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Activated carbon from agro waste groundnut (Arachis hypogaea) shell was prepared by chemical activation and used as support for dispersion of 5% platinum nanoparticles. The Pt nanoparticles were obtained by the reduction in hydrogen gas medium. The synthesized groundnut activated carbon/platinum catalyst was characterized by various techniques such as X-ray powder diffraction, electron microscopies and X-ray photoelectron spectroscopy. The catalytic behaviour of the synthesized catalyst was investigated by exploring it as catalyst for the reduction of various classes of dyes; namely, triphenylmethane dyes such as malachite green, phenol red and bromophenol blue, xanthene dyes: rose bengal, rhodamine 6 G, rhodamine B, thiazine dye: methyelene blue, azo dye: congo red and 4-nitrophenol by sodium borohydride in aqueous medium. Under suitable reaction conditions, for all tested dyes, cationic dyes were reduced at a faster rate than anionic dyes. The rate of reduction on the structure of dye and nature of catalyst was employed.

Herein, the fluorescent carbon dots (CDs) with blue emission were prepared by hydrothermal treatment using pineapple peel as a source of carbon. The as-prepared CDs exhibited turn-Off fluorescence behavior toward Hg2+ and subsequent turn-On behavior for l-cysteine along with enhanced biocompatibility and negligible cytotoxicity for cell imaging. The practical applicability of carbon dots was used for the quantification of Hg2+ in water. On the basis of the spectral characteristic changes, we have designed individual elementary logic operations such as NOT and IMP gates, by utilizing CD as probe and Hg2+ and l-Cys as chemical inputs. We have also demonstrated the utility of this system in electronic security devices and as memory element, with the idea of the switching.

Hierarchical mesoporous TiO2 was synthesized via a solvothermal technique. The sonochemical method was adopted to decorate plasmonic nanoparticles (NPs) (Ag, Au) on the pores of mesoporous TiO2. The crystallinity, structure, and morphology were determined to understand the physicochemical nature of the nanocomposites. The catalytic efficiency of the plasmonic nanocatalysts was tested for the azo dyes (congo red, methyl orange, acid orange 10, and remazol red) under solar and visible light irradiations. The generation of hydroxyl radicals was also studied using terephthalic acid as a probe molecule. An attempt was made to understand the influence of size, work function and Fermi level of the metal NPs toward the efficiency of the photocatalyst. The efficiency of the nanocomposites was found to be in the order of P25 < mesoporous TiO2 < mesoporous Ag–TiO2 < mesoporous Au–TiO2 nanospheres under both direct solar light and visible light irradiation. The results indicated that the adsorption of dye, anatase ph...

Strontium titanates, SrTiO3, Sr3Ti2O7 and Sr4Ti3O10, with perovskite structure, have been modified by co-doping with N, S and Fe and characterized by X-ray diffraction (XRD), Diffuse reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDXA), X-ray Photoelectron Spectroscopy (XPS) and Photo Luminescence Spectroscopy (PLS) techniques. XRD, EDXA and XPS results substantiate the incorporation of the three dopants into the titanate matrices. Based on the XPS binding energy data, it is inferred that doped nitrogen in SrTiO3 and Sr4Ti3O10 phases occupies O2− ion sites by substitution and interstitial sites in Sr3Ti2O7. Fe as Fe3+ and S as cationic S6+ occupy Ti4+ ion sites in the respective lattice in all three titanates. Additional energy levels created by the dopants within the band gap result in narrowing of the band gap, as revealed by DRS data and thus enable visible light absorption by the modified titanates. Significant reduction in the intensity of photo luminescence emission lines of modified titanates indicates that doping retards the recombination rates of charge carriers, enhancing their life time. Changes in the photo-physical properties brought out by modification with dopants improve the activity for photo catalytic reduction of CO2 vis-a-vis pristine titanates. Both Sr3Ti2O7 and Sr4Ti3O10, perovskites with layered structure, display higher activity when compared to simple perovskite, SrTiO3. Layered structure facilitates faster transport of charge carriers and the interlayer space could function as oxidation/reduction reaction sites, leading to the separation of charge carriers. Amongst the two layered perovskites, double layered Sr3Ti2O7 displays higher activity compared to triple layered Sr4Ti3O10 since the conduction band minimum of Sr3Ti2O7 is at higher negative energy level vis-a-vis that for Sr4Ti3O10 and the inter layer spacing is appropriate for CO2 reduction and splitting of water as well.

