Carbon defect catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalytic material preparation, in particular to a carbon defect catalyst as well as a preparation method and application thereof, the general formula of the carbon defect catalyst is WCx, 0 lt; xlt; the catalyst is prepared by adopting a high-temperature solid-phase in-situ carburizing method, has high-concentration carbon defects on the surface, can realize highly selective adsorption of nitrogen and effectively inhibit a hydrogen evolution reaction, so that the Faraday efficiency and the ammonia synthesis rate are improved, and a new solution is provided for industrial application of an electrochemical ammonia synthesis technology.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic material preparation, and in particular to a carbon-defect catalyst and a preparation method and application thereof. Background Art

[0002] Ammonia is an important chemical raw material and energy carrier, widely used in agriculture, industry, and energy. Currently, industrial ammonia synthesis primarily utilizes the Haber-Bosch process, which operates under high-temperature and high-pressure conditions, consumes significant amounts of energy, emits large amounts of carbon dioxide, and poses a serious environmental risk. In recent years, electrochemical ammonia synthesis has garnered widespread attention as an emerging, green ammonia production pathway. This technology, which can be operated at ambient temperature and pressure, reduces energy consumption and greenhouse gas emissions. However, due to the competing hydrogen evolution reaction, electrochemical ammonia synthesis suffers from a low Faradaic efficiency and a slow ammonia synthesis rate, making it difficult to meet the demands of industrial production.

[0003] To improve the efficiency of electrochemical ammonia synthesis, new, highly efficient catalysts are needed to inhibit the hydrogen evolution reaction and enhance the selective adsorption of nitrogen. While currently reported noble metal catalysts exhibit high activity, they are expensive and have limited reserves. Non-noble metal catalysts, while inexpensive, suffer from poor activity and stability. Therefore, there is an urgent need to develop new non-noble metal catalysts to improve the efficiency of electrochemical ammonia synthesis. Summary of the Invention

[0004] To address the above technical problems, embodiments of the present invention provide a carbon-defect catalyst, a preparation method, and an application thereof. The catalyst is prepared by a high-temperature solid-phase in-situ carburization method and has a high concentration of carbon defects on its surface. This catalyst can achieve highly selective adsorption of nitrogen, effectively inhibiting the hydrogen evolution reaction, thereby improving the Faradaic efficiency and ammonia synthesis rate, providing a new solution for the industrial application of electrochemical ammonia synthesis technology.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0006] In one aspect, the present invention provides a carbon defect catalyst, wherein the carbon defect catalyst has the general formula WC x , where 0 <x<1。

[0007] In some embodiments, x is 0.1, 0.25, or 0.4.

[0008] In another aspect, the present invention provides a method for preparing a carbon-defect catalyst, comprising the following steps:

[0009] A. In an atmosphere of hydrogen and argon, a tungsten source and a carbon source are subjected to a reduction reaction to obtain an initial product;

[0010] B. The initial product of step A is subjected to a solid phase in-situ carburization reaction to obtain a carbon defect catalyst.

[0011] In some embodiments, in step A, the volume ratio of hydrogen to argon is (5-15): (85-95).

[0012] In some embodiments, in step A, the tungsten source includes at least one of tungsten dioxide, tungsten trioxide, sodium tungstate, tungsten carbide, sodium octafluorotungstate, and tungsten hexachloride.

[0013] In some embodiments, in step A, the carbon source includes at least one of porous activated carbon, carbon black, carbon nanotubes, and reduced graphene oxide.

[0014] In some embodiments, in step A, the mass ratio of the tungsten source to the carbon source is 1:3 to 5:2.

[0015] In some embodiments, in step A, the reduction reaction time is 0.5 to 2 hours, and the temperature is 400 to 600°C.

[0016] In some embodiments, in step B, the temperature of the solid phase in-situ carburizing reaction is 800-1200° C., and the time is 2-4 hours.

[0017] In another aspect, the present invention provides a carbon-defect catalyst or a carbon-defect catalyst prepared by the above-mentioned preparation method, and its use in ammonia production.

