Abstract
Herein, we report a facile synthesis method for mesoporous TiO2 nanocrystals using the F127 tri-block copolymer as a template. Then, precious metals (Au, Pd and Pt) have been photodeposited onto mesoporous TiO2. The prepared photocatalysts have been compared with Aeroxide TiO2 P-25 by the determination of the formation rate of HCHO generated by the photooxidation of CH3OH. The TEM results indicated that the lattice fringes exhibit the typical distances, TiO2 (1 0 1) (3.54 angstrom) and TiO2 nanoparticles with an average diameter of 10 nm particles are not agglomerated and quite uniform in size and shape. TEM images of mesoporous Pd/TiO2, Pt/TiO2 and Au/TiO2 clearly show Pd, Pt and Au nanoparticles are well dispersed and exhibit diameters of 12, 3 and 5 nm, respectively. The dependence of HCHO formation rate on the precious metals/TiO2, behaves quite differently depending on types of precious metals as electrons sink. The photocatalytic efficiency of mesoporous TiO2 has been enhanced by photodeposition of Au, Pt and Pd in the order Pd > Pt > Au. The increased photocatalytic activity of Pd/TiO2 more than either Pt/TiO2 or Au/TiO2 can be attributed to the density of states in the vicinity of the Fermi level of Pd is high and consists mainly of contributions from d electrons. To the best of our knowledge, the measured photonic efficiency xi = 17.8 of Pd photodeposited onto mesoporous TiO2 is found to be among the highest xi-values reported up to now. (C) 2012 Elsevier B.V. All rights reserved.