CN109382125B - Nickel-nitrogen co-doped carbon-based electrocatalyst and preparation method and application thereof - Google Patents

Abstract

The invention provides a preparation method of a nickel-nitrogen co-doped carbon-based electrocatalyst, which comprises the following steps: A) dispersing nickel salt, dicyandiamide and ammonium chloride in water, drying and calcining; B) mixing the calcined product with glucose in water and then carrying out hydrothermal reaction; C) and calcining the product of the hydrothermal reaction to obtain the nickel-nitrogen co-doped carbon-based electrocatalyst. The invention utilizes the limited-area reaction to disperse the nickel in the form of single atom in the nitrogen-doped carbon-based material, thereby avoiding the agglomeration and the loss of active sites. The prepared catalyst shows excellent electrocatalytic carbon dioxide reduction performance, and the selectivity of the catalyst on carbon monoxide can reach 99%. The preparation method provided by the invention has the characteristics of simple process flow, low cost, large yield, suitability for industrial production and the like, and has potential application value. The invention also provides a nickel-nitrogen co-doped carbon-based electrocatalyst and application thereof.

Description

A kind of nickel-nitrogen co-doped carbon-based electrocatalyst, its preparation method and application

technical field

The invention belongs to the technical field of catalysis, and in particular relates to a nickel-nitrogen co-doped carbon-based electrocatalyst, a preparation method and application thereof.

Background technique

Energy is the basis for the survival and development of human society. At present, the energy needed by human beings is heavily dependent on petroleum energy. Excessive consumption of petroleum energy not only aggravates the energy crisis, but also leads to excessive emissions of carbon dioxide, which brings about an increasingly serious greenhouse effect, which seriously threatens the survival and development of human beings. The conversion and utilization of carbon dioxide can not only effectively reduce the accumulation of carbon dioxide in the atmosphere, but also convert carbon dioxide into carbon-containing chemicals, thereby promoting the carbon cycle.

The reduction of carbon dioxide by electrocatalysis is one of the most promising ways to realize the conversion and utilization of carbon dioxide. Although many progresses have been made on the electrocatalytic reduction of CO2, the diversity of reduction products leads to low CO2 reduction selectivity, especially the reduction of water to hydrogen becomes the main competing reaction in the catalytic reduction of CO2, resulting in low CO2 conversion. Noble metals such as Au and Ag show excellent selectivity when applied to CO2 reduction, but their expensive prices still limit their further development as electrocatalysts for CO2 reduction. Therefore, finding cheap and efficient electrocatalysts for CO2 reduction has become an urgent problem.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a nickel-nitrogen co-doped carbon-based electrocatalyst, a preparation method and application thereof, and the nickel-nitrogen co-doped carbon-based electrocatalyst in the present invention has high reaction selectivity and low cost.

The present invention provides a method for preparing a nickel-nitrogen co-doped carbon-based electrocatalyst, comprising the following steps:

A) disperse nickel salt, dicyandiamide and ammonium chloride in water, and calcine after drying;

B) the product after calcination is mixed with glucose in water to carry out hydrothermal reaction;

C) calcining the product of the hydrothermal reaction to obtain a nickel-nitrogen co-doped carbon-based electrocatalyst.

Preferably, the nickel salt is a divalent soluble nickel salt.

Preferably, the mass ratio of the nickel salt to the dicyandiamide is (0.2-5): 100;

The mass ratio of the nickel salt to the ammonium chloride is (0.2-5):500.

Preferably, the calcination temperature in the step A) is 500-650°C;

The calcination time in the step A) is 1 to 4 hours.

Preferably, the mass ratio of the calcined product in the step A) to the glucose is (0.7-1.5):5.

Preferably, the temperature of the hydrothermal reaction is 160-200°C;

The time of the hydrothermal reaction is 10-20 hours.

Preferably, the calcination temperature in the step C) is 800-1100°C;

The calcination time in the step C) is 0.5 to 4 hours.

The present invention provides a nickel-nitrogen co-doped carbon-based electrocatalyst, which is prepared according to the above preparation method.

Preferably, the mass fraction of nitrogen in the nickel-nitrogen co-doped carbon-based electrocatalyst is 3-6%;

The mass fraction of nickel in the nickel-nitrogen co-doped carbon-based electrocatalyst is 1-3%.

