Fluorinated ruthenium oxide catalyst as well as preparation method and application thereof

Abstract

The invention provides a fluorinated ruthenium oxide catalyst and a preparation method and application thereof.The preparation method of the fluorinated ruthenium oxide catalyst comprises the steps that S1, ruthenium precursor salt and villiaumite are dissolved in an alcohol solvent, and a mixed solution is obtained; s2, drying the mixed solution to remove the alcohol solvent to obtain a catalyst precursor; and S3, adding the catalyst precursor into molten nitrate for reaction, and after the reaction is completed, washing and drying the obtained product to obtain the fluorinated ruthenium oxide catalyst. The prepared fluorinated ruthenium oxide electrocatalyst shows excellent electrocatalytic activity in an acidic electrolyzed water anode oxygen evolution reaction, and also has relatively good long-term working stability.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytic water oxygen evolution catalysts, and specifically relates to a fluorinated ruthenium oxide catalyst and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane (PEM) water electrolysis is an efficient hydrogen production technology, in which the catalytic efficiency and durability of the electrocatalytic oxygen evolution reaction (OER) are key factors affecting the overall water electrolysis performance. OER is a multi-electron transfer process, usually accompanied by a high reaction energy barrier, which makes the process particularly slow in acidic environments, severely limiting the efficiency of hydrogen production from water electrolysis.

[0003] In order to accelerate the OER reaction, the selection and optimization of catalysts have become the focus of research. x Iridium (Ir)-based catalysts are widely used in the OER process because of their long durability and relatively good activity, but their low reserves and high cost seriously hinder their large-scale application. Ru is considered to be an alternative material to Ir-based catalysts due to its high intrinsic acidic OER activity, high reserves, and price about one order of magnitude lower than Ir. However, Ru-based OER catalysts, especially RuO x , due to the over-oxidation of Ru atoms to volatile RuO4 or soluble RuO5 at high OER voltage (>1.6 V). 2− Materials usually have poor solubility resistance. This leads to direct demetallization of the Ru active sites on the surface, severe loss of catalyst structure and active sites, decreased catalyst activity, and limited service life of only a few dozen hours, making it difficult to meet the needs of long-term and stable industrial applications.

[0004] In recent years, researchers have been doping other elements to regulate the electronic structure of RuO2 catalysts to enhance their catalytic activity and durability. For example, Guo Shaojun's team introduced Ln elements through dpf orbital hybridization to achieve RuO x Benefiting from the optimized Ru-O covalency, Er-RuO xThe catalyst was selected and showed high catalytic stability (Li, L., Zhang, G., Zhou, C. et al. Lanthanide-regulating Ru-O covalency optimizes acidic oxygen evolution electrocatalysis. Nat Commun 15, 4974(2024)). Wei Zidong's research group proposed a silicon-decorated interstitial RuO2 catalyst that showed high activity and stability for acidic OER. Si was incorporated into the RuO2 lattice, which reduced the energy barrier of RDS by optimizing the adsorption strength of *OOH intermediates on active Ru sites, thereby improving OER performance (Ping, X., Liu, Y., Zheng, L. et al. Locking thelattice oxygen in RuO2 to stabilize highly active Ru sites in acidic wateroxidation. Nat Commun 15, 2501 (2024)). Wang Haotian's team reported a Ni-stabilized ruthenium dioxide (Ni-RuO2) catalyst. The Ni dopant can stabilize the surface Ru and subsurface oxygen, which plays a key role in improving the durability of OER. The catalyst has high activity and durability in acidic OER and is used for PEM water electrolysis (Wu, ZY., Chen, FY., Li, B. et al. Non-iridium-based electrocatalyst for durable acidic oxygen evolution reaction in proton exchange membrane water electrolysis. Nat. Mater.22, 100–108 (2023)). The Chinese patent application with publication number CN117802528A proposes a manganese-doped ruthenium oxide nanocatalyst and its preparation method and application, which is used for the anode extreme oxygen evolution reaction of acidic water electrolysis to produce hydrogen, showing excellent activity and certain stability; however, the preparation method is complicated and requires multiple steps of treatment, and even needs to be carried out under hydrothermal conditions, which is not conducive to large-scale industrial production. For example, the Chinese patent application with publication number CN118558340A proposes a fluorine-doped ruthenium dioxide catalyst and its preparation method and application in proton exchange membrane water electrolysis, which first dissolves ruthenium salt and fluoride salt in water and mixes them ultrasonically to obtain a mixed solution, and the mixed solution is stirred and mixed with nitrate and then freeze-dried to obtain a catalyst precursor; the catalyst precursor is calcined and post-treated to obtain a fluorine-doped ruthenium dioxide catalyst. This method is time-consuming, the fluorine doping amount is difficult to ensure, and the activity and stability of the catalyst are not high.