[0018] The beneficial effects of the present invention are:

[0019] WC x(0<x<1) The C vacancy in the electrolyte will make the surrounding area in a state of power deficiency, which can attract and accommodate the lone pair electrons in the N2 molecule, while the H + The electrode is positively charged and repels the C vacancy area, thereby achieving selective adsorption of N2 molecules. Subsequently, the electrode will provide electrons through W to enter the empty antibonding orbit of N2, activating the adsorbed nitrogen to form active nitrogen (marked as * N2), and with H + Hydrogenation reaction occurs to form *The continuous activation and hydrogenation of nitrogen by N2H2 ultimately results in the formation of NH3, which leaves the catalyst surface and enters the electrolyte solution. The more carbon vacancies there are, the more active sites for N2 adsorption there are. In other words, increasing the concentration of carbon vacancies on the catalyst surface can improve the reaction rate of N2 electrocatalytic reduction to ammonia. (Due to the high electronegativity of O and N in WO3 or WN, the corresponding O and N vacancy regions are highly electronegative and highly adsorbent to N, hindering the desorption of NH3 molecules after the reaction.) This catalyst, prepared by a high-temperature solid-phase in-situ carburization method, possesses a high concentration of carbon defects on its surface, enabling highly selective nitrogen adsorption and effectively suppressing the hydrogen evolution reaction, thereby improving the Faradaic efficiency and ammonia synthesis rate. This provides a new solution for the industrial application of electrochemical ammonia synthesis technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 For surfaces with different W / C ratios, a is WC 0.1 , b is WC 0.25 , c is WC 0.4 XPS spectrum of W in nanocrystals;

[0021] Figure 2 a is the SEM image of graphene; b is the SEM image of WC 0.4 / SEM image of porous graphene; c is WC 0.4 / TEM image of porous graphene (the inset is WC 0.4 Particle size distribution of nanocrystals); d is WC 0.4 / BET curve of porous graphene;

[0022] Figure 3 is the LSV curve in saturated N2 and saturated Ar solution;

[0023] Figure 4 is the chronocurrent result at the corresponding potential;

[0024] Figure 5 UV-visible absorption spectrum of the electrolyte after being stained with indophenol blue indicator for 2 hours;

[0025] Figure 6 is the ammonia yield and Faradaic efficiency at the corresponding potential;

[0026] Figure 7 UV-visible absorption spectra of the electrolyte after charging at -0.6 V for 2 h under three control experimental conditions;

[0027] Figure 8 exist 14 N2 and 15 The electrolyte after electrocatalytic reduction under N2 feed gas conditions 1 H-NMR spectroscopy;

[0028] Figure 9 UV-Vis absorption spectrum of the catalytic reaction test in N2 atmosphere electrolyte for 2 hours and repeated 7 times;

[0029] Figure 10 is a bar graph of NH3 production rate and Faraday efficiency;

[0030] Figure 11 The current density curve at -0.6 V for 22 hours. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0032] In order to objectively evaluate the technical effects of the embodiments of the present disclosure, the technical solutions provided by the present disclosure will be described in detail and exemplarily through experimental examples below.

[0033] In order to make the present application easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are merely illustrative and do not limit the scope of application of the present invention.

[0034] Unless otherwise specified, the operations and processing methods involved in this application are conventional methods in the art.

[0035] Unless otherwise specified, the instruments used in this application are conventional instruments in this field.

[0036] Example 1

[0037] Step 101: uniformly mix tungsten hexachloride and reduced graphene oxide in a mass ratio of 1:2;

[0038] Step 102: reducing the mixture in a hydrogen-argon mixed gas (10% hydrogen and 90% argon) at 400° C. for 1 hour to form a composite material of nano-tungsten supported on graphene;

[0039] Step 103: Carburize the composite material in a solid state at 1000°C for 2 hours to form carbon defect WC 0.1 Nanocrystalline / porous graphene composite catalyst.

[0040] Example 2

[0041] Step 101: uniformly mix tungsten trioxide and reduced graphene oxide in a mass ratio of 1:1;

[0042] Step 102: reducing the mixture in a hydrogen-argon mixed gas (10% hydrogen and 90% argon) at 400° C. for 1 hour to form a composite material of nano-tungsten supported on graphene;

[0043] Step 103: Carburize the composite material in a solid state at 1000°C for 2 hours to form carbon defect WC 0.25 Nanocrystalline / porous graphene composite catalyst.

[0044] Example 3

[0045] Step 101: uniformly mix sodium tungstate and reduced graphene oxide at a mass ratio of 5:2;

[0046] Step 102: reducing the mixture in a hydrogen-argon mixed gas (10% hydrogen and 90% argon) at 400° C. for 1 hour to form a composite material of nano-tungsten supported on graphene;

[0047] Step 103: Carburize the composite material in situ at 1000°C for 2 hours to form a high-concentration carbon defect WC 0.4 Nanocrystalline / porous graphene composite catalyst.

