Research Of Some Fundamental Problems On Stability Of Titanium Substrate Lead Dioxide Elctrodes （Ti/PbO₂）

Modern chemistry plays a key role in the improvement of quality of life anddevelopment of society around the world. However, these advances frequently comewith an increase in contamination of the environment by toxic substances. Nowadays,it gets the attention to reduce or avoid pollution of the environment due to increasingeconomic, social and environmental pressures. Electrochemical process has certain abroad space for development on the environment treatment and materials’development because of environment protection, safety and easy operation. Electrodematerial is the heart of electrochemical technology and the key of electrochemicalreaction efficiency.Ti/PbO₂electrode is widely used as industrial anode due to its excellentconductivity, excellent corrosion, high electrocatalytic activity and low cost, etc.However, the stability of the Ti substrate PbO₂electrode needs to be improved asmore as possible. Therefore, we make a series of fundamental researches in order toimprove the stability of Ti substrate PbO₂electrode. In this work, the deactivationprogress of a Ti substrate PbO₂electrode in H2SO4solution is studied during theaccelerated life test. We obtain the deactivation reasons of Ti substrate PbO₂electrodein different stage. Then we enhance the performance of Ti substrate PbO₂by dopingF-, introducing solid solution interlayer and using porous Ti substrate. The maincontributions of this research are as follows:（1）The deactivate process of Ti/PbO₂electrode is complicated. According todifferent dominant reason at various stages, the deactivation process can be roughly divided into the following several stages: In the initial stage of electrolysis, H2SO4electrolyte contact with internal and external of PbO₂electrode more completely,which leads to a fast increase of active site for about10-20h. After that, the oxideanode suffers a long period of steady state stage for about300h. Finally, PbO₂coatingdetachment phenomenon is found due to the interaction of O₂evolution. Then TiO₂passivation layer are formed quickly on bare Ti substrate which lead to the dissolveand detachment of PbO₂coating more fast, which leads Ti substrate PbO₂electrodedeactivated completely.（2）F-PbO₂electrode is electrochemical deposited in the Pb（NO3）2platingsolution including different NaF concentration by galvanostatic technology. F-caninfluent the rate of electrodeposition. The higher the F-concentration, the moreobvious the effect. The concentration of F-in Pb（NO3）2plating solution can changethe content of F-in PbO₂electrode. F-content in PbO₂electrode will be increasedwith the increase of F-concentration in the plating solution. When the concentrationof F-is0.02mol/L, the F-content in the electrode achieved the maximum value. F-doping can make the particle get smaller and PbO₂specific surface area increase.Because F-doping PbO₂electrode can inhibit the electrolyte into the Ti substratesurface and slow the dissolution loss of PbO₂coating, it can obviously increase theservice life of the electrode.（3）Ti-substrate is coated by three different mixed oxides （SnO₂-Sb₂O₅,RuO₂-TiO₂, IrO₂-Ta2O5）, then PbO₂is electrodeposited on them to prepare PbO₂electrode with different interlayer. The results indicated that the above oxide interlayerexited in the form of solid solution and the interlayer combines the Ti substrateclosely with the PbO₂coating. The presence of solid solution interlayer can increasethe stability of Ti substrate PbO₂electrode. The accelerated service life of Ti/PbO₂,Ti/SnO₂-Sb₂O₅/PbO₂, Ti/RuO₂-TiO₂/PbO₂and Ti/IrO₂-Ta2O5/PbO₂electrode are about58,207, and672h, respectively. Cyclic voltammogram indicates that the PbO₂electrode with the solid solution interlayer have more active surface area in sulfuricacid solution. The oxygen evolution potential decreases as the following order ofTi/PbO₂, Ti/SnO₂-Sb₂O₅/PbO₂, Ti/RuO₂-TiO₂/PbO₂, and Ti/IrO₂-Ta2O5/PbO₂.（4） Porous Ti-substrate （porosity:40%, aperture:30μm） is coated bySnO₂-Sb₂O₅, then PbO₂is electrodeposited on them to prepare porousTi/SnO₂-Sb₂O₅/PbO₂electrode. The electrode has high surface area and good electrical conductivity, which can be used as a substrate of PbO₂electrode. In order toremain the porous structure, the deposition time of PbO₂electrode should not exceed30min with the current density20mA/cm2. The embedded structure between porousTi/SnO₂-Sb₂O₅substrate and PbO₂coating can increase the stability of porousTi/SnO₂-Sb₂O₅/PbO₂electrode. The service life of porous Ti/SnO₂-Sb₂O₅/PbO₂electrode is about350h. Porous Ti/SnO₂-Sb₂O₅/PbO₂electrode has better electricalcatalytic activity of phenol degradation than plate Ti/SnO₂-Sb₂O₅/PbO₂electrode.