Iridium dioxide catalyst for electrolysis of water to produce hydrogen and preparation method thereof

Abstract

The present invention discloses an iridium dioxide catalyst for hydrogen production by electrolysis of water and a preparation method thereof. The preparation method comprises first dissolving an iridium precursor in water to form an iridium precursor solution, then uniformly mixing the iridium precursor solution with carbon black, an alcohol solvent, and an alkaline solution to obtain a mixed solution; adding a reducing agent to carry out a reduction reaction; filtering the reduced product, washing it with a filter press, and drying it to obtain an Ir / C catalyst; and heat-treating the obtained Ir / C catalyst in an oxygen-containing atmosphere to remove the carbon black, thereby obtaining an iridium dioxide catalyst. The present invention provides a process for preparing a catalyst for water electrolysis, utilizing liquid-phase reduction and high-temperature heat treatment to prepare a highly active IrO2 catalyst. The iridium particles have controllable particle size and exhibit high activity and stability. The preparation method is simple and easy to operate, facilitates the collection of iridium nanoparticles, and enables mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen production by electrolysis of water, and particularly relates to an iridium dioxide catalyst for hydrogen production by electrolysis of water and a preparation method thereof. Background Art

[0002] Affected by energy depletion and environmental pollution issues, the development and application of new energy represented by hydrogen energy is receiving widespread attention.

[0003] Hydrogen production by water electrolysis is the process of breaking the chemical bonds of water molecules through the action of electric potential to generate pure hydrogen and oxygen. It is essentially the conversion of electrical energy into chemical energy. The process is simple and has the advantages of high product purity and environmental protection.

[0004] In a full water electrolysis device, the catalyst is the primary site of the water electrolysis reaction, playing a key role in lowering the reaction energy barrier and increasing the reaction rate. It is a core component of the entire water electrolysis device. Currently, the most common anode catalysts in industry are precious metal oxides such as RuO2 and IrO2. IrO2 is currently the most popular anode catalyst due to its high activity and durability.

[0005] At present, the main preparation processes of industrial IrO2 include: Adams melting method, impregnation thermal decomposition method and sol-gel method.

[0006] Among them, the Adams melting method and the impregnation thermal decomposition method mainly dissolve and disperse the iridium precursor and polymer in the solution, and then prepare IrO2 particles by high-temperature thermal decomposition in the air.

[0007] The sol-gel method first prepares Ir and Ir(OH)2 colloidal particles in a solution, and then calcines them in air to obtain IrO2 particles.

[0008] The sol-gel method is a commonly used method for preparing precious metal catalysts, including nano-platinum and palladium. The particles prepared by it are often small in size; however, unlike platinum and palladium nanoparticles, iridium often exists in the form of a single metal, unlike platinum and palladium, which are usually loaded on a carrier. The result is that Ir nanoparticles are prone to agglomeration without the addition of a dispersant. Adding a dispersant will make the dispersant difficult to remove, and this process cannot be collected by processes such as filter presses. Centrifugation must be used, and mass production cannot be achieved.

[0009] For example, the invention with publication number CN1 14990576A discloses a preparation method and application of an IrO2 catalyst with a supported structure. The preparation method includes the following steps: 1) dispersing g-C3N4: preparing a g-C3N4 solution in an organic solvent; 2) adding an iridium (Ir) precursor aqueous solution to the carbon nitride solution prepared in step 1) to obtain a mixed solution; 3) adjusting the acidity of the mixed solution prepared in step 2) to the alkaline region, stirring and precipitating; 4) placing the precipitate obtained in step 3) in a muffle furnace for sintering to form an IrO2 / g-C3N4 composite nanocatalyst.

[0010] Loading precious metals onto a carrier is a conventional method for preparing small-sized nanoparticles. A suitable carrier can improve the dispersion of precious metals, forming nanoparticles with uniform particle size. In addition, the presence of the carrier allows the precious metal catalyst to be obtained by filter pressing, making it easy to achieve mass production. Summary of the Invention

[0011] The present invention provides a water electrolysis catalyst and a preparation method thereof. Iridium nanoparticles are loaded on a suitable carbon carrier by a liquid phase reduction method, and then the carbon particles are removed under high temperature, thereby finally achieving the preparation of a highly active IrO2 catalyst.

