Preparation method of iridium tin catalyst and its product and application

Abstract

The application provides a preparation method of an iridium-tin catalyst, a product and an application thereof. The method comprises the following steps: preparing an aqueous solution of an iridium source and a tin source under the action of a complexing agent and in an alkaline condition; removing water to obtain a catalyst precursor; and calcining under an oxygen-containing atmosphere, and then performing post-treatment to obtain the product. The preparation process of the application does not use raw materials such as organic solvents, sodium borohydride and surfactants, and does not emit harmful gases such as NOx during calcination, and is lower in cost and more environmentally friendly; and the atomic utilization rate of the transition metal can reach 100%. In the catalyst, Sn is more uniformly doped, and the catalyst is not phase-separated at a high Ir / Sn ratio or a low Ir / Sn ratio; when the catalyst is used as an anode catalyst for water electrolysis of a proton exchange membrane, the catalyst has higher catalytic activity than a commercial iridium oxide catalyst, and the cost is significantly reduced.

Description

Technical Field

[0001] The present invention relates to a preparation method of an iridium-tin catalyst, a product thereof and applications thereof, and in particular to a preparation method of an iridium-tin composite oxide catalyst, a product thereof and applications of the product in proton exchange membrane water electrolysis hydrogen production technology. Background Art

[0002] Compared with alkaline water electrolysis technology, proton exchange membrane (PEM) water electrolysis hydrogen production technology has the advantages of fast response speed, high current density, wide working load range, and high hydrogen purity. In particular, it has unparalleled advantages in utilizing renewable energy for power generation and is the main way to obtain green hydrogen in the future. The anode oxygen evolution reaction is the rate-controlling step of the PEM water electrolysis reaction, so the anode catalyst is the key material in the proton exchange membrane water electrolysis hydrogen production technology. At present, the anode of commercial PEM water electrolysis devices uses iridium oxide or iridium black catalyst. Metallic iridium resources are scarce and expensive, and the Ir dosage of the electrolyzer is generally higher than 2 mg / cm 2 Therefore, reducing the amount of anode iridium is one of the important breakthroughs for the large-scale application of PEM electrolysis water. Existing literature shows that adding cheaper metal oxides such as titanium oxide, tin oxide, tantalum oxide, ruthenium oxide, etc. to iridium oxide is an effective way to reduce the amount of anode iridium. However, how to maintain the original catalytic activity and stability of iridium oxide remains a technical difficulty that needs to be solved in this field. Existing preparation methods include Adams method (Preparation and characterization of nanocrystalline Ir x Sn 1-xO2 electrocatalytic powders, Materials Chemistry and Physics, 2005, 94, 226-232.), triblock surfactant-assisted sodium borohydride coupled hydrolysis method (CN103880094 A; Triblock polymer mediated synthesis of Ir-Sn oxide electrocatalysts for oxygen evolution reaction, Journal of Power Sources, 2016, 325, 15024), etc. The catalyst prepared by the Adams method is prone to phase separation structure when the Ir / Sn ratio is high or low, and the prepared catalyst particles are large and the electrochemical activity is not high. In addition, the Adams method uses more sodium nitrate, which releases NOx during calcination. The catalyst prepared by the sodium borohydride coupled hydrolysis method also has the problem of phase separation when the Ir / Sn ratio is high or low. In addition, both of the above-mentioned preparation methods will result in a certain amount of iridium metal loss, and the sodium borohydride coupled hydrolysis method also uses a relatively expensive triblock surfactant and sodium borohydride reducing agent. Summary of the Invention

[0003] The present invention aims to provide a method for preparing an iridium-tin catalyst that can be easily and efficiently doped with tin oxide without causing phase separation even at high or low Ir / Sn ratios. Another object of the present invention, further to achieving the aforementioned objectives, is to provide an iridium-tin catalyst with excellent performance for use as anode in proton exchange membrane water electrolyzers, maintaining catalytic activity and stability even at low Ir / Sn ratios.

[0004] In order to achieve the above objectives, the present invention provides the following technical solutions.

