A carbon nanotube network-supported hydroxyl oxide, its preparation method and application

Abstract

This invention relates to a carbon nanotube network-supported hydroxyl oxide, wherein the microstructure of the carbon nanotube network-supported hydroxyl oxide consists of irregularly shaped clusters of hydroxyl oxide coated with carbon nanotubes; wherein the size of the hydroxyl oxide is 0.5–2 μm, and the diameter of a single carbon nanotube is 10–50 nm. The invention also provides a method for preparing the carbon nanotube network-supported hydroxyl oxide, and its application as a catalyst in the air electrode of a metal-air battery, wherein it is coated onto the positive electrode carbon paper / carbon cloth of the metal-air battery. The carbon nanotube network-supported hydroxyl oxide, its preparation method, and its application provided in the above technical solution can effectively improve the problem of slow reaction kinetics at the positive electrode of metal-air batteries.

Description

Technical Field

[0001] This invention relates to the field of metal-air battery technology, specifically to a carbon nanotube network-supported hydroxyl oxide, its preparation method, and its application in metal-air batteries. Background Technology

[0002] Current energy supplies are insufficient to meet the new energy demands brought about by technological advancements. Social progress also necessitates the development of safer, more stable, and renewable clean energy sources, as well as more cost-effective energy storage devices. The lithium-ion battery era has provided powerful range assurance for various portable electronic devices and is the primary choice for most electric vehicles. While lithium-ion batteries have achieved significant commercial success, numerous technological challenges remain. High manufacturing costs and low energy density clearly cannot meet future practical needs, and lithium-ion batteries themselves also pose numerous safety hazards. Therefore, researchers have begun searching for alternatives.

[0003] Among the many types of batteries, aqueous metal (zinc, iron, magnesium, aluminum, lithium)-air batteries have gradually attracted attention, especially zinc-air and aluminum-air batteries, which have become promising candidate batteries. Compared with lithium metal, zinc and aluminum metals are abundant in nature, and their extraction costs are lower and more environmentally friendly. Zinc / aluminum-air batteries have attracted increasing research in recent years due to their higher theoretical energy density, lower manufacturing costs, and inherent safety advantages. However, the inherently slow kinetics of the oxygen evolution and oxygen reduction reactions during the charging and discharging process at the positive electrode result in suboptimal performance and a shorter lifespan, which has become the biggest limitation to commercial development.

[0004] Therefore, based on their significant resource and cost advantages, people have been exploring efficient and durable bifunctional catalysts that combine oxygen reduction reaction and oxygen evolution reaction performance to improve the problem of slow kinetics and obtain good performance. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon nanotube network-supported hydroxyl oxide, its preparation method and application, which can effectively improve the problem of slow cathode reaction kinetics in metal-air batteries.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A carbon nanotube network-loaded hydroxy oxide, wherein the microstructure of the carbon nanotube network-loaded hydroxy oxide is carbon nanotubes coating irregularly clustered hydroxy oxides; wherein the size of the hydroxy oxides is 0.5~2μm, and the diameter of a single carbon nanotube is 10~50 nm.

[0008] Meanwhile, this invention also discloses a method for preparing the above-mentioned carbon nanotube network-supported hydroxyl oxide, comprising the following steps:

[0009] Step S1. Dissolve hydrogen peroxide-treated graphene oxide, ferric nitrate nonahydrate, and melamine in deionized water. Evaporate the liquid by high-temperature stirring to form a solid powder. Then, carbonize the obtained powder under an argon atmosphere to obtain Fe-CNTs-rGO. The mass ratio of graphene oxide, ferric nitrate nonahydrate, and melamine is 1~5:10~20:900~1500, preferably 1:10:900. The evaporation temperature is 50~100℃, preferably 95℃. The carbonization process is as follows: first maintain at 400~500℃ for 1~5 hours under an argon atmosphere, then maintain at 700~1100℃ for 1~5 hours, with a heating rate of 1~20 degrees / minute. The preferred carbonization process is: first maintain at 400℃ for 1 hour under an argon atmosphere, then maintain at 900℃ for 2 hours, with a heating rate of 5 degrees / minute.

[0010] Step S2. Under alkaline conditions, a transition metal salt is coordinated to generate a hydroxy oxide, which is then loaded onto the above Fe-CNTs-rGO to obtain MOOH / Fe-CNTs-rGO.

[0011] Step S2 specifically includes the following steps:

[0012] Fe-CNTs-rGO was dispersed in deionized water and sonicated for 1-5 hours to form solution A.

[0013] Then, nickel nitrate and ferric nitrate in a mass ratio of 2~4:1~4 are dissolved in deionized water to form solution B;

[0014] Sodium carbonate and sodium hydroxide in a mass ratio of 1~3:1~5 are dissolved in deionized water to form solution C;

[0015] The above-mentioned solutions B and C are simultaneously and slowly added dropwise to solution A while it is being stirred to form solution D; solution D is alkaline with a pH of 8-13, preferably pH 10.