[0012] The present invention first provides a method for preparing an iridium dioxide catalyst for electrolyzing water to produce hydrogen, comprising the following steps:

[0013] (1) dissolving an iridium precursor in water to prepare an iridium precursor solution, and then uniformly mixing the iridium precursor solution with carbon black, an alcohol solvent, and an alkali solution to obtain a mixed solution;

[0014] (2) adding a reducing agent to the mixed solution obtained in step (1) to carry out a reduction reaction;

[0015] (3) filtering the reduced product obtained in step (2), washing it with a filter press, and drying it to obtain an Ir / C catalyst;

[0016] (4) The Ir / C catalyst obtained in step (3) is heat-treated in an oxygen-containing atmosphere to remove carbon black and obtain an iridium dioxide catalyst.

[0017] Preferably, the iridium precursor is at least one of chloroiridic acid, iridium trichloride, and iridium acetylacetonate.

[0018] Preferably, the mass concentration of the iridium precursor solution is 5% to 20%.

[0019] Preferably, the carbon black is at least one of Cabot FCX800 and Toyo Tanso MH-1800;

[0020] The alcohol solvent is at least one of ethanol, isopropanol, and ethylene glycol;

[0021] The alkali solution is at least one of sodium carbonate solution, sodium hydroxide solution and ammonia solution;

[0022] The reducing agent is at least one of formic acid and formaldehyde.

[0023] Preferably, the mass percentage of Ir in the Ir / C catalyst obtained in step (3) is 20% to 60%. More preferably, the mass percentage of Ir in the Ir / C catalyst obtained in step (3) is 30% to 40%.

[0024] Preferably, the mass ratio of carbon black to alcohol solvent is 1:10 to 100. More preferably, the mass ratio of carbon black to alcohol solvent is 1:50.

[0025] The mass concentration of the alkali solution is 10%-20%, the mass ratio of carbon black to the alkali solution is 1:5-30, and the mass ratio of the iridium precursor to the alkali solution is 1:1-10.

[0026] Preferably, the reduction reaction in step (2) is carried out at a temperature of 70-90° C. for 1-4 hours, and more preferably at a temperature of 80° C. for 2 hours.

[0027] The heat treatment temperature in step (4) is 400-600° C. for 2-4 hours. More preferably, the heat treatment temperature is 450° C. for 2 hours. During the heat treatment, the carbon black serving as a carrier is removed, so the final product obtained is only iridium dioxide. The oxygen-containing atmosphere in step (4) can be an air atmosphere or an oxygen atmosphere.

[0028] The present invention further provides an iridium dioxide catalyst prepared by the preparation method and used for electrolyzing water to produce hydrogen.

[0029] The present invention also provides application of the iridium dioxide catalyst in producing hydrogen by electrolysis of water.

[0030] Beneficial effects of the present invention:

[0031] The present invention provides a process for preparing a catalyst for water electrolysis, which adopts liquid phase reduction and high-temperature heat treatment to prepare a highly active IrO2 catalyst. The particle size of the iridium particles is controllable and the activity and stability are high. The preparation method is simple and easy to operate, facilitates the collection of iridium nanoparticles, and can realize batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a graph showing the LSV performance of the catalysts prepared in Examples 1-5 of the present invention and Comparative Example 1 in the electrolyte.

[0033] Figure 2 This is the TEM spectrum of the catalyst of Example 2 of the present invention.

[0034] Figure 3 TEM spectrum of the catalyst in Comparative Example 1. DETAILED DESCRIPTION

[0035] Example 1

[0036] The present invention provides a catalyst for water electrolysis and a preparation method thereof, comprising the following steps:

[0037] 1. Dissolve chloroiridic acid in deionized water to prepare a 10% chloroiridic acid solution. Weigh 2.1 g of 10% chloroiridic acid solution, 0.4 g of Cabot FCX800 carbon black, 20 g of ethylene glycol, and 2 g of 10% sodium carbonate aqueous solution in a beaker and disperse with an ultrasonic rod for 30 minutes.

