Photocatalytic metamaterials: TiO2 inverse opals
ABSTRACT The study of the photocatalytic activity of TiO(2) inverse opals showed that these structures behave as metamaterials: their properties arise principally from the 3D periodic structure of the material and marginally from porosity, reflectivity and scattering.
- SourceAvailable from: Claudio MineroMolecular Photochemistry - Various Aspects, 03/2012; , ISBN: 978-953-51-0446-9
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ABSTRACT: Conversion of energy from photons in sunlight to hydrogen through solar splitting of water is an important technology. The rising significance of producing hydrogen from solar light via water splitting has motivated a surge of developing semiconductor solar-active nanostructures as photocatalysts and photoelectrodes. Traditional strategies have been developed to enhance solar light absorption (e.g., ion doping, solid solution, narrow-band-gap semiconductor or dye sensitization) and improve charge separation/transport to prompt surface reaction kinetics (e.g., semiconductor combination, co-catalyst loading, nanostructure design) for better utilizing solar energy. However, the solar-to-hydrogen efficiency is still limited. This article provides an overview of recently demonstrated novel concepts of nanostructure designs for efficient solar hydrogen conversion, which include surface engineering, novel nanostructured heterojunctions, and photonic crystals. Those first results outlined in the main text encouragingly point out the prominence and promise of these new concepts principled for designing high-efficiency electronic and photonic nanostructures that could serve for sustainable solar hydrogen production.07/2012; 1(1):31-50. DOI:10.1515/nanoph-2012-0010
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ABSTRACT: Porous TiO2 microspheres with robust texture and high photoactivity were prepared by inflowing a TiO2 precursor in the confined space of polystyrene-co-divinyl benzene (PS-co-DVB) polymer, working as sacrificial scaffold. The impregnated polymer spheres, upon thermal treatments under N2, N2/air or pure air flow at temperatures in the 400–500 °C interval, are transformed into porous microspheres. Depending on the gas flow composition, the obtained microspheres are constituted by porous carbon, hybrid core–shell C/TiO2 or of cemented TiO2 nanoparticles assembled in elongated pillars. The composition of pure TiO2 microspheres ranges from pure anatase (400 °C) to the prevailing rutile phase (>475–500 °C). All samples have been extensively characterized by means of SEM/AFM microscopes, N2-volumetric porosimetry, XRD and UV–vis analyses. The photodegradation of NO has been used to check the photocatalytic activity of the TiO2 materials. It is concluded that they exhibit higher photoactivity than the classical benchmark material (Degussa P25). This property together with porous character of the microspheres, the tunable anatase–rutile ratio and the high crystallinity makes these microspheres very interesting materials for applications in photocatalysis. From a physical point of view, the large axial pores and the columnar nature of the spheres can produce the entrapment of the light into the material.Journal of Photochemistry and Photobiology A Chemistry 08/2012; 242:51–58. DOI:10.1016/j.jphotochem.2012.05.020 · 2.29 Impact Factor