Study On The Catalytic And Electrochromic Properties Of Polyoxometalate Nanocomposite Films

Polyoxometalates?Abbr:POMs?are a class of metal-oxygen single molecular clusters with the nanometer scale.Due to their adjustable structure,rich composition and reversible redox properties,POMs have potential applications in catalysis,optics,electricity,magnetism and other aspects.On the one hand,POMs with the reversible redox properties were elechemically reduced to heteropoly blue by intramolecular valence electron transfer at room temperature.Then the electrons were transferred to GO and H4ClO4 to prepare the nano-composite films for catalytic research.On the other hand,POMs show the colorless/blue reversible electrochromism under the oxidation/reduction potential.We study the electrochromism of composite film including POMs and GO prepared with layer by layer?LBL?self-assembly technology.The electrochromic film will have a wide range of appplications in the smart glass,display device and other fields.In this paper,the catalytic capacity and electrochromic properties of film with POMs were studied by using POMs as reducing agent and stabilizing agent.The research content includes the following four parts:?1?Based on the electron transfer between phosphotungstic acid,graphene and chloroauric acid,a novel method for the preparation of a tricomponent composite film of POMs/graphene/gold nanoparticles was developed by in-situ electrochemical reduction.In this method,the reduced P8W48 was served as reducing agent,stabilizer and bridging molecules simultaneously in the composite film.First of all,P8W48acted as electrocatalyst to transfer the electrons from electrode to GO and HAuCl4.GO was reduced to rGO and HAuCl₄.was reduced from Au^?to Au⁰ to form Au Nps.Meanwhile,P8W48 was adsorbed on the rGO nanosheets through the electron transfer interaction,forming the{PEI/rGO}-Au@P8W48 composite film.The composition,structure and morphology of the as-prepared sample was characterized by scanning electron microscope?SEM?,transmission electron microscopy?TEM?and X-ray photoelectron spectroscopy?XPS?.?2?The{PEI/rGO}-Au@P8W48 composite film was used as the electrode material for the detection of H2O2.The result indicated the better catalytic effect of{PEI/rGO}-Au@P8W48 modified electrode than{PEI/rGO}-P8W48 modified electrode.This is probably due to the synergistic effect P8W48,Au NPs and rGO.In addition,the film can be used as an electrochemical sensor for the detection of H2O2in milk samples.?3?The electrochemical behavior of uric acid catalyzed by{PEI/rGO}-Au@P8W48 composite film was studied.The result showed that the composite film had good catalytic activity,sensitivity,stability and anti-interference ability.In addition,the film can be used as an electrochemical sensor for the detection of uric acid in urine samples.?4?In this chapter,a hybrid multilayer film[PEI/P8W48]n and[PEI/P8W48/PEI/GO]n on the surface of ITO conductive glass were prepared by LBL self-assembly method.The result displayed that the combination of P8W48 and GO with good conductivity could enhance the performance of electrochromism.