Composite electrocatalyst based on polyurethane foam, preparation method and battery

Abstract

The invention discloses a composite electrocatalyst based on polyurethane foam, a preparation method and a battery. The composite electrocatalyst is nitrogen and sulfur co-doped carbon foam loaded with cobalt hydroxide nanosheets and CoP, and the specific surface area of the carbon foam is 186-211m < 2 > / g; the carbon foam is obtained by calcining a polyurethane foam-based transition metal composite material in an inert atmosphere at the temperature of 700-750 DEG C. According to the present invention, the cobalt hydroxide nanosheet and the cobalt phosphide are loaded so as to provide the rich self-supporting pore structure, such that the specific surface area of the electrocatalyst can be easily increased, and the cobalt hydroxide nanosheet and the cobalt phosphide are loaded so as to provide the rich adsorption site for the oxygen. Through co-doping of nitrogen and sulfur, the active sites of the electrocatalyst are further increased, and the kinetic efficiency of oxygen reduction reaction is improved. Moreover, in the oxygen reduction reaction process, the composite electrocatalyst is not prone to agglomeration, active substance falling and other problems, and therefore the circulation capacity of the oxygen reduction reaction can be improved.

Description

Technical Field

[0001] This application belongs to the field of zinc-air battery technology, specifically relating to a composite electrocatalyst based on polyurethane foam, its preparation method, and the battery. Background Technology

[0002] Existing zinc-air batteries use oxygen from the air as the positive electrode material. Under alkaline conditions, the basic reactions in zinc-air batteries include the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). However, current oxygen reduction catalysts have slow reaction kinetics, which is detrimental to improving the overall efficiency of zinc-air batteries. Moreover, oxygen reduction electrocatalysts exhibit poor stability and low energy density during the reaction process. Summary of the Invention

[0003] This application aims to address the shortcomings of existing related technologies by providing a composite electrocatalyst based on polyurethane foam, its preparation method, and a battery, which can improve the cycle stability of the catalyst in the oxygen reduction reaction process and has a high energy density.

[0004] The first aspect of this application provides a composite electrocatalyst based on polyurethane foam, wherein the composite electrocatalyst is a nitrogen- and sulfur-co-doped carbon foam supported on cobalt hydroxide nanosheets and CoP, and the specific surface area of ​​the carbon foam is 186-211 m². 2 / g; The carbon foam is obtained by calcining a polyurethane foam-based transition metal composite material in an inert atmosphere at 700-800℃. The carbon foam prepared from polyurethane foam achieves nitrogen and sulfur co-doping during high-temperature calcination. Calcination of the polyurethane foam-based transition metal composite material at 700-750℃ maintains the carbon foam structure and provides abundant self-supporting pore structures. At lower temperatures, the degree of graphitization is low, and self-supporting pore structures cannot be obtained. Through nitrogen and sulfur co-doping, in conjunction with cobalt hydroxide nanosheets and partially phosphated CoP, a high specific surface area is achieved, providing abundant active sites, which is beneficial for improving the activity of the oxygen reduction reaction.

[0005] The method for preparing the polyurethane foam includes reacting hexamethylene diisocyanate (HDI) or diphenylmethane diisocyanate (TDI) with polyethylene glycol (PEG, molecular weight 600) or polypropylene glycol (PPG, molecular weight 1000) at 40-80°C. Preferably, during the reaction, the molar ratio of isocyanate groups to hydroxyl groups can be controlled at 4-9, so that the obtained polyurethane foam can form a self-supporting carbon foam during the carbonization process.

[0006] Further, the reaction is carried out at 40-80℃ for 2-5 hours, and the obtained polyurethane foam is washed with deionized water and then freeze-dried to obtain polyurethane foam.

