Influence of temperature on the morphology and photocatalytic activity of ZnGa2O4 crystallites prepared by hydrothermal method

ZnGa2O4 crystallites were synthesized via a hydrothermal method in the temperature between 160 °C and 200 °C at the pH of 13.5 using ZnSO4·10H2O and Ga2O3 as source materials. The phase and microstructure of the as-prepared ZnGa2O4 crystallites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It is found that the nano-spheric ZnGa2O4 crystallites can be synthesized at the temperature of 160 °C, while the assembled three-dimensional structure of the ZnGa2O4 crystallites can be achieved at 170–200 °C. In addition, the growth mechanisms of nano-spheric and three-dimensional structure of the ZnGa2O4 crystallites are preliminarily discussed and it is found that the ZnGa2O4 nucleation rate was controlled by the formation of Ga(OH)4−. The photocatalytic activity of ZnGa2O4 crystallites was evaluated using Rhodamine B (RB) as a model pollutant. Results showed that the photocatalytic activity of the ZnGa2O4 crystallites can be significantly decreased and the areal activity of them are increased by increasing the temperature from 160 °C to 200 °C, which may be caused by the improved crystallization and a cuboid-like morphology. The best photodegradation efficiency was shown by the sample prepared at 160 °C and the degradation efficiency of Rhodamine B was 98.4% in 60 min.