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Instead of the conventional carbon supports for Pt, the use of supports like carbon nanotubes and carbon nanotubes containing nitrogen has been shown to give rise better activity and stability for methanol oxidation. The anchoring sites (namely the hetero atoms) disperse the Pt crystallites and also contribute to alteration of the onset potential for methanol oxidation. � 2008 Elsevier B.V. All rights reserved.

Vapor phase hydrogenation of nitrobenzene is reported on 1 wt.% Pd supported on hydrotalcite, MgO and ?-Al2O3 catalysts. The catalysts were prepared in the laboratory using a wet impregnation method and were characterized by XRD, BET surface area, TPR, TEM, XPS and CO chemisorption studies. The conversion of nitrobenzene was studied in the temperature region of 498-573 K and compared on all the catalysts. An impressive catalytic performance of nitrobenzene conversion was observed on hydrotalcite supported Pd catalyst. CO chemisorption and TEM results prove that palladium disperses better on hydrotalcite supports when compared with other conventional supports such as MgO and ?-Al2O3, which is responsible for the high conversion of nitrobenzene. � 2008 Elsevier B.V. All rights reserved.

A metal oxygen molecular cluster compound has been utilized for the preparation of organic-inorganic nanocomposite film by a sol-gel method. The entrapment of these cluster compounds in a composite film has been characterized by various physico-chemical techniques. The entrapped metal oxygen cluster stabilizes its energy levels, which is evidenced from the change in redox potential and band gap. The rectification phenomenon of composite films is attributed to the embedded cluster compounds. The rectification behaviour of the composite film, which is due to the charge transfer from molecular cluster and the electrode, has been studied. � 2008 Elsevier B.V. All rights reserved.

The proton conductivity of perfluorinated ionomer membrane used in a proton exchange membrane fuel cell (PEMFC) depends largely on the extent of hydration state of the membrane. Sufficient membrane hydration is achieved typically through the humidification of gases prior to feeding them into the fuel cell. Further, hydrogen humidification is known to have a larger impact on the performance of a PEMFC than the oxygen humidification. Bubble humidification has been a widely used method to externally humidify hydrogen. However, to-date a continuous bubble humidification system, which is essential to the continuous operation of the PEMFC system, has not been implemented. The main contributions of this work are (i) a design for continuous humidification of hydrogen for the PEMFC system and (ii) a method to maintain the RH of hydrogen between 93 and 95% (at desired temperature) over a wide range of gas flow rates. One of the key advantages of the proposed design is the flexibility of using recirculated stack coolant water to increase the energy efficiency of the PEMFC system. The design is first tested off-line and then online with a 1 kW stack. Results obtained from both the off-line and online tests indicate that the design successfully meets the demands of an online operation. It is observed that with the use of the proposed humidification scheme, the stack efficiency in terms of power output increases by about 6-19% of the power obtained under dry hydrogen conditions. � 2008 International Association for Hydrogen Energy.

The storage of hydrogen in carbon nanotubes requires appropriate chemical activators in suitable geometry. In this study, the role of boron substitution in carbon nanotubes is demonstrated for activation and storage of hydrogen. � 2007 International Association for Hydrogen Energy.

Carbon nanofibres (CNFs) were prepared by catalytic decomposition of gaseous ethylene on NiCu/H-ZSM-5. They were characterized by XRD and TEM techniques. Dehydrogenation characteristics of LiAlH4 admixed with CNFs and Vulcan XC72R were studied and compared with that of pure lithium aluminium hydride. The results show that CNFs have prominent effect on the dehydrogenation properties of LiAlH4. On the basis of the dehydrogenation characteristics, a possible mechanism for the dehydriding of LiAlH4 upon addition of carbon materials has been considered.

A reverse microemulsion procedure has been adopted for the preparation of 20 wt % RuxSey/C (where x = 1 and y = 0- 1). This system has been examined for electrochemical oxygen reduction activity. The measured oxygen reduction activity was comparable with that of commercial Pt/C (E-TEK). The activity is due to stabilization of Ru active sites by Se against blocking as a result of (hydr)oxide formation. � 2007 American Chemical Society.

