Alloying modification method for platinum catalyst and use thereof

Abstract

Provided is an alloying modification method for a platinum catalyst. The method comprises: mixing a 5% platinum-on-carbon catalyst and a phytic acid solution until uniform, and then freeze-drying same; performing primary pyrolysis, a sulfuric acid treatment, cleaning with ultrapure water, suction filtration and drying to obtain a powder; and adding ferrous sulfate and 1,10-phenanthroline thereto, and performing secondary pyrolysis, a sulfuric acid treatment, cleaning with ultrapure water, suction filtration and drying to obtain an alloying-modified carbon-based catalyst. By subjecting platinum metal and a transition metal to alloying, the activity and stability of the catalyst are effectively improved, the amount of the noble metal platinum is reduced, and the manufacturing costs of the catalyst are effectively lowered. The obtained alloying-modified carbon-based catalyst can be used for preparing primary zinc-air batteries and rechargeable zinc-air batteries.

Description

Alloying modification method of platinum catalyst and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical catalysis, in particular to an alloying modification method of platinum catalyst and application thereof. BACKGROUND

[0002] The performance of hydrogen fuel cells mainly depends on the air electrode, which undergoes a slow oxygen reduction reaction (ORR) during discharging, consuming electrons from the fuel to directly convert chemical energy into electrical energy. There are many types of cathode catalysts for fuel cells at present, and high catalytic activity, high stability and low cost have become the main direction of synthesizing catalysts. In current research, fuel cell catalysts are mainly divided into two categories: one is noble metal catalyst material, including Pt, Pd, Au, etc.; the other is non-noble metal catalyst, including transition metals and heteroatom-doped carbon materials. Using noble metals as catalysts can significantly improve the electrocatalytic performance of ORR, but noble metals are not only expensive, but also have poor resistance to poisoning and poor stability. Using non-noble metal catalysts can effectively reduce the cost of catalysts, but they have low catalytic activity, poor stability (for example: Fe-N-C catalysts may have problems such as deactivation of Fe active sites, corrosion of C, and collapse of the three-phase interface of the catalyst during the operation of hydrogen fuel cells), difficulty in mass production, high requirements for working environment (for example: in high temperature or high humidity environment, the stability and activity of some non-noble metal catalysts may decrease significantly), and other problems restrict the application of non-noble metal catalysts in fuel cells. SUMMARY

[0003] The purpose of the present application is to provide an alloying modification method of platinum catalyst.

[0004] The purpose of the present application is achieved by the following technical solutions.

[0005] The alloying modification method of platinum catalyst comprises the following steps:

[0006] Step S1, uniformly mix 5% platinum carbon catalyst, phytic acid solution and deionized water, stir, then freeze dry the mixed solution;

[0007] Step S2, pyrolyze the powder after freeze drying in step S1 once, and then treat the product after the first pyrolysis with sulfuric acid, then wash and filter with ultrapure water, and then dry;

[0008] Step S3, uniformly mix the dried powder in step S2 with ferrous sulfate and 1,10-phenanthroline, and then pyrolyze twice;

[0009] Step S4, the product of secondary pyrolysis in step S3 is treated with sulfuric acid, then washed with ultrapure water, filtered and dried to obtain the alloyed modified carbon-based catalyst (i.e. Pt-Fe-NPC catalyst).

[0010] Further optimization, the phytic acid solution in step S1 is a phytic acid solution with a mass concentration of 70%; the mass-volume ratio of 5% platinum carbon catalyst, phytic acid solution and deionized water is: 0.1-0.3g: 0.5-1.5mL: 8-12mL.

[0011] Further optimization, the stirring time of 5% platinum carbon catalyst and phytic acid solution in step S1 is 12-24h.

[0012] Further optimization, the freeze-drying step in step S1 is specifically: the mixed solution is pre-frozen at a temperature of-15℃ to-10℃ for 2h, then placed in a vacuum freeze dryer at a temperature of-55℃ to-45℃ for 12h.

