An ir@irox core-shell catalyst, and a preparation method and application thereof

Abstract

The application provides an Ir@IrOx core-shell catalyst and a preparation method and application thereof. In the XRD spectrum of the catalyst, characteristic peaks of elemental iridium and characteristic peaks of amorphous IrOx are present; in the XPS spectrum, characteristic peaks of Ir(IV) and characteristic peaks of Ir(III) are present. The preparation process of the catalyst is characterized in that: a simple organic polyacid is used to complex with chloroiridate, and the metal precursor after the complexing is calcined under nitrogen and oxygen atmospheres. When the catalyst is used as an anode catalyst for hydrogen production by water electrolysis of a proton exchange membrane, compared with commercial iridium black and iridium oxide catalysts, the catalyst has the characteristics of low overpotential and good stability.

Description

Technical Field

[0001] This invention relates to an Ir@IrOx core-shell catalyst, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane (PEM) water electrolysis for hydrogen production offers advantages over alkaline water electrolysis, including faster response, greater load adjustability, higher current density, and higher efficiency. It has experienced rapid development in recent years, particularly in the application of renewable energy power generation followed by water electrolysis. This technology is widely recognized in the hydrogen energy field as the primary method for future hydrogen production and is of great significance to the development of hydrogen energy. The anode catalyst is one of the key materials in PEM water electrolysis for hydrogen production. Its main function is to oxidize water molecules to produce oxygen and hydrogen protons under electrochemical action; this reaction is the rate-determining step in water electrolysis for hydrogen production. Typically, the anode overpotential is much higher than the cathode overpotential, which is one of the main factors determining the efficiency of water electrolysis for hydrogen production.

[0003] Commonly used oxygen evolution catalysts include iridium black and iridium dioxide. However, metallic iridium is scarce and expensive, and the catalytic activity and stability of existing catalysts are not ideal. The Ir concentration in electrolyzers is generally higher than 2 mg / cm³. 2 Conventional methods for synthesizing iridium black require the use of surfactants, sodium borohydride reducing agents or template agents, and organic solvents, resulting in high production costs and the generation of large amounts of organic wastewater, as detailed in patents CN 103157467B, CN 104437481B, and CN 103055853 B. The main method for iridium oxide catalysts is the Adams method (Electrochimica Acta 56(2011)10223–10230, R. Adams, R. Shriner, J. Am. Chem. Soc. 45(1923)2171-2179). This method requires the use of nitrates in excess of iridium by tens of times during synthesis, generating large amounts of NOx and other harmful substances during calcination, necessitating further tail gas treatment. Simultaneously, the treatment of nitrogen-containing wastewater generated during washing must be considered.

[0004] In summary, existing oxygen evolution catalysts each have their shortcomings, and there is a lack of environmentally friendly and economical preparation methods. Summary of the Invention

[0005] One object of this invention is to provide an Ir@IrOx core-shell catalyst for use as an anode in proton exchange membrane water electrolysis for hydrogen production, which overcomes the shortcomings of existing iridium black catalysts and iridium oxide catalysts. Another object of this invention is to provide an environmentally friendly and economical method for preparing the aforementioned catalyst.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] 1. An Ir@IrOx core-shell catalyst, the XRD spectrum of which shows both characteristic peaks of elemental iridium and characteristic peaks of amorphous IrOx.

[0008] 2. According to any of the aforementioned catalysts, the XPS spectrum of the catalyst contains both Ir(IV) and Ir(III) characteristic peaks in the Ir 4f peak, and the ratio of Ir(III) / (Ir(IV)+Ir(III)) is 45% to 50%.

[0009] 3. According to any of the aforementioned catalysts, wherein the cyclic voltammetric analysis spectrum of the catalyst has Ir(III) / Ir(IV) characteristic peaks between 0.7V and 1.0V, and the integrated charge is not less than 120C / g.

[0010] 4. According to any of the aforementioned catalysts, wherein the particle size of the catalyst observed on TEM is 3 nm to 4 nm.

[0011] 5. According to any of the aforementioned catalysts, wherein the specific surface area of ​​the catalyst is 50 m². 2 / g~80m 2 / g.

[0012] 6. According to any of the aforementioned catalysts, wherein the reduction temperature of the catalyst in the TPR analysis test is 30℃~50℃.

