Nitrogen-doped carbon nanotube packaged CoCu bimetallic electrocatalyst as well as preparation method and application thereof

Abstract

The invention is applicable to the technical field of electrocatalysis, and provides a preparation method of a nitrogen-doped carbon nanotube (NCNT) packaged CoCu bimetallic electrocatalyst, which comprises the following steps: cleaning carbon cloth (CC); the preparation method comprises the following steps: dissolving Co (NO3) 2.6 H2O and CuCl2. 2H2O in deionized water, dissolving 2-methylimidazole in deionized water, mixing the two solutions, immersing a CC substrate in the mixed solution, and standing at room temperature; cleaning the obtained product, and drying the product to obtain CoCu-MOF / CC; and putting the CoCu-MOF / CC into a porcelain boat, putting the porcelain boat containing a melamine ethanol solution in front of the CoCu-MOF / CC, and heating and calcining to obtain the CoCu-coated NCNT / CC. The invention further provides the nitrogen-doped carbon nano tube packaged CoCu bimetallic electrocatalyst and application of the nitrogen-doped carbon nano tube packaged CoCu bimetallic electrocatalyst. According to the preparation method, MOF is selected as a template, CoCu-MOF grown on a CC substrate in situ is taken as a precursor, alloy particles are packaged in a carbon layer through a coating effect, so that agglomeration and corrosion of an alloy catalyst are effectively avoided, pyrolysis in-situ conversion is performed under the assistance of melamine, an electronic structure is adjusted, a reaction energy barrier is reduced, excellent activity and durability are realized, and OER catalytic activity is efficiently promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and in particular relates to a nitrogen-doped carbon nanotube encapsulated CoCu bimetallic electrocatalyst and a preparation method and application thereof. Background Art

[0002] Faced with the severe challenges of environmental pollution and energy depletion, renewable energy technology has become a research focus. Among many renewable energy technologies, water electrolysis has attracted much attention due to its cleanliness and high efficiency. In water electrolysis hydrogen production technology, electrocatalysts play a key role in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), improving the electrochemical reaction rate by enhancing reaction kinetics and reducing overpotential; however, the anode OER process in alkaline water electrolysis has become a bottleneck in technological development due to its complex four-electron transfer process. This process not only consumes a lot of energy, but also leads to excessively high reaction energy barriers, which seriously limits the efficiency of water electrolysis hydrogen production. Therefore, the development of OER electrocatalysts with high activity and durability is crucial to promote the development of water splitting technology. In the existing technology, although commercial OER electrocatalysts such as Ru / Ir oxides are highly active, their high cost, scarce resources and insufficient stability limit their widespread application in industry. There is an urgent need to seek electrocatalysts with higher performance and higher cost performance.

[0003] Alloy catalysts have attracted much attention and show significantly enhanced catalytic activity compared to single metals, which is attributed to the synergistic changes in electronic structure, low energy barriers and enhanced reaction kinetics. However, existing preparation methods are often complicated and energy-intensive; in addition, during the OER reaction, alloy particles are prone to agglomeration and corrosion, which seriously affects their catalytic activity. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a method for preparing a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst, aiming to solve the problems raised in the above background technology.

[0005] The embodiment of the present invention is implemented as follows: a method for preparing a nitrogen-doped carbon nanotube encapsulated CoCu bimetallic electrocatalyst comprises the following steps:

[0006] Step 1: Clean the carbon cloth (CC) as a substrate;

[0007] Step 2: Co(NO 3 ) 2 6H 2 O and CuCl 2 ·2H 2 O is dissolved in deionized water to form solution A, and 2-methylimidazole is dissolved in deionized water to form a uniform solution B;

[0008] Step 3: quickly pour solution A into solution B to obtain a mixed solution, immerse the cleaned CC substrate in the mixed solution, and let it stand at room temperature;

[0009] Step 4: Wash the product obtained in step 3 with deionized water for multiple times, and dry it to obtain purple CoCu-MOF / CC;

[0010] Step 5. Put CoCu-MOF / CC into a porcelain boat and place it in the middle of a tubular furnace. Put a porcelain boat containing melamine ethanol solution in front of it. Heat and calcine it in the tubular furnace and keep it warm in an atmosphere of high-purity argon. After calcination, the color changes from purple to black to obtain CoCu@NCNT / CC, which is a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst.

[0011] Preferably, in step 1, the cleaning process is specifically as follows: the carbon cloth (CC) is treated with HNO 3 , acetone, ethanol and water ultrasonic cleaning.

[0012] Preferably, in step 2, the Co(NO 3 ) 2 6H 2 O and CuCl 2 ·2H 2 O has a molar ratio of 1:1; the Co(NO 3 ) 2 6H 2 The molar ratio of O to 2-methylimidazole is 1:16.

[0013] Preferably, in step five, the concentration of the melamine ethanol solution is 5 g / 5 mL.