[0013] Further optimization, the specific steps of the first pyrolysis in step S2 are: heating at a rate of 3-5℃ / min to 800-1000℃, then holding for 1-2h to complete the first pyrolysis.

[0014] Further optimization, the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline in step S3 is 30-50mg: 0.012-0.014mg: 0.026-0.028mg.

[0015] Further optimization, the specific steps of the second pyrolysis in step S3 are: heating at a rate of 3.5-4.5℃ / min to 800-1000℃, then holding for 1-2h to complete the second pyrolysis.

[0016] Further optimization, the sulfuric acid treatment in steps S2 and S4 is specifically: the pyrolysis product is placed in a 0.5-2mol / L sulfuric acid solution and stirred at a temperature of 60-80℃ for 10-12h.

[0017] Further optimization, the drying step in steps S2 and S4 is specifically: the sample obtained after filtration is placed in a 55-65℃ air drying oven for 6h.

[0018] Based on the above preparation method, the application also provides an application of the alloyed modified platinum catalyst, specifically the application of Pt-Fe-NPC catalyst in zinc-air batteries. The Pt-Fe-NPC catalyst can be applied in the preparation process of primary zinc-air batteries or rechargeable zinc-air batteries.

[0019] The following are the technical effects possessed by the application:

[0020] The present application not only effectively improves the morphology characteristics of the platinum carbon catalyst, forms a three-dimensional network porous structure precursor (i.e. a hierarchical pore structure with uniform distribution of micropores and mesopores on the surface of the carbon material), facilitates the adsorption of Fe ions by the carbon matrix material and the transportation and transfer of reactants and products, but also effectively ensures the uniform distribution of active sites, avoids the agglomeration of active sites during the pyrolysis process, avoids the problems of site deactivation, poor stability and poor ORR activity caused by uneven active sites, and promotes the sufficient combination of Fe ions and Pt atoms to form a platinum-iron alloy, so that the platinum-iron alloy is used as an anchor point to anchor platinum nanoparticles, avoids the dissolution and migration of platinum nanoparticles during the ORR reaction process, effectively ensures the stability of the catalyst, improves the catalytic activity of the catalyst and the corresponding battery performance.

[0021] The specific surface area of the carbon-based catalyst prepared by alloying modification is as high as 1139.2 m² / g or more, and the catalyst exhibits excellent ORR activity: E 1 / 2 =0.851 V vs.RHE; and when the catalyst is used as a positive electrode oxygen reduction catalyst to assemble a primary zinc-air battery, the battery has a high energy density of not less than 926 Wh / kg-1 Zn. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an SEM image of the alloying modified catalyst prepared in Example 2 of the present application.

[0023] Figure 2 is a TEM image of the alloying modified catalyst prepared in Example 2 of the present application.

[0024] Figure 3 is an HR-TEM image of the alloying modified catalyst prepared in Example 2 of the present application.

[0025] Figure 4 is an XRD image of the alloying modified catalyst prepared in Example 2 of the present application.

[0026] Figure 5 is an XPS image of the alloying modified catalyst prepared in Example 2 of the present application.

[0027] Figure 6 is a N2 adsorption-desorption isotherm graph of the alloying modified catalyst prepared in Example 2 of the present application (wherein the inset is the pore distribution).

[0028] Figure 7 is a comparison of the oxygen reduction LSV of the alloying modified catalyst prepared in Example 2 of the present application and the Pt / C catalyst.

[0029] Figure 8 is a comparison chart of the energy density of a primary zinc-air battery assembled with the alloying modified catalyst prepared in Example 2 of the present application and a Pt / C catalyst.

[0030] Figure 9 is a long-time constant current density discharge chart of a primary zinc-air battery assembled with the alloying modified catalyst prepared in Example 2 of the present application.

