Cobalt-manganese bimetallic oxide OER catalyst and application thereof in zinc-air battery

Abstract

The invention relates to the technical field of oxygen evolution reaction, and discloses a cobalt-manganese bimetallic oxide OER catalyst and application in a zinc-air battery, water, a cobalt salt, a manganese salt and a polyethylene glycol copolymer are added into a hydrothermal reaction kettle, a precipitant is added after stirring, a reaction is performed, a product is calcined in a resistance furnace, and the cobalt-manganese bimetallic oxide OER catalyst is obtained. The OER catalyst is composed of the cobalt-manganese bimetallic oxide and the nitrogen-sulfur doped carbon matrix, after nitrogen and sulfur co-doping of the carbon matrix, the conductivity is better, the wettability with an electrolyte is improved, migration and diffusion of electrons and ions in an oxygen evolution reaction are accelerated, meanwhile, catalytic active centers such as pyridine nitrogen and pyrrole nitrogen are formed, the oxygen evolution reaction is promoted, and the oxygen evolution reaction efficiency is improved. Meanwhile, the specific surface area is higher, more oxygen evolution reaction active sites are exposed, and the oxygen evolution reaction catalytic activity is better.

Description

Technical Field

[0001] The invention relates to the technical field of oxygen evolution reaction, and in particular to a cobalt-manganese bimetallic oxide OER catalyst and application thereof in a zinc-air battery. Background Art

[0002] Zinc-air batteries have the advantages of small size, light weight, and large charge capacity. They are green and environmentally friendly batteries with great development prospects. The two most important reactions in zinc-air batteries are the ORR oxygen reduction reaction and the OER oxygen evolution reaction. Among them, the energy barrier in the OER oxygen evolution reaction is very large, and the electrochemical reaction rate and efficiency are low, which affects the electrochemical performance of zinc-air batteries. At present, the OER oxygen evolution reaction is mainly based on precious metal catalysts such as platinum and ruthenium. The development of cheap and readily available transition metal catalysts is a research hotspot.

[0003] Cobalt manganese oxide has bimetallic catalytic active centers, and its preparation methods are diverse, its structure is controllable, and its raw material sources are broad. It has been widely studied in OER oxygen evolution catalysts. Patent CN110508308B discloses a preparation method and application of a CoMn-P-NCNT multifunctional catalyst, which uses cobalt salts, manganese salts, ammonium fluoride, phosphorus sources, dopamine hydrochloride, urea and other raw materials to achieve nitrogen and phosphorus doped carbon nanotubes to coat cobalt atomic particles, and manganese oxide is attached around the carbon nanotubes. The obtained catalyst has good catalytic activity such as OER and ORR. Increasing the specific surface area of ​​the catalyst and doping the carbon-based carrier of the catalyst with nitrogen, sulfur and other heteroelements can improve the catalyst's OER oxygen evolution and other reaction activities. Summary of the invention

[0004] Technical problem to be solved: The present invention provides a cobalt-manganese bimetallic oxide OER catalyst with large specific surface area and high catalytic activity for zinc-air batteries.

[0005] Technical solution: A method for preparing a cobalt-manganese bimetallic oxide OER catalyst: Step A: Add xylene, polyethylene glycol, 2-formyl naphthalene diimide and p-toluenesulfonic acid into a flask equipped with a water separator, stir and react at 110-130° C. for 2-3 hours, rotary evaporate, wash with methanol and dry to obtain a polyethylene glycol copolymer.

[0006] Step B: Add water, cobalt salt, manganese salt, and polyethylene glycol copolymer to a hydrothermal reactor, stir and add a precipitant, react at 100-120°C for 12-18h, cool and filter, wash with ethanol and water in turn, and dry the product in a resistance furnace, first in an air atmosphere, heat to 280-300°C, keep warm and calcine for 2-3h; then in a nitrogen atmosphere, heat to 600-700°C, keep warm and calcine for 1.5-2.5h, cool, and obtain a cobalt-manganese bimetallic oxide OER catalyst. The preparation reaction formula is as follows: .

