阅读说明：本技术 一种用于工业电解的析氧阳极及其制备方法 (Oxygen evolution anode for industrial electrolysis and preparation method thereof ) 是由 范朝阳 温可寒 齐培栋 于 2021-08-25 设计创作，主要内容包括：本发明涉及一种用于工业电解的析氧阳极及其制备方法,析氧阳极包括导电基体和在导电基体的表面形成的多孔型催化剂层；导电基体为阀金属、阀金属合金的一种或多种；多孔型催化剂层包括二氧化铱、过渡金属氧化物和纳米二氧化硅颗粒；过渡金属氧化物为钛、钽、铌、锆、铪、钒、钼、钨、锡的一种或多种的氧化物。本发明采用的含有纳米二氧化硅颗粒的无机粘结剂可以在酸性或是中性溶液的电解过程中,减低析氧阳极上二氧化铱的消耗速率,延长析氧电极的使用寿命。(The invention relates to an oxygen evolution anode for industrial electrolysis and a preparation method thereof, wherein the oxygen evolution anode comprises a conductive substrate and a porous catalyst layer formed on the surface of the conductive substrate; the conductive matrix is one or more of valve metal and valve metal alloy; the porous catalyst layer comprises iridium dioxide, transition metal oxide and nano silicon dioxide particles; the transition metal oxide is one or more oxides of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum, tungsten and tin. The inorganic binder containing the nano silicon dioxide particles can reduce the consumption rate of iridium dioxide on the oxygen evolution anode and prolong the service life of the oxygen evolution electrode in the electrolytic process of an acidic or neutral solution.)

1. An oxygen evolving anode for industrial electrolysis, comprising a conductive substrate and a porous catalyst layer formed on the surface of the conductive substrate;

the conductive substrate is one or more of valve metal and valve metal alloy;

the porous catalyst layer contains iridium dioxide, transition metal oxide and nano silicon dioxide particles;

the transition metal oxide is one or more oxides of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum, tungsten and tin.

2. The oxygen evolving anode according to claim 1 wherein the molar ratio of iridium dioxide to silica is 0.2 to 5.0 and the nano silica particles have a particle size of 2 to 100 nm.

3. The oxygen evolving anode according to claim 1 wherein a corrosion resistant coating is formed between the surface of said conductive substrate and said porous catalyst layer;

the corrosion-resistant coating is one or more oxides of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum and tungsten,

the thickness of the corrosion-resistant coating is 0.1-2 mu m.

4. A method for preparing an oxygen evolving anode according to any of claims 1 to 3, characterized in that it comprises the following steps:

step (1), conducting pretreatment on a conductive substrate;

mixing an iridium dioxide precursor, a nano silicon dioxide particle precursor and a transition metal oxide precursor, adding the mixture into a 10-20% hydrochloric acid solution, and fully stirring to prepare a solution of the porous catalyst layer;

the precursor of the iridium dioxide is a water-soluble salt compound containing trivalent iridium ions and/or tetravalent iridium ions;

the precursor of the nano silicon dioxide particles is water-soluble nano silicon dioxide sol with a grain size;

the precursor of the transition metal oxide is a water-soluble transition metal salt compound;

step (3), coating the solution prepared in the step (2) on the surface of the conductive substrate treated in the step (1), drying, and then carrying out high-temperature roasting in the air to form the porous catalyst layer;

and (4) selecting the number of times of repeating the step (3) according to the thickness of the preset porous catalyst layer.

5. The method of claim 4, wherein the pre-treating the conductive substrate specifically comprises:

immersing the conductive substrate into an aqueous solution dissolved with a cleaning agent and ethanol, and carrying out surface cleaning and oil removal through ultrasonic treatment for 12-18 minutes;

drying for 0.5-1.5 hours at the temperature of 55-65 ℃;

cutting according to the required size, performing sand blasting treatment, and performing tempering and leveling at 580-620 ℃ for 2.5-3.5 hours;

pickling in boiling hydrochloric acid aqueous solution for 18-25 minutes;

and cleaning and drying to obtain the treated conductive matrix.

6. The method according to claim 4, characterized in that the molar percentage of said precursor of iridium dioxide to said precursor of transition metal oxide is (55% to 90%): (10% -45%) and the molar ratio of the precursor of the iridium dioxide to the precursor of the nano silicon dioxide particles is 0.2-5.0.

