériau a été envisagé. Les synthèses des matériaux dopés et non-dopés ont été réalisées et, pour cela, différents agents minéralisants (acide fluorhydrique, acide acétique et acétate de sodium) ont été testés. Les matériaux synthétisés furent caractérisés par diffraction des rayons X (DRX), par microscopie électronique à balayage (MEB), par analyses thermogravimétriques (ATG) et par adsorption d’azote à 77K. Les capacités de stockage d’hydrogène de ces matériaux à 77 K et 100 bar ont été évaluées par mesures des isothermes d’adsorption d’hydrogène, réalisées par méthodes volumétrique et gravimétrique. Les résultats obtenus par ces deux méthodes sont en parfait accord et le matériau composite affiche une capacité d’adsorption de 13.5 wt%, qui est supérieure à celle du matériau non dopé (8.2 wt% dans les même conditions expérimentales). Les cinétiques d’adsorption ont été mesurées à 77 K par méthode volumétrique. Les résultats obtenus ont été comparés au modèle de la force motrice linéaire, Linear Driving Force (LDF). Un modèle de diffusion dépendant de la température a été développé afin de tenir compte des variations de températures qui se produisent durant le processus d’adsorption. / Since the last 15 years, the porous solids such as Metal-Organic Frameworks (MOFs) have opened new perspectives for the development of adsorbents for hydrogen storage. The structure and the pore networks of these materials are especially adapted to the adsorption of gases. The chromium (III) terephthalate-based MIL-101(Cr) is a very stable material which exhibits good adsorption uptakes for hydrogen (H2), carbon dioxide (CO2) and methane (CH4).In this study, syntheses were carried out by different ways and several mineralizing agents such as hydrofluoric acid (HF), acetic acid (CH3COOH) and sodium acetate (CH3COONa) have been tested. Moreover, Activated Carbon (AC) has been introduced in the framework to create an AC incorporated composite material with an enhanced specific surface area. Conventional techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and nitrogen (N2) adsorption isotherms at 77 K were used for materials characterizations.In the aim to evaluate hydrogen storage capacities of these materials, hydrogen adsorption isotherms were measured at 77 K via both volumetric and gravimetric methods, and the obtained results are in good agreement. A hydrogen uptake value of 13.5 wt% has been measured at 77 K and 100 bar for the composite material which shows a great improvement of hydrogen capacity compared to the pristine MIL-101(Cr) (8.2 wt%).Finally, hydrogen adsorption kinetics has been measured at 77 K using volumetric method. The obtained results were compared to the Linear Driving Force (LDF) and a temperature dependent diffusion model was also considered to take into account the temperature variations which occur during the adsorption process.

Nanoporous metal represents a particular form of a metal, which combines the characteristics of metals, such as good thermal and electrical conductivity, catalytic activity with the materials properties characteristic of nanoporosity, which include high surface area, low density, large number of pores, etc. Nanoporous metals have applications in various fields such as catalysis, hydrogen storage, electrochemical sensing, membranes, SERS, and supercapacitors. The three dimensional porous structures offer high specific surface area and large pore volumes, which enhance substrate diffusion within the porous structures and provide a large number of surface active sites for catalytic applications. However, synthesis of nanoporous metal based on conventional approach (template assisted synthesis and dealloying) suffers from scalability issue, specific for few metals, additional synthetic steps etc. Challenges still remain in this field to fabricate three dimensional porous metals where pores are interconnected (bicontinuous). Recently, development of the synthesis of nanoporous metal got a thrust by the advent of the concept of assembly of nanoparticles in either an ex-situ or in an in-situ manner. Objectives 1. Establish the synthetic strategy of metal nanosponge formation by capping agent dissolution method (ex-situ assembly) 2. Explore the catalytic activity of these metal nanosponges towards 4-nitrophenol reduction and alkene hydrogenation reactions 3. Elucidate the mechanism of formation of metal nanosponge in solution state (kinetic in-situ assembly of nanoparticles) using ammonia borane as a reducing agent in water under different conditions 4. Investigate the hydrogen storage properties and catalytic arene hydrogenation activities of metal nanosponges 5. Synthesis of bismuth oxide nanosponge using bismuth nanosponge as a template. Study of the photocatalytic dye degradation behavior using bismuth oxide nanosponge under visible light irradiation Significant results Synthesis of metal