Boron-modified iridium black, preparation method thereof and water electrolysis catalyst
By modifying the iridium black catalyst by boron, the problems of insufficient catalytic activity and poor stability of the existing iridium black catalyst are solved, efficient and stable acidic oxygen evolution catalytic performance is achieved, and the preparation process is simplified and environmental pollution is reduced.
Patent Information
- Application Number
- CN202311631132.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-30
- Publication Date
- 2025-05-30
AI Technical Summary
The existing iridium black catalysts have insufficient catalytic activity and poor stability in proton exchange membrane electrolysis technology, complex synthesis process and poor consistency, resulting in difficulty in scale preparation and serious environmental pollution.
Iridium black is modified by boron, and boron elements are doped to improve catalytic activity and stability. A simple preparation method is adopted, including evaporating, washing and drying a mixture of boron source, iridium source and organic alcohol to prepare a boron modified iridium black catalyst with a particle size of 2nm-5nm.
The high catalytic activity and stability of boron-modified iridium black catalyst was achieved, especially in the acidic oxygen evolution reaction, and stable catalyzed at a current density of 10 mA/cm2 for more than 160 hours, reducing environmental pollution and improving preparation consistency.
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Figure CN120060904A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of inorganic functional materials, and particularly to a boron-modified iridium black, a preparation method thereof, and an electrolytic water catalyst. Background Art
[0002] In current hydrogen production technologies, proton exchange membrane (PEM) electrolytic water hydrogen production technology has the advantage of rapid start-up and shutdown, and can match the volatility and instability of renewable energy power generation systems such as solar energy and wind energy. It is considered the most promising hydrogen production technology.
[0003] The oxygen evolution reaction is the bottleneck reaction in the water splitting process, which largely determines the energy consumption, power, and lifespan of the electrolytic cell, etc. Currently, the water splitting oxygen evolution catalyst used in commercial proton exchange membrane electrolytic water technology is an iridium-based catalyst. Iridium resources are extremely scarce and expensive. Therefore, the urgent task is to develop an efficient and stable iridium-based catalyst to make it exhibit more excellent performance and more lasting stability in the same operating environment. At present, although iridium black catalyst is widely used in proton exchange membrane electrolytic water technology, its catalytic activity is poor and its stability needs to be further improved. More importantly, its synthesis process is often complex and cumbersome, and the products prepared in batches have poor consistency.
[0004] Existing hydrogen evolution catalysts have the following problems: 1. The synthesis time is too long, and the synthesis method is cumbersome, time-consuming, and energy-consuming; 2. The stability of the catalyst is not good and needs to be further improved. In particular, existing iridium black preparation technologies often have drawbacks such as cumbersome processes, difficulty in scaling up, and serious environmental pollution, and the prepared products also have problems such as poor homogeneity and poor catalytic performance.
[0005] Therefore, a catalyst synthesis method that is simple in process and can improve the stability of the product is needed. Summary of the Invention
[0006] In order to solve the above problems, the purpose of the present invention is to provide a boron-modified iridium black, a preparation method thereof, and an electrolytic water catalyst. The boron-modified iridium black has high catalytic activity, electrical conductivity, and corrosion resistance.
[0007] To achieve the above purpose, the present invention provides a boron-modified iridium black, which includes: elemental iridium black and boron doped in the iridium black; taking the molar amount of the boron-modified iridium black as 100%, the molar amount of boron element in the boron-modified iridium black is 0.5%-5%.
[0008] In the above-mentioned boron-modified iridium black, the molar content of boron element in the boron-modified iridium black is 0.5%-5%, specifically, it can be specific values such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., and ranges with any two of the above specific values as endpoints. In some specific embodiments, the molar amount of boron element in the boron-modified iridium black can be controlled to be 1%-3%.
[0009] The existing iridium catalysts have relatively large particle sizes, all above hundreds of nanometers. The particle size of the above-mentioned boron-modified iridium black provided by the present invention is relatively small, being 2nm-5nm, for example, specific values such as 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, etc., and ranges with any two of the above specific values as endpoints. The boron-modified iridium black with the above particle size range has a small particle size. Combining the modification effect of boron on elemental iridium, it can endow the material with higher conductivity and corrosion resistance, making the boron-modified iridium black have higher acidic oxygen evolution catalytic activity and better catalytic stability as a catalyst.