[0048] The carbon defect catalysts prepared in Examples 1 to 3 above were prepared by Figure 1 The carbon defect sites caused by high temperature reaction will be occupied by oxygen in the air atmosphere to form WO bonds, such as Figure 1 The intensity of W on the catalyst surface is the sum of the areas (S) of peaks I and II, so the proportion of carbon in tungsten carbide x = S Ⅰ :(S Ⅰ +S Ⅱ ).according to Figure 1 The areas of peaks Ⅰ and Ⅱ in Figures a, b, and c can be calculated to correspond to x values ​​of 0.1, 0.25, and 0.4, i.e., WC 0.1 、WC 0.25 、WC 0.4 , that is, the carbon defect concentrations on the surface of tungsten carbide are 90%, 75%, and 60% respectively.

[0049] Figure 2 The graphene SEM image in Figure a has no load and no holes, so as to compare the morphology with the composite material loaded with tungsten nanoparticles in Figure b; the tungsten loaded on the graphene sheet shown in Figure b is subjected to high-temperature carburization, and the carbon atoms enter the tungsten lattice to form tungsten carbide, thereby causing the carbon-carbon bond to break and eventually forming a porous shape. The red ellipse in Figure b is the hole in the graphene sheet; Figure c is WC 0.4 / TEM image of porous graphene (the inset is WC 0.4 Particle size distribution of nanocrystals); Figure d is WC0.4 / BET curve of porous graphene.

[0050] Figure 2 Graphene and WC are shown 0.4 / Typical SEM and TEM images of porous graphene. It can be seen that WC 0.4 The graphene nanocomposite contains numerous particles and porous graphene sheets (the pores in the graphene sheets are indicated by red circles in panel b), as well as WC nanocrystals uniformly embedded throughout the graphene sheets, free of aggregation and with diameters ranging from 10 to 20 nm (panel c). Graphene obtained by thermal reduction under the same conditions remains intact, without pores (panel a). During the in situ carburization process, where metallic W is anchored on graphene, two scenarios may occur: one is the formation of pores in the graphene due to the carburization depth and the strong bonding energy of WC; the other is the intact C-C bonds between carbon atoms in the tungsten carbide particles and adjacent carbon atoms in the graphene, resulting in the tungsten carbide particles being firmly embedded in the graphene sheets. At the same time, the resulting pores are not uniformly distributed throughout the graphene sheets. The nitrogen adsorption isotherm (inset in panel d) is type IV, with hysteresis loops in the intermediate and high-pressure regions (P / P0 = 0.4-1). The pore sizes in the material range from 20 to 50 nanometers. The porous morphology will promote the efficient diffusion of reactants and products.

[0051] Test example

[0052] Step 1: Loading the WCx nanocrystal / porous graphene composite catalyst prepared in the above embodiment on a carbon cloth carrier to form a catalytic working electrode;

[0053] Step 2: The prepared catalyst working electrode is placed in a commercially available H-type reactor using an H2SO4 electrolyte with a pH value of 2 to 5, and a voltage of -0.2V to -0.6V (relative to the standard hydrogen electrode potential) is applied to perform an electrocatalytic N2 reduction to NH3 activity test at room temperature and pressure, preferably at a voltage of -0.4V. Characterization is performed using an indoxyl blue-UV-visible spectrophotometer to measure the ammonia yield and Faraday efficiency.

[0054] Step 3: Perform 10 cycles of testing on the catalyst to determine whether the catalytic activity is reduced.

[0055] Step 4: Through material characterization techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, as well as in situ testing techniques such as density functional theory calculations and in situ infrared spectroscopy, the selective adsorption mechanism of the catalyst for N2 is revealed, and the mechanism of the catalyst's promotion of the electrochemical ammonia synthesis reaction is clarified.

[0056] 1. Preparation of catalytic electrode

[0057] 5 mg of the catalyst prepared in Example 1, 1 mL of perfluoro(4-methyl-3,6-dioxa-7-octene)sulfonyl fluoride solution, 2 mL of ultrapure water, and 4 mL of anhydrous ethanol were mixed by ultrasonic dispersion for 30 min to form a uniform dispersion. Then, 2 mL of the dispersion was loaded on a 1×1 cm 2 The catalytic carbon cloth was vacuum dried to obtain the catalytic carbon cloth for standby use at a drying temperature of 80°C for 12 h.

