Three-dimensional bimetallic carbon material and preparation method and application thereof

Abstract

The invention relates to the technical field of nano material preparation and application, in particular to a three-dimensional bimetallic carbon material and a preparation method and application thereof.The preparation method includes the steps that firstly, metal cobalt salt, ferric salt, dicyandiamide and boric acid are ground to obtain a uniform mixture, the mixture is placed in a tubular furnace to be heated, and a precursor is obtained; the preparation method comprises the following steps: firstly, preparing a three-dimensional bimetallic carbon material precursor, secondly, generating bimetallic alloy from metal ions in the precursor through a carbon thermal reduction process, and finally, preparing the three-dimensional bimetallic carbon material under the catalytic action of the bimetallic alloy. Iron is introduced to form a bimetallic ferrocobalt alloy to effectively regulate and control the electronic structure of the material, so that the electro-catalytic reaction energy barrier is reduced, and the intrinsic activity is improved; the prepared three-dimensional bimetallic carbon material has good oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc air battery performance. The material has the advantages of simple and controllable preparation process, easiness in batch synthesis, low raw material price and the like, and can be used as an electrocatalytic reaction catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of nano material preparation and application, and in particular to a three-dimensional bimetallic carbon material and a preparation method and application thereof. Background Art

[0002] At present, in order to solve the energy shortage and environmental pollution problems caused by the serious consumption of traditional fossil fuels, researchers have developed many clean and efficient energy storage and conversion devices such as fuel cells and metal-air batteries. Among these devices, rechargeable zinc-air batteries have received widespread attention due to their low cost and high theoretical energy density. Generally, the multi-electron transfer process of the oxygen evolution reaction and oxygen reduction reaction occurring on its air electrode reduces the catalytic reaction kinetics and the performance of the zinc-air battery. At present, the precious metals RuO2 and Pt / C are good oxygen evolution reaction and oxygen reduction reaction catalysts; however, their high price, low reserves and poor durability limit their industrial application. In addition, these catalysts usually have monofunctional catalytic activity, resulting in the catalysts used in the air electrode having disadvantages such as high cost and side reactions. Therefore, the development of cheap, high-performance bifunctional oxygen evolution reaction and oxygen reduction reaction catalysts is the key to achieving high-performance zinc-air batteries.

[0003] In the past few decades, researchers have been committed to developing alternative oxygen evolution reaction and oxygen reduction reaction catalysts, such as transition metal-based compounds and carbon materials. In general, cobalt-based carbon materials have attracted much attention due to their low price, good conductivity and high oxygen evolution reaction activity. Although great research progress has been made, their oxygen reduction reaction performance cannot meet practical requirements due to their weak oxygen adsorption and activation capabilities. In order to improve the catalytic activity, the introduction of other metals can regulate the adsorption and desorption characteristics of reaction intermediates on the catalyst surface and reduce the catalytic reaction energy barrier. At the same time, the rational design of the structure of carbon materials is very important for catalysts. At present, common carbon materials include one-dimensional carbon nanotubes, two-dimensional graphene / carbon nanosheets and three-dimensional carbon materials. One-dimensional carbon nanotubes and three-dimensional carbon materials with hollow structures can accelerate material transfer and electron transfer during the catalytic reaction; assembling one-dimensional carbon nanotubes into three-dimensional carbon materials not only has a large specific surface area, but also has the advantages of one-dimensional materials. Recently, the chemical foaming method has attracted widespread attention from researchers due to its advantages such as simple operation and time saving. This process uses the gas generated by the foaming agent as a template to form a carbon material with a three-dimensional porous structure. Therefore, it is urgent to prepare three-dimensional carbon materials constructed from one-dimensional cobalt-based carbon nanotubes using a chemical foaming method to improve the catalytic performance of oxygen evolution reaction and oxygen reduction reaction.

[0004] In view of the above problems, the present invention uses a simple chemical foaming method and a subsequent calcination process to obtain a low-cost, high-catalytically active three-dimensional bimetallic carbon material. Thanks to the synergistic effect of the bimetallic cobalt-iron alloy formed by the introduction of iron and the three-dimensional highly conductive carbon material carrier, the bimetallic carbon material has good oxygen evolution reaction and oxygen reduction reaction performance in alkaline electrolyte. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and propose a three-dimensional bimetallic carbon material and its preparation method and application. The raw materials of the carbon material are low in price and abundant in reserves, and have good electrocatalytic oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery performance.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A three-dimensional bimetallic carbon material comprises carbon nanotubes embedded with cobalt-iron alloy and a bulk carbon material with a three-dimensional structure constructed by the carbon nanotubes.

