Photoelectrochemical behavior of composite metal oxide semiconductor films with a WO 3 matrix and occluded Degussa P 25 TiO 2 particles

Abstract

This paper describes the photoelectrochemical (PEC) behavior of composite semiconductor films containing Degussa P 25 TiO 2 particles dispersed in a WO 3 matrix. These films (hereafter designated as “WO 3–TiO 2”) were electrosynthesized using occlusion electrodeposition from a bath contained suspended TiO 2 particles and peroxytungstate precursor species. One focus of this study was the effect of pre-calcination of the TiO 2 particles (prior to their incorporation into the WO 3 film matrix) on the PEC behavior of the resultant composite film. The PEC activity and selectivity of the composite films and their dependence on the pre-calcination temperature were studied in aqueous media containing formate ions as additives in some cases. Another focus of this study was the role of the WO 3 matrix itself and how the oxide matrix compares with a metallic (e.g., Ni) counterpart. Finally, the photoaction spectra of the WO 3–TiO 2 composite films were simulated by a modified diffusion model, previously developed by Södergren et al. [J. Phys. Chem. 98 (1994) 5552] for microporous semiconductor films. Good agreement was found between the model simulations and experimental photoaction spectra. These simulations confirmed the ability of the WO 3 component to accept the photogenerated electrons from the TiO 2 component in the composite films and thereby improve the quantum yield.