Metal cluster, at sub-nanometer level has a unique property in the activation of small molecules, in contrast to that of bulk surface. In the present work, singly exposed active site of copper metal cluster at sub-nanometer level was designed to arrive at the energy minimised configurations, binding energy, electrostatic potential map, frontier molecular orbitals and partial density of states. The ab initio molecular dynamics was carried out to probe the catalytic nature of the cluster. Further, the stability of the metal cluster and its catalytic activity in the electrochemical reduction of CO 2 to CO were evaluated by means of computational hydrogen electrode via calculation of the free energy profile using DFT/B3LYP level of theory in vacuum. The activity of the cluster is ascertained from the fact that the copper atom, present in a two coordinative environment, performs a more selective conversion of CO 2 to CO at an applied potential of −0.35 V which is comparatively lower than that of higher coordinative sites. The present study helps to design any sub-nano level metal catalyst for electrochemical reduction of CO2 to various value added chemicals.

Mesoporous carbon nitrides (MCNs) with large surface areas and uniform pore diameters are unique semiconducting materials and exhibit highly versatile structural and excellent physicochemical properties, which promote their application in diverse fields such as metal free catalysis, photocatalytic water splitting, energy storage and conversion, gas adsorption, separation, and even sensing. These fascinating MCN materials can be obtained through the polymerization of different aromatic and/or aliphatic carbons and high nitrogen containing molecular precursors via hard and/or soft templating approaches. One of the unique characteristics of these materials is that they exhibit both semiconducting and basic properties, which make them excellent platforms for the photoelectrochemical conversion and sensing of molecules such as CO2, and the selective sensing of toxic organic acids. The semiconducting features of these materials are finely controlled by varying the nitrogen content or local electronic structure of the MCNs. The incorporation of different functionalities including metal nanoparticles or organic molecules is further achieved in various ways to develop new electronic, semiconducting, catalytic, and energy harvesting materials. Dual functionalities including acidic and basic groups are also introduced in the wall structure of MCNs through simple UV-light irradiation, which offers enzyme-like properties in a single MCN system. In this review article, we summarize and highlight the existing literature covering every aspect of MCNs including their templating synthesis, modification and functionalization, and potential applications of these MCN materials with an overview of the key and relevant results. A special emphasis is given on the catalytic applications of MCNs including hydrogenation, oxidation, photocatalysis, and CO2 activation. Refereed/Peer-reviewed

Lanthanum doped sodium tantalate (Na(1−x)LaxTaO(3+x)) with Pt, Ag, Au, CuO, NiO and RuO2 as co-catalysts, have been prepared and characterized by XRD, DRS, photoluminescence spectroscopy, SEM and TEM. Photocatalytic reduction of CO2 on these catalysts in alkaline medium under UV–Visible radiation yields methanol and ethanol as major products with traces of methane, ethane, ethylene, etc. Maximum apparent quantum yield (AQY) for CO2 reduction is achieved on the formulation with 0.2 wt% NiO, followed by 1 wt% CuO as co-catalysts. DRS studies reveal that the addition of co-catalysts brings about reduction in band gap energy of NaTaO3 and its light absorption onset edge is extended into the visible region. Coupling of the conduction band bottom energy levels of NiO and CuO with that of Na(1−x)LaxTaO(3+x) shows that they facilitate easy transfer of photo-generated electrons from the doped tantalate to NiO/CuO, wherein these electrons participate in simultaneous hydrogen generation by water splitting and CO2 photoreduction processes. Other co-catalysts, like, Pt, Ag, Au and RuO2 act as electron traps, resulting in charge separation, which, in turn, leads to improvement in photo-catalytic activity. Besides, significant reduction in the intensity of photoluminescence lines observed for Na(1−x)LaxTaO(3+x) with different co-catalysts also indicates longer life time of the charge carriers. Used catalysts retain the cubic perovskite structure of the fresh catalyst during the reaction for 20 h and stable activity is displayed for three cycles. The alkaline medium plays multiple roles, acting as scavenger of holes, increasing the solubility of CO2 and stabilization of NiO. NaTaO3 based catalysts could become viable alternatives to titania for this application.

