A composite catalyst of iridium and iridium oxide and its preparation method and application

Abstract

The application provides an iridium and iridium oxide composite catalyst and a preparation method and application thereof. The XRD spectrum of the catalyst has characteristic peaks of elemental iridium and does not have characteristic peaks of iridium dioxide. The preparation method can avoid the use of sodium borohydride reducing agent and surfactant, does not produce solid waste and NOx exhaust gas, and has high atomic utilization rate of iridium metal. When the catalyst is used as an anode catalyst for hydrogen production by water electrolysis of a proton exchange membrane, the catalyst has the characteristics of low overpotential, high activity and good stability.

Description

Technical Field

[0001] The invention relates to a composite catalyst of iridium and iridium oxide, and a preparation method and application thereof. Background Art

[0002] Compared to alkaline water electrolysis, proton exchange membrane water electrolysis technology has the advantages of fast response, strong load adjustability, high current density, and high hydrogen production efficiency. It has developed rapidly in recent years, especially the use of renewable energy to generate electricity and then electrolyze water to produce hydrogen. It is widely recognized in the hydrogen energy field as the main method for hydrogen production in the future and is of great significance to the development of hydrogen energy. Anode catalysts are one of the key materials for proton exchange membrane water electrolysis to produce hydrogen. The main function of anode catalysts is to oxidize water molecules to produce oxygen and hydrogen protons under electrochemical action. This reaction is the main rate-controlling step in water electrolysis hydrogen production. Under normal circumstances, the anode overpotential is much higher than the cathode overpotential, which is one of the main factors determining the efficiency of water electrolysis hydrogen production.

[0003] Commonly used oxygen evolution catalysts are iridium black and iridium dioxide. Metallic iridium resources are scarce and expensive, and the catalytic activity and stability of existing catalysts are not ideal. The Ir dosage in the electrolytic cell is generally higher than 2 mg / cm 2 Conventional synthesis methods for iridium black require the use of surfactants, sodium borohydride reducing agents or templates, organic solvents, and the like, resulting in high production costs and the generation of large amounts of organic wastewater. For details, see patents CN 103157467B, CN 104437481B, and CN 103055853 B. Iridium oxide catalysts primarily utilize the Adams method (Electrochimica Acta 56 (2011) 10223–10230, R. Adams, R. Shriner, J. Am. Chem. Soc. 45 (1923) 2171-2179). During the synthesis process, nitrate is used in an excess of several dozen times the amount of iridium. During the calcination process, large amounts of harmful substances such as NOx are generated, requiring further tail gas treatment. Furthermore, the treatment of nitrogen-containing wastewater generated during washing must be considered.

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

[0005] One object of the present invention is to provide a composite catalyst of iridium and iridium oxide for use as an anode in proton exchange membrane water electrolysis for hydrogen production. This catalyst can overcome the shortcomings of existing iridium black catalysts and iridium oxide catalysts. Another object of the present invention is to provide an environmentally friendly and economical method for preparing the aforementioned catalyst.

[0006] In order to achieve the above objectives, the present invention provides the following technical solutions.

[0007] 1. A composite catalyst of iridium and iridium oxide, wherein the XRD spectrum of the catalyst has characteristic peaks of elemental iridium but no characteristic peaks of iridium dioxide.

[0008] 2. The catalyst according to any one of the above, wherein the Ir 4f 7 / 2 Among the characteristic peaks, there is a characteristic peak of iridium oxide, but no characteristic peak of elemental iridium.

[0009] 3. The catalyst according to any one of the above, wherein the Ir 4f 7 / 2 Among the characteristic peaks, there is a characteristic peak of iridium oxide, but no characteristic peak of elemental iridium; and relative to the characteristic peak of iridium dioxide, the characteristic peak of iridium oxide shifts toward the direction of low electron binding energy.

[0010] 4. A catalyst according to any of the above, wherein the particle size of the catalyst is 1 nm to 10 nm, preferably 1 nm to 5 nm.

[0011] 5. A catalyst according to any one of the preceding claims, wherein the iridium content of the catalyst is 92% to 95% based on the mass of the catalyst.

