Preparation method of tin-doped iridium dioxide anode catalyst

Abstract

The invention provides a preparation method of a tin-doped iridium dioxide anode catalyst, and belongs to the field of hydrogen production through water electrolysis. The preparation method comprises the following steps: dissolving an iridium trichloride raw material and a tin source in water, adding sodium hydroxide to adjust the pH value of the solution, fully stirring, transferring the stirred solution to a reaction kettle, heating to 120-160 DEG C, introducing oxygen to carry out pressurized oxidation, carrying out centrifugal filtration and washing on an oxidation product obtained after the reaction by using a sulfuric acid solution, deionized water and ethanol in sequence, and drying to obtain the iridium trichloride tin oxide. And obtaining an anode catalyst product. The tin-doped iridium dioxide catalyst is prepared in an aqueous solution system, the process is simple, the product performance is stable, the process is clean and free of pollution, and compared with a commercial catalyst, the overpotential of the obtained doped catalyst is reduced by 30 mV or above under the current density of 10 mA / cm < 2 >.

Description

Technical Field

[0001] The present invention relates to the field of anode catalysts for hydrogen production by electrolysis of water, and in particular to a method for preparing a tin-doped iridium dioxide catalyst for anodes of PEM water electrolysis for hydrogen production. Technical Background

[0002] The overexploitation and application of traditional fossil energy sources has not only caused serious environmental pollution but also hindered the transformation of my country's energy structure. Therefore, there is an urgent need to develop new green, low-carbon, and environmentally friendly energy sources to gradually replace traditional fossil energy. Against this backdrop, my country has begun to continuously promote the development and application of new clean energy sources such as wind, solar, and hydropower. However, these energy sources all have certain disadvantages, such as the intermittent nature of solar and wind power generation and the seasonal nature of hydropower generation. These characteristics limit their continuous power supply and lead to waste of resources.

[0003] Hydrogen energy has the advantages of being clean, environmentally friendly, renewable, and abundant in resources. At the same time, hydrogen energy can reduce dependence on fossil fuels and improve the security of energy supply. Due to these advantages of hydrogen energy, it is widely considered to be the key to replacing traditional fossil energy in the future and solving environmental and resource problems. Traditional hydrogen production methods include: water electrolysis to produce hydrogen, alkane cracking to produce hydrogen and other technologies. Among the many hydrogen production technologies, water electrolysis to produce hydrogen is simple and clean, and is considered to be one of the main technologies for hydrogen production in the future. During the water electrolysis process, unstable and discontinuous electrical energy can be converted into stable hydrogen energy and stored in hydrogen gas. When hydrogen energy is converted into electrical energy, it can provide continuous and stable energy. In the process of converting electrical energy into hydrogen energy, not only is the waste of electrical energy reduced, but the recycling of clean energy is also achieved.

[0004] The electrolysis of water is divided into oxygen evolution half-reaction and hydrogen evolution half-reaction, which together constitute the full reaction of electrolysis of water. The process is shown in the following reaction formula:

[0005] Oxygen evolution reaction:

[0006] Hydrogen evolution reaction: 2H + +2e - →H2(2)

[0007] Overall reaction:

[0008] Among them, the hydrogen evolution reaction (HER) reaction process is relatively rapid, while the oxygen evolution reaction (OER) reaction process is relatively complex and the kinetic process is slow. It is the controlling step of the overall water electrolysis reaction. Therefore, the reaction rate of OER directly affects the speed of water electrolysis. Therefore, studying an OER catalyst with high catalytic efficiency, low cost and good stability has become the key to solving the problem of water electrolysis. Currently, the catalysts that are studied more are mainly platinum group metal catalysts, mainly including precious metals such as Ir and Ru and their oxides. However, the small amount of such precious metals on the earth and their high price limit their industrial application. Therefore, many researchers began to explore the possibility of large-scale application of precious metal-doped non-precious metal catalysts. In this process, researchers found that after transition metals such as Mn, Sn, Co are doped into precious metal catalysts, the catalyst material can be micro-modified, while improving the catalytic performance of the material, reducing the amount of precious metals and further reducing costs.

[0009] Many researchers have proposed different treatment methods to prepare high-performance iridium dioxide-doped catalysts. Traditional methods for preparing iridium dioxide include thermal decomposition and the Adams method. The thermal decomposition method involves first mixing an Ir-containing precursor salt and a transition metal salt in a certain proportion in an organic solution, then evenly coating the mixed solution on a Ti plate, drying it, briefly sintering it, and repeating the above steps until the coating solution is exhausted. The catalyst is then sintered and oxidized to obtain the catalyst. The Adams method involves first mixing an Ir-containing precursor salt, a transition metal salt, and sodium nitrate in a solution, then evaporating the mixed solution to obtain a solid mixture. This solid mixture is then calcined at high temperature to obtain IrO2-doped particles and water-soluble Na salts. The soluble salts are then washed off to obtain metal oxide powder. (Y.Murakami,S.Tsuchiya,K.Yahikozawa,etal.Preparation of ultrafine RuO2and IrO2 particles by a sol-gel process[J].Journal of materials science letters,1994,13(24):1773-1774.)

