Preparation method and application of a Pd-based alloy supported catalyst

Abstract

The present invention discloses a preparation method and application of a Pd-based alloy supported catalyst, belonging to the technical field of fuel cell electrocatalysis. The preparation method of the Pd-based alloy supported catalyst comprises the following steps: S1. Prepare a nitrogen-doped flaky MXene material; S2. Prepare nitrogen-doped flaky MXene / carbon nanotubes; S3. Prepare a nitrogen-doped flaky MXene / carbon nanotubes / molybdenum disulfide composite material; S4. Load Pd, Cu, and Co on the nitrogen-doped flaky MXene / carbon nanotubes / molybdenum disulfide composite material to obtain the Pd-based alloy supported catalyst. In the present invention, metal particles are loaded through the unique spatial structure of the carrier, improving the dispersion, catalytic activity, stability, and CO poisoning resistance of the metal particles, and achieving higher electrocatalytic activity and durability while reducing the Pd usage amount.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell electrocatalysis, and in particular to a preparation method and application of a Pd-based alloy supported catalyst. Background Art

[0002] Hydrogen fuel cells play an important role in the future development of hydrogen energy. 2 There are still some problems in the process of transportation, preparation and storage, so the development of alternative energy is an important issue at present. Direct alcohol fuel cells (DAFCs) are used as portable power sources, and H 2 In comparison, commonly used alcohols such as methanol, ethanol and ethylene glycol have higher volume energy density and exist in liquid form at room temperature, making their storage and transportation much easier than hydrogen. Compared with methanol and ethanol, ethylene glycol has a higher electron transfer number and low volatility during electrochemical catalytic oxidation, and ethylene glycol has lower fuel permeability and higher energy density. All these advantages make ethylene glycol-based fuel cells a promising alternative energy source.

[0003] With the continuous development of fuel cells, Pt is a common active component in direct ethylene glycol fuel cells. Therefore, highly dispersed Pt nanoparticles can be loaded onto a carrier with an appropriate surface area and excellent electrical conductivity to improve the anti-poisoning ability of the catalyst and use it more efficiently. However, due to the high economic cost and poor anti-poisoning performance of Pt, its practical application is limited. Pd and Pt belong to the same family of the periodic table, Pd and Pt present similar electrochemical properties, and Pd and Pt both present the same face-centered cubic structure, so Pd and Pd-based nanomaterials as potential substitutes for Pt have attracted more and more attention. However, when direct ethylene glycol fuel cells only use Pd as a catalyst, alcohol ethylene glycol will also undergo incomplete oxidation during the reaction process to produce some intermediates, and the enrichment of these intermediates will reduce the performance of the fuel cell. In addition, although the price of Pd metal is lower than that of Pt, Pd is still a precious metal, and the large-scale use of Pd is bound to increase the cost of fuel cells.

[0004] Therefore, it is necessary to develop a Pd-based alloy-supported catalyst that can achieve higher electrocatalytic activity and durability while reducing the amount of Pd used. Summary of the invention

[0005] Based on the problems existing in the background technology, the present invention provides a method for preparing a Pd-based alloy-supported catalyst, which achieves higher electrocatalytic activity and durability while reducing the amount of Pd used.

[0006] The present invention is implemented by the following technical solutions:

[0007] The first aspect of the present invention discloses a method for preparing a Pd-based alloy supported catalyst, comprising the following steps:

[0008] S1. dispersing the flaky MXene material in an acidic solution, adding a nitrogen-containing precursor, stirring, separating, washing the obtained product with deionized water until neutral, and calcining to obtain a nitrogen-doped flaky MXene material;

[0009] S2. Dispersing nitrogen-doped flaky MXene in deionized water, dispersing carbon nanotubes in ethanol, and then mixing the nitrogen-doped flaky MXene aqueous solution and the carbon nanotube alcohol solution, stirring at room temperature, separating, and vacuum drying to obtain nitrogen-doped flaky MXene / carbon nanotubes;

[0010] S3. The pH value of the sodium molybdate solution is adjusted to acidic with a hydrochloric acid solution, L-cysteine ​​is added, and after ultrasonic treatment, nitrogen-doped flaky MXene / carbon nanotubes are continuously added, hydrothermally reacted, cooled to room temperature, separated, and the obtained product is washed with ethanol and deionized water, and dried to obtain a nitrogen-doped flaky MXene / carbon nanotube / molybdenum disulfide composite material;