[0013] 7. A method for preparing an Ir@IrOx core-shell catalyst, comprising:

[0014] S1, an iridium source and a complexing agent are mixed in water to form a solution; the complexing agent is selected from one or more organic polybasic acids and their soluble salts;

[0015] S2, adjust the pH of the solution to 8-9, and react;

[0016] S3, remove water to obtain catalyst precursor;

[0017] S4, the catalyst precursor is calcined under a nitrogen atmosphere;

[0018] S5, the calcined powder is placed in an oxygen atmosphere for further calcination, and after washing and drying, a catalyst is obtained.

[0019] 8. According to any of the foregoing preparation methods, wherein the iridium source is chloroiridic acid or a soluble salt of chloroiridic acid (such as an alkali metal salt of chloroiridic acid).

[0020] 9. According to any of the foregoing preparation methods, wherein the complexing agent is selected from one or more of citric acid, tartaric acid and malic acid.

[0021] 10. According to any of the aforementioned preparation methods, wherein the molar ratio of the complexing agent to iridium is 50:(25-50), preferably 50:(30-40).

[0022] 11. According to any of the aforementioned preparation methods, the mass fraction of chloroiridic acid (excluding the mass of water of crystallization) is 0.5% to 10% based on the mass of the S1 solution.

[0023] 12. According to any of the aforementioned preparation methods, wherein in S2, a pH adjuster is used to adjust the pH value, and the pH adjuster is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia water.

[0024] 13. The preparation method described above, wherein the reaction temperature is 40℃~80℃ and the reaction time is 2h~12h.

[0025] 14. According to any of the aforementioned preparation methods, the calcination temperature under the nitrogen atmosphere is 400℃~500℃, and the calcination time is 1h~2h.

[0026] 15. According to any of the aforementioned preparation methods, wherein the calcination temperature under the oxygen atmosphere is 300℃~400℃ and the calcination time is 2h~4h.

[0027] 16. According to any of the aforementioned preparation methods, the washing process further includes a drying operation at a temperature of 50°C to 70°C.

[0028] 17. An Ir@IrOx core-shell catalyst, characterized in that it is prepared by any of the aforementioned methods.

[0029] 18. The application of any of the aforementioned catalysts as oxygen evolution electrocatalysts in electrochemistry.

[0030] 19. A proton exchange membrane water electrolyzer, comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer, and an anode diffusion layer, characterized in that any of the aforementioned catalysts is used in the anode catalyst layer.

[0031] 20. A method for producing hydrogen by electrolysis of water, characterized in that any of the aforementioned catalysts or the aforementioned proton exchange membrane water electrolyzers are used.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects.

[0033] This invention utilizes an organic polybasic acid to complex with iridium to create a precursor, followed by calcination under nitrogen and oxygen atmospheres to produce a novel catalyst. This catalyst exhibits a typical core-shell structure, with a metallic Ir core and an amorphous IrOx shell.

[0034] Compared with existing technologies, the preparation method provided by this invention does not use easily explosive reagents such as sodium nitrate and sodium borohydride, nor does it use expensive surfactants such as triblock copolymers, thus having the advantage of low raw material cost.

[0035] The manufacturing method of this invention is simple, has high production efficiency, and the atomic utilization rate of iridium metal can reach 100%.

[0036] The oxygen evolution activity and stability of the catalyst of the present invention are superior to those of commercial iridium oxide catalysts and iridium black catalysts.

[0037] Other features and advantages of the present invention will be described in detail in the Detailed Description section. Attached Figure Description

[0038] Figure 1 This is a TEM image of the catalyst from Example 1.

[0039] Figure 2 The cyclic voltammetry spectra of the catalysts in Example 1 and the comparative examples are shown.

[0040] Figure 3 The image shows the XRD pattern of the catalyst in Example 1.

[0041] Figure 4 XPS spectra of the catalysts in Example 1 and Comparative Example 2.

[0042] Figure 5 The H2-TPR spectra of the catalysts of Example 1 and Comparative Example 2 are shown. Detailed Implementation

[0043] The present invention is described in detail below with reference to specific embodiments. However, it should be noted that the scope of protection of the present invention is not limited by these specific embodiments and principle explanations, but is determined by the claims.

[0044] In this invention, except where expressly stated, any matters or issues not mentioned herein are directly applicable to those known in the art without any modification. Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or concepts are considered part of the original disclosure or record of this invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination clearly unreasonable.