[0005] 1. A method for preparing an iridium-tin catalyst, comprising:

[0006] S1, a step of preparing an aqueous solution of an iridium source and a tin source under alkaline conditions in the presence of a complexing agent; the complexing agent is a C4-C8 organic polyacid and a soluble salt thereof;

[0007] S2, a step of removing water to obtain an iridium tin catalyst precursor;

[0008] S3, calcining the iridium tin catalyst precursor in an oxygen-containing atmosphere, and washing it to obtain a product.

[0009] 2. According to any of the above preparation methods, it is characterized in that said S1 comprises:

[0010] S1-1, mixing an iridium source and a first complexing agent to prepare a first aqueous solution;

[0011] S1-2, mixing a tin source and a second complexing agent to prepare a second aqueous solution;

[0012] S1-3, adjusting the pH of the first aqueous solution and the second aqueous solution to be alkaline, and then mixing the two;

[0013] S1-4, controlling the pH value of the mixed aqueous solution in S1-3 to be alkaline, reacting;

[0014] The first complexing agent and the second complexing agent are independently selected from C4-C8 organic polyacids and soluble salts thereof.

[0015] 3. A preparation method according to any of the above, characterized in that the iridium source is chloroiridic acid or a soluble salt thereof; and the tin source is a soluble stannate.

[0016] 4. The preparation method according to any of the above, characterized in that the first complexing agent and the second complexing agent are each independently selected from citric acid, tartaric acid or malic acid.

[0017] 5. The preparation method according to any of the above, characterized in that the molar ratio of the first complexing agent to iridium is (1-4):1; the molar ratio of the second complexing agent to tin is (1-4):1.

[0018] 6. A preparation method according to any of the above, characterized in that the molar ratio of the complexing agent to the total molar amount of iridium and tin is (1-4):1.

[0019] 7. A method according to any of the above-mentioned preparations, characterized in that the total molar concentration of iridium and tin in any of the above-mentioned solutions is 0.1M to 1M.

[0020] 8. The preparation method according to any of the above, characterized in that, in any of the above steps, a pH regulator is used to adjust the pH value of the solution, and the pH regulator is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia water.

[0021] 9. A preparation method according to any of the above, characterized in that the solvent used for washing is a mixed solution of alcohol and water, and the alcohol is selected from one or more of methanol, ethanol, n-propanol and isopropanol.

[0022] 10. A preparation method according to any of the above, characterized in that the solvent used for washing is a mixed solution of alcohol and water, and the alcohol accounts for 10% to 95% by mass of the mixed solution, preferably 30% to 60%.

[0023] 11. A preparation method according to any of the above, characterized in that, in S1-4, the reaction temperature is 35°C to 95°C, preferably 50°C to 90°C; and the reaction time is 0.5h to 6h, preferably 2h to 4h.

[0024] 12. A preparation method according to any of the above, characterized in that the calcination temperature is 350°C to 550°C, preferably 380°C to 450°C; and the calcination time is 1 hour to 3 hours, preferably 1.5 hours to 2 hours.

[0025] 13. The preparation method according to any of the above-mentioned methods is characterized in that a drying operation is further included after washing, and the drying temperature is less than 10°C, preferably less than 0°C, and more preferably -30°C to -10°C.

[0026] 14. The preparation method according to any one of the above, characterized in that water is removed by distillation under reduced pressure and / or rotary evaporation.

[0027] 15. An iridium-tin catalyst, characterized in that it is prepared by any of the above methods and is an amorphous solid.

[0028] 16. An iridium tin catalyst, characterized in that the catalyst has the formula Ir x Sn 1-x O2 or Ir x Sn 1-x The schematic chemical composition represented by O2·nH2O; wherein x is 0.3-0.4, 0.4-0.6 or 0.6-0.8; the catalyst is an amorphous solid.

[0029] 17. A catalyst according to any preceding claim, characterised in that the surface of the catalyst is enriched in iridium relative to the bulk of the catalyst.

[0030] 18. The catalyst according to any one of the preceding claims, characterized in that the ratio of the molar fraction of iridium as analyzed by XPS to the molar fraction of iridium as analyzed by XRF is 1.54 to 1.97 based on the total molar amount of iridium and tin.

