Ionic Liquid-assisted Preparation Of FeWO₄ Base Composites And Its Enhanced Photocatalytic Activity

In recent years, the phenomenon of water ecology destruction and water pollution in the world is increasing. It is urgent needed to rationaliy and efficiently control water pollution in order to maintain the ecological balance of the water.photocatalytic technology is a method for degradation of water pollution. Because of its pollution-free, residue-free properties, it has been the focus of researchers studied since it was found. Traditional photocatalytic semiconductor material（TiO₂ as the representative） has large band gap and is only excited by ultraviolet light（sunlight accounts for only 4%） and its quantum efficiency is not high. Photocatalytic nano-heterojunction semiconductor not only has high activity, small size, large specific surface area, but also combin with high quantum efficiency and wide spectral range of absorption. It has become the focus of photocatalytic material modification methods. In addition, tungstate materials also occupy a place in the light catalysis because of its unique structure and properties.This paper focuses on FeWO₄ material. FeWO₄, FeWO₄ / Ag₃PO₄ composites,FeWO₄ / Ag₃VO₄ composites were prepared. The photocatalytic performances of FeWO₄/Ag₃PO₄ and FeWO₄/Ag₃VO₄ composites have been optimized by regulating the content of FeWO₄ to find the optimum ratio. In addition, the possible photocatalytic mechanism of semiconductor materials is analyzed.（1） Used the property of solvent, templates and dispersant of metal-based ionic liquid, the FeWO₄ microspheres was synthesed by hydrothermal method. FeWO₄ microspheres have been characterized in morphology, structure, elements and quantum transfer efficiency by X-ray photoelectron spectroscopy（XPS）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, energy dispersive X-ray spectroscopy（EDS）, UV-Vis diffuse reflectance spectroscopy（DRS） et al. In addition, the photocatalytic activity of FeWO₄ microspheres has been tested by degradating Rhodamine B（RhB） in the presence of H₂O₂. When the H₂O₂ was added, the photocatalytic activity of FeWO₄ microspheres degradated RhB solution are more than 70% in 5 min. When the photocatalytic reaction was carried out for 20 min, RhB almost completely degraded.Contrasted newly synthesized FeWO₄ microsphere with the FeWO₄ microspheres after the catalytic reaction in the XRD figure, FeWO₄ microspheres before and after the photocatalytic reaction have not any change. This shows that the crystal structure of FeWO₄ is not changed in the process of photoreaction.（2） The FeWO₄/Ag₃PO₄ composites with different FeWO₄ content are prepared by a mothed of coprecipitation in ambient temperature. FeWO₄ / Ag₃PO₄ composites were characterized and analyzed by XRD, XPS, DRS, SEM, PL, photocurrent methods et al. There is no Ag existed from the XRD and XPS patterns. The result suggests that FeWO₄/Ag₃PO₄ can be uccessfully prepared by the method. As can be seen from the SEM image, FeWO₄ and Ag₃PO₄ are linked closely, which can enhance the photocatalytic activities. As can be seen from the PL and photocurrent, the recombination rate of photo-generated electrons and holes in FeWO₄/Ag₃PO₄ composites can be suppressed. Rhodamine B is used as a target pollutants in the photocatalysis experiments. It can be seen from the photocatalytic activity test that FeWO₄/Ag₃PO₄ shows high photocatalytic activity compared with pure Ag₃PO₄.Among FeWO₄/Ag₃PO₄ composites, 3 wt% FeWO₄/Ag₃PO₄ has the highest photocatalytic activity.（3） By co-precipitation method at room temperature, novel FeWO₄/Ag₃VO₄ composites were prepared using water as solvent. The composites were characterized by XRD, SEM, XPS, DRS, PL, photocurrent and other tests to figure out morphology structures and other features. As can be seen from the SEM image, Ag₃VO₄ nanoparticles are observed anchored on the surface of FeWO₄ microspheres. The results of XRD and XPS analysis illustrate that the as-synthesized catalyst is FeWO₄/Ag₃VO₄ composite and there is on Ag existed. As can be seen from the PL and photocurrent, the separation rate of photo-generated electrons and holes in FeWO₄/Ag₃VO₄ composites is improved compared to Ag₃VO₄. Rhodamine B is used as a target pollutants in the photocatalysis experiments to contrast the activity of different materials. Due to the interaction between FeWO₄ and Ag₃VO₄, FeWO₄ /Ag₃VO₄ composites exhibited good photocatalytic activity.