[0010] The present invention also provides a preparation method of the above-mentioned boron-modified iridium black, and this preparation method includes:
[0011] Mix a mixture of a boron source, an iridium source and an organic alcohol to form a reaction system, evaporate the reaction system to dryness (that is, evaporate to dryness, and the liquid completely volatilizes), wash and dry to obtain the boron-modified iridium black.
[0012] In the above preparation method, the molar ratio of the boron source to the iridium source is 1:0.5-10, for example, 1:0.5-5.5 or 1:5-10, etc. The molar ratio of the boron source to the iridium source can specifically be specific values such as 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc., and ranges with any two of the above specific values as endpoints.
[0013] In the above preparation method, the molar ratio of the sum of the boron source and the iridium source to the organic alcohol is 1:230-800, for example, 1:230-1:500-800.
[0014] In the above preparation method, on the one hand, the organic alcohol can be used as a solvent to dissolve the iridium source; on the other hand, the organic alcohol can be used as a reducing agent and a stabilizer, promoting the reduction of the boron source and the iridium source, and controlling the growth rate of the nanoparticles, preventing the aggregation of the particles, improving the dispersibility of the particles, and being beneficial to obtaining boron-modified iridium black with a small particle size and a high degree of dispersion. Conversely, if the reaction system does not contain organic alcohol, the reduction reaction rate is slower, and the particle size of the obtained boron-modified iridium black nanoparticles is larger. The organic alcohol can include one or a combination of two or more of ethylene glycol, isopropyl alcohol, and glycerol.
[0015] In the above preparation method, the boron source is used to provide the doping element boron. The boron source is generally a boron-containing mixture soluble in water or organic alcohol. The boron source includes one or a combination of two or more of boric acid, sodium borohydride, and sodium metaborate.
[0016] In the above preparation method, the boron source can be added in the form of a solution, and the solvent of the boron source solution can be water. The aqueous phase system can fully dissolve the boron source and uniformly disperse it in the synthesized boron-modified iridium black. There is no special limitation on the amount of water in the present invention, as long as the boron source can be fully dissolved. In some specific embodiments, the amount of water can be 10 mL.
[0017] In the above preparation method, the iridium source is generally a iridium-containing mixture soluble in water or organic alcohol. Specifically, the iridium source can include one or a combination of two or more of iridium chloride, chloroiridic acid, potassium hexachloroiridate, and iridium acetylacetonate.
[0018] In the above preparation method, the evaporation temperature is 80 - 180 °C, such as specific values like 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, etc., and ranges with any two of the above specific values as endpoints. There is no special limitation on the evaporation time in the present invention, as long as the liquid in the reaction system is evaporated to dryness.
[0019] In the above preparation process, by using organic alcohol and controlling the evaporation conditions, the present invention can control the reduction process of iridium at the atomic level and achieve the maximum utilization of the solvent.
[0020] In some specific embodiments, the evaporation can be carried out in an oil bath environment and / or an oven. When the evaporation is carried out in an oil bath environment, the evaporation temperature can be further controlled to 80 - 150 °C; when the evaporation is carried out in an oven, the evaporation temperature can be further controlled to 120 - 180 °C.
[0021] In the above preparation method, the washing is usually water washing. In some specific embodiments, the number of washing times can be 3 times.
[0022] In the drying process after washing in the above preparation method, the drying temperature can be controlled to 50 - 80 °C.
[0023] According to the specific embodiments of the present invention, the preparation method of the above boron-modified iridium black includes:
[0024] Dissolve the boron source in water to obtain an aqueous boron source solution; dissolve the iridium source in organic alcohol to obtain an iridium source alcohol solution; mix the aqueous boron source solution and the iridium source alcohol solution, evaporate to dryness at 80 - 180 °C, wash with water, and dry at 50 - 80 °C to obtain boron-modified iridium black; wherein, the molar ratio of the boron source to the iridium source is 1:5 - 10, and the molar ratio of the sum of the boron source and the iridium source to the organic alcohol is 1:500 - 800.
[0025] The above preparation method provided by the present invention can macroscopically prepare kilogram-level boron-modified iridium black catalysts under mild conditions such as normal pressure (101.325 kPa) and relatively low temperature (300 - 350 °C). Further, by regulating the input amounts of the reactant raw materials, the boron source and the iridium source, the preparation method provided by the present invention can synthesize a series of boron-modified iridium black catalysts with different boron contents, enabling precise regulation of the catalyst components.
