Method for alloying modification of platinum catalysts and use thereof

Abstract

The application provides an alloying modification method of a platinum catalyst, relates to the field of electrochemical catalysis, and particularly relates to the following steps: mixing 5% of a platinum carbon catalyst and a phytic acid solution uniformly, performing freeze-drying treatment, performing one-time pyrolysis, sulfuric acid treatment, and ultra-pure water cleaning and suction filtration, and drying to obtain a powder; adding ferrous sulfate and 1,10-phenanthroline, performing second-time pyrolysis, sulfuric acid treatment, and ultra-pure water cleaning and suction filtration, and drying to obtain an alloying modification carbon-based catalyst. The method is alloyed by the metal platinum and a transition metal, effectively improves the activity and stability of the catalyst, reduces the use amount of the noble metal platinum, and effectively reduces the manufacturing cost of the catalyst; and the alloying modification carbon-based catalyst obtained by the method can be used for the preparation of a primary zinc-air battery, a rechargeable zinc-air battery and the like.

Description

TECHNICAL FIELD

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

[0002] Hydrogen fuel cells have become one of the focuses in the field of energy conversion due to high energy density, environmental friendliness and abundant raw material resources; the performance of hydrogen fuel cells mainly depends on air electrodes, which undergo a slow oxygen reduction reaction (ORR) during discharging, consuming electrons from fuel to directly convert chemical energy into electrical energy. Therefore, some cars have been equipped with fuel cells as power sources and have achieved mass production. In the prior art, there are many types of fuel cell cathode catalysts, and high catalytic activity, high stability and low cost have become the main direction of synthesizing catalysts; in the 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 metal and heteroatom-doped carbon material. Using noble metal as catalyst can significantly improve the electrocatalytic performance of ORR, but noble metal is not only expensive, but also has poor resistance to poisoning and poor stability, which seriously limits the large-scale application of noble metal-based catalysts in the field of fuel cells; using non-noble metal as catalyst can effectively reduce the cost of catalyst, but it has low catalytic activity, poor stability (for example: Fe-N-C catalyst may have problems such as deactivation of Fe active sites, corrosion of C and collapse of three-phase interface of the catalyst during operation of hydrogen fuel cells), difficulty in mass production, high requirement 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, which leads to the fact that non-noble metal cannot be used in high-power, large-scale and long-term stable operation environment, and seriously restricts the application of non-noble metal catalyst in the field of fuel cells. SUMMARY

[0003] In view of the problems existing in the prior art, the purpose of the present application is to provide a method for alloying modification of platinum catalyst, which can effectively improve the activity and stability of the catalyst by alloying metal platinum with transition metal, and reduce the use amount of noble metal platinum and the manufacturing cost of the catalyst.

[0004] Another purpose of the present application is to provide the application of the alloyed and modified platinum catalyst.

[0005] The purpose of the present application is achieved by the following technical solutions.

[0006] A method for alloying modification of platinum catalyst, comprising:

[0007] Step S1, uniformly mix 5% platinum carbon catalyst, phytic acid solution and deionized water, stir, then freeze dry the mixed solution;

[0008] Step S2, once pyrolysis is performed on the freeze-dried powder in step S1, and the product after the first pyrolysis is treated with sulfuric acid, then after washing and filtering with ultrapure water, drying is performed;

[0009] Step S3, uniformly mix the dried powder in step S2 with ferrous sulfate and 1,10-phenanthroline, then perform secondary pyrolysis;

[0010] Step S4, the product of the secondary pyrolysis in step S3 is treated with sulfuric acid, then after washing and filtering with ultrapure water, drying is performed, thereby obtaining an alloyed modified carbon-based catalyst (i.e. Pt-Fe-NPC catalyst).

[0011] Based on the further optimization of the above scheme, 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.

[0012] Based on the further optimization of the above scheme, the stirring time of 5% platinum carbon catalyst and phytic acid solution in step S1 is 12-24h.

