Iridium tantalum coated titanium anode

A good electrode for oxygen evolution in the electrolysis industry is a mixed oxide coating of iridium oxide and tantalum oxide. The iridium tantalum coated titanium electrodes developed by Longsheng Company include plate electrodes, tube electrodes, mesh electrodes, rod electrodes, and wire electrodes for customers to choose from; Iridium tantalum coated titanium anode is an insoluble anode, and the platinum iridium coating is firmly bonded to the titanium substrate. Compared with ordinary coated electrodes, it enhances the resistance to gap corrosion and better improves the durability of the contact area between the titanium substrate and the coating.

Application of Iridium Tantalum Coating on Titanium Anodes

IrO2 and Ta2O5 coated titanium anodes have excellent electrocatalytic activity and electrochemical stability, and are widely used in the electrolysis industry with strong corrosive media, harsh working environments, and extremely high current density. They are currently recognized as excellent oxygen evolution electrodes.

1. Copper foil production

The production process of electrolytic copper foil involves first oxidizing the electrolytic copper to obtain a copper sulfate solution, and then electrolyzing it in a foil making machine to generate green foil. The green foil is processed through acid washing, roughening, curing, and brass plating to obtain the finished product. It includes two major processes: electrolysis and electroplating. For example, the process conditions of a copper foil production company are: sulfuric acid concentration of 120g/L, 7-9KA/m2, and a gap between the anode and cathode of 12mm. The use of IrTa anode can meet production requirements and solve the problem of extremely high production current density. It uses a metal roller partially immersed in a copper sulfate solution and continuously rotating as the cathode to produce foil through continuous electrolysis. Electrolytic copper foil is used as a conductive material on single-sided printed circuit boards, with increasing usage and thinner thickness, ranging from 0.15mm, 0.105mm, 0.07mm, 0.05mm, and 0.035mm.

Electrolytic copper foil can be divided into several types based on thickness, including 105um, 70um, 18um, 12um, 9um, and 5um. Among them, 12um and below are generally referred to as ultra-thin copper foil.

According to the surface treatment process, copper foil can be divided into several types, including pink foil (surface copper plating), ashed foil (surface zinc plating), yellowed foil (surface brass plating), and so on.

The IPc standard divides electrolytic copper foil into several categories based on its performance, including standard foil (STD Class E), high elongation foil (HD Class E), high-temperature high elongation foil (THE Class E) and annealed electrolytic copper foil (ANN Class E), low-temperature annealable electrolytic copper foil (LTA Class E), and annealable electrolytic copper foil (A-E Class).

Japan is manufacturing printed circuit boards using copper foil through electrolysis with copper sulfate solution. Copper is plated on a titanium rotating cylinder cathode with a diameter of 1-2 meters and a height of 2-3 meters, and the copper foil is peeled off at one end of the cylinder. When using copper foil for printed circuits, the coated titanium anode has a height of about 1.3 meters, a surface length of about 2.4 meters, and a plate thickness of about 25mm. Using a titanium based coating anode, the spacing between the plates does not need to be adjusted. The oxygen bubbles generated by the anode vigorously stir the electrolyte, accelerating the movement of copper ions towards the cathode surface. Therefore, the operating current density can be increased to 50A/dm2, significantly improving the productivity of the electrolytic cell. Applying IRO2 coating on titanium substrate using thermal decomposition method can work well under this medium condition. After setting up an extremely thin platinum plating intermediate layer, it can prevent the oxidation of the titanium substrate, and the anode life can reach at least 2.5 years.

2. Aluminum foil dot forming

The electrolyte is 10% -15% ammonium adipate, with a current density of 400-1000A/m2. Aluminum foil can be electroplated into IrTa coated anodes to solve the problem of high organic concentration.

3. Galvanized steel plate

As a major consumer of electricity in the electrolysis industry, for example, in steel plate galvanizing production lines, using low overpotential DSA instead of high overpotential lead electrodes can reduce energy consumption by lowering the electrodes. The applicable coating components are iridium oxide and tantalum oxide.

IrO2 · Ta2O5 coated anodes can be used on galvanizing production lines to replace lead alloy electrodes. Among these anode materials, the IRO2 based anode has excellent electrode performance. It has a low oxygen evolution overpotential, low consumption of electrocatalytic active layer, and little pollution to the electrolyte. The IrO2 · Ta2O5 anode has a long working life in electroplating at high current density, such as 10ka/m2.

4. Electroplating thick copper on circuit boards

The distance between the anode and cathode is 10mm, and the sulfuric acid concentration is 2mol/L. IrO2 · Ta2O5 coated titanium anode can be used to solve the problem of extremely high acidity.

5. Chromium plating

When a certain TV glass shell company is manufacturing TV and computer glass screens, the steel mold surface of the glass shell is prone to corrosion and appears uneven under high temperature and weak alkaline molten glass material sulfuric acid corrosion. In order to produce a smooth glass screen, the surface of the steel mold needs to be plated with hexavalent chromium. IrTa coated anode can be used instead of the original lead electrode.

