CN1772955A - A kind of mixed metal oxide electrode and preparation method thereof - Google Patents

Abstract

The mixed metal oxide electrode features the metal substrate with one intermediate layer coated via physical and/or chemical process and one mixed metal oxide coating formed through painting, several times of thermal decomposition and sintering on the intermediate layer. The metal substrate is made of Ti, Ta, Nb, Zr, W, Al or stainless steel; and the intermediate layer is one or several of nitride, boride or carbide of Ti, Ta and Nb. The mixed metal oxide electrode has the advantages of high electric catalytic activity, high electric conductivity, high anode oxidation resistance, long service life and low production cost.

Description

A kind of mixed metal oxide electrode and preparation method thereof

technical field

The invention relates to a mixed metal oxide electrode for electrochemical engineering and a preparation method thereof, in particular to a mixed metal oxide electrode containing an intermediate layer and a preparation method thereof.

Background technique

Both the electrochemical industry and the electrometallurgical industry are inseparable from electrodes, and the selection of electrode materials is extremely important. The direction and kinetics of the electrode process, the structure type of the electrode and the electrolytic cell and the life of the cell, the maintenance cost and labor consumption, and the dynamic index of the process all depend to a large extent on the structure of the electrode and the materials used, especially The electrode type and cell structure design are closely related to the durability, conductivity, electrocatalytic activity and power consumption value of the electrode material. The continuous development of new electrode materials with superior performance has always received great attention.

The existing coated titanium electrode uses metal titanium as the electrode substrate, and its surface is coated with an active coating mainly composed of platinum group metal oxides. Coated titanium electrodes are also called metal anodes, generally called DSA at home and abroad. Henry Beer first revealed the electrocatalytic activity of metal oxides, obtained a patent for ruthenium oxide coating in South Africa in 1965, and published a patent for titanium-based mixed ruthenium oxide coating in Belgium in 1967. After that, Vittorio de Nora put H. Beer's invention into industrialization. Relevant scholars believe that the invention of DSA is an epoch-making contribution to the field of electrochemistry and one of the most important inventions in electrochemistry in the 20th century. At present, there have been many reports on the theoretical research and invention of DSA, and its purpose is nothing more than to improve the electrocatalytic performance and service life of the electrode. There are two aspects affecting the life of the coated titanium electrode: one is the active dissolution of the catalytic layer, and the other is the oxidation passivation of the titanium substrate. The active dissolution of the catalytic layer can be controlled from the composition, ratio and sintering process of the catalytic layer. Regarding the inhibition of electrode failure caused by the passivation of the titanium substrate, relevant literature has proposed the use of tantalum as the intermediate layer, but a fatal shortcoming of this method is that the cost of manufacturing the electrode is too high, and the application value is lost. It is also pointed out in the literature that the oxidation passivation time of the titanium substrate can be reduced by increasing the number of coatings of the catalytic layer and increasing the thickness of the catalytic layer, but this undoubtedly greatly increases the manufacturing cost of the electrode, and in terms of the final effect, it affects the life of the electrode. Improvement is also limited. Therefore, under the premise of ensuring the electrocatalytic performance of the electrode, how to develop a new type of electrode with low cost and long life has become a key problem that the electrochemical industry needs to solve urgently.

Contents of the invention

The object of the present invention is to provide a mixed metal oxide electrode and its preparation method, which can solve the above-mentioned problems in the prior art.

A mixed metal oxide electrode is characterized in that there is a metal substrate, coated with an intermediate layer, and a mixed metal oxide coating is coated on the intermediate layer; the metal substrate is titanium, tantalum, niobium, zirconium , tungsten, aluminum, or stainless steel, and the intermediate layer is one or more of titanium, tantalum, or niobium nitrides, borides, or carbides.

The preparation method of the above-mentioned mixed metal oxide electrode is characterized in that an intermediate layer is coated on the metal substrate by physical or/and chemical methods, and then the mixed layer is coated on the intermediate layer and formed by multiple times of thermal decomposition and sintering. Metal oxide coating; the metal substrate is one of titanium, tantalum, niobium, zirconium, tungsten, aluminum or stainless steel, and the intermediate layer is nitride or boride or carbide of titanium or tantalum or niobium one or more of them.