[0013] Based on the further optimization of the above scheme, the freeze-drying step in step S1 is specifically: after mixing the solution, pre-freeze at a temperature of -15℃ to -10℃ for 2h, then put it into a vacuum freeze dryer at a temperature of -55℃ to -45℃, freeze dry for 12h.

[0014] Based on the further optimization of the above scheme, the specific steps of the first pyrolysis in step S2 are: heat at a rate of 3-5℃ / min to 800-1000℃, then keep the temperature for 1-2h to complete the first pyrolysis.

[0015] Based on the further optimization of the above scheme, 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.

[0016] Based on the further optimization of the above scheme, the specific steps of the secondary pyrolysis in step S3 are: heat at a rate of 3.5-4.5℃ / min to 800-1000℃, then keep the temperature for 1-2h to complete the secondary pyrolysis.

[0017] Further to the above scheme, the sulfuric acid treatment in steps S2 and S4 is specifically as follows: the pyrolysis product is placed in a 0.5-2 mol / L sulfuric acid solution and stirred at 60-80℃ for 10-12 h.

[0018] Further to the above scheme, the drying step in steps S2 and S4 is specifically as follows: the sample obtained after suction filtration is placed in a 55-65℃ forced air drying oven and dried for 6 h.

[0019] Based on the above preparation method, the application also provides an application of the alloy-modified platinum catalyst, specifically, an application of the Pt-Fe-NPC catalyst in a zinc-air battery, and the Pt-Fe-NPC catalyst can be applied in the preparation process of a primary zinc-air battery or a rechargeable zinc-air battery.

[0020] The following are the technical effects possessed by the application:

[0021] The present application uniformly mixes 5% platinum carbon catalyst and phytic acid solution, and then performs freeze-drying, followed by a second pyrolysis after uniformly mixing ferrous sulfate and 1,10-phenanthroline, which not only effectively improves the morphology of the platinum carbon catalyst, forms a three-dimensional network porous structure precursor (i.e., forms 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 pyrolysis, and avoids problems such as site deactivation, poor stability, and poor ORR activity caused by uneven active sites. In addition, it also promotes the sufficient combination of Fe ions and Pt atoms to form iron-platinum alloy, so as to anchor platinum nanoparticles as anchor points, avoid their dissolution and migration during the ORR reaction, effectively ensure the stability of the catalyst, improve the catalytic activity of the catalyst, and improve the corresponding battery performance.

[0022] The specific surface area of the carbon-based catalyst prepared by alloy modification is as high as 1139.2 m² / g or more, and at the same time, it exhibits excellent ORR activity: E 1 / 2 =0.851 V vs.RHE; and the zinc-air battery assembled with the catalyst as the positive electrode oxygen reduction catalyst has a high energy density of not less than 926 Wh / kg-1 Zn. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The SEM image of the alloy-modified catalyst prepared in Example 2 of the present application.

[0024] Figure 2 The TEM image of the alloy-modified catalyst prepared in Example 2 of the present application.

[0025] Figure 3 HR-TEM image of the alloying modified catalyst prepared in Example 2 of the present application.

[0026] Figure 4 XRD image of the alloying modified catalyst prepared in Example 2 of the present application.

[0027] Figure 5 XPS image of the alloying modified catalyst prepared in Example 2 of the present application.

[0028] Figure 6 N2 adsorption-desorption isotherm image of the alloying modified catalyst prepared in Example 2 of the present application (wherein the inset is the pore distribution).

[0029] Figure 7 LSV comparison image of the alloying modified catalyst prepared in Example 2 of the present application and Pt / C catalyst for oxygen reduction.

[0030] Figure 8 Energy density comparison image of the primary zinc-air battery assembled by the alloying modified catalyst prepared in Example 2 of the present application and Pt / C catalyst.

[0031] Figure 9 Long time constant current density discharge image of the primary zinc-air battery assembled by the alloying modified catalyst prepared in Example 2 of the present application.