7. The method of claim 4, wherein the precursor of the nanosilica particles is prepared by:

exchanging the sodium silicate solution with cation exchange resin to prepare polysilicic acid mother liquor with small particle size;

adding elemental silicon powder treated by boiling water, and realizing the primary increase of the particle size of silica sol particles under the dual actions of hydrolysis reaction of the elemental silicon powder and dissolution reaction of the polysilicic acid mother liquor to prepare a first large-particle size silica sol crude product;

performing secondary growth on the basis of the first large-particle-size silica sol crude product to prepare a second large-particle-size silica sol crude product;

and removing impurities and concentrating the second large-particle-size silica sol crude product to obtain a precursor of the nano silica particles.

8. The method according to claim 4, wherein the step (3) comprises in particular:

and coating the prepared solution of the porous catalyst layer on the surface of the conductive substrate by using a roller, and then drying the conductive substrate at the temperature of 50-70 ℃ for 7-15 minutes and roasting the conductive substrate at the temperature of 470-530 ℃ for 13-24 minutes in the presence of oxygen at a high temperature to form the porous catalyst layer containing iridium dioxide, transition metal oxide and nano silicon dioxide particles.

9. The method according to claim 4, wherein the step (1) further comprises preparing a corrosion-resistant coating on the surface of the conductive substrate after the acid washing in the step (1), wherein the corrosion-resistant coating is an oxide of one or more of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum and tungsten, and the thickness of the corrosion-resistant coating is 0.1-2 μm.

10. The method according to claim 9, wherein the preparation of the corrosion resistant coating specifically comprises: and (2) cleaning and drying the acid-washed conductive substrate in the step (1), coating the conductive substrate with one or more salt compounds of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum and tungsten, and roasting and oxidizing the conductive substrate in an air furnace at 480-520 ℃.

Technical Field

The invention belongs to the field of industrial electrolysis, and particularly relates to an oxygen evolution anode for industrial electrolysis and a preparation method thereof.

Background

On one hand, the application and rapid development of the technologies of IT products, the internet of things, 5G communication and the like promote the development of the raw material copper-clad Printed Circuit Board (PCB) towards the direction of multilayering, thinning, high-density and high-speed high-frequency, and further the electrolytic copper foil is required to have the characteristics of higher performance, high function, high quality, high reliability and the like. On the other hand, with the development of lithium ion battery technology, higher requirements are put forward on the aspects of thinness, thickness consistency, flatness, tensile strength, oxidation resistance and the like of the electrolytic copper foil used as a negative electrode current collector. In order to meet the above requirements, various organic and inorganic additives are increasingly used in the production of electrolytic copper foil, and these additives, while improving the performance of electrolytic copper foil, are accompanied by various side reactions to accelerate the consumption of metal catalyst of oxygen evolution anode or the corrosion of conductive substrate, which puts higher demands on the production technology of oxygen evolution anode used in electrolytic copper foil.

The ion doping modification method becomes a conventional means for prolonging the service life of the oxygen evolution anode, and the methods of a sol-gel method, electrodeposition, magnetron sputtering, vapor deposition and the like are generally adopted to dope silicon dioxide, tantalum oxide, tin oxide and the like into a catalyst coating, improve partial characteristics of the catalyst and prolong the service life of the anode.

ZL200910099601.1 discloses a silica-doped modified insoluble iridium dioxide anode and a preparation method thereof, wherein a homogeneous sol-gel system is formed by silane and noble metal salt in a solvent, and an atomic-level mutual-doped active noble metal oxide/silica composite oxide coating is obtained on the surface of a titanium substrate after roasting. Through SiO₂The doped and modified insoluble anode coating has fine crystal grains, is porous, has high electrocatalytic activity and has longer service life.

Generally, a sol-gel method is adopted to prepare an introduced organosilane monomer or n-silane ethyl ester as a silicon source, so that mutual doping of silicon and iridium at an atomic level can be realized, and the effect of uniform dispersion is achieved. However, the organosilane material is high in cost, toxic and insoluble in water, the preparation period of the method is long, strict requirements are imposed on temperature rise and drop during plate coating and roasting, and if the plate is unevenly coated or the temperature rise and drop rate during roasting is too high, the catalyst coating is cracked, a substrate is exposed, and the service life of the plate is seriously influenced.

