Research On Surface Treatment Of Titanium And Titanium-based Insoluble Anode

Insoluble anode（DSA） refer to anodes which can maintain size and shape duringelectrochemical process. DSA have high catalytic activity, good corrosion resistance. Theyhave been widely used in acidic, alkaline medium as oxygen or chloride evolution materials inelectroplating, chlor-alkali industry and water treatment.IrO₂/Ti anode is one of the widely used DSAs. So far, commercially available IrO₂/Tianode has some problems such as low acid resistance, low thermostability and short servicelife. These problems limit the industrial application of IrO₂/Ti electrode. Researches haveshown that some methods could be employed to improve the performance of IrO₂/Ti electrode,such as proper pretreatment of titanium substrate, composite IrO₂with RuO₂、SnO₂or othermetal oxide, adding metal or metal oxide interlayer. For the aim of improving theperformance of IrO₂/Ti electrode, the main works of this thesis are as follows:（1） Ordered, large area TiO₂nanotube arrays were prepared by anodic oxidation inNH4F/H2SO4electrolyte. The morphology and structure of TiO₂nanotubes were characterizedby Scanning electron microscope（SEM） and X-ray diffraction（XRD）. The formationmechanism of the nanotubes and the effect of voltage on the morphology are discussed.Results show that in a certain range, increasing the voltage contributes to the formation ofTiO₂nanotubes, and the pipe diameter increases with voltage; when the voltage is more than25V, the titanium dioxide nanotubes collapse. The process of anodic oxidation can be dividedinto three stage, formation of barrier layer, formation of porous layer and growth of porouslayer.（2） Thermal decomposition method was used to prepare IrO₂coating on Ti/TiO₂surface,and the resulting electrode was labeled as Ti/TiO₂/IrO₂. IrO₂was coated on Ti using the samemethod, named as Ti/IrO₂. The microstructure and phase structure of the coating werecharacterized by SEM and XRD, respectively. Cyclic voltammetry （CV）, linear sweepvoltammetry （LSV） and Chronopotentiometry were used to study the electrochemicalproperties. Results show that the Ti/TiO₂/IrO₂has lower oxygen evolution potential andlonger life than Ti/IrO₂, which means better electrochemical performance and higherapplication value.（3） Solution of NaF and NaCl were used to treat titanium substrate, then IrO₂coatingswas prepared by thermal decomposition on the above substrates. The influence of solution pHare discussed. SEM, XRD, CV, LSV and Chronopotentiometry were used to study thestructure and properties of Tix/IrO₂electrodes. Results show that when the pH value is1, the obtained electrode has lower oxygen evolution potential and longer life, which means betterelectrochemical performance.