[0031] 19. A catalyst according to any of the preceding claims, characterized in that the average pore size of the catalyst is 7 nm to 16 nm, preferably 9 nm to 13 nm.

[0032] 20. Use of any of the above catalysts as an oxygen evolution electrocatalyst in electrochemistry.

[0033] 21. 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.

[0034] Compared with the prior art, the present invention can achieve the following beneficial technical effects.

[0035] 1. In the method of the present invention, the reaction process does not use raw materials such as organic solvents, sodium borohydride and surfactants, and no harmful gases such as NOx are emitted during roasting, which reduces the manufacturing cost and makes the process more environmentally friendly.

[0036] Second, the method of the present invention has a high product yield and the utilization rate of transition metal atoms can reach 100%.

[0037] 3. In the catalyst of the present invention, Sn doping is more uniform and there is no phase separation even at a high Ir / Sn ratio or a low Ir / Sn ratio.

[0038] Fourth, the bulk structure of the catalyst of the present invention is amorphous. When used as an anode catalyst for proton exchange membrane water electrolysis to produce hydrogen, it has higher catalytic activity than commercial iridium oxide catalysts and significantly reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Attachment Figure 1 This is the high-resolution transmission electron microscopy image of Example 2.

[0040] Attachment Figure 2 The following are XRD patterns of various embodiments and comparative examples.

[0041] Other features and advantages of the present invention will be described in detail in the detailed description section. DETAILED DESCRIPTION

[0042] 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.

[0043] 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.

[0044] 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 combination 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.

[0045] 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.

[0046] Unless otherwise specified, the numerical ranges defined herein include the endpoints of the numerical ranges.

[0047] In the present invention, unless otherwise specified, the term "soluble" means soluble in water.

[0048] The present invention provides a method for preparing an iridium-tin catalyst, comprising:

[0049] S1, a step of preparing an aqueous solution of an iridium source and a tin source under alkaline conditions under the action of a complexing agent; the complexing agent is a C4-C8 organic polyacid and a soluble salt thereof;

[0050] S2, a step of removing water to obtain an iridium tin catalyst precursor;

[0051] S3, calcining the iridium tin catalyst precursor in an oxygen-containing atmosphere, and washing it to obtain a product.

[0052] In the prior art, it is difficult to manufacture iridium-tin composite oxides with uniform bulk structure, especially when Ir / Sn is high or low, which easily leads to phase separation problems. After diligent research, the inventors found that, on the one hand, this problem is related to the process of manufacturing the precursor, especially when the precursor is synthesized in the aqueous phase, precipitation is easily generated, leading to phase separation problems; on the other hand, it is related to the structure, composition and roasting process of the precursor. It has been found that different precursor structures and compositions will lead to different bulk structures of iridium-tin composite oxides. For example, the bulk structure of iridium-tin composite oxides manufactured by the gel method of ethylene glycol is crystalline. The inventors found that using organic polyacids as complexing agents to manufacture catalyst precursors under alkaline conditions in the aqueous phase can, on the one hand, avoid the precipitation problem that is easy to occur in aqueous phase synthesis, and on the other hand, can also manufacture iridium-tin composite oxides with an amorphous bulk structure, thereby completing the present invention.

[0053] According to the method of the present invention, a preferred embodiment includes:

[0054] S1-1, mixing an iridium source and a first complexing agent to prepare a first solution;

[0055] S1-2, mixing a tin source and a second complexing agent to prepare a second solution;

[0056] S1-3, adjusting the pH values ​​of the first solution and the second solution to be alkaline, and then mixing the two;

[0057] S1-4, controlling the pH value of the mixed solution in S1-3 to be alkaline, and reacting;

[0058] The first complexing agent and the second complexing agent are independently selected from C4-C8 organic polyacids and soluble salts thereof.

[0059] According to the method of the present invention, any existing iridium source and tin source can be used, as long as they can be converted into an aqueous solution under the action of the complexing agent. The iridium source is preferably chloroiridic acid or a soluble salt thereof; the chloroiridic acid and its soluble salt may or may not contain water of crystallization, generally containing water of crystallization, such as compounds represented by the formula H2IrCl6·6H2O or (NH4)2IrCl6·6H2O. The tin source is preferably a soluble stannate; the soluble stannate may or may not contain water of crystallization, generally containing water of crystallization, such as compounds represented by the formula Na2SnO3·3H2O or K2SnO3·3H2O.