[0012] 6. A method for preparing a composite catalyst of iridium and iridium oxide, comprising:

[0013] S1, mixing an iridium source and a complexing agent in water to prepare a solution; the complexing agent is selected from one or more organic polyacids and soluble salts thereof (preferably one or more organic polyacids of C4 to C8 and soluble salts thereof);

[0014] S2, adjusting the pH value of the solution in S1 to 7-10 (preferably 8-9), reacting;

[0015] S3, removing water to obtain a catalyst precursor;

[0016] S4, calcining the catalyst precursor in an oxygen-containing atmosphere, and washing the catalyst precursor to obtain a product.

[0017] 7. A preparation method according to any of the above, wherein the iridium source is chloroiridic acid or a soluble salt of chloroiridic acid (such as an alkali metal salt of chloroiridic acid).

[0018] 8. According to any of the above preparation methods, wherein the complexing agent is selected from one or more of citric acid, tartaric acid and malic acid.

[0019] 9. A preparation method according to any of the above, wherein the molar ratio of the complexing agent to iridium is 50:(5-50), preferably 50:(20-35).

[0020] 10. A preparation method according to any of the above, wherein the mass fraction of chloroiridic acid (excluding the mass of crystal water) is 0.5% to 40% based on the mass of the solution of S1.

[0021] 11. According to any of the above preparation methods, wherein the pH value is adjusted by a pH adjuster in S2, and the pH adjuster is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia water.

[0022] 12. According to any of the above preparation methods, wherein the reaction temperature is 15°C to 95°C, preferably 50°C to 85°C; and the reaction time is 1h to 12h, preferably 2h to 4h.

[0023] 13. According to any of the above preparation methods, wherein the calcination temperature is 200°C to 800°C, preferably 300°C to 500°C; the calcination time is 0.5h to 6h, preferably 1h to 3h.

[0024] 14. A preparation method according to any of the above, wherein the heating rate during calcination is 0.5°C to 10°C, preferably 1°C to 5°C.

[0025] 15. According to any of the aforementioned preparation methods, wherein the solvent used for washing is a mixed solution of alcohol and water, and the alcohol accounts for 10% to 95% (preferably 30% to 60%) of the mass of the mixed solution; the alcohol is preferably one or more of methanol, ethanol, n-propanol and isopropanol.

[0026] 16. A preparation method according to any of the above, wherein the oxygen-containing atmosphere is air, oxygen or a mixture of the two.

[0027] 17. According to any of the above-mentioned preparation methods, wherein the washing further includes a drying operation, and the drying temperature is ≤10°C (preferably ≤0°C, more preferably -30°C to -10°C).

[0028] 18. A composite catalyst of iridium and iridium oxide, characterized in that it is prepared by any of the above methods.

[0029] 19. Use of any of the above catalysts as an oxygen evolution electrocatalyst in electrochemistry.

[0030] 20. 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 any of the aforementioned catalysts is used in the anode catalyst layer.

[0031] 21. A method for producing hydrogen by electrolyzing water, characterized in that any of the aforementioned catalysts or the aforementioned proton exchange membrane water electrolyzer is used.

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

[0033] 1. The present invention adopts a method of preparing a precursor by complexing an organic polyacid with iridium and then calcining it in an oxygen-containing atmosphere to produce a catalyst with a novel structure. The bulk phase of the catalyst is metallic iridium and the surface is iridium oxide. In particular, the iridium in the iridium oxide has a valence between +4 and 0.

[0034] 2. Compared with the prior art, the reaction process of the present invention does not use organic solvents and surfactants, does not use oxidants and reducing agents such as sodium nitrate and sodium borohydride, and neither produces solid waste such as sodium borate or sodium borite nor NOx waste gas. It is a green and environmentally friendly manufacturing method.

[0035] 3. The manufacturing method of the present invention is simple, has high production efficiency, and the atomic utilization rate of iridium metal can reach 100%.

[0036] Fourth, the catalyst of the present invention has a lower overpotential than pure iridium oxide, a significantly higher mass specific activity than pure iridium oxide, and a significantly better stability than iridium black.