Polycrystalline gold nanowires were synthesized by a simple chemical reduction method using potassium oxalate as the reducing and capping agent along with polyvinylpyrrolidone (PVP) as the co-capping agent at room temperature. Different molar concentration ratios of HAuCl4 and potassium oxalate were studied for the synthesis of Au nanowires. Kinetics studies for Au colloid formation were carried out using UV-vis spectroscopic technique for the various concentration ratios of the reactants. As the concentration of oxalate was increased, the rate of reduction as well as particle growth was found to increase. XRD and TEM analyses revealed the formation of polycrystalline Au nanowires with a preferential growth of the {111} facet. In the absence of PVP, no Au colloid was formed. Studies revealed that the formation of the Au nanowire was due to the bridging nature of the oxalate dianion. The formation of Pt nanowires further supported the role of oxalate when the same method was adopted for the synthesis of Pt nanowires without using PVP. A plausible mechanism was proposed for the formation of Au nanowires explaining the role of oxalate. � 2007 American Chemical Society.

Template assisted synthesis of boron substituted carbon nanotubes was carried out by the carbonization of hydroborane polymer in alumina membrane template. The nanotubes were characterized by electron microscopic analysis, FT-Raman, FT-IR, XRD, X-ray photoelectron spectroscopy (XPS) and 13C & 11B MAS NMR techniques. The presence of boron in different chemical environment has been visualized by XPS and 11B MAS NMR. The hydrogen absorption activity has been studied and a maximum of 2 wt% hydrogen storage capacity was observed. � 2007 Elsevier Ltd. All rights reserved.

Nitrogen doped spherical TiO2 has been prepared by thermal decomposition of Ti-melamine complex in air atmosphere. A clear shift in the onset light absorption from UV region (520 nm) has been observed for the N-doped samples. It has been deduced from the optical absorption spectra that the higher calcination temperature results in the decrease in the amount of N-doping. The XRD results revealed the phase transition of TiO2 from anatase to rutile crystalline phase, starting at calcination temperature ?600 �C. The electron microscopic images reveal the formation of spherical and flakes of TiO2 nanocrystals (25 nm). The chemical nature of N in the N-TiO2 has been evolved through X-ray photoelectron spectroscopy. The presence of different types of N species have been observed corresponding to different oxidation states and the presence of Ti-N and O-Ti-N have been confirmed from the observed binding energy values. Photocatalytic decomposition of methylene blue has been carried out both in the visible region and UV + visible region. In the visible region, N-TiO2 showed higher activity compared to the undoped commercial TiO2 (Degussa P25). � 2007 Elsevier B.V. All rights reserved.

Monoclinic hydromagnesite (Mg5(CO3) 4�(OH)2�4H2O) flower-like structures of 2-3 ?m diameter have been synthesized at room temperature by a simple precipitation method without using any template, catalyst, or surfactant. The as-synthesized flowers were further calcined at various temperatures to prepare monodispersed, nanofibrous MgO microtubes of aspect ratio ?15. Both the precursor flowers and the MgO microtubes formed were characterized by powder XRD, TG-DTA, FT-IR, SEM, EDAX, HR-TEM, SAED, BET analysis and photoluminescence (PL) studies. A plausible mechanism for the formation of cubic MgO microtubes from monoclinic hydromagnesite flowers is proposed. The as-synthesized nanofibrous MgO microtubes have shown intense green and red emission. The more defective MgO microtubes formed in N2 atmosphere at 400�C showed the highest PL intensity and surface area. An attempt has been made to correlate the lattice parameter and the PL intensity. � 2007 American Chemical Society.

N -doped anatase TiO 2 has been prepared by thermal decomposition of Ti containing metal complexes. The light absorption onset has been shifted to the visible region by ~ 100 nm when compared to pure TiO 2. The N environment of N -doped TiO 2 has been studied by XPS and the results confirm the presence of N – Ti – O in the N -doped samples. Also, there is a shift in the binding energy values of Ti 2p3/2, and the additional peak for O 1s in N -doped TiO 2 confirms the increase in the covalent nature of TiO 2 during the N -doping. The photocatalytic activity of N -doped TiO 2 has been studied both in the UV and visible regions and N -doped TiO 2 shows higher activity than the Degussa TiO 2 in the visible region.

Layered perovskite type Sr3Ti2O7 catalysts, doped with N, S and Fe have been prepared by modified polymer complex method, characterized and evaluated for photo reduction of CO2 in aqueous alkaline medium using UV-visible radiation. EDXA and XRD data reveal the incorporation of the dopants into the titanate matrix. The presence of N in substitutional and interstitial locations, S as S6+ and Fe as Fe3+ species are indicated by XPS analysis. DRS and photo luminescence studies show that the dopants form additional energy levels within the band gap, promoting visible light absorption and retarding recombination of the charge carriers. Morphological changes and smaller crystallites also minimize recombination. Layered structure of Sr3Ti2O7 facilitates easy transport of charge carriers and separation of oxidation/reduction reaction centres. Structural, morphological and photo physical characteristics of doped catalysts improve the activity significantly. Sr3Ti2O7 co-doped with N, S and Fe together, displays maximum apparent quantum yield for CO2 reduction products. This journal is � The Royal Society of Chemistry.