[0026] The present invention also provides an electrolytic water catalyst, which comprises the above boron-modified iridium black or is made of the above boron-modified iridium black. The boron-modified iridium black provided by the present invention has a small particle size and contains the doped element boron, and has excellent acidic oxygen evolution catalytic activity and high stability. In some specific embodiments, when the above boron-modified iridium black is used as a catalyst in the electrolytic water process, it can stably catalyze for more than 160 h at a current density of 10 mA / cm 2 .
[0027] The beneficial effects of the present invention include:
[0028] 1. The boron-modified iridium black catalyst provided by the present invention has a nanoscale size. The modification of boron endows the catalyst with higher conductivity and corrosion resistance, making the catalyst exhibit excellent catalytic activity (especially acidic oxygen evolution catalytic activity) and relatively high catalytic stability (especially for strong acidic and strong oxidizing environments). The proton exchange membrane electrolytic cell with the boron-modified iridium black catalyst of the present invention as the anode also shows outstanding advantages in terms of performance and service life, and has broad development prospects.
[0029] 2. The boron-modified iridium black catalyst provided by the present invention has excellent conductivity and corrosion resistance, shows lower contact resistance and antioxidant properties in the proton exchange membrane pure water electrolytic cell, making the electrolytic cell have outstanding performance and service life, and has broad development prospects.
[0030] 3. The preparation method provided by the present invention can precisely regulate the boron modification amount in the iridium black catalyst. The process is simple, has good reproducibility, mild preparation conditions, can realize batch preparation, and reduces environmental pollution in the traditional preparation process. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1XRD pattern of the boron-modified iridium black catalyst synthesized in Example 1. The samples corresponding to Figures a, b, c, and d are boron-modified iridium black catalyst samples 1a, 1b, 1c, and 1d, respectively.
[0032] Figure 2 SEM image of the boron-modified iridium black catalyst synthesized in Example 1. The samples corresponding to Figures a, b, c, and d are boron-modified iridium black catalyst samples 1a, 1b, 1c, and 1d, respectively.
[0033] Figure 3 TEM image of boron-modified iridium black catalyst sample 1c synthesized in Example 1.
[0034] Figure 4 Electrolytic water oxygen evolution polarization curves of the boron-modified iridium black catalyst synthesized in Example 1. The samples corresponding to Figures a, b, c, and d are boron-modified iridium black catalyst samples 1a, 1b, 1c, and 1d, respectively.
[0035] Figure 5 Overpotential test results of iridium black and the boron-modified iridium black catalyst (B molar content 3%, sample 1c) synthesized in Example 1.
[0036] Figure 6 Electrolytic water oxygen evolution polarization curve of iridium boride catalyst.
[0037] Figure 7 Polarization curve of the proton exchange membrane electrolyzer made of boron-modified iridium black catalyst sample 1c synthesized in Example 1.
[0038] Figure 8 Electrolytic water oxygen evolution polarization curve of the boron-modified iridium black catalyst (B molar content 3%, sample 1c) synthesized in Example 1. Detailed implementation mode
[0039] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.
[0040] The sources of the raw materials used in the following experiments are shown in Table 1, and the equipment information is shown in Table 2:
[0041] Table 1
[0042] Raw material name Specification Manufacturer Sodium borohydride 50g Sinopharm Chemical Reagent Co., Ltd. Iridium trichloride 10.01g Sinopharm Chemical Reagent Co., Ltd. Ethylene glycol 500ml Sinopharm Chemical Reagent Co., Ltd. Isopropyl alcohol 500ml Sinopharm Chemical Reagent Co., Ltd. Glycerol 500ml Sinopharm Chemical Reagent Co., Ltd. Chloroiridic acid 10g Shanghai Jiufeng Chemical Co., Ltd. Potassium hexachloroiridate 1g Anaiji Iridium acetylacetonate 1g Aladdin Boric acid 500g Beijing Chemical Plant Sodium metaborate 500g Aladdin Iridium Black Model SSC-Ir-4001 Anhui Masuzu New Energy Technology Co., Ltd.
