Preparation characterization and photocatalytic activity of polycrystalline ZnO/TiO2 systems. 1. Surface and bulk characterization

Polycrystalline ZnO/TiO2 solids have been prepared with four different meth ods using home prepared Tin, (anatase) or TiO2 (rutile) as supports and Zn( NO3)(2). 6H(2)O or Zn(CH3COO)(2). 2H(2)O as precursors for ZnO. The bulk an d surface properties of the samples were investigated by means of TG-DTA, X RD, TEM, SEME-DAX, XPS, BET surface area determination, and porosity measur ements. XRD and TEM results indicate that no significant defect structures exist in any of the samples. The ZnO crystallinity and its enrichment on th e surface of TiO2 particles were dependent on the preparation method. The s urface areas generally decrease by increasing the amount of ZnO except when ZnO from Zn(CH3COO)(2). 2H(2)O was supported on TiO2 (rutile). The samples prepared from Zn(CH3COO)(2). 2H(2)O were more porous than those prepared f rom Zn(NO3)(2). 6H(2)O. This was confirmed by BET surface area determinatio ns and SEM observations. XPS spectra indicate that the atomic ratio between OH- and O2- 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 fur samples obtained b y using the acetate precursor.