The product distribution of electrochemical reduction of CO 2 can be altered by modifying the surface of pure copper by deposition. In this study, chronoamperometric deposition of Cu on Cu (Cu/Cu) was carried out at two different CuSO 4 bath concentrations, 0.25 M (high) and 0.025 M (low), termed as Cu/Cu-H and Cu/Cu-L respectively. These deposits were characterized by X-ray diffraction and they vary in their crystal orientation. Pure Cu and Cu/Cu were aligned towards (1 1 1) and (2 2 0) plane with a texture coefficient of 1.2 and 1.7, respectively. Electrodeposited electrodes were tested for the electrochemical reduction of CO 2 in KCl electrolyte and the results were compared with that of pure Cu electrode. Electrochemical reduction of CO 2 showed methane and ethane, with hydrogen as the byproduct. The product distribution varied with the crystal orientation of Cu electrodes. The maximum Faradaic efficiency of methane was 26% obtained on pure Cu electrode with (1 1 1) and (2 0 0) orientation, whereas Cu/Cu-L with dominating (2 2 0) orientation showed a maximum formation of ethane with Faradaic efficiency of 43%. A possible mechanism of product formation on Cu towards C 1 and Cu/Cu towards C 2 is also discussed.

The fabrication and properties of a hybrid membrane based on cesium salt of heteropoly acid, zirconium phosphate and polyvinyl alcohol are described. The fabricated membranes were characterized for their intra molecular interaction, thermal stability, surface morphology, water content and surface-charge properties using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water uptake and ion-exchange capacity measurements. These membranes showed reduced methanol crossover (for possible application in DMFC) relative to that of Nafion� 115. At 50% of relative humidity, the protonic conductivity of the hybrid membranes was in the range of 10-3 to 10-2 S cm-1. The feasibility of these hybrid membranes as proton conducting electrolyte in direct methanol fuel cell (DMFC) was investigated and preliminary results are compared with that of Nafion� 115. A maximum power density of 6 mW cm-2 with PVA-ZrP-Cs2STA hybrid membrane was obtained with the cell operated in passive mode at 373 K and atmospheric pressure. Open circuit voltage of the cell operated with hybrid membranes are high compared to that of Nafion� 115 indicating reduced methanol crossover. � 2006 Elsevier B.V. All rights reserved.

Carbon materials should have specific centers for hydrogen adsorption/absorption. The Universal Force Field and Density Functional Theory have been used to find the role of heteroatom substitution in carbon nanotubes as an activator. The effect of various heteroatoms like nitrogen, phosphorus, sulphur and boron for hydrogen activation and their geometrical positions has been identified for easy hydrogenation. This will be one of the possible centers where hydrogen adsorption/absorption is initiated. � 2006 Elsevier Ltd. All rights reserved.

TiO2 nanotubes have been synthesized using anodic alumina membrane as template. Highly dispersed platinum nanoparticles have been supported on the TiO2 nanotube. The supported system has been characterized by electron microscopy and electrochemical analysis. SEM image shows that the nanotubes are well aligned and the TEM image shows that the Pt particles are uniformly distributed over the TiO2 nanotube support. A homogeneous structure in the composite nanomaterials is indicated by XRD analysis. The electrocatalytic activity of the platinum catalyst supported on TiO2 nanotubes for methanol oxidation is found to be better than that of the standard commercial E-TEK catalyst.

Zirconium doped manganese oxide OMS-2 materials have been synthesized. The synthesized zirconium doped manganese oxide OMS-2 materials have been characterized by XRD, TGA, BET and TEM techniques. All the materials showed the OMS-2 type (cryptomelane) X-ray diffraction patterns and the thermal stability and BET surface area of zirconium doped OMS-2 materials are improved compared to the parent manganese oxide (K-OMS-2) material. Transmission electron micrographs showed the rod like needle shaped morphology and zirconia dispersion on fibrous morphology of as-synthesized zirconium doped manganese oxide OMS-2 materials. As synthesized zirconium incorporated OMS-2 catalysts have been tested for the liquid phase oxidation of side chain aromatic compounds (ethylbenzene and benzyl alcohol) and cyclohexanol. Zr-K-OMS-2 (Cry) has shown high conversion for ethylbenzene and benzyl alcohol, whereas Zr-K-OMS-2 (Bir) has shown high activity for the conversion of cyclohexanol and good selectivity towards the formation of cyclohexanone. � 2006 Elsevier B.V. All rights reserved.

