Preparation method and application of supported iridium-based OER catalyst

Abstract

The application relates to the technical field of catalysts, and particularly discloses a preparation method and application of a supported iridium-based OER catalyst; the supported iridium oxide catalyst is prepared by adopting an innovative double-hydrolysis synthesis method of a precursor salt, the synthesis method is simple and controllable, the reaction temperature is controlled at 60 DEG C, is much lower than 160 DEG C required by a traditional hydrothermal method and a glycol reduction method, is more energy-saving, and is favorable for obtaining ultra-small iridium oxide nanoparticles (2-3 nm) which are uniformly dispersed; the Ir loading amount on a single electrode is 0.014 mg / cm2, the problem of a large iridium usage amount in an existing preparation process is solved, and the production cost is greatly reduced; the performance is 6 times that of a commercial iridium oxide catalyst, and when the standard potential is 1.6 V, the current density can reach 75 mA cm ‑2 . By means of the innovative synthesis strategy, the usage amount of the noble metal is effectively reduced, the catalyst of the application improves the energy conversion efficiency, and has remarkable advantages in economy and sustainability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and specifically discloses a preparation method and application of a supported iridium-based OER catalyst. Background Art

[0002] In recent years, many iridium-based materials have been used in the research of PEM water electrolysis, such as IrO2 / TiO2, IrNi x , IrCo / C and IrO x / SrIrO3, etc., but some common problems were found in the research, such as (1) the currently reported Ir-based nanomaterial synthesis methods usually produce large nanoparticles, resulting in low utilization of Ir atoms; (2) a large amount of organic (polymer) molecular protective agents are often introduced during the synthesis process, which will remain on the surface of the catalyst and affect the exposure of the active sites, ultimately leading to a decrease in activity; (3) in order to increase the hydrogen / oxygen production rate, commercial water electrolysis hydrogen production electrolyzers need to operate at a high current density (> 400 mAcm -2 ), while high current density electrolysis will produce a large number of bubbles, which will occupy the active sites on the catalyst surface and / or destroy the catalyst structure, thereby reducing the catalytic activity and stability. Summary of the Invention

[0003] To address these issues, we provide a simple and efficient method for preparing nanoscale supported iridium-based catalysts under mild conditions. By adjusting the synthesis parameters, the iridium oxide nanoparticles in the prepared catalyst are made smaller (2-3nm) and more evenly dispersed, thereby preparing a low-loading, high-performance iridium-based OER catalyst that can be used in the field of water electrolysis catalysis technology.

[0004] The first aspect of the present invention provides a method for preparing a supported iridium-based OER catalyst, comprising:

[0005] S1: adding a titanium precursor salt to alcohol, heating, and dispersing to obtain a mixed solution;

[0006] S2: adding an iridium precursor to the mixture to obtain a precipitate, which is then dried;

[0007] S3: Grinding the dried solid into powder, heating to a predetermined temperature, and calcining at the predetermined temperature;

[0008] S4: The calcined solid is washed with a mixture of water and alcohol to obtain the catalyst IrO2 / TiO2-CTO.

[0009] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the titanium precursor salt in S1 is selected from one or a combination of cesium titanate, potassium titanate, and lithium titanate.

[0010] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the alcohol in S1 is selected from one or more of methanol, ethanol, or isopropanol.

[0011] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the heating temperature in S1 is heated to 50-70°C, in some embodiments, 60°C, in some embodiments, 65°C, and in some embodiments, 70°C.

[0012] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the heating temperature in S1 is heated to 50-70°C.

[0013] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the amount of the titanium precursor added per 1 L of the alcohol solution in S1 is 30-35 mmol in terms of titanium atoms.

[0014] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the heating temperature in S1 is heated to 50-70°C, in some embodiments 55°C, in some embodiments 60°C, and in some embodiments 65°C.

[0015] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the amount of the titanium precursor added per 1 L of alcohol solution in S1 is 30 to 35 mmol, calculated as titanium atoms. In some embodiments, the amount of the titanium precursor added per 1 L of alcohol solution in S1 is 32 mmol, calculated as titanium atoms. In some embodiments, the amount of the titanium precursor added per 1 L of alcohol solution in S1 is 34 mmol, calculated as titanium atoms.