[0014] Preferably, in step five, the process of heating and calcining in the tubular furnace is specifically as follows: the tubular furnace is heated from room temperature to 850° C. at a heating rate of 2° C. / min; and the insulation time is 1 hour.

[0015] Another object of an embodiment of the present invention is to provide a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst, which is prepared by the above-mentioned preparation method.

[0016] Another object of an embodiment of the present invention is to provide an application of a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst in hydrogen production by water electrolysis.

[0017] The preparation method of the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst provided in the embodiment of the present invention successfully constructs a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic alloy electrocatalyst by selecting a metal organic framework (MOF) with the characteristics of high specific surface area, adjustable pore size, diversity of central metal and organic ligand, and easy modification as a template, and in situ growth of CoCu-MOF on a carbon cloth (CC) substrate is used as a precursor. One-dimensional nitrogen-doped carbon nanotubes (NCNT) have a large specific surface area, excellent charge transfer ability, short diffusion path and high structural stability. The alloy particles are encapsulated in the carbon layer through the coating effect to effectively avoid the agglomeration and corrosion of the alloy catalyst, and are pyrolyzed in situ with the assistance of melamine to be converted into a carbon nanotube-encapsulated metal alloy electrocatalyst (CoCu@NCNT / CC). The composite of NCNT and alloy catalyst can adjust the electronic structure, reduce the reaction energy barrier, achieve excellent activity and durability, and efficiently promote the OER catalytic activity; improve the electrocatalytic oxygen evolution performance, at 10 mA cm -2 The overpotential at this current density is 264 mV. Meanwhile, CoCu@NCNT / CC has a -2 The chronopotentiometry test under the given conditions was able to maintain a high stability for 110 h, providing a new in-situ pyrolysis doping path for constructing cost-effective catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of CoCu@NCNT / CC prepared in Example 1 of the present invention;

[0019] Figure 2 TEM image of CoCu@NCNT / CC prepared in Example 1 of the present invention;

[0020] Figure 3 This is the SEM image of Co@NCNT / CC prepared in Comparative Example 1 of the present invention;

[0021] Figure 4 XRD diagrams of CoCu@NCNT / CC prepared in Example 1 of the present invention and Co@NCNT / CC prepared in Comparative Example 1;

[0022] Figure 5 The OER polarization curve test diagram of CoCu@NCNT / CC prepared in Example 1 of the present invention and Co-NCNT / CC prepared in Comparative Example 1;

[0023] Figure 6 This is the electrochemical stability test result of CoCu@NCNT / CC prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0026] Example 1: A method for preparing a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst comprises the following steps:

[0027] Step 1: Use 3M HNO 3 , acetone, ethanol, and water ultrasonic cleaning for 10 min to remove dust and impurities on the CC surface;

[0028] Step 2: 1 mol Co(NO 3 ) 2 6H 2 O and 1 mol CuCl 2 ·2H 2 O was dissolved in 25 mL of deionized water to form solution A;

[0029] Step 3: Dissolve 16 mol of 2-methylimidazole in a beaker containing 25 mL of deionized water to form a uniform solution B;

[0030] Step 4: Pour solution A into solution B quickly, immerse the cleaned CC substrate in the mixed solution, and let it stand at room temperature for 4 hours;

[0031] Step 5: Wash the product obtained in step 4 with deionized water several times, and then dry the product in a vacuum drying oven at 60° C. for 8 h to obtain a purple CoCu-MOF / CC;

[0032] Step 6: Place CoCu-MOF / CC into a porcelain boat, and place the porcelain boat containing CoCu-MOF / CC into the middle of the tubular furnace, and place a porcelain boat containing 5g / 5mL melamine ethanol solution in front. Then heat the tubular furnace from room temperature to 850°C at a heating rate of 2°C / min, and keep it for 1h in an atmosphere of high-purity argon (gas concentration>99.999%). After calcination, the color of the product changes from purple to black, and the CoCu@NCNT / CC sample is obtained.

[0033] Comparative Example 1: A nitrogen-doped carbon nanotube encapsulated Co metal electrocatalyst, wherein the preparation method comprises the following steps:

[0034] Step 1: Use 3M HNO 3 , acetone, ethanol, and water ultrasonic cleaning for 10 min to remove dust and impurities on the CC surface;

[0035] Step 2: 2 mol Co(NO 3 ) 2 6H 2 O was dissolved in 25 mL of deionized water to form solution A;

[0036] Step 3: Dissolve 16 mol of 2-methylimidazole in a beaker containing 25 mL of deionized water to form a uniform solution B;

[0037] Step 4: Pour solution A into solution B quickly, immerse the cleaned CC substrate in the mixed solution, and let it stand at room temperature for 4 hours;

[0038] Step 5: Wash the product obtained in step 4 with deionized water for multiple times, and then place the product in a vacuum drying oven at 60° C. and dry for 8 h to obtain Co-MOF / CC;

[0039] Step 6: Place Co-MOF / CC into a porcelain boat, and place the porcelain boat containing Co-MOF / CC into the middle of the tubular furnace, and place a porcelain boat containing 5g / 5mL melamine ethanol solution in front. Then heat the tubular furnace from room temperature to 850°C at a heating rate of 2°C / min, and keep it in an atmosphere of high-purity argon (gas concentration>99.999%) for 1h. After calcination, the Co@NCNT / CC sample is obtained.