[0032] Figure 10 Charge / discharge cycle test comparison image of the rechargeable zinc-air battery assembled by the alloying modified catalyst prepared in Example 2 of the present application and Pt / C catalyst. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application.

[0034] Example 1:

[0035] An alloying modification method of a platinum catalyst, comprising:

[0036] Step S1, 5% platinum carbon catalyst (Shanghai Aladdin Bio-Chem Technology Co., Ltd., commercially available product), a phytic acid solution with a mass concentration of 70% (Shanghai Maikelin Biochemical Technology Co., Ltd., commercially available product) and deionized water were uniformly mixed and stirred for 12 h, wherein the amount of platinum carbon catalyst was 0.15 g, the amount of phytic acid solution was 0.5 mL, and the amount of deionized water was 8 mL; then the mixed solution was freeze-dried, and the freeze-drying step was as follows: the mixed solution was pre-frozen at a temperature of -10°C for 2 h, then was placed in a vacuum freeze dryer, and was freeze-dried at a temperature of -45°C for 12 h.

[0037] Step S2, the freeze-dried powder in step S1 was subjected to a first pyrolysis, specifically: heating at a rate of 3°C / min to 800°C, and then holding for 2 h to complete the first pyrolysis;

[0038] The product after the first pyrolysis was treated with sulfuric acid, specifically: the product after the first pyrolysis was placed in a 0.5 mol / L sulfuric acid solution and stirred at a temperature of 60°C for 12 h;

[0039] Then, after washing and suction filtration with ultrapure water, drying was performed, and the drying step was as follows: the sample obtained after suction filtration was placed in a 55°C air drying oven and dried for 6 h.

[0040] Step S3, the dried powder in step S2 was uniformly mixed with ferrous sulfate (Shanghai Aladdin Bio-Chem Technology Co., Ltd., AR, commercially available product) and 1,10-phenanthroline (Shanghai Titan Science and Technology Co., Ltd., 99%, commercially available product), wherein the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline was 30 mg:0.012 mg:0.026 mg; then a second pyrolysis was performed, specifically: heating at a rate of 3.5°C / min to 800°C, and then holding for 2 h to complete the second pyrolysis.

[0041] Step S4, the product after the second pyrolysis in step S3 was treated with sulfuric acid, specifically: the product after pyrolysis was placed in a 0.5 mol / L sulfuric acid solution and stirred at a temperature of 60°C for 12 h;

[0042] Then, after washing and suction filtration with ultrapure water, drying was performed, and the drying step was as follows: the sample obtained after suction filtration was placed in a 55°C air drying oven and dried for 6 h, thereby obtaining an alloyed modified carbon-based catalyst (i.e., a Pt-Fe-NPC catalyst).

[0043] The specific surface area of the carbon-based catalyst obtained by alloying in this example was 1227.8 m² / g, and the ORR activity was E 1 / 2 =0.834 V vs. RHE.

[0044] Example 2:

[0045] A method for alloying modification of a platinum catalyst, comprising:

[0046] Step S1, uniformly mix 5% platinum carbon catalyst (a product commercially available from Shanghai Aladdin Bio-Chem Technology Co., Ltd.), a 70% phytic acid solution (a product commercially available from Shanghai Maikelin Biochemical Technology Co., Ltd.) and deionized water, and stir for 18 hours, 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 freeze-dry the mixed solution, and the freeze-drying step specifically comprises: pre-freezing the mixed solution at a temperature of -12°C for 2 hours, then placing it in a vacuum freeze dryer and freeze-drying at a temperature of -50°C for 12 hours.

[0047] Step S2, pyrolyze the freeze-dried powder in step S1 once, specifically: heat at a rate of 4°C / min to 900°C, then keep the temperature for 1.5 hours to complete the first pyrolysis;

[0048] and then treat the product of the first pyrolysis with sulfuric acid, specifically: place the product of the first pyrolysis in a 1 mol / L sulfuric acid solution and stir at a temperature of 70°C for 11 hours;

[0049] then wash with ultrapure water, and then dry, and the drying step specifically comprises: placing the sample obtained after filtration in a 60°C air drying oven for 6 hours.

