In modern industry and scientific research, the performance of electrode materials plays a decisive role in the efficiency and quality of many electrochemical processes. Titanium anode, as an electrode material with excellent performance, has been widely used in many fields since its advent. It is based on titanium and coated with a specific metal oxide coating on the surface. This unique structure gives it many excellent properties, such as good conductivity, excellent corrosion resistance, high catalytic activity and dimensional stability, making it a key factor in promoting the development of industries such as chlor-alkali industry, electroplating, water treatment, and electrolytic organic synthesis.
2. Working Principle
2.1 Basic Electrochemical Principles
In an electrolytic cell, an electrochemical reaction is triggered when current passes through the electrolyte. The anode is the electrode where oxidation reaction occurs, and the cathode is the electrode where reduction reaction occurs. Taking the common electrolysis of salt water to prepare chlorine and caustic soda as an example, at the anode, chloride ions (Cl⁻) lose electrons and are oxidized to chlorine (Cl₂), and the reaction formula is: 2Cl⁻ – 2e⁻ = Cl₂↑; at the cathode, water gains electrons and is reduced to hydrogen (H₂) and hydroxide ions (OH⁻), and the reaction formula is: 2H₂O + 2e⁻ = H₂↑ + 2OH⁻.
2.2 Unique mechanism of action of titanium anode
In this process, the titanium substrate of the titanium anode mainly plays a supporting and conductive role. The metal oxide coating on the surface is the key, which can significantly reduce the overpotential of a specific oxidation reaction. For example, in the chlorine evolution reaction, metal oxides such as ruthenium (Ru) and iridium (Ir) in the coating can provide special active sites, making it easier for chloride ions to lose electrons and convert into chlorine, thereby reducing the voltage required for the reaction, improving the electrolysis efficiency, and saving electricity. In the oxygen evolution reaction, the coating can also reduce the overpotential of water oxidation to generate oxygen and promote the smooth progress of the reaction.
III. Classification
3.1 Classification by function
Chlorine evolution anode: Mainly used in chloride electrolyte systems, such as electrolysis of saturated brine and electrolysis of seawater to produce chlorine in the chlor-alkali industry. Its surface coating is usually rich in ruthenium oxides, which have good electrocatalytic activity for chlorine evolution reaction and can effectively reduce the overpotential of chlorine evolution. When saturated brine is electrolyzed in the chlor-alkali industry, a ruthenium-coated chlorine evolution anode is used. The overpotential of chlorine evolution is reduced by about 100-150mV compared with the traditional graphite anode, which greatly improves the chlorine evolution efficiency and production stability.
Oxygen evolution anode: Suitable for sulfate, nitrate and other electrolyte systems, it plays an important role in electroplating, electrolysis of water to produce hydrogen, wastewater treatment and other processes. The surface of this type of anode is mostly iridium-based coating, which can significantly reduce the overpotential of oxygen evolution. For example, when electrolyzing water to produce hydrogen, an iridium-coated oxygen-evolving anode is used, and the oxygen-evolving overpotential is 0.2-0.3V lower than that of ordinary electrodes, which improves the efficiency of hydrogen production and reduces energy consumption.
3.2 Classification by application field
Titanium anode for chlor-alkali industry: It is the core component of chlor-alkali production. Compared with traditional graphite anodes, it has the advantages of long life, high current density, high product purity and low energy consumption. In the production of caustic soda by diaphragm method, the working current density of graphite anode is generally 8A/dm², while that of titanium anode can reach 17A/dm², the output can be doubled, the purity of chlorine gas is high, and the alkali concentration is also higher.
Titanium anode for electroplating: It is widely used in the electroplating of non-ferrous metals such as nickel plating, gold plating, chromium plating, zinc plating, and copper plating. As an anode or auxiliary anode, it can make the coating uniform and smooth, and improve the quality of the coating. The oxygen-evolving overpotential of the new insoluble titanium anode is about 0.5V lower than that of the lead alloy anode, which saves energy significantly, does not pollute the plating solution, and has a long service life.
