Method for preparing MoxNy by salt-assisted topological nitridation of molybdenum oxide

Abstract

The invention provides a method for preparing MoxNy through salt-assisted topological nitridation of molybdenum oxide. The preparation method comprises the following steps: mixing molybdenum oxide and metal salt according to a ratio, putting the mixture into a tubular furnace, carrying out nitridation reaction in an ammonia gas atmosphere, cooling the obtained product, and carrying out acid pickling, water washing and drying to obtain a MoxNy material; the molar ratio of the molybdenum oxide to the metal salt is 1: (15-35). According to the invention, the structure and morphology of the product can be optimized by regulating and controlling different salts to assist nitridation and the molybdenum / salt ratio, and the nitrogen-rich MoN nanobelt and the highly nitrogen-rich Mo5N6 one-dimensional porous nanobelt can be prepared by precise regulation and control. In addition, the high nitrogen-rich type Mo5N6 has excellent high specific capacitance. According to the method, low-cost KCl and NaCl are adopted as salt auxiliary agents, and the obtained nitride is high in purity and controllable in phase; meanwhile, the synthesis process is simple, and batch and large-scale preparation is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and in particular to a method for preparing Mo by salt-assisted topological nitridation of molybdenum oxide. x N y method. Background Art

[0002] In recent years, with the rapid development and application of portable devices, wearable electronic devices, new energy electric vehicles and mobile communications, people's demand for miniaturized energy storage devices with high volume energy / power density has become more and more urgent. As a new type of energy storage device, supercapacitors have the characteristics of high power density, fast charging and discharging, long cycle life and safety, and have attracted widespread attention in the field of electrochemical energy storage. The core component of supercapacitors is the electrode material, and its composition and structure largely determine the energy storage characteristics of supercapacitors. Transition metal molybdenum nitride (MoN) x N y ) shines with outstanding advantages such as high theoretical specific capacitance, high tap density, good chemical stability and excellent conductivity. It is a new type of electrochemical energy storage material that combines high power / energy density pseudocapacitor. x N y It has a variety of phases and crystal structures. The main ones reported in the literature include: cubic γ-Mo 2 N, tetragonal β-Mo 2 N, Hexagonal δ 1 -MoN, hexagonal δ 2 -MoN, Hexagonal δ 3 -MoN, cubic Mo 3 N 2 , Hexagonal Mo 5 N 6 and MoN 2 Among them, nitrogen-deficient Mo 2 N (x:y<1) is the most common, nitrogen-rich Mo x N y There are few reports on the preparation and application of (x:y≥1) phases, and they are mostly used in the field of electrocatalysis, and less used in supercapacitor research.

[0003] Currently synthesized Mo x N y Nanomaterials are still limited to high temperature and high pressure method, chemical vapor deposition method, topological transformation method and salt template method, which can only obtain single phase Mo. x N y Among them, the high temperature and high pressure method can provide enough energy to destroy strong chemical bonds and effectively prevent N atoms from diffusing out of the Mo metal lattice at high temperatures, but high temperature will make Mo x N ySintering and the resulting product contains impurities (such as Mo, MoO 2 ), affecting the specific surface area of ​​the material or covering the surface active energy storage sites. At the same time, the preparation conditions are harsh and the universality is poor. Chemical vapor deposition method selects appropriate molybdenum precursors to be pre-deposited on the substrate (Si / SiO 2 ) and placed in a suitable nitrogen source for nitridation deposition reaction to prepare high-quality, large-area single-layer molybdenum nitride film, but this method has low yield, large substrate mass and is difficult to transfer, and is not suitable for the preparation of electrode materials. In a broad sense, the topological transformation method is to replace non-metallic C, O, S and other elements in the molybdenum precursor with nitrogen atoms in a nitrogen-containing environment to obtain a target product with unchanged morphology, which can be better used in the preparation of electrode materials, but only a single phase can be obtained, and it is difficult to achieve Mo from the same precursor. x N y Phase regulation. The salt template method mainly uses a suitable salt as a template or precursor. Through the lattice matching effect between the salt and the target product, MoN, the target product is promoted to grow along the two-dimensional surface of the salt or restricted in a specific direction to achieve the preparation of large-area two-dimensional (2D) MoN nanosheets. For example, the literature "Salt-Templated Synthesis of 2D Metallic MoN and Other Nitrides[J]. ACS Nano, 2017, 11(2): 2180-2186." and the literature "Single-Crystal Nitrogen-Rich Two-Dimensional Mo 5 N 6 Nanosheets for Efficient and Stable Seawater Splitting[J]. ACS Nano, 2018, 12(2): 12761-12769. "Alkali metal salts such as sodium chloride or potassium chloride (NaCl, 640 g or KCl, 500 g) were used as templates, and the lattice matching between the salt and the target product MoN was used to make MoO 3 Epitaxial growth occurs on the salt surface to prepare 2D layered MoN nanosheets. The above literature shows that the salt template method is a simple, feasible and highly applicable method that can be widely used in the preparation of 2D molybdenum nitride. The melting point, crystal structure and size of the salt will affect the size, thickness and crystal structure of the target product, and the growth mechanism involved is a bottom-up nucleation-growth process, but how to choose a suitable salt as a template and the extremely large amount of salt used (about 100 grams) reported in the current literature are still a major challenge.