[0045] All features disclosed in this invention can be combined arbitrarily, and such combinations should be understood as the content disclosed or described in this invention. Unless those skilled in the art consider such combinations to be obviously unreasonable, they should all be regarded as specifically disclosed and described in this invention. The numerical points disclosed in this specification include not only the numerical points specifically disclosed in the embodiments, but also the endpoints of each numerical range in the specification. Any range of combinations of these numerical points should be regarded as the range disclosed or described in this invention.

[0046] In this invention, the technical and scientific terms that are given a definition shall be used as defined thereon, and those that are not given a definition shall be understood according to their common meaning in the art.

[0047] Unless otherwise specified, the numerical range defined in this invention includes the endpoints of the numerical range.

[0048] In this invention, unless otherwise specified, the term "soluble" refers to being soluble in water.

[0049] In this invention, "optional" means either present or absent. For example, A and optional B means "A without B" or "A and B".

[0050] In this invention, Ir@IrOx represents a core of metallic iridium and a shell of iridium oxide; where X indicates that there is no restriction on the oxidation state of iridium in the iridium oxide.

[0051] This invention provides an Ir@IrOx core-shell catalyst, whose XRD spectrum shows both characteristic peaks of elemental iridium and characteristic peaks of amorphous IrOx.

[0052] According to the catalyst of the present invention, the XRD spectrum of the catalyst contains both characteristic peaks of elemental iridium and characteristic peaks of amorphous IrOx between 20° and 70°.

[0053] According to the catalyst of the present invention, in the XRD spectrum of the catalyst, there are only characteristic peaks of elemental iridium and amorphous IrOx between 20° and 70°, and no other characteristic peaks.

[0054] According to the catalyst of the present invention, the XPS spectrum of the catalyst has both Ir(IV) and Ir(III) characteristic peaks in the Ir 4f peak, and the ratio of Ir(III) / (Ir(IV)+Ir(III)) is 45% to 50%.

[0055] According to the catalyst of the present invention, the catalyst has a core-shell structure, with the core being iridium metal and the outer shell being amorphous IrOx.

[0056] The catalyst according to the present invention has a particle size of 3 nm to 4 nm as observed by high-resolution transmission electron microscopy (TEM).

[0057] According to the catalyst of the present invention, the catalyst has a specific surface area of ​​50 m². 2 / g~80m 2 / g.

[0058] According to the catalyst of the present invention, the reduction temperature of the catalyst in TPR analysis is 30℃~50℃, generally 35℃~42℃.

[0059] This invention also provides a method for preparing an Ir@IrOx core-shell catalyst, comprising:

[0060] S1, an iridium source and a complexing agent are mixed in water to form a solution; the complexing agent is selected from one or more organic polybasic acids and their soluble salts;

[0061] S2, adjust the pH of the solution to 8-9, and react;

[0062] S3, remove water to obtain catalyst precursor;

[0063] S4, the catalyst precursor is calcined under a nitrogen atmosphere;

[0064] S5, the calcined powder is placed in an oxygen atmosphere for further calcination, and after washing and drying, a black catalyst powder is obtained.

[0065] According to the preparation method of the present invention, in S1, the complexing agent is preferably selected from one or more of C4-C8 organic polybasic acids and their soluble salts, and more preferably from one or more of citric acid, tartaric acid and malic acid.

[0066] According to the preparation method of the present invention, in S1, the iridium source is preferably chloroiridic acid or a soluble salt of chloroiridic acid. The iridium source may or may not contain water of crystallization.

[0067] According to the preparation method of the present invention, in S1, there is no particular limitation on the concentration of the iridium source in the aqueous solution. Based on the mass of the aqueous solution, the mass fraction of the iridium source can be 0.5% to 10%.

[0068] Under the guidance of this invention, those skilled in the art can select a suitable molar ratio of complexing agent to iridium (on an atomic basis). Generally, in S1, the molar ratio of complexing agent to iridium (on an atomic basis) is 50:(25 to 50), preferably 50:(30 to 40).

[0069] According to the preparation method of the present invention, in S2, the pH value of the solution needs to be adjusted to 8-9, and then the reaction is carried out for a certain period of time. The pH value of the solution can be adjusted by one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia water.

[0070] According to the preparation method of the present invention, in S2, the reaction temperature can be 40℃~80℃ and the time can be 2h~12h.

[0071] According to the preparation method of the present invention, there are no particular limitations on the method of removing water from the solution in S3; any existing known method can be used, such as rotary evaporation and / or vacuum evaporation. The rotary evaporation can be carried out at a temperature of 70°C to 100°C, preferably at a temperature of 80°C to 85°C.