[0037] Other features and advantages of the present invention will be described in detail in the detailed description section. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 TEM image of the catalyst of Example 1.

[0039] Figure 2 The XRD patterns of the catalysts in Example 1 and comparative examples are shown.

[0040] Figure 3 The XPS spectra of the catalysts of Example 1 and comparative examples are shown. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with specific embodiments. However, it should be noted that the protection scope of the present invention is not limited by these specific embodiments and principle explanations, but is determined by the claims.

[0042] In the present invention, except for the contents explicitly described, any matters or issues not mentioned are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical concepts formed thereby are considered part of the original disclosure or description of the present invention and should not be regarded as new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0043] All features disclosed in this invention may be combined in any combination, and such combinations should be understood as disclosed or described in this invention. Unless a person skilled in the art considers such combinations to be obviously unreasonable, such combinations should be considered as specifically disclosed and described in this invention. The numerical values ​​disclosed in this specification include not only the numerical values ​​specifically disclosed in the examples, but also the endpoints of the numerical ranges in this specification. The ranges of any combination of these numerical values ​​should be considered as the ranges disclosed or described in this invention.

[0044] Technical and scientific terms in the present invention shall be understood according to their definitions if they are defined, and shall be understood according to their general meanings in the art if they are not defined.

[0045] Unless otherwise specified, the numerical ranges defined herein include the endpoints of the numerical ranges.

[0046] In the present invention, unless otherwise specified, the term "soluble" means soluble in water.

[0047] In the present invention, "optionally" means "with" or "without", for example, A and optionally B means "A and not including B" or "A and B".

[0048] The invention provides a composite catalyst of iridium and iridium oxide. The XRD spectrum of the catalyst has characteristic peaks of elemental iridium but no characteristic peaks of iridium dioxide.

[0049] According to the catalyst of the present invention, in the XRD spectrum of the catalyst, there is only a characteristic peak of elemental iridium between 20° and 70°.

[0050] According to the catalyst of the present invention, the Ir 4f 7 / 2 Among the characteristic peaks, there is a characteristic peak of iridium oxide, but no characteristic peak of elemental iridium. 7 / 2 Among the characteristic peaks, the characteristic peak of iridium oxide shifts toward the direction of low electron binding energy relative to the characteristic peak of iridium dioxide. The valence state of the iridium oxide on the surface of the catalyst is between +4 and 0.

[0051] According to the catalyst of the present invention, the catalyst is a core-shell structure, and the core is iridium metal element.

[0052] According to the catalyst of the present invention, the particle size thereof is within 10 nm as observed by high-resolution transmission electron microscopy (TEM). In some embodiments, the particle size of the catalyst is 1 nm to 5 nm.

[0053] According to the catalyst of the present invention, the catalyst does not contain other metals except iridium.

[0054] The catalyst according to the present invention comprises iridium, oxygen and optionally carbon; preferably consists of iridium, oxygen and optionally carbon.

[0055] According to the catalyst of the present invention, based on the mass of the catalyst, the iridium content of the catalyst is 92% to 95% or 95% to 97%.

[0056] According to the catalyst of the present invention, the chlorine content of the catalyst may be 0-0.2%, preferably 0-0.1%, more preferably 0-0.05%, and further preferably 0-0.02%, based on the mass of the catalyst.

[0057] The catalyst according to the present invention may contain no carbon, or contain about 2% or less carbon, based on the mass of the catalyst. This carbon has no significant effect on the performance of the catalyst, and it is not necessary to accurately quantify it.

[0058] The present invention also provides a method for preparing a composite catalyst of iridium and iridium oxide, comprising:

[0059] S1, mixing an iridium source and a complexing agent in water to prepare a solution; the complexing agent is selected from one or more organic polyacids and soluble salts thereof;

[0060] S2, adjust the pH value of the solution to 7-10, and react;

[0061] S3, removing water to obtain a catalyst precursor;

[0062] S4, calcining the catalyst precursor in an oxygen-containing atmosphere, and washing the catalyst precursor to obtain a product.