[0058] To ensure work efficiency, multiple catalytic electrodes are prepared at one time, which will be used more frequently later. Each 1×1cm 2 Weigh the carbon cloth and record its mass (m1 = 0.0137g). The mass of the electrode after drying (m2 = 0.0142g) is recorded. The mass difference Δm = m2 - m1 = 0.0142 - 0.0137 = 0.0005g. The mass concentration of the perfluoro(4-methyl-3,6-dioxa-7-octene)sulfonyl fluoride solution is 5%. Using 5mg of catalyst, assuming 0.1780g of perfluoro(4-methyl-3,6-dioxa-7-octene)sulfonyl fluoride solution (5% mass fraction) is added, the catalyst ratio is 5 / (5 + 0.1780 * 5%). The amount of catalyst after drying is 0.0005 * 5 / (5 + 0.1780 * 5%) = 0.0005g.

[0059] 2. Construction of test equipment

[0060] A proton exchange membrane was used as the diaphragm. The membrane was first boiled in a 5% H₂O₂ aqueous solution for 1 hour, then boiled in a 0.5M H₂SO₄ solution for another 1 hour, and finally rinsed with ultrapure water for 1 hour (the first treatment). After use, the membrane was rinsed with pure water and stored in a sealed bag. Before the next use, it was softened by soaking in the experimental solution.

[0061] Using an H-type electrolytic cell, the prepared catalytic carbon cloth was sandwiched between platinum electrode holders as the working electrode, a high-purity platinum sheet as the counter electrode, and a Hg / HgSO electrode as the reference electrode in H2SO4 aqueous electrolyte at varying pH values. The electrolytic cell was continuously filled with high-purity nitrogen under closed conditions, while air was removed and nitrogen saturation was maintained. Electrochemical measurements were performed using an electrochemical workstation at room temperature and pressure. All electrode potentials were converted to relative to a standard hydrogen electrode (E(vs RHE) = E(vs Hg / HgSO4) + 0.616 + 0.059 × pH).

[0062] 3. Catalytic performance test

[0063] (1) LSV test (scan range 0 to -1.1 V vs RHE electrode, scan rate 5 mV s -1) (Compared to the actual operation of Hg / Hg2SO4 electrode converted according to the above formula)

[0064] First, test the LSV under argon. Continuously fill the electrolytic cell with high-purity argon for 30 minutes while purging air from the cell and ensuring it is saturated with argon. Then, test the LSV under nitrogen. Continuously fill the electrolytic cell with high-purity nitrogen while purging air from the cell and ensuring it is saturated with nitrogen. Compare the current densities of the LSV curves at the same potential.

[0065] like Figure 3 The two curves shown in the figure exhibit similar trends, but the current densities are clearly different. At the same voltage, the current density in the N2 atmosphere is higher, indicating a more active NRR reaction. Generally speaking, the more negative the voltage, the more pronounced the reduction reaction. However, due to the competing hydrogen evolution side reaction of the ammonia synthesis reaction, hydrogen production becomes more intense as the voltage increases, resulting in a gradual decrease in the Faradaic efficiency. To determine the optimal operating voltage for the ammonia synthesis reaction, a series of ammonia synthesis experiments were conducted at potentials ranging from -0.4 to -1.0 V.

[0066] (2) Chronoamperometry (CA) test

[0067] According to the LSV curve, different voltages were selected to test the current density-time curves of the catalytic electrode at different voltages (such as -0.4, -0.5, -0.6, -0.7, -0.8, -0.9 V). The time was set to 2 h, and the optimal working potential was determined by subsequent determination of the synthetic ammonia yield and Faraday efficiency.

[0068] As the electrode potential gradually increases, the current density gradually increases ( Figure 4 ), indicating that the electrochemical reduction reaction has become stronger, which may be caused by nitrogen reduction to synthesize ammonia or hydrogen evolution. The UV-visible absorption spectrum of the electrolyte after 2h electrocatalysis ( Figure 5 ) showed obvious absorption, proving the catalytic performance of the catalyst. With the increase of voltage, the absorption peak intensity showed a trend of first increasing and then decreasing, with the strongest peak appearing at -0.6V. The ammonia yield ( Figure 6 ) also showed a trend of increasing first and then decreasing with the increase of voltage, with the highest output (17.3ug h -1 mg -1 cat ), while the Faradaic efficiency showed a gradually decreasing trend. Although it showed the highest Faradaic efficiency at -0.4V, the NH3 yield was too low, so -0.6V was selected as the optimal operating voltage, at which the highest ammonia productivity was obtained, and the Faradaic efficiency was also high (5.4%).

