David G Calatayud
Instituto de Ceramica y Vidrio – CSI, Spain
Title: Band-gap engineering and morphological control of TiO2 nanoparticles by a semisolvothermal route
Biography
Biography: David G Calatayud
Abstract
TiO2 has become a material of great interest for photocatalytic H2 production, environmental purification and solar energy conversion.[1] It is generally accepted that anatase is the most active photocatalyst of the three possible polymorphs of TiO2. The properties influencing the photoactivity of anatase particles have been reported to include surface area, crystallinity, crystallite size, crystal structure;[2,3] and the morphology of the particles. Among the key parameters boosting the photocatalytic efficiency of anatase nanoparticles, an increased light absorption to extend the optical response to the visible, together with an improved charge separation of the electrons and holes generated upon photoexcitation, shall be enumerated. Conventional TiO2 anatase nanoparticles have a bandgap of 3.20 eV which only allows the excitation of carriers by light with wavelengths smaller than 387 nm (UV region); if visible light harvesting is to be enabled, this gap should be narrowed. In this work, pure anatase nanoparticles have been obtained using a solvothermal process with reduced band-gap and/or reactive faces. Trifluoroacetic acid is used as morphological control and doping agent, and urea is employed as a reduction agent.[4,5] Through the careful choice and control of the working conditions, it is possible to control the final properties of the produced nanoparticles, e.i. morphology, size, crystallinity, crystal phase, network defects and band gap. The obtained results point out that in order to improve the photocatalytic performance, a well-designed intrinsic defective TiO2 system for visible light driven photocatalysis should meet all three requirements simultaneously: (i) reduced band gap for visible light absorption, (ii) appropriate energy level to initiate photocatalytic reaction, and (iii) proper defect species or highly active surfaces to separate photo-generated charge-carriers (electrons and holes) for reaching high catalytic performance.