6. Rhodium plating

In recent years, people's interest in platinum headgear has been increasing. Platinum plated headgear is actually rhodium plated. Rhodium plating uses a sulfuric acid rhodium plating solution, which is highly acidic and corrosive. IrTa coated titanium anodes have been widely used in the rhodium plating industry.

7. Silver nitrate electrolysis

Coarse silver can be refined by electrolysis to obtain refined silver. The electrolyte contains about 80g/L of silver, with a nitric acid concentration of 20g/L. The insoluble anode electrolysis method is used to recover silver. The anode is coated with IrTa titanium electrode, and silver is deposited on the cathode. The electrolytic waste liquid only contains about 10g/L of silver, which is sold at 150g/L.

8. Electrolytic organic synthesis

The electrodialysis method can directly electrolyze tetramethylammonium chloride to produce high-purity tetramethylammonium hydroxide. The anode uses IrO2 · Ta2O5 coated titanium anode, which has a lifespan many times longer than the general RuSnTi coating.

9. Electrometallurgy

In electrometallurgy, electrolytic production of zinc has always used lead alloy anodes containing small amounts of silver, antimony, or calcium. The use of lead anodes can lead to the following issues: unstable lead electrode size; The overpotential of oxygen evolution is too high, about 800mv, and it will corrode during anodic polarization. Lead ions dissolve in the electrolyte and deposit on the cathode, contaminating the metal zinc and affecting product quality. The size stable anode (DSA) coated with various metal oxides such as RUO2, IrO2, MnO2, Ta2O5, etc. on a titanium substrate has low oxygen overpotential and inert properties, and can be considered as an oxygen evolution anode coating for acidic solutions. Among the coating components, the IRO2 (70%, mole fraction) · Ta2O5 (30%, mole fraction) component is considered an excellent oxygen evolution anode coating. In the coating components, IrO2 is an electrochemical active substance for anodic polarization, and Ta2O5 can improve the chemical stability of IrO2. The estimated working life of Ti/IrO2 · Ta2O5 anode can reach 5-10 years.

10. Electrochemical industrial purification

Although Ti/IrO2 anodes are relatively expensive, they have still been used in electrochemical industrial purification processes recently. This is because the Ti/IrO2 anode has been successfully used as an oxygen evolution electrode in moderately strong or weakly acidic solutions, while the classic Ti/RuO2 electrode cannot be used due to its short service life in low concentration chloride ion solutions. Ti/IrO2 anode can be used to remove cations (on the cathode) from wastewater, or to remove harmful substances from wastewater through anodic oxidation.

The Ti/IrO2 · Ta2O5 coated electrode can be successfully used as an oxygen evolution electrode in the treatment of electroflotation wastewater containing dispersed peptides and oil. Stable cathode material is made of stainless steel. The current density of both the anode and cathode is 100-200A/m2, and the size of the bubbles (H2 and O2) generated by the electrochemical method is 50-100um, to ensure high efficiency of electro flotation, up to 99.5%, and to reduce the content of harmful substances in wastewater. The import concentration is reduced from 1-10g/L to 1-10mg/L.

The sewage flow rate through the electric tank is 12-16m3/h, 4-6 V, with a current of 300A. The Ti/IrO2 anode (with an area of 2 m2, Ir coating amount of 12.3g/m2, 65mol% IrO2, 35mol% Ta2O5) has a service life of more than 4 years in operation in the electric tank.

11. Electrochemical activity in aqueous solutions containing organic small molecules

Due to the adsorption and poisoning of intermediate product CO, a single precious metal Pt is not an ideal electrode for small molecule organic point catalytic oxidation. In recent years, DSA has been applied in the electro oxidation removal of organic pollutants. This active anode can effectively indirectly oxidize difficult to degrade pollutants into biodegradable intermediate organic products.

12. High speed tinned steel plate

The ruthenium titanium coated titanium anode used in the salt electrolysis industry has excellent electrocatalytic activity for chlorine evolution and is used by over 90% of chlor alkali enterprises worldwide, with a lifespan of up to 10 years. However, it cannot be used in electrochemical systems for oxygen evolution and has an extremely short lifespan.

Iridium coated titanium anodes have excellent electrocatalytic activity for oxygen evolution and maintain high stability in oxygen evolution electrochemical systems. Since 1997, iridium coated titanium anodes have been widely used in high-speed galvanized steel plate production lines in sulfate plating media, with a lifespan of about 1 year, replacing existing lead alloy anodes.

If organic matter is present in the electrolyte, when oxygen is released from the anode, the coated anode will experience "loss of active coating in the presence of organic matter", with a very short lifespan, even less than 1 day. The phenomenon of "high-speed loss of active coatings in the presence of organic matter" occurs as follows:

(1) When the high-speed loss phenomenon of active coatings occurs in the presence of organic matter, there will inevitably be a significant increase in electrode potential, even up to several hundred millivolts.

(2) The increase in electrode potential in the presence of organic matter only occurs during the anodic reaction of oxygen evolution, and has no effect on the anodic reaction of chlorine evolution, nor does it have any effect on the cathodic reaction of hydrogen evolution.

(3) The phenomenon of electrode potential increase and high-speed loss of active coatings in the presence of organic matter does not occur on electrodes of lead alloys and other systems, but is unique to platinum group metals and their oxide system electrodes.