[0060] According to the method of the present invention, the complexing agent is a C4-C8 organic polyacid and its soluble salt. In the aforementioned preferred embodiment, the first complexing agent and the second complexing agent are each independently selected from C4-C8 organic polyacids and their soluble salts. The present invention has no further restrictions on the C4-C8 organic polyacids and their soluble salts. From the perspective of industrial application, the present invention prefers those C4-C8 organic polyacids and their soluble salts that are lower in cost and more abundant in source, such as citric acid, tartaric acid, malic acid, and their soluble salts.

[0061] According to the method of the present invention, in the aqueous solution, the molar ratio of the complexing agent to the total molar amount of iridium and tin is 1:1 to 4:1. For the aforementioned preferred embodiment, the molar ratio of the first complexing agent to iridium is 1:1 to 4:1; and the molar ratio of the second complexing agent to tin is 1:1 to 4:1.

[0062] According to the method of the present invention, in the aqueous solution, the total molar concentration of iridium and tin in any solution is 0.1M to 1M. For the aforementioned preferred embodiment, the molar concentration of iridium in the first solution is 0.1M to 1M; and the molar concentration of tin in the second solution is 0.1M to 1M.

[0063] According to the method of the present invention, in said S1, an aqueous solution of an iridium source and a tin source is prepared under the action of a complexing agent. If the complexing agent of the present invention is not used, the aqueous solution of the iridium source and / or the tin source will show obvious precipitation.

[0064] According to the method of the present invention, in any step, a pH regulator can be used to adjust and control the pH value of the aqueous solution as needed. The pH regulator can be selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonia.

[0065] According to the method of the present invention, in S1, an aqueous solution of an iridium source and a tin source is prepared under alkaline conditions. The "alkaline conditions" mentioned above are crucial to the performance of the iridium-tin catalyst. In S1, the pH is preferably adjusted to 8-9. Generally, the aqueous solution of the iridium source and the tin source is reacted at 35-95°C for 0.5-6 hours, preferably at 50-90°C for 2-4 hours.

[0066] According to the aforementioned preferred embodiment, in S1-3, the pH values ​​of the first aqueous solution and the second aqueous solution are preferably adjusted to 8-9, respectively.

[0067] According to the aforementioned preferred embodiment, in S1-4, the pH value of the mixed aqueous solution is preferably controlled to be 8-9.

[0068] According to the method of the present invention, in S2, water is removed by reduced pressure distillation and / or rotary evaporation.

[0069] According to the method of the present invention, the calcination temperature is 350° C. to 550° C., preferably 380° C. to 450° C.; the calcination time is 1 h to 3 h, preferably 1.5 h to 2 h.

[0070] According to the method of the present invention, the calcination is preferably carried out in an oxygen-containing atmosphere, more preferably in an air or oxygen atmosphere. Calcination under nitrogen has an adverse effect on the catalytic effect of the catalyst.

[0071] According to the method of the present invention, the solvent used for washing is a mixed solution of alcohol and water. The alcohol-water mixture is used to facilitate separation of the catalyst by centrifugation. Washing with water alone is difficult to separate the catalyst by centrifugation. Any alcohol that meets the aforementioned objectives can be used in the present invention. The alcohol is preferably one or more of methanol, ethanol, n-propanol, and isopropanol. The alcohol may comprise 10% to 95% by mass of the mixed solution, preferably 30% to 60%.

[0072] Generally, the catalyst should be washed until the pH of the liquid phase after washing is neutral or no chloride ions are detected.

[0073] The method of the present invention preferably includes a drying operation after washing. The drying temperature is less than 10°C, preferably less than 0°C, and more preferably between -30°C and -10°C. The prior art generally involves drying above room temperature. However, the present inventors have found that if washing with water is used, it is difficult to completely separate the catalyst by centrifugation. If washing is performed partially or entirely with an organic solvent (such as the aforementioned alcohol), drying above room temperature can degrade the catalytic performance of the catalyst.

