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The catalytic performance of supported metal oxides is often controlled by their two- or three-dimensional dispersion. Silica, one of the popular inert supports, triggers the undesired formation of three-dimensional nanoparticles ...
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The catalytic performance of supported metal oxides is often controlled by their two- or three-dimensional dispersion. Silica, one of the popular inert supports, triggers the undesired formation of three-dimensional nanoparticles at significantly lower loadings than other conventional supports like Al2O3, TiO2, Nb2O5, or ZrO2. This observation has been ascribed to the lower reactivity of surface SiOH groups toward the precursor, compared to other metal hydroxyl groups on different supports. In this contribution, we show that by promoting amorphous silica with low amounts of sodium, the surface density of two-dimensional metal oxide species can be significantly enhanced to the same level as all other oxide supports previously reported in the literature. This effect is demonstrated for the case of supported vanadia using a variety of spectroscopic techniques (i.e., Raman, diffuse reflectance UV-vis, and V-51-MAS NMR), as well as a catalytic activity study for the oxidative dehydrogenation of propane (ODHP), a structure-sensitive probe reaction. The propane consumption rate was found to increase linearly with the vanadium surface density while the propylene selectivity was not affected until a monolayer coverage of ca. 9 vanadia per nm(2) was surpassed. The method is also applicable to other group V metals (i.e., Nb- and Ta-oxide), opening new perspectives for supported metal oxides.
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The study of nanocomposites formed by doping of graphene oxide with a metal and polymer is presented in this paper. The graphene oxide contains oxygenated functional groups, like epoxy, hydroxyl and carboxyl, as shown by Fourier t...
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The study of nanocomposites formed by doping of graphene oxide with a metal and polymer is presented in this paper. The graphene oxide contains oxygenated functional groups, like epoxy, hydroxyl and carboxyl, as shown by Fourier transform infrared spectroscopy (FTIR) studies. The existence of these functional groups on the surface of graphene oxide disperses the polymer chain and leads to a good interaction with the metal. The characterization of the prepared nanocomposite was done by X-ray diffraction, energy dispersive X-ray analysis, FTIR, Raman spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy. The results showed that the obtained nanocomposite comprises nano-shaped thin stacked flakes with a well-defined multilayered edge structure. It was also seen that the metal particles were uniformly dispersed on the graphene surface with an average particle size of 1-25 nm. The synthesized nanocomposites can be used for adsorption and degradation of dyes.
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Metal oxides/ Mixed metal oxides have wide applications as catalyst, Adsorbents, Superconductors, semiconductors, ceramics, antifungal agents and also have spacious applications in medicines. This review article is focused on thei...
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Metal oxides/ Mixed metal oxides have wide applications as catalyst, Adsorbents, Superconductors, semiconductors, ceramics, antifungal agents and also have spacious applications in medicines. This review article is focused on their applications as sensors.
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Bulk V-P-O and model supported vanadia catalysts were investigated with in situ Raman spectroscopy during n-butane oxidation to maleic anhydride in order to determine the fundamental molecular structure-reactivity/selectivity insi...
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Bulk V-P-O and model supported vanadia catalysts were investigated with in situ Raman spectroscopy during n-butane oxidation to maleic anhydride in order to determine the fundamental molecular structure-reactivity/selectivity insights that can be obtained from such experiments. The in situ Raman studies of the bulk V-P-O catalysts provided information about the bulk crystalline phases, the hemihydrate precursor and its transformation to vanadyl pyrophosphate. However, the Raman experiments could not provide any molecular structural information about the amorphous and surface phases also present in this bulk metal oxide catalyst because of the strong Raman scattering from the crystalline phases. In contrast, in situ Raman studies of the model supported vanadia catalysts, where the active phase is present as a two-dimensional surface metal oxide overlayer, provided new insights into this important hydrocarbon oxidation reaction. In addition, the surface properties of the supported vanadia catalysts could be molecularly engineered to probe the role of various functionalities upon the structure-reactivity/selectivity relationship of n-butane oxidation to maleic anhydride. These fundamental studies revealed that the oxidation of n-butane required only one surface vanadia site and that the critical rate determining step involved the bridging V-O-P or V-O-support bonds. The selective oxidation of n-butane to maleic anhydride could occur over one surface vanadia site as well as multiple adjacent surface vanadia sites, but the reaction is more efficient with multiple sites. The n-butane oxidation TOF increased with the introduction of both surface Broensted and Lewis acid sites, but only the surface Lewis acid sites increased the maleic anhydride selectivity.
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Kevlar, poly(p-phenylene terephthalamide) (PPTA), yarns are modified for use as flexible supercapacitor electrodes by coating them with a nanometerscale film of conductive platinum metal and pseudocapacitive V_2O_5 using atomic la...