[0016] The stirring environment of liquid D is at room temperature. After stirring for 12 to 48 hours, it is centrifuged 3 to 5 times. The liquid used for centrifugation is ethanol. After centrifugation, it is vacuum dried at 60 to 80 degrees for 2 to 24 hours to obtain carbon nanotube network-supported hydroxyl oxides.

[0017] An application of the above-mentioned carbon nanotube network-supported hydroxyl oxide as a catalyst for the air electrode of a metal-air battery; the catalyst layer is coated on the positive electrode carbon paper / carbon cloth of the metal-air battery, and the catalyst loading is 0.5 mg / cm³. 2The metal in a metal-air battery is aluminum, lithium, magnesium, iron, or zinc. When carbon nanotube networks loaded with hydroxyl oxides are used as the positive electrode catalyst layer in a zinc-air battery, they need to be dispersed in ethanol and aqueous solution at a ratio of 1:1, and the ratio of carbon nanotube network-loaded hydroxyl oxides to liquid is 10 mg / mL.

[0018] The above-mentioned technical solution provides a carbon nanotube network-supported transition metal hydroxy oxide and a preparation method. Nitrogen-doped graphene and nickel-based hydroxy oxide have high ORR and OER electrocatalytic activities, respectively. By coating nitrogen-doped graphene onto nickel-based hydroxy oxide, the advantages of the two types of materials in electrocatalytic applications can be combined to prepare a bifunctional catalyst with both ORR and OER electrocatalytic activities, which can then be applied in metal-air batteries.

[0019] Using the carbon nanotube network of this invention to support transition metal hydroxyl oxides as the positive electrode catalyst material for a metal-air battery, a metal-air battery is assembled. Under alkaline conditions, the positive electrode reaction of the reversible metal-air battery is: O2 + 2H2O + 4e- − ↔ 4OH − During discharge, the oxygen reduction reaction (ORR) occurs at the positive electrode. During charging, the oxygen evolution reaction (OER) occurs at the positive electrode under the action of a catalyst, producing oxygen. The metal-air battery of this invention operates at a voltage between 0.01 and 3 V, and at a speed of 10 mA / cm². 2 It can cycle stably for 100 hours at a current density. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of MOOH / Fe-CNTs-rGO prepared in Example 1.

[0021] Figure 2 This is a SEM image of the MOOH / Fe-CNTs-rGO prepared in Example 1;

[0022] Figure 3 Raman spectroscopy for MOOH / Fe-CNTs-rGO prepared in Example 1;

[0023] Figure 4 The CV curve of the catalytic electrode prepared in Example 2 is shown.

[0024] Figure 5 The optimal oxygen evolution reaction performance of the catalytic electrode prepared in Example 2 and a comparison diagram are shown.

[0025] Figure 6 The optimal oxygen reduction reaction performance of the catalytic electrode prepared in Example 2 and a comparison diagram are shown.

[0026] Figure 7 The LSV curve of the annular disk catalytic electrode prepared in Example 2 is shown.

[0027] Figure 8 The zinc-air battery assembled in Example 3 at 10 mA / cm 2 Performance graph for the next cycle. Detailed Implementation

[0028] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention. Example

[0029] This embodiment describes a carbon nanotube network-loaded hydroxyl oxide. The microstructure of the carbon nanotube network-loaded hydroxyl oxide consists of carbon nanotubes encapsulating irregularly shaped clusters of hydroxyl oxide. The size of the hydroxyl oxide is 0.5~2μm, and the diameter of a single carbon nanotube is 10~50 nm. Example

[0030] This embodiment provides a detailed description of the preparation method of carbon nanotube network-supported hydroxyl oxides in Example 1:

[0031] 10 mg of graphene oxide was poured into 10 mL of deionized water and 5 mL of hydrogen peroxide was added dropwise. The mixture was left to stand for 30 minutes to form solution I. 9 g of melamine and 0.1 g of ferric nitrate nonahydrate were dissolved in 100 mL of deionized water to form solution II. Solution I was poured into solution II and the mixture was vigorously stirred in a 100°C hydrothermal flask until a solid powder was formed. The resulting solid powder was heated to 400°C at a heating rate of 5°C per minute under an argon atmosphere and held for 1 hour. Then, it was heated to 900°C and annealed for 2 hours to obtain a sample named Fe-CNTs-rGO.

