A method for preparing an anode catalyst for an alkaline system fuel cell

Abstract

The application discloses a preparation method of an anode catalyst of an alkaline system fuel cell, and comprises the following steps: dissolving a precursor platinum salt and a precursor bismuth salt in deionized water to obtain a precursor solution A; performing ultrasonic treatment and stirring on the precursor solution A, and protecting the precursor solution A by using a double-pipe nitrogen gas protection device; in a heating process, dissolving sodium borohydride in deionized water to obtain a solution B, and adding the solution B into the precursor solution A to obtain a reaction solution C; placing the reaction solution C for 2 hours, cleaning the obtained sample, and adding methanol to disperse the sample to obtain a solution D; dissolving a precursor zinc salt and a surfactant polyvinylpyrrolidone in methanol to obtain a solution E and performing stirring on the solution E; dissolving dimethyl imidazole in methanol to obtain a solution F; slowly adding the solution D into the solution E, and then adding the solution F to obtain a reaction solution G; placing the reaction solution G for 12 hours; after the reaction is completed, cleaning the obtained sample, and drying the sample at 60 DEG C for 12 hours to obtain a PtBi@ZIF-8 composite structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials, and particularly relates to a preparation method of an anode catalyst for an alkaline system fuel cell. BACKGROUND

[0002] Direct methanol fuel cells (DMFCs) have attracted much attention due to their high energy density, environmentally friendly products, simple manufacturing process, and small size and portability. Pt is used as a high-efficiency catalyst in DMFCs to accelerate electrochemical reactions such as methanol oxidation and oxygen reduction by reducing the activation energy, thereby greatly improving the performance and energy conversion efficiency of the cell. However, the limited reserves and high cost of Pt have severely limited its widespread application in the commercial development of DMFCs. In view of the shortage of Pt-based catalysts and the high cost, researchers have made contributions by developing non-platinum catalyst materials, optimizing the structure of platinum-based catalysts, and improving the utilization rate of platinum, aiming to reduce costs and ensure performance and strive to make breakthroughs in related technologies. The catalytic performance of methanol fuel cells can be improved by optimizing the structure to reduce mass transfer resistance, changing the morphology to increase active sites, and regulating the components to enhance synergistic effects, thereby accelerating electrochemical reactions and improving cell efficiency and stability. The combination of PtBi nanomaterials and ZIF-8 can significantly improve the catalytic performance of direct methanol fuel cells. The principle lies in the fact that PtBi nanomaterials have good catalytic activity, and ZIF-8 has a unique porous structure and high specific surface area. This combination allows the active sites of PtBi nanomaterials to be fully exposed, increasing the contact area with reactants, while the pore structure of ZIF-8 facilitates mass transfer, accelerating the reaction process. The two work together to promote the efficient performance of electrochemical reactions in direct methanol fuel cells, thereby improving catalytic performance. Currently, methanol oxidation catalysis cannot precisely control path selection, and the carbon-containing intermediates and byproducts produced in the process are easily adsorbed on the Pt surface, occupying active sites and causing catalyst poisoning and deactivation. Incomplete electron transfer also reduces the utilization rate of methanol, and DMFCs do not reach the theoretical capacity. PtBi alloys have many problems in the field of methanol oxidation. For example, it is difficult to precisely control the morphology and atomic coordination environment of PtBi alloys, and the synergistic mechanism between elements is not clear, making it difficult to optimize the design. In addition, the stability of PtBi alloys in the reaction is insufficient and is easily affected by reaction conditions, which leads to performance degradation, which is related to changes in the surface structure and adsorption of intermediate products. SUMMARY

[0003] The technical problem solved by the application is to provide a preparation method of an anode catalyst for an alkaline system fuel cell.