[0007] Wherein, in step A, the ratio of polyethylene glycol, 2-formylthienylnaphthalene diimide and p-toluenesulfonic acid is 1 mol: (1-1.2) mol: (0.002-0.003) mol.

[0008] Wherein, the ratio of cobalt salt, manganese salt, polyethylene glycol copolymer and precipitant in step B is 2 mol:1 mol:(300-600) g:(5-8) mol.

[0009] Wherein, the cobalt salt is cobalt chloride or cobalt nitrate, and the manganese salt is manganese chloride or manganese nitrate.

[0010] Wherein, the precipitant in step B is urea or hexamethylenetetramine.

[0011] Among them, the preparation method of 2-formic acid thienyl naphthalene diimide is: add N, N-dimethylformamide, 1,4,5,8-naphthalenetetracarboxylic anhydride, 5-aminothiophene-2-carboxylic acid methyl ester, and triethylamine in a flask equipped with a condensation reflux tube in a ratio of 1 mol: (2.2-2.6) mol: (2.5-3) mol, heat to 120-135°C in a nitrogen atmosphere, stir and react for 6-12 hours, add water to dilute the solution, filter and wash the filter cake with acetone, add the dried product to methanol, add a potassium hydroxide solution with a concentration of 3.5-4 mol / L, heat to 85-95°C, condense and reflux for 4-6 hours, cool and add hydrochloric acid solution dropwise, precipitate, filter, wash with water, and dry to obtain 2-formic acid thienyl naphthalene diimide. The preparation reaction formula is as follows: .

[0012] Among them, cobalt-manganese bimetallic oxide OER catalysts are used in zinc-air batteries.

[0013] Technical effect: The present invention utilizes 2-carboxylic acid thiophenyl naphthalene diimide and polyethylene glycol to undergo an esterification polymerization reaction to obtain a polyethylene glycol copolymer containing naphthalene diimide and thiophene structures, and uses the naphthalene diimide as a surfactant and a structure-directing agent, cobalt chloride or cobalt nitrate as a cobalt salt, manganese chloride or manganese nitrate as a manganese source, and hexamethylenetetramine or the like as a precipitant, and undergoes a hydrothermal reaction to generate a cobalt-manganese precursor. Then, during a high-temperature calcination process, a highly carbon-forming and rigid naphthalene diimide ring is used as a carbon source and a nitrogen source, and thiophene is used as a sulfur source. The calcination and carbonization generate a nitrogen- and sulfur-coated carbon matrix, and the cobalt-manganese precursor generates a cobalt-manganese bimetallic oxide MnCo2O4 and is loaded into the carbon matrix. At the same time, the polyethylene glycol copolymer plays the role of a structure-directing agent. The generated cobalt-manganese bimetallic oxide forms a regular porous nanoflower structure with good dispersibility and a larger specific surface area, which is beneficial to increasing the OER oxygen reduction catalytic active sites.

[0014] The OER catalyst of the present invention is composed of cobalt-manganese bimetallic oxide and nitrogen-sulfur doped carbon matrix. After the carbon matrix is ​​co-doped with nitrogen and sulfur, the conductivity is better and the wettability with the electrolyte is increased, which is conducive to accelerating the migration and diffusion of electrons and ions in the oxygen evolution reaction. At the same time, pyridine nitrogen, pyrrole nitrogen and other catalytic active centers are formed to promote the oxygen evolution reaction. In addition, the OER catalyst has a higher specific surface area, exposing more active sites for the oxygen evolution reaction, and thus has better catalytic activity for the oxygen evolution reaction. Only an overpotential of 193-231mV is required to reach 10 mA / cm 2 The current density is 2.37 W and the Tafel slope value is only 60.8-73.7 mV / dec. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a scanning electron microscope image of the cobalt-manganese bimetallic oxide OER catalyst. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0017] Embodiment 1: (1) Add 50 mL of N,N-dimethylformamide, 8 mmol of 1,4,5,8-naphthalenetetracarboxylic anhydride, 20.8 mmol of 5-aminothiophene-2-carboxylic acid methyl ester and 24 mmol of triethylamine to a flask equipped with a condenser reflux tube, heat to 135°C in a nitrogen atmosphere, and stir to react for 6 h. Add water to dilute the solution, filter and wash the filter cake with acetone, add the dried product to 150 mL of methanol, add 100 mL of 3.5 mol / L potassium hydroxide solution, heat to 95°C, condense and reflux to react for 4 h, cool and slowly add hydrochloric acid solution dropwise, stir until a large amount of precipitate is precipitated, filter, wash with water and dry to obtain 2-carboxylic acid thienylnaphthalene diimide.