[0031] Figure 10 is a comparison chart of the charge / discharge cycle test of a rechargeable zinc-air battery assembled with the alloying modified catalyst prepared in Example 2 of the present application and a Pt / C catalyst. Embodiment of the present application

[0032] The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0033] Example 1:

[0034] An alloying modification method of a platinum catalyst, comprising:

[0035] Step S1, uniformly mix 5% platinum carbon catalyst (a commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.), a phytic acid solution with a mass concentration of 70% (a commercially available product of Shanghai Maikelin Biochemical Technology Co., Ltd.) and deionized water, and stir for 12 h, wherein the amount of platinum carbon catalyst is 0.15 g, the amount of phytic acid solution is 0.5 mL, and the amount of deionized water is 8 mL; then freeze-dry the mixed solution, and the freeze-drying step specifically comprises: pre-freezing the mixed solution at a temperature of -10℃ for 2 h, then placing it in a vacuum freeze dryer, and freeze-drying at a temperature of -45℃ for 12 h.

[0036] Step S2, once pyrolysis is performed on the freeze-dried powder in step S1, specifically: heating at a rate of 3℃ / min to 800℃, and then maintaining the temperature for 2 h to complete the first pyrolysis;

[0037] and the product after the first pyrolysis is treated with sulfuric acid, specifically: placing the product after the first pyrolysis in a 0.5 mol / L sulfuric acid solution, and stirring at a temperature of 60℃ for 12 h;

[0038] Then, the product is washed and suction-filtered with ultrapure water, and then dried, and the drying step specifically comprises: placing the sample obtained after suction-filtration in a 55℃ air drying oven for drying for 6 h.

[0039] Step S3, the dried powder in step S2 is uniformly mixed with ferrous sulfate (AR, commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,10-phenanthroline (99%, commercially available product of Shanghai Titan Science and Technology Co., Ltd.), wherein the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline is 30 mg:0.012 mg:0.026 mg; and then secondary pyrolysis is performed, specifically, the temperature is raised to 800℃ at a rate of 3.5℃ / min, and then the temperature is kept for 2h to complete the secondary pyrolysis.

[0040] Step S4, the product of the secondary pyrolysis in step S3 is treated with sulfuric acid, specifically, the pyrolyzed product is placed in a 0.5 mol / L sulfuric acid solution and stirred at a temperature of 60℃ for 12h;

[0041] Then the product is washed with ultrapure water and then filtered, and then dried, and the drying step is specifically that the filtered sample is placed in a 55℃ air drying oven for 6h to obtain an alloyed modified carbon-based catalyst (i.e., a Pt-Fe-NPC catalyst).

[0042] The specific surface area of the carbon-based catalyst obtained by alloying in this embodiment is 1227.8 m² / g, and the ORR activity is E 1 / 2 =0.834 V vs. RHE.

[0043] Example 2:

[0044] A method for alloying modification of a platinum catalyst, comprising:

[0045] Step S1, 5% platinum carbon catalyst (commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.) and a 70% phytic acid solution (commercially available product of Shanghai Maikelin Biochemical Technology Co., Ltd.) are uniformly mixed with deionized water and stirred for 18h, wherein the amount of platinum carbon catalyst is 0.2g, the amount of phytic acid solution is 1mL, and the amount of deionized water is 10mL; then the mixed solution is freeze-dried, and the freeze-drying step is specifically that the mixed solution is pre-frozen at a temperature of -12℃ for 2h, then placed in a vacuum freeze dryer at a temperature of -50℃ and freeze-dried for 12h.

[0046] Step S2, the freeze-dried powder in step S1 is subjected to primary pyrolysis, specifically, the temperature is raised to 900℃ at a rate of 4℃ / min, and then the temperature is kept for 1.5h to complete the primary pyrolysis;

[0047] and the product of the primary pyrolysis is treated with sulfuric acid, specifically, the product of the primary pyrolysis is placed in a 1 mol / L sulfuric acid solution and stirred at a temperature of 70℃ for 11h;

[0048] Then the sample after filtration is cleaned with ultrapure water and dried, and the drying step is as follows: the sample after filtration is placed in a 60℃ air drying oven for drying for 6h.

