Design, Preparation And Photocatalytic Properties Of Polyimide

Since the 21st century, with the continuous progress of human civilization, science and technology, turns out a variety of environmental pollution and the growing problem of energy scarcity. Searching for new energy sources to relieve the pressure of Earth’s imminent is very important. Photocatalytic technology with its low cost price, environmental pollution and other environmental problems become advantages and energy crisis hot research project. In the future, with a huge potential for water splitting by photocatalysis to provide renewable energy and clean hydrogen energy. So far, there have been more than one hundred kinds of materials have been shown to be photocatalytic activity. These semiconductor photocatalyst materials, although with low prices and costs, the catalytic activity and good features, but most of the metal-doped semiconductor material. These semiconductor materials not only because of mass production and increase the economic costs, but also increased metal ion contamination. In comparison, carbon-based semiconductor material because of its high chemical stability and rich reserves will become better choice.In recent years, polyimide (PI) was reported on under visible light irradiation can be used to restore the water photocatalytic hydrogen production. Polyimide is a polymer imide monomer is an industrial application and has excellent thermal and chemical stability, has been widely used in electrical and electronic industry, the separation of science and aerospace engineering area. Currently, during the synthesis of the polyimide typically requires a lot of tedious process, or at least the reaction at elevated temperatures for several hours.In this paper, we quickly polyimide synthesized by microwave-assisted method is simple, and the synthesis of inorganic by-step calcination method-organic composite photocatalyst material zinc oxide-polyimide and study their photocatalytic properties. The main contents of the thesis are as follows:1.Herein we used a rapid "microwave (MW)-assisted heating synthesis" to produce the crystalline polyimide in minutes. Importantly, the present strategy avoids the tedious washing process for the produced polyimide. The structure and morphology of the obtained products were characterized by powder XRD, FT-IR, N2 adsorption/desorption, SEM, and TEM. We have demonstrated the rapid and green synthesis of polyimide through MW-assisted heating process. This strategy shows the following advantages over the conventional heating process. First, The reactions can be finished within 10 minutes, making the process to be time-and energy-efficient. Second, the present strategy avoids the tedious washing process or using the toxic organic reagents. Therefore, the present reaction is a green synthesis process. The last but not the least, the polyimide prepared through present strategy shows improved crystalline over the conventional heating process, resulting in the enhanced H2 production. This innovative strategy provides a new route to synthesize the polyimide-related products, and can be extended to construct modified polyimide and hybrid materials based on polyimide and other semiconductors. We believe that the present process allows us to tune the chemical composition, electronic structure, and surface functionality of polyimide for catalytic reactions.2.Design and Synthesis of inorganic-organic hybrid zinc oxide-polyimide core-shell structure photocatalyst. Such composite material can be manufactured by one-step calcination process. The structure and morphology of the obtained composite material may be a powder X-ray diffraction (XRD), ultraviolet spectroscopy (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to characterize the resulting composites have good light catalytic properties. The resultant hybrids showed remarkablly enhanced photocatalytic activity for methylene blue (MB) decolorization under visible light irradiation. The decolorization rate of the optimum ZnO-polyimide photocatalyst (～31 wt% of ZnO) is 1.2 times of the pristine polyimide under the same experimental conditions. The photocatalytic mechanism reveals that the direct oxidation by photogenerated holes is the main reaction pathway for MB degradation. The enhanced photoactivity for MB decolorization over ZnO-polyimide hybrids is attributed to the effective interfacial charge transfer between ZnO and polyimide, thereby suppressed the recombination of the photoexcited electron-hole pairs and improved the photocatalytic efficiency. The present work demonstrates the great potential usage of polymeric photocatalysts in constructing the active heterostructured photocatalysts for environmental purification.