[0043] Table 2
[0044] equipment Manufacturer Energy-saving fiber resistance furnace Hangzhou Zhuochi Instrument Co., Ltd. Ultrasonic cleaning machine Ningbo Xinzhi Biotechnology Co., Ltd. Electric constant temperature blast drying oven Shanghai Senxin Experimental Instrument Co., Ltd. Ultrasonic precision spraying machine Beijing Dongfang Jinrong Ultrasonic Appliance Co., Ltd. High-speed desktop refrigerated centrifuge Shanghai Luxiangyi Centrifuge Instrument Co., Ltd.
[0045] Example 1
[0046] This embodiment provides a boron-modified iridium black catalyst, and the preparation methods of each catalyst are as follows:
[0047] Boron-modified iridium black catalyst sample 1a (mole fraction B - 0.5%):
[0048] Put 19 mg (0.49 mmol) of sodium borohydride into 10 mL of distilled water, stir well until it becomes a clear, colorless and transparent solution, and call it solution a; put 800 mg (2.68 mmol) of iridium trichloride into 100 mL of ethylene glycol, stir well until it becomes a brownish-yellow transparent solution, and call it solution b. Transfer solution a to solution b, place it in an oil bath at 120 °C. At this time, the solution shows a yellowish-green color. Heat and stir for more than 6 h to ensure that the solution is evaporated to dryness. Subsequently, wash the dried product three times with water, dry it at a temperature of 50 - 80 °C. After naturally cooling to room temperature, grind the product thoroughly to present a black powder. Collect the sample powder, which is the boron-modified iridium black catalyst (B - 0.5%), denoted as sample 1a. The mass of the product is 0.5 g.
[0049] Boron-modified iridium black catalyst sample 1b (mole fraction B - 1%):
[0050] Put 38 mg (0.98 mmol) of sodium borohydride into 10 mL of distilled water, stir well until it becomes a clear, colorless and transparent solution, and call it solution a; put 800 mg (2.68 mmol) of iridium trichloride into 100 mL of ethylene glycol, stir well until it becomes a brownish-yellow transparent solution, and call it solution b. Transfer solution a to solution b, place it in an oil bath at 120 °C. At this time, the solution shows a yellowish-green color. Heat and stir for more than 6 h to ensure that the solution is evaporated to dryness. Subsequently, wash the dried product three times with water, dry it at a temperature of 50 - 80 °C. After naturally cooling to room temperature, grind the product thoroughly to present a black powder. Collect the sample powder, which is the boron-modified iridium black catalyst (B - 1%), denoted as sample 1b. The mass of the product is 0.5 g.
[0051] Boron-modified iridium black catalyst sample 1c (mole fraction B - 3%):
[0052] 114 mg (1.47 mmol) of sodium borohydride was placed into 10 mL of distilled water and stirred thoroughly until a clear, colorless, and transparent solution was obtained, designated as solution a; 800 mg (2.68 mmol) of iridium(III) chloride was placed into 100 mL of ethylene glycol and stirred thoroughly until a brownish-yellow transparent solution was obtained, designated as solution b. Solution a was transferred into solution b and placed in an oil bath at 120 °C. At this time, the solution showed a yellowish-green color. It was heated and stirred for more than 6 h to ensure that the solution was completely evaporated. Subsequently, the dried product was washed three times with water and dried at a temperature of 50 - 80 °C. After naturally cooling to room temperature, the product was ground thoroughly to present a black powder. The sample powder was collected, which was the boron-modified iridium black catalyst (B-3%), denoted as sample 1c. The mass of the product was 0.5 g.
[0053] Boron-modified iridium black catalyst sample 1d (mole fraction B-5%):
[0054] 190 mg (4.9 mmol) of sodium borohydride was placed into 10 mL of distilled water and stirred thoroughly until a clear, colorless, and transparent solution was obtained, designated as solution a; 800 mg (2.68 mmol) of iridium(III) chloride was placed into 100 mL of ethylene glycol and stirred thoroughly until a brownish-yellow transparent solution was obtained, designated as solution b. Solution a was transferred into solution b and placed in an oil bath at 120 °C. At this time, the solution showed a yellowish-green color. It was heated and stirred for more than 6 h to ensure that the solution was completely evaporated. Subsequently, the dried product was washed three times with water and dried at a temperature of 50 - 80 °C. After naturally cooling to room temperature, the product was ground thoroughly to present a black powder. The sample powder was collected, which was the boron-modified iridium black catalyst (B-5%), denoted as sample 1d. The mass of the product was 0.5 g.