[0074] The present invention also provides an iridium tin catalyst prepared by any of the above methods, wherein the catalyst is an amorphous solid. The catalyst may have the formula Irx Sn 1-x O2 or Ir x Sn 1-x Schematic chemical composition represented by O2·nH2O; wherein x is 0.3-0.4, 0.4-0.6 or 0.6-0.8.

[0075] The present invention provides an iridium tin catalyst, characterized in that the catalyst has the formula Ir x Sn 1-x O2 or Ir x Sn 1-x The schematic chemical composition represented by O2·nH2O; wherein x is 0.3-0.4, 0.4-0.6 or 0.6-0.8; the catalyst is an amorphous solid.

[0076] It is known in the art that the catalyst may sometimes contain a certain amount of water (for example, before drying), and thus may have the formula "Ir x Sn 1-x O2·nH2O”; after drying to remove water, it can have the formula “Ir x Sn 1-x Since the presence of water does not substantially affect the subsequent performance of the catalyst, the present invention believes that there is no need to limit the amount of water.

[0077] According to the iridium tin catalyst of the present invention, the surface of the catalyst is rich in iridium relative to the bulk phase of the catalyst. The so-called surface rich in iridium means that the iridium content on the catalyst surface is higher than the iridium content in the bulk phase of the catalyst.

[0078] According to the iridium-tin catalyst of the present invention, based on the total molar amount of iridium and tin, the ratio of the molar fraction of iridium analyzed by XPS to the molar fraction of iridium analyzed by XRF is 1.54-1.97.

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

[0080] 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.

[0081] Reagents, Instruments and Tests

[0082] The raw materials used in the examples are all obtained through commercial channels, and are all analytical pure unless otherwise specified. Among them, the chloroiridic acid raw material is in liquid form, and the mass fraction of Ir is 35%. For the convenience of taking, it is prepared into a solution with a mass concentration of 0.182 mol / L for use, and a solution with a higher concentration can also be prepared for use.

[0083] The model of the X-ray fluorescence spectrometer (XRF) is Rigaku 3013 X-ray fluorescence spectrometer, and the X-ray fluorescence spectrum analysis test conditions are: the scanning time is 100 s, and the atmosphere is air.

[0084] The present application detects the elements on the surface of the material by X-ray photoelectron spectrometer (XPS). The X-ray photoelectron spectrometer used is ESCALab220i-XL type ray electron spectrometer produced by VG Scientifc company and equipped with Avantage V5.926 software, and the X-ray photoelectron spectrum analysis test conditions are: the excitation source is monochromatic Al Kα X-ray, the power is 330 W, and the base vacuum during analysis and test is 3×10 -9 mbar. In addition, the electron binding energy is corrected by the C1s peak (284.3 eV) of elemental carbon.

[0085] BET test method: in the present application, the pore structure properties of the sample are determined by Quantachrome AS-6B type analyzer, the specific surface area and pore volume of the catalyst are obtained by Brunauer-Emmett-Taller (BET) method, and the pore distribution curve is calculated according to Barrett-Joyner-Halenda (BJH) method on the desorption curve.

[0086] The high-resolution transmission electron microscope (HRTEM) used in the present application is JEM-2100 (HRTEM) (Japan Electron Corporation), and the high-resolution transmission electron microscope test conditions are: the acceleration voltage is 200 kV.

[0087] X-ray diffraction analysis (XRD) is carried out on X-ray diffractometer of XRD-6000 of Japan Shimadzu, and the test conditions include: tube voltage 40 kV, tube current 40 mA, Cu target Kα radiation, and 2θ scanning range 5° to 80°.

[0088] 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 passed through the solution for 30 min before the test to saturate the solution with oxygen. The rotation speed was 2500 rpm. The scanning range of the linear polarization curve was 1.2 V to 1.5 V (vs RHE) at a scanning rate of 5 mV / s.

