Synthesis Of (SiW₁₂-M) Nanoparticles By Photocatalysts And The Electrocatalytic Properties Of Their Modified Electrode

In this paper metal nanoparticles were prepared using Keggin structure tungstosilicate H₄SiW₁₂O₄₀(short for SiW₁₂)as photocatalyst.The nanoparticles were successfully immobilized on the electrode surface.And a modified electrode with high stability,good sensitive response and outstanding electrocatalytic property was obtained.First,gold,silver and gold/silver(core/shell) nanoparticles supported with SiW₁₂ were prepared by simple photoreduction technique.Here,the heteropolyanions acted as reducing agents,photocatalysts and stabilizers.And propan-2-ol heteropolyanions acted as electron victim.The influence factors to nanoparticles property are investigated by adjusting different experimental parameters such as the time of UV irradiation,the concentration of propan-2-ol or PW₁₁M.The experiment indicated the uniform spherical nanoparticels can be obtained when reactants were irradiated for 12 minutes and the colloids were stable and not easy to deposit.Second,SiW₁₂-NPs were successfully immobilized on the glassy carbon and ITO electrode surface with PVP layer-by-layer assembly film,and a SiW₁₂-M-PVP mutillayer film modified electrode was obtained.The multilayer films were characterized by UV-visible spectroscopy and cyclic voltammetry.The absorbency and current were increased linearly with the number of the assembly film layer,which showed the mutillayer films were uniform and regular.The electrochemical activity and their electrocatalytic properties of these modified electrodes can be characterized by cyclic voltammetry.The redox waves of SiW₁₂ were appeared for SiW₁₂-Ag-PVP/GCE, SiW₁₂-(Au/Ag)-PVP/GCE and SiW₁₂-Au-PVP/GCE in 0.5mol/L H₂SO₄.All of such modified electrodes had efficient electrocatalytc response to NO₂^-,H2_O2,IO₃^- and BrO₃^-. The electrocatalytic ability of SiW₁₂-Ag-PVP/GCE and SiW₁₂-(Au/Ag)-PVP/GCE were better than that of SiW₁₂-Au-PVP/GCE.The heterogeneous catalytic rate constant of SiW₁₂-Ag- PVP/GCE for NO₂^- is 4×10³ mol^-1·L·s^-1 by chronoamperometric measurement.The experiment results show photoreduction technique by which nanoparticles supported with SiW₁₂ are prepared is simple and convenient.The figure of nanoparticles can be influenced by adjusting experimental parameters.SiW₁₂-NPs are successfully immobilized on the glassy carbon with PVP layer-by-layer assembly mutillayer film. The modified electrode exhibits stable and sensitive.It not only keeps electrochemical activity and electrocatalytic properties,but also current increase evidently because of conductivity or electrocatalysis of metal nanoparticles.