CN116005185A - A kind of composite catalyst of iridium and iridium oxide and its preparation method and application - Google Patents

Abstract

The invention provides a composite catalyst of iridium and iridium oxide, and a preparation method and application thereof. The XRD spectrum of the catalyst provided by the invention has characteristic peaks of simple substance iridium and no characteristic peaks of iridium dioxide. The preparation method can avoid using sodium borohydride reducing agent and surfactant, does not generate solid waste and NOx waste gas, and has high atom utilization rate of iridium metal. When used as an anode catalyst for hydrogen production by water electrolysis of a proton exchange membrane, the catalyst provided by the invention has the characteristics of low overpotential, high activity and good stability.

Description

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

technical field

The invention relates to a composite catalyst of iridium and iridium oxide, a preparation method and application thereof.

Background technique

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

Commonly used oxygen evolution catalysts include iridium black and iridium dioxide. Metal iridium resources are scarce and expensive, and the catalytic activity and stability of the existing catalysts are not ideal. The amount of Ir used in the electrolytic cell is generally higher than 2mg/cm ² . The conventional synthesis method of iridium black requires the use of surfactants, sodium borohydride reducing agents or templates, organic solvents, etc., resulting in high preparation costs for iridium black and the generation of a large amount of organic wastewater. For details, see patents CN 103157467B, CN 104437481B, CN 103055853 B, etc. . The main use of 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), which needs to be used in the synthesis process Nitrate, which is dozens of times more than iridium, produces a large amount of harmful substances such as NOx during the roasting process, which requires further tail gas treatment, and at the same time, the treatment of nitrogen-containing wastewater generated by washing needs to be considered.

To sum up, the existing oxygen evolution catalysts have their own shortcomings, and there is a lack of environmentally friendly and economical preparation methods.

Contents of the invention

An object of the present invention is to provide a composite catalyst of iridium and iridium oxide for the hydrogen production anode of proton exchange membrane electrolysis, which can improve the deficiencies of existing iridium black catalysts and iridium oxide catalysts. Another object of the present invention is to provide an environmentally friendly and economical preparation method of the aforementioned catalyst.

In order to achieve the above object, the present invention provides the following technical solutions.

1. A composite catalyst of iridium and iridium oxide. In the XRD spectrum of the catalyst, there are characteristic peaks of elemental iridium and no characteristic peaks of iridium dioxide.

2. The catalyst according to any one of the above, wherein, among the characteristic peaks of Ir 4f _7/2 in the XPS spectrum of the catalyst, there are characteristic peaks of iridium oxide and no characteristic peaks of elemental iridium.

3. According to any of the aforementioned catalysts, wherein, in the Ir 4f _7/2 characteristic peak of the XPS spectrum of the catalyst, there is a characteristic peak of iridium oxide, and there is no characteristic peak of elemental iridium; and relative to the characteristic peak of iridium dioxide , the characteristic peak of iridium oxide shifts to the direction of lower electron binding energy.

4. The catalyst according to any one of the above, wherein the particle size of the catalyst is 1 nm to 10 nm, preferably 1 nm to 5 nm.

5. The catalyst according to any one of the foregoing, wherein, based on the mass of the catalyst, the iridium content of the catalyst is 92% to 95%.

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

S1, mix the iridium source and complexing agent in water to make a solution; the complexing agent is selected from one or more of organic polyacids and soluble salts thereof (preferably selected from C4～C8 organic polyacids and one or more of its soluble salts);

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

S3, removing water to obtain a catalyst precursor;

S4, calcining the catalyst precursor in an oxygen-containing atmosphere, and obtaining a product after washing.

7. The preparation method according to any one 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).

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

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

10. According to any one of the above preparation methods, wherein, based on the mass of the solution of S1, the mass fraction of chloroiridic acid (excluding the mass of crystallization water) is 0.5%-40%.

11. According to any one of the above preparation methods, wherein in S2, a pH regulator is used to adjust the pH value, and the pH regulator is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia water.

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

13. The preparation method according to any one of the above, wherein the calcination temperature is 200°C-800°C, preferably 300°C-500°C; the calcination time is 0.5h-6h, preferably 1h-3h.

14. According to any one of the above preparation methods, wherein the heating rate during calcination is 0.5°C to 10°C, preferably 1°C to 5°C.

15. According to any one of the above preparation methods, wherein the solvent used in the 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.

16. The preparation method according to any one of the above, wherein the oxygen-containing atmosphere is air, oxygen or a mixture of the two.

