A method for ultrafast preparation of a single-atom bifunctional oxygen catalyst

Abstract

The application discloses a kind of single-atom bifunctional oxygen catalyst ultrafast preparation method, belong to electrocatalytic energy storage technical field.The present air battery cathode catalyst preparation is long in time, cost is high, preparation environment is strictly required, the present application provides a kind of quick preparation process simple, solvent-free green environmental protection, in short time, preparation obtains single-atom bifunctional oxygen catalyst with high performance.The method utilizes carbon nanotube as carbon source, metal phthalocyanine is iron source, and a kind of high-performance single-atom bifunctional oxygen catalyst is prepared by doping phosphorus through Joule heat flash evaporation technology.The catalyst has excellent ORR and OER catalytic performance, and has potential application value in the cathode catalyst of metal-air fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic energy storage technology, specifically relating to a method for ultrafast preparation of high-performance single-atom bifunctional oxygen catalysts using Joule thermal flash evaporation technology. Background Technology

[0002] Many researchers are working to develop environmentally friendly, efficient, and low-cost energy storage devices, such as fuel cells and metal-air batteries. Among these applications, rechargeable zinc-air batteries stand out due to their high theoretical energy density (1370 Wh / kg). -1 Low cost, safety, and environmental friendliness have garnered widespread attention. The two main processes—the oxygen reduction reaction (ORR) at the air cathode and the oxygen evolution reaction (OER) at the anode—dominate battery performance during charging and discharging. However, because the reactions at the cathode are six orders of magnitude slower than those at the anode, cathode catalysts represent the biggest challenge hindering their commercialization.

[0003] Currently, non-precious metal materials used as catalysts for the oxygen reduction reaction mainly include transition metal oxides, transition metal nitrides, and carbon materials doped with transition metals and heteroatoms. Platinum-based catalysts are the most effective cathode catalysts for this slow reaction, but the high price and scarcity of platinum are major drawbacks preventing their widespread application. Transition metal oxides and nitrides, with their abundant sources and high electrocatalytic activity, possess the characteristics to replace precious platinum-based catalysts. However, their poor conductivity and tendency for metal agglomeration result in low electrocatalytic oxygen reduction activity. Using highly conductive carbon materials as supports and modifying them with transition metals and heteroatoms can achieve both the catalytic activity of transition metals / heteroatoms and create abundant active sites on the carbon material surface. The combined effect of these two factors gives transition metal / heteroatom-modified carbon materials extremely high conductivity and catalytic activity, theoretically improving the oxygen reduction activity of the catalyst. Therefore, carbon materials doped with transition metals and heteroatoms are currently the most promising non-precious metal catalysts and are expected to become the best alternative to platinum-based catalysts.

[0004] Among numerous preparation methods, a wide variety of carbon materials can be selected, including fullerenes, carbon fibers, carbon nanotubes, graphene, carbon black, and biomass carbon materials. Carbon nanotubes, in particular, have attracted considerable attention in the field of catalytic oxygen reduction due to their excellent porosity, good electronic conductivity, and high stability. Doping carbon supports with N, B, F, P, and S can significantly improve the electrochemical performance of carbon materials, including hydrophilicity, conductivity, and durability. Therefore, there is a need to find a low-cost, efficient, and stable non-precious metal catalyst to replace traditional platinum-based catalysts. Summary of the Invention

[0005] To address the problems of time-consuming, costly, and environmentally demanding preparation of cathode catalysts for air batteries, this invention provides a rapid, simple, solvent-free, and environmentally friendly method for preparing high-performance single-atom bifunctional oxygen catalysts in a short time. This method utilizes carbon nanotubes as the carbon source, metal phthalocyanine as the iron source, and phosphorus doping via Joule thermal flash evaporation to prepare a high-performance single-atom bifunctional oxygen catalyst. This catalyst exhibits excellent ORR and OER catalytic performance and has potential application value in cathode catalysts for metal-air fuel cells.

[0006] To achieve the above objectives, the present invention employs the following technical solutions:

[0007] An ultrafast method for preparing a single-atom bifunctional oxygen catalyst includes the following steps:

[0008] Step 1: Disperse metal phthalocyanine and carbon nanotubes in N,N-dimethylformamide and stir evenly. Wash with N,N-dimethylformamide, anhydrous ethanol and deionized water in sequence, and then vacuum dry to obtain powder material A.

