What is titanium anode？
Coated titanium electrode, also known as metal anode, is usually called Dimen-sionally Stable Anode (DSA), also known as Dimen-sionally Stable electrode, also called Mixed Metal Oxide Anode (MMO anode), which was developed in the late 1960s. A new type of high-efficiency and energy-saving electrode material developed.
Coated titanium electrode, also known as metal anode, is usually called Dimen-sionally Stable Anode (DSA), also known as Dimen-sionally Stable electrode, also called Mixed Metal Oxide Anode (MMO anode), which was developed in the late 1960s. A new type of high-efficiency and energy-saving electrode material developed.
The DSA electrode is a Ceramic-Electro-catalytic-Semi-Conductor, referred to as CESC coated electrode. It uses titanium as the substrate because titanium is a so-called valve metal that is used in salt water. It is conductive when used as a cathode, and immediately non-conductive when used as an anode. This is the meaning of "valve". Titanium has the performance of a single-phase fluid carrier. This is due to the formation of a passivation film on its surface and cannot be used as an anode in salt water; if it is coated with a layer of enamel-electrocatalytic-semiconductor coating, it becomes corrosion-resistant and conductive. Good anode.
Enamel-electrocatalysis-semiconductor coating is mainly composed of TiO₂. TiO is the main raw material of this enamel. After calcination, this coating has the stability and firmness of enamel and adheres tightly to the titanium mesh. However, TiO is not conductive. , need to be additionally coated with RuO2.
Ruthenium is a platinum group metal. Its outer electronic structure is 4d'5s', with valence from 1 to 8. Ru0 has the following characteristics:
(1) It has catalytic properties. RuO2 is a catalyst for the chlorine discharge reaction at the anode. The reason why the ruthenium oxide and titanium oxide layers can reduce the precipitation potential of chlorine gas is mainly due to the electrocatalytic activity of ruthenium.
(2) It is both a semiconductor and a metallic conductor. Among many transition element oxides, the only oxides with this property are RuO2, IrO2, OsO2 and TiO2.
(3) Although the crystal fastness of RuO2 is not enough, the ionic radii of Ru4+ and Ti4+ are almost the same, so RuO₂ can form a solid solution with TiO₂ to form a strong and stable film. Ru4+ replaces part of TiORu4+ in the film, making the coating become Semiconductor, excess RuO₂ can also serve as a catalyst.
The enamel-electrocatalyst-semiconductor coating must also contain a certain amount of iridium and chlorine, because although the RuO2 electrode has excellent corrosion resistance to many cid and alkali salts, it is easily corroded in sodium hypochlorite solution, and iridium is resistant to sodium hypochlorite. However, it has good corrosion resistance and has a much higher current efficiency than ruthenium when electrolyzed in low-concentration brine. For example, in the Chlor-Alkali Industry, the consumption of only ruthenium and platinum group metals is 0.1g of chlorine per ton. If iridium is added, the consumption is close to zero. In addition, IrO2 is a semiconductor-type material with metallic conductivity, and Ir4+ and Ru4* ions belong to the same crystalline form. The ionic radii are similar, so IrO2 can form a stable solid-liquid phase coating with RuO2, so the iridium content is about 20%. The enamel-electrocatalytic-semiconductor coating also contains trace amounts of chlorine of about 3.5%, mainly because it can significantly improve the conductive properties of the coating. This is the original prototype of titanium anode.