[0055] Example 2
[0056] This example provides boron-modified iridium black catalysts, and the preparation methods of each catalyst are as follows:
[0057] Sample 2a: The preparation method was similar to that of sample 1a in Example 1, with the difference that: in this experiment, isopropanol was used to replace ethylene glycol in Example 1, and the addition amount of isopropanol was calculated according to the following molar ratio: (boron source + iridium source) : isopropanol = 1:650. The other raw material compositions and preparation steps in this experiment were the same as those of sample 1a. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 0.5%.
[0058] Sample 2b: The preparation method was similar to that of sample 1b in Example 1, with the difference that: in this experiment, isopropanol was used to replace ethylene glycol in Example 1, and the addition amount of isopropanol was calculated according to the following molar ratio: (boron source + iridium source) : isopropanol = 1:650. The other raw material compositions and preparation steps in this experiment were the same as those of sample 1b. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 1%.
[0059] Sample 2c: The preparation method was similar to that of Sample 1c in Example 1, except that: in this experiment, isopropanol was used to replace ethylene glycol in Example 1, and the addition amount of isopropanol was calculated according to the following molar ratio: (boron source + iridium source): isopropanol = 1:650. The other raw material compositions and preparation steps in this experiment were the same as those of Sample 1c. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 3%.
[0060] Sample 2d: The preparation method was similar to that of Sample 1d in Example 1, except that: in this experiment, isopropanol was used to replace ethylene glycol in Example 1, and the addition amount of isopropanol was calculated according to the following molar ratio: (boron source + iridium source): isopropanol = 1:650. The other raw material compositions and preparation steps in this experiment were the same as those of Sample 1d. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 5%.
[0061] Example 3
[0062] This example provides a boron-modified iridium black catalyst, and the preparation methods of each catalyst are as follows:
[0063] Sample 3a: The preparation method was similar to that of Sample 1a in Example 1, except that: in this experiment, glycerol was used to replace ethylene glycol in Example 1, and the addition amount of glycerol was calculated according to the following molar ratio: (boron source + iridium source): glycerol = 1:720. The other raw material compositions and preparation steps in this experiment were the same as those of Sample 1a. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 0.5%.
[0064] Sample 3b: The preparation method was similar to that of Sample 1b in Example 1, except that: in this experiment, glycerol was used to replace ethylene glycol in Example 1, and the addition amount of glycerol was calculated according to the following molar ratio: (boron source + iridium source): glycerol = 1:720. The other raw material compositions and preparation steps in this experiment were the same as those of Sample 1b. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 1%.
[0065] Sample 3c: The preparation method was similar to that of Sample 1c in Example 1, except that: in this experiment, glycerol was used to replace ethylene glycol in Example 1, and the addition amount of glycerol was calculated according to the following molar ratio: (boron source + iridium source): glycerol = 1:720. The other raw material compositions and preparation steps in this experiment were the same as those of Sample 1c. After characterization, the obtained product was boron-modified iridium black, and the molar content of boron in the product was 3%.
[0066] Sample 3d: The preparation method is similar to that of Sample 1d in Example 1, with the difference that: in this experiment, glycerol is used to replace ethylene glycol in Example 1, and the addition amount of glycerol is calculated according to the following molar ratio: (boron source + iridium source): glycerol = 1:720. The other raw material compositions and preparation steps in this experiment are the same as those of Sample 1d. After characterization, the obtained product is boron-modified iridium black, and the molar content of boron in the product is 5%.
[0067] Example 4
[0068] Sample 4a: The preparation method is similar to that of Sample 1a in Example 1, with the difference that: in this experiment, the addition amount of ethylene glycol is calculated according to the following molar ratio: (boron source + iridium source): ethylene glycol = 1:780. The other raw material compositions and preparation steps in this experiment are the same as those of Sample 1a. After characterization, the obtained product is boron-modified iridium black, and the molar content of boron in the product is 0.5%.
[0069] Sample 4b: The preparation method is similar to that of Sample 1b in Example 1, with the difference that: in this experiment, the addition amount of ethylene glycol is calculated according to the following molar ratio: (boron source + iridium source): ethylene glycol = 1:780. The other raw material compositions and preparation steps in this experiment are the same as those of Sample 1b. After characterization, the obtained product is boron-modified iridium black, and the molar content of boron in the product is 1%.