Titanium anode for water treatment: can be used for seawater desalination, wastewater treatment, drinking water disinfection, etc. In the electrocatalytic oxidation technology of wastewater treatment, the strong oxidizing free radicals (such as hydroxyl radicals・OH) produced by the titanium anode can effectively degrade organic pollutants, and the COD removal rate of printing and dyeing wastewater, pharmaceutical wastewater, etc. can reach more than 80%.
Titanium anode for electrolytic organic synthesis: in the electrolytic synthesis of organic compounds, it promotes the oxidation reaction of organic molecules and realizes the synthesis of specific organic products, such as the preparation of organic acids and organic alcohols. When synthesizing certain fine chemicals, the titanium anode can provide a suitable electrocatalytic environment to improve the reaction selectivity and yield.
IV. Application fields
4.1 Chlor-alkali industry
Key role in the production process: In the ion membrane method and diaphragm method production process of the chlor-alkali industry, titanium anode is an indispensable component. Taking the ion membrane method as an example, the coating on the surface of the titanium anode can promote the oxidation of chloride ions and produce high-purity chlorine gas, while ensuring the long-term stable operation of the anode in high-concentration salt water and highly corrosive environments, thereby improving production efficiency and product quality.
Advantages: Compared with traditional graphite anodes, titanium anodes have a longer service life, which can be increased from 8 months of graphite anodes to more than 6 years; it can greatly increase the current density, thereby increasing the production capacity of a single tank; it avoids the pollution of anode dissolution to the product, making the chlorine gas purer, free of CO₂, and with a higher alkali concentration, and it can also save heating steam and reduce energy consumption.
4.2 Electroplating industry
Application in various electroplating processes: In the nickel plating process, the titanium anode can release nickel ions evenly, ensure the uniformity and glossiness of the nickel plating layer, and improve the corrosion resistance of the plated parts; when chrome plating, the use of titanium anodes can effectively reduce the generation of chrome mist, reduce environmental pollution, and at the same time improve the hardness, wear resistance and corrosion resistance of the chrome plating layer; in the gold plating process, the titanium anode can ensure a stable supply of gold ions, obtain a high-quality gold plating layer, and meet the high requirements of electronic devices, jewelry, etc. for plating.
Impact on coating quality and production efficiency: The use of titanium anodes can reduce the cell voltage and save energy consumption; it has high chemical and electrochemical stability and long service life during the electroplating process, reduces the frequency of anode replacement, and improves production efficiency; and can make the coating more uniform and dense, improving the appearance and performance quality of the plated parts.
4.3 Water treatment field
Seawater desalination: In the electrodialysis and electrolysis methods of seawater desalination, titanium anodes, as key electrode materials, can promote the migration and reaction of ions in seawater and achieve the separation of salt and water. In the electrodialysis seawater desalination device, the stability and efficient ion conductivity of titanium electrodes can effectively improve the desalination efficiency and reduce energy consumption.
Wastewater treatment: Electrocatalytic oxidation is one of the important technologies for wastewater treatment, and titanium anodes play a key role in it. By generating strong oxidizing free radicals, organic pollutants in wastewater can be decomposed, such as degrading dye molecules in printing and dyeing wastewater into small molecules, thereby improving the biodegradability of wastewater; for wastewater containing heavy metal ions, heavy metal ions can be reduced and precipitated at the cathode through electrolysis to achieve wastewater purification.
Drinking water disinfection: Use disinfectants such as sodium hypochlorite produced by titanium anode electrolysis to disinfect drinking water. This disinfection method is safe and residue-free, and can effectively kill bacteria, viruses and other microorganisms in water to ensure the safety of drinking water.
4.4 Electrolytic organic synthesis
Application examples in common organic synthesis reactions: In the electrolytic synthesis process of adipic acid, the use of titanium anodes can promote the oxidation reaction of cyclohexanol or cyclohexanone and increase the yield of adipic acid; when producing terephthalic acid, titanium anodes can provide suitable conditions for electrochemical reactions and achieve efficient oxidation of xylene.
Promoting effect on organic synthesis reactions: Titanium anodes can reduce the overpotential of organic synthesis reactions, allowing reactions to proceed under milder conditions, improving reaction rates and selectivity; they can also avoid environmental pollution and cost issues caused by the use of large amounts of chemical oxidants in traditional chemical synthesis methods, providing an effective way for green organic synthesis.