[0016] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, in the step S2, the amount of the iridium precursor added per 1 L of alcohol solution is 60-70 mg, calculated as iridium atoms. In some embodiments, in the step S2, the amount of the iridium precursor added per 1 L of alcohol solution is 66 mg, calculated as iridium atoms.

[0017] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the iridium precursor in S2 is selected from one or a combination of chloroiridic acid, iridium trichloride, iridium acetate, and potassium chloroiridate.

[0018] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the iridium precursor in S2 is configured as a solution and then added to the mixed liquid.

[0019] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the iridium precursor solution is an aqueous solution of an iridium precursor.

[0020] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the S2 iridium precursor aqueous solution is prepared in such a manner that the amount of the iridium precursor fed per 1 L of water is 80 to 120 g, calculated as iridium atoms. In some embodiments, the amount of the iridium precursor fed per 1 L of water is 90 g, calculated as iridium atoms. In some embodiments, the amount of the iridium precursor fed per 1 L of water is 110 g, calculated as iridium atoms.

[0021] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the drying temperature in S3 is 50~70°C. In some embodiments, the drying temperature in S3 is 55°C. In some embodiments, the drying temperature in S3 is 60°C. In some embodiments, the drying temperature in S3 is 65°C.

[0022] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the heating rate in S4 is 4~6 °C / min, in some embodiments, the heating rate in S4 is 4 °C / min, in some embodiments, the heating rate in S4 is 5 °C / min, and in some embodiments, the heating rate in S4 is 6 °C / min.

[0023] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst of the first aspect, the predetermined temperature in S4 is 430~470°C. In some embodiments, the predetermined temperature in S4 is 450°C. In some embodiments, the predetermined temperature in S4 is 460°C. In some embodiments, the predetermined temperature in S4 is 470°C.

[0024] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the calcination is performed in an air atmosphere.

[0025] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the alcohol in S4 is methanol, ethanol or isopropanol.

[0026] In some specific embodiments of the method for preparing a supported iridium-based OER catalyst according to the first aspect, the number of washing times in S4 is 3 times.

[0027] The second aspect of the present invention provides a supported iridium-based OER catalyst IrO2 / TiO2-CTO obtained by the preparation method described in the first aspect.

[0028] The third aspect of the present invention proposes an application of the supported iridium-based OER catalyst IrO2 / TiO2-CTO described in the second aspect in hydrogen production by water electrolysis.

[0029] The drugs used in the present invention are purchased from the open legal market and have not been further purified.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] Technical means: The present invention precisely controls the ratio of precursor salt and alcohol, the type of alcohol (isopropyl alcohol), the dripping rate of the iridium precursor, and the reasonable type of titanium precursor (cesium titanate) and iridium precursor (chloroiridic acid). After experimental analysis, it was found that the strong binding ability of cesium ions and chloroiridate ions makes it easier to evenly load the acidic iridium precursor.

[0032] (1) Through the above technical means, the present invention adopts an innovative double hydrolysis synthesis method of precursor salts. The synthesis method of this method is simple and controllable, and the reaction temperature is controlled at 60 °C, which is lower than the 160 °C required by the traditional hydrothermal method and ethylene glycol reduction method, and is more energy-efficient. This low-temperature synthesis strategy not only reduces energy consumption, but also may help maintain the high specific surface area and specific microstructure of the catalyst, which is crucial for improving the activity of the catalyst. In addition, the low-temperature synthesis method also reduces safety risks and equipment loss during the experiment, reduces the requirements for equipment, and makes the experimental conditions milder, which is conducive to large-scale production and industrial application.

[0033] (2) The present invention prepares a supported iridium oxide catalyst, and the amount of iridium used is much lower than that of commercial iridium oxide catalysts. The Ir loading on a single electrode is 0.014 mg / cm², which solves the problem of large iridium usage in existing preparation processes and greatly reduces production costs. The performance is 6 times that of commercial iridium oxide catalysts. When the standard potential is 1.6 V, the current density can reach 75 mA cm -2 By reducing the use of precious metals, the catalyst of the present invention improves energy conversion efficiency and has significant advantages in terms of economy and sustainability. This is of great significance for reducing the cost of clean energy technologies such as hydrogen fuel cells and accelerating their commercialization process.