[0004] Therefore, developing an efficient, low-cost, low-salt consumption and easily scalable method to regulate the phase of molybdenum nitride has important research and application significance. Summary of the invention

[0005] The main purpose of the present invention is to provide a salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method of oxidizing molybdenum to the corresponding Mo x N y The physical phase transformation can be controlled; the method is simple to operate and has universal applicability, and is suitable for large-scale promotion and application.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows: The present invention provides a salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises mixing molybdenum oxide and metal salt in proportion, placing the mixture in a tube furnace, and performing a nitridation reaction under an ammonia atmosphere. The obtained product is cooled, acid-washed, water-washed and dried to obtain Mo x N y Materials; the molar ratio of the molybdenum oxide and the metal salt is 1: (15 ~ 35).

[0007] Preferably, the metal salt includes but is not limited to NaCl, KCl, FeCl 3 6H 2 O、CoCl 2 6H 2 O、NiCl 2 6H 2 One or a combination of O.

[0008] Preferably, the ammonia atmosphere is pure ammonia, nitrogen-ammonia or argon-ammonia mixture, wherein the ammonia content is 5-100%.

[0009] Preferably, the flow rate of the ammonia gas is 20 to 50 sccm.

[0010] Preferably, the nitridation reaction temperature is 550-850°C, the nitridation reaction time is 0.5-2 h, and the heating rate is 5°C / min.

[0011] Preferably, the pickling is performed using a hydrochloric acid solution with a concentration of 0.5-5 mol / L, and the metal salt is fully removed according to the percentage of metal salt added.

[0012] In the above scheme, the drying step adopts freeze drying or air drying oven.

[0013] Preferably, the molybdenum oxide is selected from MoO 3 Nanoribbons or commercial MoO 3 Powder.

[0014] Further preferably, the MoO 3 The method for preparing the nanobelt comprises the following steps: 1) Add metal molybdenum (Mo) powder to a mixed solution of hydrogen peroxide and deionized water, stir in an ice water bath to dissolve the molybdenum powder, and prepare a light yellow solution for later use; 2) The light yellow solution obtained in step 1) was added into a stainless steel autoclave lined with polytetrafluoroethylene for hydrothermal reaction. After the reaction was completed, the reaction solution was cooled to room temperature, and then filtered, washed and dried in sequence to obtain white MoO 3 Nanoribbons.

[0015] In the above scheme, the metal molybdenum powder is in the form of commercially available powder, and its size is 1-50 μm.

[0016] More preferably, the concentration of the light yellow solution in step 1) is 5%-10%.

[0017] More preferably, in step 2), the polytetrafluoroethylene liner is 50-200 mL.

[0018] More preferably, in step 2), the hydrothermal reaction temperature is 160-200° C. and the reaction time is 1-3 days.