Organic-inorganic composites consisting of silicotungstic acid and poly(vinyl alcohol) were prepared by a sol-gel method. The advantage of this strategy is that it is to manipulate the desired properties such as thermal stability, conductivity. The silicotungstic acid present in the composite acts as acid catalyst to hydrolyze/condense the silica precursor that leads to isotropic composite. The composite is structurally characterized with various techniques such as IR, UV-vis, TGA, SEM, TEM and CV measurements. The proton conductivity of composites is measured using impedance spectroscopy. The conductivity is found to increase with increase in temperature. The activation energy for the proton migration in the composite film was calculated to be 10 kJ/mol. � 2005 Elsevier B.V. All rights reserved.

A novel reduction technique is developed for preparing a Pt/C system using organic-inorganic nanocomposite consisting of heteropolyanions. Transmission electron microscopic studies revealed the formation of anisotropic platinum nanocrystals. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to evaluate the electrochemical methanol oxidation over the prepared Pt/C electrode. The effects of supporting electrolyte and temperature on the electrochemical oxidation of methanol were studied. The obtained Pt/C catalysts were found to exhibit higher activity and stability for methanol oxidation in perchloric acid than in sulphuric acid medium. The activation energy for methanol oxidation was found to be 41 � 3 kJ mol-1, being lower than the reported value. The lower activation energy for methanol oxidation on Pt/C could be attributed to the presence of anisotropic platinum nanoparticles. The described method is simple and elegant and can also be applied to the preparation of other noble metal supported catalysts. ? 2005 Elsevier B.V. All rights reserved.

The evolution of microstructure and interfacial defects in β-quenched and thermally aged Zircaloy-2 is studied by positron annihilation, hardness and ultrasonic measurements. Defect-sensitive positron lifetime and S-parameter have shown an increase during isochronal aging treatment in the temperature range of 673-873 K, which indicates defect production as a consequence of intermetallic phase formation. Hardness measurements have revealed an increase beyond 473 K, a plateau between 673 and 873 K. At 973 K, the hardness value falls slightly below that of quenched sample, indicating the retention of as-quenched state. The hardness variation is qualitatively consistent with that of positron annihilation parameters. Ultrasonic velocity measurements have revealed complementary variations. Metallographic studies have shown evidence towards the existence of hard intermetallic phases between 673 and 873 K, based on which the observed experimental results are explained.

A soft chemical route is described for the preparation of platinum nanorods and self-assemblies over photochemically reduced polyoxometalate (silicotungstate) containing composite films. Transmission electron microscopy shows that the diameters of the platinum nanorods are around 55-60 nm. The formation of platinum nanorods on solid-liquid interface reactions was explained on the basis of single site growth mechanism and diffusion limitation aggregation process. ? Indian Academy of Sciences.

Aligned nitrogen containing carbon nanotubes have been synthesized using Anodisc alumina membrane as template. Highly dispersed platinum nanoparticles have been supported on the nitrogen containing carbon nanotubes. Nitrogen containing carbon nanotubes as platinum catalyst supports were characterized by electron microscopic technique and electrochemical analysis. The EDX patterns show the presence of Pt and the micrograph of TEM shows that the Pt particles are uniformly distributed on the surface of the nitrogen containing carbon nanotube with an average particle size of 3 nm. Cyclic voltammetry studies revealed a higher catalytic activity of the nitrogen containing carbon nanotube supported Pt catalysts. Keywords: Nitrogen containing carbon nanotubes, Template synthesis, Alumina template, Catalyst support, Methanol oxidation

Microwave irradiation of various dialdehydes and chiral diamines afforded chiral macrocyclic imines in moderate to good yields. Linked dialdehydes predominantly form [2+2] macrocycles whereas dialdehydes without linkers yield [3+3] macrocycles. This is the first report of template-free synthesis of calixsalen-type macrocycles formed in shorter reaction times under microwave conditions. In all the reactions, the salts of chiral diamines were used in contrast to the free diamines normally employed. ? 2005 Elsevier Ltd. All rights reserved.