ZL201580060998.7 discloses an anode for oxygen generation, which forms a catalyst layer of at least one of an oxide, nitride and carbide of iridium and at least one of an oxide, nitride and carbide of at least one metal selected from the group consisting of elements of groups 4, 5 and 13 of the periodic table on the surface of a valve metal substrate, and produces an electrode having a small overvoltage and stable operation. However, when the component is used for preparing the catalyst layer, iridium dioxide and transition metal oxide serving as a framework structure and an adhesive cannot be uniformly mixed, and the iridium dioxide is separated among the distribution, so that the iridium oxide segregation phenomenon is generated. Thereby causing excessive consumption of iridium oxide during electrolysis, accelerating corrosion of the metal substrate, and shortening the life of the oxygen evolution electrode.

How to obtain an oxygen evolution anode which can better meet the industrial electrolysis requirement, has long electrolysis life and excellent performance becomes a technical problem to be solved urgently in the field.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide an oxygen evolving anode for industrial electrolysis and a method for its preparation.

In a first aspect, the present invention provides an oxygen evolving anode for industrial electrolysis comprising an electrically conductive substrate and a porous catalyst layer formed on the surface of said electrically conductive substrate;

the conductive substrate is one or more of valve metal and valve metal alloy;

the porous catalyst layer contains iridium dioxide, transition metal oxide and nano silicon dioxide particles;

the transition metal oxide is one or more oxides of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum, tungsten and tin.

Further, the valve metal is one or more of niobium, tantalum, titanium, zirconium, vanadium, tungsten, molybdenum, aluminum, hafnium, and steel.

Furthermore, the molar ratio of the iridium dioxide to the silicon dioxide is 0.2-5.0, and the particle size of the nano silicon dioxide particles is 2-100 nm.

Further, a corrosion resistant coating is formed between the surface of the conductive substrate and the porous catalyst layer;

the corrosion-resistant coating is one or more oxides of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum and tungsten,

the thickness of the corrosion-resistant coating is 0.1-2 mu m.

In a second aspect, the present invention also provides a method for preparing the above oxygen evolving anode, comprising the steps of:

the method comprises the following steps of (1) carrying out pretreatment on a conductive matrix, including cleaning, cutting, sand blasting, leveling and acid washing;

cleaning is primarily the cleaning of the conductive substrate for surface contaminants such as grease, chips, salts, and the like. Available cleaning methods include water washing, alkali washing, ultrasonic cleaning, steam cleaning, scrubbing, and the like;

drying and shearing the cleaned conductive substrate, and processing the conductive substrate into a required size;

then, the surface of the conductive substrate is roughened and an oxide film layer on the surface is damaged by a surface sand blasting or etching process, and the surface roughening treatment can enhance the bonding strength of a surface coating and improve the dispersion degree of electrolytic current;

the conducting substrate after the surface roughening treatment is subjected to acid cleaning and etching by using non-oxidizing acid such as hydrochloric acid, sulfuric acid, oxalic acid or mixed acid thereof under the condition of a boiling point or close to the boiling point or mixed solution of nitric acid and hydrofluoric acid under the condition of close to room temperature, so that an oxide film on the surface can be completely removed, sharp protrusions caused by the surface roughening treatment can be flattened, and meanwhile, surface pollutants can be more thoroughly cleaned; when the acid washing is completed, the conductive substrate is sufficiently washed to remove the residual acid, and sufficiently dried, and at this time, the residual acid can be removed by using purified water.

Step (2), preparing a solution of the porous catalyst layer: mixing an iridium dioxide precursor, a nano silicon dioxide particle precursor and a transition metal oxide precursor, adding the mixture into a 10-20% hydrochloric acid solution, and fully stirring;

the precursor of the iridium dioxide is a water-soluble salt compound containing trivalent iridium ions and/or tetravalent iridium ions;

the precursor of the nano silicon dioxide particles is water-soluble nano silicon dioxide sol with a grain size;

the precursor of the transition metal oxide is a water-soluble transition metal salt compound;

the water-soluble silica sol with the nano particle size can be stably distributed in an acid solution, and can be uniformly mixed and dispersed with precursors of iridium dioxide and transition metal oxide in a water phase;

hydrochloric acid, nitric acid and oxalic acid are added into the solution for preparing the porous catalyst layer to serve as stabilizing agents, and salicylic acid, 2-ethyl hexanoate, acetylacetone, EDTA, ethanolamine, citric acid and ethylene glycol can be optionally added to serve as complexing agents.

Step (3), coating preparation: coating the solution prepared in the step (2) on the surface of the conductive substrate treated in the step (1), drying, and then roasting at high temperature in the air to form the porous catalyst layer;

the high-temperature roasting temperature is 430-550 ℃, and the time is 10-30 minutes;

and (4) selecting the number of times of repeating the step (3) according to the thickness of the preset porous catalyst layer.

