Elecrtocatalytic Water Oxidation With [Ag?H₂O?(H₃PW₁₁O₃₉)]^3-

[H₃Ag^I?H₂O?PW₁₁O₃₉]^3-and Ag⁺had dispalyed a excellent catalytic activity for chemical oxidation of water with S₂O₈^2-.It will be of great academic significance and potential application value to develop their modified electrodes.In this paper,the cyclic voltammetry of[H₃Ag?H₂O?PW₁₁O₃₉]^3-and Ag⁺was investigated in phosphate buffer solution by using glassy carbon electrode.Both of them show electrocatalytic activity.In the concentration of 0.002⁰.200 mmol/L,the former exhibits a higher catalytic currents than that of the latter.And the lower the concentration is,the larger the peak current difference is.Electrochemical impedance spectroscopy supports the conclusion.It is indicated that polyoxometalate ligands palys a important role in improving catalytic water oxidation for Ag⁺in the range of 1.10 V-1.40 V vs.Ag/AgCl,the cyclic voltammetry of[H₃Ag?H₂O?PW₁₁O₃₉]^3-shows a pair of Ox-Red peaks(E_pa?1.31 V,E_pc?1.22 V),?E_p>0.058/n.This demonstrates a qusi-reversible electrochemical process on the electrode surface.This is mainly a diffusion-controlled process.In the process,both the number of transferred electrons and the number of protons are 1.The possible reaction mechanism is proposed:[H₃Ag^I?H₂O?PW₁₁O₃₉]^3-?[H₂Ag^II?H₂O?PW₁₁O₃₉]^3-+H⁺+e^-3[H₂Ag^II?H₂O?PW₁₁O₃₉]^3-+2H₂O?3[H₃Ag^I?H₂O?PW₁₁O₃₉]^3-+O₂+H⁺The AgPW₁₁-TiO₂/ITO electrode was developed and characterized by XRD,SEM,UV and so on.Linear scanning voltammetry shows that[H₃Ag^I?H₂O?PW₁₁O₃₉]^3-modified TiO₂/ITO electrode exhibits better catalytic activity than Ag⁺modified TiO₂/ITO electrode at1.50 V vs.Ag/AgCl.for the water oxidation,indicating that the H₃PW₁₁O₃₉^3-ligand plays an important role in improving Ag⁺catalytic water oxidation.Electrochemical impedance spectroscopy shows that the former has a smaller impedance,which favors charge transfer and enhances the activity of electrocatalytic water oxidation.This is due to the H₃PW₁₁O₃₉^3-ligand.For the[H₃Ag^I?H₂O?PW₁₁O₃₉]^3-modified TiO₂/ITO electrode,photoelectrocatalytic oxidation of water was studied,the anode current of TiO₂/ITO electrode was 1.5 times higher than that at 1.44 V vs.Ag/AgCl,but the anode current of AgPW₁₁-TiO₂/ITO electrode was6.7 times higher than that at 1.44 V vs.Ag/AgCl when the voltage was 1.50 V vs.Ag/AgCl under 300 W xenon lamp irradiation.[H₃Ag^I?H₂O?PW₁₁O₃₉]^3-modified TiO₂/ITO electrodes are reused up to 15 times,and still maintain the high electrocatalytic activity.