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Kevlar, poly(p-phenylene terephthalamide) (PPTA), yarns are modified for use as flexible supercapacitor electrodes by coating them with a nanometerscale film of conductive platinum metal and pseudocapacitive V_2O_5 using atomic layer deposition (ALD). The PPTA yarns are incorporated into a solidstate supercapacitor through the use of a polyvinyl alcohol/lithium chloride gel electrolyte. Pseudocapacitive V_2O_5 films 11 nm thick provide up to a 5× increase in areal capacitance (18.4 mF cm~(?2)) over the Pt-only-coated PPTA. Thicker films of V_2O_5 and wrapping the electrodes together into a single yarn result in decreased areal capacitance due to charge-transfer limitations. The work describes how ALD metal and metal oxide can be combined to add double layer and pseudocapacitive charge storage to mechanically robust PPTA creating unique multifunctional electronic fabric device systems.
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Active layers consisting of rf sputtered WO_3 were deposited on microhotplate substrates. The films were doped with seven different materials (Pt, Au, Ag, Ti, SnO_2, ZnO and ITO (indium tin oxide)). The eight types of sensors (inc...
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Active layers consisting of rf sputtered WO_3 were deposited on microhotplate substrates. The films were doped with seven different materials (Pt, Au, Ag, Ti, SnO_2, ZnO and ITO (indium tin oxide)). The eight types of sensors (including pure tungsten oxide ones) were tested in the presence of ammonia, hydrogen sulphide, nitrogen dioxide, carbon monoxide and methane. It was found that gold improved the sensitivity to H_2S. On the other hand, doping with Ag and Pt led to higher responses to NO_2 and NH_3, respectively. No response to CH_4 was observed. The sensitivity to CO was very low. The influence of the working temperature on the sensor response was also studied. Our study proves that selective gas detection is possible combining a few tungsten oxide sensors with different dopants.
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Metal/Mixed metal oxides have high surface area and more reactive sites.Surface area of the oxides depends on the mode of synthesis.Because of these properties metal oxides/mixed metal oxides have wide applications such as catalys...
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Metal/Mixed metal oxides have high surface area and more reactive sites.Surface area of the oxides depends on the mode of synthesis.Because of these properties metal oxides/mixed metal oxides have wide applications such as catalyst and adsorbents.Metal oxides also work as superconductors and semiconductors as they are conducting in nature.Metal oxides are being used in cosmetics as antifungal agents and also have large applications in medicines.One of the most attentive applications of metal/mixed metal oxides is as catalyst because of more reactive sites.This review article is focused on their applications as catalyst in various organic reactions.
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This manuscript deals with the preparation of graphen oxide ? metal oxide composite for the removal of heavy metal ions from water by adsoprtion. Composite of graphene oxide (GO) with zink oxide and titanium oxid
This manuscript deals with the preparation of graphen oxide ? metal oxide composite for the removal of heavy metal ions from water by adsoprtion. Composite of graphene oxide (GO) with zink oxide and titanium oxide has been prepared and analyzed structurally. Further, these composites has been used for the removal of heavy metals such as lead, chromium, mercury etc. from water. Metal oxide GO composites has been found efficient towards removal of heavy metal ions.
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The effect of surface and bulk potassium promotion on the transition metal oxides (Mn, Fe, Co) catalytic activity in catalytic soot oxidation was investigated. The surface promotion was obtained via incipient wetness impregnation,...
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The effect of surface and bulk potassium promotion on the transition metal oxides (Mn, Fe, Co) catalytic activity in catalytic soot oxidation was investigated. The surface promotion was obtained via incipient wetness impregnation, whereas the bulk promotion-nanostructuration- was obtained via wet chemical synthesis or solid state reaction leading to mixed oxide materials. The introduction of potassium into the transition metal oxide matrix results in the formation of tunneled or layered structures, which enable high potassium mobility. The structure of the obtained materials was verified by powder X-ray diffraction and Raman spectroscopy and the catalytic activity in soot oxidation was determined by TPO-QMS and TGA. It was found that the surface promotion does not alter the metal oxide structure and leads to either enhancement (Mn, Fe) or deterioration (Co) of the catalytic activity. Simultaneously, the catalytic activity in soot combustion of the potassium structured oxides is strongly enhanced. The most active, cobalt oxide based catalyst significantly lowers the temperature of 50 % of soot conversion by similar to 350 degrees C comparing to the non-catalyzed process. The study allows for the establishment of rational guidelines for designing robust materials for DPF applications based on ternary metal oxides.
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The inorganic metal oxides and graphene in the form of nanocomposites have excellent potential application towards various practical usages. In this review, we have discussed recent research on MO-specific transition metal oxides ...
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The inorganic metal oxides and graphene in the form of nanocomposites have excellent potential application towards various practical usages. In this review, we have discussed recent research on MO-specific transition metal oxides (TMO) (e.g., Ti, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, W) and rare earth metal oxides CREMO) (e.g., La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb) anchored on reduced graphene oxide (rGO) nanocomposites that are being developed for photochemical applications such as degradation of aqueous pollutants and electrochemical behaviour including supercapaciors, Li-ion energy storage, and sensing. Also, we have discussed some future nano MO/rGO composite materials.
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