In this study, the structure and photoelectrochemical properties of CuWO 4 porous films synthesized by a co-precipitation method followed by a hydrothermal treatment were investigated. The film was deposited on fluorine-doped tin oxide (FTO)-conducting glass, from a suspension containing polyethylene glycol, and heat-treated at 500 C for 30 min. X-ray diffraction patterns, the Rietveld refinement data, and the micro-Raman spectrum showed that the CuWO 4 film has a triclinic structure. The optical band gap energy of the film was estimated to be 2.45 eV by the Tauc plot. Field emission scanning electron microcopy images of the films indicated that they are about 4.0 AE 0.5 mm thick. The photoelectrochemical properties of the film were investigated in a Na 2 SO 4 aqueous solution, in the absence of light and under polychromatic irradiation. The CuWO 4 film exhibited photoelectrochemical behavior of a n-type semiconductor, with a negative photopotential and an anodic photocurrent density of 68 mA cm À2 at 0.73 V vs. Ag/AgCl (1.23 V vs. RHE). The n-type photoelectrochemical behavior was confirmed by a chronoamperometry measurement biased condition at + 0.7 V, at different pH values. From these studies, it was noted that when the pH values increased from 3 to 11, the photocurrent density increased about 9 times. Also, the flat band potential (E fb) of the semiconductor was estimated by the Butler-Gärtner model at + 0.34 V, which was utilized to calculate the conduction band edge. The studies presented here reveal that the CuWO 4 porous film is a promising candidate to be applied as a photoanode in photocatalytic processes under irradiation by visible light.

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In this communication, we report the growth of pure gamma-phase tungsten oxide (γ-WO 3 ) films on a conducting substrate (fluorinedoped tin oxide), followed by heat treatment at 500°C for 2 h, and finally modification with either silver (Ag 0 ) or platinum (Pt 0 ) metallic nanoparticles. These γ-WO 3 thin films can be obtained from a tungsten citrate solution by a drop-coating method, and their surfaces are modified with Ag 0 and Pt 0 nanoparticles by photoreduction. X-ray diffraction analysis indicates that all the thin films have a monoclinic structure. Field emission-scanning electron microscopy analysis reveals large and fine grains for pure γ-WO 3 film and modified WO 3 films, respectively, with an average grain size of~48 nm and thickness of~986 nm. Finally, an enhancement in photoelectrochemical performance by a factor of~2.5 is noted to modified γ-WO 3 films, which is attributed to superior electron-hole charge recombination lifetime under polychromatic irradiation. It is observed that, even under bias, an exponential reduction in photocurrent intensity is associated with charge recombination instead of mass transport conditions like diffusion. Keywords γ-WO 3 films . Ag 0 /Pt 0 nanoparticles . Recombination lifetime . Transient photocurrent

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SBA-15 molecular mesoporous sieve has attracted great interest of researchers since its discovery in 1998, owing large area surface, well-defined pores, uniform pore size, high thermal and hydrothermal stability, well-defined pore structure and ability to be functionalized with diverse metal oxides (active phase of catalyst). This work contains a brief review of the main SBA-15 functionalization methods: direct synthesis, post-synthesis or post-grafting, deposition-precipitation, graft hybrid, colloid immobilization and nanoparticle encapsulation showing the advantages and disadvantages of each. We also approach some synthetic strategies to overcome the shortcomings of the mentioned methods, as well as some parameters to choose the best method. Here, we showed that these methods don't provide the functionalization of SBA-15 keeping all the peculiar properties of support and that the new strategies or alternatives routes are important to overcome some challenges of the functionalization of SBA-15. This is a challenging point that needs to be further explored by promoting greater advances in materials science and catalysis.

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