[0009] Step 2: Powder material A and phosphate are then rapidly flash-evaporated to obtain material B;

[0010] Step 3: Finally, material B is acid-treated, washed to pH 7, and then vacuum dried to obtain a single-atom bifunctional oxygen catalyst.

[0011] Furthermore, the metal phthalocyanine includes any one of iron phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, or copper phthalocyanine; the carbon nanotube is a single-walled carbon nanotube or a multi-walled carbon nanotube; the phosphate includes orthophosphate (potassium phosphate, sodium phosphate, ammonium phosphate), phosphite (potassium phosphite, sodium phosphite, ammonium phosphite), or hypophosphite (potassium hypophosphite, sodium hypophosphite, ammonium hypophosphite).

[0012] Furthermore, in step 2, rapid flash evaporation is performed using Joule thermal flash evaporation, which includes flash discharge, staged heating, pulse discharge, and combined discharge.

[0013] Furthermore, when Joule heating flash evaporation is a flash discharge, the resistance is 0.1Ω~10.0Ω; the voltage of flash constant voltage discharge is 80V~200V; the discharge time is 100ms~2000ms; and the temperature is 800℃~4000℃.

[0014] When Joule heating flash is performed in stages, the resistance is 0.1Ω to 10.0Ω; the holding time of each stage is 1s to 60s; and the temperature is 800℃ to 3000℃.

[0015] When Joule flash evaporation is a pulse discharge, the resistance is 0.1Ω~10.0Ω; the number of discharges is 1 to 5; the discharge time is 0.5s to 2s; the power supply voltage is 10V~36V; and the power supply current is 10A~83A.

[0016] Furthermore, when Joule heating flash evaporation is a combined discharge, a method of first performing a staged temperature rise followed by flash discharge is adopted, with a resistance of 0.1Ω to 10.0Ω; the holding time of the staged temperature rise is 1s to 60s; the temperature is 800℃ to 3000℃; the voltage of the flash constant voltage discharge is 80V to 200V; the discharge time is 100ms to 2000ms; and the temperature is 800℃ to 4000℃.

[0017] Furthermore, the mass ratio of metal phthalocyanine to carbon nanotubes is 1:0.5 to 2.5; the mass ratio of powder material A to phosphate is 1:1 to 10.

[0018] Furthermore, in step 1, metal phthalocyanine and carbon nanotubes are dispersed in N,N-dimethylformamide by ultrasonic dispersion for a time of 0.2–1 h.

[0019] Furthermore, the vacuum drying temperature in steps 1 and 3 is between 60℃ and 100℃, and the vacuum drying time is between 6h and 12h.

[0020] A single-atom bifunctional oxygen catalyst prepared by the method described above.

[0021] Application of a single-atom bifunctional oxygen catalyst prepared by the above method in zinc-air batteries.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. Raw materials are widely available, environmentally friendly, and highly safe;

[0024] 2. The Joule thermal flash evaporation technology used is simple to operate and can complete the pyrolysis process of the catalyst in milliseconds, resulting in high preparation efficiency;

[0025] 3. Phosphates formed during flash pyrolysis can effectively increase the graphitization degree of carbon, enhance the conductivity of materials, and thus improve the catalytic activity of catalytic materials;

[0026] 4. The MNC single-atom bifunctional oxygen catalyst prepared by this invention has a rich microporous structure and exhibits excellent oxygen reduction activity, cycle stability and methanol tolerance under alkaline conditions. When used as a cathode material in zinc-air batteries, it has excellent oxygen reduction performance and a large power density, providing a theoretical basis and technical support for the practical application of zinc-air batteries. Attached Figure Description

[0027] Figure 1 Aberration-corrected transmission electron microscopy image of the target product C2 prepared in Example 2;

[0028] Figure 2 The nitrogen adsorption-desorption curve and pore size distribution of the target product C2 prepared in Example 2 are shown.

[0029] Figure 3 X-ray diffraction patterns of target products prepared with different metals;

[0030] Figure 4 ORR polarization curves of target products prepared with different metals in alkaline electrolyte;

[0031] Figure 5 OER polarization curves of target products prepared with different metal loading in alkaline electrolyte;

[0032] Figure 6 Half-wave potential histograms for target products prepared with different metals;

[0033] Figure 7 The constant current charge-discharge cycle diagram of the zinc-air battery assembled with the target product of Example 2. Detailed Implementation

[0034] Example 1

[0035] Step S1: Dissolve 0.2g of multi-walled carbon nanotubes and 0.2g of phthalocyanine iron in 120mL of N,N-dimethylformamide and sonicate for 0.5h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 12h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol, and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 80℃ for 8h. After cooling to room temperature, obtain powder product material A1.