[0007] A second aspect of this application provides a method for preparing a composite electrocatalyst based on polyurethane foam. The method includes: reacting hexamethylene diisocyanate (HDI) or diphenylmethane diisocyanate (TDI) with polyethylene glycol (PEG) (molecular weight 600) or polypropylene glycol (PPG) (molecular weight 1000) at 40-80°C for 2-5 hours to obtain a first polyurethane foam having a stable pore structure.

[0008] Further, the first polyurethane foam is immersed in a sulfonate-type anionic surfactant solution for 30-50 minutes to obtain a second polyurethane foam. The sulfonate-type anionic surfactant is one of alkylbenzene sulfonate, lignin sulfonate, or alkyl sulfonate. Placing the first polyurethane foam in the sulfonate-type anionic surfactant solution results in a negatively charged surface, which is beneficial for subsequent adsorption of metal ions and also for providing sulfur for doping.

[0009] The second polyurethane foam is reacted with cobalt salt to prepare a third polyurethane foam, wherein cobalt hydroxide nanosheets are loaded onto the third polyurethane foam. Specifically, the preparation of the third polyurethane foam includes: dissolving cobalt nitrate hexahydrate and hexamethylenetetramine in deionized water to obtain a first solution, wherein the mass ratio of cobalt nitrate hexahydrate to the volume of deionized water is (0.5g-2.5g):(10-30ml), and the mass ratio of hexamethylenetetramine to the volume of deionized water is (0.5g-3.5g):(10-30ml).

[0010] Then, the second polyurethane foam is placed in the first solution and transferred to a reaction vessel. The reaction vessel is sealed and subjected to a hydrothermal reaction at 70-85°C for 3-6 hours to obtain a third polyurethane foam loaded with cobalt hydroxide nanosheets. The negatively charged second polyurethane foam adsorbs cobalt ions, thereby generating the third polyurethane foam loaded with cobalt hydroxide nanosheets.

[0011] After obtaining the third polyurethane foam, it is placed in an inert atmosphere and calcined at 700-800℃ to obtain nitrogen and sulfur co-doped carbon foam. The nitrogen and sulfur co-doped carbon foam is then phosphated in a phosphorus-containing atmosphere to obtain nitrogen and sulfur co-doped carbon foam loaded with cobalt hydroxide nanosheets and CoP. The inert atmosphere can be nitrogen, argon, etc. The specific steps of the phosphating include: placing a first predetermined mass of the third polyurethane foam and a second predetermined mass of anhydrous sodium hypophosphite in a tube furnace and heating under an inert atmosphere at 200-300℃ for 1-3 hours to obtain a composite electrocatalyst.

[0012] Furthermore, the first preset mass is 10-40 mg, and the second preset mass is 50-200 mg; the heating rate is 2-4 °C / min. By controlling the heating rate, it is beneficial to avoid problems such as agglomeration during phosphating, and to better maintain the morphology of the cobalt hydroxide nanosheets. Phosphating can increase the spacing between metals, which is beneficial to improving catalytic performance. The carbon foam framework obtained based on polyurethane foam, loaded with cobalt hydroxide nanosheets and some cobalt phosphide, is beneficial to providing more adsorption sites for hydrogen and oxygen.

[0013] A third aspect of this application provides a metal-air battery cathode material, wherein the cathode material is a polyurethane foam-based composite electrocatalyst as described in various embodiments of this application, or a loaded electrocatalyst prepared by the preparation method described in various embodiments of this application.

[0014] A fourth aspect of this application provides an all-solid-state zinc-air battery, the battery comprising the metal-air battery cathode material, zinc-platinum anode, and gel electrolyte described in the embodiments of this application. Specifically, the preparation method of the all-solid-state zinc-air battery includes: placing 1.0-2.0g of potassium hydroxide and 0.5-1.4g of zinc oxide in 30-60ml of deionized water, and then adding 0.4-0.6g of acrylic acid and 0.05-0.9g of methylenebisacrylamide, stirring and reacting for 3-8 minutes, then filtering the precipitate, and placing the supernatant in a container. Adding 40-90ul of potassium persulfate to the supernatant, and stirring to obtain a solid electrolyte. Taking a piece of acrylic tape of a certain size, cutting a 1cm section from the middle. 2 In the designated area, the metal-air battery cathode material and solid electrolyte are encapsulated together with acrylic tape to obtain an all-solid-state zinc-air battery.