[0005] In summary, although the existing technical solutions have demonstrated the potential of doping methods in improving the electrochemical performance of RuO2, the preparation process usually faces problems such as complex operation, low doping efficiency, and poor doping uniformity, which makes it difficult to meet the requirements of efficient, uniform, and low-cost industrial preparation. Therefore, it is urgent to develop an efficient and simple preparation method for doping ruthenium dioxide so that it can be widely used in PEM water electrolysis systems. Summary of the invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention proposes a fluorinated ruthenium oxide catalyst and its preparation method and application. The prepared fluorinated ruthenium oxide electrocatalyst exhibits excellent electrocatalytic activity in the anode oxygen evolution reaction in acidic water electrolysis, and has good long-term working stability.

[0007] The present invention is achieved through the following technical solutions: The present invention provides a method for preparing a fluorinated ruthenium oxide catalyst, comprising: S1, dissolving a ruthenium precursor salt and a fluoride salt in an alcohol solvent to obtain a mixed solution; S2, drying the mixed solution to remove the alcohol solvent to obtain a catalyst precursor; S3, adding the catalyst precursor into the molten nitrate to react, and after the reaction is completed, washing and drying the obtained product to obtain a fluorinated ruthenium oxide catalyst.

[0008] Preferably, in S1, the ruthenium precursor salt is one or more of ruthenium acetylacetonate, ruthenium trichloride, ruthenium acetate, potassium pentachlororuthenate, hexaammineruthenium chloride and ammonium hexachlororuthenate.

[0009] Preferably, in S1, the fluoride salt is one or more of sodium fluoride, lithium fluoride, potassium fluoride, ammonium fluoride and calcium fluoride.

[0010] Preferably, in S1, the alcohol solvent is one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol and glycerol.

[0011] Preferably, in S1, the molar ratio of ruthenium to fluorine in the mixed solution is 1:(1-30).

[0012] Preferably, in S2, the drying temperature is 40-100°C, and the drying time is 1-10 h.

[0013] Preferably, in S3, the reaction temperature is 200-500°C, and the reaction time is 1-10 min.

[0014] Preferably, in S3, the nitrate is one or more of potassium nitrate, sodium nitrate, calcium nitrate, lithium nitrate, magnesium nitrate and sodium nitrite.

[0015] The present invention also provides a fluorinated ruthenium oxide catalyst obtained by the preparation method described above.

[0016] The present invention also provides the use of the fluorinated ruthenium oxide catalyst as an OER catalyst in proton exchange membrane water electrolysis.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts the molten salt method for fluorine doping, and the required reaction time is very short, which greatly shortens the reaction time, and the molten salt can be recycled, reducing the production cost, and is suitable for large-scale industrial production. In addition, the reaction temperature of the molten salt method of the present invention is relatively low, which avoids the complex gas equipment requirements and high-temperature operation process in the high-temperature gas phase fluorination method, makes the preparation process simpler and easier, and reduces equipment investment and operating costs. At the same time, the present invention adopts the molten salt method to make the combination of fluorine in the RuO2 lattice more stable. This stable doping structure effectively regulates the RuO2 electronic structure, improves the catalytic activity and long-term stability of the RuO2 catalyst, and solves the problems of poor activity, low stability and catalytic efficiency of existing electrolytic water oxygen evolution catalysts in the reaction process that cannot meet industrial applications. The fluorine-doped ruthenium dioxide catalyst prepared by the present invention shows a lower OER overpotential in acidic electrolytic water. The catalyst is used in a proton exchange membrane electrolysis water system to greatly improve the hydrogen production efficiency and extend the service life of the catalyst, meeting the performance requirements for oxygen evolution catalysts in efficient electrolytic water systems.