[0072] According to the preparation method of the present invention, in S4, the catalyst precursor is first calcined under a nitrogen atmosphere at a temperature of 400℃ to 500℃ for a time of 1h to 2h.

[0073] According to the preparation method of the present invention, in S5, the catalyst calcined in S4 is further calcined in an oxygen atmosphere, the calcination temperature is 300℃~400℃, and the calcination time is 2h~4h.

[0074] According to the preparation method of the present invention, in S4 and S5, there is no particular limitation on the heating rate during calcination, which can be 0.5℃ / min to 10℃ / min, and generally 1℃ / min to 5℃ / min.

[0075] According to the preparation method of the present invention, in step S5, washing can be stopped when no chloride ions are detected in the solvent after washing or when its pH value is neutral. Preferably, the washing operation is stopped after detecting that no chloride ions are detected in the solvent after washing.

[0076] According to the preparation method of the present invention, in step S5, the washed catalyst is dried in a forced-air drying oven. The drying temperature can be 50°C to 70°C, and the drying time can be 8 hours to 24 hours.

[0077] The present invention also provides an Ir@IrOx core-shell catalyst, which is prepared by any of the foregoing methods. Other characteristics of the catalyst are the same as those described above, and will not be repeated here.

[0078] This invention also provides the application of any of the aforementioned catalysts as oxygen evolution electrocatalysts in electrochemistry.

[0079] The present invention also provides a proton exchange membrane water electrolyzer, comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer, and an anode diffusion layer, wherein the anode catalyst layer uses any of the aforementioned catalysts.

[0080] The present invention also provides a method for producing hydrogen by electrolysis of water, which uses any of the aforementioned catalysts or the aforementioned proton exchange membrane water electrolyzer.

[0081] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way.

[0082] Reagents, Instruments and Tests

[0083] All raw materials used in the examples were obtained commercially and, unless otherwise specified, were of analytical grade. The chloroiridic acid raw material was in liquid form with an iridium mass fraction of 35%. For ease of use, it was prepared as a 0.182 mol / L solution, but solutions with higher concentrations can also be prepared.

[0084] Instruments, methods and conditions for TEM analysis: The high-resolution transmission electron microscope (HRTEM) used in this invention is model JEM-2100 (HRTEM) (Nippon Electron Ltd.), and the high-resolution transmission electron microscope test conditions are: accelerating voltage of 200kV.

[0085] Instruments, methods, and conditions for XPS analysis: This invention utilizes X-ray photoelectron spectroscopy (XPS) to detect elements on the surface of materials. The X-ray photoelectron spectroscopy instrument used is a VG Scientific ESCALab220i-XL model equipped with Avantage V5.926 software. The X-ray photoelectron spectroscopy analysis conditions are as follows: the excitation source is monochromatic AlKα X-rays, the power is 330W, and the basic vacuum during analysis is 3×10⁻⁶. -9 mbar. In addition, the electron binding energy is corrected using the C1s peak of elemental carbon (284.8 eV).

[0086] Instruments, methods and conditions for XRD analysis: X-ray diffraction analysis (XRD) was performed on a Shimadzu XRD-6000 X-ray diffractometer from Japan. The test conditions included: tube voltage 40 kV, tube current 40 mA, Cu target Kα radiation, and 2θ scan range of 5° to 80°.

[0087] BET testing method: In this invention, the pore structure properties of the sample were determined by a Quantachrome AS-6B analyzer, the specific surface area and pore volume of the catalyst were obtained by the Brunauer-Emmett-Taller (BET) method, and the pore distribution curve was calculated from the desorption curve using the Barrett-Joyner-Halenda (BJH) method.

[0088] TPR testing method: In this invention, the TPR test uses a fully automated chemical adsorption instrument (2920) by McMill, with a test temperature range of room temperature to 300℃ and a heating rate of 5℃ / min.