[0011] S4. The nitrogen-doped MXene / carbon nanotube / MoS2 composite material was ultrasonically dispersed in deionized water and H 2 PdCl 4 、Cu(NO 3 ) 2 、Co(NO 3 ) 2 Then, the reducing agent is added dropwise while stirring, and the mixture is stirred in a water bath until the reaction is completed. The mixture is separated, and the obtained product is washed with deionized water until it is neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0012] Furthermore, in step S1, the preparation of the sheet MXene material is specifically performed by etching Ti with a mixed solution of lithium fluoride and hydrochloric acid. 3 AlC 2 , ultrasonic dispersion, water bath etching, separation, and washing the obtained product with deionized water until neutral to obtain a flaky MXene material;

[0013] The concentration of hydrochloric acid in the mixed solution of lithium fluoride and hydrochloric acid is 8-10 mol / L, and the concentration of lithium fluoride is 75-90 g / L; 3 AlC 2 The mass ratio is 1:(0.6-0.9); etch under heating in a 45-55°C water bath for 24-36 hours.

[0014] Furthermore, in step S1, the acidic solution is a hydrochloric acid solution with a concentration of 1-3 mol / L; the nitrogen-containing precursor is an aminonitrile aqueous solution with a concentration of 50 wt%; the mass ratio of the nitrogen-containing precursor to the flaky MXene material is 1:(2-3); and the calcination temperature is 500-600°C.

[0015] Furthermore, in step S2, the carbon nanotubes need to be treated with acid, and the specific operation is: adding the carbon nanotubes to a mixed acid composed of concentrated nitric acid and concentrated sulfuric acid, and reacting in an oil bath under reflux, cooling to room temperature after the reaction is completed, separating, washing the obtained product with deionized water until it is neutral, and drying, thus completing the acid treatment of the carbon nanotubes;

[0016] The volume ratio of concentrated nitric acid to concentrated sulfuric acid in the mixed acid is 1:(0.5-2.5); the ratio of the amount of carbon nanotubes to the amount of the mixed acid is 1g:(10-50)mL; and the oil bath temperature is 80-120°C.

[0017] Furthermore, in step S2, the mass ratio of nitrogen-doped flaky MXene to carbon nanotubes is (4-8):1.

[0018] Furthermore, in step S3, the concentration of the sodium molybdate solution is 3.5 mg / mL; the concentration of L-cysteine ​​is 8.75 mg / mL; the mass ratio of nitrogen-doped flaky MXene / carbon nanotubes to sodium molybdate is (1.2-2.8):1; the hydrothermal reaction temperature is 180-200°C, and the reaction time is 24-36h.

[0019] Further, in step S4, the concentration of the nitrogen-doped flaky MXene / carbon nanotube / molybdenum disulfide composite material is 1-30 mg / mL;

[0020] The amount of nitrogen-doped MXene / carbon nanotube / MoS2 composites and H 2 PdCl 4 、Cu(NO 3 ) 2 、Co(NO 3 ) 2 The mass ratio of the total amount is (5-15): 1;

[0021] H 2 PdCl 4 、Cu(NO 3 ) 2 、Co(NO 3 ) 2 The molar ratio is 1:1:(1.2-1.5).

[0022] Furthermore, the reducing agent is a sodium borohydride solution with a solubility of 5-15 mg / mL.

[0023] The second aspect of the present invention discloses a Pd-based alloy supported catalyst prepared by the above preparation method.

[0024] The third aspect of the present invention discloses the use of a Pd-based alloy supported catalyst in a direct ethylene glycol fuel cell.

[0025] Beneficial effects of the present invention:

[0026] In the present invention, the electrocatalytic performance of the catalyst is improved and the cost of the catalyst is reduced by introducing Cu and Co metals. In addition, the unique electronic structure of the three metals Pd, Cu and Co can weaken the metal-CO bonding strength and improve the catalyst's CO poisoning resistance. The present invention loads the three metals Pd, Cu and Co onto a nitrogen-doped flaky MXene / carbon nanotube / molybdenum disulfide composite carrier, and loads metal particles through the unique spatial structure of the carrier, thereby improving the dispersibility, catalytic activity, stability and CO poisoning resistance of the metal particles.