nanosponges was carried out using capping agent dissolution method wherein addition of water to M@BNHx polymer gives metal nanosponges. The B-H bond of BNHx polymer is unstable in the presence of water and gets hydrolyzed to give hydrogen gas bubbles which act as dynamic templates for the formation of metal nanosponges. The pristine nature of the surface of these metal nanosponges was elucidated by several analytical techniques. The catalytic activity of these metal nanosponges (Ag, Au, Pd, Pt, and Cu) was demonstrated using 4-nitrophenol reduction reaction in the presence of sodium borohydride as a reducing agent. Iridium nanosponge was obtained by capping agent dissolution method from Ir@BNHx polymer. Mesoporous high surface area iridium nanosponge was found to be an active catalyst for alkene hydrogenation reaction, whereas Ir@BNHx polymer does not exhibit any catalytic activity under similar reaction conditions. The effects of temperature, solvent, substrate to catalyst ratio, and pressure on catalyst activity were established using styrene as a substrate. The thermal stability (up to 300 oC) and robustness over several cycles were demonstrated for the iridium nanosponge. Several alkenes (linear alkene, cycloalkane, and conjugated alkene) were successfully hydrogenated using iridium nanosponge at room temperature and 4 bar hydrogen pressure. Generality of the synthetic procedure was explored by using different iridium precursors which gave iridium nanosponges exhibiting similar catalytic activity. Silver, gold, palladium, platinum, and copper nanosponges have been synthesized by chemical reduction method (in-situ kinetic assembly of nanoparticles) using ammonia borane as a reducing agent in water as a solvent. The effect of variables (metal salt to amine borane ratio, concentration of the reactants, solvent, temperature, and reducing agent) were thoroughly investigated using the silver system as a model. In the absence of a capping agent, metal salt reduction was carried out using amine borane which forms nanoparticles. In a high dielectric solvent, the colloidal particles attach together to form agglomerates. During the course of the reaction, hydrogen gas bubbles were generated which produce pores within the agglomerates leading to the formation of three dimensional nanosponge structures. Finally, the hydrogen storage properties (pressure composition isotherm and sorption kinetics) of these metal nanosponges were investigated under different conditions. These metal nanosponges exhibit reasonable, reversible storage characteristics: Ag (3 wt%), Pd (5.5 wt%), Pt (6 wt%), and Cu (2.5 wt%). Phase selective ruthenium nanosponge was synthesized using chemical reduction method. It was found that amine borane as a reducing agent for certain ruthenium precursors results in the hcp phase of ruthenium whereas, reduction using sodium borohydride affords fcc phase of ruthenium. Hcp and fcc phases of ruthenium were established using electron and X-ray diffraction methods. Surface characterization technique showed the pristine nature of ruthenium nanosponge. Both hcp and fcc ruthenium nanosponges were employed as catalysts for hydrogenation of benzene; it was found that hcp ruthenium is more active than fcc ruthenium for benzene hydrogenation to cyclohexane. Substrate to catalyst ratio, temperature, hydrogen pressure, and solvent effect were thoroughly investigated using benzene as a model substrate. It was found that hcp ruthenium nanosponge is capable of hydrogenating a variety of alkyl substituted benzenes under ambient conditions. The catalyst was found to be active over several cycles without any loss in its activity. Phosphine was used as a catalyst poison and hot filtration test was performed separately to show the true heterogeneous nature of the active catalyst. Hydrogen storage experiments were performed to understand the interaction of hydrogen with different phases of ruthenium. Bismuth nanosponge was synthesized using chemical reduction method. Synthesis of different polymorphs of bismuth oxide nanosponges (tetragonal, monoclinic and body centered cubic) were carried out by calcination of bismuth nanosponge at different temperature (300 oC, 500 oC, and 800 oC). The phase purity of bismuth oxide nanosponges were established using X-ray and electron diffraction method. It was found that surface area decreases with increasing the calcination temperature. Tetragonal bismuth oxide (300 oC annealed sample) nanosponge shows the highest photocatalytic activity as compared to other polymorphs. Mechanistic investigation suggests that hole and hydroxyl radical are responsible for dye degradation. Recyclability study demonstrated the formation of bismuth oxycarbonate which leads to a drop in catalytic activity. However, the tetragonal phase of bismuth oxide with high catalytic activity could be regenerated upon annealing at 300 oC for 3 h.