[0032] The above 50 mg Fe-CNTs-rGO was mixed with 10 mL of deionized water and sonicated for 1 hour to form solution A. 109 mg of nickel nitrate and 50 mg of ferric nitrate were dissolved in 5 mL of deionized water to form solution B. 30 mg of NaOH and 28 mg of Na2CO3 were dissolved in 5 mL of deionized water to form solution C. Solutions B and C were simultaneously and slowly added dropwise to solution A to form solution D. The pH of solution D was 10. After stirring at room temperature for 24 hours, the mixture was centrifuged three times with ethanol and dried under vacuum at 60°C for 12 hours to synthesize the final product MOOH / Fe-CNTs-rGO, which was a black powder.

[0033] The obtained product was tested. Figure 1 XRD pattern of MOOH / Fe-CNTs-rGO; Figure 2The SEM image of MOOH / Fe-CNTs-rGO shows that the microstructure consists of irregularly shaped clusters of nickel-iron hydroxyl oxides coated with carbon nanotubes, with a size of 0.5~2μm and a diameter of 10~50 nm for each individual carbon nanotube. Figure 3 The Raman plot of MOOH / Fe-CNTs-rGO shows that the ratio of D band to G band is 0.95.

[0034] Comparative Example 1

[0035] This embodiment provides a detailed description of the preparation method and test results of the carbon nanotube network:

[0036] 10 mg of graphene oxide was poured into 10 mL of deionized water and 5 mL of hydrogen peroxide was added dropwise. The mixture was left to stand for 30 minutes to form solution I. 9 g of melamine and 0.1 g of ferric nitrate nonahydrate were dissolved in 100 mL of deionized water to form solution II. Solution I was poured into solution II and the mixture was vigorously stirred in a 100°C hydrothermal flask until a solid powder was formed. The resulting solid powder was heated to 400°C at a heating rate of 5°C per minute under an argon atmosphere and held for 1 hour. Then, it was heated to 900°C and annealed for 2 hours to obtain a sample named Fe-CNTs-rGO.

[0037] Comparative Example 2

[0038] This embodiment provides a detailed description of the preparation method and test results of hydroxyl oxides:

[0039] 109 mg of nickel nitrate and 50 mg of ferric nitrate were dissolved in 5 mL of deionized water to form solution B. 30 mg of NaOH and 28 mg of Na2CO3 were dissolved in 5 mL of deionized water to form solution C. Solutions B and C were then slowly added dropwise to 10 mL of deionized water to form solution E, which had a pH of 10. After stirring at room temperature for 24 hours, the solution was centrifuged three times with ethanol and dried under vacuum at 60°C for 12 hours to synthesize the final product MOOH, which was a yellow powder. Example

[0040] In this embodiment, the products of Example 1, Comparative Example 1, and Comparative Example 2 are used as catalysts, and the specific steps are as follows:

[0041] 5 mg of the product was dispersed in 0.5 mL of deionized water and 0.5 mL of ethanol solution, and 20 μL of 5% Nafion solution was added dropwise and ultrasonically dispersed for 1 hour to obtain the catalytic ink. Then, 20 μL of the catalytic ink was added dropwise to a glassy carbon electrode and allowed to dry naturally to obtain the working electrode for testing. First, oxygen was continuously bubbled into the electrolyte for 30 minutes to form an oxygen-saturated solution, and then the electrode was tested at 50 mV·s. -1 CV activation was performed for 30 cycles at a scan rate, such as... Figure 4 As shown, the catalytic material can undergo a reduction reaction.

[0042] The LSV curve of the product in Example 1 was recorded at a speed of 1600 rpm and a scan rate of 10 mV·s. -1 Electrochemical compensation of 95%, such as Figure 5 As shown, the catalytic material exhibits excellent OER performance, E j=10 =1.523V, superior to commercially available precious metal RuO2 materials; such as Figure 6 As shown, the material exhibits excellent ORR performance, with a half-wave potential E 1 / 2 =0.821V.

[0043] The LSV curve of the product of Comparative Example 1 was recorded at a speed of 1600 rpm and a scan rate of 10 mV·s. -1 Electrochemical compensation of 95%, such as Figure 5 As shown, the catalytic material exhibits poor OER performance, E j=10 =1.72V, such as Figure 6 As shown, the half-wave potential E of this material 1 / 2 =0.81V, through ΔE=E j=10 -E 1 / 2 The material's bifunctional properties were evaluated, and its ΔE = 0.91V.

[0044] The LSV curve of the product of Comparative Example 1 was recorded at a speed of 1600 rpm and a scan rate of 10 mV·s. -1 Electrochemical compensation of 95%, such as Figure 6 As shown, the catalytic material exhibits poor ORR performance, E 1 / 2 =0.59V, such as Figure 5 As shown, the E of this material j=10 =1.51V, through ΔE=E j=10 -E 1 / 2 The material's bifunctional properties were evaluated, with a ΔE value of 0.92V.

[0045] Through ΔE=E j=10 -E 1 / 2 The material's bifunctional performance was evaluated, and its ΔE = 0.71V was superior to that of comparative examples 1 and 2.