[0050] Step S3, uniformly mix the dried powder in step S2 with ferrous sulfate (a product commercially available from Shanghai Aladdin Bio-Chem Technology Co., Ltd.) and 1,10-phenanthroline (a product commercially available from Shanghai Titan Science and Technology Co., Ltd.), wherein the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline is 40 mg:0.013 mg:0.027 mg; then pyrolyze again, specifically: heat at a rate of 4°C / min to 900°C, then keep the temperature for 1.5 hours to complete the second pyrolysis.

[0051] Step S4, treat the product of the second pyrolysis in step S3 with sulfuric acid, specifically: place the pyrolyzed product in a 1 mol / L sulfuric acid solution and stir at a temperature of 70°C for 11 hours;

[0052] then wash with ultrapure water, and then dry, and the drying step specifically comprises: placing the sample obtained after filtration in a 60°C air drying oven for 6 hours, to obtain an alloyed modified carbon-based catalyst (i.e., a Pt-Fe-NPC catalyst).

[0053] The carbon-based catalyst obtained by alloying in this example has a specific surface area of 1139.2 m² / g, and an ORR activity of E 1 / 2 =0.851 V vs. RHE.

[0054] The carbon-based catalysts obtained through alloying modification in the examples were analyzed. Figure 1 The SEM images show that the catalyst exhibits a three-dimensional morphology with a rich porous structure, and some iron-platinum alloy can also be seen distributed on the catalyst surface. Figure 2 The TEM images show that the catalyst forms a three-dimensional porous structure and contains a large amount of relatively dispersed iron-platinum alloy. Figure 3 The high-resolution transmission electron microscope (HR-TEM) images reveal irregular lattice fringes, indicating the amorphous nature of the carbon matrix. The inset selected-area electron diffraction pattern further confirms the presence of an iron-platinum alloy throughout the carbon matrix. Figure 4 The X-ray diffraction pattern further confirms the existence of the iron-platinum alloy. Figure 5 The X-ray photoelectron spectroscopy (XPS) results clearly show that the content of M-Nx active sites in the catalyst is as high as 29.2%, proving the presence of a high content of active sites, which effectively improves the catalytic activity of the catalyst. Figure 6 It can be seen that the catalyst exhibits a typical Type IV nitrogen adsorption-desorption isotherm, and the pore size distribution indicates that the catalyst has a hierarchical porous structure with a specific surface area as high as 1139.2 m². 2 / g, which is beneficial for exposing more active sites and accelerating electron transfer and mass transfer rates. Figure 7 The LSV curves demonstrate the excellent electrochemical performance of the catalyst, clearly showing that the catalyst obtained through alloying modification in this embodiment (E 1 / 2 = 0.856 V vs. RHE, J L = 5.86mA cm -2 ) and 20% Pt / C (E 1 / 2 = 0.8561V vs. RHE, J L = 5.3mA cm -2 It has considerable ORR activity, and the catalyst obtained by alloying modification in this embodiment has less Pt content, not more than 5%, and lower cost.

[0055] Example 3:

[0056] An alloying modification method for a platinum catalyst, comprising:

[0057] Step S1, 5% platinum carbon catalyst (Shanghai Aladdin Biochem Technology Co., Ltd., commercially available product), a 70% phytic acid solution (Shanghai Maikelin Biochemical Technology Co., Ltd., commercially available product) and deionized water were uniformly mixed and stirred for 24 h, wherein the amount of platinum carbon catalyst was 0.3 g, the amount of phytic acid solution was 1.5 mL, and the amount of deionized water was 12 mL; then the mixed solution was freeze-dried, and the freeze-drying step was as follows: the mixed solution was pre-frozen at -15℃ for 2 h, then was placed in a vacuum freeze dryer at a temperature of -55℃ and freeze-dried for 12 h.

