Three-dimensional open porous doped carbon material, preparation and application thereof

Abstract

The application discloses a three-dimensional open porous doped carbon material and preparation and application thereof, and belongs to the technical field of new energy materials. The three-dimensional open porous doped carbon material is prepared by using a heterocyclic polymer as a carbon source and a doping source, double potassium salt (potassium chloride and potassium bicarbonate) as an activator, and acetylacetone salt as a metal source, and through steps of ball milling, high-temperature carbonization, acid pickling and drying. The whole preparation process is simple, no organic solvent is involved, and the process is green and efficient. The obtained product has a high heteroatom doping amount, a high specific surface area, excellent pore size distribution characteristics and excellent electrochemical performance. Based on the special electrochemical nitrate reduction mechanism, when the product is used for electrocatalytic reduction of nitrate to synthesize ammonia, the yield is high, the faradic efficiency is excellent, and the long-time running stability is good. The application is an effective expansion in the field of ammonia synthesis, and can provide a new idea for application of the porous carbon material in the field of electrocatalytic reduction of nitrate to synthesize ammonia.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials, and particularly relates to a three-dimensional open porous doped carbon material, a preparation method thereof and application of the three-dimensional open porous doped carbon material in electrocatalytic reduction of nitrate to synthesize ammonia. BACKGROUND

[0002] Ammonia is an important industrial and agricultural raw material, is the key to the realization of sustainable production in many industries, and has high application value. At present, ammonia is still mainly produced by the traditional Haber-Bosch method, which needs to be carried out in a high-temperature and high-pressure environment and needs to rely on large-scale and centralized infrastructure. The Haber process is an energy-intensive process, which not only consumes a large amount of energy, but also produces a large amount of carbon dioxide, which is not conducive to the sustainable development of energy and environment. Therefore, the technical personnel in the field are committed to exploring some routes for ammonia synthesis relying on renewable energy generated electricity, and the electrocatalytic reduction of nitrate to synthesize ammonia process is one of the relatively green and efficient ammonia synthesis technologies. The process can produce a large amount of ammonia in aqueous electrolyte by using electrocatalytic materials, and the working condition of the process is room temperature and room pressure, which can realize low energy consumption and zero carbon emission for ammonia synthesis, and has good application prospect.

[0003] In order to more efficiently utilize the method of electrocatalytic reduction of nitrate for synthesis of ammonia reaction, it is necessary to develop efficient catalytic materials that can convert nitrate ions into ammonia molecules on the electrode interface. Since the 8-electron transfer process of electrocatalytic reduction of nitrate to ammonia is relatively complex, many by-products will be produced, and the potential of nitrate reduction to ammonia is usually below the hydrogen evolution reaction potential, which will produce hydrogen, consume too many electrons, and ultimately lead to low Faraday efficiency, so the corresponding catalytic material must have high selectivity in addition to high activity.

[0004] Metal iron and its compounds generally have certain nitrate electrocatalytic activity and can be prepared into nanoparticles supported on a catalyst carrier for electrocatalytic reduction of nitrate. However, general iron-based nanoparticles lack stability and durability, are easily oxidized or agglomerated, and thus reduce the catalytic activity.

[0005] Porous carbon materials can provide a large number of reaction sites and material transport channels for catalytic reactions due to their rich pore structure and large specific surface area, and are often used as catalyst carriers for various electrocatalytic reactions. However, the direct use of porous carbon materials is limited due to the lack of chemically adsorbed active sites on their surface. Porous doped carbon obtained by chemical modification of porous carbon materials is a good metal nanoparticle carrier. Doping nitrogen, sulfur and other heteroatoms in porous carbon materials can create defects, and heteroatoms can effectively form coordination bonds with metals, thereby anchoring metal particles in defect structures containing heteroatoms. This material can help improve the stability of metal nanoparticles and prevent agglomeration.

