The Study Of Modified Electrode Based On Polyoxometalates: Fabrication, Electrocatalytic And Photoelectrocatalytic Properties

The aim of chemically modified electrodes is to carry out the molecular design on the electrode surface. In other words, some molecule, ion and polymer with excellent properties are immobilized on electrode surface and the electrode with specially chemical and physical properties is obtained. And it has been intensively used in electroanalysis due to their high sensitivity and excellent selectivity. Therefore, a new type of chemically modified electrode built by different materials and different strategies should provide a new ideas for its development and application in sensors, catalysis and other areas.Polyoxometalates (POMs), a well-known class of nanoclusters with much diversity in size, composition, and function, have attracted increasing attention worldwide. One of the most attractive features of POMs is that the metal-oxygen framework can undergo reversible and stepwise, multielectron-transfer reactions. Their very rich redox chemistry makes them suitable for electrode modification, electrocatalysis and electroanalysis. Thus, it has great significance that the design and development of modified electrode based on POMs, extend the application of POMs modified electrode in electrocatalysis and photoelectrocatalysis. In this paper, we focus on the preparation of chemically modified electrodes containing POMs, carbon nanotubes (CNTs) and nanotitanium dioxide by self-assembly and sol-gel technology. The electrocatalytic and photoelectrocatalytic activities for the chemically modified electrodes were investigated to detect small chemistry molecule and biological activity molecular.1. A new electrocatalytic multilayer films electrode, which shows bifunctional electrocatalysis on iodate and hydrazine, was obtained by the layer-by-layer self-assembly of vanadium-substituted phosphotungstate 1,2-K8P2W16V2O62?18H2O (P2W16V2) on ITO electrode. Electrocatlytic activity of P2W16V2 modified electrode towards hydrazine and IO3- was performed using cyclic voltammetry and Amperometry. The proposed modified electrode has high stability, fast response and low detection limit, which extends the application of POMs-based modified electrode in electrocatalysis.2. A novel composite film modified glassy carbon electrode (GCE) based on the heteropolyacid/CNTs was fabricated due to the good electrocatalytic ability of heteropoly acids and excellent electrochemical properties of CNTs. Keggin-type POM (H4SiMo12O40) was potentiodynamic deposited on GCE and then was used as matrix to form multilayer films by electrochemical growth method with the CNTs. Thus-prepared multilayer films and the electrochemical behavior of the composite film modified electrode were characterized by UV–vis spectroscopy and cyclic voltammetry in detail. The preparation process of the modified electrode is simple and convenient. The resulting multilayer films have high stability and good electrocatalytic activity, which opened up a new way for development POMs modified electrode in the actual application.3. We developed a facile strategy for the first time to fabricate heteropolytungstate (P2W18) and CNTs modified GCE. In this work, chitosan was used as a dispersant to form a stable CNTs?chitosan composite, and then prepared P2W18/CNTs?chitosan modified electrode by electrostatic interactions. The electrochemical and electrocatalytic activities for the P2W18/CNTs?chitosan electrode were investigated in detail. The results suggest that the presence of CNTs in the composite film not only enhances the conductivity of the film but also increases the surface area of the electrode and the surface coverage of P2W18. The developed composite electrode greatly enhances the sensitivity and stability of POMs/CNTs modified electrode.4. Phosphotungstic acid?anatase nanocomposite film (H₃PW₁₂O₄₀-TiO₂) was prepared using sol?gel technology, and their photoelectrochemical properties were examined in the Na2SO4 solution. The results demonstrated that H3PW12O40-TiO₂ films possess high photoelectrochemical performance. POMs as electron scavergers can retard effectively the fast electron-hole recombination on the suface of TiO₂, and consequently enhance the photoelectremical response. Amino acids are the basic components units of protein, so that fundamental photodecomposition study of amino acids is of importance.The photoelectrocatalytic property of H3PW12O40-TiO₂ electrode was evaluated by oxidation aspartate (Asp). The results show that Asp photooxidation kinetics obeys Langmuir-Hinshelwood kinetic equation.