The electronically conducting hybrid material based on transition metal oxide and conducting polymer has been used as the catalyst support for Pt nanoparticles. The Pt nanoparticles loaded hybrid organic (polyaniline)-inorganic (vanadium pentoxide) composite has been used as the electrode material for methanol oxidation, a reaction of importance for the development of direct methanol fuel cells (DMFC). The hybrid material exhibited excellent electrochemical and thermal stability in comparison to the physical mixture of conducting polymer and transition metal oxide. The Pt nanoparticles loaded hybrid material exhibited high electrocatalytic activity and stability for methanol oxidation in comparison to the Pt supported on the Vulcan XC 72R carbon support. The higher activity and stability is attributed to the better CO tolerance of the composite material. ? 2004 Elsevier B.V. All rights reserved.

Mesoporous cubic MCM-48 was synthesized at a lower concentration of the surfactant. XRD, N 2 adsorption and electron microscopic studies confirmed the formation of cubic phase. Spectroscopic and electron spin resonance techniques confirmed the presence of heteroatom within the framework. The catalytic activities of various acid catalysts have been examined for vapour phase alkylation of naphthalene with alcohols and these studies revealed that aluminium substituted cubic MCM-48 was more active compared to Fe-MCM-48, Al-MCM-41 and H-Y zeolite. ? 2004 Elsevier B.V. All rights reserved.

Bis(ethylenediamine) copper(II) complex was encapsulated in NaY, KL, Naβ and NaZSM-5 zeolite. The redox properties of metal complexes in neat and encapsulated state were studied by cyclic voltammetry. The redox potential of metal complex is altered towards negative value upon encapsulation in various zeolites. This may be due to axial interaction with various zeolite matrix. The redox properties of biological systems are also altered (cytochrome-C, and Vitamin-B12) when they are immobilized on NaAlMCM-41 materials. The copper ethylenediamine complex in constrained environment shows higher activity for the oxidation of dimethyl sulfide compared to that of neat complex.

Trivalent iron incorporated mesoporous aluminophosphate was synthesized under hydrothermal conditions. The synthesized mesoporous Fe-AlPO was characterized by using various physico-chemical techniques, which confirm the formation of mesophase as well as the presence of trivalent iron in the framework. Catalytic activity of mesoporous Fe-AlPO was tested for the oxidation of cyclohexane.

Bis(8-hydroxyquinoline)manganese(II) [Mn(C9H6NO)2 (Mn–Qn)] was encapsulated in NaY, KL, MCM-41, Na and Na-ZSM-5. Characterization of the catalysts was done by using IR, UV–vis and EPR spectroscopy whereas redox properties of neat and encapsulated Mn–Qn complexes were evaluated by cyclic voltammetry. Peak broadening and different electrochemical responses are observed upon encapsulation of Mn–Qn complex in various zeolites, thus indicating that Mn–Qn complexes have altered values of redox potential in various positions of zeolite. In order to compare biological systems with metal complexes encapsulated in various zeolites, cytochrome- c was immobilized in MCM-41. Redox potential of cytochrome-c is shifted towards more positive value upon immobilization in MCM-41. This has been attributed to be due to conformational change of cytochrome-c in MCM-41. Change of redox potential of Mn–Qn complex in zeolites is due to change in the positions of HOMO and LUMO levels of metal complexes. Density functional theory (DFT) is employed to calculate the position of HOMO and LUMO levels of metal complexes in zeolite cluster models. The catalytic activity towards oxidation of cyclohexanol was performed using neat and encapsulated Mn–Qn complexes. Encapsulated complexes shows higher activity compared to that of neat complex. © 2004 Elsevier B.V. All rights reserved.

The esterification of triethylene glycol (TEG) with methacrylic acid (MAA) was carried out over various solid acid catalysts and the results were compared with conventional acid catalysts. Among the catalysts studied, heteropolyacids showed higher activities than the conventional acids. These were attributed to the acidity of the catalysts. A systematic investigation was carried out for the esterification of triethylene glycol with methacrylic acid over phosphotungstic acid without any free radical inhibitor. The effects of catalyst concentration, alcohol/acid molar ratio and temperature were also studied. Parameters such as activation energy, reaction enthalpy and reaction entropy were derived for the above reaction over phosphotungstic acid in the temperature range of 353–383 K. The obtained results were also compared with silicotungstic acid.

A virtual instrument based automated ion channeling experimental setup has been developed and implemented in a 1.7 MV tandetron accelerator. Automation of the PC based setup is done using a windows based virtual instrument software allowing the setup to be easily ported between different computer operating systems. The virtual instrument software has been chosen to achieve quick and easy development of versatile, multi-purpose user friendly graphical interface for carrying out channeling experiments. The software has been modular designed to provide independent control of the stepper motors for fixing the sample at any user defined orientation, running and on-line display of azimuthal and tilt angular scans, auto storage of the angular scan data. Using this automated setup, the crystallographic axis of the sample can be aligned with the incident ion beam rapidly minimizing the beam damages to the sample. A standard single crystalline GaAs(100) has been characterized with this set up using 2 MeV He++ ion ...

