A ruthenium nanocage used as an anode material for alkaline fuel cells and a preparation method thereof

Abstract

The present invention belongs to the technical field of alkaline fuel cells, and discloses a ruthenium nanocage used as an anode material for alkaline fuel cells and a preparation method thereof, wherein a metal organic framework material is used as a template, and a metal organic framework composite material adsorbing ruthenium is subjected to hydrogen argon reduction and acid etching treatment in succession, and finally a porous ruthenium nanocage is prepared. The preparation method of the present invention is simple to operate, and the obtained product has a large specific surface area and excellent electrochemical performance, and can effectively improve the activity and stability of the ruthenium-based electrocatalyst in the hydrogen oxidation reaction.

Description

Technical Field

[0001] The invention relates to an alkaline fuel cell anode material, belonging to the technical field of alkaline fuel cells. Background Art

[0002] Anion exchange membrane fuel cells (AEMFCs) are highly attractive for efficient utilization of hydrogen energy due to the rapid development of PGM-free electrocatalysts for the oxygen reduction reaction at the cathode. However, the kinetics of the anodic hydrogen oxidation reaction (HOR) in alkaline media are two orders of magnitude slower than in acidic media. The anode platinum loading of AEMFCs needs to be much higher (10-100 times) than that of PEM. Although Pt-based electrocatalysts generally have satisfactory activity performance for HOR under alkaline conditions, the high price of Pt must be considered during the commercialization of fuel cells. Therefore, the development of robust, cost-effective, low-Pt or Pt-free electrocatalysts is of great significance for the practical application of AEMFCs. Ruthenium (Ru) is considered as a potential alternative to Pt as a hydrogen oxidation electrocatalyst due to its lower price (about 50% of Pt), similar hydrogen binding energy to Pt, and reasonable oxygen affinity. Ru is able to maintain a balanced adsorption of adsorbed hydrogen and adsorbed hydroxyl groups at low anode potentials, which is crucial for achieving high HOR catalytic performance in alkaline media. However, the activity and stability of Ru-based HOR electrocatalysts usually decay rapidly at relatively high anodic potentials (>0.1 V vs. RHE).

[0003] In summary, it is necessary to find a simple and efficient preparation method to synthesize nanomaterials with special structures and ensure that the material has high activity and stability to meet its application as a ruthenium-based catalyst material in hydrogen oxidation electrocatalysis. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing ruthenium nanocages used as an anode material for alkaline fuel cells. The technical problem to be solved is to make the preparation method have the advantages of simplicity, low cost, high repeatability, etc., and at the same time make the resulting product have a large specific surface area, excellent stability and outstanding electrochemical performance.

[0005] The present invention solves the technical problem by adopting the following technical solution:

[0006] A method for preparing ruthenium nanocages used as anode materials for alkaline fuel cells, characterized in that: using metal organic framework material ZIF-8 as a template, first adsorbing ruthenium chloride onto the ZIF-8 template to obtain a Ru@ZIF-8 composite material, then calcining and reducing the Ru@ZIF-8 in a reducing atmosphere to obtain a RuZn composite material, and finally soaking the RuZn composite material in a hydrochloric acid solution to etch away zinc to obtain a Ru nanocage. Specifically comprising the following steps:

[0007] a. Dissolve 0.72 g to 0.73 g of zinc nitrate hexahydrate in 25 mL of deionized water to obtain solution A; dissolve 11 g to 12 g of 2-methylimidazole and 0.03 g to 0.04 g of hexadecyltrimethylamine bromide in 175 mL of deionized water to obtain solution B; quickly inject solution A into solution B, stir evenly with a magnetic stirrer, and allow to react at 28 to 33 ° C for 2 h to 3 h to obtain a ZIF-8 solution;

[0008] b. Take 8 mL of the ZIF-8 solution obtained in step a and centrifuge it. Wash the precipitate with methanol and centrifuge it. Then, add it to 3 mL of deionized water and disperse it evenly with ultrasound to obtain solution C.

[0009] Weigh 0.00621g-0.01449gRuCl3, add it into 2-3mL deionized water and dissolve it by ultrasonic to obtain solution D; inject solution D into solution C under magnetic stirring, then add 1mL methanol solution, stir it evenly by magnetic stirring, and hydrothermally react in an oven at 80℃ for 2h. After the reaction, centrifuge and vacuum dry to obtain Ru@ZIF-8 composite material;

[0010] c. transferring the Ru@ZIF-8 composite material to a tubular furnace and calcining and reducing it under a reducing atmosphere to obtain a RuZn composite material;

[0011] d. Immerse the RuZn composite material in a 1M hydrochloric acid solution to etch away zinc, then centrifuge, and then wash and centrifuge with methanol to obtain Ru nanocages.