[0036] Step S2: Weigh 100mg of material A1 obtained in step S1 and transfer it to a quartz tube. Cool the product obtained by Joule thermal flash evaporation constant voltage discharge to room temperature to obtain material B1. When Joule thermal flash evaporation is flash discharge, the resistance is 0.5Ω; the voltage of flash evaporation constant voltage discharge is 150V; the discharge time is 1000ms and the temperature is 2800℃.

[0037] Step S3: The material B1 obtained in step S2 is heated in an oil bath at 80°C for 12 hours with 1M H2SO4, then washed with deionized water until pH=7. The resulting product is transferred to a forced-air drying oven and dried at 80°C for 8 hours, then cooled to room temperature to obtain catalyst sample C1. Figure 1The image shown is a spherical aberration transmission electron microscope (TEM) image of the target product C2 prepared in Example 1. The aberration-corrected high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image shows the isolated distribution of Fe material, proving the single-atom morphology.

[0038] Example 2

[0039] Step S1: Dissolve 0.2g of multi-walled carbon nanotubes and 0.3g of phthalocyanine iron in 120ml of N,N-dimethylformamide and sonicate for 0.2h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 12h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol, and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 60℃ for 12h. After cooling to room temperature, obtain powder product material A2.

[0040] Step S2: Weigh 66.6 mg of material A2 obtained in step S1 and 33.3 mg of sodium hypophosphite, grind them thoroughly, transfer them to a quartz tube, and use Joule heat flash discharge at constant voltage (190V) for 2 seconds. Cool the product to room temperature to obtain material B2. When Joule heat flash discharge is used, the resistance is 2Ω; the voltage of flash discharge at constant voltage is 80V; the discharge time is 100ms and the temperature is 800℃.

[0041] Step S3: The material B2 obtained in step S2 is heated in an oil bath at 80°C for 12 hours with 1M H2SO4, then washed with deionized water until pH=7. The resulting product is transferred to a forced-air drying oven and dried at 80°C for 8 hours, then cooled to room temperature to obtain catalyst sample C2. Figure 2 The diagram shows the porous structure of the target product C2 catalyst prepared in Example 2. The adsorption / desorption curves, obtained using a nitrogen adsorption / desorption method, are typical type IV isotherms, indicating that the obtained product has a rich mesoporous structure, which is beneficial for exposing the active sites for the oxygen reduction reaction. The catalyst's specific surface area (BET) is 91.35 m² / g.

[0042] Example 3

[0043] Step S1: Dissolve 0.2g of multi-walled carbon nanotubes and 0.4g of cobalt phthalocyanine in 120ml of N,N-dimethylformamide and sonicate for 1.0h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 8h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 60℃ for 10h. After cooling to room temperature, obtain powder product material A3.

[0044] Step S2: Weigh 100 mg of material A3 obtained in step S1 and 33.3 mg of sodium hypophosphite, grind them thoroughly, transfer them to a quartz tube, and heat them at 1500°C for 1 second using Joule heat flash evaporation. Cool the product to room temperature to obtain material B3. When Joule heat flash evaporation is a staged heating, the resistance is 0.1 Ω; the holding time of the staged heating is 20 seconds; and the temperature is 1500°C.

[0045] Step S3: The material B3 obtained in step S2 was heated in an oil bath at 80°C for 12 hours using 1M H2SO4, then washed with deionized water until pH=7. The resulting product was transferred to a forced-air drying oven and dried at 80°C for 8 hours, then cooled to room temperature to obtain catalyst sample C3. Figure 2 As shown in the X-ray diffraction (XRD) patterns, the different metal catalysts all have only two distinct diffraction peaks, at 25.7° and 44.7°, which correspond to the C(002) and C(100) planes, respectively.

[0046] Example 4

[0047] Step S1: Dissolve 0.2g of multi-walled carbon nanotubes and 0.3g of nickel phthalocyanine in 120ml of N,N-dimethylformamide and sonicate for 0.8h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 12h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol, and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 100℃ for 6h. After cooling to room temperature, obtain powder product material A4.