[0058] Step S2, the freeze-dried powder in step S1 was pyrolyzed once, specifically: the temperature was raised to 1000℃ at a rate of 5℃ / min, and then was kept for 1 h to complete the first pyrolysis;

[0059] The product after the first pyrolysis was treated with sulfuric acid, specifically: the product after the first pyrolysis was placed in a 2 mol / L sulfuric acid solution and stirred at 80℃ for 10 h;

[0060] Then the sample after filtration was washed with ultrapure water and dried, and the drying step was as follows: the sample after filtration was placed in a 65℃ air drying oven and dried for 6 h.

[0061] Step S3, the dried powder in step S2 was uniformly mixed with ferrous sulfate (Shanghai Aladdin Biochem Technology Co., Ltd., AR, commercially available product) and 1,10-phenanthroline (Shanghai Titan Science and Technology Co., Ltd., 99%, commercially available product), wherein the mass ratio of the dried powder, ferrous sulfate and 1,10-phenanthroline was 50 mg:0.014 mg:0.028 mg; then the second pyrolysis was carried out, specifically: the temperature was raised to 1000℃ at a rate of 4.5℃ / min, and then was kept for 1 h to complete the second pyrolysis.

[0062] Step S4, the product after the second pyrolysis in step S3 was treated with sulfuric acid, specifically: the product after pyrolysis was placed in a 2 mol / L sulfuric acid solution and stirred at 80℃ for 10 h;

[0063] Then the sample after filtration was washed with ultrapure water and dried, and the drying step was as follows: the sample after filtration was placed in a 65℃ air drying oven and dried for 6 h to obtain an alloyed modified carbon-based catalyst (i.e. Pt-Fe-NPC catalyst).

[0064] The specific surface area of the carbon-based catalyst obtained by alloying in this example was 1349.2 m² / g, and the ORR activity was E 1 / 2 =0.842 V vs. RHE.

[0065] Comparative Example 1:

[0066] A method for preparing a carbon-based catalyst, comprising:

[0067] Step S1, uniformly mix 5% platinum carbon catalyst (a commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.), etchant (use existing conventional etchants, including but not limited to zinc chloride solution, ammonium chloride solution, sodium bicarbonate solution, ammonium bicarbonate solution) and deionized water, and stir for 18 hours, wherein the amount of platinum carbon catalyst is 0.2 g, and the amount of etchant is equal to the amount of phytic acid in Example 2, and the etchant is dissolved in 10 mL of deionized water; then the mixed solution is freeze-dried, and the freeze-drying step specifically comprises: pre-freezing the mixed solution at a temperature of -12°C for 2 hours, then placing it in a vacuum freeze dryer at a temperature of -50°C and freeze-drying for 12 hours.

[0068] Step S2, consistent with Step S2 in Example 2;

[0069] Step S3, consistent with Step S3 in Example 2;

[0070] Step S4, consistent with Step S4 in Example 2.

[0071] The specific surface areas of the carbon-based catalysts prepared in the present comparative examples (using zinc chloride solution, ammonium chloride solution, sodium bicarbonate solution, and ammonium bicarbonate solution as etchants, respectively) are 462.5 m² / g, 628.3 m² / g, 366.8 m² / g, and 481.7 m² / g, respectively, and the ORR activities are 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 contents are 15.7%, 17.2%, 11.9%, and 19.4%, respectively.

[0072] Comparative Example 2:

[0073] A method for preparing a carbon-based catalyst, comprising:

[0074] Step S1, uniformly mix 5% platinum carbon catalyst (a commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.), 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 18 hours, 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).

[0075] Step S2, consistent with step S2 in example 2;

[0076] Step S3, consistent with step S3 in example 2;

[0077] Step S4, consistent with step S4 in example 2.

[0078] The specific surface area of the carbon-based catalyst prepared in the present comparative example is 990.6 m2 / g, the ORR activity is E 1 / 2 =0.83 V vs. RHE, and the active site content is 23.2%.