[0040] Performance Testing:

[0041] The CoCu@NCNT / CC prepared in Example 1 was observed using a scanning electron microscope, and the SEM image was as follows: Figure 1 As shown, the CoCu@NCNT / CC prepared in Example 1 was observed using a transmission electron microscope, and the TEM image was as shown in FIG. Figure 2 As shown;

[0042] The Co@NCNT / CC prepared in Comparative Example 1 was observed using a scanning electron microscope, and the SEM image was as follows: Figure 3 As shown;

[0043] The CoCu@NCNT / CC prepared in Example 1 and the Co@NCNT / CC prepared in Comparative Example 1 were analyzed by X-ray diffractometer, and the XRD patterns were as follows: Figure 4 As shown;

[0044] Oxygen evolution reaction performance test;

[0045] The samples prepared in Example 1 and Comparative Example 1 were respectively subjected to oxygen evolution reaction performance tests in 1 M KOH alkaline solution using a three-electrode system (catalyst as working electrode, mercury / mercuric oxide electrode as reference electrode, and carbon rod as counter electrode). Linear sweep voltammetry (LSV) was used at 1 mV s -1 The electrocatalyst activity of the polarization curve was tested at a scan rate of , and the mercury / mercury oxide electrode potential was converted into a reversible hydrogen electrode potential according to the Nernst equation, as follows: E RHE =E(Hg / HgO)+0.098+0.059×pH(1M KOH, pH~13.7);

[0046] Where E RHE is the conversion potential relative to RHE, E SCE is the experimental potential value measured for SCE. The test results are as follows: Figure 5 As shown, according to Figure 5 It can be seen that at a current density of 10 mA cm -2 Under the condition of 100 % CO, the overpotentials of CoCu@NCNT / CC and Co@NCNT / CC are 264 mV and 328 mV, respectively, which proves that the performance of the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic alloy electrocatalyst CoCu@NCNT / CC prepared in the embodiment of the present invention in oxygen evolution reaction (OER) is significantly improved compared with the nitrogen-doped carbon nanotube-encapsulated Co metal electrocatalyst Co@NCNT / CC.

[0047] Stability testing;

[0048] The sample prepared in Example 1 was subjected to a chronopotentiometry stability test in a 1M KOH alkaline solution using a three-electrode system (catalyst as working electrode, mercury / mercuric oxide electrode as reference electrode, carbon rod as counter electrode). The test results are as follows: Figure 6 As shown, according to Figure 6 It can be seen that the sample is -2 It remains stable for 110h under a current density of , which has application value.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst, characterized in that: The following steps are involved: Step 1: Clean the carbon cloth as a substrate; Step 2: Dissolve Co(NO3)2·6H2O and CuCl2·2H2O in deionized water to form solution A, and dissolve 2-methylimidazole in deionized water to form a uniform solution B; Step 3: quickly pour solution A into solution B to obtain a mixed solution, immerse the cleaned CC substrate in the mixed solution, and let it stand at room temperature; Step 4: Wash the product obtained in step 3 with deionized water for multiple times, and dry it to obtain purple CoCu-MOF / CC; Step 5. Put CoCu-MOF / CC into a porcelain boat and place it in the middle of a tubular furnace. Put a porcelain boat containing melamine ethanol solution in front of it. Heat and calcine it in the tubular furnace and keep it warm in an atmosphere of high-purity argon. After calcination, the color changes from purple to black to obtain CoCu@NCNT / CC, which is a nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst.

2. The method for preparing the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst according to claim 1, characterized in that: In step 1, the cleaning process is specifically as follows: ultrasonically cleaning the carbon cloth (CC) with HNO3, acetone, ethanol and water respectively.

3. The method for preparing the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst according to claim 1, characterized in that: In step 2, the molar ratio of Co(NO3)2·6H2O to CuCl2·2H2O is 1:1; the molar ratio of Co(NO3)2·6H2O to 2-methylimidazole is 1:

16.

4. The method for preparing the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst according to claim 1, characterized in that: In step 5, the concentration of the melamine ethanol solution is 5g / 5mL.

5. The method for preparing the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst according to claim 1, characterized in that: In step 5, the process of heating and calcining in the tubular furnace is specifically as follows: the tubular furnace is heated from room temperature to 850° C. at a heating rate of 2° C. / min; and the insulation time is 1 hour.

6. A nitrogen-doped carbon nanotube encapsulated CoCu bimetallic electrocatalyst, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the nitrogen-doped carbon nanotube-encapsulated CoCu bimetallic electrocatalyst as claimed in claim 6 in hydrogen production by electrolysis of water.

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