The organic-inorganic nanocomposites were synthesized by sol-gel techniques. The constructed film renders photochromism, which can be tuned by choosing suitable polyoxometalates (POM). The molybdenum POMs show better photochromism than the tungsten POMs, which is well correlated with the first reduction potentials and band gap of the POM.

Photothermal deflection spectroscopic technique was used to study Ar + implanted cadmium sulphide thin films. Variations in grain size and lattice strain due to Ar + irradiation were analysed using X-ray diffraction. Thickness of damaged layer in CdS due to Ar + implantation was calculated using photothermal deflection technique and compared with results from Stopping and Range of Ions in Matter.

Hydrogen storage by carbon materials is a topic of current interest. In order to exploit fullerenes as one of the new forms of carbon for hydrogen storage, it is shown that an activator for hydrogen is necessary in the fullerene network. Even though one can generate stoichiometric hydrides the formation of such hydrides have to be established. In this present study we have examined what type of species on carbon surfaces may be able to activate hydrogen molecule and lead to hydride formation. The Density Functional Theory calculations have been carried out on some typical model systems wherein the fullerene molecule is substituted in the network with heteroatoms like N, P and S and the reduction in the dissociation energy of hydrogen molecule is considered as a measure of the ability to hydride the carbon materials. On the basis of the reduction in the dissociation energy for the hydrogen molecule it was shown that heteroatom substitution in the fullerene net work may be suitable for the activation and dissociation of hydrogen molecule.

Bis(ethylenediamine)copper(II) [Cu(NH2CH2CH 2NH2)2]2+ (Cu-en) was encapsulated in NaY, KL, AlMCM-41, Na?, and Na-ZSM-5. Characterization of the catalyst was done by IR, UV-vis, and electron paramagnetic resonance (EPR), whereas redox properties of neat and encapsulated Cu-en complexes were evaluated via cyclic voltamrnetry. The difference in UV-vis and EPR parameters between neat and intrazeolite complexes suggests that the metal complex does not have the same geometry as that in the neat complex but does undergo distortion inside the system. Peak broadening and different electrochemical responses are observed on encapsulation of the Cu-en complex in various zeolites, thus indicating that Cu-en complexes have altered values of redox potential in various positions of zeolite. Change of redox potential of Cu-en complex in zeolites is due to a change in the positions of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the metal complexes. Density functional theory is used to calculate the position of the HOMO and LUMO levels of the metal complexes in zeolite cluster models. The HOMO and LUMO levels increase on encapsulation. When a substitution of the heteroatoms (B, Al, Ga) occurs, the HOMO and LUMO levels are stabilized, compared to those in pure silicious zeolites. An electric field acting inside the zeolite matrix is responsible for the change in the position of HOMO and LUMO levels of the metal complexes in various zeolites. Catalytic activity toward the oxidation of dimethyl sulfide by intrazeolite Cu-en complexes exhibits higher catalytic activity, compared to the neat complex.

The template carbonization of polyphenyl acetylene yielded well aligned, cylindrical, mono disperse carbon nanotubes (CNT), which are effectively utilized to load Pt, Pt-Ru, and Pt-WO3 nano particles. The nanoparticles are effectively dispersed inside the tube with the particle sizes of around 1.2, 1.6, and 10 nm for Pt, Pt-Ru, and Pt-WO3, respectively. The electrochemical surface area of the CNT-based electrode was higher compared to the Vulcun XC 72R carbon, graphite, and glassy carbon (GC) electrodes. The X-ray photoelectron spectroscopic measurements revealed that the Pt and Ru are in metallic state and W is in +VI oxidation state. The higher activity of GC/CNT-Pt-WO3-Nafion for methanol oxidation compared to GC/CNT/Pt-Ru-Nafion and GC/CNT/Pt-Nafion suggests the better utilization of the catalytic particles. The stability of the electrode for methanol oxidation polarized at +0.6 V follows the order of GC/CNT/Pt-Ru-Nafion > GC/CNT/Pt-WO3 > GC/CNT/Pt-Nafion, and for the electrodes polarized at +0.4 V, the order is GC/CNT/Pt-WO3-Nafion > GC/CNT/Pt-Ru-Nafion > GC/CNT/Pt-Nafion. The differences in the stability possibly suggest the better tolerance of the adsorbed species of methanol oxidation for the GC/CNT/Pt-WO3-Nafion electrode (when it is polarized at +0.4 V).