[0018] Furthermore, the molar ratio of ruthenium to fluorine has a certain influence on the catalyst performance. As the fluorine doping amount increases, the catalytic performance of the catalyst first increases and then decreases. The present invention optimizes the appropriate molar ratio of ruthenium to fluorine so that the obtained catalyst has better catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The X-ray diffraction pattern of the fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention; Figure 2 A high-resolution transmission electron microscopy image of the fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention; Figure 3 This is a selected area electron diffraction pattern of the fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention; Figure 4 This is the element mapping distribution diagram of the fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention; Figure 5 The linear sweep voltammetry test results of different fluorine-doped ruthenium oxide catalysts prepared in the examples of the present invention and the catalysts prepared in the comparative examples in 0.5 mol / L sulfuric acid solution are shown; Figure 6 The fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention has a conductivity of 10 mAcm in a 0.5 mol / L sulfuric acid solution. -2 Chronopotentiometry test results during current density electrolysis; Figure 7 This is a graph showing the polarization curve test results of the fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention and the commercial ruthenium oxide catalyst based on proton exchange membrane water electrolysis. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0022] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0023] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0024] The basic content of the technical solution of the present invention is: to synthesize a fluorinated ruthenium dioxide catalyst by a molten salt method and use it as an anode catalyst in acidic water electrolysis, thereby reducing the overpotential of the electrocatalytic oxygen evolution reaction and achieving low-voltage and long-term stable water electrolysis to produce hydrogen, while simplifying the preparation method of the doped ruthenium dioxide catalyst and greatly shortening the preparation time.

[0025] The preparation method of the fluorinated ruthenium oxide catalyst of the present invention comprises: S1, dissolving a ruthenium precursor salt and a fluoride salt in an alcohol solvent to obtain a mixed solution; S2, drying the mixed solution to remove the alcohol solvent to obtain a catalyst precursor; S3, adding the catalyst precursor into the molten nitrate to react, and after the reaction is completed, washing and drying the obtained product to obtain a fluorinated ruthenium oxide catalyst.

[0026] Because the present invention adopts alcohol solvent to dissolve the mixed ruthenium precursor salt and fluoride salt, the alcohol solvent can be dried and removed in a short time to obtain the catalyst precursor. Also, because the present invention adopts the molten salt method to prepare the fluorinated ruthenium oxide catalyst, the reaction time can be shortened to a very short time. That is, the present invention adopts the molten salt method for fluorine doping, and the required reaction time is very short, which greatly shortens the reaction time, and the molten salt can be recycled, which reduces the production cost and is suitable for large-scale industrial production.

[0027] Specifically, in the embodiment of the present invention, the drying temperature of the mixed solution is 40-100°C, and the drying time is 1-10 h; more preferably, the drying temperature is 80°C, and the drying time is 4 h.

[0028] Specifically, in the embodiment of the present invention, the catalyst precursor is reacted in molten nitrate at a temperature of 200-500° C. for a reaction time of 1-10 min; more preferably, the reaction temperature is 250-400° C. for a reaction time of 5 min.

[0029] It can be seen from this that the preparation method of the fluorinated ruthenium oxide catalyst of the present invention can be completed in just a few hours, which greatly shortens the time required for preparation and is more conducive to industrial realization.

[0030] At the same time, according to the experimental results of the present invention, it can be found that the fluorinated ruthenium oxide catalyst prepared by the molten salt method of the present invention has better catalytic activity than the fluorinated ruthenium oxide catalyst prepared by other methods, which may be because the fluorine doping process using the molten salt method makes the combination of fluorine in the RuO2 lattice more stable and uniform. This stable doping structure effectively regulates the electronic structure of RuO2 and improves the activity and long-term stability of the RuO2 catalyst.

[0031] In some specific embodiments of the present invention, the ruthenium precursor salt is one or more of ruthenium acetylacetonate, ruthenium trichloride, ruthenium acetate, potassium pentachlororuthenate, hexaammineruthenium chloride and ammonium hexachlororuthenate, more preferably ruthenium trichloride.

[0032] In some specific embodiments of the present invention, the fluoride salt is one or more of sodium fluoride, lithium fluoride, potassium fluoride, ammonium fluoride and calcium fluoride, more preferably ammonium fluoride.