[0004] This application addresses the shortcomings of existing technologies and solves several defects of Pt elements, such as high cost and easy aggregation leading to a reduction in active sites. It provides a method for preparing an anode catalyst for an alkaline fuel cell by combining a Pt-based catalyst with a metal-organic framework (MOF). The unique spatial structure of the MOF effectively disperses Pt particles, increasing the number of active sites. From a microscopic perspective, the ordered pores of the MOF facilitate mass transport and promote the kinetic processes in the methanol fuel cell. Its stable framework structure also enhances the stability of the Pt-based catalyst, inhibiting Pt particle growth and loss. This combination optimizes the thermodynamic environment, allowing for a more complete reaction between the Pt-based catalyst and methanol oxidation, significantly improving fuel cell performance.

[0005] Technical solution:

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] A method for preparing an anode catalyst for an alkaline fuel cell specifically includes the following steps:

[0008] Step 1: Dissolve the precursor platinum salt and precursor bismuth salt in 35 mL of deionized water at a molar ratio of 1-2:1-2, sonicate for 30 min to obtain precursor solution A, and stir at a speed of 500 r / min for 20 min.

[0009] Step 2: Use a double-row tube with nitrogen gas for protection, and control the rotation speed at 500 r / min at 60℃ to heat the solution.

[0010] A. After 30 minutes, adjust the rotation speed to 1500 r / min, dissolve 18.195 mg of sodium borohydride in 10 mL of deionized water to obtain solution B, sonicate for 5-10 seconds, and quickly inject 3 mL of the sonicated solution B into the heated precursor solution A, while maintaining the rotation speed at 1500 r / min.

[0011] The reaction solution C was obtained by stirring at 1500 r / min for 1 min.

[0012] Step 3: Let the reaction solution C stand at 60°C for 2 hours to obtain the sample, wash the obtained sample, and disperse it in 5 mL of methanol to obtain solution D;

[0013] Step 4: Dissolve the precursor zinc salt and 0.2g of surfactant polyvinylpyrrolidone in 10mL of methanol to obtain solution E and stir at 500r / min for 2h. During stirring, add solution D dropwise to solution E to obtain reaction solution F. Dissolve dimethylimidazole in 15mL of methanol to obtain solution G. Then add solution G to solution F to obtain reaction solution H.

[0014] Fifth step: after the reaction solution H is stirred for 2h, the reaction solution H is again placed for 12h, after the reaction is completed, the obtained sample is cleaned, and is dried at 60℃ for 12h to obtain the PtBi@ZIF-8 composite structure.

[0015] Further, in the precursor solution A, the concentration of platinum ions is 1.428mmol / L, the concentration of bismuth ions is 0.714

[0016] mmol / L, and in the solution E, the concentration of the surfactant is 0.345mmol / L, in the precursor solution E, the concentration of zinc ions is 25mmol / L.

[0017] Further, in the fourth step, the molar ratio of zinc ions to dimethyl imidazole is 1:4.

[0018] Further, the precursor platinum salt is chloroplatinic acid hexahydrate, the precursor bismuth salt is bismuth ammonium citrate, and the precursor zinc salt is zinc nitrate hexahydrate.

[0019] Further, in the second step and the third step, the reaction temperature is 60℃, in the fourth step and the fifth step, the reaction temperature is room temperature, and the entire reaction time is 17-20h.

[0020] Further, in the fifth step, the solvent for cleaning the sample is methanol.

[0021] Original explanation: the Kirkendall effect plays an important role in this process, atomic diffusion migration leads to rearrangement of the internal structure of the alloy, and then a unique aerogel structure is formed; in the synthesis of the PtBi@ZIF-8 composite structure, PVP effectively controls the crystal growth direction and morphology by virtue of its surface activity and steric hindrance effect, and promotes the close combination between PtBi and ZIF-8; for the stability mechanism of the microenvironment of PtBi, it is synergistically affected by multiple factors such as surface energy distribution, electronic structure and chemical bonding; by precisely controlling the reaction temperature, concentration and reaction time conditions, fine adjustment of the microenvironment of the PtBi alloy is realized, and the stability and performance in practical application are greatly improved.