Thesynthesesofthermallystablechromium-incorporatinghexagonalmesoporousaluminophosphateandcubicCr-MCM-48have been reported. Characterization of the catalysts was made using low angle XRD, N 2 adsorption, UV-VISDRS, thermalanalysis, ICP-AES and ESR. Mesoporous Cr-AlPO 4 and Cr-MCM-48 catalysts have been found to be active for the vapourphase oxidation of toluene with molecular oxygen. Mesoporous Cr-AlPO 4 is found to exhibit both acidic and redox propertiesand hence oxidation as well as dealkylation reactions are taking place in a concerted manner, whereas, the cubic silicateanalogue acts as a pure redox catalyst.© 2002 Elsevier Science B.V. All rights reserved. Keywords: Chromium; Aluminophosphates; Mesoporous materials; Partial oxidation 1. IntroductionAluminophosphate materials, recently developed ascrystalline microporous materials are of potential useincatalysis[1].Flanigenetal.[2]reportedtheincorpo-ration of various elements into the framework sites ofaluminophospahtes and the resulting systems are ac-tiveforvariouscatalytictransformations.However,thepore dimensions of these materials are not sufficient toaccommodate a broad spectrum of organic moleculesin their cavities. With the first discovery of M41S bythe Mobil researchers, a series of mesoporous ma-terials with pore dimensions greater than 20A havebeen synthesised using structure-directing templates

The photoelectrochemical reduction of nitrite ions to ammonia on CdS photocatalysts was investigated in the slurry mode. The oxidation and the reduction reactions take place separately, thus, decreasing the electron–hole recombination and enhancing the yield of ammonia.

Carbon dioxide a common greenhouse gas is converted to value added products such as methane and ethane by electrochemical reduction at a surface oxidized copper electrode. The product yield and the relationships between the surface chemistry and reaction behavior were investigated. Ethane was observed as a dominant product at the surface oxidized Cu electrodes suggesting that Cu (I) species play a critical role in selectivity towards C2 species.

Formation of silver nanoparticles (AgNPs) by a biological route employing Crossandra infundibuliformis leaf extract has been investigated. The silver nanoparticles were formed in 1 h by stirring at room temperature. In this case, yellowish brown color was developed. Formation of AgNP was confirmed by surface plasmon spectra and absorbance peaks at 457 nm. Crystalline nature of the nanoparticle was face centered cubic (fcc) structure. The AgNPs formed were flake-like in shape and the average particle size was about 38 nm. � 2011 Elsevier B.V. All rights reserved.

The carbon nanotube (CNT) synthesised by the template carbonisation of polypyrrole on alumina membrane has been used as the support for Pt–WO3, Pt–Ru, and Pt. These materials have been used as the electrodes for methanol oxidation in acid medium in comparison with E-TEK 20 wt% Pt and Pt–Ru on Vulcan XC72R carbon. The higher electrochemical surface of the carbon nanotube (as evaluated by cyclic voltammetry) has been effectively used to disperse the catalytic particles. The morphology of the supported and unsupported CNT has been characterised by scanning electron micrograph and high-resolution transmission electron micrograph. The particle size of Pt, Pt–Ru, and Pt–WO3 loaded CNT was found to be 1.2, 2, and 5 nm, respectively. The X-ray photoelectron spectra indicated that Pt and Ru are in the metallic state and W is in the +VI oxidation state. The electrochemical activity of the methanol oxidation electrode has been evaluated using cyclic voltammetry. The activity and stability (evaluated from chronoamperometric response) of the electrodes for methanol oxidation follows the order: GC/CNT–Pt–WO3–Nafion>GC/E-TEK 20% Pt–Ru/Vulcan Carbon–Nafion>GC/CNT–Pt–Nafion>GC/E-TEK 20% Pt/Vulcan carbon–Nafion>Bulk Pt. The amount of nitrogen in the CNT plays an important role as observed by the increase in activity and stability of methanol oxidation with N2 content, probably due to the hydrophilic nature of the CNT.