[0006] Chinese patent CN 114436242 B discloses a three-dimensional heteroatom-doped porous carbon material and its preparation method and application. It is prepared by cross-coupling reaction of a double-halogen aromatic heterocyclic organic monomer, a hydroxyl-containing aromatic conjugated organic monomer and anhydrous potassium carbonate, and then a three-dimensional heteroatom-containing covalent organic framework material is prepared. The three-dimensional heteroatom-doped porous carbon material is obtained by calcining the three-dimensional heteroatom-containing covalent organic framework. The carbon material disclosed in this document also has a high heteroatom doping content and a high specific surface area, which can provide a large number of contact sites and improve the electrochemical performance of the material. However, the production process of the three-dimensional porous carbon material using this method is complicated. The organic framework material can be obtained by mixing the monomer with the base and adding the solvent at 150-170℃ for 4-5 hours. A large amount of organic solvent N,N-dimethylacetamide is used in the process, which is not conducive to the development of green and clean production. This document mainly introduces the application of the carbon material as a supercapacitor electrode material in the energy storage field, and reveals its excellent electrochemical performance. It is unknown whether the carbon material has high selectivity and can be efficiently used in the electrocatalytic reduction of nitrate to synthesize ammonia.

[0007] Although there is some research on doped carbon materials, it is still a difficult technical problem to use a simple and green method to prepare a three-dimensional open porous carbon material structure and ensure the doping level of heteroatoms in the carbon material, so that it can stabilize metal nanoparticles, improve their dispersion, and be efficiently applied in the field of electrocatalytic reduction to synthesize ammonia. SUMMARY

[0008] The purpose of the present application is to solve the problems existing in the prior art, and to provide a three-dimensional open porous doped carbon material with highly developed pores and excellent electrochemical performance. The material is obtained by a solvent-free preparation method, which is simple, environmentally friendly and easy to industrialize. When the material is used for electrocatalytic reduction of nitrate to synthesize ammonia, it not only has high yield and excellent faradaic efficiency, but also has good long-term running stability.

[0009] The technical scheme of the present application is: a preparation method of three-dimensional open porous doped carbon material, the specific preparation process is as follows:

[0010] 1) Measure the heterocyclic polymer, potassium bicarbonate, potassium chloride and acetylacetone salt, mix and grind into powder;

[0011] Among them, the heterocyclic polymer is used as a carbon source and a heteroatom doping source at the same time, the double potassium salt (potassium chloride and potassium bicarbonate) is an activator, and the acetylacetone salt is a metal source.

[0012] The purpose of selecting the heterocyclic polymer as the initial raw material is that the direct doping of the heteroatom is realized before the reaction, compared with the preparation scheme of separately adding a carbon source and a heteroatom doping source, the operation steps are simplified, and the final doping is more uniform.

[0013] The reason why the acetylacetone salt is selected as the metal source in the present application is that it contains heteroatoms as an organic metal salt, which can further dope and modify the carbon material. In addition, compared with traditional metal salts (such as metal sulfate, chloride salt, etc.), the crystallinity of acetylacetone salt is smaller, and it is not easy to absorb water, so it is more convenient to carry out dry grinding, which can make the mixed powder obtained by ball milling more uniform, and is beneficial to the preparation of the final product.

[0014] The main purpose of selecting the double potassium salt (potassium chloride and potassium bicarbonate) as the activator is that potassium bicarbonate plays a role in gas activation and pore forming, which is beneficial to the formation of adjustable disordered microporous and mesoporous structures on the product; potassium chloride itself has no gas activation effect, but it can be fully mixed with the precursor in the molten state and act as a salt template, and after cooling and washing away the potassium chloride, an open and ordered macroporous structure is left; the use of the two kinds of potassium salt together can optimize the pore size distribution of the material to the greatest extent, which is helpful for the final product to present a three-dimensional open and interconnected pore morphology.

[0015] 2) Put the powder obtained in the above step into a tube furnace and carbonize under an inert atmosphere;

[0016] 3) After acid washing the carbonized product, washing to neutral and drying, a three-dimensional open porous doped carbon material is obtained.

[0017] Further, in step 1), the heterocyclic polymer is selected from any one or derivative of any one of polyphenylene sulfide, polyaniline, polythiophene, polypyrrole, poly aryl sulfone, polyether sulfone, polyethylene terephthalate, polyether ketone, polyamide, polybenzimidazole, poly-p-phenylene benzobisoxazole, polyoxazoline, polyquinoline and polyimide.

[0018] Further, in step 1), the mass ratio of potassium chloride, potassium bicarbonate and heterocyclic polymer is 1-10:1-10:1.

[0019] Further, in step 1), the mass ratio of the acetylacetone salt and the heterocyclic polymer is 0.01-5:1.