[0022] Beneficial effects:

[0023] The application provides a preparation method of an anode catalyst of an alkaline system fuel cell.

[0024] Beneficial effects:

[0025] 1. The alloy prepared by the method is composed of Pt and Bi elements.

[0026] 2. The PtBi@ZIF-8 composite material prepared by the method plays a key role in the improvement of the structure; the wrapping of ZIF-8 enhances the resistance to CO, reduces the adsorption and poisoning of CO; the structure promotes the optimization of the methanol oxidation reaction path and improves the reaction activity; at the same time, the structural stability is enhanced, and good performance is maintained in long-term use;

[0027] 3. Due to the change of the catalytic environment space, the selectivity and kinetics of the electrochemical reaction can be affected, and the structure-activity relationship between the Pt-based alloy and MOR is revealed, thereby providing further guidance for synthesizing new and efficient Pt-based alloy catalysts;

[0028] 4. In the experimental test process, the mass activity of the Pt-based alloy measured by cyclic voltammetry in 1.0M KOH+1.0M CH3OH electrolyte solution is 5.5Amg -1 , which is 18.3 times the result 0.3Amg -1 measured by commercial Pt / C; the remaining activity of the Pt-based alloy after 10000s of stability test is 2.75Amg -1 , which is much higher than that of commercial Pt / C (close to 0) measured by chronoamperometry in 1.0M KOH+1.0M CH3OH electrolyte solution for 3600s; therefore, it can be seen that the prepared Pt-based alloy has high activity and stability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a scanning electron microscope image of the PtBi@ZIF-8 composite material obtained in Example 1 of the present application, wherein a is the structure morphology of the PtBi@ZIF-8 composite material at high magnification, and b is the structure morphology of the PtBi@ZIF-8 composite material at low magnification;

[0030] Figure 2 is a curve diagram of the activation of the PtBi@ZIF-8 composite material obtained in Example 1 of the present application and the commercial Pt / C catalyst in 1.0M KOH electrolyte solution, wherein the red line represents the methanol oxidation reaction catalytic activation curve of the PtBi@ZIF-8 composite material, and the black line represents the methanol oxidation reaction catalytic activation curve of the commercial Pt / C catalyst;

[0031] Figure 3 is a cyclic voltammetry curve of the methanol oxidation reaction catalytic activity of the PtBi@ZIF-8 composite material obtained in Example 1 of the present application and the commercial Pt / C catalyst, wherein the red line represents the cyclic voltammetry curve of the methanol oxidation reaction catalytic activity of the PtBi@ZIF-8 composite material, and the black line represents the cyclic voltammetry curve of the methanol oxidation reaction catalytic activity of the commercial Pt / C catalyst;

[0032] Figure 4 is the chronoamperogram of the catalytic activity of the PtBi@ZIF-8 composite material and the commercial Pt / C catalyst in the basic methanol oxidation reaction, wherein the red line is the chronoamperogram of the catalytic activity of the PtBi@ZIF-8 composite material in the methanol oxidation reaction, and the black line is the chronoamperogram of the catalytic activity of the commercial Pt / C catalyst in the methanol oxidation reaction. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0034] Embodiment 1

[0035] A preparation method of an anode catalyst of an alkaline system fuel cell, specifically comprising the following steps:

[0036] First step: dissolve the precursor platinum salt and the precursor bismuth salt in 35 mL of deionized water according to a molar ratio of 2:1, and ultrasonic for 30 min to obtain a precursor solution A and stir, and control the stirring speed to be 500 r / min and the stirring time to be 20 min;

[0037] Second step: use double-tube nitrogen protection, control the stirring speed to be 500 r / min at a temperature of 60 ℃, and heat the solution

[0038] A 30 min; adjust the stirring speed to be 1500 r / min, dissolve 18.195 mg of sodium borohydride in 10 mL of deionized water to obtain a solution B, ultrasonic for 5 s, quickly inject 3 mL of the ultrasonic solution B into the heated precursor solution A, and stir for 1 min at a stirring speed of 1500 r / min to obtain a reaction solution C;