[0063] 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 polyacids and soluble salts thereof, more preferably selected from one or more of citric acid, tartaric acid and malic acid.

[0064] 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, preferably an alkali metal salt of chloroiridic acid. The iridium source may or may not contain crystal water.

[0065] 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. The mass fraction of the iridium source can be 0.5% to 40%, preferably 20% to 40%, and more preferably 35% to 40%, based on the mass of the aqueous solution.

[0066] Under the guidance of the present invention, those skilled in the art can select a suitable molar ratio of the complexing agent to the iridium (by atom). Generally, in S1, the molar ratio of the complexing agent to the iridium (by atom) is 50:(5-50), preferably 50:(20-35).

[0067] According to the preparation method of the present invention, in S1, after the iridium source and the complexing agent are mixed in water, the mixture may be heated or not heated (preferably heated), and stirred or not stirred (preferably stirred). The heating temperature is generally maintained at 40°C to 95°C, preferably 50°C to 90°C. The stirring time is generally 0.5h to 2h, preferably 0.5h to 1h.

[0068] According to the preparation method of the present invention, in S2, the pH of the solution needs to be adjusted to 7-10, and then reacted for a certain time. Preferably, the pH of the solution is adjusted to alkaline, and more preferably, the pH of the solution is adjusted to 8-9. The pH of the solution can be adjusted with one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, and ammonia.

[0069] According to the preparation method of the present invention, in S2, the reaction temperature can be 15°C to 95°C, and the reaction time can be 1h to 12h; preferably, the reaction temperature is 50°C to 85°C, and the reaction time is 2h to 4h.

[0070] According to the preparation method of the present invention, there is no particular limitation on the method for removing water from the solution in S3, and any known method can be used, such as rotary evaporation and / or reduced pressure evaporation. The rotary evaporation can be performed at a temperature of 15°C to 95°C, preferably at a temperature of 50°C to 75°C.

[0071] According to the preparation method of the present invention, S3 preferably includes heating and drying the obtained catalyst precursor. The drying temperature of the catalyst precursor can be 80°C to 200°C, preferably 100°C to 140°C; and the drying time of the catalyst precursor can be 8 hours to 40 hours, preferably 22 hours to 26 hours.

[0072] According to the preparation method of the present invention, in S4, the catalyst precursor is first calcined in an oxygen-containing atmosphere, then washed, and then dried to finally obtain the product.

[0073] According to the preparation method of the present invention, in S4, the calcination is carried out in an oxygen-containing atmosphere, which is preferably air, oxygen, or a mixture of air and oxygen.

[0074] According to the method of the present invention, in S4, the calcination temperature is 200°C to 800°C, and the calcination time is 0.5h to 6h; preferably, the calcination temperature is 300°C to 500°C, and the calcination time is 1h to 3h.

[0075] According to the preparation method of the present invention, in S4, there is no particular limitation on the heating rate during calcination, which may be 0.5°C / min to 10°C / min, generally 1°C / min to 5°C / min.

[0076] When washing the aforementioned catalyst using water alone as the solvent, it is difficult to separate the catalyst from the aqueous phase by centrifugation. According to the method of the present invention, in S4, the washing solvent is preferably a mixed solution of alcohol and water, with the alcohol comprising 10% to 95% (preferably 30% to 60%) of the mixed solution by mass; the alcohol is preferably one or more of methanol, ethanol, n-propanol, and isopropanol, with ethanol being more preferred. In this case, the catalyst can be easily separated by centrifugation. When separation is performed at a speed of 10,000 r / min and the aforementioned alcohol-water mixed solution is used as the washing solvent, the centrifugation time can be 1 to 50 minutes, preferably 5 to 15 minutes.

[0077] According to the preparation method of the present invention, in S4, ultrasonic treatment may be used during the washing, and the ultrasonic treatment time may be 1 min to 50 min, preferably 5 min to 15 min.

[0078] According to the preparation method of the present invention, in S4, when it is detected that there are no chloride ions in the solvent after washing or the pH value is neutral, the washing operation can be ended. Preferably, the washing operation is ended after the detection that there are no chloride ions in the solvent after washing.