[0089] The electrochemical workstation was a PARSTAT3000A-DX, and the rotating disk electrode was a 636A. A three-electrode system was used: a saturated calomel electrode as the reference electrode, a platinum sheet as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions was a 0.5M H₂SO₄ solution. The catalyst to be tested was ultrasonically and uniformly dispersed in a mixed solution of isopropanol, water, and Nafion, and then dropped onto the surface of the glassy carbon electrode. After natural drying, the working electrode was obtained, with a catalyst loading of 0.38 mg / cm³. 2 The test temperature was 25℃. Before the test, oxygen was purged for 30 minutes to saturate the solution. The rotation speed was 2500 rpm. The scanning range for the cyclic voltammetry curve was 0.26–1.46 V (vs RHE), and the scanning range for the linear polarization curve was 1.2 V–1.6 V (vs RHE), with a scan rate of 5 mV / s. The stability test scan range was 1.26 V–1.56 V (vs RHE), with a scan rate of 50 mV / s and 10,000 scan cycles.

[0090] Example 1

[0091] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, add 1.58 g of citric acid, and stir at 75 °C for 0.5 h to make the citric acid and chloroiridic acid fully mixed;

[0092] (2) Add a certain amount of Na2CO3 solution dropwise to the above solution to make the pH value of the solution between 8 and 9, and stir the reaction at 75°C for 2 hours.

[0093] (3) The above solution was evaporated by rotary evaporation at 80°C to dry the water and obtain the catalyst precursor;

[0094] (4) Place the catalyst precursor in an oven and dry it at 120°C for 24 hours;

[0095] (5) Take out the dried catalyst precursor, cool it and grind it, spread it evenly in a porcelain boat, introduce nitrogen into the muffle furnace, and calcine it at a heating rate of 5℃ / min to 450℃ under nitrogen atmosphere for 1h.

[0096] (6) After cooling to room temperature, oxygen is introduced and calcined at 350°C at a heating rate of 2°C / min for 2 hours.

[0097] (7) Take out the calcined solid, cool it to room temperature, add a mixed solution of water and ethanol with a volume ratio of 1:1, ultrasonically wash it at room temperature for 10 minutes, then centrifuge it at 10000 rpm for 10 minutes, discard the supernatant after centrifugation, and continue to repeat the above steps until chloride ions are not detected by silver nitrate, and the washing process is over.

[0098] (8) The washed solid was placed in a forced-air drying oven and dried at 60°C for 12 hours to obtain the catalyst.

[0099] The instruments and conditions for testing and characterizing the electrochemical performance of the catalyst are described above, and the results are shown in Table 1.

[0100] The catalyst in this embodiment, TEM image is shown below. Figure 1 ; see cyclic voltammetry chart Figure 2 XRD patterns are shown below. Figure 3 XPS plots can be found here. Figure 4 See H2-TPR diagram Figure 5 .

[0101] Example 2

[0102] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, add 1.83 g of citric acid, and stir at 75 °C for 0.5 h to ensure that the citric acid and chloroiridic acid are fully mixed;

[0103] (2) Add a certain amount of Na2CO3 solution dropwise to the above solution to make the pH value of the solution between 8 and 9, and stir the reaction at 75°C for 2 hours.

[0104] (3) The above solution was evaporated by rotary evaporation at 80°C to dry the water and obtain the catalyst precursor;

[0105] (4) Place the catalyst precursor in an oven and dry it at 120°C for 24 hours;

[0106] (5) Take out the dried catalyst precursor, cool it and grind it, spread it evenly in a porcelain boat, introduce nitrogen into the muffle furnace, and calcine it at a heating rate of 5℃ / min to 450℃ under nitrogen atmosphere for 1h.

[0107] (6) After cooling to room temperature, oxygen is introduced and calcined at 350°C at a heating rate of 2°C / min for 2 hours.

[0108] (7) Take out the calcined solid, cool it to room temperature, add a mixed solution of water and ethanol with a volume ratio of 1:1, ultrasonically wash it at room temperature for 10 minutes, then centrifuge it at 10000 rpm for 10 minutes, discard the supernatant after centrifugation, and continue to repeat the above steps until chloride ions are not detected by silver nitrate, and the washing process is over.

[0109] (8) The washed solid was placed in a forced-air drying oven and dried at 60°C for 12 hours to obtain the catalyst.

[0110] The instruments and conditions for testing and characterizing the electrochemical performance of the catalyst are described above, and the results are shown in Table 1.

[0111] The catalyst in this embodiment has the same TEM spectrum as... Figure 1 Features shown in Example 1; Cyclic voltammetry spectrum is the same as... Figure 2 Features shown in Example 1; XRD pattern is the same Figure 3 Features shown in Example 1; XPS spectra are the same Figure 4 The features shown in Example 1, the H2-TPR spectrum is the same Figure 5 Features shown in Example 1.