[0027] The flaky MXene material used in the present invention has good conductivity, is conducive to the transmission of electrons, has a large specific surface area, and can provide a large number of attachment sites for metal particles; nitrogen doping improves the problem of easy collapse and restacking of the flaky MXene material, and ensures the stability of the flaky MXene material. When nitrogen is doped into the flaky MXene material, the ionic bonds between CN atoms are enhanced, while the covalent nature is weakened, thereby improving the adsorption performance of the surface of the flaky MXene material.

[0028] The addition of carbon nanotubes inhibits the serious stacking and agglomeration of nitrogen-doped flaky MXene sheets, effectively utilizes their interfaces, increases the number of attachment sites, and increases the specific capacity of the material. Moreover, the carbon-doped flaky MXene material and carbon nanotubes form a three-dimensional structure through a stable CN structure, further improving the stability of the catalyst. In addition, the carbon nanotubes are treated with a mixed acid of concentrated nitric acid and concentrated sulfuric acid to form more defects on the carbon nanotubes, remove impurities on the surface of the carbon nanotubes, and make the tube wall thinner, with obvious tube opening, providing more attachment sites; and the acid-treated carbon nanotubes can be better dispersed in an aqueous solution, which is beneficial to the subsequent loading of metal particles.

[0029] The two-dimensional material molybdenum disulfide is further introduced on the surface of nitrogen-doped flaky MXene / carbon nanotubes. Molybdenum disulfide grows on the surface of MXene / carbon nanotubes, further improving the stability of the carrier structure. It is not easy to denature in the air, easy to store, has a large specific surface area, and provides more attachment sites. It can effectively alleviate the structural collapse during the catalytic process and ensure the integrity of the carrier structure. In addition, nitrogen-doped flaky MXene / carbon nanotubes also improve the conductivity of molybdenum disulfide itself. The three form a unique structure, which greatly enriches the electron transmission channel, ensuring that the electron transmission is smooth while adding metal loads such as Pd, which is conducive to maximizing the catalytic effect. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] A method for preparing a Pd-based alloy supported catalyst comprises the following steps:

[0033] S1.8g lithium fluoride was added to 100mL 9mol / L hydrochloric acid solution and mixed well. 6.4g Ti 3 AlC 2 , ultrasonic dispersion, etching in a water bath at 50°C for 30h, separation, and washing the obtained product with deionized water until neutral to obtain a flaky MXene material;

[0034] 5 g of flaky MXene material was dispersed in a 2 mol / L hydrochloric acid solution, 2 g of a 50 wt% aminonitrile aqueous solution was added, stirred, separated, the obtained product was washed with deionized water until neutral, and calcined at 550°C to obtain a nitrogen-doped flaky MXene material;

[0035] S2. Add 3 g of carbon nanotubes to a mixed acid consisting of 50 mL of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:1, and react under reflux in an oil bath at 85°C. After the reaction is completed, cool to room temperature, separate, and wash the obtained product with deionized water until it is neutral, and dry, thereby completing the acid treatment of the carbon nanotubes;

[0036] 4.8 g of nitrogen-doped flaky MXene is dispersed in deionized water, and 0.8 g of carbon nanotubes is dispersed in ethanol. Then, the nitrogen-doped flaky MXene aqueous solution and the carbon nanotube alcohol solution are mixed, stirred at room temperature, separated, and vacuum dried to obtain nitrogen-doped flaky MXene / carbon nanotubes.

[0037] S3. Adjust the pH value of 80 mL of 3.5 mg / mL sodium molybdate solution to 6.5 with hydrochloric acid solution, add 0.7 g of L-cysteine, and after ultrasonic treatment, continue to add 0.616 g of nitrogen-doped flaky MXene / carbon nanotubes, hydrothermally react at 200 ° C for 24 h, cool to room temperature, separate, and wash the obtained product with ethanol and deionized water, and dry to obtain a nitrogen-doped flaky MXene / carbon nanotube / molybdenum disulfide composite material;