[0079] According to the preparation method of the present invention, after being fully washed, the catalyst contains no or substantially no chlorine element.

[0080] In some embodiments, in S4, the washed catalyst is dried in a freeze drying oven. The drying temperature may be -30°C to 10°C, or may be -30°C to -10°C. The drying time may be 8 hours to 40 hours, preferably 22 hours to 26 hours.

[0081] The present invention also provides a composite catalyst of iridium and iridium oxide, which is prepared by any of the above methods. The other features of the catalyst are the same as those of the catalyst described above, and the present invention will not repeat them.

[0082] The present invention further provides the use of any of the above catalysts as an oxygen evolution electrocatalyst in electrochemistry.

[0083] The present invention further 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 any of the aforementioned catalysts is used in the anode catalyst layer.

[0084] The present invention further provides a method for producing hydrogen by electrolyzing water, using any of the aforementioned catalysts or the aforementioned proton exchange membrane water electrolyzer.

[0085] The present invention will be described in detail below with reference to specific examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form.

[0086] Reagents, Instruments and Tests

[0087] The raw materials used in the examples were all commercially available and were analytically pure unless otherwise specified. The chloroiridic acid raw material was in liquid form, with an iridium mass fraction of 35%. For ease of use, a 0.182 mol / L solution was prepared, although higher concentrations could also be used.

[0088] TEM analysis instruments, methods and conditions: The high-resolution transmission electron microscope (HRTEM) used in the present invention is a JEM-2100 (HRTEM) (JEOL Ltd.), and the high-resolution transmission electron microscope test conditions are: an accelerating voltage of 200 kV.

[0089] Instruments, methods and conditions for EDX elemental analysis: EDX elemental analysis was measured by an EDS spectrometer equipped with a Japanese Hitachi S 4800 scanning electron microscope, with an accelerating voltage of 20 kV and WD = 15 mm.

[0090] XPS analysis instrument, method and conditions: The present invention uses X-ray photoelectron spectroscopy (XPS) to detect the elements on the surface of the material. The X-ray photoelectron spectroscopy analyzer used is an ESCALab220i-XL type X-ray electron spectrometer equipped with Avantage V5.926 software produced by VG Scientific. The X-ray photoelectron spectroscopy analysis test conditions are as follows: the excitation source is monochromatic A1Kα X-ray with a power of 330W, and the basic vacuum during the analysis test is 3×10 -9 In addition, the electron binding energy was calibrated using the C1s peak (284.3 eV) of elemental carbon.

[0091] Instruments, methods, and conditions for XRD analysis: X-ray diffraction analysis (XRD) was performed on a Shimadzu XRD-6000 diffractometer (Japan). The test conditions included: tube voltage 40 kV, tube current 40 mA, Cu target Kα radiation, and a 2θ scanning range of 5° to 80°.

[0092] The electrochemical workstation was a PARSTAT 3000A-DX, and the rotating disk electrode was a 636A. A three-electrode system was used, with 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 acidic electrolyte used was a 0.5 M H₂SO₄ solution. The catalyst to be tested was ultrasonically dispersed in a mixture of isopropanol, water, and Nafion, then dripped onto the surface of the glassy carbon electrode and allowed to dry naturally to obtain the working electrode. The catalyst loading was 0.38 mg·cm⁻¹. -2 The test temperature was 25°C. Oxygen was introduced for 30 minutes before testing to saturate the solution. The rotation speed was 2500 rpm. The linear polarization curve scan range was 1.2 V to 1.5 V (vs RHE) at a scan rate of 5 mV / s. The stability test scan range was 1.26 V to 1.56 V (vs RHE) at a scan rate of 50 mV / s, and the number of scans was 10,000.

[0093] Example 1

[0094] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, add 1.58 g of citric acid, and stir at 90 ° C for 0.5 h to fully mix the citric acid and chloroiridic acid;

[0095] (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 90°C for 3 hours;

[0096] (3) rotary evaporating the above solution at 70° C. to evaporate the water to obtain a catalyst precursor;

[0097] (4) The catalyst precursor was placed in an oven and dried at 120°C for 24 h;

[0098] (5) The dried catalyst precursor was taken out, ground after cooling, and placed flat on a porcelain boat. Oxygen was introduced into a muffle furnace. The temperature was raised to 400°C at a heating rate of 2°C / min under an oxygen atmosphere for 2 h.

