The Preparation Of Polyoxometalates-Anocomposite Modified Electrodes And Heir Electrocatalytic Properties

Chemical modified electrodes are achevied via the molecule or functional groupsdesigned on the electrode surface by some chemical or physical methods. Therefore,the electrodes have the especial and opitional properties depending on their modifiedmaterials. It has been intensively used in electroanalysis due to their high sensitivityand excellent selectivity.Polyoxometalates (POMs) become the attractive candidates for chemicalmodified electrodes due to their reversible redox activities and excellentelectrocatalytic properties. Thus, it is great significance to design and develop themodified electrode, extending the application of POMs modified electrode inelectrocatalysis and photoelectrocatalysis. POMs have the weak stability leading tolose their activity of catalysis under the neutral or alkalinity condition.Graphene with an atomically thin two-dimensional lattice of sp~2packed into adense honeycomb is characterized as "the thinnest known material and the strongestever measured". It has received considerable attention due to the high surface areahigh chemical stability and unique electronic and mechanical properties, which ensureits potential applications in many fields, such as nanocomposites, field-effecttransistors, nanoelec-tronics, and ultrasensitive sensors. Because of containing richfunctinonal groups such as carboxyl and hydroxyl, the dispersity and dissolution ofgraphene would be greatly improved. Coupled graphene with polyoxometalates andionic liquid, we prepare a seise of eletrodes with these compounds. It is important toextend the application of POMs modified electrode in electrocatalysis andphoto-electrocatalysis.In this paper, we focus on the preparation of chemically modified electrodescontaining POMs, graphene, polymers and ironic liquid by dip method and layer bylayer self-assembly. The electrocatalytic activities of the electodes were investigatedto detect small inorganic chemistry molecule and biological activity molecular.(1) Combination metal nanomaterials of its unique electronic, optical, magnetic,and catalytic properties with high conductivities of graphene, a composite material was prepared from graphene and palladium nanoparticles (Pd NPs) by one-pot way.The material was characterized by scanning electron microscopy and Ramanspectroscopy. Cyclic voltammetry demonstrated the presence of electrocatalyticcenters in the palladium decorated graphene. The effects of scan rates, pH solutions,and stability were studied in details. Experimental results showed that the modifiedelectrode not only maintains the electrochemical activity and electrocatalyticproperties of PMo12, but also in corporation of Pd NPs increases its sensitivity bymore than an order of magnitude. This sensor reveal excellent catalysis to iodate.(2) Owing to the strong interaction between graphene and polyoxometalate, wesynthetized graphene-POMs composite materials during the reduction process of thegraphene by one-pot method. The as-prepared graphene-based materials possesses alarge specific surface area, good dissolubility and well dispersibility, excellentconductivities. In this work, we prepared the modified electrode by dipping thedimethyl formamide(DMF) solution of graphene-based materials, and the acetonsolution containning polyoxometalate and ionic liqiud. The electrochemical behaviorof the composite films modified electrode was characterized by cyclic voltammetry indetails. The results showed that high stability and good electrocatalytic activity foriodate, and could be in application of the detection for the real samples.(3) We synthetize a controlled-thickness polypyrrole (PPy) nanoparticles withinultrathin films by a layer-by-layer (LbL) adsorption and polymerization method. Byrepetitive adsorption of pyrrole and subsequent polymerization with12-molybdophosphoric acid, the polyelectrolyte multilayer films containing PPynanoparticles were fabricated. Cyclic voltammograms (CVs) was used to characterizethe PPy nanoparticles and their multilayer thin films and the electrochemistrybehavior. The results suggested that the LbL adsorption and polymerization methoddeveloped herein provides an effective way to prepare PPy nanoparticles in thepolymer matrix. The sensitivity of the nanocomposite depends on the number ofbilayers of POMs–PPy. And this electrode showed good stabality, reproducibility, andgood electrocatalytic activity for bromate.