[0033] In some specific embodiments of the present invention, the alcohol solvent is one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol and glycerol, more preferably ethanol.

[0034] In the present invention, the molar ratio of the ruthenium precursor salt to the fluorine salt is 1:(1-30), preferably 1:(5-15), and more preferably 1:10, based on the moles of ruthenium and fluorine.

[0035] In some specific embodiments of the present invention, the nitrate is one or more of potassium nitrate, sodium nitrate, calcium nitrate, lithium nitrate, magnesium nitrate and sodium nitrite, preferably a mixture of two or more nitrates, such as potassium nitrate and sodium nitrate. A mixture of two or more nitrates has a lower melting point and can reduce the temperature required for melting.

[0036] When potassium nitrate and sodium nitrate are used, the molar ratio of potassium nitrate to sodium nitrate is 1:(1-5), more preferably 1:2.

[0037] In S3 of the present invention, after the reaction is completed, the obtained product is first washed with water and then washed with ethanol. After washing, the drying temperature is 40-100°C and the drying time is 2-12 hours; more preferably, the drying temperature is 60°C and the drying time is 4 hours.

[0038] The fluorinated ruthenium oxide catalyst prepared by the present invention can be used as a PEM water electrolysis anode catalyst for PEM water electrolysis to produce hydrogen.

[0039] Example 1 Weigh 3.03 g potassium nitrate and 5.1 g sodium nitrate, grind and mix them in a mortar, and transfer the mixed salt to an alumina crucible. Place the crucible in a muffle furnace and heat it to 350 °C at a heating rate of 5 °C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst (referred to as 5F-RuO2).

[0040] The fluorinated ruthenium oxide catalyst prepared by the above method was characterized, and the results are shown in Figures 1 to 4 .like Figure 1 As shown, the physical phase of the fluorinated ruthenium oxide catalyst prepared in this example is consistent with rutile phase ruthenium dioxide. Figure 2 and Figure 3 As shown in FIG. 1 , the high-resolution transmission electron microscope image and selected area electron diffraction image of the fluorinated ruthenium oxide catalyst prepared in this example show that the catalyst is a polycrystalline material composed of many tiny nanoparticles. Figure 4 As shown, in the fluorinated ruthenium oxide catalyst prepared in this embodiment, the fluorine element is evenly distributed in the ruthenium oxide.

[0041] Example 2 The difference between this embodiment and embodiment 1 is that the molar ratio of ruthenium and fluorine elements is adjusted to 1:5. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt is transferred to an alumina crucible after mixing; the crucible is placed in a muffle furnace and heated to 350°C at a heating rate of 5°C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 188 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst (denoted as 2.5F-RuO2).

[0042] Example 3 The difference between this embodiment and embodiment 1 is that the molar ratio of ruthenium and fluorine elements is adjusted to 1:15. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350°C at a heating rate of 5°C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 566 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst (recorded as 7.5F-RuO2).

[0043] Example 4 The difference between this embodiment and embodiment 1 is that the calcination temperature is adjusted to 300°C. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 300°C at a heating rate of 5°C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0044] Example 5 The difference between this embodiment and embodiment 1 is that the nitrate used for adjustment is only sodium nitrate. Specifically: 8.13 g of sodium nitrate is weighed and ground in a mortar. The ground sodium nitrate is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350°C at a heating rate of 5°C / min. The sodium nitrate is melted and used for subsequent reactions. 216 mg of ruthenium trichloride and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to molten sodium nitrate, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven and dried at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0045] Example 6 The difference between this embodiment and embodiment 1 is that the calcination time is adjusted to 1 min. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350 ° C at a heating rate of 5 ° C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 60 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0046] Example 7 The difference between this embodiment and embodiment 1 is that the calcination time is adjusted to 10 min. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350 ° C at a heating rate of 5 ° C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 60 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven and dried at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0047] Example 8 The difference between this embodiment and embodiment 1 is that the ruthenium precursor is adjusted to ruthenium acetylacetonate. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350 ° C at a heating rate of 5 ° C / min. After the mixed salt is melted, it is ready for subsequent reactions. 398 mg of ruthenium acetylacetonate and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 60 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven and dried at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0048] Example 9 The difference between this embodiment and embodiment 1 is that the solvent used to adjust the mixed solution is methanol. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350 ° C at a heating rate of 5 ° C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride and 378 mg of ammonium fluoride were weighed and dissolved in 5 mL of methanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven and dried at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0049] Example 10 The difference between this embodiment and embodiment 1 is that the fluoride salt is adjusted to sodium fluoride, specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, put in a mortar and grind and mix, and the mixed salt is transferred to an alumina crucible after mixing; the crucible is placed in a muffle furnace and heated to 350 °C at a heating rate of 5 °C / min, and the mixed salt is melted for subsequent reactions. 216 mg of ruthenium trichloride and 420 mg of sodium fluoride were weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a mixed solution; the mixed solution after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 60 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven and dried at 60 °C for 4 h to obtain a fluorinated ruthenium oxide catalyst.

