Preparation method and application of a rhenium-doped iridium supported catalyst

Abstract

The application provides a preparation method of a rhenium-doped iridium supported catalyst and application thereof, and relates to the technical field of catalysts. The rhenium source and the iridium source are reduced to iridium-rhenium alloy and supported on nano metal oxides by a one-step method of a solvothermal reaction, with an alcohol solvent as one of solvents and a reducing agent, and with nano metal oxides as carriers. The supported catalyst has high catalytic activity and good stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology and relates to a method for preparing a rhenium-doped iridium supported catalyst and its application. Background Technology

[0002] The most commonly used catalysts for oxygen evolution reaction in water electrolysis to produce hydrogen are iridium oxide and ruthenium oxide, but they have problems such as high cost and insufficient stability. In particular, ruthenium oxide has poor stability in acidic media, while iridium oxide will gradually dissolve and deactivate during long-term operation.

[0003] Supports and alloying are effective methods to improve the intrinsic activity and stability of iridium or ruthenium catalysts. However, how to prepare alloy-supported catalysts with high dispersibility, low particle size and uniform composition through relatively simple methods is one of the challenges in the industry. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a rhenium-doped iridium-supported catalyst and its application.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a rhenium-doped iridium-supported catalyst, comprising the following steps: Metal oxides are dispersed in a mixed solvent consisting of an alcohol solvent and water to obtain a carrier dispersion; Rhenium and iridium sources were added to the carrier dispersion, stirred and dispersed evenly, and a solvation reaction was carried out. After cooling, solid-liquid separation was performed, the solid was collected, washed and dried to obtain a rhenium-doped iridium supported catalyst. The alcohol solvent acts as a reducing agent for the rhenium source and the iridium source during the solvation reaction.

[0007] Preferably, the metal oxide is selected from one or more of titanium dioxide, antimony-doped titanium dioxide, niobium dioxide, tantalum dioxide, and silicon dioxide; The average particle size of the metal oxide is 10-100 nm.

[0008] Preferably, the alcohol solvent is selected from one or more of ethylene glycol, glycerol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, and dipropylene glycol. The volume ratio of the alcohol solvent to the water is 1-4:1.

[0009] Preferably, the concentration of the carrier in the carrier dispersion is 1-10 mmol / L.

[0010] Preferably, the rhenium source is selected from one or more of ammonium perperurate, ammonium chlorate, rhenium trichloride, rhenium pentoxide, and rhenium heptaoxide; The iridium source is selected from one or more of the following: iridium chloroiridic acid, potassium iridium chloroiridate, sodium iridium chloroiridate, iridium trichloride, iridium trifluoride, iridium triiodide, iridium tetrachloride, iridium tetrafluoride, iridium pentafluoride, iridium hexafluoride, iridium acetylacetone, tetrairidium dodecylcarbonyl, ammonium hexachloroiridate, and iridium acetate. The molar ratio of iridium in the iridium source to rhenium in the rhenium source is 1:9-7:3.

[0011] More preferably, the molar ratio of iridium in the iridium source to rhenium in the rhenium source is 3:7-1:1.

[0012] Preferably, the molar ratio of iridium to the metal oxide in the iridium source is 1:10 to 1:1.

[0013] Preferably, the solvothermal reaction temperature is 160-220℃ and the reaction time is 3-12h.

[0014] The application of the rhenium-doped iridium-supported catalyst obtained by the preparation method of the rhenium-doped iridium-supported catalyst according to any of the above embodiments, as a catalyst for hydrogen production by water electrolysis.

[0015] Preferably, the rhenium-doped iridium supported catalyst is a rhenium-iridium alloy coated on the surface of the metal oxide.

[0016] The beneficial effects of this invention are: (1) This invention achieves uniform mixing of rhenium and iridium at the atomic scale through a one-step solvothermal reaction by precisely controlling the proportion of the precursor, forming a rhenium-iridium alloy with precisely controllable composition. Simultaneously, the rhenium-iridium alloy is stably supported on a nanoscale metal oxide support. The process is simple and suitable for industrial-scale production. The supported rhenium-iridium alloy catalyst prepared by this invention has a uniform size distribution (typically 200-300 nm), good dispersibility, a large electrochemical active area, and high electrochemical activity.