[0020] Further, the acetylacetone salt is selected from one or more of the following: acetylacetone iron, acetylacetone cobalt, acetylacetone molybdenum, acetylacetone zinc, acetylacetone palladium, acetylacetone nickel, acetylacetone chromium, acetylacetone copper, acetylacetone platinum, acetylacetone rhodium, acetylacetone ruthenium, acetylacetone lanthanum, acetylacetone indium, acetylacetone manganese, acetylacetone hafnium, acetylacetone iridium, acetylacetone thorium, acetylacetone titanium, acetylacetone vanadium, acetylacetone barium, acetylacetone magnesium, acetylacetone cadmium, acetylacetone zirconium, acetylacetone lead, acetylacetone gallium, acetylacetone strontium, acetylacetone silver, acetylacetone gadolinium, acetylacetone praseodymium, and acetylacetone aluminum in a reasonable metal valence state.

[0021] Further, in step 1), the grinding process is carried out in a planetary ball mill, the rotation speed of the planetary ball mill is 200-500 r / min, and the ball milling time is 1-60 min, wherein the forward rotation is 1-59 min and the reverse rotation is 1-59 min.

[0022] 6. The method of claim 1, wherein in step 2), the heating rate of the carbonization is 1-10 ℃ / min, and after reaching 600-1200 ℃, the temperature is maintained for 1-6 h, and then the temperature is lowered to 100-400 ℃ at a rate of 1-10 ℃ / min, and the material is naturally cooled to room temperature.

[0023] Further, in step 3), the acid pickling process uses hydrochloric acid or sulfuric acid as the acid pickling solution, the concentration of the acid pickling solution is 1-5 mol / L, the temperature is 30-80 ℃, and the treatment time is 1-5 h.

[0024] The three-dimensional open porous doped carbon material prepared according to the above method has a three-dimensional open porous structure, and is doped with heteroatoms, and the heteroatoms and the nano metal loaded on the surface form a coordination bond, anchoring the metal particles in the defect structure of the heteroatoms.

[0025] The three-dimensional open porous doped carbon material can be applied in the electrocatalytic reduction of nitrate to synthesize ammonia, and has high yield and high faradic efficiency of the ammonia product, and has good long-term running stability.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] 1. The application uses a heterocyclic polymer as a carbon source and a heteroatom doping source, double potassium salt (potassium chloride and potassium bicarbonate) as an activator, and acetylacetone salt as a metal source to obtain a three-dimensional open porous doped carbon material with highly developed pore structure through ball milling, high-temperature carbonization, acid washing, drying and other steps. The preparation process is simple and reliable, the reaction process is efficient, and industrialization is easy to realize;

[0028] 2. The three-dimensional open porous doped carbon material prepared in the application has a high heteroatom doping amount, a high specific surface area (up to 1986 m 2 g -1 ) and excellent pore size distribution (microporous, mesoporous and macroporous structures), and the highly doped surface also brings more defect structures (I D / I G =1.02). The defect structure has good anchoring ability for metal nano-sites, which can improve the stability of metal nanoparticles and reduce the phenomenon of particle agglomeration, so that the catalytic activity of the material is effectively improved;

[0029] 3. The three-dimensional open porous doped carbon material disclosed in the application is a dynamic pre-catalyst, which generates zero-valent nano-iron particles in situ during the actual reaction process, and is used for electrocatalytic reduction of nitrate to synthesize ammonia. The reaction has high yield, excellent faradic efficiency, and good long-term running stability;

[0030] 4. The preparation scheme of the three-dimensional open porous carbon material disclosed in the application does not involve organic solvents, and is a green and environmentally friendly preparation process, which fully embodies the environmental friendliness of the scheme. The overall preparation process is simple and efficient. The application is an effective expansion in the field of ammonia synthesis, and provides a new idea for the application of new type of catalytic material in the field of electrocatalytic reduction of nitrate to synthesize ammonia, which has important scientific significance and economic value. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Scanning electron microscope image of the three-dimensional open porous carbon material loaded with nano-metal iron sites prepared in Example 2;

[0032] Figure 2 Three-dimensional reconstruction image of the three-dimensional open porous carbon material loaded with nano-metal iron sites prepared in Example 2, characterized by industrial computed tomography;