[0112] Example 3

[0113] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, add 2.09 g of citric acid, and stir at 75 °C for 0.5 h to ensure that the citric acid and chloroiridic acid are fully mixed;

[0114] (2) Add a certain amount of Na2CO3 solution dropwise to the above solution to make the pH value of the solution between 8 and 9, and stir the reaction at 75°C for 2 hours.

[0115] (3) The above solution was evaporated by rotary evaporation at 80°C to dry the water and obtain the catalyst precursor;

[0116] (4) Place the catalyst precursor in an oven and dry it at 120°C for 24 hours;

[0117] (5) Take out the dried catalyst precursor, cool it and grind it, spread it evenly in a porcelain boat, introduce nitrogen into the muffle furnace, and calcine it at a heating rate of 5℃ / min to 450℃ under nitrogen atmosphere for 1h.

[0118] (6) After cooling to room temperature, oxygen is introduced and calcined at 350°C at a heating rate of 2°C / min for 2 hours.

[0119] (7) Take out the calcined solid, cool it to room temperature, add a mixed solution of water and ethanol with a volume ratio of 1:1, ultrasonically wash it at room temperature for 10 minutes, then centrifuge it at 10000 rpm for 10 minutes, discard the supernatant after centrifugation, and continue to repeat the above steps until chloride ions are not detected by silver nitrate, and the washing process is over.

[0120] (8) The washed solid was placed in a forced-air drying oven and dried at 60°C for 12 hours to obtain the catalyst.

[0121] The instruments and conditions for testing and characterizing the electrochemical performance of the catalyst are described above, and the results are shown in Table 1.

[0122] The catalyst in this embodiment has the same TEM spectrum as... Figure 1 Features shown in Example 1; Cyclic voltammetry spectrum is the same as... Figure 2 Features shown in Example 1; XRD pattern is the same Figure 3 Features shown in Example 1; XPS spectra are the same Figure 4 The features shown in Example 1, the H2-TPR spectrum is the same Figure 5 Features shown in Example 1.

[0123] Comparative Example 1: Commercial Iridium Black Catalyst

[0124] Purchased from Alfa, product number 047150.

[0125] The instruments and conditions for testing and characterizing the electrochemical performance of the catalyst are described above, and the results are shown in Table 1.

[0126] The catalyst in this comparative example has the following cyclic voltammetric spectrum: Figure 2 .

[0127] Comparative Example 2: Commercial Iridium Oxide Catalyst

[0128] Purchased from Sigma Aldrich, product number 206237.

[0129] The instruments and conditions for testing and characterizing the electrochemical performance of the catalyst are described above, and the results are shown in Table 1.

[0130] The catalyst in this comparative example has the following cyclic voltammetric spectrum: Figure 2 XPS plots can be found here. Figure 4 See H2-TPR diagram Figure 5 .

[0131] Table 1

[0132] <![CDATA[Specific surface area / m 2 / g]]> 68.6 55.4 53.5 13.8 130.0 Ir(III) / ((Ir(III)+Ir(IV)) 45.8 46.2 48.1 / 15.54 TPR / ℃ 41 43 44 / 100 Integrated charge (0.7-1.0V) / C / g 127 122 133 77 41 <![CDATA[Initial overpotential / mV@10mA / cm 2 > 229 231 225 232 260 <![CDATA[Final overpotential / mV@10mA / cm 2 > 244 245 245 348 279

[0133] Depend on Figure 1As can be seen, the lighter-colored areas of the catalyst prepared in Example 1 (the darker areas are due to incomplete dispersion of the catalyst, with the catalyst piled up) indicate a catalyst particle size between 3 nm and 4 nm. Figure 2 As can be seen from the cyclic voltammogram, the catalyst prepared in Example 1 exhibits a distinct Ir(III) / Ir(IV) characteristic peak between 0.7 V and 1.0 V, which is significantly stronger than that of commercial iridium black (Comparative Example 1) and iridium oxide (Comparative Example 2) catalysts. Figure 3 As can be seen, the catalyst prepared in Example 1 exhibits two distinct diffraction peaks at 40.7° and 47.3°, corresponding to the (111) and (200) crystal planes of metallic Ir, respectively, indicating that the catalyst of the present invention contains metallic iridium. In addition, the catalyst prepared in Example 1 also shows an amorphous IrOx peak between 30° and 35°. Figure 4 As can be seen, the catalyst prepared in Example 1 has a higher proportion of Ir(III) characteristic peaks compared to commercial iridium oxide catalysts, and the Ir(III) proportion reaches 45.8% (Table 1). Furthermore, besides Ir(III) and Ir(IV), there are no Ir(O) characteristic peaks on the catalyst surface, indicating that the catalyst surface is amorphous IrOx. The XRD and XPS results together indicate that the catalyst of this invention is an Ir@IrOx core-shell catalyst, with the bulk phase being metallic elemental iridium and the surface being amorphous IrOx. Figure 5 It can be seen that the reduction temperature of the catalyst prepared in Example 1 under a hydrogen atmosphere is significantly lower than that of the commercial IrO2 (Comparative Example 2) catalyst.

