The Kinetics of Palladium Reduction at Particulate TiO₂ Photocatalysts

Abstract

Thin films of TiO2 were prepared by the hydrolysis of tetraisopropyl titanate (TIPT) which was applied to quartz substrates by spin coating. Microscopic examination revealed an array of TiO2 particles, rather than a continuous film. The physical properties of the TiO2 were examined as a function of annealing temperature. Unannealed films were found to be amorphous and microporous while those annealed for 1h at 500°C were fully densified and crystallized. The photocatalytic reduction of Pd, from an aqueous PdCl2 solution, at the Ti02 surface was studied as a function of annealing temperature. The metal deposition rate was determined to be higher for annealed films and TEM showed fewer nucleation sites with much larger sized deposits than those obtained with unannealed films. The metal deposition behavior is explained by the presence of a Schottky barrier at the metal/semiconductor interface, although the unannealed films are dominated bv their microporous nature. Nb doping (n-doping) of the films resulted in enhancement of the deposition rate for annealed films but had no effect on unannealed films. © 1987, The Electrochemical Society, Inc. All rights reserved.