[0039] Third step: place the reaction solution C at a temperature of 60 ℃ for 2 hours to obtain a sample, wash the obtained sample, and disperse the sample in 5 mL of methanol to obtain a solution D;

[0040] Fourth step: dissolve the precursor zinc salt and 0.2 g of the surfactant polyvinylpyrrolidone in 10 mL of methanol to obtain a solution E and stir, and control the stirring speed to be 500 r / min and the stirring time to be 2 h, drop the solution D into the solution E during the stirring process to obtain a reaction solution F, dissolve dimethylimidazole in 15 mL of methanol to obtain a solution G, and drop the solution G into the solution F to obtain a reaction solution H;

[0041] Fifth step: After the reaction solution H is stirred for 2h, the reaction solution H is again left to stand for 12h, and after the reaction is completed, the obtained sample is cleaned and dried at 60℃ for 12h to obtain the PtBi@ZIF-8 composite structure.

[0042] The reaction temperature in the second step and the third step is 60℃, and the reaction temperature in the fourth step and the fifth step is room temperature, and the whole reaction time is 17-20h.

[0043] In the precursor solution A, the concentration of platinum ions is 1.428mmol / L, and the concentration of bismuth ions is 0.714mmol / L, and in the solution E, the concentration of the surfactant is 0.345mmol / L, and in the precursor solution E, the concentration of zinc ions is 25mmol / L.

[0044] The precursor platinum salt is chloroplatinic acid hexahydrate; the precursor bismuth salt is bismuth ammonium citrate; and the precursor zinc salt is zinc nitrate hexahydrate.

[0045] The PtBi@ZIF-8 composite material obtained above is observed by a scanning electron microscope (SEM), and as shown in FIG. 1, the morphology of the obtained PtBi@ZIF-8 composite material is a nano-aerogel. Figure 1

[0046] Methanol oxidation reaction (MOR) catalytic activity test:

[0047] (1) Preparation of a catalytic electrode

[0048] The PtBi@ZIF-8 composite material prepared above and a commercial Pt / C catalyst are dispersed in 0.5mL water, 0.5mL anhydrous ethanol, 0.3mg carbon black and 30μL Nafion solution, and then ultrasonic treatment is performed for 30min to form a uniform ink. The Pt loading is maintained at 2μg / μL. 6.5μL of the ink is dropped onto a glassy carbon electrode with an area of 0.07065cm 2 , and then the glassy carbon electrode is left to dry at room temperature for use.

[0049] (2) MOR test

[0050] The MOR test is performed at a scan rate of 50mV / s in 1.0mol / L KOH+1.0mol / L CH3OH. The long-term stability of the prepared sample is determined by chronoamperometry in 1.0mol / L KOH solution containing 1.0mol / L CH3OH. For comparison, a commercial Pt / C (20wt% of Pt nanoparticles loaded on Vulcan XC-72 carbon, Aladdin Company) is also prepared by the same preparation steps and test methods.

[0051] ​The MOR performance of the PtBi@ZIF-8 composite material obtained by the example was tested by using a CTS workstation in a three-electrode cell system. In the three-electrode system, a saturated calomel electrode and a Pt mesh were used as the reference electrode and the counter electrode, respectively.

[0052] Figure 3 The PtBi@ZIF-8 composite material for the example was subjected to cyclic voltammetry in a 1.0 mol / L KOH solution containing 1.0 mol / L CH3OH, at a potential range of -0.9 V to 0.2 V (relative to a saturated calomel electrode, SCE), and a scan rate of 50 mV / s. The red line in the figure represents the cyclic voltammetry curve of the methanol oxidation reaction catalytic activity of the PtBi@ZIF-8 composite material, and the black line represents the cyclic voltammetry curve of the methanol oxidation reaction catalytic activity of the commercial Pt / C catalyst. From Figure 4 It can be concluded that the MOR activity of the PtBi@ZIF-8 composite material is 5.5 A mg -1 , while the activity of the commercial Pt / C is only 0.3 A mg -1 .