[0018] (2) In a flask equipped with a water separator, 20 mL of xylene, 10 mmol of polyethylene glycol 2000, 10 mmol of 2-thienylnaphthalene diimide, and 0.02 mmol of p-toluenesulfonic acid were added, and the mixture was stirred at 120° C. for 3 h. The mixture was rotary evaporated, washed with methanol, and dried to obtain a polyethylene glycol copolymer.

[0019] (3) Add 3 L of water, 60 mmol of cobalt chloride, 30 mmol of manganese chloride, and 9 g of polyethylene glycol copolymer into a hydrothermal reactor, stir, then add 170 mmol of precipitant hexamethylenetetramine, react at 110 °C for 18 h, cool and filter, wash with ethanol and water in turn, and dry the product in a resistance furnace, first heat to 280 °C in an air atmosphere and calcine for 4 h; then heat to 650 °C in a nitrogen atmosphere and calcine for 2 h, cool to obtain a cobalt-manganese bimetallic oxide OER catalyst.

[0020] Embodiment 2: (1) Add 50 mL of N,N-dimethylformamide, 8 mmol of 1,4,5,8-naphthalenetetracarboxylic anhydride, 17.6 mmol of 5-aminothiophene-2-carboxylic acid methyl ester and 20 mmol of triethylamine to a flask equipped with a condenser reflux tube, heat to 120°C in a nitrogen atmosphere, and stir to react for 12 h. Add water to dilute the solution, filter and wash the filter cake with acetone, add the dried product to 150 mL of methanol, add 120 mL of 4 mol / L potassium hydroxide solution, heat to 85°C, condense and reflux for 6 h, cool and slowly add hydrochloric acid solution dropwise, stir until a large amount of precipitate is precipitated, filter, wash with water and dry to obtain 2-carboxylic acid thienylnaphthalene diimide.

[0021] (2) In a flask equipped with a water separator, 30 mL of xylene, 10 mmol of polyethylene glycol 2000, 12 mmol of 2-thienylnaphthalene diimide, and 0.03 mmol of p-toluenesulfonic acid were added, and the mixture was stirred at 110° C. for 12 h. The mixture was rotary evaporated, washed with methanol, and dried to obtain a polyethylene glycol copolymer.

[0022] (3) 4 L of water, 60 mmol of cobalt nitrate, 30 mmol of manganese nitrate, and 12 g of polyethylene glycol copolymer were added to a hydrothermal reactor. After stirring, 150 mmol of precipitant hexamethylenetetramine was added. The mixture was reacted at 100 °C for 18 h. After cooling, the mixture was filtered and washed with ethanol and water in turn. After drying, the product was heated to 300 °C in an air atmosphere in a resistance furnace and calcined for 3 h. Then, the temperature was raised to 600 °C in a nitrogen atmosphere and calcined for 2.5 h. The product was cooled to obtain a cobalt-manganese bimetallic oxide OER catalyst.

[0023] Embodiment 3: (1) In a flask equipped with a water separator, 30 mL of xylene, 10 mmol of polyethylene glycol 2000, 12 mmol of 2-carboxylic acid thienyl naphthalene diimide (prepared in Example 1), and 0.023 mmol of p-toluenesulfonic acid were added, and the mixture was stirred at 110° C. for 3 h. The mixture was rotary evaporated, washed with methanol, and dried to obtain a polyethylene glycol copolymer.