[0099] (6) The calcined solid was taken out, cooled to room temperature, and a mixed solution of water and ethanol was added, with the volume ratio of water to ethanol being 1:1, and ultrasonic washing was performed at room temperature for 10 min, followed by centrifugation at a speed of 10,000 rpm for 10 min. After centrifugation, the supernatant was discarded and the above steps were repeated until no chloride ions were detected using silver nitrate, and the washing process was completed;

[0100] (7) The washed solid was placed in a freeze drying oven for freeze drying at -10°C for 24 h to obtain the catalyst.

[0101] The instruments and conditions for the electrochemical performance test and characterization of the catalyst are shown above, and the results are shown in Table 1.

[0102] The catalyst of this embodiment has a TEM spectrum. Figure 1 ; XRD pattern see Figure 2 ; XPS spectrum see Figure 3 .

[0103] Preparation Example 2

[0104] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, add 1.58 g of malic acid, and stir at 90 ° C for 0.5 h to allow the malic acid and chloroiridic acid to be fully mixed;

[0105] (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 90°C for 3 hours;

[0106] (3) rotary evaporating the above solution at 70° C. to dry the water to obtain a catalyst precursor;

[0107] (4) The catalyst precursor was placed in an oven and dried at 120°C for 24 h;

[0108] (5) The dried catalyst precursor was taken out, cooled, ground, and placed flat on a porcelain boat. Oxygen was introduced into a muffle furnace. The temperature was raised to 400°C at a heating rate of 2°C / min under an oxygen atmosphere and maintained for 2 h.

[0109] (6) The calcined solid was taken out, cooled to room temperature, and a certain amount of a mixed solution of water and ethanol was added, with the volume ratio of water to ethanol being 1:1, and ultrasonic washing was performed at room temperature for 10 min, followed by centrifugation at a speed of 10,000 rpm for 10 min. After centrifugation, the supernatant was discarded and the above steps were repeated until no chloride ions were detected using silver nitrate, and the washing process was completed;

[0110] (7) The washed solid was placed in a freeze drying oven for freeze drying at -10°C for 24 h to obtain the catalyst.

[0111] The instruments and conditions for the electrochemical performance test and characterization of the catalyst are shown above, and the results are shown in Table 1.

[0112] The catalyst of this embodiment has the same TEM spectrum as Figure 1 The characteristics shown in Example 1; XRD pattern is the same Figure 2 The features shown in Example 1; XPS spectrum is the same Figure 3 The features shown in Example 1.

[0113] Preparation Example 3

[0114] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, add 1.58 g of tartaric acid, and stir at 90 ° C for 0.5 h to allow the tartaric acid and chloroiridic acid to be fully mixed;

[0115] (2) Add a certain amount of sodium carbonate solution dropwise to the above solution to make the pH value of the solution between 8 and 9, and stir the reaction at 90°C for 3 hours;

[0116] (3) rotary evaporating the above solution at 70° C. to dry the water to obtain a catalyst precursor;

[0117] (4) The catalyst precursor was placed in an oven and dried at 120°C for 24 h;

[0118] (5) The dried catalyst precursor was taken out, cooled, ground, and placed flat on a porcelain boat. Oxygen was introduced into a muffle furnace. The temperature was raised to 400°C at a heating rate of 2°C / min under an oxygen atmosphere and maintained for 2 h.

[0119] (6) The calcined solid was taken out, cooled to room temperature, and a certain amount of a mixed solution of water and ethanol was added, with the volume ratio of water to ethanol being 1:1, and ultrasonic washing was performed at room temperature for 10 min, followed by centrifugation at a speed of 10,000 rpm for 10 min. After centrifugation, the supernatant was discarded and the above steps were repeated until no chloride ions were detected using silver nitrate, and the washing process was completed;

[0120] (7) The washed solid was placed in a freeze drying oven for freeze drying at -10°C for 24 h to obtain the catalyst.