[0053] Figure 4 The PtBi@ZIF-8 composite material for the example was subjected to a potential change test after 3600 s in a 1.0 mol / L KOH solution containing 1.0 mol / L CH3OH, at a potential of -0.29 V (relative to a saturated calomel electrode, SCE). The red line in the figure represents the current curve of the methanol oxidation reaction catalytic activity of the PtBi@ZIF-8 composite material, and the black line represents the current curve of the methanol oxidation reaction catalytic activity of the commercial Pt / C catalyst. From Figure 4 It can be concluded that after the 3600 s stability test, the activity of the PtBi@ZIF-8 composite material still maintains at 2.75 A mg -1 . In comparison, after the 3600 s stability test, the activity of the commercial Pt / C tends to be 0, i.e., loses activity.

[0054] Example 2

[0055] A preparation method of an anode catalyst for an alkaline system fuel cell, specifically comprising the following steps:

[0056] First step: Dissolve the precursor platinum salt and the precursor bismuth salt in 35 mL of deionized water according to a molar ratio of 1:1, and ultrasonic for 30 min to obtain a precursor solution A and stir, control the stirring speed at 500 r / min, and the stirring time at 20 min;

[0057] Second step: using double row pipe to protect nitrogen, control the speed at 500 r / min at 60℃, heat solution A for 30 min; adjust the speed to 1500 r / min, dissolve 18.195 mg sodium borohydride in 10 mL deionized water to obtain solution B, ultrasonic for 10 s, take 3 mL of the ultrasonic solution B and quickly inject into the heated precursor solution A, stir for 1 min at the speed of 1500 r / min to obtain reaction solution C;

[0058] Third step: reaction solution C is placed at 60℃ for 2 hours to obtain a sample, the obtained sample is washed and dispersed in 5 mL of methanol to obtain solution D;

[0059] Fourth step: dissolve the precursor zinc salt and 0.2 g of surfactant polyvinylpyrrolidone in 10 mL of methanol to obtain solution E and stir at a speed of 500 r / min for 2 h, add solution D dropwise to solution E during stirring to obtain reaction solution F, dissolve dimethylimidazole in 15 mL of methanol to obtain solution G, and add solution G dropwise to solution F to obtain reaction solution H;

[0060] Fifth step: after stirring reaction solution H for 2 h, reaction solution H is placed for 12 hours, and after the reaction is completed, the obtained sample is washed and dried at 60℃ for 12 hours to obtain PtBi@ZIF-8 composite structure.

[0061] The reaction temperature in the second step and the third step is 60℃, the reaction temperature in the fourth step and the fifth step is room temperature, and the whole reaction time is 17-20 hours.

[0062] Example 3:

[0063] A preparation method of an anode catalyst for an alkaline system fuel cell, specifically comprising the following steps:

[0064] First step: dissolve the precursor platinum salt: precursor bismuth salt according to the molar ratio 1:2 in 35 mL of deionized water, ultrasonic for 30 min to obtain precursor solution A and stir at a speed of 500 r / min for 20 min;

[0065] Second step: use double row pipe to protect nitrogen, control the speed at 500 r / min at 60℃, heat solution A for 30 min; adjust the speed to 1500 r / min, dissolve 18.195 mg sodium borohydride in 10 mL deionized water to obtain solution B, ultrasonic for 8 s, take 3 mL of the ultrasonic solution B and quickly inject into the heated precursor solution A, stir for 1 min at the speed of 1500 r / min to obtain reaction solution C;

[0066] The third step: the reaction solution C is placed at a temperature of 60 DEG C for 2 hours to obtain a sample, the sample is cleaned, and methanol is added to disperse to obtain a solution D;