[0049] Step S3, the dried powder in step S2 is uniformly mixed with ferrous sulfate (AR, commercially available product from Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,10-phenanthroline (99%, commercially available product from Shanghai Titan Science and Technology Co., Ltd.), and the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline is 40mg:0.013mg:0.027mg; then secondary pyrolysis is performed, and the specific process is as follows: the temperature is raised to 900℃ at a rate of 4℃ / min, and then the temperature is kept for 1.5h to complete the secondary pyrolysis.

[0050] Step S4, the product after secondary pyrolysis in step S3 is treated with sulfuric acid, and the specific process is as follows: the product after pyrolysis is placed in a 1mol / L sulfuric acid solution, and stirred at a temperature of 70℃ for 11h.

[0051] Then the sample after filtration is cleaned with ultrapure water and dried, and the drying step is as follows: the sample after filtration is placed in a 60℃ air drying oven for drying for 6h, thereby obtaining the alloyed modified carbon-based catalyst (i.e., Pt-Fe-NPC catalyst).

[0052] The specific surface area of the carbon-based catalyst obtained by alloying in this embodiment is 1139.2m² / g, and the ORR activity is E 1 / 2 =0.851V vs.RHE.

[0053] The carbon-based catalyst obtained by alloying modification in the embodiment is analyzed, and it can be seen from the SEM graph of FIG. 1 that the catalyst presents a three-dimensional morphology with a rich porous structure, and it can also be seen that part of the iron-platinum alloy is distributed on the surface of the catalyst. It can be seen from the TEM graph of FIG. 2 that the catalyst forms a three-dimensional porous structure and a large amount of relatively dispersed iron-platinum alloy. It can be seen from the high-resolution transmission electron microscope (HR-TEM) graph of FIG. 3 that the irregular lattice fringes indicate that the carbon matrix has amorphous properties, and the selected area electron diffraction graph in the inset also proves the existence of iron-platinum alloy in the entire carbon matrix. It is further proved that the iron-platinum alloy exists from the X-ray diffraction graph of FIG. 4. It can be clearly seen from the X-ray photoelectron spectroscopy test graph of FIG. 5 that the content of M-Nx active sites in the catalyst is as high as 29.2%, which proves the existence of high-content active sites, which effectively improves the catalytic activity of the catalyst. As shown in FIG. 6, the catalyst presents a typical type IV nitrogen adsorption-desorption isotherm, and the pore size distribution shows that the catalyst has a hierarchical pore structure, and the specific surface area is as high as 1139.2m 2 / g, which is beneficial to expose more active sites, accelerate electron transfer and mass transfer rate. The excellent electrochemical performance of the catalyst is shown by the LSV curve of Fig. 7, and it is obvious that the catalyst obtained by the alloying modification method in this embodiment (E 1 / 2 = 0.856 V vs. RHE, J L = 5.86 mA cm -2 ) has comparable ORR activity with 20% Pt / C (E 1 / 2 = 0.8561 V vs. RHE, J L = 5.3 mA cm -2 ), and the catalyst obtained by the alloying modification method in this embodiment has less Pt content, not higher than 5%, and lower cost.

[0054] Example 3:

[0055] An alloying modification method of a platinum catalyst, comprising:

[0056] Step S1, uniformly mix 5% platinum carbon catalyst (Shanghai Aladdin Biochemical Technology Co., Ltd., a commercially available product), a phytic acid solution with a mass concentration of 70% (Shanghai Maikelin Biochemical Technology Co., Ltd., a commercially available product) and deionized water, and stir for 24 h, wherein the amount of platinum carbon catalyst is 0.3 g, the amount of phytic acid solution is 1.5 mL, and the amount of deionized water is 12 mL; then freeze-dry the mixed solution, and the freeze-drying step specifically comprises: pre-freezing the mixed solution at a temperature of -15℃ for 2 h, then placing it in a vacuum freeze dryer at a temperature of -55℃, and freeze-drying for 12 h.

