| With the deepening of semiconductor science research, people has been found that ZnO and SnO2 are two kinds of metal oxide semiconductor photocatalytic materials, more common and studied more. Among them, ZnO has become the main research target with its high efficiency in photocatalytic degradation of dye, because of non-toxic, morphological diversity, inexpensive, high photosensitivity and mild preparation conditions, and so on. However, a study shows, ZnO with wide band gap has some defects, such as low efficiency in the solar energy utilization, high recombination rate of photo-induced carrier and poor cycle stability. That greatly limits its practical application in the field of photocatalysis. Therefore, how to improve the photocatalytic activity of ZnO material has become the research highlights in the photocatalytic fields.In this paper, C-doped ZnO samples of different morphologies were synthesized by using a hydrothermal assisted calcination method with Zn(NO3)2·H2O, trisodium citrate citric acid and Na OH as raw materials, adding different carbon source(glucose, glycol and soluble starch). The morphology, composition and structure of the prepared C-doped ZnO samples were characterized by XRD, SEM, FTIR, UV-vis and PL. The photocatalytic properties and degradation kinetics of the prepared C-doped ZnO samples were evaluated using the prepared C-doped ZnO photocatalysts with Reactive Black GR as simulated dye wastewater. The main research contents and results are as follows:1. C-doped ZnO samples of different morphologies were successfully synthesized with ethylene glycol as carbon source. By controlling the reaction solution pH and the addition ratio of ethylene glycol, the photocatalytic degradation performance of the C-doped ZnO material under different preparation conditions was studied. The results indicated that C-doped ZnO samples showed the better photocatalytic activity than that of pure ZnO under the visible light irradiation. Especially C-doped ZnO sample prepared with the reaction solution pH=12, ethylene glycol amount to 30 ml, showed the highest photocatalytic activity for the degradation of Reactive Black GR solution, reaching the rate of 97% in 60 min. This may be attributed to its rod composed flower-like morphology, the high separation efficiency of photo-generated e--h+ and smaller band gap.2. C-doped ZnO samples with different morphologies were prepared with glucose as carbon source. After a series of characterization, C is doped into Zn O. The morphology of C-doped ZnO samples were influenced by the reaction solution pH value, dosage of glucose and hydrothermal temperature. The possible growth mechanism of C-doped ZnO samples were proposed. The photocatalytic performance of the samples at different preparation conditions were evaluated by degrading Reactive Black GR solution under visible light irradiation. The results showed that the sample under the optimal preparation technology of C-doped at pH=12 of reaction solution, 2M of glucose, 150 ℃ hydrothermal 10 h, reveal the higher photocatalytic activity, which the degradation ratios could reach 96 % in 60 min.3. C-doped ZnO samples with different morphologies were prepared with soluble starch as carbon source. The morphology of C-doped ZnO samples were effected by the reaction solution pH value, dosage of soluble starch and hydrothermal time. The photocatalytic activity of the samples at different preparation conditions were tested by degrading Reactive Black GR solution under visible light irradiation. The results showed that C-doped ZnO sample prepared with the reaction solution pH=12, the starch content of 0.1 g, hydrothermal time for 10 h displayed higher photocatalytic activity than the other samples, which the degradation ratios could reach 99 % in 60 min. This may be due to the doping suitable content of C that not only make a response to visible light response, but also can reduce the band gap, increasing the concentration of oxygen deficiency and improving the separation efficiency of photo-generated e--h+, which could improve the photocatalytic activity.4. SnO2 powders were prepared with SnCl2·2H2O and citric acid as raw materials by the hydrothermal assisted calcination process. The prepared powders were characterized by XRD and SEM. It can be known that the samples are self-assembed into the hollow microsphere, and keep the tetragonal crystal structure of rutile. The photocatalytic activity of SnO2 powders were evaluated by degrading Reactive Black GR solutions under UV irradiation, and its photocatalytic degradation mechanism is discussed. |
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