[0034] (3) The catalyst can achieve a current density of 10 mAcm under the condition of Ir loading of 0.014 mg / cm². -2When the overpotential is 280 mV, the overpotential is significantly lower than that of many traditional catalysts, indicating that the catalyst can achieve efficient electrocatalytic OER at a low loading. This low overpotential means that during the electrochemical water splitting process, the catalyst requires a smaller additional voltage to drive the reaction, thereby reducing energy consumption and improving energy conversion efficiency. In addition, the low overpotential also indicates that the catalyst has high intrinsic activity and low charge transfer resistance, which is crucial for accelerating the electron transfer process and improving reaction kinetics.

[0035] (4) The catalyst can achieve a current density of 75 mA cm at a standard potential of 1.6 V under the condition of an Ir loading of 0.014 mg / cm². -2 . This outstanding performance shows that the catalyst can still maintain a high current output at a higher potential, which is particularly important for high-efficiency electrochemical water splitting in practical applications. The realization of high current density is usually closely related to the high activity, high stability and optimized charge transfer characteristics of the catalyst. This performance advantage of the catalyst not only reflects its excellent catalytic activity at high potential, but also means that it has potential application prospects in actual electrochemical devices, especially in situations where high current output is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 shows the powder X-ray diffraction pattern of the catalyst sample IrO2 / TiO2-CTO;

[0037] Figure 2 Shows the transmission electron microscope image and field emission scanning electron microscope image of the catalyst sample IrO2 / TiO2-CTO;

[0038] Figure 3 1-3 shows a comparison of electrochemical performance tests;

[0039] Figure 4 The mass-normalized activity graphs of Examples 1-3 are shown. DETAILED DESCRIPTION

[0040] Example 1: Preparation of IrO2 / TiO2-CTO

[0041] Step 1: Disperse cesium titanate as a titanium precursor (50 mmol based on titanium atoms) in 1.5 L of isopropanol, heat in a 60 °C water bath, and stir thoroughly for 30 min.

[0042] Step 2: Add 5.4 mL of the prepared aqueous solution of iridium precursor (chloroiridic acid), i.e., 100 mg / mL chloroiridic acid aqueous solution, dropwise to the above dispersion. Continue heating in a 60°C water bath and stirring for 2 h to obtain a green precipitate.

[0043] Step 3: After washing and drying the precipitate with ethanol, transfer it to a vacuum drying oven at 60°C, allow it to dry for 12 hours, and grind it into powder to obtain the catalyst precursor;

[0044] Step 4: Control the heating rate to 5 ℃ / min, raise the temperature from room temperature to 450 ℃, calcine the catalyst precursor in an air atmosphere for 1 h, and wash it with water and ethanol several times to obtain a titanium oxide-supported iridium oxide catalyst, represented by: IrO2 / TiO2-CTO.

[0045] Comparative Example 1:

[0046] The difference between Comparative Example 1 and Example 1 is that the titanium precursor added in step 1 is changed from cesium carbonate to lithium titanate (the amount of the added material is 50 mmol in terms of titanium atoms).

[0047] Comparative Example 2:

[0048] The difference between Comparative Example 2 and Example 1 is that the titanium precursor added in step 1 is changed from cesium carbonate to potassium titanate (the amount of the added material is 50 mmol in terms of titanium atoms).

[0049] Comparative Example 3:

[0050] The difference between Comparative Example 3 and Example 1 is that the solvent isopropyl alcohol used in step 1 is replaced by ethanol.

[0051] Comparative Example 4:

[0052] The difference between Comparative Example 4 and Example 1 is that the water bath temperature used in step 2 is 30°C.

[0053] Comparative Example 5:

[0054] The difference between Comparative Example 5 and Example 1 is that the iridium precursor used in step 2 is iridium trichloride (the feed amount in terms of Ir atoms is the same as that in Example 1).

[0055] Comparative Example 6:

[0056] The difference between Comparative Example 6 and Example 1 is that the iridium precursor used in step 2 is iridium acetate (the feed amount in terms of Ir atoms is the same as that in Example 1).

[0057] Comparative Example 7:

[0058] The difference between Comparative Example 7 and Example 1 is that the iridium precursor used in step 2 is potassium chloroiridate (the feed amount in terms of Ir atoms is the same as that in Example 1).