[0134] As shown in Table 1, the initial overpotentials of the catalysts prepared in Examples 1, 2, and 3 are all superior to those of the commercial iridium black catalyst (Comparative Example 1) and the commercial iridium oxide catalyst (Comparative Example 2). After stability testing, the increase in the final overpotential of the catalysts prepared in Examples 1, 2, and 3 compared to the initial overpotential is significantly lower than that of the commercial iridium black catalyst (Comparative Example 1), and slightly better than that of the commercial iridium oxide catalyst, indicating that the catalysts of the present invention possess both high activity and high stability.

Claims

1. An Ir@IrOx core-shell catalyst, characterized in that, The XRD pattern of the catalyst shows both characteristic peaks of elemental iridium and characteristic peaks of amorphous IrOx; the catalyst surface is amorphous IrOx; the XPS pattern of the catalyst shows both Ir(IV) and Ir(III) characteristic peaks in the Ir 4f pattern, and the ratio of Ir(III) / (Ir(IV)+Ir(III)) is 45% to 50%.

2. The catalyst according to claim 1, characterized in that, The cyclic voltammetric analysis spectrum shows an Ir(III) / Ir(IV) oxidation peak between 0.7 and 1.0 V, and the integrated charge is not less than 120 C / g.

3. The catalyst according to claim 1, characterized in that, The particle size observed on the catalyst via TEM was 3 nm to 4 nm.

4. The catalyst according to claim 1, characterized in that, The catalyst has a specific surface area of ​​50 m². 2 / g~80m 2 / g.

5. The catalyst according to claim 1, characterized in that, In the TPR analysis test, the reduction temperature of the catalyst was 30℃~50℃.

6. The method for preparing the Ir@IrOx core-shell catalyst according to claim 1, comprising: S1, an iridium source and a complexing agent are mixed in water to form a solution; the complexing agent is selected from one or more organic polybasic acids and their soluble salts; S2, adjust the pH of the solution to 8-9, and react; S3, remove water to obtain catalyst precursor; S4, the catalyst precursor is calcined under a nitrogen atmosphere; S5, the calcined powder is placed in an oxygen atmosphere for further calcination, and after washing and drying, a catalyst is obtained.

7. The preparation method according to claim 6, characterized in that, The complexing agent is selected from one or more of citric acid, tartaric acid, and malic acid.

8. The preparation method according to claim 6, characterized in that, The molar ratio of the complexing agent to iridium is 50:(25-50).

9. The preparation method according to claim 6, characterized in that, The calcination temperature under a nitrogen atmosphere is 400℃~500℃, and the calcination time is 1h~2h.

10. The preparation method according to claim 6, characterized in that, The calcination temperature under an oxygen atmosphere is 300℃~400℃, and the calcination time is 2h~4h.

11. The preparation method according to claim 6, characterized in that, The iridium source is chloroiridic acid or a soluble salt of chloroiridic acid.

12. The preparation method according to claim 6, characterized in that, The washing process also includes a drying operation at a temperature of 50°C to 70°C.

13. An Ir@IrOx core-shell catalyst, characterized in that, It is prepared by any of the methods in claims 6 to 12.

14. The application of the catalyst according to any one of claims 1 to 5 and claim 13 as an oxygen evolution electrocatalyst in electrochemistry.

15. A proton exchange membrane water electrolyzer, comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer, and an anode diffusion layer, characterized in that, The anode catalyst layer uses any one of the catalysts described in claims 1 to 5 and claim 13.

16. A method for producing hydrogen by electrolysis of water, characterized in that, The catalyst described in any one of claims 1 to 5 and claim 13 was used, or the proton exchange membrane water electrolyzer described in claim 15 was used.

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