[0015] The metal-air battery cathode material obtained based on this embodiment has a self-supporting pore structure, abundant active sites, and a large specific surface area, which further improves the cycle stability and power density of the all-solid-state zinc-air battery and solves the problem of low reaction efficiency of the all-solid-state zinc-air battery.

[0016] Beneficial effects

[0017] A carbon foam framework was obtained by calcining a polyurethane foam-based transition metal composite material at high temperature. This framework provides abundant self-supporting pore structures, which is beneficial for increasing the specific surface area of ​​the electrocatalyst. Cobalt hydroxide nanosheets and cobalt phosphide are loaded onto the framework, providing abundant adsorption sites for oxygen. Nitrogen and sulfur co-doping further increases the active sites of the electrocatalyst, which is beneficial for improving the kinetic efficiency of the oxygen reduction reaction. Furthermore, this composite electrocatalyst is less prone to agglomeration and active material shedding during the oxygen reduction reaction, thus improving the cycling capacity of the oxygen reduction reaction. Detailed Implementation

[0018] Example 1:

[0019] This embodiment provides a method for preparing a composite electrocatalyst based on polyurethane foam, including the following steps:

[0020] (1) The molar ratio of isocyanate group to hydroxyl group is 5. According to this molar ratio, 42g of hexamethylene diisocyanate and 30g of polyethylene glycol are reacted at 50°C for 3h. The product after reaction is then freeze-dried for 10h to obtain the first polyurethane foam.

[0021] (2) Weigh 5g of alkylbenzene sulfonate, dissolve it in 100ml of water, then immerse the first polyurethane foam in the alkylbenzene sulfonate solution, stir and react at room temperature for 30min, then take it out and freeze dry for 10h to obtain the second polyurethane foam.

[0022] (3) Dissolve 2g of cobalt nitrate hexahydrate and 2g of hexamethylenetetramine in 30ml of deionized water to obtain a cobalt salt solution, and stir thoroughly until dissolved. Add the second polyurethane foam to the reactor, and transfer the cobalt salt solution to the reactor. Perform a hydrothermal reaction at 70℃ for 5h. After cooling, wash with deionized water, and freeze-dry the cleaned material for 10h to obtain the third polyurethane foam.

[0023] (4) Place the third polyurethane foam in a tube furnace, introduce nitrogen gas beforehand, and heat the tube furnace at a heating rate of 5℃ / min until it reaches 700℃. Hold the temperature for 2 hours and then cool it to room temperature. Weigh 100mg of the carbonized third polyurethane foam and 500mg of anhydrous sodium hypophosphite. Place the anhydrous sodium hypophosphite at the upper air vent of the tube furnace and the carbonized third polyurethane foam at the lower air vent. Heat the tube furnace at a heating rate of 2℃ / min under a nitrogen atmosphere until it reaches 250℃. React at 250℃ for 2 hours and then cool it to room temperature to obtain nitrogen and sulfur co-doped carbon foam loaded with cobalt hydroxide nanosheets and CoP, which is taken as sample 1.

[0024] Example 2:

[0025] This embodiment provides a method for preparing a composite electrocatalyst based on polyurethane foam, including the following steps:

[0026] (1) The molar ratio of isocyanate group to hydroxyl group is 5. According to this molar ratio, 43.5g of diphenylmethane diisocyanate and 30g of polyethylene glycol are reacted at 80°C for 3h. The product after reaction is then freeze-dried for 10h to obtain the first polyurethane foam.

[0027] (2) Weigh 5g of alkyl sulfonate, dissolve it in 100ml of water, then immerse the first polyurethane foam in the alkyl sulfonate solution, stir and react at room temperature for 30min, then take it out and freeze dry for 10h to obtain the second polyurethane foam.