[0057] Step S2, pyrolyze the powder freeze-dried in step S1 once, specifically by heating at a rate of 5℃ / min to 1000℃, and then holding for 1 h to complete the first pyrolysis;

[0058] and then treating the product after the first pyrolysis with sulfuric acid, specifically by placing the product after the first pyrolysis in a 2 mol / L sulfuric acid solution and stirring at a temperature of 80℃ for 10 h;

[0059] Then wash and suction-filter using ultrapure water, and then dry, and the drying step specifically comprises: placing the sample obtained after suction-filtering in a 65℃ air drying oven for drying for 6 h.

[0060] Step S3, the dried powder in step S2 is uniformly mixed with ferrous sulfate (AR, commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,10-phenanthroline (99%, commercially available product of Shanghai Titan Science and Technology Co., Ltd.), wherein the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline is 50 mg:0.014 mg:0.028 mg; then secondary pyrolysis is carried out, specifically: heating to 1000℃ at a rate of 4.5℃ / min, then holding for 1h, to complete the secondary pyrolysis.

[0061] Step S4, the product of the secondary pyrolysis in step S3 is treated with sulfuric acid, specifically: the pyrolyzed product is placed in a 2 mol / L sulfuric acid solution and stirred at 80℃ for 10h;

[0062] Then the sample after suction filtration is washed with ultrapure water and dried, and the drying step is specifically: the sample after suction filtration is placed in a 65℃ air drying oven for drying for 6h, to obtain an alloyed modified carbon-based catalyst (i.e. Pt-Fe-NPC catalyst).

[0063] The specific surface area of the carbon-based catalyst obtained by alloying in this embodiment is: 1349.2 m² / g, and the ORR activity is: E 1 / 2 =0.842 V vs. RHE.

[0064] Comparative Example 1:

[0065] A method for preparing a carbon-based catalyst, comprising:

[0066] Step S1, 5% platinum carbon catalyst (commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.) is uniformly mixed with etchant (using existing conventional etchant, including but not limited to zinc chloride solution, ammonium chloride solution, sodium bicarbonate solution, ammonium bicarbonate solution) and deionized water, and stirred for 18h, wherein the amount of platinum carbon catalyst is 0.2g, and the amount of etchant is the same as the amount of phytic acid in Example 2, and the etchant is dissolved in 10mL of deionized water; then the mixed solution is freeze-dried, and the freeze-drying step is specifically: the mixed solution is pre-frozen at a temperature of-12℃ for 2h, then placed in a vacuum freeze dryer at a temperature of-50℃, and freeze-dried for 12h.

[0067] Step S2, consistent with step S2 in Example 2;

[0068] Step S3, consistent with step S3 in Example 2;

[0069] Step S4, consistent with step S4 in Example 2.

[0070] The specific surface area of the carbon-based catalyst prepared in the present comparative example (using zinc chloride solution, ammonium chloride solution, sodium bicarbonate solution, and ammonium bicarbonate solution as etching agents, respectively) is 462.5 m² / g, 628.3 m² / g, 366.8 m² / g, and 481.7 m² / g, respectively, and the ORR activity is E 1 / 2 = 0.75 V vs. RHE, E 1 / 2 = 0.77 V vs. RHE, E 1 / 2 = 0.81 V vs. RHE, E 1 / 2 = 0.79 V vs. RHE, and the active site content is 15.7%, 17.2%, 11.9%, and 19.4%, respectively.

[0071] Comparative Example 2

[0072] A method for preparing a carbon-based catalyst, comprising:

[0073] Step S1, uniformly mix 5% platinum carbon catalyst (a commercially available product from Shanghai Aladdin Biochemical Technology Co., Ltd.), a phytic acid solution with a mass concentration of 70% (a commercially available product from Shanghai Maikelin Biochemical Technology Co., Ltd.), and deionized water, and stir for 18 h, wherein the amount of platinum carbon catalyst is 0.2 g, the amount of phytic acid solution is 1 mL, and the amount of deionized water is 10 mL; then dry the mixed solution, and the drying is performed by conventional drying (i.e., placing it in a 60°C air drying oven until a powder is obtained).