Bimetallic catalysts of the type Ni–M with M = Cu, Ag and Au, and supported on TiO2-P-25 have been prepared by chemical reduction using glucose as the reducing agent. Hydrogenation of cinnamaldehyde (CAL) to yield hydrocinnamaldehyde (HCAL), cinnamyl alcohol (COL) and hydrocinnamyl alcohol (HCOL) has been studied on the catalysts in the temperature range 60–140 °C and at 20 kg/cm2 pressure, with methanol as solvent. Ni crystallite sizes, measured by X-ray line broadening analysis (XLBA), H2 pulse chemisorption and Transmission Electron Microscope (TEM) techniques, are in the range 8–12 nm. Temperature Programmed Reduction (TPR) and Diffuse Reflectance Spectroscopic (DRS) studies indicate the formation of Ni–Cu alloys, while Ni–Ag and Ni–Au exist as bimetallic nanoparticles. High-resolution HRTEM studies show that the bimetallic nanoparticles are in close contact, forming hetero junctions. Changes in the XPS binding energy values for Ni 2p1/2 and Ni 2p3/2 levels reveal that Cu/Ag/Au, tend to increase electron density around Ni, which retards the adsorption of CAL via olefinic bond and weakens Ni H bond strength. H2 TPD measurements also indicated weakening of Ni H bond. Bimetallic catalysts display higher CAL conversion and selectivity to COL vis-a-vis the corresponding monometallic catalysts at lower reaction temperatures, 60–80 °C. But, selectivity to COL decreases at higher temperatures, 100–120 °C. Mode of adsorption of CAL and nature of adsorbed hydrogen on bimetallic catalysts influence their activity and selectivity.

Developing new efficient catalysts for the electrochemical reduction of carbon dioxide to formic acid is important in the process of mitigating environmental CO2. In the present work, we have designed metal (M) clusters anchored on a polyaniline (PANI) conducting polymer electrode (M@PANI), where, M = Ni, Pd, Pt, Cu, Ag & Au, and evaluated their potential catalytic activity towards CO2 reduction by means of computational hydrogen electrode using hybrid density functional theory methods. The predicted binding energy and electronic properties of M@PANI suggest a thermodynamically feasible reaction which retains its conducting property with enhancement. The modified electrodes favour the formation of HCOOH involving H*COO species via the formate pathway. The computed limiting potentials suggest that Cu@PANI is a suitable electrode material for the CO2 reduction reaction leading to HCOOH.

An investigation of the nature of adsorption of H2O and CO2 on a nitrogen doped zinc oxide cluster surface and the resultant reaction between them has been performed using hybrid density functional theory (DFT) calculations at the B3LYP level of theory in a vacuum. The stable chemisorption modes of CO2 and H2O on metal, oxygen and nitrogen sites were examined. The calculated adsorption energies reveal that the formation of CO2- attached to N is the most favorable process for CO2 on the Zn18O17:N cluster surface, with a binding energy of -1.86 eV. The water molecule spontaneously dissociates on the same surface to produce chemisorbed H? and?OH with an interaction energy of -0.77 eV. The model calculations rationalize the hydrogenation of CO2 by H2 generated from H2O on the cluster surface. Thermodynamically favorable reaction pathways for the formation of methanol on the catalytic surface in a vacuum were proposed. Among the three pathways, methanol formation follows the carbamate route. The carbamate formed undergoes hydrogenation to generate COOH? units, followed by its exothermic decomposition to?CO attached to N and?OH. Further hydrogenation of CO ultimately yields methanol. All of the above steps were computationally evaluated. � The Royal Society of Chemistry 2015.

Potassium-birnessite (K-OL-1) samples of different morphologies (nanowire networks, nanoparticles and mesoporous hierarchical nanowire networks) and textural properties were synthesized from KMnO4 by using oxalate-reduction method under ambient conditions. Cryptomelane (K-OMS-2) samples of similar morphologies were synthesized by the calcination of birnessite samples. The synthesized MnO2 samples were characterized by XRD, TGA, DTA, SEM, TEM, nitrogen adsorption-desorption and ICP-OES analyses. One each of the birnessite and the cryptomelane samples showed mesoporous nature (pore size ?50 � and 66 � respectively). The pH of the reaction medium has been found to have a key role in the properties of the resulting MnO2 samples. Electrochemical studies of MnO 2-carbon black composites were performed in 0.1 M aqueous Na 2SO4 solution using cyclic voltammetry and galvanostatic charge-discharge cycling. One of the birnessite samples with nanowire network morphology and a BET surface area of 202 m2 g-1 exhibited a high capacitance value of 234 F g-1. Electrochemical studies revealed that the specific capacitance values of the studied MnO2 materials have a direct relationship with their BET surface area values. Birnessite samples have exhibited better capacitance behavior and values than their cryptomelane derivatives. The effect of the morphology has also been reflected in the values of the specific capacitance. This journal is � the Partner Organisations 2014.