[0067] The fourth step: a precursor zinc salt and 0.2g of a surfactant polyvinylpyrrolidone are dissolved in 10mL of methanol to obtain a solution E and stirring is carried out at a speed of 500r / min for 2h, and the solution D is added dropwise into the solution E to obtain a reaction solution F, dimethylimidazole is dissolved in 15mL of methanol to obtain a solution G, and the solution G is added dropwise into the solution F to obtain a reaction solution H;

[0068] The fifth step: after the reaction solution H is stirred for 2h, the reaction solution H is placed for 12 hours, and after the reaction is completed, the sample is cleaned,

[0069] 60 DEG C drying for 12 hours to obtain a PtBi@ZIF-8 composite structure.

[0070] The reaction temperature in the second step and the third step is 60 DEG C, the reaction temperature in the fourth step and the fifth step is room temperature, and the whole reaction time is 17-20 hours.

[0071] In conclusion, the PtBi@ZIF-8 composite material prepared by the preparation method has good catalytic activity for methanol oxidation reaction, i.e., good MOR activity and excellent stability, and the preparation process is simple, low in cost and convenient for industrialized scale production.

[0072] The above description has fully disclosed the specific embodiments of the present application. It should be pointed out that any modification made by the skilled in the art to the specific embodiments of the present application does not deviate from the scope of the claims of the present application. Correspondingly, the scope of the claims of the present application is not limited to the foregoing specific embodiments.

Claims

1. A method for preparing an anode catalyst for an alkaline fuel cell, characterized in that, The specific steps are as follows: Step 1: Dissolve the precursor platinum salt and precursor bismuth salt in 35 mL of deionized water at a molar ratio of 1-2:1-2, sonicate for 30 min to obtain precursor solution A, and stir at a speed of 500 r / min for 20 min. Step 2: Using a double-row tube with nitrogen gas for protection, heat solution A for 30 minutes at 60℃ with a rotation speed of 500 r / min; adjust the rotation speed to 1500 r / min, dissolve 18.195 mg of sodium borohydride in 10 mL of deionized water to obtain solution B, sonicate for 5-10 s, take 3 mL of sonicated solution B and quickly inject it into the heated precursor solution A, stir for 1 minute at a rotation speed of 1500 r / min to obtain reaction solution C; Step 3: Let the reaction solution C stand at 60°C for 2 hours to obtain the sample, wash the obtained sample, and disperse it in 5 mL of methanol to obtain solution D; Step 4: Dissolve the precursor zinc salt and 0.2 g of surfactant polyvinylpyrrolidone in 10 mL of methanol to obtain solution E and stir at 500 r / min for 2 h. During stirring, add solution D dropwise to solution E to obtain reaction solution F. Dissolve dimethylimidazole in 15 mL of methanol to obtain solution G. Then add solution G to solution F to obtain reaction solution H. Step 5: After stirring the reaction solution H for 2 hours, let the reaction solution H stand for 12 hours. After the reaction is complete, wash the obtained sample and dry it at 60℃ for 12 hours to obtain the PtBi@ZIF-8 composite structure. In the fourth step, the molar ratio of zinc ions to dimethylimidazole is 1:4; In the precursor solution A, the concentration of platinum ions is 1.428 mmol / L and the concentration of bismuth ions is 0.714 mmol / L. In solution E, the concentration of surfactant is 0.345 mmol / L and the concentration of zinc ions is 25 mmol / L. The reaction temperature in the second and third steps is 60°C, and the reaction temperature in the fourth and fifth steps is room temperature. The entire reaction time is 17-20 hours.

2. The method for preparing an alkaline fuel cell anode catalyst according to claim 1, characterized in that: The precursor platinum salt is chloroplatinic acid hexahydrate; the precursor bismuth salt is bismuth ammonium citrate; and the precursor zinc salt is zinc nitrate hexahydrate.

3. The method for preparing an alkaline fuel cell anode catalyst according to claim 1, characterized in that: The solvent used for sample cleaning in the fifth step is methanol.

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