Preparation Characterization and Photocatalytic Activity of Polycrystalline ZnO/TiO2 Systems. 1. Surface and Bulk Characterization

Abstract

Polycrystalline ZnO/TiO 2 solids have been prepared with four different methods using home prepared TiO 2 (anatase) or TiO 2 (rutile) as supports and Zn(NO 3 ) 2 ·6H 2 O or Zn(CH 3 COO) 2 ·2H 2 O as precursors for ZnO. The bulk and surface properties of the samples were investigated by means of TG-DTA, XRD, TEM, SEM-EDAX, XPS, BET surface area determination, and porosity measurements. XRD and TEM results indicate that no significant defect structures exist in any of the samples. The ZnO crystallinity and its enrichment on the surface of TiO 2 particles were dependent on the preparation method. The surface areas generally decrease by increasing the amount of ZnO except when ZnO from Zn(CH 3 COO) 2 ·2H 2 O was supported on TiO 2 (rutile). The samples prepared from Zn(CH 3 COO) 2 ·2H 2 O were more porous than those prepared from Zn(NO 3 ) 2 ·6H 2 O. This was confirmed by BET surface area determinations and SEM observations. XPS spectra indicate that the atomic ratio between OH - and O 2- on the particles surface is similar for samples with the same ZnO content independent of the precursor used for the samples' preparation. Moreover a much higher segregation of ZnO was found for samples obtained by using the acetate precursor.