Attempt has been made to obtain the relationship between the electrophysical and electrochemical properties in order to provide a possible basis for designing new electrode materials for fuel cell applications. The substituted lanthanum cuprates of composition La2−xMxCu1−yM′yO4 (where M=Sr, Ca and Ba; M′=Sb and Ru; 0.0≤x≤0.4 and y=0.1) were used to demonstrate the correlation of the Fermi level and carrier concentration with the methanol oxidation onset potential and activity, respectively. The activity of bulk material is compared with that of the nanocrystalline material prepared by the polymer modified sol–gel method. The nanocrystalline material was characterized by TGA, XRD, SEM, TEM and cyclic voltammetry.

This paper describes the encapsulation of μ-oxo bridged dinuclear iron 1,10 phenanthroline (Fe-phen) complex in MCM-41. These systems have been characterized by thermogravimetric analysis (TGA), UV–Vis, FT-IR, EPR and cyclic voltammetry. On encapsulation reduction potential of Fe-phen is shifted by 275 mV more positive due to perturbation of molecular energy levels. Because of antiferromagnetic coupling a decrease in EPR signal intensity is observed as temperature is lowered from 300 to 77 K. By comparing the performance of the heterogeneous system with the free complex in the oxidation of benzyl alcohol using t-butyl hydroperoxide (TBHP), a protection effect of the matrix over the active center was evidenced by high turnover and yield of product. UV–VIS spectrum shows in neat complex Fe–O–Fe bridge is cleaved during the oxidation of benzyl alcohol while in encapsulated system, it is stable.

Zirconium doped tunnel structure manganese oxide (OMS-2) materials were synthesized by reflux and impregnation methods by adopting suitable synthetic conditions. XRD and TGA analyses were used tocharacterize the crystal structure and thermal stability of as synthesized zirconium doped manganese oxide OMS-2 catalysts. FT-IR and BET analyses were used to interpret the stretching frequency of corresponding functional group present in the catalysts and surface area of as synthesized catalysts. Fibrous structure and the aggregated particle morphology of zirconium doped manganese oxide OMS-2 catalysts were confirmed by TEM analyses. The synthesized catalysts were tested for liquid phase oxidation of side chain aromatic compounds such as ethyl benzene and benzyl alcohol, TBHP (tert-butyl hydrogen peroxide) as the chemical oxidant. Liquid phase oxidation ethyl benzene over zirconium doped tunnel structure manganese oxide OMS-2 catalysts show the higher substrate conversion compared to that of benzyl alcohol oxidation on as synthesized zirconium doped manganese oxide OMS-2 catalysts.

Vanadium incorporated hexagonal mesoporous aluminophosphate characteristic of MCM-41 has been synthesized. Characterization of the catalyst has been done by using low angle XRD, N2 adsorption, UVVIS DRS, thermal analysis, XPS and ESR spectroscopy. These techniques confirm the presence of vanadium in both +4 and +5 oxidation states in the calcined material. Liquid phase partial oxidation of toluene has been carried out on V-AlPO using 70% TBHP and 30% H2O2 as oxidants. When 70% TBHP is used as an oxidant, it resulted in side chain oxidation giving rise to aldehyde/acid where as with 30% H2O2, side chain as well as ring oxidation takes place. Catalytic activity of V-AlPO has been compared with that of VMCM-48 and other vanadium containing catalytic systems. It has been observed that mesoporous V-AlPO shows higher conversion and is also selective towards side chain oxidation products. The higher conversion of V-AlPO over V-MCM-48 has been attributed to the stabilization of the active V+5/+4 species in AlPO framework as compared to silicate analogue.

Ni (15% w/w) supported on alumina, silica and titania (P-25, anatase and rutile phases) have been investigated for the liquid phase hydrogenation of cinnamaldehyde. XRD, TPR and XPS data (binding energy shifts for Ni 2p ) indicate metal-support interactions in all supported catalysts. Weaker bonding of H 2 on Ni/TiO 2 (H 2 -TPD) improves activity. Ni/TiO 2 phases display higher cinnamaldehyde conversion and selectivity to cinnamyl alcohol compared to the catalysts supported on alumina and silica. Amongst the three polymorphs of titania, the maximum activity and selectivity displayed by Ni/ TiO 2 -P-25, is attributed to the active Ni crystallites located at the interface between anatase and rutile phases in titania P-25 matrix (HRTEM). Though Ni crystallites on alumina and silica are relatively smaller (compared to those on the three TiO2 phases) in size, their activity vis-a-vis for those supported on titania phases is less, implying that factors other than crystallite size influence the performance.

Correction for ‘Mesoporous carbon nitrides: synthesis, functionalization, and applications’ by Kripal S. Lakhi et al., Chem. Soc. Rev., 2017, DOI: 10.1039/c6cs00532b.