[0024] (2) Add 4 L of water, 60 mmol of cobalt nitrate, 30 mmol of manganese nitrate, and 15 g of polyethylene glycol copolymer into a hydrothermal reactor, stir, then add 150 mmol of precipitant hexamethylenetetramine, react at 100 °C for 18 h, cool and filter, wash with ethanol and water in turn, and dry the product in a resistance furnace, first heat to 280 °C in an air atmosphere and calcine for 3 h; then heat to 600 °C in a nitrogen atmosphere and calcine for 2.5 h, cool to obtain a cobalt-manganese bimetallic oxide OER catalyst.

[0025] Embodiment 4: (1) In a flask equipped with a water separator, 20 mL of xylene, 10 mmol of polyethylene glycol 2000, 11 mmol of 2-carboxylic acid thienylnaphthalene diimide (prepared in Example 1), and 0.026 mmol of p-toluenesulfonic acid were added, and the mixture was stirred at 130° C. for 2 h. The mixture was rotary evaporated, washed with methanol, and dried to obtain a polyethylene glycol copolymer.

[0026] (2) Add 5 L of water, 60 mmol of cobalt chloride, 30 mmol of manganese chloride, and 18 g of polyethylene glycol copolymer into a hydrothermal reactor, stir, add 240 mmol of precipitant urea, react at 110 °C for 12 h, cool and filter, wash with ethanol and water in turn, and dry the product in a resistance furnace, first heat to 280 °C in an air atmosphere and calcine for 3 h; then heat to 700 °C in a nitrogen atmosphere and calcine for 1.5 h, cool to obtain a cobalt-manganese bimetallic oxide OER catalyst.

[0027] Comparative Example 1: (1) Add 3 L of water, 60 mmol of cobalt chloride, and 30 mmol of manganese chloride into a hydrothermal reactor, stir, then add 170 mmol of precipitant hexamethylenetetramine, react at 110 °C for 18 h, cool and filter, wash with ethanol and water in turn, and dry the product in a resistance furnace, first heat to 280 °C in an air atmosphere and calcine for 4 h; then heat to 650 °C in a nitrogen atmosphere and calcine for 2 h, cool, and obtain a cobalt-manganese bimetallic oxide OER catalyst.

[0028] Comparative Example 2: (1) Add 3 L of water, 60 mmol of cobalt chloride, 30 mmol of manganese chloride, and 9 g of polyethylene glycol 2000 into a hydrothermal reactor, stir, then add 170 mmol of precipitant hexamethylenetetramine, react at 110 °C for 18 h, cool and filter, wash with ethanol and water in turn, and dry the product in a resistance furnace, first heat to 280 °C in an air atmosphere and calcine for 4 h; then heat to 650 °C in a nitrogen atmosphere and calcine for 2 h, cool, and obtain a cobalt-manganese bimetallic oxide OER catalyst.

[0029] The specific surface area of ​​the cobalt-manganese bimetallic oxide OER catalyst was determined by a specific surface area and porosity analyzer using a nitrogen adsorption-desorption method. The electrode material was vacuum degassed at 150°C for 12 h before the test.

[0030] Table 1 Specific surface area test

[0031] Figure 1 The scanning electron microscope images show that the cobalt-manganese bimetallic oxide OER catalyst obtained in Example 1 and Comparative Example 2, using polyethylene glycol copolymer and polyethylene glycol as surfactants and structure-directing agents, respectively, exhibits a regular porous nanoflower structure, good dispersibility, and a larger specific surface area, which is beneficial to increasing the catalytic active sites. The cobalt-manganese bimetallic oxide OER catalyst in Comparative Example 1 exhibits irregular agglomerates and a small specific surface area.

[0032] The cobalt-manganese bimetallic oxide OER catalyst was added to ethanol and ultrasonically dispersed. Then, Nafion solution was added and the slurry was coated on the surface of the glassy carbon electrode. The catalyst loading was 0.5 mg / cm 2 The oxygen evolution reaction activity test was carried out in an electrochemical workstation with a platinum electrode as the counter electrode, Ag / AgCl as the reference electrode, and a 0.1 mol / L potassium hydroxide solution as the electrolyte. The scan rate was 10 mV / s.