[0089] Example 1 Catalyst Ir 0.4 Sn 0.6 Preparation of O2

[0090] (1) Take 20 mL (3.64 mmol) of chloroiridic acid aqueous solution, weigh 1.05 g of citric acid, and stir at 90°C to fully mix the citric acid and chloroiridic acid;

[0091] (2) 1.456 g of Na2SnO3·3H2O (5.46 mmol) was dissolved in 10 mL of water, and 1.57 g of citric acid was dissolved in 5 mL of water. The citric acid solution was added dropwise to the Na2SnO3 solution. The final pH value was about 3, and then the pH value was adjusted to 8 with Na2CO3 solution.

[0092] (3) Add a certain amount of Na2CO3 to the solution in step 1 to adjust the solution pH to 8, add the solution in step 2, stir at 90°C for half an hour, then add a certain amount of sodium carbonate solution to control the solution pH to between 8 and 9, and stir for another 3 hours. At the end of the process, observe that there is no precipitation at the bottom of the bottle and the solution is transparent under strong light;

[0093] (4) After cooling, spin-dry at 70°C and dry in a 120°C oven overnight;

[0094] (5) After the catalyst is removed and cooled, it is ground and placed flat on a porcelain boat. In an oxygen atmosphere, the temperature is increased to 400°C at a heating rate of 2°C / min and then maintained for 2 h.

[0095] (6) Cool to room temperature, wash with a mixed solvent of ethanol and water in a mass ratio of 1:1, centrifuge three times (pH test paper shows neutral), and place the centrifuge tube with the catalyst in a freeze drying oven (-10°C) to dry overnight.

[0096] 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.

[0097] Example 2 Catalyst Ir 0.6 Sn 0.4 Preparation of O2

[0098] (1) Take 20 mL (3.64 mmol) of chloroiridic acid aqueous solution, weigh 1.05 g of citric acid, and stir at 90°C to fully mix the citric acid and chloroiridic acid;

[0099] (2) 0.648 g of Na2SnO3·3H2O (2.43 mmol) was dissolved in 10 mL of water, and 0.7 g of citric acid was dissolved in 5 mL of water. The citric acid solution was added dropwise to the Na2SnO3 solution. The final pH value was about 3, and then the pH value was adjusted to 8 with Na2CO3 solution.

[0100] (3) Add a certain amount of Na2CO3 to the solution in step 1 to adjust the solution pH to 8, add the solution in step 2, stir at 90°C for half an hour, then add a certain amount of sodium carbonate solution to control the solution pH to between 8 and 9, and stir for another 3 hours. At the end of the process, observe that there is no precipitation at the bottom of the bottle and the solution is transparent under strong light;

[0101] (4) After cooling, spin-dry at 70°C and dry in a 120°C oven overnight;

[0102] (5) After the catalyst is removed and cooled, it is ground and placed flat on a porcelain boat. In an oxygen atmosphere, the temperature is increased to 400°C at a rate of 2°C / min and maintained for 2 h.

[0103] (6) Cool to room temperature, wash with a mixed solvent of ethanol and water in a mass ratio of 1:1, centrifuge three times (pH test paper shows neutral), and place the centrifuge tube with the catalyst in a freeze drying oven (-10°C) to dry overnight.

[0104] 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.

[0105] Example 3 Catalyst Ir 0.8 Sn 0.2 Preparation of O2

[0106] (1) Take 30 mL (5.46 mmol) of chloroiridic acid aqueous solution, weigh 1.58 g of citric acid, and stir at 90°C to fully mix the citric acid and chloroiridic acid;

[0107] (2) 0.363 g of Na2SnO3·3H2O (1.36 mmol) was dissolved in 5 mL of water. 0.39 g of citric acid was dissolved in 5 mL of water. The citric acid solution was added dropwise to the Na2SnO3 solution. The final pH value was about 3. The pH value was then adjusted to 8 with Na2CO3 solution.

[0108] (3) Add a certain amount of Na2CO3 to the solution in step 1 to adjust the solution pH to 8, add the solution in step 2, stir at 90°C for half an hour, then add a certain amount of sodium carbonate solution to control the solution pH to between 8 and 9, and stir for another 3 hours. At the end of the process, observe that there is no precipitation at the bottom of the bottle and the solution is transparent under strong light;

[0109] (4) After cooling, spin-dry at 70°C and dry in a 120°C oven overnight;

[0110] (5) After the catalyst is removed and cooled, it is ground and placed flat on a porcelain boat. In an oxygen atmosphere, the temperature is increased to 400°C at a rate of 2°C / min and maintained for 2 h.