[0038] S4.0.58 g of nitrogen-doped MXene / carbon nanotube / molybdenum disulfide composite material was ultrasonically dispersed in 30 mL of deionized water and 0.0213 g of H 2 PdCl 4 、0.0188g Cu(NO 3 ) 2 , 0.0219g Co(NO 3 ) 2 Then, 5 mL of 6 mg / mL sodium borohydride was added dropwise while stirring, and stirred in a water bath at 200°C until the reaction was completed. The product was separated and washed with deionized water until neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0039] The prepared Pd-based alloy supported catalyst was dispersed in 9 mL of deionized water for later use. The electrochemical catalytic performance of the catalyst was analyzed at room temperature using a Shanghai Chenhua CH660B electrochemical workstation. A three-electrode system was used: a glassy carbon electrode (GC) was used as the working electrode (Φ = 3 mm, surface area 0.07 cm 2 ), platinum wire electrode as counter electrode, saturated calomel electrode (SCE) as reference electrode. All experiments were carried out at room temperature. The glassy carbon electrode was washed with Al 2 O 3 The powder was repeatedly polished on the suede, then ultrasonicated for 1 minute, dried and set aside. Use a pipette to transfer 5 μL of the uniformly dispersed catalyst solution after ultrasonication for 30 minutes, and drop it on the cleaned glassy carbon electrode, transfer twice, a total of 10 μL. Put it in a 50°C oven at a constant temperature for 10 minutes, and the glassy carbon electrode needs to keep balanced during the process.

[0040] Weigh 5.6g of KOH, measure 5mL of ethylene glycol, put them into a beaker, add 95mL of distilled water to obtain an electrolyte solution. Cyclic voltammetry was used to test the performance of the prepared catalyst. The three electrodes were inserted into the solution, fixed, and connected with wires. The working parameters were set as follows: the scanning range was -1.25V-0.45V, and the scanning rate was 50mVs -1 , sensitivity is set to 10 -3 .

[0041] The oxidation peak generated during the positive scan is the oxidation peak of ethylene glycol, and the current density is 47.52 mA cm -2 The oxidation peak generated during backscanning is the oxidation peak of the intermediate product CO, and the current density is 19.34 mA cm -2 ; Peak current density of forward scan I f and the peak current density I of the reverse scan b The ratio I f / I b , which can demonstrate the anti-poisoning ability of the catalyst, the I of the catalyst in Example 1 is calculated f / I b After 200 cycles of cyclic stability testing, the current density of the catalyst in Example 1 dropped to 40.69 mA·cm -2 , the attenuation rate is 14.4%.

[0042] Example 2

[0043] A method for preparing a Pd-based alloy supported catalyst comprises the following steps:

[0044] Steps S1-S3 are the same as in Example 1;

[0045] S4. 0.52 g of nitrogen-doped MXene / carbon nanotube / MoS2 composite was ultrasonically dispersed in 30 mL of deionized water and 0.017 g of H 2 PdCl 4 , 0.015g Cu(NO 3 ) 2 , 0.0201g Co(NO 3 ) 2 Then, 5 mL of 5 mg / mL sodium borohydride was added dropwise while stirring, and stirred in a water bath at 200°C until the reaction was completed. The product was separated and washed with deionized water until neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0046] The catalyst was used for electrochemical testing as in Example 1. The current density of the ethylene glycol oxidation peak was 43.67 mA·cm -2 The current density of the intermediate product CO oxidation peak is 17.55 mA cm -2 ; Catalyst I f / I b After 200 cycles of cyclic stability testing, the current density of the catalyst in Example 2 dropped to 37.04 mA·cm -2 , the attenuation rate is 15.2%.

[0047] Comparative Example 1

[0048] A method for preparing a Pd-based alloy supported catalyst comprises the following steps:

[0049] S1.8g lithium fluoride was added to 100mL 9mol / L hydrochloric acid solution and mixed well. 6.4g Ti 3 AlC 2 , ultrasonic dispersion, etching in a water bath at 50°C for 30h, separation, and washing the obtained product with deionized water until neutral to obtain a flaky MXene material;

[0050] 5 g of flaky MXene material was dispersed in a 2 mol / L hydrochloric acid solution, 2 g of a 50 wt% aminonitrile aqueous solution was added, stirred, separated, the obtained product was washed with deionized water until neutral, and calcined at 550°C to obtain a nitrogen-doped flaky MXene material;

[0051] S2. Add 3 g of carbon nanotubes to a mixed acid consisting of 50 mL of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:1, and react under reflux in an oil bath at 85°C. After the reaction is completed, cool to room temperature, separate, and wash the obtained product with deionized water until it is neutral, and dry, thereby completing the acid treatment of the carbon nanotubes;

[0052] 4.8 g of nitrogen-doped flaky MXene is dispersed in deionized water, and 0.8 g of carbon nanotubes is dispersed in ethanol. Then, the nitrogen-doped flaky MXene aqueous solution and the carbon nanotube alcohol solution are mixed, stirred at room temperature, separated, and vacuum dried to obtain nitrogen-doped flaky MXene / carbon nanotubes.