The coating method of the porous catalyst layer includes a thermal decomposition method, a sol-gel method, a slurry method, an electrophoresis method, a CVD method, a PVD method, and the like.

Further, the pretreatment of the conductive substrate specifically comprises:

immersing the conductive substrate into an aqueous solution dissolved with a cleaning agent and ethanol, and carrying out surface cleaning and oil removal through ultrasonic treatment for 12-18 minutes;

drying for 0.5-1.5 hours at the temperature of 55-65 ℃;

cutting according to the required size, performing sand blasting treatment, and performing tempering and leveling at 580-620 ℃ for 2.5-3.5 hours;

pickling in boiling hydrochloric acid aqueous solution for 18-25 minutes;

and cleaning and drying to obtain the treated conductive matrix.

Further, the mol percentage of the precursor of iridium dioxide to the precursor of the transition metal oxide is (55-90%): (10% -45%), wherein the molar ratio of the precursor of the iridium dioxide to the precursor of the nano silicon dioxide particles is 0.2-5.0;

further, the precursor of the nano silicon dioxide particle is prepared by the following steps:

exchanging the sodium silicate solution with cation exchange resin to prepare polysilicic acid mother liquor with small particle size;

adding elemental silicon powder treated by boiling water, and realizing the primary increase of the particle size of silica sol particles under the dual actions of hydrolysis reaction of the elemental silicon powder and dissolution reaction of the polysilicic acid mother liquor to prepare a first large-particle size silica sol crude product;

performing secondary growth on the basis of the first large-particle-size silica sol crude product to prepare a second large-particle-size silica sol crude product;

and removing impurities and concentrating the second large-particle-size silica sol crude product to obtain a precursor of the silica.

Further, the step (3) specifically includes:

and coating the prepared solution of the porous catalyst layer on the surface of the conductive substrate by using a roller, and then drying the conductive substrate at the temperature of 50-70 ℃ for 7-15 minutes and roasting the conductive substrate at the temperature of 470-530 ℃ for 13-24 minutes in the presence of oxygen at a high temperature to form the porous catalyst layer containing iridium dioxide, transition metal oxide and nano silicon dioxide particles.

By uniformly introducing the nano silicon dioxide particles into the catalyst coating, the uniform dispersion of the nano silicon dioxide particles, the iridium dioxide and the transition metal oxide is realized, the formation of a porous structure on the catalyst layer is promoted, the specific surface area is increased, and cracks are not easily formed.

Further, the step (1) also comprises preparation of a corrosion-resistant coating, wherein the corrosion-resistant coating is prepared on the surface of the conductive substrate after the acid washing in the step (1), the corrosion-resistant coating is one or more oxides of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum and tungsten, and the thickness of the corrosion-resistant coating is 0.1-2 μm.

Further, the preparation of the corrosion resistant coating specifically comprises: and (2) cleaning and drying the acid-washed conductive substrate in the step (1), coating the conductive substrate with one or more salt compounds of titanium, tantalum, niobium, zirconium, hafnium, vanadium, molybdenum and tungsten, and roasting and oxidizing the conductive substrate in an air furnace at 480-520 ℃.

The corrosion resistant coating can be formed by thermal decomposition, high temperature oxidation or ion plating. The corrosion-resistant coating can improve the corrosion resistance of the conductive matrix in the acid electrolyte, strengthen the interface bonding force of the porous catalyst layer and the conductive matrix and prolong the service life of the oxygen evolution anode.

The oxygen evolution anode of the invention introduces the inorganic binder with the diameter of several nanometers dispersed in the blue-white colloidal solution in the preparation of the catalyst layer solution, is nontoxic, tasteless, high temperature resistant and water soluble, and is uniformly mixed and dispersed with precursors of the silicon dioxide and the transition metal oxide in the water phase; finally, the formed catalyst layer realizes the uniform dispersion of the iridium dioxide, the transition metal oxide and the nano silicon dioxide particles, the catalyst layer has a porous structure, the surface area is increased, cracks are not easy to appear, and the catalyst layer can be widely applied to the electrolytic process of acidic and neutral solutions, so that the consumption rate of the iridium dioxide on the oxygen evolution anode is reduced, and the service life of the oxygen evolution electrode is prolonged.

