Nitrogen-doped carbon material and its application in electrocatalytic generation of hydrogen peroxide in seawater

Abstract

The application belongs to the field of electrocatalytic energy conversion, and particularly relates to a nitrogen-doped carbon material and application of the nitrogen-doped carbon material in electrocatalytic generation of hydrogen peroxide in seawater. The nitrogen-doped carbon material is prepared by using a zinc organic framework (ZIF) as a template to prepare a nitrogen-doped carbon material containing different types of nitrogen. The application uses simulated seawater as an electrolyte solution, which not only can utilize abundant seawater resources, but also can reduce cost, and the generated hydrogen peroxide chemical energy can realize energy sustainability, and has important significance for constructing a green energy atlas.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrocatalytic energy conversion, and particularly relates to a nitrogen-doped carbon material and application thereof in electrocatalytic production of hydrogen peroxide in seawater. BACKGROUND

[0002] Hydrogen peroxide is a valuable and environmentally friendly chemical reagent, which is widely used in various industries such as sewage treatment, chemical oxidation, cosmetics, biological systems, pharmaceuticals, etc. due to its decomposition to produce water and oxygen without harmful residues. Hydrogen peroxide is mainly synthesized by the anthraquinone method in industry, but this synthesis method produces organic pollutants and the synthesis process is complex. Electro-catalytic oxygen reduction synthesis of hydrogen peroxide is a simple method that can realize in-situ production and application, and can effectively avoid the cost and danger caused by storage and long-distance transportation of hydrogen peroxide. However, the catalyst for electro-catalytic oxygen reduction to produce hydrogen peroxide generally has high selectivity under strong acidic or strong alkaline conditions, and the research under neutral conditions is still relatively less. At the same time, the earth is rich in seawater resources, and seawater can be used as an electrolyte solution to realize sustainable utilization of energy. Therefore, it is of great significance to study the catalytic performance of nitrogen-doped carbon materials in electro-catalytic production of hydrogen peroxide in simulated seawater, and to realize sustainable utilization of seawater resources and green energy in the future. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the application aims to provide a nitrogen-doped carbon material and application thereof in electro-catalytic production of hydrogen peroxide in simulated seawater.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0005] A nitrogen-doped carbon material, which is prepared by using zinc organic framework (ZIFs) as a template to prepare nitrogen-doped carbon materials containing different types of nitrogen.

[0006] Further, the ZIFs are used as a template to prepare nitrogen-doped carbon materials containing different types of nitrogen at different temperatures, wherein the temperature is 600-1000℃.

[0007] The nitrogen-doped carbon material contains different types of nitrogen, wherein the different types of nitrogen are graphite nitrogen, pyrrole nitrogen and pyridine nitrogen.

[0008] Application of a nitrogen-doped carbon material, wherein the nitrogen-doped carbon material is applied to electro-catalytic production of hydrogen peroxide in a neutral electrolyte solution.

[0009] Application of the nitrogen-doped carbon material to electro-catalytic production of hydrogen peroxide in seawater.

[0010] The neutral solution is simulated seawater, i.e. 0.5M NaCl solution.

[0011] The nitrogen-doped carbon material has high hydrogen peroxide selectivity in 0.5M NaCl solution, wherein the selectivity is about 95%.

[0012] The present application has the following advantages:

[0013] The present application utilizes ZIFs as templates to prepare different types of nitrogen-doped carbon materials at different temperatures, wherein the different types of nitrogen include graphite nitrogen, pyrrole nitrogen and pyridine nitrogen.