[0070] Sample 4c: The preparation method is similar to that of Sample 1c in Example 1, with the difference that: in this experiment, the addition amount of ethylene glycol is calculated according to the following molar ratio: (boron source + iridium source): ethylene glycol = 1:780. The other raw material compositions and preparation steps in this experiment are the same as those of Sample 1c. After characterization, the obtained product is boron-modified iridium black, and the molar content of boron in the product is 3%.
[0071] Sample 4d: The preparation method is similar to that of Sample 1d in Example 1, with the difference that: in this experiment, the addition amount of ethylene glycol is calculated according to the following molar ratio: (boron source + iridium source): ethylene glycol = 1:780. The other raw material compositions and preparation steps in this experiment are the same as those of Sample 1d. After characterization, the obtained product is boron-modified iridium black, and the molar content of boron in the product is 5%.
[0072] Comparative Example 1
[0073] This comparative example provides an iridium black catalyst, and the iridium black is a product of model SSC-Ir-4001 of Anhui Shengshui New Energy Technology Co., Ltd.
[0074] Comparative Example 2
[0075] This comparative example provides a boronized iridium catalyst, and the preparation method of boronized iridium is as follows:
[0076] MgB and IrCl 3The powders were mixed in a molar ratio of 1:1 and ground thoroughly. After grinding, the powders were calcined at 850 °C for 4 hours under vacuum conditions with a heating rate of 3 °C / min. The calcined product was soaked in 0.5 M H 2 SO 4 solution for 5 h to remove impurities, and then washed three times with water to obtain IrB.
[0077] Test Example 1
[0078] This test example provides the results of structural characterization and performance testing of various samples in Example 1.
[0079] The above 4 samples were tested by ICP (Inductively Coupled Plasma Emission Spectrometer), and the test results are shown in Table 3.
[0080] Table 3
[0081] Test value B mole fraction Boron modified iridium black (B-0.5%) Ir 178.02ppm B 0.05ppm 0.5％ Boron modified iridium black (B-1%) Ir 131.56ppm B 0.07ppm 1％ Boron modified iridium black (B-3%) Ir 155.23ppm B 0.26ppm 3％ Boron modified iridium black (B-5%) Ir 167.17ppm B 0.47ppm 5％
[0082] The samples in Example 1 were characterized by XRD, and the results are as Figure 1 shown. It can be seen that each sample has the characteristic peaks of elemental iridium, which is the pure phase of elemental iridium metal. Further, the XRD diffraction results of Sample 1c were compared with the standard PDF card of elemental iridium and the standard PDF card of iridium boride respectively. The XRD results of Sample 1c are consistent with the characteristic peaks of elemental iridium and do not correspond to the characteristic peaks of iridium boride. Thus, it can be proved that the samples synthesized in Example 1 are not iridium boride but elemental iridium. Combining with the ICP results in Table 3, it can be known that the samples synthesized in Example 1 are elemental iridium black modified by boron doping, and boron occupies some sites of iridium metal in this product, and boron exists in the form of doping.
[0083] The samples in Example 1 were characterized by morphology, and the results are as Figure 2 、 Figure 3 shown. It can be seen that the particle size of the samples synthesized in Example 1 is 2 nm - 5 nm. The samples in Examples 2 to 4 were characterized by morphology, and the measured particle size of each sample is also 2 nm - 5 nm.
[0084] The oxygen evolution performance of the samples in Example 1 was evaluated in a standard three-electrode electrolytic cell under acidic conditions (0.5 M H 2 SO 4 ). The specific method is as follows:
[0085] The sample to be tested was uniformly dispersed in an ionomer solution with a solid content of 5% - 30%, and dropped and coated on a glassy carbon electrode drop by drop. After drying, it was used as the working electrode, and the sample loading on the working electrode was 0.28 mg / cm 2 ; a platinum wire was used as the counter electrode, a saturated calomel electrode was used as the reference electrode, and the electrolyte was 0.5 M H 2 SO 4It should be noted that all the potentials obtained with a saturated calomel electrode as the reference electrode in the electrocatalytic tests are converted to the reversible hydrogen electrode potential in the property diagram, and the external power supply is the main battery of the electrochemical workstation. Figure 4 It is the oxygen evolution reaction (OER) polarization curve obtained from the test.