[0017] (2) The present invention adjusts the electronic structure of iridium by introducing rhenium, which not only reduces the cost of catalyst, but also optimizes the adsorption energy of reaction intermediates on the catalyst surface, thereby significantly improving the intrinsic activity of oxygen evolution reaction, and has a high resistance to dissolution in acidic environment. Attached Figure Description

[0018] Figure 1 The image shows the SEM image of the supported catalyst obtained in Example 1.

[0019] Figure 2 The image shows a comparison of the iridium 4f XPS spectra of the supported catalyst obtained in Example 1 and the commercial iridium-based catalyst in Comparative Example 1.

[0020] Figure 3The graph shows a comparison of the electrochemical performance of the film-coated electrodes prepared in Examples 1, 2 and Comparative Example 1.

[0021] Figure 4 The voltage change curve is shown for 100 hours of constant current operation after the film electrode was prepared in Example 1. Detailed Implementation

[0022] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0023] On the one hand, this invention proposes a method for preparing a rhenium-doped iridium-supported catalyst, the steps of which include: Metal oxides are dispersed in a mixed solvent consisting of an alcohol solvent and water to obtain a carrier dispersion; Rhenium and iridium sources were added to the carrier dispersion, stirred and dispersed evenly, and a solvation reaction was carried out. After cooling, solid-liquid separation was performed, the solid was collected, washed and dried to obtain a rhenium-doped iridium supported catalyst. Alcohol solvents act as reducing agents for rhenium and iridium sources in solvation reactions.

[0024] This invention uses metal oxide as a support, and disperses the metal oxide, rhenium source, and iridium source together in a mixed solvent to directly carry out a solvothermal reaction. This "one-step" method achieves the reduction and alloying of rhenium and iridium, and the loading of the rhenium-iridium alloy onto the metal oxide support. The supported rhenium-iridium alloy catalyst obtained by this invention has the following characteristics: (1) The introduction of rhenium modulates the electronic structure of iridium, optimizes the adsorption energy of the reaction intermediate on the catalyst surface, and thus significantly improves the intrinsic activity of the catalyst in the oxygen evolution reaction. In 0.5M HClO4 solution, it reaches 10 mA cm⁻¹. -2 The overpotential required for the current density can be as low as below 270mV. (2) The metal oxide support and rhenium-iridium alloy structure enhance the catalyst's resistance to dissolution in acidic environments. In constant current testing, the supported catalyst of this invention can operate stably for more than 100 hours without significant activity decay. (3) By reducing the thickness of the iridium layer through the metal oxide support and reducing the amount of iridium used, and by partially replacing the expensive iridium with relatively inexpensive rhenium, the preparation cost of the catalyst is significantly reduced, resulting in significant economic benefits.

[0025] In this invention, alcohol solvents serve both as reducing agents for rhenium and iridium sources, providing mild and highly controllable reaction conditions, and as components of the mixed solvent, exhibiting good dispersibility for metal oxides, rhenium sources, and iridium sources. Therefore, this invention eliminates the need for additional reducing agents, avoiding potential contamination of the alloy or increased difficulty in the cleaning process that might result from additional reducing agents.

[0026] In this invention, the metal oxides dispersed in the mixed solvent and the rhenium and iridium sources dispersed in the carrier dispersion can both be dispersed by ultrasonication. The ultrasonication temperature can be 10-50℃, and the ultrasonication time can be 5 min-2 h. The rhenium and iridium sources can also be dispersed in the carrier dispersion by stirring. The solid after the solvothermal reaction can be washed several times by alternating washing with anhydrous ethanol and deionized water. After washing, the drying temperature can be 40-80℃, the drying time can be 6-24 h, and the drying environment can be atmospheric pressure or negative pressure.

[0027] In some embodiments, the metal oxide is selected from one or more of titanium dioxide, antimony-doped titanium dioxide, niobium dioxide, tantalum dioxide, and silicon dioxide; The average particle size of the metal oxide is 10-100 nm.

[0028] The metal oxide of the present invention has a certain degree of conductivity. When the rhenium-doped iridium supported catalyst is used for electrocatalysis, the conductive metal oxide can improve the electrocatalytic performance of the rhenium-doped iridium supported catalyst.

[0029] In some embodiments, the alcohol solvent is selected from one or more of ethylene glycol, glycerol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, and dipropylene glycol. The volume ratio of alcohol solvent to water is 1-4:1. For example, the volume ratio of alcohol solvent to water can be 1:1, 2:1, 2.5:1, 3:1, 4:1, etc.