[0069] 4. Determination of product yield and Faraday efficiency

[0070] The yield of ammonia synthesized by electrocatalytic reduction of N2 was determined by the indophenol blue method. 4 mL of the electrolyte after the reaction was measured and thoroughly mixed with 500 μL of sodium salicylate (C7H5NaO3) solution (wherein, C7H5NaO3 0.4M, NaOH 0.32M), 50 μL of sodium hypochlorite (NaClO) solution (wherein, NaClO 0.05M, NaOH 0.75M) and 50 μL of sodium nitrosoferricyanide (C5FeN6Na2O) solution (1wt.%), and allowed to stand in the dark for 2 h. The absorbance of the mixed solution was then obtained using a UV-visible spectrophotometer. 0-2 μg mL -1 A concentration-absorbance curve was drawn for the standard NH4Cl solution. The yield of ammonia was calculated using formula 1:

[0071]

[0072] Among them, c NH3 is the measured concentration of ammonia (μg mL -1 ), V is the volume of the electrolyte (mL), t is the reaction time (h), and m is the amount of catalyst used (mg).

[0073] The Faradaic efficiency (FE) is the ratio of the amount of electricity transferred to the total amount of electricity consumed for ammonia synthesis and is calculated using Formula 2:

[0074]

[0075] Where F is the Faraday constant (96485C mol -1 ), n NH3 is the molar amount of ammonia produced (mol), and Q is the total amount of electricity consumed (C).

[0076] 5. Controlled comparative experiment

[0077] In order to further ensure that ammonia is produced by N2 electrocatalytic reduction, three control experiments were performed:

[0078] (1) The original carbon cloth electrode (the original carbon cloth electrode is the carbon cloth without loaded catalyst) is reacted in a N2 saturated solution at the optimal working potential of -0.6 V for 2 hours.

[0079] (2) The catalytic electrode was subjected to open circuit reaction in N2 saturated electrolyte solution for 2 h.

[0080] (3) The catalytic electrode reacted in an Ar saturated solution at an optimal working potential of -0.6 V for 2 h.

[0081] Figure 7UV-visible absorption spectra of the electrolyte after charging at -0.6V for 2 hours under three control experimental conditions. Figure 7 The UV-Vis absorption spectra of the electrolytes obtained from the three comparisons are shown after treatment with indophenol blue as an indicator. Only trace amounts of NH₃ were detected under the three comparative experimental conditions, indicating that the electrocatalytic ammonia synthesis reaction occurs only in an N₂-saturated atmosphere and under a certain applied voltage.

[0082] At the same time, use 15 N2 bound proton NMR spectroscopy ( 1 H NMR) was used for isotope labeling to confirm the actual source of nitrogen in the product ammonia, and the measurement was repeated three times to verify the repeatability and reliability of ammonia production.

[0083] use 15 N2 isotope labeling experiment. Use a sealed reactor, pass Ar gas (4h) to exhaust the air in the reactor (both reaction cells need to exhaust air), close the valve of the reaction cell on the counter electrode side (the purpose is to make only Ar in the entire electrolytic cell without N2), and then pass Ar gas to the reaction cell on the working electrode side. 15 N2, fill the reactor 15 N2. Electrolyze for 2 hours at the optimal working potential, add a certain amount of 15N2 every 10 minutes, then remove the electrolyte and heat and concentrate it at 75℃ to about 1mL. For comparison, 14 The N2 experiments were also carried out in the same manner (i.e., the electrolyte obtained by the experiments with ordinary nitrogen).

[0084] Figure 8 exist 14 N2 and 15 The electrolyte after electrocatalytic reduction under N2 feed gas conditions 1 H-NMR spectroscopy was performed using 14 N2 and 15 The N2 gas feed was isotopically labeled to confirm the true source of NH3. 1 The results of HNMR spectra ( Figure 8 ) shows 14 NH4 and 15 The characteristic triplet and doublet peaks of NH4 are respectively related to the 14 N2 and 15 This indicates that the nitrogen in the ammonia does come from the nitrogen gas used.

[0085] 6. Catalyst stability test

[0086] The service life is tested at the optimal working potential of -0.6V to verify the stability.