[0008] Preferably, the mass ratio of metal cobalt to iron in the three-dimensional bimetallic carbon material is 1:0.05 to 1:1.

[0009] A method for preparing a three-dimensional bimetallic carbon material comprises the following steps:

[0010] Step 1: Grind 10 parts of metal cobalt salt, 0.5-10 parts of metal iron salt, 30-80 parts of dicyandiamide and 2-20 parts of boric acid in a mortar according to the mass ratio to obtain a uniform mixture;

[0011] Step 2: placing the above mixture in a tube furnace, heating the tube furnace to a target temperature at a constant heating rate under the protection of an inert gas argon or nitrogen, and keeping the temperature for a period of time to prepare a three-dimensional bimetallic carbon material precursor;

[0012] Step 3: Continue to heat the above three-dimensional bimetallic carbon material precursor in a tubular furnace at a constant heating rate to the target temperature and keep it warm for a period of time to prepare a three-dimensional bimetallic carbon material. During this process, the metal ions are carbon-thermally reduced to a metal cobalt-iron alloy.

[0013] Preferably, in step 1, the metal cobalt salt is cobalt chloride or cobalt nitrate, and the metal iron salt is ferric chloride or ferric nitrate.

[0014] Preferably, in step 2, the heating rate of the tubular furnace is 2 to 10° C. / min, the target temperature is 400 to 600° C., and the holding time is 0 to 6 hours.

[0015] Preferably, in step 3, the heating rate of the tubular furnace is 2-10° C. / min, the target temperature is 700-1200° C., and the holding time is 0.5-5 hours.

[0016] The present invention also provides an application of the three-dimensional bimetallic carbon material in electrocatalytic oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery.

[0017] Preferably, the three-dimensional bimetallic carbon material is used as a catalyst for electrocatalytic reactions and an air electrode material for rechargeable zinc-air batteries.

[0018] By adopting the above technical scheme: using metal cobalt salt and iron salt to synthesize bimetallic cobalt-iron alloy, dicyandiamide and boric acid as carbon / nitrogen source and boron source respectively, the preparation of three-dimensional bimetallic carbon material assembled by bimetallic cobalt-iron alloy embedded in carbon nanotubes is realized; by introducing iron to form bimetallic cobalt-iron alloy, the electronic structure of the material is effectively regulated, the energy barrier of electrocatalytic reaction is reduced and the intrinsic activity is improved; the prepared three-dimensional bimetallic carbon material has good performance in oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention utilizes a foaming method to prepare a three-dimensional bimetallic carbon material, and utilizes the gas generated by dicyandiamide and boric acid during the heating process as a template and polymer cross-linking to prepare a three-dimensional bimetallic carbon material precursor. In the subsequent heating process, the metal ions are carbon-thermally reduced to metal nanoparticles, and the metal nanoparticles serve as catalysts to catalyze the growth of carbon nanotubes, thereby solving the problem of easy agglomeration of carbon materials during the preparation process.

[0021] 2. The three-dimensional bimetallic carbon material prepared by the present invention utilizes iron to introduce to form a bimetallic cobalt-iron alloy, and the three-dimensional highly conductive carbon material carrier regulates the electronic structure of the material and the number of exposed rich catalytic active sites, thereby improving the intrinsic catalytic activity, catalytic reaction performance and mass transfer rate of the material during the catalytic reaction.

[0022] 3. The three-dimensional bimetallic carbon material prepared by the present invention has good electrocatalytic oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery performance in alkaline electrolyte, which solves the problems of low electrocatalytic reaction performance and low power density of zinc-air batteries.