[0059] Comparative Example 8:

[0060] The difference between Comparative Example 8 and Example 1 lies in the way in which the iridium precursor is added to the titanium precursor in step 2:

[0061] The addition method of Comparative Example 8 is:

[0062] 5.4 mL of the prepared aqueous solution of iridium precursor (chloroiridic acid), i.e., chloroiridic acid aqueous solution (100 mg / ml, Ir), was mixed with the above dispersion at once, and then continued to heat in a 60 °C water bath and stir for 2 h.

[0063] Comparative Example 9:

[0064] The difference between Comparative Example 9 and Example 1 is the difference in step 2, and the others are the same:

[0065] 8.1 mL of the prepared aqueous solution of iridium precursor (chloroiridic acid), i.e., chloroiridic acid aqueous solution (100 mg / ml, Ir), was added dropwise to the above dispersion, and the mixture was heated in a 60 °C water bath and stirred for 2 h to obtain a green precipitate.

[0066] Comparative Example 10:

[0067] The difference between Comparative Example 10 and Example 1 is the difference in step 2, and the others are the same:

[0068] 10.8 mL of the prepared aqueous solution of iridium precursor (chloroiridic acid), i.e., chloroiridic acid aqueous solution (100 mg / ml, Ir), was added dropwise to the above dispersion, and the mixture was heated in a 60 °C water bath and stirred for 2 h to obtain a green precipitate.

[0069] Summary table of catalyst preparation of Example 1 and Comparative Examples 1 to 10

[0070] Titanium precursor Step 1 Solvent Iridium precursor Step 2 Temperature (°C) Calcination atmosphere Heating rate (℃ / min) Constant temperature (℃) How to join Amount of iridium precursor solution added (ml) Example 1 Cesium titanate Isopropyl alcohol Chloroiridic acid 60 Air atmosphere 5℃ / min 450℃ Titration 5.4 Comparative Example 1 lithium titanate / / / / / / / / Comparative Example 2 Potassium titanate / / / / / / / / Comparative Example 3 / ethanol / / / / / / / Comparative Example 4 / / / 30 / / / / / Comparative Example 5 / / Iridium trichloride / / / / / / Comparative Example 6 / / Iridium acetate / / / / / / Comparative Example 7 / / Potassium chloroiridate / / / / / / Comparative Example 8 / / / / / / / Disposable / Comparative Example 9 / / / / / / / / 8.1 Comparative Example 10 / / / / / / / / 10.8

[0071] In Table 1, “ / ” represents the same as Example 1.

[0072] The “addition method” in Table 1 refers to the method of adding the iridium precursor solution to the titanium precursor isopropanol mixed solution.

[0073] Example 2: Preparation of unloaded commercial IrO2 catalyst of control sample 1

[0074] (1) Unloaded commercial IrO2 catalyst is used as anode material for hydrogen production by water electrolysis, denoted as: IrO2-Com.

[0075] Example 3: Preparation of unloaded IrO2 prepared from cesium-containing precursor of control sample 2

[0076] (1) Add 250 μL of chloroiridic acid aqueous solution (100 mg / mL Ir) dropwise into 20 mL of deionized water and stir thoroughly for 30 min.

[0077] (2) Add freshly prepared 1 M CsOH solution dropwise into the above solution and continue stirring for 30 min to obtain a red precipitate;

[0078] (3) The precipitate was washed and dried with ethanol, and then calcined at 550 °C in air atmosphere for 1 h at a heating rate of 5 °C / min. After washing with water and ethanol several times, an unloaded IrO2 catalyst prepared from a cesium-containing precursor was obtained, which was expressed as: IrO2-Cs2IrCl6.

[0079] Example 4: Characterization of IrO2 / TiO2-CTO

[0080] (1) Take about 50 mg of the catalyst sample IrO2 / TiO2-CTO for X-ray diffraction (XRD) experiment;

[0081] (2) About 1 mg of the catalyst sample IrO2 / TiO2-CTO was dispersed in an ethanol solution and subjected to ultrasonic dispersion for about 30 min. Finally, a small amount of the sample ethanol solution was taken and dropped onto the surface of a silicon wafer for field emission scanning electron microscopy (SEM) experiments.

[0082] (3) About 1 mg of the catalyst sample IrO2 / TiO2-CTO was dispersed in an ethanol solution and subjected to ultrasonic dispersion for about 30 min. Finally, a small amount of the sample ethanol solution was taken out and dropped onto the surface of the ultra-thin carbon film for transmission electron microscopy (TEM) experiments.

