| Recently, as a new semiconductor photocatalytic material, iron vanadate(FeVO4) has received increasing attention for potential applications in various fields due to its narrow band gap, higher light energy utilization, nontoxicity and easily recycles of magnetic property. Triclinic FeVO4 is an n-type semiconductor with a special layered structure consisting of three isolated VO4 units exhibiting important applications in catalysis and its layered structure can reduce the recombination rate of electrons and holes. Based on such characteristic of FeVO4, the synthesis of triclinic FeVO4 is favorable to enhance the light quantum efficiency and promote the activity of photocatalytic reaction.In this paper, FeVO4 and Fe2O3/FeVO4 heterojunctions powders were prepared by the hydrothermal method using FeCl3·6H2O and NH4VO3 as raw materials. The crystal structures, the morphologies, and the photophysical properties of the samples were all characterized by different measure techniques. The influence of the photocatalytic performances with pH values and nonmetal doping were evaluated by the decolorization of rhodamine B under UV-light irradiation. The results were as follows:The selective preparation of pure triclinic FeVO4 was obtained by adjusting the pH values of the precursor. The main crystalline phase changes from FeVO4 to α-Fe2O3 with the pH values increasing. The results show that the short rod-like FeVO4 with a pure triclinic structure can be obtained in the pH range of 2~4; the rod-like α-Fe2O3/FeVO4 heterojunctions can be obtained in the pH range of 5~8; the octahedron and disc-like α-Fe2O3 can be obtained at pH 10 and pH 12. The formation of α-Fe2O3 is calcined by the Fe(OH)3 gel formed from Fe3+ and OH-. At pH=5, the rod-like Fe2O3/FeVO4 heterojunction with remanent magnetization 0.268emu/g exhibits the best photocatalytic activity and the degradation rate of RhB after 180 min UV-light irradiation is 90%.The α-Fe2O3/Fe VO4-xNx heterojunctions were synthesized by the hydrothermal and calcining method using NaN3 as a nitrogen source. The N doping gives rise to the formation of rod-like heterojunctions, which exists between trigonal α-Fe2O3 and triclinic FeVO4. The surface Oads/Olatt molar ratios of α-Fe2O3/FeVO4-xNx(x=0.75) is 0.61. It demonstrates more oxygen vacancies appear in α-Fe2O3/FeVO4-xNx(x=0.75) heterojunction and the photoluminescence intensity is weak and the absorption edge is red-shifts. As a result, in α-Fe2O3/FeVO4-xNx heterojunction photocatalysts, the photogenerated electrons can be trapped by the surface oxygen vacancies caused by nitrogen incorporation, whereas the holes can be trapped by the organic on the surface, which reduces the recombination rate. The α-Fe2O3/FeVO4-xNx(x=0.75) heterojunction with the maximum content of α-Fe2O3(30.46%) shows the best photocatalytic activity under UV-light irradiation, which can efficiently catalyze the degradation of RhB up to 90% at 180 min. Furthermore, the high Ms value(20.78emu/g) of the α-Fe2O3/FeVO4-xNx(x=0.75) heterojunction is strong enough to maintain their good performance of magnetic recovery after the photocatalytic reactions.The α-Fe2O3/FeVO4-xCx heterojunctions were synthesized by the hydrothermal and calcining method using C6H12O6 as a carbon source. With N3-ions content increasing, the growth of FeVO4 crystal can be promoted and the α-Fe2O3 crystal can be restrained, meanwhile the remanent magnetization of α-Fe2O3/FeVO4-xCx heterojunctions can be enhanced. The α-Fe2O3/FeVO4-xCx(x=10%) heterojunction shows the best photocatalytic activity under UV-light irradiation, which can efficiently catalyze the degradation of RhB up to 82.03% at 180 min and 42.86% TOC removal is obtained. It can be found that no significant photoactivity loss is observed after four times of the photodegradation of RhB under the same experimental conditions. The results indicate that α-Fe2O3/FeVO4-xCx(x=10%) heterojunction is stable during the photodegradation of RhB. |
PDF Full Text Request