17. The preparation method according to any one of the above, wherein drying is also included after the washing, and the drying temperature is ≤10°C (preferably ≤0°C, more preferably -30°C～-10°C).

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

19. The application of any one of the aforementioned catalysts in electrochemistry as an oxygen evolution electrocatalyst.

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, characterized in that any of the aforementioned catalysts is used in the anode catalyst layer.

21. A method for electrolyzing water to produce hydrogen, characterized in that any of the aforementioned catalysts or the aforementioned proton exchange membrane water electrolyzer is used.

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

One, the present invention adopts organic polybasic acid and iridium complexation to manufacture precursor after, the method for roasting under oxygen-containing atmosphere, has produced a kind of catalyst of novel structure, and the bulk phase of this catalyst is metal iridium, and the surface is iridium oxide, especially The iridium in the iridium oxide is between +4 valence and 0 valence.

Two, compared with prior art, do not use organic solvent and tensio-active agent in the reaction process of the present invention, do not use oxidants such as sodium nitrate, sodium borohydride and reductant, neither produce solid wastes such as sodium borate or sodium borate , and does not produce NOx exhaust gas, it is a green and environmentally friendly manufacturing method.

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

4. The overpotential of the catalyst of the present invention is lower than that of pure iridium oxide, its mass specific activity is significantly higher than that of pure iridium oxide, and its stability is significantly better than that of iridium black.

Other features and advantages of the present invention will be described in detail in the detailed description section.

Description of drawings

FIG. 1 is a TEM image of the catalyst of Example 1.

Fig. 2 is the XRD pattern of the catalyst of embodiment 1 and each comparative example.

Fig. 3 is the XPS pattern of the catalyst of embodiment 1 and each comparative example.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments, but 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.

In the present invention, any matters or matters not mentioned are directly applicable to those known in the art without any change except for the contents explicitly stated. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the resulting technical solutions or technical ideas are regarded as a part of the original disclosure or record of the present invention, and should not be regarded as It is regarded as a new content that has not been disclosed or expected in this paper, unless those skilled in the art think that the combination is obviously unreasonable.

All the features disclosed in the present invention can be combined arbitrarily, and these combinations should be understood as the content disclosed or recorded in the present invention, unless a person skilled in the art thinks that the combination is obviously unreasonable, it should be regarded as the specific disclosure and content of the present invention. recorded. The numerical points disclosed in this specification not only include the numerical points specifically disclosed in the examples, but also include the endpoints of the numerical ranges in the specification. Any combination of these numerical points shall be regarded as the disclosed or recorded range of the present invention .

For the technical and scientific terms in the present invention, those defined shall prevail, and those not defined shall be understood according to the common meaning in the field.

Unless otherwise specified, the numerical ranges defined in the present invention include the endpoints of the numerical range.

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

In the present invention, optional refers to whether there is or is not, such as A and optional B, means "A without B" or "A and B".

The invention provides a composite catalyst of iridium and iridium oxide. In the XRD spectrogram of the catalyst, there are characteristic peaks of elemental iridium and no characteristic peaks of iridium dioxide.

According to the catalyst of the present invention, in the XRD spectrogram of the catalyst, there are only characteristic peaks of elemental iridium between 20° and 70°.

According to the catalyst of the present invention, among the Ir 4f _7/2 characteristic peaks of the XPS spectrum of the catalyst, there are characteristic peaks of iridium oxide and no characteristic peaks of elemental iridium. According to the catalyst of the present invention, among the Ir 4f _7/2 characteristic peaks of the XPS spectrum of the catalyst, relative to the characteristic peaks of iridium dioxide, the characteristic peaks of iridium oxide shift towards the direction of low electron binding energy. The valence state of the iridium oxide on the surface of the catalyst is between +4 and 0.

According to the catalyst of the present invention, the catalyst has a core-shell structure, and the core is iridium metal.

According to the catalyst of the present invention, its particle size is within 10nm observed by a high-resolution transmission electron microscope (TEM). In some embodiments, the particle size of the catalyst is 1nm-5nm.

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

According to the catalyst of the present invention, the catalyst comprises iridium element, oxygen element and optional carbon element; preferably consists of iridium element, oxygen element and optional carbon element.

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

According to the catalyst of the present invention, based on the mass of the catalyst, the chlorine element content of the catalyst may be 0-0.2%, preferably 0-0.1%, more preferably 0-0.05%, even more preferably 0-0.02%.