[0074] Step S2, consistent with step S2 in Example 2;

[0075] Step S3, consistent with step S3 in Example 2;

[0076] Step S4, consistent with step S4 in Example 2.

[0077] The specific surface area of the carbon-based catalyst prepared in the present comparative example is 990.6 m² / g, and the ORR activity is E 1 / 2 = 0.83 V vs. RHE, and the active site content is 23.2%.

[0078] Comparative Example 3

[0079] A method for preparing a carbon-based catalyst, comprising:

[0080] Step S1, consistent with step S1 in Example 2;

[0081] Step S2, the freeze-dried powder in step S1 is uniformly mixed with ferrous sulfate (AR, Shanghai Aladdin Biochemical Technology Co., Ltd., commercially available product), 1,10-phenanthroline (99%, Shanghai Titan Science and Technology Co., Ltd., commercially available product), wherein the mass ratio of the freeze-dried powder, ferrous sulfate and 1,10-phenanthroline is 40 mg:0.013 mg:0.027 mg; then pyrolysis is performed, specifically: heating at a rate of 4℃ / min to 900℃, and then holding for 1.5h to complete the pyrolysis.

[0082] Step S3, consistent with step S4 in Example 2.

[0083] The specific surface area of the carbon-based catalyst prepared in the present comparative example is 1036.7 m² / g, the ORR activity is E 1 / 2 =0.79 V vs. RHE, and the active site content is 14.6%.

[0084] Example 4:

[0085] The application of a method for alloying modification of a platinum catalyst, specifically in the preparation of a primary zinc-air battery, comprises:

[0086] 2 mg of the carbon-based catalyst prepared by the alloying modification method in Example 2 is weighed and uniformly dispersed in a mixed solution composed of 195 μL of ethanol and 5 μL of naphthol; then the mixed solution is uniformly coated on a 4 cm 2 square carbon cloth as a positive electrode oxygen reduction catalyst, a zinc sheet with a thickness of 0.2 mm is selected as the negative electrode, and a 6 mol / L KOH solution is used as the electrolyte to assemble a primary zinc-air battery.

[0087] Control group: replace the carbon-based catalyst prepared by the alloying modification method in Example 2 with a Pt / C catalyst with a platinum content of 20% (i.e. the existing commercially available Pt / C catalyst), and use the same method as above to assemble and prepare a primary zinc-air battery.

[0088] Figure 8 is a comparison chart of the energy density of the primary zinc-air battery assembled with the carbon-based catalyst prepared by the alloying modification method in Example 2 and the Pt / C catalyst with a platinum content of 20%; as can be clearly seen from Figure 8, when discharging at a fixed current density of 50 mA / cm 2 , the primary zinc-air battery assembled with the iron-platinum alloy doped carbon-based catalyst has a high energy density of 926 Wh / kg-1 Zn, far exceeding the energy density of the primary zinc-air battery assembled with the Pt / C catalyst with a platinum content of 20%, i.e. 770 Wh / kg-1 Zn.

[0089] Figure 9 is a comparison chart of the energy density of the primary zinc-air battery prepared in the present example at a fixed current density of 50 mA / cm 2The long-time constant current density discharge graph of the zinc-air battery is shown in Figure 9. It can be obviously seen that the discharge voltage of the primary zinc-air battery assembled by the carbon-based catalyst prepared by the alloying modification method of the application only presents a reduction of 44 mV under the condition of constant current density discharge for about 140 h.