[0019] The salt-assisted topological nitridation method proposed in this invention can effectively regulate Mo x N y Phase. MoO nitrided without salt addition 3 Precursor, regulating the nitriding temperature, can only obtain nitrogen-deficient Mo 2 N nanoribbons or Mo 2 N / MoN heterojunction (Mo 2 N is the main phase), and the introduction of alkali metal salts NaCl or KCl can regulate the nitridation to form nitrogen-rich MoN nanobelts or MoN / Mo 2 N heterojunction (MoN as main phase), iron group metal salt FeCl 3 、CoCl 2 or NiCl 2 The addition of promotes nitridation to produce higher nitrogen-rich Mo 5 N 6 Phase. Adjusting the Mo / salt ratio can further optimize the structure and morphology of the product. Low-ratio salt is easy to form Mo 2 N / MoN heterojunction phase, high salt ratio is conducive to the formation of pure phase MoN and Mo 5 N 6 .

[0020] The present invention adopts low-cost KCl and NaCl as salt auxiliary agents, and the obtained nitride has high purity and controllable physical phase; meanwhile, the synthesis process is simple, which is conducive to batch-scale preparation.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention uses MoO 3 Nanobelts are used as precursors, using metal halides NaCl, KCl, FeCl 3 6H 2 O、CoCl 2 6H 2 O、NiCl 2 6H 2 O is an auxiliary agent, which is low in cost and consumes very little salt (only a few grams of salt are consumed per gram of molybdenum oxide). During the entire nitridation process, metal salts can effectively regulate the Mo x N y phase and crystal structure, reduce nitriding temperature, shorten nitriding time, accelerate reaction kinetics and increase Mo x N y The growth rate is reduced, and the salt can be removed by a simple water or acid wash.

[0022] 2) Mo prepared by the present invention x N y The structures are similar, and the one-dimensional morphology is well maintained in pure phase MoN nanobelts and Mo 5 N 6 Nanoribbons and Mo 2 N nanoribbons all show high conductivity, good rate characteristics and high specific capacitance.

[0023] 3) Mo can be precisely controlled by changing the Mo / salt ratio x N y The physical phase of nanobelts is conducive to the formation of pure phase MoN and Mo 5 N 6 .

[0024] 4) The method described in the present invention is universal and can be extended to other molybdenum precursors, such as commercial MoO 3 Powder, MoS 2 Nanosheets, MoO x @Ni-MOF nanoribbons. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A Mo provided in an embodiment of the present invention x N y Nanoribbon preparation process; Figure 2 is a SEM image of MoN in Example 1 of the present invention; Figure 3 TEM image of MoN in Example 1 of the present invention; Figure 4MoN and Mo in Examples 1-2 and Comparative Example 1 of the present invention 2 XRD pattern of N; Figure 5 Mo in Example 3 of the present invention 5 N 6 SEM images of Figure 6 Mo in Example 3 of the present invention 5 N 6 TEM images of Figure 7 The MoN, Mo in Example 1, Comparative Example 1 and Example 3 of the present invention are 2 N and Mo 5 N 6 CV curve of Figure 8 The MoN, Mo in Example 1, Comparative Example 1 and Example 3 of the present invention are 2 N and Mo 5 N 6 GCD curve; Fig. 9 Mo in Example 3 of the present invention 5 N 6 The rate performance; Fig.10 Mo obtained in Examples 3, 5 and 6 of the present invention 5 N 6 XRD pattern of Fig.11 Mo obtained in Example 7, Example 8 and Comparative Example 2 of the present invention x N y XRD pattern of . DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] The purpose of the present invention is to provide a salt-assisted topological nitridation of molybdenum oxide to regulate Mo x N y Phase method. To achieve the oxidation of molybdenum to the corresponding Mo x N y The physical phase transformation can be controlled; the method is simple to operate and has universal applicability, and is suitable for large-scale promotion and application.

[0028] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows: The present invention provides a method for preparing Mo by salt-assisted topological nitridation of molybdenum oxide. x Ny The method comprises mixing molybdenum oxide and metal salt in proportion, placing the mixture in a tube furnace, and performing a nitridation reaction under an ammonia atmosphere. The obtained product is cooled, acid-washed, water-washed and dried to obtain Mo x N y Materials; the molar ratio of the molybdenum oxide and the metal salt is 1: (15 ~ 35).

[0029] The metal salts include but are not limited to NaCl, KCl, FeCl 3 6H 2 O、CoCl 2 6H 2 O、NiCl 2 6H 2 One or a combination of O.

[0030] The ammonia atmosphere is pure ammonia, nitrogen-ammonia or argon-ammonia mixed gas, wherein the ammonia content is 5-100%.