[0053] S3. 0.58 g of nitrogen-doped MXene / carbon nanotube composite material was ultrasonically dispersed in 30 mL of deionized water, and 0.0213 g of H 2 PdCl 4 、0.0188g Cu(NO 3 ) 2 , 0.0219g Co(NO 3 ) 2 Then, 5 mL of 6 mg / mL sodium borohydride was added dropwise while stirring, and stirred in a water bath at 200°C until the reaction was completed. The product was separated and washed with deionized water until neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0054] The catalyst was used for electrochemical testing as in Example 1. The current density of the ethylene glycol oxidation peak was 37.51 mA·cm -2 The current density of the intermediate product CO oxidation peak is 21.13 mA cm -2 ; Catalyst I f / I bAfter 200 cycles of cycle stability testing, the current density of the catalyst in Comparative Example 1 dropped to 25.64 mA·cm -2 , the attenuation rate is 31.6%.

[0055] Comparative Example 2

[0056] S1.8g lithium fluoride was added to 100mL 9mol / L hydrochloric acid solution and mixed well. 6.4g Ti 3 AlC 2 , ultrasonic dispersion, etching in a water bath at 50°C for 30h, separation, and washing the obtained product with deionized water until neutral to obtain a flaky MXene material;

[0057] 5 g of flaky MXene material was dispersed in a 2 mol / L hydrochloric acid solution, 2 g of a 50 wt% aminonitrile aqueous solution was added, stirred, separated, the obtained product was washed with deionized water until neutral, and calcined at 550°C to obtain a nitrogen-doped flaky MXene material;

[0058] S2. The pH value of 80 mL of 3.5 mg / mL sodium molybdate solution was adjusted to 6.5 with hydrochloric acid solution, 0.7 g of L-cysteine ​​was added, and after ultrasonic treatment, 0.616 g of nitrogen-doped flaky MXene was added, and the mixture was hydrothermally reacted at 200 ° C for 24 h, cooled to room temperature, separated, and the obtained product was washed with ethanol and deionized water, and dried to obtain a nitrogen-doped flaky MXene / molybdenum disulfide composite material;

[0059] S3. 0.58 g of nitrogen-doped flaky MXene / MoS2 composite material was ultrasonically dispersed in 30 mL of deionized water and 0.0213 g of H 2 PdCl 4 、0.0188g Cu(NO 3 ) 2 , 0.0219g Co(NO 3 ) 2 Then, 5 mL of 6 mg / mL sodium borohydride was added dropwise while stirring, and stirred in a water bath at 200°C until the reaction was completed. The product was separated and washed with deionized water until neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0060] The catalyst was used for electrochemical testing as in Example 1. The current density of the ethylene glycol oxidation peak was 28.69 mA·cm -2 The current density of the intermediate product CO oxidation peak is 15.86 mA cm -2 ; Catalyst I f / I b After 200 cycles of cycle stability testing, the current density of the catalyst in Comparative Example 2 dropped to 18.65 mA cm-2 , the attenuation rate is 35.0%.

[0061] Comparative Example 3

[0062] S1. Add 3 g of carbon nanotubes to a mixed acid consisting of 50 mL of concentrated nitric acid and concentrated sulfuric acid, the volume ratio of concentrated nitric acid to concentrated sulfuric acid being 1:1, and react under reflux in an oil bath at 85°C. After the reaction is completed, cool to room temperature, separate, and wash the obtained product with deionized water until it is neutral, and dry, thereby completing the acid treatment of the carbon nanotubes;