[0033] Figure 3 XRD pattern of the three-dimensional open porous carbon material loaded with nano-metal iron sites prepared in Example 2;

[0034] Figure 4 Raman spectrum of the three-dimensional open porous carbon material loaded with nano-metal iron sites prepared in Example 2;

[0035] Figure 5Mercury intrusion test curve of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2;

[0036] Figure 6 Nitrogen adsorption-desorption isotherm curve of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2;

[0037] Figure 7 Chronoamperometric curve of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2 at different voltages;

[0038] Figure 8 Ammonia yield and Faraday efficiency diagram of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2;

[0039] Figure 9 X-ray photoelectron spectrogram of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2;

[0040] Figure 10 Nuclear magnetic resonance spectrogram of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2 after reaction using nitrogen 15 isotope;

[0041] Figure 11 Long-time cycle stability diagram of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2. DETAILED DESCRIPTION

[0042] The technical solutions of the present application are further described below in conjunction with the accompanying drawings, but are not limited thereto, and any modification or equivalent replacement to the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application shall be encompassed in the protection scope of the present application.

[0043] Example 1

[0044] Accurately weigh 0.5 g of polyphenylene sulfide, 2.0 g of potassium bicarbonate and 2.0 g of potassium chloride into a ball mill jar, run in a planetary ball mill at a speed of 400 r / min for 30 min (forward rotation for 15 min and reverse rotation for 15 min), take the ground powder, carbonize in a tube furnace, heat to 800℃ at a rate of 5℃ / min under nitrogen atmosphere, keep for 2 h, then cool to 400℃ at a rate of 5℃ / min, and then cool to room temperature naturally. Finally, the obtained carbonized product is washed with 1 mol / L hydrochloric acid at 50℃ for 2 h, the acid washing process is carried out in a magnetic stirrer at a speed of 400 r / min, then repeatedly washed with water to neutral, and then dried to obtain a three-dimensional open porous sulfur-doped carbon material.

[0045] Example 2

[0046] Accurately weigh 0.5 g of polyphenylene sulfide, 2.0 g of potassium bicarbonate, 2.0 g of potassium chloride and 0.5 g of iron acetylacetonate into a ball mill jar, run in a planetary ball mill at a speed of 400 r / min for 30 min (15 min forward rotation and 15 min reverse rotation), take the ground powder and carbonize in a tube furnace, under nitrogen atmosphere, heat to 800℃ at a rate of 5℃ / min, keep for 2 h, then cool to 400℃ at a rate of 5℃ / min, and then cool to room temperature naturally. Finally, the obtained carbonized product is washed with 1 mol / L hydrochloric acid at 50℃ for 2 h, the acid washing process is carried out in a magnetic stirrer, the rotation speed is 400 r / min, after repeated water washing to neutral, drying, a three-dimensional open porous sulfur-doped carbon material loaded with nano metal iron sites is obtained, the yield is 26%, the mass percentage of doped sulfur atoms is 16wt% of the total mass of the porous carbon material, the mass percentage of doped oxygen atoms is 12wt% of the total mass of the porous carbon material, and the total doping amount of heteroatoms is 28wt%.

[0047] Example 3

[0048] Accurately weigh 0.5 g of polyphenylene sulfide, 2.0 g of potassium bicarbonate, 2.0 g of potassium chloride and 0.5 g of iron acetylacetonate into a ball mill jar, run in a planetary ball mill at a speed of 400 r / min for 30 min (15 min forward rotation and 15 min reverse rotation), take the ground powder and carbonize in a tube furnace, under nitrogen atmosphere, heat to 800℃ at a rate of 5℃ / min, keep for 2 h, then cool to 400℃ at a rate of 5℃ / min, and then cool to room temperature naturally. Finally, the obtained carbonized product is washed with 1 mol / L hydrochloric acid at 50℃ for 2 h, the acid washing process is carried out in a magnetic stirrer, the rotation speed is 400 r / min, after repeated water washing to neutral, drying, a three-dimensional open porous sulfur-doped carbon material loaded with nano metal iron sites is obtained, the yield is 26%, the mass percentage of doped sulfur atoms is 16wt% of the total mass of the porous carbon material, the mass percentage of doped oxygen atoms is 12wt% of the total mass of the porous carbon material, and the total doping amount of heteroatoms is 28wt%.

