Bin Tang

Fabrication of magnetically separable NiFe2O4/BiOI nanocomposites with enhanced photocatalytic performance under visible-light irradiation

A series of novel flower-like NiFe2O4/BiOI (NFO/BOI) nanocomposites have been synthesized via a facile solvothermal method. The structure, morphology and magnetic, optical and visible-light photocatalytic properties of the as-prepared nanocomposite were respectively characterized by X-ray diffraction, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, vibrating sample magnetometry and UV-visible diffuse reflectance spectroscopy. Experimental results revealed that the weight percent of NiFe2O4 has a considerable effect on the photodegradation of rhodamine B, methylene blue and crystal violet under visible-light irradiation. Compared with pure NiFe2O4 and BiOI, all the heterogeneous NFO/BOI nanocomposites exhibited significantly enhanced photocatalytic efficiency. Among these prepared samples, the NiFe2O4/BiOI nanocomposite with 15% wt NiFe2O4 displayed the best photocatalytic activity. The enhanced photocatalytic performance was mainly ascribed to the efficient separation of photo-induced electron–hole pairs and the formation of highly active species, superoxide radicals (˙O2˙−), in the NFO/BOI photocatalytic oxidation system. Furthermore, the NFO/BOI nanocomposites could be easily separated and recycled from contaminant solution using a magnet, which exhibited great potential application in the treatment of various pollutants in wastewater by utilizing solar energy effectively.

Fabrication and photocatalytic property of magnetic SrTiO3/NiFe2O4 heterojunction nanocomposites

Novel multifunctional SrTiO3/NiFe2O4 nanocomposites were successfully fabricated via a two-step route. The as-prepared samples were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), field-emission transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). The results indicate that the SrTiO3/NiFe2O4 heterostructures are composed of SrTiO3 spheroidal nanoparticles adhered to NiFe2O4 polyhedra. The heterojunction established in the composite material accelerates the process of electron–hole pair separation and boosts the photo-Fenton reaction. Among the samples, 15 wt% SrTiO3/NiFe2O4 nanocomposites exhibit a powerful light response and excellent room temperature ferromagnetism. Subsequently, the photocatalytic degradation of RhB over the as-prepared samples was investigated and optimized, revealing that the 15 wt% SrTiO3/NiFe2O4 nanocomposites exhibit the best photocatalytic activity and stability under simulated solar light irradiation. Furthermore, according to experimental results, the possible mechanism of improved photocatalytic activity was also proposed.

Optimal co-catalytic effect of NiFe2O4/ZnO nanocomposites toward enhanced photodegradation for dye MB

Abstract A series of magnetically recyclable NiFe2O4/ZnO nanocomposites have been successfully fabricated by a facile two-step route. The as-prepared NiFe2O4/ZnO nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, vibrating sample magnetometer, ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. The results demonstrate that the NiFe2O4/ZnO nanocomposites are composed of ZnO particles (50–120 nm) integrated with NiFe2O4 particles (30–80 nm). Compared with bare ZnO, the NiFe2O4/ZnO nanocomposites exhibit evidently enhanced visible light absorption and decreased recombination of photo-generated electron-hole pairs. Moreover, the nanocomposites exhibit enhanced photocatalytic performance for the degradation of methylene blue under simulated solar light irradiation when compared with bare ZnO, and the 20%-NiFe2O4/ZnO nanocomposite is observed as the optimal composite. This is ascribed to the more efficient separation of photo-generated electron-hole pairs and generation of hydroxyl (˙OH) radicals in the 20%-NiFe2O4/ZnO nanocomposite. Furthermore, the NiFe2O4/ZnO nanocomposites have a high saturation magnetization, indicating that they can be magnetically separated and recycled from organic dye wastewater.

Fabrication of novel Cu2O/Bi24O31Br10 composites and excellent photocatalytic performance

This was the first report that novel Cu2O/Bi24O31Br10 heterostructure composites were synthesized by calcination-chemical reduction method. The as-prepared products were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FE-SEM), energy-disperse X-ray (EDS), photoluminescence (PL) spectroscopy, and ultraviolet–visible diffuse reflectance (UV–Vis DRS) spectroscopy. The photocatalytic activity of the samples was evaluated by the degradation of Methylene blue (MB) under visible light irradiation. The Cu2O/Bi24O31Br10 heterostructure composites show enhanced visible-light photocatalytic activity, which results from the efficient separation of photo-generated electron/hole pairs. The composites also exhibit good stability and recycling capacity in the photocatalytic process. Furthermore, radical scavenging experiments confirm that the reactive ·OH radicals play an important role in the photocatalytic reaction.

Enhanced photocatalytic performance of Z-scheme Cu2O/Bi5O7I nanocomposites

Cu2O/Bi5O7I nanocomposites were prepared by a facile thermal decomposition process and chemical reduction route. The structures, morphologies, optical and electrochemical properties of the samples were characterized by XRD, XPS, SEM, TEM, HRTEM, DRS, EIS and photocurrent responses. The photocatalytic activity of the composites was evaluated by the degradation of rhodamine B (RhB) under simulated sunlight irradiation, compared to bare Cu2O and Bi5O7I, the Cu2O/Bi5O7I composites exhibit an enhanced photocatalytic activity. The highest photocatalytic activity was observed for the 25.0%Cu2O/Bi5O7I composite. The superior photocatalytic activity of Cu2O/Bi5O7I nancomposites could be mainly ascribed to the stronger absorption ability for visible light and the high separation efficiency of photogenerated electron and hole pairs via a Z-scheme mechanism. Furthermore, it is concluded from the experimental results that ·OH and ·O2− are the dominant reactive species causing the dye degradation. The photocatalytic Z-scheme mechanism involved was discussed.