Application of Ni-nitrogen Co-doped Carbon-Based Electrocatalysts in Carbon Dioxide Reduction Reaction

The present invention provides a method for preparing a nickel-nitrogen co-doped carbon-based electrocatalyst, comprising the following steps: A) dispersing nickel salt, dicyandiamide and ammonium chloride in water, drying and then calcining; B) calcining After mixing the product with glucose in water, a hydrothermal reaction is carried out; C) the product of the hydrothermal reaction is calcined to obtain a nickel-nitrogen co-doped carbon-based electrocatalyst. The invention utilizes the confinement reaction to disperse nickel in the form of single atoms in the nitrogen-doped carbon-based material, thereby avoiding the agglomeration and loss of active sites. The prepared catalyst exhibits excellent electrocatalytic carbon dioxide reduction performance, and the selectivity to carbon monoxide can reach 99%. The preparation method provided by the invention has the characteristics of simple process flow, low cost, large output, suitable for industrial production and the like, and has potential application value.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to the provided drawings without creative work.

Fig. 1 is the X-ray diffraction pattern of product in the embodiment of the present invention 1;

Fig. 2 is the TEM image of the product in the embodiment of the present invention 1;

Fig. 3 is the element distribution diagram of the product in the embodiment of the present invention 1;

Fig. 4 is the X-ray photoelectron spectroscopy analysis diagram of the product in the embodiment of the present invention 1;

Fig. 5 is the HAADF figure of the product in the embodiment of the present invention 1;

6 is a linear voltammetry scan diagram of the electrocatalyst in Example 1 of the present invention;

7 is a linear voltammetry scan diagram of the electrocatalyst in Example 2 of the present invention;

8 is a linear voltammetry scan diagram of the electrocatalyst in Example 3 of the present invention;

9 is a linear voltammetry scan diagram of the electrocatalyst in Example 4 of the present invention;

Figure 10 is a linear voltammetry scan diagram of the electrocatalyst in Example 5 of the present invention;

FIG. 11 is a linear voltammetry scan diagram of the electrocatalyst in Comparative Example 1 of the present invention;

Figure 12 is a linear voltammetry scan diagram of the electrocatalyst in Comparative Example 2 of the present invention;

13 is a Faradaic efficiency curve of the catalysts in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention for reducing carbon dioxide to carbon monoxide.

Detailed ways

The invention provides a preparation method of a nickel-nitrogen co-doped carbon-based electrocatalyst, comprising the following steps:

A) disperse nickel salt, dicyandiamide and ammonium chloride in water, and calcine after drying;

B) the product after calcination is mixed with glucose in water to carry out hydrothermal reaction;

C) calcining the product of the hydrothermal reaction to obtain a nickel-nitrogen co-doped carbon-based electrocatalyst.

The electrocatalyst prepared by the preparation method of the present invention has high reaction selectivity and low cost.

In the present invention, nickel salt, dicyandiamide and ammonium chloride are dispersed in water, the water is evaporated to dryness after stirring at 80 DEG C, and then calcined to obtain a calcined product. In the present invention, the nickel salt is preferably a divalent soluble nickel salt, more preferably nickel nitrate, nickel acetate, and nickel chloride; the mass ratio of the nickel salt to dicyandiamide is preferably (0.2-5):100 , more preferably (1-4):100; the mass ratio of the nickel salt to ammonium chloride is (0.2-5):500, more preferably (1-4):500. Specifically, in the embodiment of the present invention, it may be 1:100:500, 3.5:100:500 or 4.7:100:500. In the present invention, the temperature of the first calcination is preferably 500-650°C, more preferably 550-600°C; the time of the first calcination is preferably 1-4 hours, more preferably 2-3 hours. In the present invention, the temperature is preferably raised at a rate of 5-10°C/min, the temperature is raised to the calcination temperature and then calcined, and the temperature is naturally lowered after the calcination is completed.

The product after the first calcination and the glucose are mixed in water to carry out a hydrothermal reaction, and the mass ratio of the product after the first calcination to the glucose is preferably (0.7-1.5): 5, more preferably (1-1.2): 5 The temperature of the hydrothermal reaction is preferably 160-200°C, more preferably 180-190°C; the time of the hydrothermal reaction is preferably 10-20 hours, more preferably 12-18 hours. After the hydrothermal reaction is completed, it is allowed to cool naturally, and then the product of the hydrothermal reaction is washed with deionized water and ethanol in sequence, and then dried.

