High-stability ruthenium-based hydroxide electrocatalyst and preparation method thereof

Abstract

The invention belongs to the technical field of anion exchange membrane fuel cells, and discloses a high-stability ruthenium-based hydroxide electrocatalyst used as an anode of an anion exchange membrane fuel cell and a preparation method of the high-stability ruthenium-based hydroxide electrocatalyst. The catalyst is prepared by taking ruthenium as a unique active component, fullerene (C60) as a carbon substrate and polydopamine (PDA) as an additive through argon heat treatment. The preparation method disclosed by the invention is simple and easy to implement, and through the design scheme that C60 with high electron affinity is used as a carrier, the electronic structure of a ruthenium active site is effectively adjusted, and excessive adsorption of a ruthenium-based catalyst to hydroxyl species in a hydrogen oxidation reaction (HOR) process is weakened, so that the ruthenium reaction active site is greatly reserved for hydrogen adsorption, and the hydrogen adsorption efficiency is improved. Therefore, the stability of ruthenium-based electro-catalysis in hydrogen oxidation reaction can be greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of anion exchange membrane fuel cells, and particularly relates to a high-stability ruthenium-based hydrogen oxidation electrocatalyst, and also relates to a preparation method of the catalyst. BACKGROUND

[0002] Hydrogen is considered as an important carrier as a high-efficiency and clean energy. In a hydrogen-oxygen fuel cell system, a hydrogen oxidation reaction (HOR) is a core reaction process of an anode, and the activity and stability of a catalyst thereof directly affect the performance and durability of the fuel cell. At present, a proton exchange membrane fuel cell (PEMFC) has been widely researched and applied, but it generally relies on a platinum-based catalyst, resulting in a large consumption of noble metals and high cost, so that large-scale popularization faces challenges. In comparison, an anion exchange membrane fuel cell (AEMFC) has become a research hotspot in the current fuel cell field because it can operate under milder conditions and has advantages of low requirement for the amount of noble metals and lower system cost.

[0003] In the anion exchange membrane fuel cell, the development of a hydrogen oxidation reaction catalyst is particularly crucial. In recent years, ruthenium (Ru) has gradually become an important alternative to the platinum-based catalyst because it is lower in cost than platinum and exhibits higher hydrogen oxidation reaction activity under alkaline conditions. However, the existing ruthenium-based catalysts have significant deficiencies in actual application: when the potential exceeds about 0.1 V (relative to the reversible hydrogen electrode, RHE), the catalyst is prone to strong adsorption of surface hydroxyl (OH*) species, so that the active sites are occupied, and eventually the catalyst is deactivated. This problem greatly limits the application of the ruthenium-based catalyst in a wide potential range, and also makes it difficult for the catalyst to maintain a large power output in the actual fuel cell operating conditions.

[0004] In view of the above problems, the existing technical research mainly focuses on improving the hydrogen oxidation reaction performance of ruthenium by regulating the electronic structure of ruthenium, constructing an alloy or interacting with a carbon carrier and the like. However, these methods still have the following deficiencies: (1) these adjustment methods mainly improve the activity of the catalyst, but the catalyst is still difficult to avoid surface over-oxidation at high potentials; (2) although alloying or doping modification can partially alleviate the strong adsorption of OH*, the preparation process is complex, it is difficult to balance the cost and large-scale preparation, and the conductivity of the catalyst is reduced, which inevitably affects the actual application of the catalyst; (3) some supported catalysts are prone to metal loss or carrier corrosion during operation, which further weakens the stability.

[0005] Therefore, how to design and prepare a ruthenium-based catalyst which can maintain excellent hydroxidation reaction activity under alkaline conditions and stable catalytic activity under high overpotential conditions has become a key technical problem to be solved in the current technical field. SUMMARY

[0006] The first object of the present application is to provide a high-stability ruthenium-based hydroxidation electrocatalyst, which improves the adsorption strength of ruthenium to the hydroxyl reaction intermediate by using fullerene as a carrier to adjust the electronic state of ruthenium, thereby ultimately improving the stability of the ruthenium-based catalyst. The prepared catalyst shows excellent stability in hydrogen oxidation reaction and can maintain activity at a potential as high as 0.9 V (vs. RHE).