According to the catalyst of the present invention, based on the mass of the catalyst, the catalyst may contain no carbon element, or contain about 2% or less of carbon element. These carbon elements have no significant effect on catalyst performance, and it is not necessary to quantify them accurately.

The present invention also provides a preparation method of a composite catalyst of iridium and iridium oxide, comprising:

S1, mixing an iridium source and a complexing agent in water to make a solution; the complexing agent is selected from one or more of organic polybasic acids and their soluble salts;

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 in an oxygen-containing atmosphere, and obtaining a product after washing.

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 soluble salts thereof, more preferably selected from citric acid, tartaric acid and malic acid. one or several.

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 can be with or without water of crystallization.

According to the preparation method of the present invention, in S1, there is no particular limitation on the iridium source concentration of the aqueous solution in S1. Based on the mass of the aqueous solution, the mass fraction of the iridium source may be 0.5%-40%, preferably 20%-40%, more preferably 35%-40%.

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

According to the preparation method of the present invention, in S1, after mixing the iridium source and the complexing agent in water, no heating or heating (preferably heating), no stirring or stirring (preferably stirring) is required. The heating generally keeps the temperature between 40°C and 95°C, preferably between 50°C and 90°C. The stirring time is generally 0.5h-2h, preferably 0.5h-1h.

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 react for a certain period of time; the pH of the solution is preferably adjusted to be alkaline, and the pH of the solution is more preferably adjusted to 8-9. One or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia water can be used to adjust the pH value of the solution.

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

According to the preparation method of the present invention, there is no particular limitation on the method of removing water in the solution in S3, and any known method can be used, such as rotary evaporation and/or vacuum evaporation to remove water in the solution. 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.

According to the preparation method of the present invention, S3 preferably includes the operation of heating and drying the obtained catalyst precursor. The drying temperature of the catalyst precursor may be 80°C-200°C, preferably 100°C-140°C; the drying time of the catalyst precursor may be 8h-40h, preferably 22h-26h.

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

According to the preparation method of the present invention, in S4, firing is carried out under an oxygen-containing atmosphere. The oxygen-containing atmosphere is preferably air, oxygen or a mixture of the two.

According to the method of the present invention, in S4, the roasting temperature is 200°C-800°C, and the roasting time is 0.5h-6h; preferably, the roasting temperature is 300°C-500°C, and the roasting time is 1h-3h

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

When simply using water as a solvent to wash the aforementioned catalyst, it is not easy to centrifuge the catalyst from the water phase. According to the method of the present invention, in S4, the solvent used in the washing is preferably 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 Preferably it is one or more of methanol, ethanol, n-propanol and isopropanol, more preferably ethanol. At this time, it is easy to separate the catalyst by centrifugation, and the rotation speed is 10000r/min for separation, and when the aforementioned alcohol-water mixed solution is used as the washing solvent, the centrifugation time can be 1min-50min, preferably 5min-15min.

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

According to the preparation method of the present invention, in S4, when it is detected that there is no chloride ion in the solvent after washing or the pH value is neutral, the washing can be ended. The washing operation is preferably terminated by detecting the absence of chloride ions in the solvent after washing.

According to the preparation method of the present invention, after sufficient washing, the catalyst does not contain or substantially does not contain chlorine.

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 dried at -30°C to -10°C; the drying time may be 8h to 40h, preferably 22h to 26h.

The present invention also provides a composite catalyst of iridium and iridium oxide, which is prepared by any of the aforementioned methods. Other features of the catalyst are the same as those described above, which will not be repeated in the present invention.

The present invention further provides the application of any one of the aforementioned catalysts in electrochemistry as an oxygen evolution electrocatalyst.

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 any of the aforementioned catalysts is used in the anode catalyst layer .

The present invention further provides a method for electrolyzing water to produce hydrogen, using any of the aforementioned catalysts or the aforementioned proton exchange membrane water electrolyzer.

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

Reagents, Instruments and Tests

The raw materials used in the examples are all obtained from commercial sources, and are analytically pure unless otherwise specified. Wherein, the raw material of chloroiridic acid is liquid, and the mass fraction of iridium is 35%. For the convenience of taking, it is prepared into a solution with a concentration of 0.182mol/L for use, and can also be prepared with a higher concentration solution for use.

The instrument, method and condition of TEM analysis: the model of the high resolution transmission electron microscope (HRTEM) that the present invention adopts is JEM-2100 (HRTEM) (Japan Electronics Co., Ltd.), and the high resolution transmission electron microscope test condition is: accelerating voltage is 200kV.