[0030] In some embodiments, the concentration of the carrier in the carrier dispersion is 1-10 mmol / L. For example, the concentration of the carrier in the carrier dispersion can be 1 mmol / L, 2 mmol / L, 3 mmol / L, 4 mmol / L, 5 mmol / L, 6 mmol / L, 7 mmol / L, 8 mmol / L, 9 mmol / L, 10 mmol / L, etc.

[0031] In some embodiments, the rhenium source is selected from one or more of ammonium perrhenate, ammonium chlorate, rhenium trichloride, rhenium pentoxide, and rhenium heptaoxide; The iridium source is selected from one or more of the following: iridium chloroiridic acid, potassium chloroiridate, sodium chloroiridate, iridium trichloride, iridium trifluoride, iridium triiodide, iridium tetrachloride, iridium tetrafluoride, iridium pentafluoride, iridium hexafluoride, iridium acetylacetone, tetrairidium dodecylcarbonyl, ammonium hexachloroiridate, and iridium acetate. The molar ratio of iridium in an iridium source to rhenium in a rhenium source is 1:9 to 7:3. For example, the molar ratio of iridium in an iridium source to rhenium in a rhenium source can be 1:9, 2:8, 3:7, 1:2, 4:6, 3:4, 5:5, 6:4, 2:1, 7:3, etc.

[0032] Furthermore, the molar ratio of iridium in the iridium source to rhenium in the rhenium source is 3:7-1:1.

[0033] In some embodiments, the molar ratio of iridium to metal oxide in the iridium source is 1:10 to 1:1. For example, the molar ratio of iridium to metal oxide in the iridium source can be 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, etc.

[0034] In some embodiments, the solvothermal reaction temperature is 160-220°C, and the reaction time is 3-12 hours. For example, the solvothermal reaction temperature can be 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, etc., and the reaction time can be 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.

[0035] On the other hand, the present invention also proposes an application of the rhenium-doped iridium-supported catalyst obtained by the preparation method of the rhenium-doped iridium-supported catalyst described in any of the above embodiments, for use as a catalyst for hydrogen production by water electrolysis. The rhenium-doped iridium-supported catalyst obtained by the preparation method of the present invention is particularly suitable as a catalyst for the oxygen evolution reaction.

[0036] In some embodiments, the rhenium-doped iridium supported catalyst is a rhenium-iridium alloy coated on the surface of a metal oxide. The molar ratio of rhenium to iridium in the rhenium-iridium alloy can be 1:9-7:3, or a further molar ratio can be 3:7-1:1. The catalyst structure of the present invention, with a rhenium-iridium alloy coated on the surface of a metal oxide, can reduce the amount of iridium used and improve the stability of the catalyst.

[0037] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0038] Example 1 0.2 mmol of nano-titanium dioxide (anatase type, average particle size 40 nm) was added to 100 ml of mixed solvent (the mixed solvent consisted of ethylene glycol and deionized water in a volume ratio of 1:1) and ultrasonically dispersed at 30 °C for 1 hour to obtain a carrier dispersion.

[0039] 0.2 mmol of chloroiridium acid and 0.2 mmol of ammonium perrhenate were added to the above-mentioned support dispersion, and the mixture was magnetically stirred for 30 minutes. The mixture was then transferred to a 500 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE) and sealed. The reactor was placed in an oven and reacted at 180°C for 6 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The black suspension was centrifuged at 10,000 rpm for 10 minutes, and the solid was collected. The solid was washed three times each with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven at 70°C for 10 hours to obtain a black supported catalyst powder, which was an iridium-rhenium alloy supported on a titanium dioxide support.

[0040] In this embodiment, the molar ratio of iridium to nano-titanium dioxide in chloroiridic acid is 1:1, and the molar ratio of iridium in chloroiridic acid to rhenium in ammonium perrhenate is 1:1.

[0041] SEM images of the supported catalyst obtained in this embodiment are attached. Figure 1 As shown, it exhibits good dispersion and a relatively uniform size distribution.

[0042] Example 2 The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the amount of ammonium perrhenate was adjusted so that the molar ratio of iridium in chloroiridium acid to rhenium in ammonium perrhenate was 3:7. The remaining steps remained unchanged. The catalyst obtained in this embodiment is an iridium-rhenium alloy supported on a titanium dioxide carrier.