[0050] Comparative Example 1 216 mg of ruthenium trichloride and 24 mg of sodium fluoride were weighed and dissolved in 5 mL of deionized water, and ultrasonically mixed for 30 min to obtain a mixed solution; 3.03 g of potassium nitrate and 5.1 g of sodium nitrate were added to the mixed solution, stirred at 500 rpm for 60 min, and freeze-dried for 48 h to obtain a catalyst precursor; the catalyst precursor was placed in a tube furnace and calcined in an air atmosphere at a heating rate of 5 °C / min, a calcination temperature of 350 °C, and a calcination time of 5 min. After naturally cooling to room temperature, the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample. Finally, the sample was placed in a vacuum oven and dried at 60 °C for 8 h to obtain a fluorinated ruthenium oxide catalyst (denoted as F-RuO2).

[0051] Comparative Example 2 The difference between this comparative example and Example 1 is that the molar ratio of ruthenium and fluorine elements is adjusted to 1:0, that is, no fluoride salt is added. Specifically: 3.03 g potassium nitrate and 5.1 g sodium nitrate are weighed, placed in a mortar and ground and mixed, and the mixed salt obtained after mixing is transferred to an alumina crucible; the crucible is placed in a muffle furnace and heated to 350°C at a heating rate of 5°C / min. After the mixed salt is melted, it is ready for subsequent reactions. 216 mg of ruthenium trichloride was weighed and dissolved in 5 mL of anhydrous ethanol, and ultrasonically mixed for 60 min to obtain a dispersion; the dispersion after ultrasonication was placed in an oven and dried at 80 °C for 4 h to obtain a catalyst precursor; the catalyst precursor was added to the molten mixed salt, reacted at 350 °C for 5 min, and then the crucible was taken out of the muffle furnace and cooled to room temperature; the cooled sample was washed with 1500 mL of water to completely remove the remaining nitrate, and then washed with 15 mL of anhydrous ethanol to remove the water remaining in the sample, and finally the sample was placed in a vacuum oven at 60 °C for 4 h to obtain a fluorine-free ruthenium oxide catalyst (denoted as M-RuO2).

[0052] Preparation of working electrode: Weigh 5 mg of catalyst and 2 mg of Vulcan XC-72 carbon black, evenly disperse them in 735 μL of isopropanol, 245 μL of deionized water and 10 μL of Nafion (Dupont, 5wt%) solution, mix and ultrasonicate for 1 h to obtain catalyst slurry. Take 10 μL of catalyst slurry with a microinjector and drop it on the glassy carbon electrode. The loading amount is 0.255 mg / cm 2 , and dried at room temperature to obtain a working electrode.

[0053] Electrochemical performance test: The glassy carbon electrode coated with the catalyst was used as the working electrode, the platinum electrode was used as the counter electrode, the reference electrode was a saturated mercurous sulfate electrode, and the electrolyte was a 0.5 mol / L sulfuric acid solution. After the assembly was completed, the electrochemical performance of the catalyst was tested.