[0007] The second object of the present application is to provide a preparation method of the high-stability ruthenium-based hydroxidation electrocatalyst.

[0008] Technical scheme: The present application uses fullerene as a carrier, uses ruthenium metal nanoparticles as an active component, and ultimately obtains the electrocatalyst by using polydopamine to enhance the interaction force between the two. The catalyst has the advantages of simple preparation method, low cost, high repeatability, etc., and can promote the development of anion exchange membrane fuel cells.

[0009] The method for preparing the high-stability ruthenium-based hydroxidation electrocatalyst of the present application comprises the following steps:

[0010] A. Fullerene and ruthenium-containing precursor salt are weighed according to the mass ratio, dispersed in a certain amount of deionized water / ethanol mixed solution, and subjected to magnetic stirring;

[0011] B. A certain amount of dopamine is weighed and added to the mixed solution of step A, and magnetic stirring is ensured;

[0012] C. Under the condition of stirring, ammonia solution is added dropwise to the solution of step B, and the pH value of the mixed solution is continuously monitored using a pH meter until the pH of the solution reaches 8-9, and then the stirring of the solution is continued.

[0013] D. The solution obtained in step C is subjected to centrifugation, washing and drying treatment;

[0014] E. The solid after step D treatment is placed in a tube furnace, and high-temperature calcination treatment is carried out under argon atmosphere to obtain the electrocatalyst of the present application.

[0015] The method for preparing the high-stability ruthenium-based hydroxidation electrocatalyst of the present application has the characteristics that,

[0016] The mass ratio of the fullerene and the deionized water / ethanol mixed solution in step A is 1:(600-1000), the volume ratio of water and ethanol in the water / ethanol mixed solution is 1:1, and the stirring rate of the magnetic stirring is 300-800 rpm.

[0017] The mass ratio of the added dopamine and the fullerene in the solution in step B is 1:(2-4).

[0018] The mass concentration of the ammonia solution in step C is 20%-40%, and the stirring time is 12-24 hours.

[0019] In step D, the centrifugal speed is 3000-8000 rpm, the centrifugal time is 5-10 minutes, the washing solvent is an ethanol solution, the drying temperature is 80-100 ℃, and the drying time is 12-24 hours.

[0020] In step E, the calcination temperature is 500-700 ℃, the heating rate is 5-10 ℃ / min, and the calcination time is 2-4 hours.

[0021] Beneficial effects: Compared with the prior art, the beneficial effects of the present application are embodied in: (1) the preparation method of the high-stability ruthenium-based hydrogen oxidation electrocatalyst provided by the present application has the advantages of simple operation, low cost, good repeatability and easy scale-up; (2) the high-stability ruthenium-based hydrogen oxidation electrocatalyst of the present application effectively solves the defect that the ruthenium-based material is easily deactivated when the potential exceeds 0.1 V (vs. RHE) in the alkaline hydrogen oxidation reaction. Therefore, the electrocatalyst and the corresponding synthesis method obtained by the present application can provide support for the development of anion exchange membrane fuel cells, and have far-reaching scientific research and practical application significance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The ruthenium / C obtained in Example 1 has a ruthenium content of 12.66 wt% 60 Transmission electron microscope image of the composite material;

[0023] Figure 2 The ruthenium / C obtained in Example 2 has a ruthenium content of 17.11 wt% 60 Transmission electron microscope image of the composite material;

[0024] Figure 3 The ruthenium / C obtained in Example 3 has a ruthenium content of 22.75 wt% 60 Transmission electron microscope image of the composite material;

[0025] Figure 4 The ruthenium / C obtained in Example 4 has a ruthenium content of 37.73 wt% 60 Transmission electron microscope image of the composite material;

[0026] Figure 5 TEM image of the ruthenium metal particles obtained in Comparative Example 1;

[0027] Figure 6 Electrochemical hydrogen oxidation performance comparison chart of the catalytic materials obtained in Examples 1-4 and commercial platinum-carbon (Pt / C);

[0028] Figure 7 Electrochemical hydrogen oxidation performance chart of the catalytic material obtained in Comparative Example 1. DETAILED DESCRIPTION

[0029] The technical solutions of the present application are further described in detail below in conjunction with examples.

