Studies On Electrochemical Properties Of K₆[P₂W₁₈O₆₂]·14H₂O And Preparation Of Electrodes Modified With The POMs

The polyoxometalates (POMs) constitute an extremely large and diverse class of compounds. Their remarkable chemical and physical properties have led to a variety of potential applications in medicine, electricity, catalysis, magnetics and chemical analysis. One of the most attractive features of POMs is that the metal-oxygen framework can undergo reversible, stepwise, multi-electron transfer reactions, which are the basis of many catalytic processes. In this paper, first, the Dawson-type polyoxometalates K6[P2W18O62]·14H2O was synthesized and characterized using UV-visible spectroscopy and Fourier transform infrared spectrometer. Then the redox properties of this compound were studied in solution. Finally, the catalysis of the compound towards the reduction of H2O2, NaNO2, KIO3, KBrO3 was stuided. From the results, it was found that the catalytic abilities of compound towards the reduction of H2O2, KIO3, KBrO3 and NaNO2 are different, for KIO3 and KBrO3,the catalytic abilities are lower than for H2O2, and for NaNO2 is the lowest. The oxidation potentials are shifted step by step towards the negative position with the increasing H2O2 and KIO3 concentrations. However, the oxidation potential moved positively step by step with the increasing of KBrO3 concentration, the oxidation potential have no change with the increasing of the NaNO2 concentration.Although the polyoxometalates showed good catalytic ability, but their ratio of area and volume is small. We hope to increase their ratio of surface area and volume.As the nanoparticles have a big surface area, we tried to enlarge the surface area by compositing polyoxometalates and nanoparticles. In this thesis, we synthesized a kind of Fe3O4 nanoparticles coated by PDDA(poly (diallyldimethylam monium chloride)),and investigated its morphology and purity by TEM and XRD. The composite film is fabricated onto by electrostatic interaction with layer-by-layer (LBL)self-assembly technique, and the assembly process and the uniformity of this film was studied.