[0010] Thermal decomposition and Adams methods are highly regarded for their mature technology and low production difficulty, but they each face some problems that cannot be ignored. Thermal decomposition requires an aging time of more than 10 hours during production, which results in a longer production cycle and lower efficiency. Adams method will inevitably produce toxic NO during the production process. xGas, increasing environmental treatment costs. In addition, the production processes of these two methods are relatively cumbersome and costly, making it difficult to meet the current urgent demand for cost-effective and environmentally friendly production. (Hu Jiezhen. Preparation and application of oxide anodes containing iridium titanium oxide intermediate layer [D]. Ocean University of China, 2009; Povia M, Abbott DF, Herranz J, et al. Operando X-ray characterization of high surface area iridium oxides to decouple their activity losses for the oxygen evolution reaction [J]. Energy and Environmental Science, 2019, 12(10): 3038-3052) Summary of the Invention

[0011] In response to the shortcomings of the prior art, the present invention aims to provide a method for preparing a tin-doped iridium dioxide catalyst for use as an anode catalyst in hydrogen production by water electrolysis. The specific process and technical parameters are as follows:

[0012] 1. Solution Preparation

[0013] According to the mass ratio of iridium to tin in iridium trichloride and tin source being 3-6:1, a certain mass of iridium trichloride and tin source are weighed and added into pure water, and the concentration of iridium trichloride is controlled to be 2.0-5.0 g / L. After stirring and dissolving, a sodium hydroxide solution with a concentration of 20-60 g / L is added dropwise into the mixed solution, and the pH value of the mixed solution is adjusted to be between 12.2 and 13.2. After the pH is stabilized for 10-20 minutes, the solution is transferred into a high-pressure reactor.

[0014] 2. Pressurized oxidation

[0015] Introduce oxygen into the autoclave to drive out nitrogen. When the nitrogen concentration in the autoclave is lower than 1 vol%, close the air inlet and outlet of the autoclave, heat it to 120-160°C, introduce oxygen into the autoclave again, control the oxygen partial pressure in the autoclave to 0.5-0.7 MPa, and stir the solution at a rate of 200-400 rpm for 60-240 minutes. Then stop heating and stirring. When the temperature in the autoclave drops to 50°C, remove the reaction slurry. 3. Centrifugal filtration and washing

[0016] The slurry after the reaction is centrifuged and filtered, and the solid oxidation product obtained by centrifugation is centrifugally washed three times with a 0.1-0.5 mol / L H2SO4 solution, pure water and ethanol in sequence, with each centrifugal washing time being 10-20 minutes, a washing temperature being 20-25°C, and a washing speed being 5000-10000 rpm; the washed product is dried at 65-80°C for 6-8 hours to obtain an IrO2·SnO2 catalyst product.

[0017] The sodium hydroxide and iridium trichloride are both analytically pure reagents; the tin source is at least one of stannous chloride, tin tetrachloride, and sodium stannate; and the purity of the oxygen is not less than 99.99%.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The pressure oxidation method can promote the full conversion of iridium and tin ions into IrO2·SnO2, with a product yield of more than 99%, which reduces the amount of iridium and significantly improves the electrochemical performance of the catalyst. The obtained doped catalyst is better than the commercial catalyst at 10 mA / cm 2 (1) The overpotential at a current density of 1000 nm is reduced by more than 30 mV; (2) The impurity ions in the catalyst can be removed by centrifugal washing with sulfuric acid solution, pure water and ethanol, thereby improving the stability of the catalyst; (3) Compared with the traditional thermal decomposition method and Adams method, this process is simple to operate, has stable product quality, and is clean and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a process flow chart for preparing the IrO2·SnO2 catalyst of the present invention.

[0020] Figure 2 LSV diagrams of the IrO2·SnO2 catalysts prepared in Example 2 and Comparative Example 3 of the present invention and a commercial IrO2 catalyst under nitrogen atmosphere.

[0021] Figure 3 This is the XRD pattern of the IrO2·SnO2 catalyst prepared in Example 2 of the present invention.

[0022] Figure 4 This is a scanning electron microscope image of the IrO2·SnO2 catalyst prepared in Example 2 of the present invention.

[0023] Figure 5 This is a stability test chart of the IrO2·SnO2 catalyst prepared in Example 2 of the present invention and a commercial IrO2 catalyst. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict.