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

[0122] The catalyst of this embodiment has the same TEM spectrum as Figure 1 The characteristics shown in Example 1; XRD pattern is the same Figure 2 The features shown in Example 1; XPS spectrum is the same Figure 3 The features shown in Example 1.

[0123] Comparative Example 1 (Adams method)

[0124] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution;

[0125] (2) Add 110 mL of 4.7 mol / L NaNO3 solution and stir at room temperature for 2 h;

[0126] (3) rotary evaporating the above solution at 70° C. to dry the water to obtain a catalyst precursor;

[0127] (4) Place the catalyst precursor in a forced air drying oven and dry it at 120°C for 24 hours;

[0128] (5) Take out the dried catalyst precursor, lay it flat on a porcelain boat, place it in a muffle furnace, and heat it to 500°C at a heating rate of 2°C / min and maintain it for 2 hours;

[0129] (6) The calcined solid was taken out, cooled to room temperature, and a certain amount of a mixed solution of water and ethanol was added, with the volume ratio of water to ethanol being 1:1, and ultrasonic washing was performed at room temperature for 10 min, followed by centrifugation at a speed of 10,000 rpm for 10 min. After centrifugation, the supernatant was discarded and the above steps were repeated until no chloride ions were detected using silver nitrate, and the washing process was completed;

[0130] (7) The washed solid was placed in a freeze drying oven for freeze drying at -10°C for 24 h to obtain the catalyst.

[0131] The instruments and conditions for the electrochemical performance test and characterization of the catalyst are shown above, and the results are shown in Table 1.

[0132] The catalyst of this comparative example has an XRD pattern as shown in Figure 2 ; XPS spectrum see Figure 3 .

[0133] Comparative Example 2 Commercial iridium black catalyst

[0134] Purchased from Alfa, product number 047150.

[0135] The instruments and conditions for the electrochemical performance test and characterization of the catalyst are shown above, and the results are shown in Table 1.

[0136] The catalyst of this comparative example has an XRD pattern as shown in Figure 2 ; XPS spectrum see Figure 3 .

[0137] Comparative Example 3 Commercial IrO2 Catalyst

[0138] Purchased from Sigma Aldrich, product number 206237.

[0139] The instruments and conditions for the electrochemical performance test and characterization of the catalyst are shown above, and the results are shown in Table 1.

[0140] The catalyst of this comparative example has an XRD pattern as shown in Figure 2 ; XPS spectrum see Figure 3 .

[0141] Table 1

[0142] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 EDX Elemental Analysis (Ir, wt%) 92.3 93.2 94.8 86.2 / / <![CDATA[初始过电势 / mV@10mA / cm 2 ]]> 228 230 231 280 232 260 <![CDATA[最终过电势 / mV@10mA / cm 2 ]]> 247 252 249 302 348 279

[0143] Depend on Figure 1 It can be seen that the lighter areas of the catalyst prepared in Example 1 (the darker areas are because the catalyst in these areas is not fully dispersed and the catalysts are stacked together) show that the catalyst particle size is between 1 and 5 nm. Figure 2 It can be seen that the commercial IrO2 catalyst (Comparative Example 3) and the catalyst prepared by the Adams method (Comparative Example 1) exhibit two obvious diffraction peaks at 28.0° and 34.7°, corresponding to the (110) and (101) crystal planes of IrO2, respectively. The catalyst prepared in Example 1 and the commercial iridium black catalyst (Comparative Example 2) exhibit two obvious diffraction peaks at 40.7° and 47.3°, corresponding to the (111) and (200) crystal planes of metallic iridium, respectively, indicating that the bulk structure of the catalyst of the present invention is a single metallic iridium substance.