[0090] Example 5:

[0091] The application of the alloying modification method of the platinum catalyst, in particular, the application in the preparation of the rechargeable zinc-air battery, comprises:

[0092] 2 mg of the carbon-based catalyst prepared by the alloying modification method in Example 2 and 2 mg of RuO2 are weighed and uniformly dispersed in a mixed solution composed of 390 μL of ethanol and 10 μL of naphthol; then the mixed solution is uniformly coated on a 4 cm 2 long carbon cloth as a positive electrode oxygen reduction catalyst, a zinc sheet with a thickness of 0.2 mm is selected as a negative electrode, a mixed solution of KOH and Zn(Ac)2 is used as an electrolyte, and a rechargeable zinc-air battery is assembled; wherein the concentration of KOH is 6 mol / L, and the concentration of Zn(Ac)2 is 0.2 mol / L.

[0093] The control group: the Pt / C catalyst with a platinum content of 20% (i.e. the existing commercially available Pt / C catalyst) is used instead of the carbon-based catalyst prepared by the alloying modification method in Example 2, and the rechargeable zinc-air battery is assembled by using the same method as described above.

[0094] As shown in Figure 10, the rechargeable zinc-air battery assembled by the carbon-based catalyst prepared by the alloying modification method and RuO2 in this embodiment has a discharge voltage of 1.1926 V and a charge voltage of 1.9786 V in the charging and discharging process for more than 100 h, and the difference between the charging and discharging voltages is 78 mV; while the rechargeable zinc-air battery assembled by the 20% Pt / C catalyst and RuO2 has a larger difference between the charging and discharging voltages, i.e. 90 mV, which indicates that the carbon-based catalyst prepared by the alloying modification method has better long-term cycle stability when applied in the rechargeable zinc-air battery.

Claims

1. A method for alloying and modifying a platinum catalyst, characterized in that: include: Step S1: Mix 5% platinum-carbon catalyst, phytic acid solution and deionized water evenly and stir, then freeze-dry the mixture. Step S2: The freeze-dried powder from step S1 is subjected to a first pyrolysis, and the product after the first pyrolysis is treated with sulfuric acid, then washed with ultrapure water, filtered, and dried. Step S3: Mix the dried powder from step S2 with ferrous sulfate and 1,10-phenanthroline evenly, and then perform a second pyrolysis. Step S4: The product from the secondary pyrolysis in step S3 is treated with sulfuric acid, then washed and filtered with ultrapure water, and then dried to obtain the alloyed modified carbon-based catalyst.

2. The method according to claim 1, characterized in that: In step S1, the phytic acid solution is a phytic acid solution with a mass concentration of 70%; the mass-volume ratio of 5% platinum carbon catalyst, phytic acid solution and deionized water is 0.1-0.3g: 0.5-1.5mL: 8mL-12mL.

3. The method according to claim 1, characterized in that: In step S1, the stirring time of 5% platinum-carbon catalyst and phytic acid solution is 12-24 hours.

4. The method according to claim 1, characterized in that: The specific steps of the first pyrolysis in step S2 are as follows: the temperature is increased to 800-1000℃ at a rate of 3-5℃ / min, and then kept at that temperature for 1-2 hours to complete the first pyrolysis.

5. The method according to claim 1, characterized in that: In step S3, the mass ratio of the dried powder, ferrous sulfate, and 1,10-phenanthroline is 30–50 mg: 0.012–0.014 mg: 0.026~0.028mg.

6. The method according to claim 1, characterized in that: The specific steps of the secondary pyrolysis in step S3 are as follows: the temperature is increased to 800-1000℃ at a rate of 3.5-4.5℃ / min, and then kept at that temperature for 1-2 hours to complete the secondary pyrolysis.

7. The method according to claim 1, characterized in that: The sulfuric acid treatment in steps S2 and S4 specifically involves placing the pyrolysis product into a 0.5–2 mol / L sulfuric acid solution and stirring at 60–80°C for 10–12 hours.

8. The method according to claim 1, characterized in that: The drying step in steps S2 and S4 specifically involves placing the filtered sample into a forced-air drying oven at 55℃~65℃ and drying it for 6 hours.

Images