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Tungsten oxide has a wide range of applications in chromic devices and catalysis. Effective control over the morphology of tungsten oxide remains a major challenge. Here, we present a facile pH-controlled strategy for synthesizing three-dimensional tungsten oxide architectures with different morphologies without using any templates or surfactants. These hierarchical architectures with rod-like, disk-like and sphere-like morphologies are assembled from one-dimensional tungsten oxide nanowires/nanorods. The influence of the single parameter of the pH value on the morphologies and crystal structures of tungsten oxide is systematically studied. The results indicate that different polytungstate anions obtained at various pH values give rise to different crystal nuclei by a dehydration process. These crystal nuclei grow into similar phases (crystal structures) but distinct morphologies via hydrothermal treatment. Here, the similarity of the crystal structures of h-WO3 and o-WO3·0.33H2O plays a key role in the structural transformation. Further experiments show that these three-dimensional tungsten oxide architectures display promising applications as catalysts in green chemistry for the oxidation of cyclohexene to adipic acid using an environmentally friendly oxidant (hydrogen peroxide). [ABSTRACT FROM AUTHOR]

Hydrogenation of unsaturated organosulfur compounds is an essential process through which these species are converted into cleaner and more useful compounds. Hydrogen bronze materials have been demonstrated to be efficient catalysts in hydrogenation of simple unsaturated compounds. Herein, we performed density functional theory calculations to investigate hydrogenation of thiophene on hydrogen tungsten bronze. Various reaction pathways were investigated and the most favourable routes were identified. Our results suggest that the reaction proceeds with moderate barriers, and formation of tetrahydrothiophene is facile both thermochemically and kinetically. The present study provides a useful insight into the design of hydrogenation thiophene and its derivatives and effective hydrodesulfurization catalysts. [ABSTRACT FROM AUTHOR]

We report here a novel proton exchange membrane with remarkably high methanol-permeation resistivity and excellent proton conductivity enabled by carefully designed self-assembled ionic conductive channels. A direct methanol fuel cell utilizing the membrane performs well with a 20 M methanol solution, very close to the concentration of neat methanol. [ABSTRACT FROM AUTHOR]

Well-defined and uniform double-walled Cu7S4nanoboxes with an average edge length of about 400 nm have been successfully synthesized by using Cu2O nanocubes as sacrificial template based on an inward replacement/etching method. The key step of the process involves repeated formation of Cu7S4layer in Na2S solution and dissolution of the Cu2O core in ammonia solution for two consecutive cycles. Experiments show that the time of dissolving Cu2O core with ammonia solution plays a key role in the preparation of double-walled Cu7S4. The as-prepared samples have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and photoluminescence analysis. NH3sensing properties of Cu7S4nanoboxes with single and double walls have been investigated at room temperature with a simply adapted photoluminescence-type gas sensor. The results revealed that the double-walled Cu7S4nanobox sensor exhibited enhanced performances such as higher sensitivity and shorter response time in ammonia gas sensing compared with the single-walled one. [ABSTRACT FROM AUTHOR]

Well-defined and uniform double-walled Cu(7)S(4) nanoboxes with an average edge length of about 400 nm have been successfully synthesized by using Cu(2)O nanocubes as sacrificial template based on an inward replacement/etching method. The key step of the process involves repeated formation of Cu(7)S(4) layer in Na(2)S solution and dissolution of the Cu(2)O core in ammonia solution for two consecutive cycles. Experiments show that the time of dissolving Cu(2)O core with ammonia solution plays a key role in the preparation of double-walled Cu(7)S(4). The as-prepared samples have been characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and photoluminescence analysis. NH(3) sensing properties of Cu(7)S(4) nanoboxes with single and double walls have been investigated at room temperature with a simply adapted photoluminescence-type gas sensor. The results revealed that the double-walled Cu(7)S(4) nanobox sensor exhibited enhanced performances such as higher sensitivity and shorter response time in ammonia gas sensing compared with the single-walled one.