[0049] Example 4

[0050] Accurately weigh 0.5 g of polyphenyl sulfide, 4.0 g of potassium bicarbonate, 4.0 g of potassium chloride and 0.5 g of iron acetylacetonate into a ball mill jar, run in a planetary ball mill at a speed of 400 r / min for 30 min (15 min forward rotation and 15 min reverse rotation), take the ground powder to carbonize in a tube furnace, under nitrogen atmosphere, heat to 800℃ at a rate of 5℃ / min, keep for 2 h, then cool to 400℃ at a rate of 5℃ / min, and then cool to room temperature naturally. Finally, the obtained carbonized product is washed with 1 mol / L hydrochloric acid at 50℃ for 2 h, the acid washing process is carried out in a magnetic stirrer, the speed is 400 r / min, after repeated water washing to neutral, drying, to obtain a three-dimensional open porous sulfur-doped carbon material loaded with nano metal iron sites, the yield is 15%, the mass percentage of doped nitrogen atoms is 3wt% of the total mass of the porous carbon material, the mass percentage of doped oxygen atoms is 11wt% of the total mass of the porous carbon material, and the total doping amount of heteroatoms is 14wt%.

[0051] Example 5

[0052] Accurately weigh 0.5 g of polyphenyl sulfide, 4.0 g of potassium bicarbonate, 4.0 g of potassium chloride and 0.5 g of iron acetylacetonate into a ball mill jar, run in a planetary ball mill at a speed of 400 r / min for 30 min (15 min forward rotation and 15 min reverse rotation), take the ground powder to carbonize in a tube furnace, under nitrogen atmosphere, heat to 800℃ at a rate of 5℃ / min, keep for 2 h, then cool to 400℃ at a rate of 5℃ / min, and then cool to room temperature naturally. Finally, the obtained carbonized product is washed with 1 mol / L hydrochloric acid at 50℃ for 2 h, the acid washing process is carried out in a magnetic stirrer, the speed is 400 r / min, after repeated water washing to neutral, drying, to obtain a three-dimensional open porous sulfur-doped carbon material loaded with nano metal iron sites.

[0053] Example 6

[0054] Accurately weigh 0.5 g of polyphenyl sulfide, 4.0 g of potassium bicarbonate, 4.0 g of potassium chloride and 0.5 g of iron acetylacetonate into a ball mill jar, run in a planetary ball mill at a speed of 400 r / min for 30 min (15 min forward rotation and 15 min reverse rotation), take the ground powder to carbonize in a tube furnace, under nitrogen atmosphere, heat to 800℃ at a rate of 5℃ / min, keep for 2 h, then cool to 400℃ at a rate of 5℃ / min, and then cool to room temperature naturally. Finally, the obtained carbonized product is washed with 1 mol / L hydrochloric acid at 50℃ for 2 h, the acid washing process is carried out in a magnetic stirrer, the speed is 400 r / min, after repeated water washing to neutral, drying, to obtain a three-dimensional open porous sulfur-doped carbon material loaded with nano metal iron sites.

[0055] Example 7

[0056] Accurately weigh 0.5 g of polyphenylene sulfide, 2.0 g of potassium bicarbonate, 2.0 g of potassium chloride, and 0.5 g of cobalt acetylacetonate into a ball mill jar. Mill the mixture in a planetary ball mill at 400 rpm for 30 min (15 min forward, 15 min reverse). The milled powder is then carbonized in a tube furnace under a nitrogen atmosphere. The temperature is increased to 800 °C at a rate of 5 °C / min and held for 2 h. The temperature is then decreased to 400 °C at a rate of 5 °C / min and allowed to cool naturally to room temperature. Finally, the carbonized product is acid-washed at 50 °C with 1 mol / L hydrochloric acid for 2 h using a magnetic stirrer at 400 rpm. After repeated washing with water until neutral, the mixture is dried to obtain a three-dimensional open porous sulfur-doped carbon material with nano-cobalt metal sites.

[0057] Relevant performance tests:

[0058] 1. The three-dimensional open porous carbon material with loaded nano-metal iron sites prepared in Example 2 is shown in the scanning electron microscope image as an interconnected three-dimensional open porous structure, as detailed in the attached figure. Figure 1 As shown.