[0014] The nitrogen-doped carbon material obtained by the present application has good electrocatalytic activity and hydrogen peroxide selectivity as a catalyst. Compared with other materials, the material can have high oxygen reduction hydrogen peroxide generation capacity in simulated seawater. The material provides an important research basis for future seawater resource utilization. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The scanning electron microscope images of the nitrogen-doped carbon material provided for the embodiments of the present application are as follows: 600 (a) N-C 700 (b) N-C 800 (c) N-C 900 (d) N-C 1000

[0016] Figure 2 The photoelectron spectrograms of the nitrogen-doped carbon material provided for the embodiments of the present application are as follows: (a) (wherein the horizontal coordinate is Intensity (intensity) in a.u. (absolute unit); the vertical coordinate is Binding Energy (binding energy) in eV); and (b) nitrogen-doped carbon of different types.

[0017] Figure 3 The electrocatalytic oxygen reduction reaction performance graphs of the nitrogen-doped carbon material provided for the embodiments of the present application are as follows: (a) ring disc current of electrocatalytic oxygen reduction reaction (wherein the horizontal coordinate is j (current density) in mA cm -2 ; the vertical coordinate is E (potential) in V, relative to standard hydrogen electrode); and (b) number of electron transfer and hydrogen peroxide selectivity in electrocatalytic reaction (wherein the horizontal coordinate is E (potential) in V, relative to standard hydrogen electrode; the vertical coordinate is n (number of electron transfer) and H2O2% (hydrogen peroxide selectivity)).

[0018] Figure 4 The graphs of different types of nitrogen in the nitrogen-doped carbon material provided for the embodiments of the present application and the binding energy of reactants in the catalytic reaction process are as follows: (wherein the horizontal coordinate is Reaction Coordinate (reaction complex); the vertical coordinate is Free Energy (free energy) in eV).

[0019] Figure 5Figure 1 is a graph showing the performance comparison of the catalysts of the present application under the same conditions. (a) Comparison of the initial potential (where the abscissa is Co-N-C and N-C 800 ; the ordinate is E onset (initial potential), in V); (b) Comparison of the selectivity (where the abscissa is Co-N-C and N-C 800 ; the ordinate is H2O2% (hydrogen peroxide selectivity) DETAILED DESCRIPTION

[0020] The specific content of the present application will be further described in detail below in combination with the drawings and specific examples.

[0021] Example 1

[0022] Dimethylimidazole (A) and zinc nitrate hexahydrate (B) were weighed separately, and then mixed with methanol solution to form solution A and solution B, respectively. The amount of methanol solution added to form each solution was equal to the amount of the mixed substance. The mass ratio of dimethylimidazole (A) to zinc nitrate hexahydrate (B) was 1:4.5.

[0023] The above-formed B solution was added to the A solution under stirring, and after addition, the reaction was continued to stir for 24 h. After the reaction, centrifugal washing was performed, and then vacuum drying was performed at 60°C to obtain ZIFs templates. The synthesized ZIFs were evenly divided into several portions, and each portion was calcined under argon at 600-1000°C for 2 h to obtain nitrogen-doped carbon materials at different temperatures, the morphology of which is shown in Figure 1 The scanning electron microscope results show that the nitrogen-doped carbon materials prepared at different temperatures have a regular polyhedral structure, and as the temperature increases, the regular polyhedral structure collapses and is in a shrinking state. When the temperature increases to 1000°C, the nitrogen-doped carbon material is polymerized from a regular polyhedral structure to form a large micron structure. In addition, as shown in Figure 2 , the photoelectron spectroscopy results show that the nitrogen-doped carbon materials generated at different temperatures contain different proportions of nitrogen-doped types. As the temperature changes, pyrrole nitrogen gradually decreases, graphite nitrogen gradually increases, and pyridine nitrogen first increases and then decreases, because as the temperature continues to increase, the graphite nitrogen structure is more stable than the pyridine nitrogen.

[0024] Example 2

[0025] Catalytic performance of the material Figure 3

[0026] 5 mg of nitrogen-doped carbon materials prepared at different temperatures were respectively dispersed in 1 ml of isopropanol to prepare catalyst solutions. An appropriate amount of the above catalyst solution was added dropwise to a glassy carbon electrode as a working electrode. The rotating disk ring electrode technology was used, and a simulated seawater 0.5M NaCl solution was used as the electrolyte solution. The disk current and ring current of the oxygen reduction reaction of the nitrogen-doped carbon material were tested at a speed of 1600 rpm at room temperature.