[0031] The flow rate of the ammonia gas is 20-50 sccm.

[0032] The nitridation reaction temperature is 550-850°C, the nitridation reaction time is 0.5-2 h, and the heating rate is 5°C / min.

[0033] The pickling uses a hydrochloric acid solution with a concentration of 0.5-5 mol / L, and the metal salt is fully removed according to the percentage of metal salt added.

[0034] The drying step is carried out by freeze drying or air drying oven.

[0035] The molybdenum oxide is MoO 3 Nanoribbons or commercial MoO 3 Powder.

[0036] The MoO 3 The method for preparing the nanobelt comprises the following steps: 1) Mix metal molybdenum (Mo) powder with a mixed solution of hydrogen peroxide and deionized water, and stir in an ice water bath to dissolve the molybdenum powder to obtain a light yellow solution for later use; 2) The light yellow solution obtained in step 1) is lined with polytetrafluoroethylene and sealed in a stainless steel autoclave, and the autoclave is placed in an electric blast drying oven for hydrothermal treatment. After cooling to room temperature, it is taken out, washed with deionized water and anhydrous ethanol, and dried to obtain white MoO 3 Nanoribbons.

[0037] Example 1 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N yThe method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder (size 1-50 µm) into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) The white MoO obtained in step 2) 3 The nanobelts were mixed evenly with a certain mass of metal salt NaCl according to the molar ratio and transferred to a porcelain boat, wherein the molar ratio of Mo:NaCl was 1:25; 4) placing the porcelain boat containing the obtained mixture in step 3) in a tube furnace, and conducting a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 40 sccm, a nitridation temperature of 650 °C, a nitridation time of 1 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 5) The black powder material obtained in step 4) is washed in a 1 mol / L hydrochloric acid solution and deionized water until the solution is neutral, and then dried in a forced air drying oven for 12 h to obtain a MoN material.

[0038] The specific preparation process diagram of the present invention is as follows Figure 1 shown.

[0039] like Figure 2 As shown, the SEM image shows that the surface pores of the prepared nitrogen-rich δ-MoN nanobelts are very obvious and present a gully shape. Further high-resolution electrical transmission images show that ( Figure 3 ), MoN nanobelts have lattice fringes with a lattice conditional spacing of 0.25 nm, which corresponds to the (110) crystal plane spacing of cubic phase MoN.

[0040] Comparative Example 1 A salt-assisted topological nitridation of molybdenum oxide to regulate Mo x N y The method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) Prepare the white MoO2 in step 2) 3 The nanobelts were placed in a tube furnace and subjected to nitridation reaction in a pure ammonia (99%) atmosphere. The ammonia flow rate was 40 sccm, the nitridation temperature was 650 °C, the nitridation time was 1 h, the heating rate was 5 °C / min, and the nanobelts were taken out after being cooled to room temperature to obtain a black powder material. 4) The black powder material obtained in step 3) was washed in 1 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain Mo 2 N material.

[0041] Example 2 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) The white MoO obtained in step 2) 3 The nanobelts were mixed evenly with a certain mass of metal salt KCl according to the molar ratio and transferred to a porcelain boat, wherein the molar ratio of Mo:KCl was 1:25; 4) placing the porcelain boat containing the obtained mixture in step 3) in a tube furnace, and conducting a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 40 sccm, a nitridation temperature of 650 °C, a nitridation time of 1 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 5) The black powder material obtained in step 4) is washed in a 1 mol / L hydrochloric acid solution and deionized water until the solution is neutral, and then dried in a forced air drying oven for 12 h to obtain a MoN material.

[0042] Compared with the nitrogen-deficient Mo obtained by nitridation without salt addition 2 Compared with the N nanobelts (Comparative Example 1), the introduction of alkali metal salts NaCl (Example 1) and KCl (Example 2) can effectively regulate the MoO 3 The nanobelts are completely nitrided to nitrogen-rich δ-MoN pure phase, and its XRD crystal phase diagram is shown in Figure 4 shown.