[0059] 2. Appendix Figure 2 The image shown is a three-dimensional reconstruction image of the three-dimensional open porous carbon material with loaded nano-metal iron sites prepared in Example 2, characterized by industrial computed tomography. The results show that the pore structure on the carbon material obtained by this method is highly open in three dimensions. This highly developed pore structure will greatly improve the reaction area and mass transfer channels of the material, making it an ideal carrier for electrocatalytic applications.

[0060] 3. The XRD pattern of the three-dimensional open porous carbon material with loaded nano-metal iron sites prepared in Example 2 is shown below. Figure 3 As shown in the figure, the material exhibits FeS2 microcrystal diffraction peaks before the reaction, and a series of new diffraction peaks appear in the XRD pattern after the reaction at 0.65V. Other metal sites appearing in the reaction can synergistically catalyze the nitrate reduction reaction, and the presence of ammonium nitrate indicates that the material successfully synthesized ammonia under electrochemical conditions; the Raman spectrum is shown below. Figure 4 As shown in the figure, the high doping of surface heteroatoms leads to more defect structures, I D / I G =1.02, this property can improve the anchoring ability of carbon materials to metal nanosites.

[0061] 4. Figure 5 The figure shows the mercury intrusion porosimetry curve of the three-dimensional open porous carbon material with loaded nano-metal iron sites prepared in Example 2. As can be seen from the figure, the carbon material prepared in this example has obvious macroporous structure and excellent pore size distribution.

[0062] 5.Figure 6 The nitrogen isothermal adsorption-desorption curve of the three-dimensional open porous carbon material loaded with nanometer metal iron sites prepared in Example 2 is shown in the figure. The adsorption amount sharply increases at the relative pressure close to zero, indicating that there are a large number of micropores in the material. A certain hysteresis loop appears at the relative pressure of about 0.8, indicating that the material has a certain mesoporous structure. When the relative pressure is close to 1, the curve shows a significant upward trend, indicating that the material has a macroporous structure.

[0063] 6. 3 mg of the three-dimensional open porous doped carbon material prepared in Example 2, 170 μL of ultrapure water, 70 μL of isopropyl alcohol, and 10 μL of a 5 wt% Nafion solution were mixed in a centrifuge tube, ultrasonic treatment was performed for 1 h to uniformly disperse them, and then a certain amount was dropped onto a glassy carbon electrode, and after natural air drying, it was measured;

[0064] The above-prepared glassy carbon electrode was used as the working electrode, a platinum mesh was used as the counter electrode, and a silver-silver chloride electrode was used as the reference electrode, which were applied to an H-type electrolytic cell including cathode and anode, and were separated by a Nafion proton exchange membrane in the middle. The anode was added with a 0.1 mol / L sodium hydroxide electrolyte, and the cathode was added with a 0.5 mol / L sodium nitrate electrolyte and a 0.1 mol / L sodium hydroxide electrolyte. The chronoamperometry test was performed at a working voltage (relative to the reversible hydrogen electrode) of -0.40 V, -0.45 V, -0.50 V, -0.55 V, -0.60 V, -0.65 V, -0.70 V. The chronoamperometry curve measured is shown in Figure 7 The reaction electrolyte collected in the above step was tested according to the indophenol blue colorimetric method, and the ammonia yield and Faraday efficiency diagrams obtained are shown in Figure 8 The ammonia yield of the material is highest at -0.65 V, which can reach 10509 μg cm -2 h -1 , and the Faraday efficiency is as high as 93%, indicating that the material has excellent ability to electrocatalyze the reduction of nitrate to synthesize ammonia.

[0065] The three-dimensional open porous carbon material was collected and characterized by X-ray photoelectron spectroscopy, and the dynamic evolution information of the metal iron nanometer sites after the reaction was obtained, as shown in Figure 9 .