The hydrogenolysis of sorbitol into 1,2-propanediol (PD), ethylene glycol (EG) and glycerol (G) was investigated over Ni, Pt and Ru supported on NaY at 220 °C and 60 bar in a batch reactor. Ni(6 %)–NaY was investigated in detail at different process conditions, including its recyclability. Attempts have been made to rationalize the experimentally observed conversion and product selectivity obtained over the different catalysts with results of Density Functional Theory calculations of adsorption energy and bond length changes in sorbitol adsorbed over various planes of Ni, Pt and Ru.

The liquid phase selective hydrogenation of cinnamaldehyde has been investigated on cobalt (15 wt%) impregnated on alumina, silica and various phases of titania supports. The multiple reduction stages observed in the TPR studies suggest the presence of cobalt aluminate/silicate/titanate species, and DRIFT spectra results seem to corroborate this observation. An optimum level of conversion and selectivity to cinnamyl alcohol was observed at 120 °C and 10 kg/cm2 hydrogen pressure. Co/TiO2 exhibited a greater conversion (47.4%) and selectivity to cinnamyl alcohol (58%) than Co/Al2O3 and Co/SiO2, which may be attributed to the presence of TiO x (x Co/SiO2 > Co/Al2O3. The hydrogenation of CMA is believed to preferentially proceed via adsorption of C=O on the surface of Co/TiO2.

Dependence of catalytic activity in CO oxidation on the structure of gold nanoparticles supported on various TiO 2 polymorphs has been investigated. Pure brookite, brookite–anatase (45:55) and anatase–rutile (85:15) mixtures were compared as supports of Au/TiO 2 . Au nanoparticles were deposited on different TiO 2 supports by adsorption of Au colloids of about 6 and 15 nm mean diameter and by deposition precipitation (DP) with urea providing Au particles smaller than 5 nm in size. Sol derived gold particles were more stable against sintering on brookite than on anatase containing supports. Taking into account the particle sizes of gold and titania for all types of gold deposition methods, the Au–anatase perimeter seems to be significantly more active in CO oxidation than the Au–brookite perimeter. The difference in activity should be originated from the different electronic, physical and surface properties of anatase and brookite.

The abilities of Keggin type polyoxometalate, silicotungstic acid (STA) to reduce metal ions by electron transfer and to modify carbon surface by strong adsorption have been explored for the preparation of Pt nanoparticles supported on carbon composites (20% Pt/STA-C). The prepared composites were characterized by Transmission electron microscopy (TEM and HRTEM)), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The electrocatalytic activities of the prepared nanocomposites were examined by using Cyclic voltammetry (CV) for oxygen reduction reaction which takes place at cathode in fuel cells. The prepared composite (20% Pt/STA-C) proved efficient compared to STA free 20% Pt/C, prepared by hydrogen reduction method. H2O2 intermediate formation is a serious concern as it reduces the activity of Pt sites during oxygen reduction. The composites prepared by polyoxometalate reduction method (20% Pt/STA-C) showed better reduction ability towards H2O2 compared to STA free 20% Pt/C composite and thus showed better performance as cathode electrocatalyst for fuel cells.

The void swelling behaviour of (15Ni–14Cr) Ti-modified steels simulated by heavy ion irradiation, has been investigated using step height measurements and positron annihilation spectroscopy. 18% cold-worked samples were pre-implanted with helium at 170 keV and 275 keV energies so as to create a uniform helium concentration of 100 appm around the 588 nm depth region. This was followed by a 2.5 MeV Ni ion irradiation to create a peak damage of ~ 84 dpa (displacement per atom) at various irradiation temperatures between 700 and 970 K. The gross swelling which has occurred throughout the ion range is determined by step height measurements. Defect-sensitive positron annihilation lineshape S-parameter measurements show clear changes consequently to void formation as a function of sample depth. From the variation of the average S-parameter as a function of irradiation temperature, the peak swelling temperature has been deduced. The changes observed in step height measurements are compared with positron annihilation measurements and the results are discussed.

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.

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.