Instruments, methods and conditions of EDX elemental analysis: EDX elemental analysis is measured by the EDS energy spectrometer equipped with Hitachi S 4800 scanning electron microscope in Japan, the accelerating voltage is 20kv, WD=15mm.

Instruments, methods and conditions for XPS analysis: the present invention detects elements on the surface of the material through an X-ray photoelectron spectrum analyzer (XPS). The X-ray photoelectron spectrum analyzer used is the ESCALab220i-XL type X-ray electron spectrometer equipped with AvantageV5.926 software produced by VG Scientifc. The X-ray photoelectron spectrum analysis test conditions are: the excitation source is monochromatic A1Kα X-ray, The power is 330W, and the basic vacuum is 3×10 ^-9 mbar during analysis and test. In addition, the electron binding energy was corrected with the C1s peak (284.3 eV) of elemental carbon.

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

The model of the electrochemical workstation is PARSTAT3000A-DX, and the model of the rotating disc electrode is 636A. A three-electrode system is adopted, the reference electrode is a saturated calomel electrode, the counter electrode is a platinum sheet, and the working electrode is a glassy carbon electrode. The electrolyte used under acidic conditions was 0.5M H ₂ SO ₄ solution. The catalyst to be tested was uniformly dispersed in a mixed solution of isopropanol, water and Nafion by ultrasonic, dropped onto the surface of a glassy carbon electrode, and dried naturally to obtain a working electrode. The loading capacity of the catalyst was 0.38 mg·cm ^-2 . The test temperature was 25°C, the solution was saturated with oxygen for 30 minutes before the test, the rotation speed was 2500 rpm, the scanning range of the linear polarization curve was 1.2V-1.5V (vs RHE), and the scanning rate was 5mV/s. The stability test scan interval is 1.26V～1.56V (vs RHE), the scan rate is 50mV/s, and the number of scan cycles is 10,000.

Example 1

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

(2) Add a certain amount of Na ₂ CO ₃ solution dropwise to the above solution, so that the pH value of the solution is between 8 and 9, and stir and react at 90°C for 3 hours;

(3) The above solution was rotatably evaporated at 70° C., and the water was evaporated to obtain a catalyst precursor;

(4) Place the catalyst precursor in an oven and dry at 120°C for 24h;

(5) Take out the dried catalyst precursor, grind it after cooling, put it into a porcelain boat, put oxygen into the muffle furnace, and raise the temperature to 400°C at a heating rate of 2°C/min under an oxygen atmosphere. Roasting, the roasting time is 2h;

(6) Take out the roasted solid, cool to room temperature, add a mixed solution of water and ethanol, the volume ratio of water and ethanol is 1:1, ultrasonically wash, the ultrasonic temperature is room temperature, the ultrasonic time is 10min, and then centrifuged , the centrifugation speed is 10000rpm, and the time is 10min. After centrifugation, pour off the supernatant, and continue to repeat the above steps until no chloride ions are detected by using silver nitrate, and the washing process ends;

(7) Put the washed solid into a freeze-drying box for freeze-drying at a temperature of -10° C. for 24 hours to finally obtain a catalyst.

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.

For the catalyst in this example, see FIG. 1 for the TEM spectrum; FIG. 2 for the XRD spectrum; and FIG. 3 for the XPS spectrum.

Preparation example 2

(1) Take 30mL (5.46mmol) of chloroiridic acid aqueous solution, add 1.58g of malic acid, and stir at 90°C for 0.5h, so that the malic acid and chloroiridic acid are fully mixed;

(2) A certain amount of Na ₂ CO ₃ solution was added dropwise to the above solution so that the pH value of the solution was between 8 and 9, and the reaction was stirred at 90°C for 3 hours;

(3) The above solution was rotatably evaporated at 70° C., and the water was spin-dried to obtain a catalyst precursor;

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

(5) Take out the dried catalyst precursor, grind it after cooling, put it into a porcelain boat, put oxygen into the muffle furnace, and raise the temperature to 400°C at a heating rate of 2°C/min under an oxygen atmosphere, and keep 2h;

(6) Take out the roasted solid, cool to room temperature, add a certain amount of mixed solution of water and ethanol, the volume ratio of water and ethanol is 1:1, ultrasonically wash, the ultrasonic temperature is room temperature, and the ultrasonic time is 10min, then Carry out centrifugation, the centrifugation speed is 10000rpm, the time is 10min, pour off the supernatant after centrifugation, continue to repeat the above steps, until no chloride ion is detected by using silver nitrate, the washing process ends;

(7) Put the washed solid into a freeze-drying box for freeze-drying at a temperature of -10° C. for 24 hours to finally obtain a catalyst.