The product of the hydrothermal reaction is calcined, and the calcination is preferably carried out under an argon atmosphere. The calcination temperature is preferably 800-1100°C, more preferably 900-1000°C; the calcining time is preferably 0.5-4 hours, more preferably 1 to 3 hours. In the present invention, the temperature is preferably raised to the calcination temperature at a rate of 5-10° C./min, followed by calcination, and after calcination is completed, the temperature is lowered to room temperature at a rate of 5-10° C./min to obtain a nickel-nitrogen co-doped carbon-based electrocatalyst.

The present invention also provides a nickel-nitrogen co-doped carbon-based electrocatalyst, which is prepared according to the above preparation method. The mass fraction of nitrogen in the nickel-nitrogen co-doped carbon-based electrocatalyst in the present invention is preferably 3-6%, more preferably 4%, and the mass fraction of nickel is preferably 1-3%, more preferably 1.4%. There are two forms of N element in the catalyst: graphitic nitrogen and pyridine nitrogen, and Ni is connected with pyridine nitrogen. The outermost layer of the catalyst is wrapped with graphene produced by carbonization of glucose.

The present invention also provides the application of the above electrocatalyst in the catalytic reduction of carbon dioxide.

The present invention provides a method for preparing a nickel-nitrogen co-doped carbon-based electrocatalyst, comprising the following steps: A) dispersing nickel salt, dicyandiamide and ammonium chloride in water, drying and then calcining; B) calcining After mixing the product with glucose in water, a hydrothermal reaction is carried out; C) the product of the hydrothermal reaction is calcined to obtain a nickel-nitrogen co-doped carbon-based electrocatalyst. The invention utilizes the confinement reaction to disperse nickel in the form of single atoms in the nitrogen-doped carbon-based material, and at the same time introduces glucose as the protective layer, so as to avoid the agglomeration and loss of active sites during high-temperature calcination. The prepared catalyst exhibits excellent electrocatalytic carbon dioxide reduction performance, and the selectivity to carbon monoxide can reach 99%. The preparation method provided by the invention has the characteristics of simple process flow, low cost, large output, suitable for industrial production and the like, and has potential application value.

In order to further illustrate the present invention, a nickel-nitrogen co-doped carbon-based electrocatalyst provided by the present invention, its preparation method and application will be described in detail below with reference to the examples, but it should not be construed as a limitation on the protection scope of the present invention.

Example 1

Mix and disperse nickel chloride, dicyandiamide and ammonium chloride with water in a mass ratio of 3.5:100:500, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcined at 500°C for 1 hour at a heating rate of 5°C/min, and then lowered to room temperature at a cooling rate of 5°C/min;

The calcined sample and glucose were mixed with water at a mass ratio of 1:5, and then hydrothermally reacted at 180 ° C for 12 hours, and the obtained product was washed with deionized water and ethanol in turn, and then dried;

The hydrothermally treated sample was placed in a quartz tube, calcined at a heating rate of 5°C/min in an argon atmosphere at 1000°C for 0.5 hours, and then lowered to room temperature at a cooling rate of 5°C/min to obtain a nickel-nitrogen co-doped carbon matrix. Electrocatalyst.

The prepared samples were analyzed by XRD, and the results are shown in Figure 1. Fig. 1 is the X-ray diffraction pattern of the product in Example 1 of the present invention. It can be seen from Fig. 1 that the spectrum of Fig. 1 is consistent with the spectrum of graphene, and it can be determined that the carbon of the sample becomes graphene after high temperature treatment. Because of the small content of Ni, it does not crystallize in graphene, so the diffraction peak of Ni does not appear in the spectrum.

The prepared samples were analyzed by TEM, and the results are shown in Figures 2-3. FIG. 2 is a TEM image of the product in Example 1 of the present invention; FIG. 3 is an element distribution diagram of the product in Example 1 of the present invention. It can be seen from Fig. 2 that the prepared sample has a flake-like morphology, and the element distribution map of Fig. 3 shows that nickel and nitrogen are uniformly distributed on the carbon.