[0038] 2. Place the ultrasonicated mixed solution in a three-necked flask, add 0.2 g of formic acid, and then place it in a water bath and react with magnetic stirring at 80°C for 2 hours.

[0039] 3. After the reaction is completed, the solution is filtered and washed, and then placed in an air drying oven and dried at 70° C. for 3 hours to obtain an Ir / C catalyst with an iridium mass percentage of 20%.

[0040] 4. The obtained Ir / C catalyst was placed in a tubular furnace, air was introduced, and heat-treated at 450°C for 2 hours. After natural cooling, the catalyst was washed and filtered with deionized water, and then dried in air at 70°C to obtain the desired IrO2 catalyst, which was marked as IrO2-20%.

[0041] Example 2

[0042] 1. Dissolve chloroiridic acid in deionized water to prepare a 10% chloroiridic acid solution. Weigh 3.15 g of 10% chloroiridic acid solution, 0.35 g of Cabot FCX800 carbon black, 17.5 g of ethylene glycol, and 3 g of 10% sodium carbonate aqueous solution in a beaker and disperse with an ultrasonic rod for 30 minutes.

[0043] 2. Place the ultrasonicated mixed solution in a three-necked flask, add 0.3 g of formic acid, and then place it in a water bath and react with magnetic stirring at 80°C for 2 hours.

[0044] 3. After the reaction is completed, the solution is filtered and washed, and then placed in an air drying oven and dried at 70° C. for 3 hours to obtain an Ir / C catalyst with an iridium mass percentage of 30%.

[0045] 4. The obtained Ir / C catalyst was placed in a tube furnace, air was introduced, and heat-treated at 450°C for 2 hours. After natural cooling, the catalyst was washed and filtered with deionized water, and then dried in air at 70°C to obtain the desired IrO2 catalyst, which was marked as IrO2-30%.

[0046] Example 3

[0047] 1. Dissolve chloroiridic acid in deionized water to prepare a 10% chloroiridic acid solution. Weigh 4.2 g of 10% chloroiridic acid solution, 0.3 g of Cabot FCX800 carbon black, 15 g of ethylene glycol, and 4 g of 10% sodium carbonate aqueous solution into a beaker and disperse with an ultrasonic rod for 30 minutes.

[0048] 2. Place the ultrasonicated mixed solution in a three-necked flask, add 0.4 g of formic acid, and then place it in a water bath and react with magnetic stirring at 80°C for 2 hours.

[0049] 3. After the reaction is completed, the solution is filtered and washed, and then placed in an air drying oven and dried at 70° C. for 3 hours to obtain an Ir / C catalyst with an iridium mass percentage of 40%.

[0050] 4. The obtained Ir / C catalyst was placed in a tubular furnace, air was introduced, and heat-treated at 450°C for 2 hours. After natural cooling, the catalyst was washed and filtered with deionized water, and then dried in air at 70°C to obtain the desired IrO2 catalyst, which was marked as IrO2-40%.

[0051] Example 4

[0052] 1. Dissolve chloroiridic acid in deionized water to prepare a 10% chloroiridic acid solution. Weigh 5.25 g of 10% chloroiridic acid solution, 0.25 g of Cabot FCX800 carbon black, 12.5 g of ethylene glycol, and 5 g of 10% sodium carbonate aqueous solution into a beaker and disperse with an ultrasonic rod for 30 minutes.

[0053] 2. Place the ultrasonicated mixed solution in a three-necked flask, add 0.5 g of formic acid, and then place it in a water bath and react with magnetic stirring at 80°C for 2 hours.

[0054] 3. After the reaction is completed, the solution is filtered and washed, and then placed in an air drying oven and dried at 70° C. for 3 hours to obtain an Ir / C catalyst with an iridium mass percentage of 50%.

[0055] 4. The obtained Ir / C catalyst was placed in a tube furnace, air was introduced, and heat-treated at 450°C for 2 hours. After natural cooling, the catalyst was washed and filtered with deionized water, and then dried in air at 70°C to obtain the desired IrO2 catalyst, which was marked as IrO2-50%.