[0023] 4. The preparation method of the present invention has the advantages of being simple and controllable, having low-cost raw materials, and being easy to prepare in batches. It can replace precious metal-based materials and promote applications in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is an X-ray diffraction spectrum of the three-dimensional bimetallic carbon material prepared in Example 1 of the present invention;

[0025] Figure 2 is a photograph of the three-dimensional bimetallic carbon material prepared in Example 1 of the present invention; wherein a is an optical photograph of the material, b and c are scanning electron microscope photographs of the material, and d are transmission electron microscope photographs of the material;

[0026] Figure 3 : is a performance diagram of the oxygen evolution reaction of the three-dimensional bimetallic carbon material prepared in Example 1 of the present invention in a potassium hydroxide solution; wherein a is a polarization curve diagram of the oxygen evolution reaction of the material, and b is a Tafel slope diagram of the oxygen evolution reaction of the material;

[0027] Figure 4 Graph showing the oxygen reduction reaction performance of the three-dimensional bimetallic carbon material prepared in Example 1 of the present invention; wherein a is a polarization curve graph of the oxygen reduction reaction of the material, and b is a Tafel slope graph of the oxygen reduction reaction of the material;

[0028] Figure 5 This is a performance test diagram of a zinc-air battery when the product prepared in Example 1 of the present invention is used as an air electrode material of a rechargeable zinc-air battery; wherein a is a polarization curve diagram of the zinc-air battery, and b is a stability curve diagram of the zinc-air battery. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0030] Embodiment 1:

[0031] A method for preparing a three-dimensional bimetallic carbon material comprises the following steps:

[0032] Step 1: Place 0.2 g of cobalt chloride, 0.02 g of ferric chloride, 1 g of dicyandiamide and 0.1 g of boric acid in a mortar, grind thoroughly and transfer to a crucible;

[0033] Step 2: placing the crucible in a tubular furnace, heating the tubular furnace to 500°C at a heating rate of 5°C / min in a nitrogen atmosphere, and keeping the temperature for 0.5h to obtain a three-dimensional bimetallic carbon material precursor;

[0034] Step 3: The three-dimensional bimetallic carbon material precursor is heated to 800°C in a tubular furnace at a heating rate of 5°C / min and kept warm for 2 hours to obtain a three-dimensional bimetallic carbon material.

[0035] The three-dimensional bimetallic carbon material prepared above was tested for its electrocatalytic oxygen evolution reaction and oxygen reduction reaction performance in a three-electrode electrolytic cell, and the electrolytes used were 1 mol / L and 0.1 mol / L potassium hydroxide solutions, respectively; the catalyst material used for the working electrode in the electrolytic cell was the product of the present invention, and the counter electrode and the reference electrode were carbon rods and saturated calomel electrodes, respectively. The electrochemical performance of the product of the present invention was tested using an electrochemical workstation, and the electrode potentials in the electrochemical test results were all converted to reversible hydrogen electrode potentials (RHE). In addition, the three-dimensional bimetallic carbon material was used as an air electrode catalyst for a rechargeable zinc-air battery to test the performance of the zinc-air battery.

[0036] The phase, morphology, structure and electrocatalytic performance of the three-dimensional bimetallic carbon material prepared above were studied. Figure 1 As shown, this is the X-ray diffraction spectrum of the three-dimensional bimetallic carbon material. Figure 1 It shows that the three-dimensional bimetallic carbon material product was successfully prepared.

[0037] like Figure 2 As shown, the optical, scanning electron microscope and transmission electron microscope images of the three-dimensional bimetallic carbon material are shown. Figure 2 It shows that the prepared three-dimensional bimetallic carbon material has a macroscopic three-dimensional bulk structure, which is composed of carbon nanotubes embedded with bimetallic cobalt-iron alloy.

[0038] like Figure 3 As shown in Figure 1, a is the polarization curve of the electrocatalytic oxygen evolution reaction of the three-dimensional bimetallic carbon material, and b is the Tafel slope diagram of the oxygen evolution reaction of the material. The material has good oxygen evolution reaction performance in 1 mol / L potassium hydroxide solution, with an output of 10 mA cm -2 The overpotential required for the current density is 319 mV, and the Tafel slope is 196 mV dec. -1 .

[0039] like Figure 4 As shown, a is the polarization curve of the electrocatalytic oxygen reduction reaction of the three-dimensional bimetallic carbon material, and b is the Tafel slope of the oxygen reduction reaction of the material. The material has good oxygen reduction reaction performance in 0.1 mol / L potassium hydroxide solution, with the starting potential and half-wave potential being 1.01 V and 0.90 V respectively, and the Tafel slope being 52 mV dec -1 .