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.

The catalyst of this embodiment has the same features as shown in Example 1 in Figure 1 in TEM spectrum; the same in Example 1 in Figure 2 in XRD spectrum; and the same in Example 1 in XPS spectrum in Figure 3.

Preparation example 3

(1) Take 30mL (5.46mmol) of chloroiridic acid aqueous solution, add 1.58g of tartaric acid, and stir at 90°C for 0.5h, so that the tartaric acid and chloroiridic acid are fully mixed;

(2) A certain amount of sodium carbonate solution was added dropwise to the above solution, so that the pH value of the solution was between 8 and 9, and stirred and reacted at 90° C. for 3 hours;

(3) The above solution was rotatably evaporated at 70° C., and the water was spin-dried to obtain a catalyst precursor;

(4) Place the catalyst precursor in an oven and dry at 120°C for 24h;

(5) Take out the dried catalyst precursor, grind it after cooling, put it into a porcelain boat, put oxygen into the muffle furnace, and raise the temperature to 400°C at a heating rate of 2°C/min under an oxygen atmosphere, and keep 2h;

(6) Take out the roasted solid, cool to room temperature, add a certain amount of mixed solution of water and ethanol, the volume ratio of water and ethanol is 1:1, ultrasonically wash, the ultrasonic temperature is room temperature, and the ultrasonic time is 10min, then Carry out centrifugation, the centrifugation speed is 10000rpm, the time is 10min, pour off the supernatant after centrifugation, continue to repeat the above steps, until no chloride ion is detected by using silver nitrate, the washing process ends;

(7) Put the washed solid into a freeze-drying box for freeze-drying at a temperature of -10° C. for 24 hours to finally obtain a catalyst.

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.

The catalyst of this embodiment has the same features as shown in Example 1 in Figure 1 in TEM spectrum; the same in Example 1 in Figure 2 in XRD spectrum; and the same in Example 1 in XPS spectrum in Figure 3.

Comparative example 1 (Adams method)

(1) Get chloroiridic acid aqueous solution 30mL (5.46mmol);

(2) Add 110 mL of 4.7 mol/L NaNO ₃ solution and stir at room temperature for 2 h;

(3) The above solution was rotatably evaporated at 70° C., and the water was spin-dried to obtain a catalyst precursor;

(4) Place the catalyst precursor in a blast drying oven and dry at 120°C for 24h;

(5) Take out the dried catalyst precursor, put it into a porcelain boat and place it in a muffle furnace, raise the temperature to 500°C at a heating rate of 2°C/min, and keep it for 2h;

(6) Take out the roasted solid, cool to room temperature, add a certain amount of mixed solution of water and ethanol, the volume ratio of water and ethanol is 1:1, ultrasonically wash, the ultrasonic temperature is room temperature, and the ultrasonic time is 10min, then Carry out centrifugation, the centrifugation speed is 10000rpm, the time is 10min, pour off the supernatant after centrifugation, continue to repeat the above steps, until no chloride ion is detected by using silver nitrate, the washing process ends;

(7) Put the washed solid into a freeze-drying box for freeze-drying at a temperature of -10° C. for 24 hours to finally obtain a catalyst.

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.

For the catalyst of this comparative example, the XRD spectrum is shown in Figure 2; the XPS spectrum is shown in Figure 3.

Comparative example 2 commercial iridium black catalyst

Purchased from Alfa Company, the product number is 047150.

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.

For the catalyst of this comparative example, the XRD spectrum is shown in Figure 2; the XPS spectrum is shown in Figure 3.

Comparative Example 3 Commercial IrO _Catalyst

Purchased from sigma aldrich company, the product number is 206237.

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.

For the catalyst of this comparative example, the XRD spectrum is shown in Figure 2; the XPS spectrum is shown in Figure 3.