[0012] Preferably, in step a, the rotation speed of the magnetic stirring is 350-450 rpm and the time is 5 min.

[0013] Preferably, in step b, the rotation speed of the centrifugal separation is 12000 rpm, the rotation speed of the magnetic stirring is 350-450 rpm, the temperature of the vacuum drying is 60-70° C., and the drying time is 6-7 h.

[0014] Preferably, in step c, the reducing atmosphere is H2 / Ar atmosphere, the calcination temperature is 250-350°C, the calcination time is 2h, and the heating rate is 10°C / min.

[0015] The ruthenium nanocage prepared by the invention can be used as an anode material for alkaline fuel cells.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. The present invention provides a method for preparing Ru nanocages, which has the advantages of simple operation, low cost, good repeatability and uniform product structure. The product obtained by the present invention has a larger specific surface area, excellent stability and outstanding electrochemical performance.

[0018] 2. The product obtained by the present invention is a catalyst material in the hydrogen oxidation reaction, which effectively solves the problem that the activity and stability of ruthenium-based materials in the hydrogen oxidation reaction usually decay rapidly at a relatively high anode potential, thereby improving their activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a transmission electron microscopy image of ZIF-8 obtained in step 1 of Example 1;

[0020] Figure 2 This is a transmission electron microscopy image of the Ru@ZIF-8 composite material obtained in step 2 of Example 1;

[0021] Figure 3 This is a transmission electron microscope image of the RuZn composite material obtained in step 3 of Example 1;

[0022] Figure 4 This is a transmission electron microscopy image of the Ru nanocage obtained in step 4 of Example 1;

[0023] Figure 5 This is a comparison chart of the electrochemical performance of the target product Ru nanocage obtained in step 4 of Example 1 and commercial platinum carbon (Pt / C). DETAILED DESCRIPTION

[0024] In order to further illustrate the features and advantages of the present invention, the embodiments of the present invention are described in detail below. The following embodiments are only part of the present invention, and the protection scope of the present invention is not limited to the following embodiments. The reagents and materials used in the following embodiments can be obtained from commercial channels unless otherwise specified; the electrochemical performance tests in the following embodiments are all adopted.

[0025] The centrifuge used in the following examples is AnkeTGL-10B produced by Shanghai Anting Scientific Instrument Factory, the magnetic stirrer is MS-MS-10 multi-head magnetic stirrer produced by Shanghai Kunquan Biotechnology Co., Ltd., the tube furnace is OTF-1200X produced by Hefei Kejing Material Technology Co., Ltd., and the transmission electron microscope is JEOL-F2010 produced in Japan. The drugs used in the following examples were used directly after purchase without any treatment.

[0026] Example 1

[0027] In this embodiment, Ru nanocages were prepared according to the following steps:

[0028] Step 1. Take 0.7252g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and add it to 25mL of deionized water, stir it evenly with a magnetic force (speed is 400rpm, time is 10min), and obtain solution A; add 11.3504g of 2-methylimidazole and 0.035g of hexadecyltrimethylamine bromide (CTAB) to 175mL of deionized water, stir it evenly with a magnetic force (speed is 400rpm, time is 10min), and obtain solution B; quickly inject solution A into solution B, stir it evenly with a magnetic force (speed is 400rpm, time is 5min), and let it stand at 32°C for 3h to obtain a ZIF-8 solution.

[0029] Step 2: Take 8 mL of the ZIF-8 solution prepared in step 1, centrifuge (speed 12000 rpm, time 20 min), wash twice with methanol, centrifuge (speed 12000 rpm, time 15 min), add 3 mL of deionized water and ultrasonically disperse evenly, place in a 20 mL polytetrafluoroethylene reactor, and obtain solution C. Take 0.01035 g of RuCl3 and dissolve it in 2 mL of deionized water and ultrasonically dissolve it to obtain solution D; inject solution D into solution C under magnetic stirring (speed 400 rpm), then add 1 mL of methanol solution, magnetic stirring (speed 400 rpm) for 50 min, and after stirring, hydrothermally react in an oven at 80 ° C for 2 h. After the reaction is completed, centrifuge (speed 12000 rpm, time 10 min), and vacuum dry at 60 ° C for 7 h to obtain Ru@ZIF-8 composite material.

[0030] Step 3: Put the Ru@ZIF-8 composite material obtained in step 2 into a porcelain boat, and then put it into a tubular furnace, heat it to 300°C at a heating rate of 10°C / min under a 5% H2 / 95% Ar atmosphere, and calcine it for 2 hours to obtain a RuZn composite material.

