Preparation, characterization and photocatalytic activity of nono-sized ZnO/SnO_2 coupled photocatalysts

摘要

The nano-sized coupled oxides ZnO/SnO_2 in a molar ratio of 2:1 (Z_2S) and 1:1 (ZS) were prepared using the co-precipitation method and characterized with X-ray diffraction (XRD), UV-VIS diffuse reflectance spectroscopy and specific surface area (Brunauer-Emmett-Teller (BET)). Their photocatalytic activities were also evaluated using methyl orange (MO) as a model organic compound. The isothermal adsorption behavior of MO on Z_2S and the factors affecting the photocatalytic activity, such as the heat-treating temperature for the photocatalyst, the pH value of the reaction suspension and the addition of NaCl, KNO_3 and K_2SO_4 into the suspension, have been studied. It is found that the cange in phase of Z_2S occurs with the calcination temperature. The band gap energy value observed by UV-VIS diffuse reflectance spectroscopy is 3.15 eV for Z_2S compared with those of 3.12 eV for ZS, 3.17 eV for ZnO and 2.53 eV for SnO_2. The isothermal adsorption behavior is a two-stage process. The photocatalytic degradation rate fo MO on Z_2S is faster than that on ZS and ZnO by 40.2 and 66.1%, respectively. A schematic diagram of photocatalytic activity is also presented to explain the results.