[0033] Table 2 Oxygen evolution reaction activity test

[0034] After testing, the cobalt-manganese bimetallic oxide OER catalysts of Examples 1-4 only require an overpotential of 193-231 mV to reach 10 mA / cm 2 The current density is 2.377 mV / dec, and the Tafel slope value is only 60.8-73.7 mV / dec, which is significantly lower than that of Comparative Examples 1 and 2. This is because the OER catalysts of Examples 1-4 are composed of cobalt-manganese bimetallic oxides and nitrogen-sulfur-doped carbon matrices. After the carbon matrix is ​​co-doped with nitrogen and sulfur, the conductivity is better, and the wettability with the electrolyte is increased, which is conducive to accelerating the migration and diffusion of electrons and ions in the oxygen evolution reaction, while forming catalytic active centers such as pyridinic nitrogen and pyrrolic nitrogen, promoting the oxygen evolution reaction, and the OER catalyst has a higher specific surface area, exposing more active sites for the oxygen evolution reaction, and thus has better catalytic activity for the oxygen evolution reaction.

[0035] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a cobalt-manganese bimetallic oxide OER catalyst, characterized in that: The preparation method comprises the following steps: Step A, adding xylene, polyethylene glycol, 2-formyl naphthalene diimide and p-toluenesulfonic acid into a flask equipped with a water separator, stirring for reaction, rotary evaporation, washing and drying to obtain a polyethylene glycol copolymer; Step B, adding water, cobalt salt, manganese salt, and polyethylene glycol copolymer into a hydrothermal reactor, adding a precipitant after stirring, reacting, filtering after cooling, washing, and drying, calcining the product in a resistance furnace, and cooling to obtain a cobalt-manganese bimetallic oxide OER catalyst.

2. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 1, characterized in that: In the step A, the ratio of polyethylene glycol, 2-formylthienylnaphthalene diimide and p-toluenesulfonic acid is 1 mol: (1-1.2) mol: (0.002-0.003) mol.

3. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 1, characterized in that: The reaction in step A is carried out at 110-130° C. for 2-3 hours.

4. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 1, characterized in that: In the step B, the ratio of the cobalt salt, the manganese salt, the polyethylene glycol copolymer and the precipitant is 2 mol:1 mol:(300-600) g:(5-8) mol.

5. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 4, characterized in that: The cobalt salt is cobalt chloride or cobalt nitrate, and the manganese salt is manganese chloride or manganese nitrate.

6. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 4, characterized in that: In the step B, the precipitant is urea or hexamethylenetetramine.

7. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 1, characterized in that: The reaction in step B is carried out at 100-120° C. for 12-18 hours.

8. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 1, characterized in that: In step B, the calcination is first carried out in an air atmosphere at 280-300° C. for 2-3 hours; and then in a nitrogen atmosphere at 600-700° C. for 1.5-2.5 hours.

9. The method for preparing the cobalt-manganese bimetallic oxide OER catalyst according to claim 2, characterized in that: The preparation method of the 2-formic acid thienyl naphthalene diimide is as follows: N,N-dimethylformamide, 1,4,5,8-naphthalenetetracarboxylic anhydride, 5-aminothiophene-2-carboxylic acid methyl ester and triethylamine are added to a flask equipped with a condensation reflux tube in a ratio of 1 mol: (2.2-2.6) mol: (2.5-3) mol, the temperature is raised to 120-135° C. in a nitrogen atmosphere, the mixture is stirred for reaction for 6-12 hours, water is added to the solution for dilution, the filter cake is washed with acetone after filtering, the dried product is added to methanol, a potassium hydroxide solution with a concentration of 3.5-4 mol / L is added, the temperature is raised to 85-95° C., the mixture is condensed and refluxed for reaction for 4-6 hours, a hydrochloric acid solution is added dropwise after cooling, a precipitate is precipitated, the precipitate is filtered, washed and dried to obtain the 2-formic acid thienyl naphthalene diimide.

10. Use of the cobalt-manganese bimetallic oxide OER catalyst obtained by the preparation method according to any one of claims 1 to 9 in a zinc-air battery.

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