[0030] Example 1

[0031] (1) 50 mg of fullerene and 26.15 mg of ruthenium trichloride trihydrate were weighed and dispersed in a mixed solution of 20 mL of deionized water / 20 mL of ethanol, and a magnetic stirrer was used to stir at a speed of 500 rpm;

[0032] (2) 25 mg of dopamine powder was weighed and added to the mixed solution of step (1) and the stirring was continued;

[0033] (3) A 30wt% ammonia solution was added dropwise to the solution of step (2), and a pH meter was used for continuous monitoring until the pH value of the solution became between 8 and 9, and then the stirring was continued for 12 hours;

[0034] (4) The product after sufficient reaction in step (3) was collected by centrifugation at a speed of 5000 rpm for 3 minutes using a centrifuge tube, and then the collected solid sample was placed in an oven at a temperature of 100°C for 12 hours to completely dry it.

[0035] (5) The dried sample in step (4) was placed in a tube furnace, argon was introduced, and then the temperature was raised from room temperature to 600°C at a rate of 5°C / min, and kept at 600°C for 2 hours, and then naturally cooled to room temperature to obtain the high-stability ruthenium-based hydrogen oxidation electrocatalyst of the present application.

[0036] The ruthenium mass fraction of the sample obtained in this example was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the final result was 12.66wt%, and the morphology of the sample was analyzed using a transmission electron microscope, and the results are shown in Figure 1

[0037] Example 2

[0038] ​(1) Weigh 50 mg of fullerene and 39.22 mg of ruthenium trichloride trihydrate and disperse them in a mixture of 20 mL of deionized water and 20 mL of ethanol. Stir the mixture at 500 rpm using a magnetic stirrer.

[0039] (2) Weigh 25 mg of dopamine powder and add it to the mixed solution of step (1) while continuing to stir;

[0040] (3) adding a 30 wt% ammonia solution dropwise to the solution of step (2) and continuously monitoring the solution with a pH meter until the pH value of the solution becomes between 8 and 9, and then continuing to stir for 12 hours;

[0041] (4) The product after the reaction in step (3) was collected by centrifugation at 5000 rpm for 3 minutes using a centrifuge tube, and then the collected solid sample was placed in an oven at 100° C. for 12 hours to completely dry it.

[0042] (5) The dried sample in step (4) is placed in a tube furnace and argon is introduced, and then the temperature is increased from room temperature to 600°C at a heating rate of 5°C / min, and maintained at 600°C for 2 hours, and then naturally cooled to room temperature to obtain the highly stable ruthenium-based hydroxide electrocatalyst of the present invention.

[0043] The ruthenium mass fraction of the sample obtained in this example was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the final result was 17.11 wt %. The morphology of the sample was analyzed using a transmission electron microscope, and the results were as follows: Figure 2 As shown, the ruthenium nanoparticles are still evenly dispersed on the surface of the fullerene substrate.

[0044] Example 3

[0045] (1) Weigh 50 mg of fullerene and 52.29 mg of ruthenium trichloride trihydrate and disperse them in a mixture of 20 mL of deionized water and 20 mL of ethanol. Stir the mixture at 500 rpm using a magnetic stirrer.

[0046] (2) Weigh 25 mg of dopamine powder and add it to the mixed solution of step (1) while continuing to stir;

[0047] (3) adding a 30 wt% ammonia solution dropwise to the solution of step (2) and continuously monitoring the solution with a pH meter until the pH value of the solution becomes between 8 and 9, and then continuing to stir for 12 hours;

[0048] (4) using a centrifuge tube, the product after fully reacting in step (3) is centrifuged at a speed of 5000 rpm for 3 minutes for collection, and then the collected solid sample is placed in an oven at a temperature of 100°C for 12 hours for complete drying.

