We used polyisoprene-block-ethyleneoxide copolymers as structure-directing agents to synthesise well-ordered and highly-crystalline mesoporous WO 3 architectures that possess improved photocatalytic properties due to enhanced dye-adsorption in absence of diffusion limitation.As a green technology, semiconductor photocatalysis has attracted increasing interest driven by the search for new energy sources during the past few decades.1 The performance of the photocatalysts strongly depends on their crystal structure and morphology.1,2 It is widely recognized that high crystallinity and a continuous network architecture with controlled pore sizes that facilitate molecular access to high surface areas are highly desired for maximizing their photocatalytic performance. 3,4 This has recently stimulated intensive research in designing mesoporous metal oxides, such as TiO 2 , Nb 2 O 5 , and ZrO 2 . 5 The major drawback of these attempts is that the oxide structures often contain a significant amount of undesired amorphous content, which facilitates the recombination of electrons and holes, thereby limiting the catalytic efficiency.2 The crystallinity can be improved by annealing at high temperatures, upon which, however, the ordered structure typically collapses. Hence, synthesising well-ordered mesoporous structures with high crystallinity still remains a major challenge. 6 Recently, we used polyisoprene-block-ethyleneoxide (PI-b-PEO) copolymers as structure-directing agents to synthesise TiO 2 with controlled mesoporous structures. 7,8 The large interaction parameter between the PI and PEO blocks and the high degree of polymerization allows the rapid formation of structures with long-range order. In addition, the PI-b-PEO morphology has relatively large pore sizes, which facilitate the effective infiltration of functional materials. The resulting TiO 2 exhibited excellent performance in dye-sensitized solar cells. Although TiO 2 is currently the most studied semiconductor photocatalyst, its wide band gap (3.2 eV) limits TiO 2 to a small ultraviolet fraction of solar energy. 9 In contrast, tungsten trioxide (WO 3 ) has a narrower band gap (2.4-2.8 eV) that enables harvesting visible light.10 Only a few studies have so far been devoted to the synthesis of porous WO 3 , i.e. using PMMA spheres 11 and by anodization of tungsten foil. 12 Despite yielding only macroporous and weakly-ordered structures these studies still demonstrated enhanced photocatalytic properties compared with their dense counterparts. It is therefore likely that improving the pore structure and crystallinity will maximise the photocatalytic performance of WO 3 . Herein, we demonstrate the synthesis of highly-crystalline mesoporous WO 3 with well-ordered pore architectures using a sol-gel process and PI-b-PEO copolymers as structure-directing agents. We investigated the effect of polymer-to-WO 3 weight ratio on the morphology and tested the photocatalytic performance for the degradation of methylene blue under visible light.In a typical synthesis, 45 mg ...

No abstract

No abstract

Ultra‐fine composite fibers made from poly(vinyl alcohol) (PVA)/silatrane, an inexpensive and moisture‐stable silicon‐containing compound, were prepared by a combined sol–gel processing and electrospinning technique with average diameters ranging between 119 and 405 nm. These fibers were subsequently converted to ultrafine silica fibers by calcination treatment, with the aim of producing a silica structure with a high surface area‐to‐mass ratio. Upon calcination at 500°C, the PVA/silica composite fibers were converted into amorphous silica fibers, while calcination of the composite fibers at temperatures ≥700°C resulted in the formation of cristobalite fibers. The average diameter of these silica fibers ranged between 162 and 213 nm.

No abstract