| A series of Zn/Al and Zn/Ti hydrotalcite-like compounds was prepared by urea method and their composite oxides were obtained after calcined at different temperature. The structure, morphology, thermal and optical properties, adsorption property of the products was characterized by XRD, TEM, SEM-EDX, FT-IR, UV-VIS-DRS, TG-DTA, BET and ICP-AES techniques. Zinc aluminate spinel and cubic zinc titanite spinel were synthesized from Zn/Al and Zn/Ti hydrotalcite-like compounds, respectively. The photocatalytic activity of ZnO/ZnAl2O4composite oxides was tested using methyl orange(MO) as the model reaction. The Dye-sensitized solar cells with Zn/Ti composite oxide as anode material were prepared. The research results showed that:(1) The synthetic Zn/Al hydrotalcite-like compounds at initial Zn/Al molar ratio of0.25-8were synthesized by urea method. The interlayer spacing of the prepared Zn/Al hydrotalcite-like compounds was calculated between0.752and0.763nm, indicated that the interlayer anions was carbonate. Pure hydrotalcite-like phase was obtained for initial Zn/Al ratios of0.5,1and2. The low (0.25and0.33) and high (3,4,6and8) initial Zn/Al molar ratio resulted in the formation of ZnAl-CO32--HTLCs with AlOOH and Zn4(CO3)(OH)6·nH2O respectively. The crystallinity of the Zn/Al hydrotalcite-like compounds could be improved via increasing the urea content or prolonging the reaction time. The thermal stability of the Zn/Al hydrotalcite-like compounds increased with the Zn/Al molar ratio.(2) The element analysis of Zn/Al hydrotalcite-like compounds at initial Zn/Al molar ratio of0.5gives the following formula:ZnAl2.08(OH)624(CO3)·0.8H2O and ZnAl2O4spinel with pure phase was obtained by calcining it at600℃or above. Specific surface area of sample heat-treated at700℃for1h is45.6m2g-1and decreased at higher calcined temperatures.The UV-VIS-DRS results indicated that the band gap (Eg) value of ZnAl2O4prepared at900℃was in the range of3.8-4.0eV.(3) The photocatalytic experiment proved that the methyl orange could be effectively degraded under UV-irradiation with ZnO/ZnAl2O4composite oxides as catalysis. The data showed that the ZnO/ZnAl2O4composite oxides with initial Zn/Al molar ratio of2had the most effective catalytical activity.(4) Zinc titanite spinel (Zn2TiO4) spinel has been prepared using a Zn/Ti hydrotalcite-like compounds as precursor. This approach involves calcination of precursor at600℃or above, followed by selective leaching of the self-generated zinc oxide template from the resultant calcined products. The BET results showed that the Zn2TiO4obtained at700℃had a high surface area of63.2m3/g. The UV-VIS-DRS results indicated that the band gap (Eg) value of Zn2TiO4prepared at900℃was around3.7eV.(5) The Zn/Ti composite oxides obtained at different temperature (500,600and700℃) was used to preparing Dye-sensitized solar cells, and the main conversion efficiency of the cells was0.691%,0.572%and0.302%respectively. The results indicated that the ZnO/Zn2TiO4composite oxide from Zn/Ti hydrotalcite-like compound was a potential anode material for Dye-sensitized solar cells. |
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