The electrode of the invention has the advantages of high electrocatalytic activity, good electrical conductivity, strong anodic oxidation resistance, long service life and low production cost.

Description of drawings

Accompanying drawing 1. is the structural representation of the titanium base mixed metal oxide coating that has titanium nitride intermediate layer.

Accompanying drawing 2. It is the effect diagram comparing the electrocatalytic performance of the titanium-based mixed metal oxide electrode with and without the titanium nitride interlayer.

Accompanying drawing 3. It is the comparison graph of the accelerated life test result of titanium-based mixed metal oxide electrode with and without titanium nitride intermediate layer.

Detailed ways

The structure of mixed metal oxide electrode of the present invention is as shown in Figure 1, and it is to coat an intermediate layer 2 on metal base 1, and coat mixed metal oxide coating 3 on intermediate layer 2; Described metal base 1 is one of titanium, tantalum, niobium, zirconium, tungsten, aluminum or stainless steel, and the intermediate layer 2 is one or more of nitrides, borides or carbides of titanium, tantalum or niobium. The metal substrate 1 is a substrate that has undergone degreasing and acid etching. The thickness of the intermediate layer 2 is in the range of 0.1 μm to 20 μm.

During preparation, an intermediate layer 2 is coated on the metal substrate 1 by physical or/and chemical methods, and then the mixed metal oxide coating 3 formed by coating the intermediate layer 2 and forming by multiple times of thermal decomposition and sintering; The intermediate layer 2 can be prepared by various physical or/and chemical methods, including ion nitriding, ion implantation, thermal spraying, physical vapor deposition, chemical vapor deposition, and plasma-assisted chemical vapor deposition. The mixed metal oxide coating 3 is composed of at least one active component and at least one inert component. The active component is a platinum group metal or its oxide, and the inert component is a non-platinum group metal or its oxide. The thermal decomposition preparation process of the mixed metal oxide coating 3 is to mix the precursor compounds of the active component and the inert component in an organic solvent to form a solution, and apply the solution on the surface by spraying, rolling or brushing. The intermediate layer 2 is then dried and then sintered at a high temperature, and then the above coating process is repeated at least three times. The sintering temperature in the high temperature sintering process is 400-560°C.

During the specific operation, at first the commercially pure titanium TA2 is cleaned with a metal cleaning agent, or the titanium plate is used as the cathode in 10% (weight percent) NaOH aqueous solution to carry out electrolytic degreasing, and then in 10% oxalic acid aqueous solution, treat it under slight boiling 2 to 3 hours, then rinse with water, and set aside. In the case of containing a titanium nitride layer, a layer of titanium nitride layer with a thickness of about 1 μm is plated on the above-mentioned titanium substrate by ion plating.

Mixed metal oxide coating 3 Select the iridium-tantalum mixed oxide coating used in the oxygen evolution electrode widely used in industry, and its typical coating mother solution is: H ₂ IrCl ₆ xH ₂ O (dissolved in hydrochloric acid)+TaCl ₅ (dissolved in ethanol) mixed solution, wherein the Ir/Ta molar ratio is 7:6, and then diluted with concentrated hydrochloric acid to a total metal concentration of 0.2mol/L. Use a woolen brush to apply the above solution on the above-mentioned titanium substrate with and without the TiN intermediate layer 2, and dry it in an oven at 120°C for 6-15 minutes, then place it in a box-type electric furnace at 400-560°C. Sinter at the same temperature for 10 minutes, take it out for air cooling, repeat the above steps 10 times, and anneal at the sintering temperature for one hour for the last time. In this way, titanium-based iridium-tantalum mixed oxides with and without TiN intermediate layers were prepared at sintering temperatures of 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C and 560°C, respectively. 9 electrodes each.