[0086] In Figure 4 , in Figure a of the OER polarization curve of the boron-modified iridium black catalyst (B-0.5%, sample 1a), it shows that when the overpotential is 287 mV, the oxygen evolution current density can reach 10 mA / cm 2 ; in Figure b of the OER polarization curve of the boron-modified iridium black catalyst (B-1%, sample 1b), it shows that when the overpotential is 283 mV, the oxygen evolution current density can reach 10 mA / cm 2 ; in Figure c of the OER polarization curve of the boron-modified iridium black catalyst (B-3%, sample 1c), it shows that when the overpotential is 281 mV, the oxygen evolution current density can reach 10 mA / cm 2 ; in Figure d of the OER polarization curve of the boron-modified iridium black catalyst (B-5%, sample 1d), it shows that when the overpotential is 289 mV, the oxygen evolution current density can reach 10 mA / cm 2 . It can be seen that all the above four kinds of boron-modified iridium black catalysts have good acidic oxygen evolution catalytic activity, and among them, the iridium black catalyst with a boron modification content of 3% (sample 1c) has the best oxygen evolution performance.
[0087] According to the Figure 4 method, the OER polarization curves of iridium black and iridium boride were tested, and the results are as shown in Figure 5 , Figure 6 .
[0088] By comparing Figure 4 , Figure 5 , Figure 6 , it can be seen that for the elemental iridium black in Comparative Example 1 as the catalyst, when reaching a current density of 10 mA / cm 2 , the overpotential is 310 mV; for iridium boride in Comparative Example 2 as the catalyst, when reaching a current density of 10 mA / cm 2 , the overpotential is 429 mV; while for the boron-modified iridium provided by the present invention as the catalyst, when reaching a current density of 10 mA / cm 2 , the overpotential is only below 290 mV. This result shows that: compared with elemental iridium black and iridium boride, the boron-modified iridium black provided by the present invention has better acidic oxygen evolution catalytic activity as an electrolytic water catalyst.
[0089] Using the boron-modified iridium black catalyst (B-3%, sample 1c) of Example 1 as the anode catalytic material to assemble a proton exchange membrane electrolytic cell, its catalytic performance was evaluated. The specific method is as follows:
[0090] Add 20 mL of isopropanol and 5 mL of an ionomer solution with a solid content of 5% - 10% to 10 mg of boron-modified iridium black catalyst (B-3%). Ultrasonically disperse for 30 min to make it evenly dispersed, and spray the evenly dispersed slurry on one side of the proton exchange membrane as the anode end. Add 20 mL of isopropanol and 5 mL of an ionomer solution with a solid content of 5% - 10% to 3 mg of platinum-carbon catalyst. Ultrasonically disperse for 30 min to make it evenly dispersed, and spray the evenly dispersed slurry on the other side of the proton exchange membrane as the cathode end. Test the polarization curve of the assembled proton exchange membrane electrolyzer at 80 °C through a water electrolysis test workstation.
[0091] Figure 7 Figure 4 is the polarization curve of Sample 1c as the anode catalyst in the proton exchange membrane electrolyzer. The results show that the performance of this electrolyzer can reach 2 V @ 3.31 A / cm 2 @ 80 °C.
[0092] Test the catalytic stability of the boron-modified iridium black catalyst (B-3%). The test method is chronopotentiometry. The results are as Figure 8 shown. It can be seen that the boron-modified iridium black catalyst synthesized in the present invention can stably catalyze for 200 h at a current density of 10 mA / cm 2 , proving that the above catalyst has high catalytic stability.
[0093] Perform oxygen evolution performance tests on each sample from Example 2 to Example 4. The test method is the same as Figure 4 , and the test results are as follows:
[0094] In Example 2, for the boron-modified iridium black catalyst (mole fraction B-0.5%, Sample 2a), when the current density can reach 10 mA / cm 2 , the overpotential is 289 mV; for the boron-modified iridium black catalyst (mole fraction B-1%, Sample 2b), when the current density can reach 10 mA / cm 2 , the overpotential is 286 mV; for the boron-modified iridium black catalyst (mole fraction B-3%, Sample 2c), when the current density can reach 10 mA / cm 2 , the overpotential is 285 mV; for the boron-modified iridium black catalyst (mole fraction B-5%, Sample 2d), when the current density can reach 10 mA / cm 2 , the overpotential is 289 mV.