4.5 Battery Industry
Application in different types of batteries: In lithium-ion batteries, titanium anodes can be used as part of the current collector or electrode material, which helps to improve the battery’s charge and discharge performance and cycle life; in vanadium flow batteries, titanium anodes, as key electrodes, can stably conduct current, promote electrochemical reactions, and improve the battery’s energy conversion efficiency.
Contribution to battery performance improvement: The good conductivity and stability of titanium anodes can reduce the battery’s internal resistance and increase the charge and discharge rate; its strong corrosion resistance can maintain stability in the complex chemical environment inside the battery, extending the battery’s service life; and it helps to increase the battery’s energy density and meet the battery performance requirements of different application scenarios.
V. Selection and Design
5.1 Select the appropriate type according to the application scenario
Analysis of the demand characteristics of different industries: The chlor-alkali industry requires titanium anodes with high chlorine evolution activity and resistance to salt water corrosion; the electroplating industry focuses on the stability of the anode and its impact on the quality of the coating; the water treatment field requires the anode to adapt to complex water quality and have good electrocatalytic oxidation performance; electrolytic organic synthesis requires the anode to have high catalytic selectivity for specific organic reactions.
Recommendation for corresponding types: The chlor-alkali industry recommends the use of ruthenium-coated chlorine anodes; the electroplating industry can choose ruthenium-titanium anodes according to different plating types, such as nickel plating, and ruthenium-iridium-titanium anodes for chromium plating; titanium anodes for water treatment can be selected according to water quality and treatment targets, such as iridium-coated oxygen anodes for acidic wastewater treatment; electrolytic organic synthesis can select anodes with targeted catalytic activity according to specific reactions.
5.2 Consider current density and electrolytic cell size
Current density determination method: Determine according to the reaction rate, production scale and characteristics of the anode material of the electrolytic process. Generally, the electrolysis efficiency and anode performance at different current densities are tested experimentally, and the optimal current density range is selected in combination with production costs and production requirements. For example, in electroplating, factors such as the surface area of the plated part, the coating thickness requirements and the composition of the plating solution should be considered to determine the appropriate current density.
Principle of matching electrolytic cell size with anode: The size and shape of the anode should be compatible with the electrolytic cell to ensure uniform electric field distribution and avoid excessive or insufficient local current density. The distance between the anode and cathode should be reasonably controlled, generally 5-25mm. If the distance is too small, short circuit is likely to occur, and if it is too large, resistance and energy consumption will increase.
5.3 Selection of coating formula
Performance characteristics of different coating formulas: Ruthenium titanium coated anode has high chlorine evolution activity and good cost performance, and is suitable for general chloride electrolyte system; Ruthenium iridium titanium coated anode has excellent comprehensive performance and is widely used in chlor-alkali industry, electroplating and other fields, and has both chlorine evolution and oxygen evolution performance; Iridium tantalum coated anode has high stability in strong oxidizing and acidic environments, and is often used in electrolysis of water for hydrogen production, wastewater treatment and other occasions with high requirements for oxygen evolution performance.
Select according to the characteristics of the electrolyte and reaction: If the electrolyte is a chloride system and mainly undergoes chlorine evolution reaction, ruthenium titanium coating can be selected; if the electrolyte is strongly acidic and requires high oxygen evolution activity, such as in electrolysis of water for hydrogen production, iridium tantalum coating is more suitable; for complex electroplating processes, it may be necessary to select ruthenium iridium titanium coating that can take into account multiple performances.
Conclusion
Titanium anodes play an irreplaceable role in many fields such as chlor-alkali industry, electroplating, water treatment, electrolytic organic synthesis, batteries, etc. due to their excellent performance. From selection and design to installation and maintenance, every link is related to its performance and service life. With the continuous advancement of science and technology, titanium anodes have broad development prospects in the research and development of high-performance coatings, integration with new technologies, and green environmental protection. In the future, titanium anodes will continue to innovate and upgrade, make greater contributions to promoting the high-quality development of various related industries, demonstrate their unique value in more emerging fields, and help achieve efficient, green, and sustainable development of industrial production.