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.

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.

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.

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.

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.

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.

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.

With the aim of finding a suitable electrocatalyst for the efficient reduction of carbon dioxide, the electrochemistry of nickel (II) complex of 1,3,6,9,11,14-hexaazatricyclo [12·2·1·1] octadecane was studied using cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) techniques in the presence and absence of CO2 in 100% H2O, CH3CN-H2O mixtures (20–100%) and DMF-H2O (70–100%) mixtures. The efficiency of this process is determined using the coulometry technique. CO is the major product in the gaseous phase and HCOOH the sole product formed in the solution phase.

Depth resolved investigations of defects and their evolution upon inter-diffusion have been carried out on Al/Ge thin film bilayers, using concurrent measurements of positron beam based Doppler broadening lineshape and secondary ion mass spectrometry (SIMS) profiles. Measurements have been made on the as-grown film and films annealed at various temperatures from 370 to 670 K. SIMS studies establish the occurrence of extensive intermixing of the Al and Ge layers beyond 370 K. It is found that there is an asymmetric diffusion across the interface, with Ge being the dominant diffusing species. The intermixed Al/Ge region formed in the near-surface layers of the sample annealed at 670 K shows Ge precipitation, as confirmed by electron microscopy and SIMS imaging. Analysis of the Doppler broadening line shape variation, together with the SIMS concentration profiles, indicates increased production of small vacancy clusters at the Al/Ge interface around 520 K, brought about by the enhanced diffusion of Ge. The interfacial vacancy structure is inferred to be a tri-vacancy cluster.

A series of rare earth cuprates with overall composition Ln2-xMxCu1-yM?y O4-� (where Ln = La and Nd; M = Sr, Ca and Ba; M? = Ru and Sb: 0.0 � x � 0.4 and y = 0.1) have been tested as anode electrocatalysts for methanol oxidation. The evaluation of electrode kinetic parameters was made galvanostatically. The catalyst characterization was carried out by specific conductivity measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Iodometry. These materials exhibit significant activity for methanol oxidation at higher potentials. The linear correlation between Cu(3 +) content and methanol oxidation activity suggests that the active sites for adsorption of methanol is Cu(3 +). The methanol oxidation onset potential depends on the ease of Cu(2 +) ? Cu(3 +) oxidation reaction. These materials show better tolerance towards the poisoning by the intermediates of methanol oxidation compared to that of conventional noble metal electrocatalysts (supported and bulk). The lattice oxygen in these oxides could be considered as active oxygen to remove CO intermediates of methanol oxidation reaction. ? 2001 Elsevier Science B.V.

The carbonization of polyphenyl acetylene in alumina matrix yields uniform, cylindrical, monodisperse carbon nanotubes with outer diameter almost equal to pore diameter of the alumina membrane used. Theelectrochemical characteristics reveal that the charge transfer at the composite electrode based on carbon nanotube might be higher compared to that of planar graphite, glassy carbon and composite electrode based on commercially available Vulcan XC72R carbon. Pt-Ru nanoparticles are highly dispersed inside the tube with an average particle size of 1.7 nm as revealed by HR-TEM images.

Microbiologically influenced corrosion of carbon steel has been investigated. Carbon steel coupons were exposed online in the cooling water system of a nuclear test reactor to assess the microbial growth on the coupons and the corrosion phenomena. Iron bacteria, sulphate reducing bacteria (SRB) and culturable aerobic heterotrophic bacteria (CAHB) were monitored both on the coupons and in the cooling water. Corrosion rate was assayed by weight loss method and corrosion products analysed by XRD and Mossbauer spectroscopy. Extensive tuberculation of carbon steel coupons was noticed. SEM pictures revealed the presence of ensheathed filamentous iron bacteria encrusted with corrosion products. Beneath the tubercles significant pitting and SRB induced corrosion in the form of concentric rings was observed. From the phase analysis, the following compounds were found to be present: γ-Fe2O3, Fe2PO5, FePS3, Fe(PO3)3 and BaFeO3 − x. From the present study it is inferred that iron bacteria (Leptothrix sp.) and SRB (Desulfovibrio sp.) are responsible for the corrosion of carbon steel. The role of these bacteria in influencing the corrosion of carbon steel is highlighted.