[0025] The process flow chart of the embodiment of the present invention is as follows Figure 1 shown.

[0026] Example 1:

[0027] First, weigh 0.14g of IrCl3·3H2O and 0.032g of SnCl2·2H2O into a 100ml beaker. Then, add 30ml of deionized water to the beaker and stir at 400rpm for 10 minutes. Then, add 20g / L aqueous NaOH to adjust the pH of the mixed solution to 12.8. Stirring was continued until the pH stabilized for 10 minutes. The mixed solution was then transferred to an autoclave.

[0028] Oxygen was introduced into the high-pressure reactor to drive out nitrogen. When the nitrogen concentration in the reactor was lower than 1 vol%, the air inlet and outlet of the reactor were closed, and the temperature was raised to 120°C. Oxygen was introduced into the reactor again, and the oxygen partial pressure in the reactor was controlled to 0.5 MPa. The stirring speed was 400 rpm and the holding time was 60 min.

[0029] After the reaction is completed, the reaction slurry is centrifuged to obtain a solid oxidation product, which is then centrifuged and washed with 0.2 mol / L H2SO4 solution, pure water, and ethanol in sequence at a centrifugal speed of 5500 rpm, for 15 min, and at a temperature of 20°C. The washed product is dried at 70°C for 6 h to obtain a tin-doped iridium dioxide catalyst.

[0030] The tin-doped iridium dioxide catalyst prepared in this example was subjected to redox testing using a three-electrode system: + / H2 as reference electrode,

[0031] Platinum wire was used as the counter electrode, the electrolyte was 0.5 mol / L H2SO4 solution, and the purity of the nitrogen used in the test was not less than 99.99%.

[0032] Example 2:

[0033] First, weigh 0.42g of IrCl3·3H2O and 0.012g of SnCl4·5H2O into a 100ml beaker. Then, add 50ml of deionized water to the beaker and stir at 400rpm for 20 minutes. Then, adjust the pH of the mixed solution to 12.5 by adding a 40g / L aqueous solution of NaOH. Stirring was continued until the pH stabilized for 15 minutes. The mixed solution was then transferred to an autoclave.

[0034] Oxygen was introduced into the high-pressure reactor to drive out nitrogen. When the nitrogen concentration in the reactor was lower than 1 vol%, the air inlet and outlet of the reactor were closed, and the temperature was raised to 140°C. Oxygen was introduced into the reactor again, and the oxygen partial pressure in the reactor was controlled to be about 0.5 MPa. The stirring speed was 400 rpm and the holding time was 120 min.

[0035] After the reaction is completed, the reaction slurry is centrifuged to obtain a solid oxidation product, which is then centrifuged and washed with 0.5 mol / L H2SO4 solution, pure water, and ethanol in sequence at a centrifugal speed of 6000 rpm, for 12 min, and at a temperature of 25°C. The washed product is dried at 75°C for 7 h to obtain a tin-doped iridium dioxide catalyst.

[0036] The tin-doped iridium dioxide catalyst prepared in this example was subjected to redox testing using a three-electrode system: + / H2 as the reference electrode, platinum wire as the counter electrode, the electrolyte is 0.5mol / L H2SO4 solution, and the purity of the nitrogen used in the test is not less than 99.99%. The LSV diagram, XRD diagram, scanning electron microscope diagram and stability test results of the IrO2·SnO2 catalyst prepared in this Example 2 under nitrogen atmosphere are shown as follows: Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 shown.

[0037] Example 3:

[0038] First, weigh 0.23g of IrCl3·3H2O, 0.021g of Na2SnO3·3H2O, and 0.031g of SnCl2·2H2O into a 100ml beaker. Then, add 40ml of deionized water to the beaker and stir at 400 rpm for 30 minutes. Then, add 60g / L of NaOH solution to adjust the pH of the mixed solution to 13.0. Stirring was continued until the pH stabilized for 20 minutes. The mixed solution was then transferred to an autoclave.

[0039] Oxygen was introduced into the high-pressure reactor to drive out nitrogen. When the nitrogen concentration in the reactor was lower than 1 vol%, the air inlet and outlet of the reactor were closed, and the temperature was raised to 160°C. Oxygen was introduced into the reactor again, and the oxygen partial pressure in the reactor was controlled to 0.7 MPa. The stirring speed was 200 rpm and the holding time was 60 min.

[0040] After the reaction is completed, the reaction slurry is centrifuged to obtain a solid oxidation product, which is then centrifuged and washed with 0.2 mol / L H2SO4 solution, pure water, and ethanol in sequence at a centrifugal speed of 8000 rpm, for 20 min, and at a temperature of 20°C. The washed product is dried at 80°C for 6 h to obtain a tin-doped iridium dioxide catalyst.

