A titanium electrode is a particular type of electrode that is based on titanium metal and, after sintering and oxidation, forms a layer of electrocatalytic oxide coating on the titanium substrate. Due to its physical dimension stability while in use, it is also known as Dimensionally Stable Anode (DSA for short).
Classification of titanium electrodes
According to the chemical composition and main electrochemical properties of the coating, titanium electrodes can be roughly divided into the following three categories:
Ruthenium-coated titanium electrode
These electrodes have a low overpotential of chlorine evolution and a high overpotential of oxygen evolution and are mainly used in various chlorine evolution occasions, such as Chlor alkali industry, cathodic protection, etc. This type of electrode coating includes the original ruthenium titanium coating (Ru Ti) and the Ru Ir Ti, Ru Co Ti, Ru Co Sn Ti, Ru Sn Ti, Ru Si Ti, Ru Ti Zr, Ru Ti La, Ru Ti Ce and other coatings developed on this basis.
An electrode made of titanium without ruthenium
A precious metal with high prices and few natural reserves is ruthenium. In order to reduce the amount of Ru and even completely replace Ru, a non-Ru coated titanium electrode was developed. These electrodes generally have high oxygen evolution overpotential. More successful electrodes include tin antimony-coated titanium electrodes, Co3O4 spinel-coated titanium electrodes, and palladium oxide-coated titanium electrodes.
Iridium-coated titanium electrode
In some electrolytic processes, such as electrolytic extraction of non-ferrous metals, electroplating industry, and electrochemical reduction to produce organic substances, the design reaction of the anode is the oxygen evolution reaction. Therefore, it is hoped to develop an anode material with low oxygen evolution overpotential. Iridium-coated titanium electrode was developed under this background. Ir Co, Ir Ta, Ir Sn, Ir Ta Co, Ir Ru Pd Ti, and other coatings are examples of such electrode coatings. The most effective oxygen evolution electrode is titanium with an Ir Ta coating.
The preparation methods of titanium electrodes are as follows:
Thermal decomposition method
The thermal decomposition method usually involves dissolving metal salt compounds in an organic solvent or aqueous solution, coating the solution on titanium substrate, heating to volatilize the solvent, and then high-temperature sintering to decompose and oxidize the salts to obtain oxide coating. The coating methods include spraying, roller coating, or brush coating. Spraying and roller coating are highly mechanized and suitable for industrial production. The labor environment is good, and the coating is relatively uniform, but the waste of coating liquid is relatively large. Brush coating is generally applicable to small-scale production. This method requires simple equipment and less loss of coating solution, but the labor intensity is high, the labor environment is poor, and the coating is often not uniform. It is easy to prepare multi-component oxide electrodes with an excellent performance by controlling the coating formulation by the thermal decomposition method.
Sol-gel method
The sol-gel method is a new method to prepare coatings based on the principle of colloidal chemistry. It can prepare ultra-fine grain electrode coatings, which can greatly increase the specific surface area of the electrode surface. The general process of preparing titanium electrodes by this method is to disperse metal-organic compounds (such as metal alkoxides) or inorganic compounds in the solvent, generate active monomer through hydrolysis reaction, polymerize the active monomer to generate sol, coat the sol on the titanium substrate, dry the sol film to obtain gel film, and then sinter at a certain temperature to obtain the coating. Compared with the traditional thermal decomposition method, the electrode coating prepared by this method is uniform, with finer grains and almost no cracks, which has attracted much attention in recent years.
Electrodeposition
Coated titanium electrode is prepared by electrodeposition, generally using an insoluble electrode as an anode, pretreated metal titanium as cathode, electrolysis in a solution containing corresponding metal ions, metal ions are deposited on metal titanium cathode, dried, and then sintered at high temperature to obtain coated titanium electrode. The coating obtained by this method is generally uniform and dense. The disadvantage of this method is that the process is complex and it is not easy to make uniform large-area electrodes.
Sputter method
The films prepared by sputtering are compact and have strong adhesion to the substrate. However, this method requires special equipment, the preparation process is relatively complex, and the waste of mother liquor is relatively large, which is not suitable for large-scale industrial production.