Drawings

The above and other objects, features and advantages of exemplary embodiments of the present disclosure will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar or corresponding parts and in which:

FIG. 1 is a schematic diagram showing SEM examination results of an oxygen evolving anode according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing the hierarchical structure of an oxygen evolving anode according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

Example 1

In the embodiment of the invention, a conductive substrate is a pure titanium plate, is immersed in an aqueous solution dissolved with a cleaning agent and ethanol, and is subjected to surface cleaning and oil removal through ultrasonic treatment for 15 minutes; followed by drying at 60 ℃ for 1 hour; cutting according to the required size of the experimental sample piece, performing sand blasting treatment, and performing tempering leveling for 3 hours at 600 ℃; followed by an acid wash in boiling aqueous hydrochloric acid for 20 minutes. And washing the dried titanium plate, coating the titanium plate with hydrochloric acid solution of titanium chloride and tantalum chloride, and roasting and oxidizing the titanium plate in an air furnace at 480-520 ℃ to form the corrosion-resistant coating.

Respectively dissolving iridium tetrachloride, tantalum pentachloride and nano silicon dioxide sol into 10% hydrochloric acid solution, and fully stirring to prepare coating solution, wherein the molar ratio of iridium chloride to silicon dioxide is 1: 5; the prepared coating solution is coated on the surface of the titanium plate with the corrosion-resistant coating by using a roller, and then the titanium plate is dried at the temperature of 60 ℃ for 8-12 minutes and roasted at the temperature of 500 ℃ for 15-20 minutes under aerobic conditions at high temperature to form a porous catalyst layer (shown in figure 1) containing iridium oxide, tantalum oxide and nano silicon dioxide particles. The coating amount of each coating solution is about 0.9-1.2 g/m calculated by the surface density of iridium metal²The coating, drying and baking processes were repeated 12 times to obtain an areal density of iridium metal of 12g/m²The porous catalyst layer of (2), the porous catalyst layer obtained at this time is a hierarchical structure in which the conductive substrate, the corrosion resistant coating layer and the porous catalyst layer are arranged in this order (as shown in fig. 2).

The preparation method of the nano silica sol comprises the following steps:

(1) preparation of polysilicic acid mother liquor the aim of the preparation of the polysilicic acid mother liquor is to obtain a mother liquor having a particle size which is a base material for the particle size growth of the particles. Preparing sodium silicate nonahydrate solution with a certain concentration, slowly flowing into a pretreated ion exchange column, and performing sodium silicate ion exchange reaction and silicic acid self-polymerization reaction in the ion exchange column to obtain the polysilicic acid mother liquor.

The resin pretreatment steps are as follows: a. loading 001 × 7 type cation exchange resin into ion exchange column, washing with distilled water until effluent is clear; b. soaking the resin in saturated NaCl solution (the volume of the solution is 1.2-1.5 times of the volume of the resin), discharging the NaCl solution after 1-2 hours, and washing with distilled water until the effluent is colorless; c. soaking the resin in 5% NaOH solution (the volume of the solution is 1.2-1.5 times of the volume of the resin), discharging alkali liquor after 1 hour, and washing with distilled water until the remaining liquor is neutral; d. soaking the resin in 5% hydrochloric acid solution (the volume of the solution is 1.2-1.5 times of the volume of the resin), discharging the acid solution after 2 hours, and washing with distilled water until the effluent is neutral.

Adopting 3 percent sodium silicate solution by mass fraction at 0.5ml/cm²Min flow through the cation exchange resin bed, the resulting polysilicic acid mother liquor having an average particle size of 3.5nm and an impurity sodium ion concentration of 224.35X 10^-6g/g。

(2) And (3) increasing the nano silicon dioxide sol, and dividing the polysilicic acid mother liquor obtained in the step (1) into a mother liquor I and a mother liquor II. Taking the mother liquor I as a reaction base solution; the mother liquid II is slowly added, and new nuclei generated by dissolving the mother liquid II and new nuclei generated by hydrolyzing the elemental silicon powder jointly act with the mother nucleus of the mother liquid I to increase the particle size. The method comprises the following specific steps: adding 15g of elemental silicon powder activated by boiling water into a round-bottom flask, adding 80ml of distilled water and 15ml of 10% ammonia water, adding 0.2g of sodium dodecyl benzene sulfonate, polyhexanediol and 15ml of polysilicic acid mother liquor I, and adjusting the stirring speed to be 250 r/min. And (3) dripping mother liquor II after the temperature of the reaction system reaches 80 ℃, carrying out dissolution reaction to provide new silicic acid nuclei, controlling the feeding speed to be 2ml/min, dripping the mother liquor II to be 300ml, keeping the pH of the solution system to be 9, and controlling the reaction time to be 5 h.