[0041] The tin-doped iridium dioxide catalyst prepared in this example was subjected to redox testing using a three-electrode system: + / H2 is used as the reference electrode, platinum wire is used as the counter electrode, the electrolyte is 0.5mol / L H2SO4 solution, and the purity of the nitrogen used in the test is not less than 99.99%.

[0042] The electrochemical test methods of Examples 2 and 3 are the same as those of Example 1. The specific electrochemical test results are shown in Table 1.

[0043] Comparative Example 1

[0044] Example 2 was repeated, except that in step 1, the pH was adjusted to 10.0 using sodium hydroxide.

[0045] Comparative Example 2

[0046] Example 2 was repeated, with the only difference being that in step 3, only pure water was used for centrifugal washing.

[0047] Comparative Example 3

[0048] Example 2 was repeated, except that the stirring speed in step 2 was 0 rpm.

[0049] Comparative Example 4

[0050] Example 2 was repeated, with the only difference being that in step 2, the oxygen pressure was controlled to be 0.2 MPa.

[0051] Comparative Example 5

[0052] Example 2 was repeated, except that the centrifugal filtration and washing speed in step 3 was 4000 rpm.

[0053] Table 1 shows the electrochemical test results of the catalysts described in Examples 1 to 3 and Comparative Examples 1 to 5. As can be seen from the table, controlling conditions such as oxygen partial pressure, solution pH, centrifugal washing method, stirring speed, and reaction temperature can help improve catalyst activity and cycle stability.

[0054] Furthermore, according to the comparison between Examples 1 to 3, Comparative Examples 1 to 5 and commercial catalysts, the catalytic activity and cyclic stability of the commercial iridium dioxide catalyst are poorer than those of the present application, indicating that the tin-doped iridium dioxide catalyst of the present application has better catalytic activity and cyclic stability.

[0055] Table 1 Electrochemical test results of Examples 1 to 3, Comparative Examples 1 to 5, and commercial catalysts

[0056]

[0057]

Claims

1. A method for preparing a tin-doped iridium dioxide anode catalyst, characterized in that The following steps are involved: (1) Solution preparation Weigh iridium trichloride and a tin source according to a mass ratio of iridium to tin in the iridium trichloride and tin source of 3 to 6:1, add them to pure water, control the concentration of iridium trichloride to 2.0 to 5.0 g / L, stir and dissolve, add a sodium hydroxide solution with a concentration of 20 g / L to 60 g / L dropwise to the mixed solution, adjust the pH value of the mixed solution to 12.2 to 13.2, and transfer the solution to an autoclave; (2) Pressurized oxidation Oxygen is introduced into the high-pressure reactor to drive out nitrogen. When the nitrogen concentration in the reactor is lower than 1 vol%, the air inlet and outlet of the reactor are closed, and the temperature is raised to 120-160° C., oxygen is introduced into the reactor again, and the oxygen partial pressure in the reactor is controlled to be 0.5-0.7 MPa. After stirring the solution at a rate of 200-400 rpm for 60-240 minutes, heating and stirring are stopped. When the temperature in the reactor drops to 50° C., the slurry after the reaction is taken out; (3) Centrifugal filtration and washing The reaction slurry is centrifugally filtered, and the solid oxidation product obtained by centrifugation is centrifugally washed three times with 0.1-0.5 mol / L H2SO4 solution, pure water and ethanol in sequence, with each centrifugal washing time being 10-20 minutes, the washing temperature being 20-25°C, and the washing speed being 5000-10000 rpm; the washed product is dried at 65-80°C for 6-8 hours to obtain an IrO2·SnO2 catalyst product, which is a doped catalyst and has an iridium element content of 44-66%.

2. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The pH value of the mixed solution in step (1) is adjusted to 12.2-13.2, and the pH value is kept stable in this range for 10-20 minutes, and then the solution is transferred to a high-pressure reactor.

3. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The concentration of iridium trichloride in step (1) is 2.5-4.6 g / L, and the mass ratio of iridium trichloride to tin in the tin source is 4.5-5.8:

1.

4. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The sodium hydroxide and iridium trichloride described in step (1) are analytical grade reagents.

5. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The stirring rate in step (2) is 200-400 rpm, and the solution is stirred for 60-120 min.

6. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The heating temperature in step (2) is in the range of 120 to 160° C., and the heating rate is in the range of 2 to 5° C. / min.

7. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The tin source in step (2) is at least one of stannous chloride, tin tetrachloride, and sodium stannate; 8. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The oxygen partial pressure in the reactor is controlled to be 0.5-0.7 MPa and the total pressure is controlled to be 0.7-1.3 MPa.

9. The method for preparing a tin-doped iridium dioxide anode catalyst according to claim 1, wherein: The centrifugal washing speed in step (3) is 6000-8000 rpm.

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