[0028] (3) Dissolve 2.5g of cobalt nitrate hexahydrate and 3.0g of hexamethylenetetramine in 20ml of deionized water to obtain a cobalt salt solution, and stir thoroughly until dissolved. Add the second polyurethane foam to the reactor, and transfer the cobalt salt solution to the reactor. Perform a hydrothermal reaction at 80℃ for 5h. After cooling, wash with deionized water, and freeze-dry the cleaned material for 10h to obtain the third polyurethane foam.

[0029] (4) Place the third polyurethane foam in a tube furnace, introduce nitrogen gas beforehand, and heat the tube furnace at a heating rate of 5℃ / min until it reaches 750℃. Hold the temperature for 2 hours and then cool it to room temperature. Weigh 100mg of the carbonized third polyurethane foam and 500mg of anhydrous sodium hypophosphite. Place the anhydrous sodium hypophosphite at the upper air vent of the tube furnace and the carbonized third polyurethane foam at the lower air vent. Heat the tube furnace at a heating rate of 2℃ / min under a nitrogen atmosphere until it reaches 250℃. React at 250℃ for 2 hours and then cool it to room temperature to obtain nitrogen and sulfur co-doped carbon foam loaded with cobalt hydroxide nanosheets and CoP, which is sample 2.

[0030] Comparative Example 1:

[0031] (1) Dissolve 2g of cobalt nitrate hexahydrate and 2g of hexamethylenetetramine in 30ml of deionized water to obtain a cobalt salt solution, and stir thoroughly until dissolved. Add nickel foam to the reactor and transfer the cobalt salt solution to the reactor. Perform hydrothermal reaction at 70℃ for 5h. After cooling, wash with deionized water and freeze-dry the cleaned material for 10h to obtain nickel foam loaded with cobalt hydroxide.

[0032] (2) Place the nickel foam loaded with cobalt hydroxide in a tube furnace, purge with nitrogen beforehand, and heat the tube furnace at a heating rate of 5℃ / min until it reaches 700℃. Hold the temperature for 2 hours and then cool to room temperature. Weigh 100 mg of calcined nickel foam loaded with cobalt hydroxide and 500 mg of anhydrous sodium hypophosphite. Place the anhydrous sodium hypophosphite at the upper air vent of the tube furnace and the nickel foam loaded with cobalt hydroxide at the lower air vent. Heat the tube furnace at a heating rate of 2℃ / min under a nitrogen atmosphere until it reaches 250℃. React at 250℃ for 2 hours and then cool to room temperature to obtain nickel foam loaded with cobalt hydroxide and cobalt phosphide, which serves as a control sample.

[0033] Performance testing:

[0034] (I) The oxygen reduction performance (ORR) of Sample 1, Sample 2 and the control sample were tested using an electrochemical workstation and a rotating disk electrode, respectively. The test conditions were 0.1 mol / L potassium hydroxide solution, a rotation speed of 1600 rpm and a scan rate of 5 mV s⁻¹. The test results are shown in Table 1.

[0035] Table 1 ORR Performance Test

[0036]

[0037] Conclusion: The data in Table 1 show that using polyurethane foam as a carbon skeleton to achieve nitrogen and sulfur co-doping can provide abundant active sites for the reaction of active substances, and the oxygen reduction reaction performance is relatively excellent, with a high onset potential and a large power density.

[0038] (II) Solid-state zinc-air batteries were prepared using Sample 1, Sample 2, and the control sample as catalysts, respectively, as follows:

[0039] Add 1.0 g potassium hydroxide and 1.0 g zinc oxide to 30 ml of deionized water, then add 0.5 g acrylic acid and 0.1 g methylenebisacrylamide. Stir for 5 min, then filter the precipitate and place the supernatant in a container. Add 50 μL of potassium persulfate solution (0.7 mol / L) to the supernatant and stir to obtain a solid electrolyte. Take a piece of acrylic tape of a certain size and cut a 1 cm section from the middle. 2 In the designated area, the metal-air battery cathode material and solid electrolyte are encapsulated together with acrylic tape to obtain an all-solid-state zinc-air battery.