[0054] The electrochemical performance test results are shown in Figure 5 , Figure 6 and Figure 7 .like Figure 5As shown, it can be seen that compared with the undoped fluorine-containing M-RuO2 in Comparative Example 2, the fluorinated ruthenium oxide catalysts prepared in Examples 1-3 of the present invention have better OER catalytic activity, indicating that fluorine doping can improve the OER catalytic activity of ruthenium oxide catalysts. Compared with the 2.5F-RuO2 in Example 2 and the 7.5F-RuO2 in Example 3, the 5F-RuO2 catalyst in Example 1 exhibits the best oxygen evolution reaction performance, indicating that the molar ratio of ruthenium to fluorine has a certain effect on the catalyst performance. With the increase of the fluorine doping amount, the catalytic performance of the catalyst first increases and then decreases. When the molar ratio of ruthenium to fluorine is 1:10, the catalyst performance is optimal. The 5F-RuO2 catalyst in Example 1 has excellent oxygen evolution reaction performance in 0.5 mol / L sulfuric acid, and the current density reaches 10mA / cm 2 Only an overpotential of 153 mV is required. Figure 5 The C-RuO2 in is commercial ruthenium oxide. It can be seen that the fluorine-doped RuO2 in Examples 1-3 and Comparative Example 1 has better catalytic activity than commercial ruthenium oxide, which further illustrates that fluorine doping can improve the OER catalytic activity of RuO2. Compared with the F-RuO2 catalyst in Comparative Example 1, the 5F-RuO2 catalyst in Example 1 shows that the catalyst prepared in Example 1 has a lower overpotential, indicating that the fluorinated ruthenium oxide catalyst prepared by the doping method in Example 1 of the present invention has a more excellent OER catalytic activity. This is because the fluorine doping by the molten salt method can make the binding of fluorine in the RuO2 lattice more stable and uniform. In addition, it can also be noted that the RuO2 prepared by the molten salt method in Comparative Example 2 has substantially equivalent catalytic activity to the fluorine-doped RuO2 prepared by the method of Comparative Example 1, which indicates that the RuO2 prepared by the molten salt method has better catalytic activity than the RuO2 prepared by the method of Comparative Example 1, further demonstrating the superiority of the molten salt method of the present invention over the method of Comparative Document 1.

[0055] like Figure 6 As shown, the fluorinated ruthenium oxide catalyst prepared in Example 1 of the present invention is heated to 10 mA / cm 2 The catalyst exhibited excellent stability in the long-term electrolysis test, and the potential decay rate was only 27 μV / h after 982 h of stability test. However, the commercial ruthenium oxide C-RuO2 can only last for more than ten hours, and the stability of the catalyst without fluorine doping in comparative example 2 is also much lower than that of Example 1 of the present invention, indicating that the present invention greatly improves the stability of the ruthenium oxide catalyst by fluorine doping.

[0056] Figure 7 The results show that the fluorinated ruthenium oxide catalyst in PEMWE only requires an electrolyzer voltage of 1.81 V to achieve 2 A / cm 2 The current density is significantly better than that of commercial ruthenium oxide catalysts.

Claims

1. A method for preparing a fluorinated ruthenium oxide catalyst, characterized in that: include: S1, dissolving a ruthenium precursor salt and a fluoride salt in an alcohol solvent to obtain a mixed solution; S2, drying the mixed solution to remove the alcohol solvent to obtain a catalyst precursor; S3, adding the catalyst precursor into the molten nitrate to react, and after the reaction is completed, washing and drying the obtained product to obtain a fluorinated ruthenium oxide catalyst.

2. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S1, the ruthenium precursor salt is one or more of ruthenium acetylacetonate, ruthenium trichloride, ruthenium acetate, potassium pentachlororuthenate, hexaammineruthenium chloride and ammonium hexachlororuthenate.

3. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S1, the fluoride salt is one or more of sodium fluoride, lithium fluoride, potassium fluoride, ammonium fluoride and calcium fluoride.

4. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S1, the alcohol solvent is one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol and glycerol.

5. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S1, the molar ratio of ruthenium to fluorine in the mixed solution is 1:(1-30).

6. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S2, the drying temperature is 40-100°C and the drying time is 1-10 h.

7. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S3, the reaction temperature is 200-500°C, and the reaction time is 1-10 min.

8. The method for preparing the fluorinated ruthenium oxide catalyst according to claim 1, characterized in that: In S3, the nitrate is one or more of potassium nitrate, sodium nitrate, calcium nitrate, lithium nitrate, magnesium nitrate and sodium nitrite.

9. A fluorinated ruthenium oxide catalyst obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the fluorinated ruthenium oxide catalyst according to claim 9 as an OER catalyst in proton exchange membrane water electrolysis.

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