[0063] S2. The pH value of 80 mL of 3.5 mg / mL sodium molybdate solution was adjusted to 6.5 with hydrochloric acid solution, 0.7 g of L-cysteine ​​was added, and after ultrasonic treatment, 0.616 g of carbon nanotubes was added, and the reaction was hydrothermally reacted at 200 ° C for 24 h, cooled to room temperature, separated, and the obtained product was washed with ethanol and deionized water, and dried to obtain a carbon nanotube / molybdenum disulfide composite material;

[0064] S3. 0.58 g of carbon nanotube / molybdenum disulfide composite material was ultrasonically dispersed in 30 mL of deionized water, and 0.0213 g of H 2 PdCl 4 、0.0188g Cu(NO 3 ) 2 , 0.0219g Co(NO 3 ) 2 Then, 5 mL of 6 mg / mL sodium borohydride was added dropwise while stirring, and stirred in a water bath at 200°C until the reaction was completed. The product was separated and washed with deionized water until neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0065] The catalyst was used for electrochemical testing as in Example 1. The current density of the ethylene glycol oxidation peak was 25.68 mA cm -2 The current density of the intermediate product CO oxidation peak is 11.96 mA cm -2 ; Catalyst I f / I b After 200 cycles of cyclic stability testing, the current density of the catalyst in Comparative Example 3 dropped to 20.31 mA·cm -2 , the attenuation rate is 20.9%.

[0066] Comparative Example 4

[0067] S1.8g lithium fluoride was added to 100mL 9mol / L hydrochloric acid solution and mixed well. 6.4g Ti 3 AlC 2, ultrasonic dispersion, etching in a water bath at 50°C for 30h, separation, and washing the obtained product with deionized water until neutral to obtain a flaky MXene material;

[0068] S2. Add 3 g of carbon nanotubes to a mixed acid consisting of 50 mL of concentrated nitric acid and concentrated sulfuric acid, wherein the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:1, and react under reflux in an oil bath at 85°C. After the reaction is completed, cool to room temperature, separate, and wash the obtained product with deionized water until it is neutral, and dry, thereby completing the acid treatment of the carbon nanotubes;

[0069] 4.8 g of flaky MXene was dispersed in deionized water, and 0.8 g of carbon nanotubes was dispersed in ethanol. Then, the flaky MXene aqueous solution and the carbon nanotube alcohol solution were mixed, stirred at room temperature, separated, and vacuum dried to obtain flaky MXene / carbon nanotubes.

[0070] S3. The pH value of 80 mL of 3.5 mg / mL sodium molybdate solution was adjusted to 6.5 with hydrochloric acid solution, 0.7 g of L-cysteine ​​was added, and after ultrasonic treatment, 0.616 g of flaky MXene / carbon nanotubes was added, and the reaction was hydrothermally reacted at 200 ° C for 24 h, cooled to room temperature, separated, and the obtained product was washed with ethanol and deionized water, and dried to obtain a flaky MXene / carbon nanotube / molybdenum disulfide composite material;

[0071] S4. 0.58 g of MXene / carbon nanotube / molybdenum disulfide composite material was ultrasonically dispersed in 30 mL of deionized water, and 0.0213 g of H 2 PdCl 4 、0.0188g Cu(NO 3 ) 2 , 0.0219g Co(NO 3 ) 2 Then, 5 mL of 6 mg / mL sodium borohydride was added dropwise while stirring, and stirred in a water bath at 200°C until the reaction was completed. The product was separated and washed with deionized water until neutral, and freeze-dried to obtain a Pd-based alloy supported catalyst.

[0072] The catalyst was used for electrochemical testing as in Example 1. The current density of the ethylene glycol oxidation peak was 35.61 mA·cm -2 The current density of the intermediate product CO oxidation peak is 16.89 mA cm -2 ; Catalyst I f / I b After 200 cycles of cycle stability testing, the current density of the catalyst in Comparative Example 4 dropped to 20.50 mA·cm -2 , the attenuation rate is 42.4%.