[0049] (5) the dried sample in step (4) is placed in a tube furnace, argon is introduced, then the temperature is raised from room temperature to 600°C at a rate of 5°C / min, and kept at 600°C for 2 hours, and then naturally cooled to room temperature to obtain the high-stability ruthenium-based hydroxidation electrocatalyst of the present application.

[0050] The ruthenium mass fraction of the sample obtained in this example is determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the final result is 22.75wt%, and the morphology of the sample is analyzed using a transmission electron microscope, and the results are shown in Figure 3 As the ruthenium content increases, the size of the ruthenium particles also increases significantly.

[0051] Example 4

[0052] (1) 50mg of fullerene and 104.59mg of ruthenium trichloride trihydrate are weighed and dispersed in a mixed solution of 20mL of deionized water / 20mL of ethanol, and a magnetic stirrer is used to stir at a speed of 500rpm;

[0053] (2) 25mg of dopamine powder is weighed and added to the mixed solution of step (1) and the stirring is continued;

[0054] (3) 30wt% ammonia solution is added dropwise to the solution of step (2), and a pH meter is used for continuous monitoring until the pH value of the solution becomes between 8 and 9, and then the stirring is continued for 12 hours;

[0055] (4) using a centrifuge tube, the product after fully reacting in step (3) is centrifuged at a speed of 5000 rpm for 3 minutes for collection, and then the collected solid sample is placed in an oven at a temperature of 100°C for 12 hours for complete drying.

[0056] (5) the dried sample in step (4) is placed in a tube furnace, argon is introduced, then the temperature is raised from room temperature to 600°C at a rate of 5°C / min, and kept at 600°C for 2 hours, and then naturally cooled to room temperature to obtain the high-stability ruthenium-based hydroxidation electrocatalyst of the present application.

[0057] The ruthenium mass fraction of the sample obtained in this example was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the final result was 37.73wt%. Meanwhile, the morphology of the sample was analyzed using a transmission electron microscope, and the results are shown in Figure 4 It can be seen that the nano-ruthenium particles are uniformly dispersed on the surface of the fullerene substrate in a larger particle size than in Examples 1-3.

[0058] Comparative Example 1

[0059] (1) 50 mg of ruthenium trichloride trihydrate was weighed and dispersed in a mixture of 20 mL of deionized water and 20 mL of ethanol, and a magnetic stirrer was used to stir at a speed of 500 rpm;

[0060] (2) A 30wt% ammonia solution was added dropwise to the solution of step (1), and a pH meter was used for continuous monitoring until the pH value of the solution changed to between 8 and 9, and then the stirring was continued for 12 hours;

[0061] (3) The product after sufficient reaction in step (2) was collected by centrifugation at a speed of 5000 rpm for 3 minutes using a centrifuge tube, and then the collected solid sample was placed in an oven at a temperature of 100°C for 12 hours to completely dry.

[0062] (4) The dried sample in step (3) was placed in a tube furnace, and argon was introduced, then the temperature was raised from room temperature to 600°C at a rate of 5°C / min, and kept at 600°C for 2 hours, and then naturally cooled to room temperature to obtain the comparative sample ruthenium metal particles of the present application.

[0063] The morphology of the ruthenium metal particles of the present comparative example was analyzed using a transmission electron microscope, and the results are shown in Figure 5 It can be seen that the ruthenium metal particles exhibit a larger and non-uniform morphology.