[0043] Example 3 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) The white MoO obtained in step 2) 3 Nanobelts and a certain mass of metal salt NiCl 2 6H 2 O are mixed evenly according to the molar ratio and transferred to a porcelain boat, where Mo:NiCl 2 6H 2 The molar ratio of O is 1:35; 4) placing the porcelain boat containing the obtained mixture in step 3) in a tube furnace, and conducting a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 40 sccm, a nitridation temperature of 650 °C, a nitridation time of 1 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 5) The black powder material obtained in step 4) was washed in 5 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain a high nitrogen-rich Mo 5 N 6 Crystal phase materials.

[0044] like Figure 5 As shown, high nitrogen-rich Mo 5 N 6 Although the crystalline material has a one-dimensional nanobelt morphology and the pores on the surface of the nanobelt are also groove-shaped, the nanobelt is easily fragmented and cannot maintain the one-dimensional nanobelt morphology well. Instead, it is composed of many small nanosheets stacked together and has a pore structure on the surface. Figure 6 for Mo 5 N 6 High-resolution transmission electron microscopy image of nanobelts. It can be seen from the image that Mo 5 N 6 The nanoribbons have obvious lattice fringes with a lattice fringing spacing of 0.25 nm, corresponding to the Mo 5 N 6 The (110) crystal plane spacing.

[0045] Figure 7 The pure phase MoN nanobelts, Mo prepared in Example 1, Comparative Example 1 and Example 3 of the present invention 2 N nanoribbons and Mo 5 N 6 The cyclic voltammetry (CV) curve of the nanobelt at a scan rate of 10 mV / s shows that the pure phase MoN nanobelt, Mo 5 N 6 Nanoribbons and Mo 2 The CV curves of MoN nanobelts are very similar, with obvious redox peaks in the range of -0.1 V and 0.3 V, indicating that all three are based on Faraday reaction energy storage and have pseudocapacitive characteristics. 5 N 6 The nanobelts not only have two pairs of obvious peaks with higher peaks, but the pure phase Mo 2 The N electrode only shows a redox peak near -0.1 V and the peak intensity is weak, indicating that the pure phase MoN and Mo 5 N 6 The electrochemical reaction energy storage sites and mass specific capacitance of the electrode are better than those of pure Mo 2N electrode. At the same scan rate and the same active material loading, the mass specific capacitance of the electrode material can be determined based on the area enclosed by the CV curve. Comparing the CV curve areas of the three nanoribbon electrodes, it can be seen that pure phase MoN and Mo 5 N 6 The curve area of ​​the electrode is similar, but significantly larger than that of Mo 2 The CV area of ​​the N electrode shows that the pure phase MoN and Mo 5 N 6 The electrodes have similar mass specific capacitance and higher capacitance than Mo 2 N electrode. The constant current charge and discharge time under different current densities can directly reflect the mass specific capacitance of the electrode material. Figure 8 This is the constant current charge and discharge (GCD) curve at a current density of 0.5 A / g. It can be seen from the figure that pure phase Mo 5 N 6 The charge and discharge time of the electrode is the longest, which is close to that of the pure phase MoN electrode, while the smallest is that of Mo 2 N nanoribbon electrode, indicating pure phase Mo 5 N 6 The specific capacitance of pure phase MoN and Mo is the largest. 5 N 6 and Mo 2 The mass specific capacitances of N are 115.4 F / g, 120.7 F / g, and 103.3 F / g, respectively.

[0046] from Fig. 9 It can be seen intuitively that pure phase Mo under different current densities 5 N 6 Nanoribbons have excellent rate performance.

[0047] Example 4 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) The white MoO obtained in step 2) 3 Nanobelts and a certain mass of metal salt NiCl 2 6H 2 O are mixed evenly according to the molar ratio and transferred to a porcelain boat, where Mo:NiCl 2 6H 2 The molar ratio of O is 1:15; 4) placing the porcelain boat containing the obtained mixture in step 3) in a tube furnace, and performing a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 20 sccm, a nitridation temperature of 850 °C, a nitridation time of 0.5 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 5) The black powder material obtained in step 4) was washed in 0.5 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain a high nitrogen-rich Mo 5 N 6 Crystal phase materials.

[0048] Example 5 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) The white MoO obtained in step 2)3 Nanobelts and a certain mass of metal salt FeCl 3 6H 2 O are mixed evenly according to the molar ratio and transferred to a porcelain boat, where Mo:FeCl 3 6H 2 The molar ratio of O is 1:25; 4) placing the porcelain boat containing the obtained mixture in step 3) in a tube furnace, and performing a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 50 sccm, a nitridation temperature of 650 °C, a nitridation time of 2 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 5) The black powder material obtained in step 4) was washed in 3 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain a high nitrogen-rich Mo 5 N 6 Crystal phase materials.