[0056] Example 5

[0057] 1. Dissolve chloroiridic acid in deionized water to prepare a 10% chloroiridic acid solution. Weigh 6.3 g of 10% chloroiridic acid solution, 0.2 g of Cabot FCX800 carbon black, 10 g of ethylene glycol, and 6 g of 10% sodium carbonate aqueous solution into a beaker and disperse using an ultrasonic rod for 30 minutes.

[0058] 2. Place the ultrasonicated mixed solution in a three-necked flask, add 0.6 g of formic acid, and then place it in a water bath and react with magnetic stirring at 80°C for 2 hours.

[0059] 3. After the reaction is completed, the solution is filtered and washed, and then placed in an air drying oven and dried at 70° C. for 3 hours to obtain an Ir / C catalyst with an iridium mass percentage of 60%.

[0060] 4. The obtained Ir / C catalyst was placed in a tubular furnace, air was introduced, and heat-treated at 450°C for 2 hours. After natural cooling, the catalyst was washed and filtered with deionized water, and then dried in air at 70°C to obtain the desired IrO2 catalyst, which was marked as IrO2-60%.

[0061] Comparative Example 1

[0062] 1. Dissolve chloroiridic acid in deionized water to prepare a 10% chloroiridic acid solution. Weigh 10.5 g of 10% chloroiridic acid solution, 20 g of ethylene glycol, and 10 g of 10% sodium carbonate aqueous solution into a beaker and disperse with an ultrasonic rod for 30 minutes.

[0063] 2. Place the ultrasonicated mixed solution in a three-necked flask, add 1 g of formic acid, and then place it in a water bath and react with magnetic stirring at 80°C for 2 hours.

[0064] 3. After the reaction is completed, the solution is centrifuged and washed, and then placed in an air drying oven and dried at 70°C for 3 hours.

[0065] 4. Place the dried catalyst in a tubular furnace, introduce air, and heat treat at 450°C for 2 hours. After cooling naturally, wash and filter the catalyst with deionized water, and then dry it in air at 70°C to obtain the desired IrO2 catalyst, which is marked as IrO2.

[0066] Test Example 1

[0067] The catalysts prepared in Examples 1-5 and Comparative Example 1 were subjected to electrochemical performance tests under the same conditions. The test method is as follows: 5 mg of catalyst was accurately weighed into a 50 mL brown glass bottle, and 5 mL of the prepared Nafion isopropanol solution was added to the weighed catalyst; ultrasonic sonication was performed for 30 minutes to mix the slurry evenly; 5 μL of the dispersed slurry was pipetted with a pipette and evenly added dropwise to the surface of a smooth and clean disk electrode, which was allowed to dry completely under an infrared lamp to serve as the working electrode; the electrode was placed in an electrolytic cell to form a three-electrode system. The reference electrode was a calomel electrode, the counter electrode was a Pt wire electrode, and the electrolyte was an O2-saturated 0.5 mol / L H2SO4 solution.

[0068] Under the condition of constant temperature of 25℃, the catalyst-coated working electrode was immersed in the electrolyte and the electrolyte was charged at 200mv.s -1 Perform cyclic voltammetry to activate the electrode, then adjust the disk electrode speed to 1600 rpm and use 5 mv.s -1 The scan rate was scanned from low potential to high potential, and each sample was tested 3 times. The test voltage range was 1.0-1.8V (Vs RHE). The RHE electrode is a reversible hydrogen electrode, a common electrode in electrochemical testing. The reading was 10mA / cm 2 The voltage value was tested under the current density to specifically evaluate the oxygen evolution reaction (OER) activity of the catalyst.

[0069] Table 1 Voltage statistics of Examples 1-5 and Comparative Example 1 at a current density of 10 mA / cm2

[0070]

[0071]

[0072] From Table 1 and Figure 1 The test data show that compared with the comparative example 1, the IrO2 catalysts prepared by Examples 1-5 of the present invention have better OER performance than the experimental data of the comparative example 1 at a specific current density, especially Example 2, which has a higher OER performance at 10 mA / cm 2 Under current density, its voltage is 1.639V, which is 0.161V lower than 1.8V of comparative example 1. This shows that the process of loading Ir on a carbon carrier and then calcining and removing carbon is beneficial to improving the performance of IrO2 electrolysis of water. By preparing Ir / C, the agglomeration of Ir and its oxides during reduction and crystal formation and the rapid increase in particle size are avoided, thereby improving the catalyst activity.