The nature and concentration of the acid sites of MCM-41 material as a function of Si/Al ratio have been monitored by in situ IR using pyridine as a probe molecule. The thermal stability of aluminium in the framework of these materials is studied using 27Al MAS NMR spectroscopy. The tetrahedral to octahedral aluminium ratio is found to increase with higher aluminium incorporation. The sample with the lowest Si/Al ratio is found to exhibit higher acidity compared to the other samples. However, the acidity of these mesoporous aluminosilicates is less compared to the conventional H-Y zeolite. ? 1999 Elsevier Science B.V. All rights reserved.

Mo-incorporated MCM-41 has been prepared by direct hydrothermal synthesis. XRD and N2-adsorption measurements showed the characteristics of MCM-41. IR, FT-Raman and UV-VIS DR spectroscopic analyses gave the evidences for the incorporation of Mo in the framework of MCM-41. They are found to be stable and active for cyclohexanol and cyclohexane oxidation reactions with H2O2 as oxidant. Activity of this system has been compared with that of Ti-MCM-41 and molybdena impregnated on pure siliceous MCM-41.

Noble metal loaded TiO2 catalysts have been employed as catalysts for the photocatalytic reduction of nitrite and nitrate ions to ammonia. The yield of ammonia was found to depend on the nature, amount of metal and the method of metallization. An optimum metal content is beneficial for the activity. Beyond the optimum content the activity decreases. ? 1997 Elsevier Science S.A.

Fe-doped TiO2 catalysts were prepared by coprecipitation and the sol-gel method. The anatase to rutile phase transformation is dependent on the nature of the precursor used. Sol-gel-derived iron-doped catalysts show the presence of rutile and pseudobrookite phases, whereas coprecipitated catalysts show only the anatase phase. The role of the dopant ion is primarily to improve the charge separation of the photoproduced electron-hole pairs via a permanent electric field. The photocatalytic activity of the iron-doped catalysts can be explained in terms of the heterojunction formed between the Fe/TiO2 and �-Fe2O3 phases for the sol-gel-derived catalyst. ?1997 Elsevier Science S.A.

Doping of TiO2 with altervalent cations, Fe3+, Cr3+, Co2+ and Mg2+ leads to a red shift in the onset of absorption. The role of the dopant ions is primarily to improve the charge separation by means of a permanent electric field. Doping of TiO2 also influences the adsorption of reagent species and the resulting photoactivity is a consequence of these two factors. An optimum level of dopant ions is beneficial for the photocatalytic activity of TiO2. ? 1997 Elsevier Science S.A.

Nitrogen-doped graphene and carbon nanotubes were prepared and employed as additives to NaAlH4 to facilitate hydrogenation and dehydrogenation reactions. The decomposition behavior of carbon nanomaterial admixed NaAlH 4 was studied by constant temperature desorption, differential scanning calorimetry and in situ FT-IR experiments. Carbon nanomaterials decrease the dehydrogenation temperature of NaAlH4 and enhance the dehydrogenation kinetics by lowering the activation energy. A reversible hydrogen storage of 1.8 wt% was achieved by the nitrogen-doped carbon nanotube/nitrogen-doped graphene admixed sodium aluminum hydride. � 2013 The Royal Society of Chemistry.

The photocatalytic reduction of dinitrogen to ammonia is influenced by the nature and amount of metal loading on TiO2. The optimum metal content varies depending on the nature of the metal. A correlation between the ammonia yield and the intermediary MH bond strength is established (low bond strength gives rise to low ammonia yield).

The in situ deposition of Pt and Ir on CdS during the photocatalytic decomposition of aqueous sulfide results in the formation of an effective bifunctional photocatalyst (MS/CdS/M, where MS is Pt or Ir sulfide and M is Pt or Ir) which is more active than CdS and metallized CdS. In situ metallization provides a convenient method for the preparation of metal- and metal-sulfide-deposited CdS. The order of reactivity for the in situ metallization of CdS in the case of the photocatalytic decomposition of aqueous sulfide is Rh > Pt > Ru = Ir > Co ≃ Ni ≃ Fe. Based on the observed results a mechanism for the photocatalytic decomposition of aqueous sulfide is proposed.

Oxidising behaviour of both simple and substituted heteropoly compounds was investigated under homogeneous conditions in the presence of H2O2 and t-BuOOH with organic sulphides and alkyl benzenes as substrates. Activity of these catalysts depends on the nature of the substrates used as well as the oxidising agent employed. The mechanistic aspects of the reaction are also elucidated.

