Multi-polyoxometalate Based Composite Modified Electrodes, Electrochemical And Electro-catalytic Research

1. Inorganic-organic hybrid polyoxometalates nanoparticles have been designed and prepared by solid-state reaction at room temperature and immobilized on the surface of wax impregnated graphite electrode (WIGE) by the sol-gel technique for the first time. The electrochemical behavior of the nanoparticles modified WIGE (P2Mo18-WIGE) has been studied in detail, including pH-dependence, solvent effect and stability. The electrocatalytic behavior of the P2Mo18-WIGE toward the reduction of chlorate, nitrite and hydrogen peroxide in 1 M H2SO4 aqueous solution is reported. Experimental results show that the P2Mo18-WIGE not only maintains the electrochemical activity and electrocatalytic properties of the H6P2Mo18O62, but also shows remarkable stability due to insolubility of the hybrid POM nanoparticles, which is important for practical application.2. PMo12-based inorganic-organic hybrid material (C21H38N)3-PMo12O40-H2O was designed, synthesized and firstly used as a bulk-modifier to fabricate a renewable three-dimensional chemically modified carbon paste electrode (CPE) by direct mixing. Electrochemical method was used to characterize the modified CPE. The hybrid material bulk-modified CPE (HM-CPE) not only displays good electrocatalytic activity toward the reduction of nitrite, bromate and hydrogen peroxide, but also exhibits a remarkable advantage of renewability in the event of surface fouling, as well as simple preparation and inexpensive material. Another remarkable advantage of the HM-CPE is its excellent stability due to insolubility of the inorganic-organic hybrid material, the affinity of the C21H38N+ toward the paste and the adsorption of PMo12 on graphite, which is important for practical application.3. Inorganic-organic hybrid polyoxometalates nanoparticles was firstly used as a bulk-modifier to fabricate a three-dimensional chemically modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior of the solid nanoparticles dispersed in the CPE in acidic aqueous solution is characterized by cyclic and square-wave voltammetry. The hybrid 18-molybdodiphosphate nanoparticles bulk-modified CPE (MNP-CPE) displays a high electrocatalytic activity towards the reduction of nitrite, bromate and hydrogen peroxide. The remarkable advantages of the MNP-CPE over the traditional polyoxometalates-modified electrodes are their excellent reproducibility of surface-renewal and high stability owing to the insolubility of the hybrid 18-molybdodiphosphate nanoparticles.4. Keggin-type phosphomolybdate (PMo12)-doped polypyrrole (PPy) prepared by chemical syntheses was firstly used as a bulk-modifier to fabricate a chemically modified carbon paste electrode (CPE) by direct mixing. Both the advantage of polyoxometalates (POMs)-doped polymer and surface-renewal property of the CPE are fully utilized. The PMou-PPy bulk-modified CPE also showed high electrocatalytic activity toward the reduction of hydrogen peroxide. A hydrodynamic voltammetric experiment was performed to characterize the electrode as an amperometric sensor for the determination of hydrogen peroxide. The sensor can be renewed easily in a repeatable manner by pushing a little carbon paste out.5. The electroactive composites containing tris(2,2'-bipyridine) ruthenium(II) and polyoxometalates RuPMo12 and RuS2Mo18 were synthesized and firstly used as a bifimctional electrocatalysts to fabricate a chemically bulk-modified carbon paste electrode (RuPMon-CPE) by direct mixing and graphite organosilicate composite electrode (RuS2Mo18-GOSE) by sol-gel process. The electrochemical behavior of the RuPMo12-CPE and RuS2Mo18-GOSE was studied by cyclicvoltammetry. The RuPMo12-CPE and RuS2Mo18-GOSE present good electrocatalytic activity not only toward the reduction of hydrogen peroxide and bromate, which is attributed to the function of polyoxometalates, but also toward the oxidation of arsenite, which is...