[0073] Finally, it should be noted that the above-mentioned embodiments only express several implementation methods of the present invention and are not intended to limit the invention. For those skilled in the art, any modification, equivalent replacement, improvement, etc. made without departing from the concept of the present invention should be included in the protection scope of the invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a Pd-based alloy supported catalyst, characterized in that: The following steps are involved: S1. dispersing the flaky MXene material in an acidic solution, adding a nitrogen-containing precursor, stirring, separating, washing the obtained product with deionized water until neutral, and calcining to obtain a nitrogen-doped flaky MXene material; S2. Dispersing nitrogen-doped flaky MXene in deionized water, adding carbon nanotubes to a mixed acid of concentrated nitric acid and concentrated sulfuric acid, and reacting in an oil bath under reflux, cooling to room temperature after the reaction is completed, separating, washing the obtained product with deionized water until neutral, and drying, thus completing the acid treatment of the carbon nanotubes, dispersing the acid-treated carbon nanotubes in ethanol, and then mixing the nitrogen-doped flaky MXene aqueous solution and the carbon nanotube alcohol solution, stirring at room temperature, separating, and vacuum drying to obtain nitrogen-doped flaky MXene / carbon nanotubes; S3. The pH value of the sodium molybdate solution is adjusted to acidic with a hydrochloric acid solution, L-cysteine ​​is added, and after ultrasonic treatment, nitrogen-doped flaky MXene / carbon nanotubes are continuously added, hydrothermally reacted, cooled to room temperature, separated, and the obtained product is washed with ethanol and deionized water, and dried to obtain a nitrogen-doped flaky MXene / carbon nanotube / molybdenum disulfide composite material; S4. Ultrasonic dispersion of nitrogen-doped MXene / carbon nanotube / molybdenum disulfide composite material in deionized water, adding H2PdCl4, Cu(NO3)2, Co(NO3)2, and then dropping a reducing agent while stirring, stirring in a water bath until the reaction is complete, separating, washing the obtained product with deionized water until neutral, and freeze-drying to obtain a Pd-based alloy supported catalyst; In step S1, the acidic solution is a hydrochloric acid solution with a concentration of 1-3 mol / L; the nitrogen-containing precursor is an aminonitrile aqueous solution with a concentration of 50 wt%; the mass ratio of the nitrogen-containing precursor to the flaky MXene material is 1:(2-3); and the calcination temperature is 500-600°C.

2. The preparation method according to claim 1, characterized in that: In step S1, the specific operation of preparing the flaky MXene material is: etching Ti3AlC2 with a mixed solution of lithium fluoride and hydrochloric acid, ultrasonic dispersion, water bath etching, separation, and washing the obtained product with deionized water until neutral to obtain a flaky MXene material; The concentration of hydrochloric acid in the mixed solution of lithium fluoride and hydrochloric acid is 8-10 mol / L, and the concentration of lithium fluoride is 75-90 g / L; the mass ratio of lithium fluoride to Ti3AlC2 is 1:(0.6-0.9); and the etching is performed under heating in a water bath at 45-55°C for 24-36 hours.

3. The preparation method according to claim 1, characterized in that: In step S2, the volume ratio of concentrated nitric acid to concentrated sulfuric acid in the mixed acid is 1:(0.5-2.5); the ratio of the amount of carbon nanotubes to the amount of mixed acid is 1g:(10-50)mL; and the oil bath temperature is 80-120°C.

4. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of nitrogen-doped flaky MXene to acid-treated carbon nanotubes is (4-8):

1.

5. The preparation method according to claim 1, characterized in that: In step S3, the concentration of the sodium molybdate solution is 3.5 mg / mL; the concentration of L-cysteine ​​is 8.75 mg / mL; the mass ratio of nitrogen-doped flaky MXene / carbon nanotubes to sodium molybdate is (1.2-2.8):1; the hydrothermal reaction temperature is 180-200°C, and the reaction time is 24-36h.

6. The preparation method according to claim 1, characterized in that: In step S4, the concentration of the nitrogen-doped flaky MXene / carbon nanotube / molybdenum disulfide composite material is 1-30 mg / mL; The mass ratio of the amount of nitrogen-doped MXene / carbon nanotube / molybdenum disulfide composite material to the total amount of H2PdCl4, Cu(NO3)2, and Co(NO3)2 is (5-15):1; The molar ratio of H2PdCl4, Cu(NO3)2, and Co(NO3)2 is 1:1:(1.2-1.5).

7. The preparation method according to claim 1, characterized in that: The reducing agent is sodium borohydride solution with a concentration of 5-15 mg / mL.

8. A Pd-based alloy supported catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the Pd-based alloy supported catalyst as claimed in claim 8 in a direct ethylene glycol fuel cell.