[0048] Step S2: Weigh 100 mg of material A4 obtained in step S1 and 33.3 mg of sodium hypophosphite, grind them thoroughly, and transfer them to a quartz tube. Use Joule heat flash evaporation pulse discharge for 2 seconds to obtain the product. Cool the product to room temperature to obtain material B4. When Joule heat flash evaporation is pulse discharge, the resistance is 10.0 Ω; the number of discharges is 3; the discharge time is 2 seconds; the power supply voltage is 30 V; and the power supply current is 50 A.

[0049] Step S3: The material B4 obtained in step S2 is heated in an oil bath at 80°C for 12 hours with 1M H2SO4, then washed with deionized water until pH=7. The resulting product is transferred to a forced-air drying oven and dried at 80°C for 8 hours, and then cooled to room temperature to catalyst sample C4. Figure 4 ORR polarization curves of target products prepared with different metals in alkaline electrolytes show that, compared with commercial Pt / C, the ORR performance of catalysts with different metals is better than that of Pt / C. Figure 5 The OER polarization curves of the target products prepared with different metals in alkaline electrolytes show that, compared with commercial Pt / C, the OER performance of catalysts with different metals is similar to that of Pt / C.

[0050] Example 5

[0051] Step S1: Dissolve 0.2g of single-walled carbon nanotubes and 0.3g of copper phthalocyanine in 120ml of N,N-dimethylformamide and sonicate for 0.2h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 12h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol, and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 60℃ for 6h. After cooling to room temperature, obtain powder product material A5.

[0052] Step S2: Weigh 100 mg of material A5 obtained in step S1 and 33.3 mg of potassium phosphite, grind them thoroughly, and transfer them to a quartz tube. Cool the product obtained by Joule heating flash discharge to room temperature to obtain material B5. When Joule heating flash discharge is used, the resistance is 3 Ω; the voltage of flash discharge is 200 V; the discharge time is 2000 ms and the temperature is 4000 °C.

[0053] Step S3: The material B5 obtained in step S2 is heated in an oil bath at 80°C for 8 hours with 1M HCl, then washed with deionized water until pH=7. The obtained product is transferred to a forced-air drying oven and dried at 70°C for 12 hours, and then cooled to room temperature to catalyst sample C5. Figure 6 The half-wave potential histograms of the target products prepared by loading different metals show that the half-wave potentials of the catalysts loaded with different metals are all higher than those of Pt / C. Figure 7 The zinc-air constant current charge-discharge cycle diagram of the target product assembled in Example 2 shows that after 1000 cycles over 1000 hours, only a slight performance loss was observed, indicating that it has stable renewability.

[0054] Example 6

[0055] Step S1: Dissolve 0.2g of multi-walled carbon nanotubes and 0.3g of phthalocyanine iron in 120ml of N,N-dimethylformamide and sonicate for 0.2h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 12h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol, and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 90℃ for 11h. After cooling to room temperature, obtain powder product material A6.

[0056] Step S2: Weigh 66.6 mg of material A2 obtained in step S1 and 33.3 mg of sodium hypophosphite, grind them thoroughly, and transfer them to a quartz tube. Use Joule heating flash discharge, first perform a staged heating to 1000℃ for 10 s, then perform a flash discharge at constant voltage (130V) for 2 s to obtain the product. Cool to room temperature to obtain material B6. When Joule heating flash discharge is a combined discharge, the method of first performing a staged heating and then performing flash discharge is adopted, with a resistance of 0.5Ω; the staged heating holding time is 30 s; the temperature is 1000℃; the flash discharge voltage is 120V; the discharge time is 400 ms; and the temperature is 1300℃.

[0057] Step S3: The material B6 obtained in step S2 is heated in an oil bath at 80°C for 12 hours with 1M H2SO4, then washed with deionized water until pH=7. The obtained product is transferred to a forced-air drying oven and dried at 80°C for 8 hours, and then cooled to room temperature to obtain catalyst sample C6.

[0058] Example 7

[0059] Step S1: Dissolve 0.2g of multi-walled carbon nanotubes and 0.3g of cobalt phthalocyanine in 120ml of N,N-dimethylformamide and sonicate for 0.2h to mix thoroughly. Then transfer to a magnetic stirrer and stir at room temperature for 12h. Wash the resulting mixture sequentially with N,N-dimethylformamide, anhydrous ethanol, and deionized water. Transfer the resulting mixture to a vacuum drying oven and vacuum dry at 100℃ for 9h. After cooling to room temperature, obtain powder product material A7.