The prepared sample was subjected to X-ray photoelectron spectroscopy analysis, and the results are shown in Figure 4, which is an X-ray photoelectron spectroscopy analysis diagram of the product in Example 1 of the present invention. Figure a is the XPS spectrum of Ni2p, and Figure b is the XPS spectrum of N1s. It can be seen from Figure 4 that N and Ni were successfully incorporated into carbon.

The prepared samples were characterized by HAADF, and the results are shown in Figure 5, which is the HAADF diagram of the product in Example 1 of the present invention. It can be seen from Fig. 5 that Ni is dispersed on the carbon substrate as a single atom.

Example 2

Mix and disperse nickel chloride, dicyandiamide and ammonium chloride with water in a mass ratio of 1:100:500, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcine at 550°C for 2 hours at a heating rate of 5°C/min, and then drop to room temperature at a cooling rate of 5°C/min;

The calcined sample and glucose were mixed with water at a mass ratio of 1:5, and then hydrothermally reacted at 180 ° C for 12 hours, and the obtained product was washed with deionized water and ethanol in turn, and then dried;

The hydrothermally treated sample was placed in a quartz tube, calcined at a heating rate of 5°C/min in an argon atmosphere of 1000°C for 1 hour, and then lowered to room temperature at a cooling rate of 5°C/min to obtain a nickel-nitrogen co-doped carbon matrix. Electrocatalyst.

Example 3

Mix and disperse nickel chloride, dicyandiamide and ammonium chloride with water in a mass ratio of 4.7:100:500, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcined at 600°C for 3 hours at a heating rate of 5°C/min, and then lowered to room temperature at a cooling rate of 5°C/min;

The calcined sample and glucose were mixed with water at a mass ratio of 1:5, and then hydrothermally reacted at 160 ° C for 16 hours, and the obtained product was washed with deionized water and ethanol in turn, and then dried;

The hydrothermally treated sample was placed in a quartz tube, calcined at a heating rate of 5°C/min in an argon atmosphere of 1000°C for 3 hours, and then lowered to room temperature at a cooling rate of 5°C/min to obtain a nickel-nitrogen co-doped carbon matrix. Electrocatalyst.

Example 4

Mix and disperse nickel chloride, dicyandiamide and ammonium chloride with water in a mass ratio of 3.5:100:500, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcined at 500°C for 1 hour at a heating rate of 5°C/min, and then lowered to room temperature at a cooling rate of 5°C/min;

The calcined sample and glucose were mixed with water at a mass ratio of 1:5, and then hydrothermally reacted at 180 ° C for 12 hours, and the obtained product was washed with deionized water and ethanol in turn, and then dried;

The hydrothermally treated sample was placed in a quartz tube, calcined at a heating rate of 5°C/min in an argon atmosphere at 1100°C for 0.5 hours, and then lowered to room temperature at a cooling rate of 5°C/min to obtain a nickel-nitrogen co-doped carbon matrix. Electrocatalyst.

Example 5

Mix and disperse nickel chloride, dicyandiamide and ammonium chloride with water in a mass ratio of 3.5:100:500, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcined at 500°C for 1 hour at a heating rate of 5°C/min, and then lowered to room temperature at a cooling rate of 5°C/min;

The calcined sample and glucose were mixed with water at a mass ratio of 1:5, and then hydrothermally reacted at 180 ° C for 12 hours, and the obtained product was washed with deionized water and ethanol in turn, and then dried;

The hydrothermally treated sample was placed in a quartz tube, calcined at a heating rate of 5°C/min in an argon atmosphere of 800°C for 0.5 hours, and then lowered to room temperature at a cooling rate of 5°C/min to obtain a nickel-nitrogen co-doped carbon matrix. Electrocatalyst.

Comparative Example 1

Mix and disperse dicyandiamide and ammonium chloride with water in a mass ratio of 2:10, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcined at 500°C for 1 hour at a heating rate of 5°C/min, and then lowered to room temperature at a cooling rate of 5°C/min;

The calcined sample and glucose were mixed with water at a mass ratio of 1:5, and then hydrothermally reacted at 180 ° C for 12 hours, and the obtained product was washed with deionized water and ethanol in turn, and then dried;

The hydrothermally treated sample was placed in a quartz tube, calcined at a heating rate of 5°C/min in an argon atmosphere at 1000°C for 0.5 hours, and then lowered to room temperature at a cooling rate of 5°C/min to obtain a nitrogen-doped carbon-based electrocatalyst. .