[0040] The power density and stability of the all-solid-state zinc-air battery were tested using the Blue Electric testing system. All tests were performed at room temperature, and the results are shown in Table 2.

[0041] Table 2 Performance Tests of All-Solid-State Zinc-Air Batteries

[0042]

[0043] As can be seen, the all-solid-state zinc-air batteries prepared by samples 1 and 2 in the embodiments of this application have high power density and high stability.

[0044] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

Claims

1. A polyurethane foam based composite electrocatalyst characterized in that, The composite electrocatalyst is a nitrogen and sulfur co-doped carbon foam loaded with cobalt hydroxide nanosheets and CoP, the specific surface area of the carbon foam is 186-211 m 2 / g; the carbon foam is obtained by calcining a polyurethane foam-based transition metal composite in an inert atmosphere at 700-750°C.

2. The composite electrocatalyst of claim 1, wherein The preparation method of the polyurethane foam comprises: reacting hexamethylene diisocyanate or diphenyl methane diisocyanate with polyethylene glycol or polypropylene glycol at 40-80℃.

3. A method for the preparation of a composite electrocatalyst based on polyurethane foam, characterized by, The preparation method comprises: The first polyurethane foam is prepared by reacting hexamethylene diisocyanate or diphenyl methane diisocyanate with polyethylene glycol or polypropylene glycol at 40-80℃; The first polyurethane foam is immersed in a sulfonate anionic surfactant solution, and after 30-50min, the second polyurethane foam is obtained; The second polyurethane foam is reacted with a cobalt salt to obtain the third polyurethane foam, wherein the third polyurethane foam is loaded with cobalt hydroxide nanosheets; The third polyurethane foam is calcined at 700-800℃ under an inert atmosphere to obtain nitrogen and sulfur co-doped carbon foam; The nitrogen and sulfur co-doped carbon foam is phosphorized in a phosphorus-containing atmosphere to obtain nitrogen and sulfur co-doped carbon foam loaded with cobalt hydroxide nanosheets and CoP.

4. The production method according to claim 3, characterized by, The sulfonate anionic surfactant is one of alkyl benzene sulfonate, lignin sulfonate and alkyl sulfonate.

5. The preparation method according to claim 3, characterized in that, The third polyurethane foam is prepared specifically by: Dissolving cobalt nitrate hexahydrate and methenamine in deionized water to obtain a first solution; The second polyurethane foam is placed in the first solution and transferred to a reaction kettle, the reaction kettle is sealed, and a hydrothermal reaction is carried out at 70-85℃ to obtain the third polyurethane foam loaded with cobalt hydroxide nanosheets.

6. The preparation method according to claim 3, characterized in that, The phosphorization specifically comprises: A first predetermined mass of the third polyurethane foam and a second predetermined mass of anhydrous sodium hypophosphite are placed in a tube furnace and heated under an inert atmosphere, and after being reacted at 200-300℃ for 1-3h, a polyurethane foam-based transition metal composite material is obtained.

7. The preparation method according to claim 6, characterized in that, The first predetermined mass is 10-40mg, and the second predetermined mass is 50-200mg.

8. The preparation method according to claim 6, characterized in that, The inert atmosphere is nitrogen, and the heating rate is 2-4℃ / min.

9. A metal-air battery cathode material, characterized in that, The cathode material is the polyurethane foam-based composite electrocatalyst of claim 1 or 2, or the loaded electrocatalyst prepared by the preparation method of any one of claims 3-8.

10. A solid-state zinc-air battery, characterized by, The battery comprises the metal-air battery cathode material of claim 9, an anode zinc platinum and a gel electrolyte.

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