Electrochemical Behavior, Microfabrication And Isotopic Characterization Of ?-PbO₂ Microdomains Based On SECM

At present,the researches on the electrochemical performance of various modified PbO₂ electrodes mostly were carried out in the macroscopic scale.The obtained electrochemical performance parameters are the average measured values of the entire electrode test area.It is difficult to distinguish the differences in the electrochemical performance of different micro-regions on the electrode surface.Therefore,it is necessary to find a method with spatial resolution to conduct in-depth research on the heterogeneity,electrochemical activity,interfacial reaction kinetics and structure-activity relationship of the active layer of PbO₂ material from the micro-scale.In this thesis,scanning electrochemical microscope(SECM)is employed to study the electrochemical reaction activity and interface reaction kinetics of PbO₂ electrode microdomains,and to establish the relationship between micro-region structure and performance.The results show following conclusions:1.?-PbO₂ electrode can support the oxidation reaction of[Fe(CN)₆]^4-under the open-circuit potential,at microscopically different positions,[Fe(CN)₆]^4-has different chemical reaction rates,and hence significantly different electrochemical reactivity.The effective heterogeneous charge transfer rate constant k_eff is computed to be 0.0253cm·s^-1 by fitting the positive feedback curve.The largest[Fe(CN)₆]^4-oxidation reaction rate on the localized?-PbO₂ electrode emerges when the substrate potential is maintained at 0.5 V,achieving the best resolution of the constant-height image;furthermore,the EIS results macroscopically strengthen this conclusion by demonstrating that the charge transfer process of[Fe(CN)₆]^4-is the easiest.2.The high electrochemical reaction activity of the short-time electrodeposition comes from the regional high electrochemical activity,and the single-point high electrochemical reaction activity contributes to the high activity of the long-term electrodeposition.In the current density window,the main factor that affects the electrochemical reaction activity of the electrode surface micro-area is the microstructure of the surface PbO₂ crystal.When the plating time is 60 minutes,the sensitivity of the electrode reaction interface to potential changes becomes weaker,and the electrode material has better stability.When the electroplating current density is 20m A·cm^-2,the high electrochemical reactivity of the PbO₂ electrode micro-area results from the combined effect of roughness,coating thickness,and phase composition.The study of the apparent heterogeneous charge transfer rate constant shows that changing the electroplating time to improve the electrochemical reactivity of the PbO₂ electrode mainly depends on the modification of the microscopic morphology and structure of the electrodeposition time.The improvement of electroplating current density and addition of Na F on the reactivity not only depends on the modification of the microscopic morphology but also the elevation of the intrinsic chemical properties of PbO₂.3.,The chemical lens method serves as the best way to achieve PbO₂ surface micromachining among the four micromachining methods using SECM,featuring obvious marking and controllable deposition area.The optimal conditions for the chemical lens method for micro-area deposition on the surface of the PbO₂ electrode are:the concentration of silver ions is 0.01 M,the probe potential is 1.4 V,the substrate potential is 0.4 V,and the increment distance of PAC is 1?m.This condition finally realized the micro-area deposition in a circular area with a diameter of 20?m.The same localized micro-area characterization study including the microdomain structure and electrochemical reactivity information of?-PbO₂ found that the localized area without a complete crystal redstone structure has higher electrochemical reactivity than the complete crystallized area.