[0095] In Example 3, for the boron-modified iridium black catalyst (mole fraction B-0.5%, Sample 3a), when the current density can reach 10 mA / cm 2 , the overpotential is 290 mV; for the boron-modified iridium black catalyst (mole fraction B-1%, Sample 3b), when the current density can reach 10 mA / cm 2At this time, the overpotential is 287 mV; for the boron-modified iridium black catalyst (B molar fraction - 3%, sample 3c), when the current density can reach 10 mA / cm 2 At this time, the overpotential is 286 mV; for the boron-modified iridium black catalyst (B molar fraction - 5%, sample 3d), when the current density can reach 10 mA / cm 2 At this time, the overpotential is 288 mV.
[0096] In Example 4, for the boron-modified iridium black catalyst (B molar fraction - 0.5%, sample 4a), when the current density can reach 10 mA / cm 2 At this time, the overpotential is 288 mV; for the boron-modified iridium black catalyst (B molar fraction - 1%, sample 4b), when the current density can reach 10 mA / cm 2 At this time, the overpotential is 285 mV; for the boron-modified iridium black catalyst (B molar fraction - 3%, sample 4c), when the current density can reach 10 mA / cm 2 At this time, the overpotential is 282 mV; for the boron-modified iridium black catalyst (B molar fraction - 5%, sample 4d), when the current density can reach 10 mA / cm 2 At this time, the overpotential is 286 mV.
[0097] The electrocatalytic performance of the catalyst samples in Examples 2 to 4 was tested. The test method was the same as Figure 8 , and the test results are as follows:
[0098] The performance of the proton exchange membrane electrolyzer assembled with the sample 2c obtained in Example 2 as the anode catalyst can reach 2 V @ 3.52 A / cm 2 @ 80 °C.
[0099] The performance of the proton exchange membrane electrolyzer assembled with the sample 3c obtained in Example 3 as the anode catalyst can reach 2 V @ 3.47 A / cm 2 @ 80 °C.
[0100] The performance of the proton exchange membrane electrolyzer assembled with the sample 4c obtained in Example 4 as the anode catalyst can reach 2 V @ 3.35 A / cm 2 @ 80 °C.
[0101] From the above results, it can be seen that the boron-modified iridium black synthesized in the present invention has a small particle size, is doped with boron elements, has excellent acidic oxygen evolution catalytic activity, and high stability. The synthesis method of this boron-modified iridium black has mild conditions, can be prepared in large quantities, and can accurately control the product components.
Claims
1. A boron-modified iridium black, which comprises iridium black and boron doped in the iridium black; based on the molar amount of the boron-modified iridium black being 100%, the molar amount of boron element in the boron-modified iridium black is 0.5%-5%.
2. The boron-modified iridium black according to claim 1, wherein, the particle size of the boron-modified iridium black is 2 nm - 5 nm.
3. The preparation method of the boron-modified iridium black according to claim 1 or 2, and this preparation method comprises: Mixing a mixture of a boron source, an iridium source and an organic alcohol to form a reaction system, evaporating and drying the reaction system, washing and drying to obtain the boron-modified iridium black.
4. The preparation method according to claim 3, wherein, the molar ratio of the boron source to the iridium source is 1:0.5 - 10.
5. The preparation method according to claim 3, wherein, the molar ratio of the sum of the boron source and the iridium source to the organic alcohol is 1:230 - 800.
6. The preparation method according to claim 3, wherein, the organic alcohol includes one or a combination of two or more of ethylene glycol, isopropyl alcohol, and glycerol.
7. The preparation method according to claim 3, wherein, the boron source includes one or a combination of two or more of boric acid, sodium borohydride, and sodium metaborate.
8. The preparation method according to claim 3, wherein, the iridium source includes one or a combination of two or more of iridium chloride, chloroiridic acid, potassium hexachloroiridate, and iridium acetylacetonate.
9. The preparation method according to claim 3, wherein, the evaporation temperature is 80 - 180 °C.
10. An electrolytic water catalyst, which comprises the boron-modified iridium black according to claim 1 or 2 or is made of the boron-modified iridium black according to claim 1 or 2.