[0087] (1) Under nitrogen atmosphere, test the same electrode for 2 hours, pour out the electrolyte and bottle it, then mark it. Repeat 7 times.

[0088] (2) Continue testing for 22 hours in a nitrogen atmosphere to observe whether the current density is stable.

[0089] The durability and stability of the catalyst are also important indicators for evaluating the performance of electrocatalysts. Figure 9 This is the UV-Vis absorption spectrum of a catalytic reaction test in an N2 atmosphere electrolyte, repeated seven times over two hours. Except for the first test, which showed a slightly higher absorbance, the absorbance curves for the remaining repeated tests are essentially identical, demonstrating the good reproducibility of the catalytic reaction experiment. Figure 10 The NH3 production rate and Faradaic efficiency of the alternating 2-hour cycle in N2-saturated electrolyte are shown. It can be seen that during the 7-cycle interval, although there are slight fluctuations, the NH3 production rate remains basically unchanged, and the corresponding Faradaic efficiency also remains stable. After a long-term cycle of 22 hours ( Figure 11 ), there was no significant difference in the catalytic current density.

[0090] In the application examples WC x(0<x<1) The C vacancy in the electrolyte will make the surrounding area in a state of power deficiency, which can attract and accommodate the lone pair electrons in the N2 molecule, while the H + The electrode is positively charged and repels the C vacancy area, thereby achieving selective adsorption of N2 molecules. Subsequently, the electrode will provide electrons through W to enter the empty antibonding orbit of N2, activating the adsorbed nitrogen to form active nitrogen (marked as * N2), and with H + Hydrogenation reaction occurs to form * The continuous activation and hydrogenation of nitrogen by N2H2 ultimately results in the formation of NH3, which then leaves the catalyst surface and enters the electrolyte solution. The more carbon vacancies there are, the more active sites for N2 adsorption there are. In other words, increasing the concentration of carbon vacancies on the catalyst surface can increase the reaction rate of the electrocatalytic reduction of N2 to ammonia. (Due to the high electronegativity of O and N in WO3 or WN, the corresponding O and N vacancy regions are highly electronegative and have strong adsorption properties for N, hindering the desorption of NH3 molecules after the reaction.)

[0091] WC with high concentration of carbon defects on the surface was prepared by high temperature solid phase in situ carburizing method x(0<x<1) Nanocrystals can be used as catalysts for the electrocatalytic nitrogen reduction reaction (eNRR) and achieve highly selective adsorption of N2.

[0092] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0093] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A carbon defect catalyst, characterized in that The general formula of the carbon defect catalyst is WC x , where 0 <x<1。 2. A carbon defect catalyst according to claim 1, characterized in that The x is 0.1, 0.25 or 0.

4.

3. A method for preparing a carbon-defect catalyst according to claim 1 or 2, characterized in that: The following steps are involved: A. In an atmosphere of hydrogen and argon, a tungsten source and a carbon source are subjected to a reduction reaction to obtain an initial product; B. The initial product of step A is subjected to a solid phase in-situ carburization reaction to obtain a carbon defect catalyst.

4. The method for preparing a carbon-defect catalyst according to claim 3, wherein: In step A, the volume ratio of hydrogen to argon is (5-15):(85-95).

5. The method for preparing a carbon-defect catalyst according to claim 3, characterized in that: In step A, the tungsten source includes at least one of tungsten dioxide, tungsten trioxide, sodium tungstate, tungsten carbide, sodium octafluorotungstate, and tungsten hexachloride.

6. The method for preparing a carbon-defect catalyst according to claim 3, characterized in that: In step A, the carbon source includes at least one of porous activated carbon, carbon black, carbon nanotubes, and reduced graphene oxide.

7. The method for preparing a carbon-defect catalyst according to claim 3, characterized in that: In step A, the mass ratio of the tungsten source to the carbon source is 1:3 to 5:

2.

8. The method for preparing a carbon-defect catalyst according to claim 3, characterized in that: In step A, the reduction reaction time is 0.5 to 2 hours, and the temperature is 400 to 600°C.

9. The method for preparing a carbon-defect catalyst according to claim 3, characterized in that: In step B, the temperature of the solid phase in-situ carburizing reaction is 800-1200° C., and the time is 2-4 hours.

10. Use of a carbon-defect catalyst according to claim 1 or 2 or a carbon-defect catalyst prepared by the preparation method according to any one of claims 3 to 9 in the production of ammonia.

Images