[0111] (6) Cool to room temperature, wash with a mixed solvent of ethanol and water in a mass ratio of 1:1, centrifuge three times (pH test paper shows neutral), and place the centrifuge tube with the catalyst in a freeze drying oven (-10°C) to dry overnight.

[0112] 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.

[0113] Example 4 Catalyst Ir 0.4 Sn 0.6 Preparation of O2

[0114] (1) Take 20 mL (3.64 mmol) of chloroiridic acid aqueous solution, weigh 1.05 g of citric acid, and stir at 90°C to fully mix the citric acid and chloroiridic acid;

[0115] (2) 1.456 g of Na2SnO3·3H2O (5.46 mmol) was dissolved in 10 mL of water, and 1.57 g of citric acid was dissolved in 5 mL of water. The citric acid solution was added dropwise to the Na2SnO3 solution. The final pH value was about 3, and then the pH value was adjusted to 8 with Na2CO3 solution.

[0116] (3) Add a certain amount of Na2CO3 to the solution in step 1 to adjust the solution pH to 8, add the solution in step 2, stir at 90°C for half an hour, then add a certain amount of sodium carbonate solution to control the solution pH to between 8 and 9, and stir for another 3 hours. At the end of the process, observe that there is no precipitation at the bottom of the bottle and the solution is transparent under strong light;

[0117] (4) After cooling, spin-dry at 70°C and dry in a 120°C oven overnight;

[0118] (5) After the catalyst is removed and cooled, it is ground and placed flat on a porcelain boat. In an oxygen atmosphere, the temperature is increased to 400°C at a rate of 2°C / min and maintained for 2 h.

[0119] (6) cooling to room temperature, washing with mixed solvent of ethanol and water with mass ratio of 1:1, centrifuging 3 times (pH test paper is neutral), centrifuge tube with catalyst is put into the blast drying oven to dry overnight (40℃).

[0120] The instruments and conditions for electrochemical performance test and characterization of the catalyst are as described above, and the results are shown in Table 1.

[0121] Example 5 Catalyst Ir 0.6 Sn 0.4 Preparation of O2

[0122] (1) Take 20 mL of aqueous chloroiridic acid (3.64 mmol), weigh 1.05 g of citric acid, and stir at 90℃ to mix the citric acid and chloroiridic acid thoroughly;

[0123] (2) 0.648 g of Na2SnO3·3H2O (2.43 mmol) is dissolved in 10 mL of water, and 0.7 g of citric acid is dissolved in 5 mL of water. The citric acid solution is added dropwise into the Na2SnO3 solution, and the final pH value is about 3. Then, Na2CO3 solution is used to adjust the pH value to 8;

[0124] (3) A certain amount of Na2CO3 is added to the solution in step 1 to adjust the pH value of the solution to 8. The solution in step 2 is added, and after stirring at 90℃ for half an hour, a certain amount of Na2CO3 solution is added to control the pH value of the solution between 8 and 9. Then, the solution is stirred for another 3 hours. At the end of the reaction, no precipitate is observed at the bottom of the bottle, and the solution is transparent under strong light;

[0125] (4) After cooling, the solution is spin-dried at 70℃, and then put into a 120℃ oven to dry overnight;

[0126] (5) After cooling, the catalyst is ground and placed flat in a porcelain boat. The temperature is raised to 400℃ at a rate of 2℃ / min under oxygen atmosphere, and maintained for 2 hours;

[0127] (6) cooling to room temperature, washing with mixed solvent of ethanol and water with mass ratio of 1:1, centrifuging 3 times (pH test paper is neutral), centrifuge tube with catalyst is put into the blast drying oven to dry overnight (40℃).

[0128] The instruments and conditions for electrochemical performance test and characterization of the catalyst are as described above, and the results are shown in Table 1.

