表面水热碳层对磁性NiFe2O4八面体光催化活性的影响

采用葡萄糖水热碳化法合成了一系列碳层包覆的NiFe₂O₄核壳八面体(NiFe₂O₄@C). 通过调控葡萄糖的含量可以有效控制NiFe₂O₄表面包覆的碳层厚度. 利用X射线衍射(XRD)、 拉曼光谱(Roman)、 X射线光电子能谱(XPS)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)和紫外-可见漫反射光谱(UV-Vis DRS)等对NiFe₂O₄@C的组成、 结构、 形貌和光学性能进行了表征. 考察了表面水热碳层对NiFe₂O₄光催化降解亚甲基蓝(MB)性能的影响. 结果表明, NiFe₂O₄的光催化活性很大程度上依赖于在其表面包覆的碳层厚度, 碳层厚度为5.5 nm的NiFe₂O₄@C-3展现了最佳的光催化活性. 荧光光谱(PL)、 瞬态光电流和电化学阻抗谱(EIS)表征结果证明, NiFe₂O₄@C的光催化性能的提升归因于在NiFe₂O₄核和碳壳之间形成了异质结, 有效地促进了光生载流子的传输和分离效率. NiFe₂O₄@C复合材料展现了较好的稳定性和可回收性, 在污水处理方面有很大的应用潜力.

Effects of Surface Hydrothermal Carbon Layer on the Photocatalytic Activity of Magnetic NiFe2O4 Octahedron

A series of magnetic carbon-coated NiFe₂O₄ core-shell octahedron（NiFe₂O₄@C） was synthesized by hydrothermal carbonization of glucose. The thickness of carbon layer on the NiFe₂O₄ surface could be precisely tuned by controlling the content of glucose. The composition， structure， morphology and optical properties of NiFe₂O₄@C composites were characterized by X-ray diffraction（XRD）， Raman spectroscopy（Roman）， X-ray photoelectron spectroscopy（XPS）， scanning electron microscopy（SEM）， transmission electron microscopy（TEM） and UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）. The photocatalytic performance for the MB-degradation of various NiFe₂O₄@C were explored. It is found that the photocatalytic activity strongly depended on the thickness of carbon layer on the surface of NiFe₂O₄. The NiFe₂O₄@C-3 with 5.5 nm carbon layer is endowed with the best photocatalytic performance for the MB photodegradation. Fluorescence spectroscopy（PL）， transient photocurrent and electrochemical impedance spectroscopy（EIS） results show that the improvement of photocatalytic performance can be attributed to the formation of the heterojunction between the NiFe₂O₄ core and carbon shell， which effectively promotes the transmission and separation of photo-generated carriers. In addition， NiFe₂O₄@C possesses relatively high stability and retrievability， indicating that NiFe₂O₄@C has great potential for applications in sewage treatment.