Scattered Wave SCF-Xa calculations were carried out on various Mo-containing cluster models in order to find out the possibility of molybdenum incorporation in a zeolitic framework, containing ring systems as secondary building units. Four and six membered ring clusters were found to stabilize molybdenum in their framework compared to that by linear chain models. Comparison of relative stabilization energies for corner and edge shared MoO4 moiety favoured the formation of the former one. Calculated HOMO-LUMO electronic transition for tetrahedrally coordinated molybdenum in Mo-containing ring clusters showed a shift of 15 nm from that in Mo-containing linear chain clusters. These results were compared with the experimental results obtained from UV-DRS studies on Mo-MCM-41 catalyst.

Zinc oxide with different morphologies like stars, multipods, ellipsoids and spikes was synthesized using zinc nitrate and sodium hydroxide in the absence of surfactants. Seed mediation was found to be essential for the formation of ZnO nanospikes. Synthesized ZnO samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), UV-visible diffuse reflectance spectroscopy (UV-vis-DRS) and energy dispersive analysis by X-rays (EDAX) techniques. The predominant c-axis growth of hexagonal lattice was observed in ZnO anisotropic particles. TEM analysis revealed the formation of two types of ZnO ellipsoid particles. Concentration of the reactants was found to have a role in controlling the morphology of the resulting ZnO. Mechanism of formation of varying morphologies of ZnO particles has been proposed. � 2011 American Scientific Publishers. All rights reserved.

Ni-Mo catalysts have been prepared using MCM-41, SBA-15, AlMCM-41, a blend of dealuminated BEA and alumina (DAl BEA-AL) and ?-Al2O 3 as supports. The supports/catalysts have been characterized by N2-adsorption, XRD, UV-vis, Raman spectroscopy, temperature programmed reduction and temperature programmed desorption of NH3. The catalysts have been evaluated in the temperature range between 553 and 613 K for the hydrodenitrogenation (HDN) of quinoline (Q) and 1,2,3,4- tetrahydroquinoline (1THQ) at 50 bar pressure using a feed containing 5 wt% of the N-compound in decalin. Cumene cracking studies have also been carried out over the sulfide catalysts at temperatures between 623 and 723 K. Over all the catalysts, HDN of 1THQ is easier than that of Q. The most active catalyst for HDN of Q was Ni-Mo/DAl BEA-AL followed by Ni-Mo/Al2O3, for 1THQ, the order was Ni-Mo/DAl BEA-AL followed by Ni-Mo/AlMCM-41. � 2012 Elsevier B.V.

The possibility of hydrogen production by photo-catalytic decomposition of water on titania has provided the incentive for intense research. Titania is the preferred semiconductor for this process, in spite of its large band gap (~3.2 eV) that restricts its utility only in the UV region. Various sensitization methodologies have been adopted to make titania to be active in the visible region. Doping of TiO2with nitrogen is one such method. The purpose of this presentation is to examine the state and location of nitrogen introduced in TiO2lattice and how far the shift of optical response to visible radiation can be beneficial for the observed photo-catalysis. The specific aspects that are discussed in this article are: (i) N-doped titania surface adopts a non-native configuration, though the bulk material is still in the native configuration of pure TiO2(ii) Though the nitrogen doped materials showed optical response in the visible region, the changes/improvements in photo-catalytic activity are only marginal in most of the cases. (iii) The exact chemical nature/state of the introduced nitrogen, and its location in titania lattice, substitutional and/or interstitial, is still unclear (iv) Is there a limit to the incorporation of nitrogen in the lattice of TiO2?

Anisotropic silver nanoparticles (NPs) have been synthesized rapidly using microwave irradiation by the decomposition of silver oxalate in a glycol medium using polyvinyl pyrolidone (PVP) as the capping agent. The obtained Ag nanoparticles have been characterized by UV-visible spectroscopy, powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) studies. Anisotropic Ag nanoparticles of average size around 30 nm have been observed in the case of microwave irradiation for 75 s whereas spherical particles of a size around 5-6 nm are formed for 60 s of irradiation. The texture coefficient and particle size calculated from XRD patterns of anisotropic nanoparticles reveal the preferential orientation of (111) facets in the Ag sample. Ethylene glycol is found to be a more suitable medium than diethylene glycol. A plausible mechanism has been proposed for the formation of anisotropic Ag nanoparticles from silver oxalate. � IOP Publishing Ltd.