Morphology influence on photocatalytic activity of tungsten oxide loaded by platinum nanoparticles
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Jinhua Yea) International Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan; and Photocatalytic Materials Center, National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan (Received 12 May 2009; accepted 2 July 2009)
Photocatalytic activity of different morphologies of tungsten oxide was investigated before and after platinum loading. Different shape particles of tungsten oxide were synthesized using peroxo tungstic acid solution as a basic precursor and different methods. The prepared materials were composed of nanoparticles, nanorods, and nanosheets that formed different morphologies. The results of photodegradation with isopropyl alcohol (IPA) under visible light showed that the samples composed of nanostructures with an average lateral thickness of 20 to 47 nm were more active than one composed of broad nanosheets with a thickness of 60 nm. The samples were loaded with a platinum cocatalyst. The results of photocatalytic evaluation of loaded samples showed that the photooxidation reaction of samples with a smaller feature was accelerated with a higher rate rather than one with broad nanosheets. We conclude that although loading of a cocatalyst promoted the photocatalytic activity, it is not capable of compensating for the morphology influence on the photocatalytic activity. I. INTRODUCTION
Many semiconductor photocatalysts have been extensively investigated with the goal of developing catalysts for the decomposition of harmful organic substances under visible light irradiation.1–5 The reactions generally originate from excited electrons and holes created by absorption of photons with more energy than the band gap of semiconductors. The holes have a strong potential to draw electrons out of organic molecules, resulting in decomposition of hazardous materials, such as harmful gases, oil, and bacteria.6–9 The events that take place during a photocatalytic reaction are light absorption, photogenerated electronhole (e-h) separation–recombination, photogenerated charge carrier diffusion, and charge transport to the reactants. There are two types of parameters that affect the photocatalytic activity of a semiconductor. The first type is electronic parameters that are assigned by crystallinity and the electronic band structure of a photoa)
Address all correspondence to this author. e-mail: [email protected] This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http:// www.mrs.org/jmr_policy DOI: 10.1557/JMR.2010.0021 J. Mater. Res., Vol. 25, No. 1, Jan 2010
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catalyst material. Electronic parameters control light absorption, separation-recombination of photogenerated e-h and charge carrier diffusion. The other type of parameters are related to morphology such as particle shape and particle size, surface area and the crystalline planes exposed to the reactan
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