[0064] Performance test

[0065] The hydrogen oxidation performance of the five catalytic materials prepared in Examples 1-4 and Comparative Example 1 was tested and compared with a commercial platinum-carbon (Pt / C) catalyst. First, 5 mg of the catalyst material was weighed and dispersed in 1 mL of an ethanol solution containing 40 μL of a Nafion solution, and ultrasonic treatment was performed for 30 minutes to form a uniform slurry. Then 10 μL of the catalyst slurry was taken using a pipette and dropped onto a rotating disc electrode with a diameter of 4 mm, and after natural air drying, it became the working electrode. Then, a Hg / HgO electrode and a graphite electrode were matched, and the experiment was carried out on a rotating electrode device. 0.1M KOH was used as the electrolyte, and linear voltammetry scanning was carried out at an electrode speed of 1600 rpm, and the test results are shown in Figures 6-7The results show that the four catalysts prepared by Examples 1-4 all exhibit excellent stability in hydrogen oxidation reaction, and their performances are close to that of commercial platinum carbon under an ultra-wide potential operating window, while the ruthenium metal particles prepared by the conventional method are obviously deactivated. This result confirms that the preparation method of the present application can improve the stability of ruthenium-based materials in hydrogen oxidation reaction.

[0066] The above examples and comparative examples are not intended to limit the present application, and it should be noted that any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A highly stable ruthenium-based hydrogen oxidation electrocatalyst, characterized in that: The catalyst is fullerene (C 60 ) as a carrier, ruthenium metal nanoparticles as the active component, and are prepared by adding polydopamine (PDA) to regulate the dispersibility of the metal particles and enhance the interaction between the particles and the carrier; wherein the mass ratio of fullerene and metal ruthenium particles in the ruthenium-based hydrogen hydroxide electrocatalyst is 1: (0.1~0.7), and the active component metal ruthenium comes from a ruthenium-containing precursor salt.

2. A highly stable ruthenium-based hydrogen oxidation electrocatalyst according to claim 1, characterized in that: The ruthenium-containing precursor salt is one or more of ruthenium trichloride, ruthenium trichloride trihydrate, ruthenium nitrosyl nitrate, and ruthenium acetylacetonate.

3. A method for preparing the highly stable ruthenium-based hydrogen hydroxide electrocatalyst according to claim 1, characterized in that The steps include: A. Weigh fullerene and ruthenium-containing precursor salt according to the mass ratio, disperse them in a certain amount of deionized water / ethanol mixed solution and stir them magnetically; B. Weigh a certain amount of dopamine and add it to the mixed solution in step A while maintaining magnetic stirring; C. Under stirring, add aqueous ammonia solution dropwise to the solution of step B, and continuously monitor the pH value of the mixed solution using a pH meter until the pH of the solution reaches 8-9, and then continue to stir the solution. D. centrifuging, washing, and drying the solution obtained in step C above; E. The solid treated in step D is placed in a tube furnace and calcined at high temperature under argon atmosphere to obtain the electrocatalyst of the present invention.

4. The method for preparing a highly stable ruthenium-based hydrogen hydroxide electrocatalyst according to claim 3, wherein: In step A, the mass ratio of the fullerene to the deionized water / ethanol mixed solution is 1:(600-1000), the volume ratio of water to ethanol in the water / ethanol mixed solution is 1:1, and the magnetic stirring rate is 300-800 rpm.

5. The method for preparing a highly stable ruthenium-based hydrogen hydroxide electrocatalyst according to claim 3, wherein: In step B, the mass ratio of the added amount of dopamine to the fullerene in the solution is 1:(2-4).

6. The method for preparing a highly stable ruthenium-based hydrogen hydroxide electrocatalyst according to claim 3, wherein: In step C, the mass concentration of the ammonia solution is 20% to 40%, and the stirring time is 12 to 24 hours.

7. The method for preparing a highly stable ruthenium-based hydrogen hydroxide electrocatalyst according to claim 3, characterized in that: In step D, the centrifugal speed is 3000-8000 rpm, and the centrifugal time is 5-10 minutes; the washing solvent is an ethanol solution; the drying temperature is 80-100° C., and the drying time is 12-24 hours.

8. The method for preparing a highly stable ruthenium-based hydrogen hydroxide electrocatalyst according to claim 3, wherein: In step E, the calcination temperature is 500-700° C., the heating rate is 5-10° C. / min, and the calcination time is 2-4 hours.

9. A highly stable ruthenium-based hydrogen oxidation electrocatalyst according to claim 1, further characterized by: Used in the anode of anion exchange membrane fuel cells.

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