[0040] like Figure 5 As shown in Figure 1, a is a performance curve of a rechargeable zinc-air battery when the three-dimensional bimetallic carbon material is used as an air electrode catalyst, and b is a cycle stability test curve of the zinc-air battery. The zinc-air battery has excellent zinc-air battery performance and a power density of 209.4 mW cm -2 .

[0041] Embodiment 2:

[0042] The same as Example 1, except that cobalt chloride is replaced by cobalt nitrate, the performance of oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery remain basically unchanged.

[0043] Embodiment 3:

[0044] The same as Example 1, except that the mass of ferric chloride added was changed to 0.05 g, and the prepared three-dimensional bimetallic carbon material outputted 10 mA cm when used for oxygen evolution reaction. -2 The overpotential required for the current density is 334 mV, and the starting potential and half-wave potential for the oxygen reduction reaction are 1.00 V and 0.89 V, respectively.

[0045] Embodiment 4:

[0046] The same as Example 1, except that the calcination temperature in the third step of the preparation process was changed to 1000°C. The prepared three-dimensional bimetallic carbon material outputted 10 mA cm -2 The overpotential required for the current density is 342 mV, and the starting potential and half-wave potential for the oxygen reduction reaction are 0.98 V and 0.88 V, respectively.

[0047] Comparative Example 1:

[0048] The same as Example 1, except that no metal iron salt was added, to obtain a three-dimensional single metal carbon material Co-CNTs. Figure 3 and Figure 4 As shown, the material outputs 10 mA cm when used for oxygen evolution reaction. -2 The overpotential required for the current density is 386mV, the starting potential for oxygen reduction reaction is 0.98V, and the half-wave potential is 0.87V.

[0049] In summary, the carbon material raw materials of the present invention are low in price and abundant in reserves, and have good electrocatalytic oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery performance.

[0050] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A three-dimensional bimetallic carbon material, characterized in that: The three-dimensional bimetallic carbon material includes carbon nanotubes embedded with cobalt-iron alloy and a bulk carbon material with a three-dimensional structure constructed by the carbon nanotubes.

2. A three-dimensional bimetallic carbon material according to claim 1, characterized in that: The mass ratio of metal cobalt to iron in the three-dimensional bimetallic carbon material is 1:0.05 to 1:

1.

3. The method for preparing a three-dimensional bimetallic carbon material according to claim 1 or 2, characterized in that: The steps include: Step 1: Grind 10 parts of metal cobalt salt, 0.5-10 parts of metal iron salt, 30-80 parts of dicyandiamide and 2-20 parts of boric acid in a mortar according to the mass ratio to obtain a uniform mixture; Step 2: placing the above mixture in a tube furnace, heating the tube furnace to a target temperature at a constant heating rate under the protection of an inert gas argon or nitrogen, and keeping the temperature for a period of time to prepare a three-dimensional bimetallic carbon material precursor; Step 3: Continue to heat the above three-dimensional bimetallic carbon material precursor in a tubular furnace at a constant heating rate to the target temperature, and keep it warm for a period of time to prepare a three-dimensional bimetallic carbon material.

4. The method for preparing a three-dimensional bimetallic carbon material according to claim 3, characterized in that: In step 1, the metal cobalt salt is cobalt chloride or cobalt nitrate, and the metal iron salt is ferric chloride or ferric nitrate.

5. The method for preparing a three-dimensional bimetallic carbon material according to claim 3, characterized in that: In step 2, the heating rate of the tubular furnace is 2 to 10° C. / min, the target temperature is 400 to 600° C., and the holding time is 0 to 6 hours.

6. The method for preparing a three-dimensional bimetallic carbon material according to claim 3, characterized in that: In step 3, the heating rate of the tubular furnace is 2 to 10° C. / min, the target temperature is 700 to 1200° C., and the holding time is 0.5 to 5 hours.

7. Use of the three-dimensional bimetallic carbon material according to claim 1 or 2 in electrocatalytic oxygen evolution reaction, oxygen reduction reaction and rechargeable zinc-air battery.

8. The use according to claim 7, characterized in that: The three-dimensional bimetallic carbon material serves as a catalyst for electrocatalytic reactions and an air electrode material for rechargeable zinc-air batteries.

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