[0043] Example 3 The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the amount of ammonium perrhenate was adjusted so that the molar ratio of iridium in chloroiridium acid to rhenium in ammonium perrhenate was 1:3. The remaining steps remained unchanged. The catalyst obtained in this embodiment is an iridium-rhenium alloy supported on a titanium dioxide carrier.

[0044] Example 4 The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the amount of ammonium perrhenate was adjusted so that the molar ratio of iridium in chloroiridium acid to rhenium in ammonium perrhenate was 1:9. The remaining steps remained unchanged. The catalyst obtained in this embodiment is an iridium-rhenium alloy supported on a titanium dioxide carrier.

[0045] Comparative Example 1 This comparative example uses a commercially available iridium-based catalyst, Umicore Elyst Ir75 0480 / TiO2 supported catalyst.

[0046] A comparison of the iridium 4f XPS spectra of the supported catalyst obtained in Example 1 and the commercial iridium-based catalyst—Umicore Elyst Ir75 0480 / TiO2 supported catalyst—is attached. Figure 2As shown, Example 1 successfully prepared a rhenium-iridium alloy. Compared to commercial iridium-based catalysts, the 4f XPS characteristic peak of iridium in the catalyst of Example 1 shifts towards a lower binding energy direction. This is attributed to the electron transfer from rhenium to iridium during alloying, which increases the outer electron cloud density of iridium and reduces the average oxidation state of iridium. The low-valence iridium active sites can optimize the adsorption energy of OER intermediates, effectively reducing the reaction overpotential and improving the intrinsic catalytic activity of the catalyst. At the same time, the lower degree of iridium oxidation can inhibit the deep oxidation and dissolution of iridium at high potentials. Combined with the lattice binding effect of the rhenium-iridium alloy, this significantly alleviates the loss of active components and improves the catalyst's cycle stability.

[0047] Figure 3 This is a comparison of the electrochemical performance of the membrane electrodes prepared in Examples 1, 2, and Comparative Example 1. The membrane is an N115 type proton exchange membrane with an effective area of ​​25 cm². 2 The test temperature was 60℃, and the iridium loading was 0.5 mg / cm³. 2 .Depend on Figure 3 It can be seen that the supported catalysts of Examples 1 and 2 have lower voltages at the same current density compared with the commercial iridium-based catalyst of Comparative Example 1, indicating that the supported rhenium-iridium alloy catalyst of the present invention has higher catalytic activity than the supported iridium catalyst (Comparative Example 1).

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that in Example 1, ammonium perrhenate was replaced with an equimolar amount of chloroiridium acid. The remaining steps remained unchanged.

[0049] That is, no rhenium source was added in this comparative example, and the supported catalyst obtained was iridium supported on nano-titanium dioxide.

[0050] Example 5 0.5 mmol of nano-titanium dioxide (anatase type, average particle size 40 nm) was added to 100 ml of mixed solvent (the mixed solvent consisted of 1,3-propanediol and deionized water in a volume ratio of 4:1) and ultrasonically dispersed at 30 °C for 1 hour to obtain a carrier dispersion.

[0051] 0.05 mmol iridium tetrachloride and 0.05 mmol ammonium rhenium chloride were added to the above-mentioned support dispersion, and the mixture was magnetically stirred for 30 minutes. The mixture was then transferred to a 500 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE) and sealed. The reactor was placed in an oven and reacted at 190 °C for 4 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The black suspension was centrifuged at 10,000 rpm for 10 minutes, and the solid was collected. The solid was washed three times each with anhydrous ethanol and deionized water, and then dried in a vacuum drying oven at 70 °C for 10 hours to obtain a black supported catalyst powder, which was a rhenium-iridium alloy supported on a titanium dioxide support.

[0052] In this embodiment, the molar ratio of iridium to nano-titanium dioxide in iridium tetrachloride is 1:10, and the molar ratio of iridium to rhenium in ammonium chlororhenate is 1:1.

[0053] The catalyst obtained in this embodiment is an iridium-rhenium alloy supported on a titanium dioxide carrier.

[0054] Example 6 The difference between this embodiment and Example 5 is that in Example 5, the amount of iridium tetrachloride was adjusted from 0.05 mmol to 0.2 mmol, and the amount of ammonium rhenium chlorate was adjusted from 0.05 mmol to 0.2 mmol. The remaining steps remained unchanged. In this embodiment, the molar ratio of iridium to nano-titanium dioxide in iridium tetrachloride is 1:2.5, and the molar ratio of iridium in iridium tetrachloride to rhenium in ammonium rhenium chlorate is 1:1. The obtained catalyst is an iridium-rhenium alloy supported on a titanium dioxide carrier.