[0046] like Figure 7 As shown, the scan rate is 10 mV·s -1 With 95% electrochemical compensation, the number of electrons transferred was calculated by testing with a ring-disk electrode, and the obtained number of electrons transferred, n=3.75, indicating that the reaction is a four-electron reaction. Example

[0047] This embodiment uses the carbon nanotube network-supported hydroxyl oxide from Example 1 as a catalyst for the positive electrode of a zinc-air battery, specifically including the following steps:

[0048] 5 mg of MOOH / Fe-CNTs-rGO was dispersed in 0.25 mL of deionized water and 0.25 mL of ethanol solution, and 20 μL of 5% Nafion solution was added dropwise. The mixture was then ultrasonically dispersed for 1 hour to obtain the catalytic ink. The catalytic ink was uniformly dropped onto 3 cm × 3 cm carbon paper and dried on a 60°C drying table. The active material loading was approximately 0.5 mg / cm³. 2 .

[0049] A 100 mL mixed solution of 6M KOH and 0.2M ZnCl2 was prepared as the electrolyte. A 3 mm thick zinc sheet (greater than 2 mm) was used as the negative electrode, and its surface was polished to remove zinc oxide. A zinc-air battery was assembled using a zinc-air battery mold, and a current density of 10 mA / cm² was tested on a Shanghai Chenhua Chi760 electrochemical workstation. 2 Cyclic performance testing, such as Figure 8 As shown.

[0050] The zinc-air battery prepared by using the nitrogen-doped carbon material of the present invention to coat nickel iron hydroxyl oxide as the positive electrode catalyst material of the zinc-air battery exhibits excellent electrochemical performance, good cycle stability, safety, reliability and no pollution. It is expected to replace precious metal catalysts and become an ideal catalyst material for the commercialization of next-generation zinc-air batteries.

[0051] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. For those skilled in the art, after learning the contents described in the present invention, several equivalent changes and substitutions can be made without departing from the principle of the present invention. These equivalent changes and substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A method for preparing carbon nanotube network-supported hydroxyl oxides, characterized in that: The microstructure of the carbon nanotube network supporting hydroxy oxides is that the carbon nanotubes are coated with irregularly shaped hydroxy oxides; wherein the size of the hydroxy oxides is 0.5~2μm, and the diameter of a single carbon nanotube is 10~50 nm. The preparation method includes the following steps: Step S1. Dissolve hydrogen peroxide-treated graphene oxide, ferric nitrate nonahydrate and melamine in deionized water, evaporate the liquid by high-temperature stirring to form a solid powder, and then carbonize the obtained powder in an argon atmosphere to obtain Fe-CNTs-rGO. The mass ratio of graphene oxide, ferric nitrate nonahydrate, and melamine is 1~5:10~20:900~1500; the evaporation temperature is 50~100℃. Step S2. Under alkaline conditions, a transition metal salt coordinates to generate a hydroxy oxide, which is then loaded onto the above Fe-CNTs-rGO to obtain MOOH / Fe-CNTs-rGO; Step S2 specifically includes the following steps: Fe-CNTs-rGO was dispersed in deionized water and sonicated for 1-5 hours to form solution A. Then, nickel nitrate and ferric nitrate in a mass ratio of 2~4:1~4 are dissolved in deionized water to form solution B; Sodium carbonate and sodium hydroxide in a mass ratio of 1~3:1~5 are dissolved in deionized water to form solution C; The above solutions B and C are simultaneously and slowly added dropwise to solution A while it is being stirred to form solution D; solution D is alkaline with a pH of 8-13.

2. The method for preparing carbon nanotube network-supported hydroxyl oxides according to claim 1, characterized in that, The carbonization process is as follows: first, maintain the temperature at 400~500℃ for 1~5 hours in an argon atmosphere, and then maintain the temperature at 700~1100℃ for 1~5 hours, with a heating rate of 1~20℃ / minute.

3. The method for preparing carbon nanotube network-supported hydroxyl oxides according to claim 1, characterized in that: The stirring environment of liquid D is at room temperature. After stirring for 12 to 48 hours, it is centrifuged 3 to 5 times. The liquid used for centrifugation is ethanol. After centrifugation, it is vacuum dried at 60 to 80°C for 2 to 24 hours to obtain carbon nanotube network-supported hydroxyl oxides.

4. The application of the carbon nanotube network-supported hydroxy oxide prepared by the method described in claim 1 as a catalyst for the air electrode of a metal-air battery.

5. The application according to claim 4, characterized in that: The catalyst layer was coated on the positive electrode carbon paper / carbon cloth of the metal-air battery, and the catalyst loading was 0.5 mg / cm³. 2 .

6. The application according to claim 4, characterized in that: The metal in a metal-air battery is aluminum, lithium, magnesium, iron, or zinc.

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