[0060] Step S2: Weigh 66.6 mg of material A2 obtained in step S1 and 33.3 mg of potassium hypophosphate, grind them thoroughly, and transfer them to a quartz tube. Use Joule heating flash discharge, first perform a staged heating at 800℃ for 20 s, then perform a flash discharge at constant voltage (180V) for 1 s to obtain the product. Cool to room temperature to obtain material B7. When Joule heating flash discharge is a combined discharge, the method of first performing a staged heating and then performing flash discharge is adopted, with a resistance of 4.0Ω; the staged heating holding time is 5 s; the temperature is 2000℃; the flash discharge voltage is 200V; the discharge time is 2000ms; and the temperature is 3000℃.

[0061] Step S3: The material B6 obtained in step S2 is heated in an oil bath at 80°C for 12 hours with 1M H2SO4, then washed with deionized water until pH=7. The obtained product is transferred to a forced-air drying oven and dried at 80°C for 8 hours, and then cooled to room temperature to obtain catalyst sample C7.

[0062] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. An ultrafast preparation method for a single-atom bifunctional oxygen catalyst, characterized in that, Includes the following steps: Step 1: Disperse metal phthalocyanine and carbon nanotubes in N,N-dimethylformamide and stir evenly. Wash with N,N-dimethylformamide, anhydrous ethanol and deionized water in sequence, and then vacuum dry to obtain powder material A. Step 2: Powder material A and phosphate are then subjected to Joule heat flash evaporation to obtain material B; Step 3: Finally, material B is acid-treated, washed at pH 7, and then vacuum dried to obtain a single-atom bifunctional oxygen catalyst.

2. The ultrafast preparation method of a single-atom bifunctional oxygen catalyst according to claim 1, characterized in that: Joule thermal flash evaporation includes: flash discharge, staged heating, pulse discharge, or a combination of discharges.

3. The ultrafast preparation method of a single-atom bifunctional oxygen catalyst according to claim 2, characterized in that: When Joule heating flash evaporation is a flash discharge, the resistance is 0.1 Ω to 10.0 Ω; the voltage of flash constant voltage discharge is 80 V to 200 V; the discharge time is 100 ms to 2000 ms; and the temperature is 800℃ to 4000℃. When Joule heating flash evaporation is a staged temperature rise, the resistance is 0.1 Ω to 10.0 Ω; The holding time for each stage of heating is 1 s to 60 s; the temperature is 800℃ to 3000℃. When Joule flash evaporation is a pulsed discharge, the resistance is 0.1 Ω to 10.0 Ω; the number of discharges is 1 to 5; the discharge time is 0.5 s to 2 s; the power supply voltage is 10 V to 36 V; and the power supply current is 10 A to 83 A.

4. The ultrafast preparation method of a single-atom bifunctional oxygen catalyst according to claim 2, characterized in that: When Joule heating flash evaporation is a combined discharge, a phased heating process is adopted followed by flash discharge. The resistance is 0.1 Ω to 10.0 Ω; the holding time of the phased heating is 1 s to 60 s; the temperature is 800℃ to 3000℃; the voltage of the flash constant voltage discharge is 80 V to 200 V; the discharge time is 100 ms to 2000 ms; and the temperature is 800℃ to 4000℃.

5. The ultrafast preparation method of a single-atom bifunctional oxygen catalyst according to claim 1, characterized in that: The mass ratio of metal phthalocyanine to carbon nanotubes is 1:0.5~2.5; the mass ratio of powder material A to phosphate is 1:1~10.

6. The ultrafast preparation method of a single-atom bifunctional oxygen catalyst according to claim 1, characterized in that: In step 1, metal phthalocyanine and carbon nanotubes are dispersed in N,N-dimethylformamide by ultrasonic dispersion for 0.2-1 h.

7. The ultrafast preparation method of a single-atom bifunctional oxygen catalyst according to claim 1, characterized in that: The vacuum drying temperature in steps 1 and 3 is 60℃~100℃, and the vacuum drying time is 6 h~12 h.

8. A single-atom bifunctional oxygen catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. The application of a single-atom bifunctional oxygen catalyst prepared by the preparation method according to any one of claims 1 to 7 in a zinc-air battery.

Images