[0049] Example 6 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps, wherein the molybdenum oxide is MoO prepared in the following steps: 3 Nanoribbons: 1) Slowly add 10 g of molybdenum powder into 50 mL of hydrogen peroxide (H 2 O 2 ) and 110 mL of deionized water in a mixed solution, stirring in an ice-water bath until the solution turns light yellow; 2) Pour the light yellow solution obtained in step 1) into a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and seal it. Place the autoclave in an electric blast drying oven and perform hydrothermal reaction at 180 °C for 2 days. After cooling to room temperature, take out the reactants, vacuum filter them, wash them with deionized water and anhydrous ethanol several times, place them in a vacuum oven, and vacuum dry them at 60 °C for 12 h to obtain white MoO 3 Nanoribbons; 3) The white MoO obtained in step 2) 3 Nanobelts and a certain mass of metal salt CoCl 2 6H 2 O were mixed evenly according to the molar ratio and transferred to a porcelain boat, where Mo:CoCl 2 6H 2 The molar ratio of O is 1:25; 4) placing the porcelain boat containing the obtained mixture in step 3) in a tube furnace, and conducting a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 40 sccm, a nitridation temperature of 550 °C, a nitridation time of 2 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 5) The black powder material obtained in step 4) was washed in 1 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain a high nitrogen-rich Mo 5 N 6 Crystal phase materials.

[0050] The present invention replaces the alkali metal salts NaCl and KCl with iron group metal salts FeCl 3 、CoCl 2 and NiCl 2 When the molybdenum nitride crystal structure is changed, the alkali metal salt NaCl, KCl and the iron metal salt FeCl 3 、CoCl 2 and NiCl 2 It can indeed regulate Mo x N y The crystal structures of different stoichiometric ratios of Mo x N y Products. Figure 5 As shown in the figure, XRD phase analysis shows that alkali metal salts NaCl and KCl effectively promote the formation of MoO 3 Nitriding to nitrogen-deficient δ-MoN crystal structure, while Fig.10 As shown, the iron metal salt FeCl 3 、CoCl 2 and NiCl 2 It is beneficial to nitrogen-rich Mo 5 N 6 Crystal structure formed.

[0051] Example 7 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps: 1) Commercial MoO 3 Powder replaces white MoO 3 The nanobelts were mixed evenly with a certain mass of metal salt NaCl according to the molar ratio and transferred to a porcelain boat, wherein the molar ratio of Mo:NaCl was 1:25; 2) placing the porcelain boat containing the obtained mixture in step 1) in a tube furnace, and performing a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 40 sccm, a nitridation temperature of 650 °C, a nitridation time of 1 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 3) The black powder material obtained in step 2) was washed in 1 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain a MoN material.

[0052] Example 8 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps: 1) Commercial MoO 3 Powder replaces white MoO 3 Nanobelts and a certain mass of metal salt NiCl 2 6H 2 O are mixed evenly according to the molar ratio and transferred to a porcelain boat, where Mo:NiCl 2 6H 2 The molar ratio of O is 1:25; 2) placing the porcelain boat containing the obtained mixture in step 1) in a tube furnace, and performing a nitridation reaction in a pure ammonia (99%) atmosphere, with an ammonia flow rate of 40 sccm, a nitridation temperature of 650 °C, a nitridation time of 1 h, a heating rate of 5 °C / min, and taking out after cooling to room temperature to obtain a black powder material; 3) The black powder material obtained in step 2) was washed in 1 mol / L hydrochloric acid solution and deionized water until the solution was neutral, and then dried in a forced air drying oven for 12 h to obtain a high nitrogen-rich Mo 5 N 6 Crystal phase materials.

[0053] Comparative Example 2 A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method comprises the following steps: Commercial MoO 3 The powder was directly placed in a tube furnace and nitrided in a pure ammonia (99%) atmosphere. The ammonia flow rate was 40 sccm, the nitriding temperature was 650 °C, the nitriding time was 1 h, the heating rate was 5 °C / min, and it was taken out for washing after cooling to room temperature. Only Mo was obtained. 2 N physical phase.