Table 1

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[Initial overpotential/mV@10mA/cm²]]> 228 230 231 280 232 260 <![CDATA[Final overpotential/mV@10mA/cm²]]> 247 252 249 302 348 279

As can be seen from Figure 1, the lighter colored region of the catalyst prepared in Example 1 (the darker part is because the catalyst in this region is not completely dispersed, and the catalyst is stacked together) shows that the catalyst particle size is between 1 and 5 nm. As can be seen from Fig. 2, commercial _IrO Catalyst (comparative example 3) and the catalyst (comparative example 1) prepared by Adams method appear two obvious diffraction peaks at 28.0 ° and 34.7 °, correspond to _IrO respectively (110) and (101 )Planes. The catalyst prepared in Example 1 and the commercial iridium black catalyst (comparative example 2) have two obvious diffraction peaks at 40.7 ° and 47.3 °, corresponding to the (111) and (200) crystal planes of metal iridium respectively, indicating that the catalyst body of the present invention The phase structure is metal iridium simple substance.

It can be seen from Table 1 that EDX elemental analysis shows that the content of iridium element in the catalysts of Examples 1, 2 and 3 is between 92wt% and 95wt%. As can be seen from Fig. 3, take Ir 4f _7/2 characteristic peak as example, commercial _IrO catalyzer (comparative example 3) and the corresponding peak position of the catalyst (comparative example 1) prepared by Adams method are respectively 61.50eV and 61.60eV, show The valence state of Ir on the surface of these two catalysts is +4. The peak position of the commercial iridium black catalyst (comparative example 2) is 60.70eV, indicating that the surface of the catalyst is a zero-valent iridium species. The peak position of the catalyst in Example 1 is at 61.20eV, indicating that the valence state of Ir is between +4 and 0, and there is an intermediate valence iridium oxide species on the surface of the catalyst. EDX elemental analysis results together with XRD and XPS results show that the catalyst of the present invention is a composite catalyst of iridium and iridium oxide, the bulk phase is metal elemental iridium, and the surface is iridium oxide.

As can be seen from Table 1, _the catalyst initial overpotential prepared by embodiment 1,2,3 is all better than the catalyst (comparative example 1) and commercial IrO prepared by Adams method Catalyst (comparative example 3), suitable with commercial iridium black catalyst (comparative example 3) Scale 2). After the stability test, the final overpotential of the catalyst prepared in Examples 1, 2, and 3 was significantly lower than that of the commercial iridium black catalyst (comparative example 2) compared to the initial overpotential increase, indicating that the catalyst of the present invention has both high Activity and high stability.

Claims (15)

1. A composite catalyst of iridium and iridium oxide is characterized in that the XRD spectrum of the catalyst has characteristic peaks of simple substance iridium and no characteristic peaks of iridium dioxide.

2. The catalyst according to claim 1, wherein the XPS spectrum of the catalyst is Ir 4f _7/2 The characteristic peak has characteristic peaks of iridium oxide, and no characteristic peak of simple substance iridium.

3. The catalyst according to claim 1, wherein the iridium element content of the catalyst is 92% to 95% based on the mass of the catalyst.

4. The catalyst according to claim 1, wherein the particle size of the catalyst is 1nm to 10nm.

5. A method for preparing a composite catalyst of iridium and iridium oxide, 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 of organic polyacid and soluble salt thereof;

s2, regulating the pH value of the solution to 7-10, and reacting;

s3, removing water to obtain a catalyst precursor;

s4, roasting the catalyst precursor in an oxygen-containing atmosphere, and washing to obtain a product.

6. The method according to claim 5, wherein the complexing agent is one or more selected from the group consisting of citric acid, tartaric acid and malic acid.

7. The method of claim 5, wherein the molar ratio of complexing agent to iridium is 50: (5-50).

8. The method according to claim 5, wherein the baking temperature is 200 to 800 ℃ and the baking time is 0.5 to 6 hours.

9. The preparation method according to claim 5, wherein the solvent used for washing is a mixed solution of ethanol and water, and ethanol accounts for 10% -95% of the mass of the mixed solution.

10. The method of claim 5, wherein the iridium source is chloroiridic acid or a soluble salt of chloroiridic acid.

11. The process according to claim 5, wherein the washing is followed by drying at a temperature of 10 ℃.

12. A composite catalyst of iridium and iridium oxide, characterized in that it is produced by the method according to any one of claims 5 to 11.

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

14. A proton exchange membrane water electrolyser comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer and an anode diffusion layer, wherein the catalyst of any one of claims 1 to 4 and claim 12 is used in the anode catalyst layer.

15. A method for producing hydrogen by electrolysis of water, characterized in that the catalyst according to any one of claims 1 to 4 and claim 12 is used, or the proton exchange membrane water electrolyzer according to claim 14 is used.

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