Synthesis, Characterization And Properties Of Keggintype Polyoxometalates Based Graphene Composites

Polyoxometalates(referred to POMs) are a class of metal-oxide cluster compounds,which are combined with oxygen to transition metals(Mo, W, etc.), and can be regulated their composition, structure and properties at the atomic and molecular level. POMs have a wide range of application in the fields of medicine, materials, especially catalysis. With the gradual enhancement of human environmental awareness, catalytic materials of POMs, which are environment-friendly, have attracted more and more attention. However, POMs have many limitations, for example, the small specific surface area, easily dissolved in water and difficult to recycle and reuse as catalysts. Graphene(GS) has received much concern known as the star material. With the unique structure, GS has larger specific surface area, good electrical conductivity and magnetic characteristics and so on, which can be used as an excellent host of composite materials in synthesis. In this paper, POMs and GS were selected as the construction unit, to prepare a series of polyoxometalates-graphene composites(POMGSs) in situ, in order to achieve the perfect combination of the structure and properties of the two kinds of materials. POMGSs were studied in electrochemical and catalytic oxidative desulfurization performance, and we found that the complex have advanced redox properties and excellent oxidation catalytic activity.The main work is as follows:1. Preparation, characterization and properties of Keggin type POMGSs composites. We selected Keggin type POMs and GS as building blocks, and prepared Keggin type POMGSs complexes in situ. We explored the issue of chemometrics of the synthesized complexes,especially the reasonable proportion of raw materials; Characterized the structure of the composites by using testing methods of FT-IR, XRD, TG, Raman and SEM and so on. The results showed that the structure of Keggin type POMs was complete and there existed strong chemical bonds between POMs and GS; We studied the electrochemical and catalytic oxidation desulfurization performance of composites. The results showed that the composites had strong oxidizing properties, and excellent catalytic oxidation performance of desulfurization.2. Preparation, characterization and properties of monosubstituted Keggin type POMGSs composites. Choosed monosubstituted Keggin type POMs and GS as building blocks, and prepared monosubstituted Keggin type POMGSs complexes in situ. The compounds werecharacterized by means of FT-IR, XRD, TG, Raman and SEM etc. The results showed that the structure of monosubstituted Keggin type was still intact existing in the composites, and there was strong chemical bonding between monosubstituted Keggin type POMs and GS; The results of the electrochemical experimental of composite showed strong redox properties.Through the experiment inquiry of catalytic oxidation desulfurization of dibenzothiophene,the results revealed that the monosubstituted Keggin type POMGSs composites have excellent oxidation catalytic activity.3. Preparation, characterization and properties of phosphomolybdic acid-graphene composite in situ. Elected PMo12 and GS as building blocks, and we made several significant changes in conditions about the feeding order of the synthesis process in situ, and compared to the work of 1 and 2, we synthesized novel PMo12–GS composite successfully; Used test methods of FT-IR, XRD, TG, Raman, SEM and TEM, to characterize the structure of the new composites; Studied the electrochemical and catalytic oxidation desulfurization performance of new composites. The results showed that the new composites by the improved synthetic process have stronger redox properties, and more excellent catalytic oxidation desulfurization activity than the products synthesized by the previous process route.