Influence of Ti(IV) on the structure and properties of zinc hydroxychloride

Layered material of zinc hydroxychloride (Zn5(OH)8Cl2 · H2O: ZHC), which is one of the basic zinc salts (BZS), prepared from ZnO nano-particles aged with aqueous ZnCl2 solutions containing TiCl4 was examined by various means. The Ti/(Ti + Zn) atomic ratio (XTi) was ranged from 0 to 0.10. XRD results indicated that the diffraction intensity of ZHC was decreased with increasing XTi. The ZHC formed at XTi = 0 is hexagonal plate particles with ca. 4 μm in size and ca. 0.2 μm in thickness. The particle size was reduced by doping Ti(IV) and the irregular particles were generated at XTi ⩾ 0.03. The Ti content was increased with increasing XTi and Ti(IV) was more easily incorporated in the products than Zn(II). Diffuse reflection UV-vis results suggested that Ti(IV) in the products at XTi ⩽ 0.01 is tetrahedral coordination and that at XTi ⩾ 0.03 is a mixture of tetrahedral and octahedral ones. These facts prove that Ti(IV) inhibits the formation and crystal growth of ZHC. The specific surface area of Ti-doped ZHC estimated from N2 adsorption isotherms was increased with increasing XTi owing to the decrease of particle size. Contrary to the N2 adsorption, H2O monolayer adsorption capacity per unit surface area was reduced as XTi increased. This seems that the layered structure of ZHC, which is accessible to H2O molecules but not to N2 molecules, is disintegrated by incorporation of Ti(IV). Similarly, adsorption of CO2 on ZHC was inhibited by doping Ti(IV).