[0073] For Examples 1-5, during the preparation of Ir / C, the different mass of the carbon support also had a significant impact on the final IrO2 performance. The OER performance of the catalysts in Examples 2 and 3 was significantly better than that in Examples 1, 4, and 5. This result may be due to the influence of the carbon support pore structure and the amount of functional groups on the support surface on the distribution and dispersion of Ir on the support surface. The carbon support has a certain mesoporous structure and a certain amount of oxygen-containing functional groups such as hydroxyl and carboxyl groups on its surface. The performance of Example 1 was slightly weaker than that of Examples 2 and 3. This may be because some Ir particles entered the pores of the carbon support, resulting in a reduction in the surface active material. The performance of the catalysts in Examples 4 and 5 was slightly worse. This may be because the Ir content was too high, and the number of functional groups on the carbon support surface was insufficient to evenly anchor the metal Ir to the support surface, resulting in a certain amount of agglomeration of the active metal Ir on the carbon support surface, resulting in reduced catalytic activity. Therefore, according to the present application, when preparing Ir / C, it is recommended to use Ir / C with a mass percentage of iridium of 30% or 40%.

[0074] Test Example 2

[0075] The microstructure or crystal structure of the catalysts prepared in Example 2 and Comparative Example 1 was observed using a transmission electron microscope.

[0076] Depend on Figure 2 and Figure 3 It can be seen that the morphology and particle size of IrO2 obtained are different due to different preparation processes. Figure 2 The IrO2 prepared in Example 2 is mostly rutile, has no obvious agglomeration phenomenon, and has a small particle size; Figure 3 The IrO2 prepared in Comparative Example 1 shows severe agglomeration in the TEM spectrum, with a significantly increased particle size and an unclear crystal form. Both anatase and rutile are present, which is the main reason why Comparative Example 1 performs poorly in OER.

Claims

1. A method for preparing an iridium dioxide catalyst for producing hydrogen by electrolysis of water, characterized in that: The following steps are involved: (1) dissolving an iridium precursor in water to prepare an iridium precursor solution, and then uniformly mixing the iridium precursor solution with carbon black, an alcohol solvent, and an alkali solution to obtain a mixed solution; (2) adding a reducing agent to the mixed solution obtained in step (1) to carry out a reduction reaction; (3) filtering the reduction product obtained in step (2), washing it, and drying it to obtain an Ir / C catalyst; the mass percentage of Ir in the obtained Ir / C catalyst is 30% to 40%; (4) heat-treating the Ir / C catalyst obtained in step (3) in an oxygen-containing atmosphere to remove carbon black and obtain an iridium dioxide catalyst; The mass ratio of carbon black to alcohol solvent is 1:10-100; the mass concentration of alkali solution is 10%-20%, and the mass ratio of carbon black to alkali solution is 1:5-30; The reduction reaction temperature in step (2) is 70-90°C and the time is 1-4 hours; The heat treatment temperature in step (4) is 400-600°C and the time is 2-4 hours.

2. The method for preparing an iridium dioxide catalyst for producing hydrogen by electrolysis of water according to claim 1, wherein: The iridium precursor is at least one of chloroiridic acid, iridium trichloride, and iridium acetylacetonate.

3. The method for preparing an iridium dioxide catalyst for producing hydrogen by electrolysis of water according to claim 1, wherein: The mass concentration of the iridium precursor solution is 5%~20%.

4. The method for preparing an iridium dioxide catalyst for producing hydrogen by electrolysis of water according to claim 1, wherein: The carbon black is at least one of Cabot FCX800 and Toyo Tanso MH-1800; The alcohol solvent is at least one of ethanol, isopropanol, and ethylene glycol; The alkali solution is at least one of sodium carbonate solution, sodium hydroxide solution and ammonia solution; The reducing agent is at least one of formic acid and formaldehyde.

5. An iridium dioxide catalyst for producing hydrogen by electrolysis of water prepared by the arbitrary preparation method of claims 1 to 4.

6. Use of the iridium dioxide catalyst according to claim 5 in producing hydrogen by electrolysis of water.

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