[0055] Electrocatalytic performance test The catalysts to be tested were loaded onto glassy carbon electrodes and subjected to RDE (rotating disk electrode) testing in 0.5 M HClO4 solution at a test value of 10 mA / cm. 2 Overpotential and Tafel slope at current density.

[0056] The catalyst to be tested was fabricated into a membrane electrode assembly (MEA) and assembled into a proton exchange membrane electrolysis test fixture. Electrochemical performance testing was conducted using a pure water circulation supply mode and at a controlled temperature of 60℃. The current was cyclically increased and decreased, ultimately yielding a result of 2 A·cm⁻¹. -2 The average voltage at current density serves as the fundamental electrochemical performance indicator of the membrane electrode.

[0057] The stability test was conducted under constant current conditions with a fixed current density of 2 A·cm. -2 The system operated continuously for 100 hours, with real-time monitoring of the operating voltage changes. Under constant output current conditions, catalyst activity decay caused a continuous increase in operating voltage. Therefore, the lower the voltage increase during the 100-hour electrolysis process, the stronger the catalyst's resistance to decay and dissolution, and the better its cycle stability.

[0058] The working voltage variation curve of Example 1 is shown in the attached figure. Figure 4 As shown, it exhibits good stability.

[0059] The results are shown in Table 1 below.

[0060] Table 1

[0061] As can be seen from the data in Table 1 above, the rhenium-doped iridium supported catalyst of the present invention still has good catalytic activity even when the molar ratio of rhenium in the iridium-rhenium alloy reaches 70% (based on the feed ratio).

[0062] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a rhenium-doped iridium-supported catalyst, characterized in that the steps include... include: Metal oxides are dispersed in a mixed solvent consisting of an alcohol solvent and water to obtain a carrier dispersion; Rhenium and iridium sources were added to the carrier dispersion, stirred and dispersed evenly, and a solvation reaction was carried out. After cooling, solid-liquid separation was performed, the solid was collected, washed and dried to obtain a rhenium-doped iridium supported catalyst. The alcohol solvent acts as a reducing agent for the rhenium source and the iridium source during the solvation reaction.

2. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 1, characterized in that, The metal oxide is selected from one or more of titanium dioxide, antimony-doped titanium dioxide, niobium dioxide, tantalum dioxide, and silicon dioxide; The average particle size of the metal oxide is 10-100 nm.

3. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 1, characterized in that, The alcohol solvent is selected from one or more of ethylene glycol, glycerol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, and dipropylene glycol. The volume ratio of the alcohol solvent to the water is 1-4:

1.

4. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 1, characterized in that, The concentration of the carrier in the carrier dispersion is 1-10 mmol / L.

5. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 1, characterized in that, The rhenium source is selected from one or more of ammonium perperurate, ammonium chlorate, rhenium trichloride, rhenium pentoxide, and rhenium heptaoxide; The iridium source is selected from one or more of the following: iridium chloroiridic acid, potassium iridium chloroiridate, sodium iridium chloroiridate, iridium trichloride, iridium trifluoride, iridium triiodide, iridium tetrachloride, iridium tetrafluoride, iridium pentafluoride, iridium hexafluoride, iridium acetylacetone, tetrairidium dodecylcarbonyl, ammonium hexachloroiridate, and iridium acetate. The molar ratio of iridium in the iridium source to rhenium in the rhenium source is 1:9-7:

3.

6. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 5, characterized in that, The molar ratio of iridium in the iridium source to rhenium in the rhenium source is 3:7-1:

1.

7. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 1, characterized in that, The molar ratio of iridium to the metal oxide in the iridium source is 1:10-1:

1.

8. The method for preparing the rhenium-doped iridium-supported catalyst according to claim 1, characterized in that, The solvothermal reaction temperature is 160-220℃, and the reaction time is 3-12h.

9. The application of a rhenium-doped iridium-supported catalyst obtained by the preparation method of the rhenium-doped iridium-supported catalyst according to any one of claims 1-8, characterized in that, Catalysts used for hydrogen production by water electrolysis.

10. The application according to claim 9, characterized in that, The rhenium-doped iridium supported catalyst is a rhenium-iridium alloy coated on the surface of the metal oxide.

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