[0079] Comparative example 3:

[0080] A method for preparing a carbon-based catalyst, comprising:

[0081] Step S1, consistent with step S1 in example 2;

[0082] Step S2, the freeze-dried powder in step S1 is uniformly mixed with ferrous sulfate (AR, commercially available from Shanghai Aladdin Biochemical Technology Co., Ltd.), 1,10-phenanthroline (99%, commercially available from Shanghai Titan Science and Technology Co., Ltd.), 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 1.5 h to complete the pyrolysis.

[0083] Step S3, consistent with step S4 in example 2.

[0084] 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%.

[0085] Example 4:

[0086] Application of a method for alloying modification of a platinum catalyst, specifically in the preparation of a primary zinc-air battery, comprising:

[0087] 2 mg of the carbon-based catalyst prepared by the method for alloying modification 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 a negative electrode, and a 6 mol / L KOH solution is used as an electrolyte to assemble a primary zinc-air battery.

[0088] The 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 described above to assemble a primary zinc-air battery.

[0089] Figure 8 The energy density comparison chart of the primary zinc-air battery assembled by the carbon-based catalyst prepared by the alloying modification method in Example 2 and the Pt / C catalyst with a platinum content of 20%. Figure 8 It can be clearly seen that the primary zinc-air battery assembled by the carbon-based catalyst doped with the iron-platinum alloy has a high energy density of 926 Wh / kg-1 Zn when discharged at a fixed current density of 50 mA / cm 2 , which is much higher than the energy density of the primary zinc-air battery assembled by the Pt / C catalyst with a platinum content of 20%, i.e., 770 Wh / kg-1 Zn.

[0090] Figure 9 The long-time constant current density discharge chart of the primary zinc-air battery prepared in this example at a fixed current density of 50 mA / cm 2 . It can be clearly 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 shows a decrease of 44 mV after experiencing a constant current density discharge of about 140 h.

[0091] Example 5:

[0092] The application of the alloying modification method of a platinum catalyst, specifically in the preparation of a rechargeable zinc-air battery, comprises:

[0093] Take 2 mg of the carbon-based catalyst prepared by the alloying modification method in Example 2 and 2 mg of RuO2, and uniformly disperse them in a mixed solution composed of 390 μL of ethanol and 10 μL of naphthol; then uniformly coat the mixed solution on a 4 cm 2 square carbon cloth as a positive electrode oxygen reduction catalyst, select a zinc sheet with a thickness of 0.2 mm as a negative electrode, and use a mixed solution of KOH and Zn(Ac)2 as an electrolyte to assemble a rechargeable zinc-air battery; wherein the concentration of KOH is 6 mol / L, and the concentration of Zn(Ac)2 is 0.2 mol / L.

[0094] The 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 described above to assemble a primary zinc-air battery.

[0095] As Figure 10As shown, the chargeable and dischargeable zinc-air battery assembled by the carbon-based catalyst prepared by the alloying modification method and RuO2 in the embodiment has a discharge voltage maintained at 1.1926 V and a charge voltage maintained at 1.9786 V in a charge and discharge process lasting more than 100 h, and a charge and discharge voltage difference of 78 mV; while the chargeable and dischargeable zinc-air battery assembled by 20% Pt / C catalyst and RuO2 has a larger charge and discharge voltage difference, that is, 90 mV, indicating that the carbon-based catalyst prepared by the alloying modification method has better long-term cycle stability when applied in the chargeable and dischargeable 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 heated to 800-1000℃ at a rate of 3-5℃ / min and held for 1-2 hours to complete one pyrolysis. 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, then heat to 800-1000℃ at a rate of 3.5-4.5℃ / min and keep at that temperature for 1-2 hours to complete the secondary 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 alloying modification method for a platinum catalyst 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 alloying modification method for a platinum catalyst 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 alloying modification method for a platinum catalyst 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.

5. The alloying modification method for a platinum catalyst 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.

6. The alloying modification method for a platinum catalyst 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.

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