[0031] Step 4: Weigh 10 mg of the RuZn composite material obtained in step 3, add 1 mL of 1 M hydrochloric acid solution thereto, soak for 60 min, centrifuge (speed is 9000 rpm, time is 7 min), wash with methanol, and centrifuge again (speed is 9000 rpm, time is 7 min) to obtain Ru nanocages.

[0032] Figure 1 This is the transmission electron microscopy image of ZIF-8 obtained in step 1 of Example 1. Figure 2 This is a transmission electron microscope image of the Ru@ZIF-8 composite material obtained in step 2 of Example 1. Figure 3 This is a transmission electron microscope image of the RuZn composite material obtained in step 3 of Example 1. Figure 4This is a transmission electron microscope image of the Ru nanocage obtained in step 4 of Example 1. From the image, it can be seen that the pores of the Ru nanocage become larger after acid washing, but the cage-like structure is still maintained.

[0033] Weigh 5 mg of Ru nanocages, add 470 μL of isopropanol and 30 μL of Nafion, and ultrasonicate for more than 30 minutes to disperse the catalyst evenly. Then take 10 μL of the dispersion and drop it on the glassy carbon electrode. After the dispersion is dry, it is used as the working electrode for the hydrogen oxidation reaction test. The reference electrode is Hg / HgO and the counter electrode is a carbon rod electrode. The electrochemical test is carried out in a 0.1M KOH electrolyte saturated with H2.

[0034] Figure 5 This is a comparison of the electrochemical performance of the target product Ru nanocage obtained in Example 1 and commercial Pt / C. It can be seen from the figure that the activity of Ru nanocage is significantly higher than that of commercial Pt / C.

[0035] The above description is only an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing ruthenium nanocages used as anode materials for alkaline fuel cells, characterized in that: Using the metal organic framework material ZIF-8 as a template, ruthenium chloride is first adsorbed onto the ZIF-8 template to obtain a Ru@ZIF-8 composite material, and then the Ru@ZIF-8 is calcined and reduced in a reducing atmosphere to obtain a RuZn composite material. Finally, the RuZn composite material is immersed in a hydrochloric acid solution to etch away zinc to obtain a Ru nanocage.

2. The preparation method according to claim 1, characterized in that: The steps include: a. Dissolve 0.72 g to 0.73 g of zinc nitrate hexahydrate in 25 mL of deionized water to obtain solution A; dissolve 11 g to 12 g of 2-methylimidazole and 0.03 g to 0.04 g of hexadecyltrimethylamine bromide in 175 mL of deionized water to obtain solution B; quickly inject solution A into solution B, stir evenly with a magnetic stirrer, and allow to react at 28 to 33 ° C for 2 h to 3 h to obtain a ZIF-8 solution; b. Take 8 mL of the ZIF-8 solution obtained in step a and centrifuge it. Wash the precipitate with methanol and centrifuge it. Then, add 3 mL of deionized water and disperse it evenly with ultrasound to obtain solution C. Weigh 0.00621g-0.01449gRuCl3, add it into 2-3mL deionized water and dissolve it by ultrasonic to obtain solution D; inject solution D into solution C under magnetic stirring, then add 1mL methanol solution, stir it evenly by magnetic stirring, and hydrothermally react in an oven at 80℃ for 2h. After the reaction, centrifuge and vacuum dry to obtain Ru@ZIF-8 composite material; c. transferring the Ru@ZIF-8 composite material to a tubular furnace and calcining and reducing it under a reducing atmosphere to obtain a RuZn composite material; d. Immerse the RuZn composite material in a 1M hydrochloric acid solution to etch away zinc, then centrifuge, and then wash and centrifuge with methanol to obtain Ru nanocages.

3. The preparation method according to claim 2, characterized in that: In step a, the rotation speed of the magnetic stirring is 350-450 rpm and the time is 5 min.

4. The preparation method according to claim 2, characterized in that: In step b, the rotation speed of the centrifugal separation is 12000 rpm, the rotation speed of the magnetic stirring is 350-450 rpm, the temperature of the vacuum drying is 60-70° C., and the drying time is 6-7 hours.

5. The preparation method according to claim 2, characterized in that: In step c, the reducing atmosphere is H2 / Ar atmosphere, the calcination temperature is 250-350°C, the calcination time is 2h, and the heating rate is 10°C / min.

6. A ruthenium nanocage prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the ruthenium nanocage according to claim 6 in an alkaline fuel cell anode material.

Images