The result of evaluating the electrocatalytic performance of the electrode of the present invention is shown in FIG. 2 . The evaluation of electrocatalytic performance is to measure its anode current density in 0.5mol/L sulfuric acid aqueous solution with a constant current at +1.4V (relative to a saturated calomel electrode). The larger the value of the anode current density, the higher the catalytic performance. It can be seen from Figure 2 that the current density of the electrode containing the TiN interlayer 2 is very close to that of the electrode without the TiN interlayer 2, indicating that the introduction of the TiN interlayer 2 does not have a negative impact on the electrocatalytic performance of the electrode.

Fig. 3 shows the results of the enhanced lifetime evaluation of the electrodes of the present invention. In 1mol/L sulfuric acid aqueous solution, adopt the constant current method, control the current density to 2A/cm ² , and measure the change of the cell pressure with time. When the cell voltage rise exceeds 5V, the electrode is considered to have failed. It can be seen from Figure 3 that the strengthened life time of the electrode containing the TiN interlayer is generally longer than that of the electrode without the TiN interlayer, especially for the electrode with a sintering temperature of 460 ° C, its strengthened life is twice that of the electrode without the TiN interlayer about.

TiN belongs to metal bond ceramics, which has much higher electrical conductivity than titanium, its corrosion resistance is similar to that of titanium, and it also has good anodic oxidation resistance, and it still maintains high electrical conductivity during anodic oxidation without The anodic oxide film like titanium is non-conductive. It is precisely because of its characteristics that it can be used as an intermediate layer to slow down the passivation of the titanium substrate, thereby improving the service life of the electrode. Moreover, the manufacturing cost of TiN is very low, it can be produced in batches, and can meet the requirements of industrial production.

Other metal substrates (tantalum, niobium, zirconium, tungsten, aluminum or stainless steel) of the present invention have similar properties to the above-mentioned titanium substrates, and the other intermediate layers (titanium boride or carbide, tantalum or niobium) One or more of nitrides or borides or carbides) also have similar properties with the above-mentioned TiN, and the electrode prepared by using them to realize the present invention also has the same functional effect, so it will not be exhausted here. stated.

The novel electrode obtained by the preparation method of the present invention can be widely used in chlor-alkali, water electrolysis, sewage treatment, organic electrosynthesis, electrodialysis and electrodeposition industries, and can be used as an anode or a cathode.

Claims (7)

1. A mixed metal oxide electrode is characterized in that there is a metal substrate (1), an intermediate layer (2) is coated on the metal substrate (1), and a mixed metal oxide coating is applied on the intermediate layer (2). layer (3); the metal substrate (1) is one of titanium, tantalum, niobium, zirconium, tungsten, aluminum or stainless steel, and the intermediate layer (2) is titanium or tantalum or niobium nitride or One or more of borides or carbides. 2. The electrode according to claim 1, characterized in that the metal substrate (1) is a substrate that has undergone degreasing and acid etching. 3. The electrode according to claim 1, characterized in that the thickness of the intermediate layer (2) is 0.1 μm˜20 μm. 4. The electrode according to claim 1, characterized in that the mixed metal oxide coating (3) has at least one active component and at least one inert component mixed composition, and the active component is a platinum group metal Or its oxide, the inert component is a non-platinum group metal or its oxide. 5. the preparation method of mixed metal oxide electrode described in claim 1 is characterized in that on metal substrate (1) by physical or/and chemical method coating an intermediate layer (2), then in intermediate layer (2) ) and a mixed metal oxide coating (3) formed by multiple thermal decomposition and sintering; the metal substrate (1) is one of titanium, tantalum, niobium, zirconium, tungsten, aluminum or stainless steel , the intermediate layer (2) is one or more of titanium, tantalum, or niobium nitrides, borides, or carbides. 6. The preparation method according to claim 5, characterized in that the physical or/and chemical methods for preparing the intermediate layer (2) include ion nitriding, ion implantation, thermal spraying, physical vapor deposition, chemical vapor deposition, Plasma Assisted Chemical Vapor Deposition. 7. The preparation method according to claim 5, characterized in that the thermal decomposition and sintering is to mix the precursor compound of the active component and the inert component in an organic solvent to form a solution, and the solution is sprayed, rolled It is coated on the metal substrate (1) by painting or brushing, then dried, and then sintered at high temperature, and the sintering temperature is 400-560°C.

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