Morphology-controlled synthesis of W18O49 nanostructures and their near-infrared absorption properties.
ABSTRACT The morphology-controlled synthesis and near-infrared (NIR) absorption properties of W(18)O(49) were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W(18)O(49), such as nanorods, nanofibers, nanograins, nanoassembles, nanoplates, and nanoparticles, with various sizes were successfully synthesized by solvothermal reactions using organic alcohols as reaction media and WCl(6), W(EtO)(6), and WO(3) solids as the tungsten source. W(18)O(49) nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which realized high transmittance in the visible region as well as excellent shielding properties of NIR light. Meanwhile, the W(18)O(49) nanorods also exhibited strong absorption of NIR light and instantaneous conversion of the absorbed photoenergy to the local heat.
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ABSTRACT: Mesoporous hollow W18O49 spheres were fabricated by a facile solvent-induced assembly method using anhydrous WCl6 as a precursor and CH3COOH as a solvent. This unique structure exhibited remarkably enhanced photocatalytic and photoelectrocatalytic performance than other morphologies like urchin and nanowire due to the simultaneous enhancement in light harvesting, surface area and adsorption capability.Chemical Communications 07/2014; · 6.38 Impact Factor
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ABSTRACT: Top-down nanostructure engineering and band engineering are promising methods for fabricating efficient photocatalysts with enhanced optical and electronic properties; however, composites with simultaneously engineered structure and band are very rare. Herein, we constructed a unique architecture composed of a W18O49 nanowire alignment core and porous BiOCl shell (WA@BiOCl), which combined the advantages of both an assembly structure and a type II core-shell heterojunction. The W18O49 alignments (WA) were synthesized using a "one-pot" solvothermal treatment of WCl6/NaNO3via NO3(-)-mediated assembly, whereas the W18O49 nanowires with BiOCl shell (W@BiOCl) were obtained using WCl6/BiCl3. Then, WA@BiOCl, in contrast to W@BiOCl alignments, were fabricated when WCl6 and Bi(NO3)3 were present in the starting mixture. Optical absorption, photoelectrochemical measurements and photoluminescence characterizations show that either the alignments or the core-shell heterojunctions can enhance light harvesting, photo-charge transfer and collection. As a synergetic result, the WA@BiOCl architecture exhibited very high photoactivity and photostability. Under UV-vis (or vis) irradiation, WA@BiOCl is 2.43 (1.93), 3.93 (2.73) and 5.34 (3.44)-fold more active than W@BiOCl, WA and W18O49, respectively. The results demonstrate that the simultaneous nanostructure and band engineering can produce a more efficient photocatalyst than a single strategy alone, which suggests a potential method for the fabrication of photocatalysts in the fields of environment and energy.Nanoscale 06/2014; · 6.73 Impact Factor
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ABSTRACT: Development of Pt-free catalyst materials for the counter electrode (CE) in dye-sensitized solar cells (DSSCs) has been regarded as one of the crucial steps to improving energy conversion efficiency and cost effectiveness of DSSCs. In this work, low cost tungsten oxide (WO 3-x) counter electrodes, prepared by annealing tungsten metal sheets under an Ar and low O 2 atmosphere, exhibited high catalytic activity and energy conversion efficiency. The highest efficiency achieved here for DSSCs with WO 3-x counter electrodes, was 5.25%, obtained from a 500 C annealed tungsten sheet. TEM and XPS analysis suggested the formation of sub-stoichiometric tungsten oxide layer ($WO 2.6) with the presence of W 6+ , W 5+ and W 4+ oxidation states at the tungsten metal surface after the 500 C annealing. Only W 6+ and W 5+ oxidation states were detected after a 600 C annealing indicating the formation of a more stoichiometric tungsten oxide layer ($WO 2.8) and resulting in a drop in efficiency of the DSSC. We suggest that mixed valence tungsten states account for the excellent catalytic activity and good electrical conductivity as evidenced by the highest cyclic voltammetry response of 0.76 mA/cm 2 and the lowest impedance value of 44.33 V, respectively.Electrochimica Acta 09/2014; 145:27-33. · 4.09 Impact Factor