[0027] As Figure 3 shown, the disc current density represents the reduction current of the electrocatalytic oxygen reduction reaction, the ring current represents the reduction current of the electrocatalytic production of hydrogen peroxide, and the disc ring current can be used to obtain the number of electron transfer and hydrogen peroxide selectivity in the electrocatalytic reaction process. The test results show that the N-C 800 has the closest number of electron transfer to 2 and the hydrogen peroxide selectivity of about 95%.

[0028] Then, by density functional theory, the adsorption energy of the intermediate in the reaction process of different types of nitrogen-doped carbon in the electrocatalytic reaction is calculated to determine which type of nitrogen-doped nitrogen is more conducive to the production of hydrogen peroxide.

[0029] By density functional calculation, as Figure 4 shown, the calculation results show that in the nitrogen-doped carbon material, graphite nitrogen is more conducive to the production of hydrogen peroxide by electrocatalytic oxygen reduction than pyridine nitrogen and pyrrole nitrogen.

[0030] Example 3

[0031] Comparison of catalytic performance Figure 5

[0032] The same Co-N-C (obtained by prior art) and N-C 800 obtained by the above-mentioned examples are compared in catalytic performance:

[0033] According to the method described in Example 2, the

[0034] 5mg of the above-mentioned material is weighed and dispersed in 1ml of isopropanol to prepare a catalyst solution, and an appropriate amount of the above-mentioned catalyst solution is added to a glassy carbon electrode as a working electrode. The rotating disc ring electrode technology is used, and the simulated seawater 0.5M NaCl solution is used as the electrolyte solution. The disc current and ring current of the material in the electrocatalytic oxygen reduction reaction are tested at a speed of 1600rpm at room temperature.

[0035] Referring to Figure 5 , in the same catalyst loading and the same concentration of NaCl electrolyte solution, the initial potential and hydrogen peroxide selectivity are obtained by testing using the selected disc ring electrode technology. The initial potential and selectivity performance of the two catalysts are compared. Compared with Co-N-C, N-C 800 has a higher initial potential, i.e. higher catalytic activity, and higher hydrogen peroxide selectivity. Therefore, the catalytic performance of N-C 800 is better than that of Co-N-C.

Claims

1. A nitrogen-doped carbon material, characterized by: Preparation of nitrogen-doped carbon materials containing different types of nitrogen by using zinc organic framework ZIFs as templates; The ZIFs are prepared by mixing dimethyl imidazole with zinc nitrate hexahydrate, and the mass ratio of the dimethyl imidazole to the zinc nitrate hexahydrate is 1:4.5; The ZIFs are calcined at 600-1000℃ for 2h under argon atmosphere to obtain nitrogen-doped carbon materials in regular polyhedral structure at different temperatures, and the nitrogen-doped carbon materials are polymerized to form large micron structures in regular polyhedral structure when the temperature is increased to 1000℃; The nitrogen-doped carbon materials formed at different temperatures contain different proportions of nitrogen-doped types; wherein the different types of nitrogen are graphite nitrogen, pyrrole nitrogen and pyridine nitrogen, and with the change of temperature, the pyrrole nitrogen gradually decreases, the graphite nitrogen gradually increases, and the pyridine nitrogen first increases and then decreases.

2. Use of the nitrogen-doped carbon material according to claim 1, characterized in that: Application of the nitrogen-doped carbon materials in electrocatalytic production of hydrogen peroxide in a neutral electrolyte solution.

3. Use of the nitrogen-doped carbon material according to claim 2, characterized in that: Application of the nitrogen-doped carbon materials in electrocatalytic production of hydrogen peroxide in seawater.

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