Modification Of Ag₃PO₄ And ZnO And Their Photocatalytic Performance

With the rapid development of socienty and economic, the problem of depleting resource and ecological environment is increasing. Semiconductor photocatalysis, based on clean solar energy, has become an effective way to deal with the problem. This technology can convert solar energy into hydrogen through water splitting, eliminate toxic organic pollutants through photocatalytic degradation, and also be used in surface cleaning. In the field of environment, how to prepare highly efficient, low cost and stable photocatalyst is very important.Ag₃PO₄ is widely studied as an excellent visible-lighted photocatalyst in recent years. When coupled with stable and cheap TiO₂, the composite exhibits strong ability in absorbing visible light, transferring and separating photo-induced electrons and holes. We synthesized Ag₃PO₄/TiO₂ composite using CH3 COOAg, Na2HPO4·12H2O and P25 as starting material, based on the co-precipitation method. The properties such as morphology, optical absorption, the separation of photo-induced elections and holes and the reaction activity of the composites were investigated. When the ratio of Ag+/TiO₂ is 12:1?AP12?, TiO₂ particles are best-dispersed on the surface of Ag₃PO₄ as isolated island in form of aggregate of several nanoparticles, and the composite has the lowest PL peak, so AP12 is the most effective in charge seperation. It exhibits the highest visible light activity, and the reaction rate constant k is 0.34 min-1 that is 2.43 times that of pure Ag₃PO₄, as well as 1.55 times of that of physical mixture. Also, the stability of Ag₃PO₄/TiO₂ composite is much better than pure Ag₃PO₄, as confirmed by XPS, XRD and UV-Vis DRS patterns. Then, according to the transfer of photo-induced elections and holes between different planes, we prepared the composite of TiO₂ nanosheet which exposed highly {001} planes and Ag₃PO₄ nanodots, and then adjusted the mass ratio of TiO₂ and Ag₃PO₄. It proves that the visible-light activity of the composite increases with the decrease of TiO₂/Ag₃PO₄ mass ratio, but when the mass ratio is 1:4, the morphology of Ag₃PO₄ nanodots decorated TiO₂ nanosheets is damaged to some degree.Metal organic frameworks?MOFs? have emerged as a promising porous materials with very large specific surface area and adjustability. Because of the remarkable advantages and facile synthesis of MOFs, they have been widely adopted for different applications, including gas storage, gas separation, catalysis, templates and chemical sensors. We chose ZIF-8, which can be rapidly synthesized at room temperature, as template to get porous cubic Zn O structure. According to the TG curve under air atmosphere, we prepared C350, C400 and C450 by one step calcination, and C350@400, C350@450 by two step calcination. Then we studied the morphology, optical absorption, the separation of photo-induced elections and holes, and the reaction activity in MO degradation under UV-Vis light. It was found that the reaction rate constant k of C350@400, C350@450, C350, C400 and C450 are 0.062 min-1, 0.047 min-1, 0.008 min-1, 0.024 min-1 and 0.02 min-1, respectively. So the reaction rate constant of C350@400, C350@450 prepared by two-step calcination is much higher than thoes made by one-step calcination. The reaction rate of C350@400 is almost 2.6 times of one-step calcined samples.