(3) And (3) impurity removal and concentration of the silica sol product, wherein the elemental silicon powder possibly contains part of impurities, and a crude silica sol product needs to be prepared for impurity removal treatment. Passing the silica sol through anion and cation exchange resins in sequence to remove anion and cation impurities in the silica sol to obtain a high-purity silica sol product; on the other hand, the high purity silica sol obtained by ion exchange has a low silica content. The concentration of the silica sol product, i.e. the silica content of the product, needs to be increased by a concentration method.

Example 2

In this example, the same preparation method as in example 1 was used to prepare an oxygen evolution anode, and the same electrolytic life evaluation method was used to evaluate the life; this example differs from example 1 in that the molar ratio of iridium chloride to silica in the coating solution was 1: 1.

Example 3

In this example, the same preparation method as in example 1 was used to prepare an oxygen evolution anode, and the same electrolytic life evaluation method was used to evaluate the life; this example differs from example 1 in that the molar ratio of iridium chloride to silica in the coating solution was 5: 1.

Comparative example 1

In this comparative example, the oxygen evolution anode was prepared by the same method as in example 1, and the life evaluation was performed by the same electrolytic life evaluation method; the present comparative example differs from example 1 in that the coating solution does not contain silica, but only iridium chloride and tantalum chloride.

Comparative example 2

In this comparative example, the oxygen evolution anode was prepared by the same method as in example 1, and the life evaluation was performed by the same electrolytic life evaluation method; the present comparative example differs from example 1 in that the molar ratio of iridium chloride to silica in the coating solution was 6: 1.

Comparative example 3

In this comparative example, the oxygen evolution anode was prepared by the same method as in example 1, and the life evaluation was performed by the same electrolytic life evaluation method; the present comparative example is different from example 1 in that the molar ratio of iridium chloride to silica in the coating solution was 1: 6.

The oxygen evolution anodes prepared in the above manner were subjected to electrolytic life evaluation, respectively, with specific parameters as follows:

current density: 50kA/m²(ii) a The electrolysis temperature is as follows: 60 ℃; electrolyte solution: 150g/L sulfuric acid aqueous solution; counter electrode: a zirconium plate; the point at which the cell voltage increased by 1.0V from the initial voltage was regarded as electricityEnd of solution life.

By the same electrolytic life evaluation method, the results of comparing the electrolytic lives of examples 1 to 3, and comparative examples 1 to 3 were obtained as shown in table 1:

TABLE 1 list of electrolytic life

	Iridium oxide/silica molar ratio	Electrolytic life (hours)
			Example 1	1:5	1340
Example 2	1:1	1874
			Example 3	5:1	1258
Comparative example 1	1:0	975
			Comparative example 2	6:1	992
Comparative example 3	1:6	875

As can be seen from table 1, in examples 1 to 3, the addition of nanosilica to the catalyst to form the porous catalyst layer can effectively increase the lifetime of the oxygen evolution anode by about 2 times, compared with comparative example 1 in which nanosilica is not added, mainly because nanosilica effectively enhances the dispersibility of iridium oxide, and as a supplement to tantalum oxide having a framework structure, the problem of iridium oxide segregation is solved, the effective specific surface area of iridium oxide is increased, and the consumption rate of iridium oxide in electrolysis is reduced, thereby increasing the electrolytic lifetime of the electrode. Moreover, it is known from the examples 1 to 3 and the comparative examples 2 and 3 that the electrolytic life of the oxygen evolution anode is not improved when the molar ratio of iridium oxide to silica is lower than 1:5 or higher than 5:1, mainly because when the molar ratio of iridium oxide to silica is lower than 1:5, i.e. the content of silica is too high, the catalyst layer becomes dense, cracks are reduced, silica agglomerates and precipitates, the surface of the coating becomes whitish, the electrode potential of the coating is remarkably increased, and the catalytic activity is reduced or even lost. When the molar ratio of iridium oxide to silica is higher than 5:1, i.e., the silica content is too low, the catalyst layer has no significant change and no significant increase in catalytic activity and lifetime compared to a catalyst layer without silica.

The foregoing describes preferred embodiments of the present invention, and is intended to provide a clear and concise description of the spirit and scope of the invention, and not to limit the same, but to include all modifications, substitutions, and alterations falling within the spirit and scope of the invention as defined by the appended claims.