[0083] Example 5: Performance test of the electrolytic water anode of Examples 1-3

[0084] (1) Examples 1-3 and Comparative Examples 1-10 were tested using linear sweep voltammetry, i.e., LSV curves. Testing was performed using a Shanghai Chenhua (CHI 660E) electrochemical workstation, using a glassy carbon electrode as the working electrode, a platinum sheet as the counter electrode, and a standard hydrogen electrode as the reference electrode. The electrolyte was a 0.5 M H2SO4 solution prepared at room temperature. Three working electrodes were prepared for each sample, and each working electrode was tested three times at 25°C and 80°C to ensure the authenticity and reliability of the data.

[0085] (2) Preparation of the working electrode: Weigh 2 mg of the catalysts from Examples 1-3 and Comparative Examples 1-10 and place them in a sample bottle. Then, add 700 µL of deionized water, 290 µL of isopropanol, and 10 µL of Nafion solution. The sealed sample bottle is placed in an ultrasonic machine and thoroughly sonicated to obtain a catalyst ink. Use a pipette to draw 10 µL of the catalyst ink onto a glassy carbon electrode and dry it. Following this method, an electrode with a catalyst loading of 0.1 mg / cm² is obtained.

[0086] (3) When the current density is 10 mA / cm², the overpotential of Example 1 is 280 mV, the overpotential of Example 2 is 316 mV, and the overpotential of Example 3 is 285 mV.

[0087] Overpotential and Tafel slope test results of Examples 1 to 3 and Comparative Examples 1 to 10

[0088]

[0089] In the table, “×” represents that the comparative example has no electrochemical activity, or its electrochemical activity is far different from that of Example 1.

[0090] After the catalyst sample was calcined in air, the main crystal phases were iridium oxide and anatase titanium dioxide ( Figure 1 ).

[0091] Through transmission electron microscopy and field emission scanning electron microscopy, the loading of iridium oxide was achieved, and the size of iridium oxide particles was 2~3 nm ( Figure 2 ).

[0092] The obtained catalyst was used for oxygen evolution reaction by electrolysis of water. At a current density of 10 mA / cm², the overpotential of Example 1 was 280 mV, the overpotential of Example 2 was 316 mV, and the overpotential of Example 3 was 285 mV ( Figure 3 ).

[0093] The obtained catalyst was used for oxygen evolution reaction by electrolysis of water. After mass normalization, the performance of Example 1 was significantly better than that of Examples 2 and 3 ( Figure 4 ).

[0094] The above description is only a preferred embodiment of the present invention and cannot be understood as limiting the present application. All equivalent changes and modifications made within the scope of the patent application of the present invention should fall within the scope of the present invention. The present invention is further described below with reference to the drawings and specific embodiments.

Claims

1. A method for preparing a supported iridium-based OER catalyst, comprising: S1: adding a titanium precursor salt to isopropanol, heating, and dispersing to obtain a mixed solution; S2: An aqueous solution of an iridium precursor is added dropwise to the mixture, and the mixture is heated to 60°C in a water bath to obtain a precipitate; S3: The precipitate is washed with alcohol, dried, and the dried solid is ground into powder; S4: heating the powder to a predetermined temperature, calcining the powder at the predetermined temperature, and washing the calcined solid with a mixture of water and alcohol to obtain the catalyst IrO2 / TiO2-CTO; The amount of the titanium precursor added to 1 L of isopropanol in S1 is 30-35 mmol in terms of titanium atoms; The S2 iridium precursor aqueous solution is prepared by feeding 80 to 120 g of the iridium precursor per 1 L of water, calculated as iridium atoms; The titanium precursor salt is selected from cesium titanate, and the iridium precursor is selected from chloroiridic acid.

2. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The heating temperature in S1 is heated to 50-70°C.

3. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The drying temperature in S3 is 50-70°C.

4. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The heating rate in S4 is 4-6°C / min.

5. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The predetermined temperature in S4 is 430-470°C.

6. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The calcination is carried out in an air atmosphere.

7. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The alcohol in S4 is ethanol.

8. The method for preparing a supported iridium-based OER catalyst according to claim 1, wherein: The number of washes was 3 times.

9. A supported iridium-based OER catalyst IrO2 / TiO2-CTO obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the supported iridium-based OER catalyst IrO2 / TiO2-CTO according to claim 9 in hydrogen production by water electrolysis.

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