[0054] The present invention is to nitride commercial MoO 3 In powder form, Fig.11It can be seen that when no other salts are introduced, the nitrogenation of commercial MoO 3 Powder can only get Mo 2 After adding NaCl, the signal peaks at 31.9°, 36.2°, 49.0°, 65.1°, 74.3°, 76.8°, 78.3° and 85.6° can be attributed to the (002), (200), (202), (220), (222), (400), (204) and (402) crystal planes of hexagonal δ-MoN (PDF#25-1367), indicating that the introduction of alkali metal salt NaCl can also promote the 3 The powder is nitrided to a pure MoN phase; the alkali metal salt NaCl auxiliary compound is replaced with an iron metal salt NiCl 2 The reaction product also changes from MoN to pure phase Mo 5 N 6 .

[0055] The salt in the present invention regulates Mo x N y The physical phase plays a crucial role. The morphology of the prepared products is consistent with the one-dimensional nanobelt or block shape of the precursor, indicating that the Mo in the present invention x N y The preparation of nanoribbons is a topological transformation process. When the molybdenum source is replaced by commercial MoO 3 Powder, nitridation product Mo 2 N nanoribbons, MoS 2 and MoO 3 @Ni-MOF and other different precursors, salt can still regulate Mo x N y This shows that the salt-assisted phase regulation method we designed is universal. In the nitridation process, salt can not only regulate the Mo x N y phase and crystal structure, and can significantly increase the formation energy of molybdenum nitride, reduce the nitriding temperature and shorten the nitriding time to promote Mo x N y The corresponding product can usually be obtained by nitriding at a low temperature of 650 °C for 1 h.

[0056] The above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here, so the obvious changes or modifications derived are still within the protection scope of the invention.

Claims

1. A salt-assisted topological nitridation of molybdenum oxide to prepare Mo x N y The method is characterized in that Molybdenum oxide and metal salt are mixed in proportion and placed in a tube furnace for nitridation reaction under an ammonia atmosphere. The obtained product is cooled, acid-washed, water-washed and dried to obtain Mo x N y Materials; the molar ratio of the molybdenum oxide and the metal salt is 1: (15 ~ 35).

2. The method for preparing Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 1 x N y The method is characterized in that The metal salt includes but is not limited to one or a combination of NaCl, KCl, FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O.

3. The method for preparing Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 1 x N y The method is characterized in that The ammonia atmosphere is pure ammonia, nitrogen-ammonia or argon-ammonia mixed gas, wherein the ammonia content is 5-100%.

4. Preparation of Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 1 x N y The method is characterized in that The flow rate of the ammonia gas is 20-50 sccm.

5. Preparation of Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 1 x N y The method is characterized in that The nitridation reaction temperature is 550-850°C, the nitridation reaction time is 0.5-2 h, and the heating rate is 5°C / min.

6. Preparation of Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 1 x N y The method is characterized in that The pickling is performed using a hydrochloric acid solution with a concentration of 0.5-5 mol / L.

7. The method for preparing Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 1 x N y The method is characterized in that The molybdenum oxide is selected from MoO3 nanobelts or commercial MoO3 powder; preferably, the preparation method of the MoO3 nanobelts comprises the following steps: 1) Add metallic molybdenum powder to a mixed solution of hydrogen peroxide and deionized water, stir in an ice water bath to dissolve the molybdenum powder, and prepare a light yellow solution for later use; 2) The light yellow solution obtained in step 1) is added into a stainless steel high-pressure reactor lined with polytetrafluoroethylene to carry out a hydrothermal reaction. After the reaction is completed, the reaction solution is cooled to room temperature, and then filtered, washed, and dried in sequence to obtain white MoO3 nanobelts.

8. The method for preparing Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 7 x N y The method is characterized in that The concentration of the light yellow solution in step 1) is 5%-10%.

9. Preparation of Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 7 x N y The method is characterized in that In the step 2), the polytetrafluoroethylene liner is 50-200 mL.

10. Preparation of Mo by salt-assisted topological nitridation of molybdenum oxide according to claim 7 x N y The method is characterized in that In the step 2), the hydrothermal reaction temperature is 160-200° C. and the reaction time is 1-3 days.

Images