[0144] As shown in Table 1, EDX element analysis shows that the iridium content in the catalysts of Examples 1, 2, and 3 is between 92 wt% and 95 wt%. Figure 3 It can be seen that Ir 4f 7 / 2 Characteristic peak is taken as example, commercial IrO2 catalyst (comparative example 3) and the catalyst (comparative example 1) prepared by Adams method have corresponding peak positions of 61.50eV and 61.60eV respectively, showing that the valence state of these two catalyst surfaces Ir is+4 valence. Commercial iridium black catalyst (comparative example 2) has peak position of 60.70eV, showing that the surface of this catalyst is 0 valence iridium species. The catalyst of embodiment 1 has peak position at 61.20eV, showing that the valence state of Ir is between+4 valence and 0 valence, and there is intermediate valence iridium oxide species on the surface of this catalyst. The result of EDX elemental analysis and XRD, XPS shows together that catalyst of the present invention is a composite catalyst of iridium and iridium oxide, and bulk is metallic element iridium, and surface is iridium oxide.

[0145] As shown in Table 1, the initial overpotentials of the catalysts prepared in Examples 1, 2, and 3 are superior to those of the catalyst prepared by the Adams method (Comparative Example 1) and the commercial IrO2 catalyst (Comparative Example 3), and are comparable to those of the commercial iridium black catalyst (Comparative Example 2). After stability testing, the increase in the final overpotential of the catalysts prepared in Examples 1, 2, and 3 relative to the initial overpotential is significantly lower than that of the commercial iridium black catalyst (Comparative Example 2), indicating that the catalysts of the present invention have both high activity and high stability.

Claims

1. A composite catalyst of iridium and iridium oxide, characterized in that The XRD spectrum of the catalyst has characteristic peaks of elemental iridium, but no characteristic peaks of iridium dioxide; the Ir 4f 7 / 2 Among the characteristic peaks, there is a characteristic peak of iridium oxide, but no characteristic peak of elemental iridium; the bulk phase of the catalyst is metallic iridium, and the surface is iridium oxide, and the iridium in the iridium oxide is between +4 and 0 valences.

2. The catalyst according to claim 1, characterized in that In the XRD spectrum of the catalyst, there is only a characteristic peak of elemental iridium between 20° and 70°.

3. The catalyst according to claim 1, characterized in that Based on the mass of the catalyst, the iridium content of the catalyst is 92% to 95%.

4. The catalyst according to claim 1, characterized in that The particle size of the catalyst is 1 nm to 10 nm; and the Ir 4f 7 / 2 Among the characteristic peaks, the characteristic peak of iridium oxide shifts toward the direction of low electron binding energy relative to the characteristic peak of iridium dioxide.

5. A method for preparing the composite catalyst of iridium and iridium oxide according to claim 1, comprising: S1, mixing an iridium source and a complexing agent in water to prepare a solution; the complexing agent is selected from one or more organic polyacids and soluble salts thereof; S2, adjust the pH value of the solution to 7-10, and react; S3, removing water to obtain a catalyst precursor; S4, calcining the catalyst precursor under oxygen, and washing it to obtain a product.

6. The preparation method according to claim 5, characterized in that: The complexing agent is selected from one or more of citric acid, tartaric acid and malic acid.

7. The preparation method according to claim 5, characterized in that: The molar ratio of the complexing agent to iridium is 50:(5-50).

8. The preparation method according to claim 5, characterized in that: The calcination temperature is 200° C. to 800° C., and the calcination time is 0.5 h to 6 h.

9. The preparation method according to claim 5, characterized in that: The solvent used for the washing is a mixed solution of ethanol and water, with ethanol accounting for 10% to 95% of the mass of the mixed solution.

10. The preparation method according to claim 5, characterized in that: The iridium source is chloroiridic acid or a soluble salt of chloroiridic acid.

11. The preparation method according to claim 5, characterized in that: The washing step also includes a drying operation, wherein the drying temperature is ≤10°C.

12. Use of the catalyst according to any one of claims 1 to 4 as an oxygen evolution electrocatalyst in electrochemistry.

13. 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 the catalyst according to any one of claims 1 to 4.

14. A method for producing hydrogen by electrolysis of water, characterized in that: The catalyst according to any one of claims 1 to 4 is used, or the proton exchange membrane water electrolyzer according to claim 13 is used.

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