[0129] Comparative Example 1 Commercial iridium oxide catalyst

[0130] Purchased from sigma aldrich company, item number 206237.

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

[0132] Table 1

[0133]

[0134] Depend on Figure 1 It can be seen that the particle size of the catalyst of the present invention is about 3nm to 5nm. Figure 2 It can be seen that the commercial IrO2 catalyst has two obvious diffraction peaks at 28.0° and 34.7°, corresponding to the (110) and (101) crystal planes of IrO2, respectively. x Sn 1-x The O2 catalyst only has two amorphous small bulges near 34° and 40°.

[0135] Table 1 shows the XRF, XPS, BET and electrochemical activity test results of each embodiment and comparative example. The XRF results show that the Ir / Sn molar ratio in the prepared catalyst is basically consistent with the raw material input ratio, which together with the manufacturing process of the present invention shows that the transition metal atom utilization rate of the preparation method can reach 100%. The XPS results show that the prepared Ir x Sn 1-x The molar ratio of Ir / Sn on the surface of O2 catalyst is higher than that in the bulk phase, forming an Ir-rich surface. From the overpotential results, it can be seen that the prepared Ir x Sn 1-x The O2 catalysts showed better oxygen evolution activity than commercial IrO2 catalysts. The drying method also had a certain impact on the performance of the catalysts. When dried at room temperature or above, the overpotential increased by 13mV to 15mV compared to freeze-drying.

Claims

1. A method for preparing an iridium-tin catalyst, comprising: S1, a step of preparing an aqueous solution of an iridium source and a tin source under alkaline conditions under the action of a complexing agent; The complexing agent is a C4-C8 organic polyacid and its soluble salt; S2, a step of removing water to obtain an iridium tin catalyst precursor; S3, calcining the iridium tin catalyst precursor in an oxygen-containing atmosphere, and washing it to obtain a product.

2. The preparation method according to claim 1, characterized in that: The S1 includes: S1-1, mixing an iridium source and a first complexing agent to prepare a first aqueous solution; S1-2, mixing a tin source and a second complexing agent to prepare a second aqueous solution; S1-3, adjusting the pH values ​​of the first solution and the second solution to be alkaline, and then mixing the two; S1-4, controlling the pH value of the mixed solution in S1-3 to be alkaline, and reacting; The first complexing agent and the second complexing agent are independently selected from C4-C8 organic polyacids and soluble salts thereof.

3. The preparation method according to claim 1, characterized in that: The iridium source is chloroiridic acid or a soluble salt thereof; the tin source is a soluble stannate.

4. The preparation method according to claim 2, characterized in that: The first complexing agent and the second complexing agent are each independently selected from citric acid, tartaric acid or malic acid.

5. The preparation method according to claim 2, characterized in that: The molar ratio of the first complexing agent to iridium is (1-4):1; the molar ratio of the second complexing agent to tin is (1-4):

1.

6. The preparation method according to claim 1, characterized in that: The calcination temperature is 350° C. to 550° C., and the calcination time is 1 hour to 3 hours.

7. The preparation method according to claim 1, 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.

8. The preparation method according to claim 1, characterized in that: The washing step includes a drying operation, wherein the drying temperature is less than 0°C.

9. An iridium-tin catalyst, characterized in that Prepared by the method described in any one of claims 1 to 8, the catalyst is an amorphous solid.

10. An iridium-tin catalyst, characterized in that The catalyst has the formula Ir x Sn 1-x O2 or Ir x Sn 1-x The schematic chemical composition represented by O2·nH2O; wherein x is 0.3-0.4, 0.4-0.6 or 0.6-0.8; the catalyst is an amorphous solid.

11. The catalyst according to claim 10, characterized in that Based on the total molar amount of iridium and tin, the ratio of the mole fraction of iridium analyzed by XPS to the mole fraction of iridium analyzed by XRF is 1.54 to 1.

97.

12. The catalyst according to claim 10, characterized in that The average pore diameter of the catalyst is 7nm-16nm.

13. Use of the catalyst according to any one of claims 9 to 12 as an oxygen evolution electrocatalyst in electrochemistry.

14. 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 9 to 12.

Images