[0066] 7. The glassy carbon electrode (the preparation method of the glassy carbon electrode is the same as above) was used as the working electrode, a platinum mesh was used as the counter electrode, and a silver-silver chloride electrode was used as the reference electrode, which were applied to an H-type electrolytic cell including cathode and anode, and were separated by a Nafion proton exchange membrane in the middle. The anode was added with a 0.1 mol / L sodium hydroxide electrolyte, and the cathode was added with a 0.5 mol / L sodium nitrate electrolyte and a 0.1 mol / L sodium hydroxide electrolyte. The chronoamperometry test was performed at -0.65 V, and then the obtained solution was characterized and tested by nuclear magnetic resonance, as shown in Figure 10As shown, the characteristic doublet of nitrogen 15 isotope ammonia product at chemical shift 7.2 is observed, and the quantitative result is similar to that obtained by ultraviolet spectrophotometry, indicating that the ammonia in the catalytic product completely comes from sodium nitrate, rather than environmental interference factors.

[0067] 8. A glassy carbon electrode (the preparation method of the glassy carbon electrode is the same as above) is used as a working electrode, a platinum net is used as a counter electrode, and a silver-silver chloride electrode is used as a reference electrode, an H-shaped electrolytic cell including a cathode and an anode is applied, a Nafion proton exchange membrane is used to separate the middle part, a sodium hydroxide electrolyte with a concentration of 0.1 mol / L is added to the anode, a sodium nitrate electrolyte with a concentration of 0.5 mol / L and a sodium hydroxide electrolyte with a concentration of 0.1 mol / L are added to the cathode, and a long-time chronoamperometry test is performed at-0.65 V to observe the stability of the material, and the result is shown in Figure 11 The result shows that the reaction stability of the three-dimensional open porous carbon material is excellent, and the reduction current still does not decay after 18000 s, indicating that the three-dimensional open porous carbon electrode material prepared by the method has excellent stability.

[0068] The above description is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent flow transformation obtained by using the content of the specification and the drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. Use of a three-dimensional open porous doped carbon material for the electrocatalytic reduction of nitrates to synthesize ammonia, characterized in that, The carbon material is in a three-dimensional open porous shape interconnected with each other, and the structure surface is highly doped with heteroatoms, and the heteroatoms form coordination bonds with the metal loaded on the surface, anchoring the metal particles in the defect structure of the heteroatoms; the preparation method of the carbon material is as follows: 1) Measure the heterocyclic polymer, potassium bicarbonate, potassium chloride and acetylacetone salt, mix and grind into powder; the heterocyclic polymer used is any one or derivative of any one of polyphenylene sulfide, polyaniline and polythiophene; the acetylacetone salt is selected from any one or more of acetylacetone iron, acetylacetone cobalt and acetylacetone molybdenum; 2) Put the powder obtained in the above step into a tube furnace and carbonize under inert atmosphere; 3) After acid washing the carbonization product, wash with water to neutral and dry, obtain a three-dimensional open porous doped carbon material.

2. Use of the three-dimensional open porous doped carbon material according to claim 1 for the electrocatalytic reduction of nitrate salts for the synthesis of ammonia, characterized in that, The mass ratio of potassium chloride, potassium bicarbonate and heterocyclic polymer is 1-10:1-10:

1.

3. Use of the three-dimensional open porous doped carbon material according to claim 1 for the electrocatalytic reduction of nitrate salts for the synthesis of ammonia, characterized in that, The mass ratio of acetylacetone salt and heterocyclic polymer is 0.01-5:

1.

4. Use of the three-dimensional open porous doped carbon material according to claim 1 for the electrocatalytic reduction of nitrate salts for the synthesis of ammonia, characterized in that, In step 1), the grinding process is carried out in a planetary ball mill, the rotation speed of the planetary ball mill is 200-500 r / min, and the ball milling time is 1-60 min, wherein the forward rotation is 1-59 min and the reverse rotation is 1-59 min.

5. Use of the three-dimensional open porous doped carbon material according to claim 1 for the electrocatalytic reduction of nitrates to synthesize ammonia, characterized in that, In step 2), the heating rate of carbonization is 1-10 ℃ / min, after reaching 600-1200 ℃, it is kept for 1-6 h, then it is cooled to 100-400 ℃ at a rate of 1-10 ℃ / min, and then it is naturally cooled to room temperature.

6. Use of the three-dimensional open porous doped carbon material according to claim 1 for the electrocatalytic reduction of nitrate salts for the synthesis of ammonia, characterized in that, In step 3), hydrochloric acid or sulfuric acid is used as the acid washing solution, the concentration of the acid washing solution is 1-5 mol / L, the temperature is 30-80 ℃, and the treatment time is 1-5 h.

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