Comparative Example 2

Mix and disperse nickel chloride, dicyandiamide and ammonium chloride with water in a mass ratio of 3.5:100:500, stir below 80°C, and evaporate to dryness;

Put the evaporated samples into a crucible, calcined at 500°C for 1 hour at a heating rate of 5°C/min, and then lowered to room temperature at a cooling rate of 5°C/min;

The calcined samples were placed in a quartz tube, calcined at a heating rate of 5 °C/min in an argon atmosphere at 1000 °C for 0.5 h, and then lowered to room temperature at a cooling rate of 5 °C/min to obtain a carbon-based electrocatalyst.

In the present invention, the reduction activities of the electrocatalysts obtained in Examples 1 to 5 and Comparative Examples 1 to 2 were tested for carbon dioxide reduction. Scanning diagram; FIG. 7 is the linear voltammetric scan diagram of the electrocatalyst in Example 2 of the present invention; FIG. 8 is the linear voltammetric scan diagram of the electrocatalyst in Example 3 of the present invention; FIG. 9 is the example 4 of the present invention. The linear voltammetry scan diagram of the electrocatalyst; Figure 10 is the linear voltammetry scan diagram of the electrocatalyst in Example 5 of the present invention; Figure 11 is the linear voltammetry scan diagram of the electrocatalyst in Comparative Example 1 of the present invention; Figure 12 It is the linear voltammogram of the electrocatalyst in Comparative Example 2 of the present invention; it can be seen from the above linear voltammogram that the catalysts in Examples 1 to 5 of the present invention have good carbon dioxide reduction activity, while Comparative Examples 1 and 5 have good carbon dioxide reduction activity. The catalyst in Comparative Example 2 had poor reducing activity.

The present invention tested the Faradaic efficiency of the electrocatalysts obtained in Example 1, Comparative Example 1 and Comparative Example 2. The results are shown in Figure 13. Figure 13 shows that the catalysts in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention will Faradaic efficiency curve for the reduction of carbon dioxide to carbon monoxide. It can be seen from FIG. 13 that the nickel-nitrogen co-doped carbon-based electrocatalyst in Example 1 of the present invention has a higher Faradaic efficiency, and the selectivity for carbon dioxide reduction reaction is as high as 99%, while that in Comparative Example 1 and Comparative Example 2 is as high as 99%. The faradaic efficiency of the catalyst is less than 70% at best.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of a nickel-nitrogen co-doped carbon-based electrocatalyst comprises the following steps:

A) dispersing nickel salt, dicyandiamide and ammonium chloride in water, drying and calcining;

B) mixing the calcined product with glucose in water and then carrying out hydrothermal reaction;

C) and calcining the product of the hydrothermal reaction in an argon atmosphere to obtain the nickel-nitrogen co-doped carbon-based electrocatalyst.

2. The method according to claim 1, wherein the nickel salt is a divalent soluble nickel salt.

3. The preparation method according to claim 1, wherein the mass ratio of the nickel salt to the dicyandiamide is (0.2-5): 100, respectively;

the mass ratio of the nickel salt to the ammonium chloride is (0.2-5): 500.

4. the preparation method according to claim 1, wherein the calcining temperature in the step A) is 500-650 ℃;

the calcining time in the step A) is 1-4 hours.

5. The preparation method according to claim 1, wherein the mass ratio of the calcined product in the step A) to the glucose is (0.7-1.5): 5.

6. the preparation method according to claim 1, wherein the temperature of the hydrothermal reaction is 160-200 ℃;

the time of the hydrothermal reaction is 10-20 hours.

7. The preparation method according to claim 1, wherein the temperature of the calcination in the step C) is 800-1100 ℃;

the calcining time in the step C) is 0.5-4 hours.

8. A nickel-nitrogen co-doped carbon-based electrocatalyst prepared by the preparation method of any one of claims 1-7.

9. The nickel-nitrogen co-doped carbon-based electrocatalyst according to claim 8, wherein the mass fraction of nitrogen in the nickel-nitrogen co-doped carbon-based electrocatalyst is 3-6%;

the mass fraction of nickel in the nickel-nitrogen co-doped carbon-based electrocatalyst is 1-3%.

10. Use of the nickel-nitrogen co-doped carbon-based electrocatalyst according to claim 8 or 9 in a reaction for reducing carbon dioxide.

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