Manganese oxide / cerium oxide amorphous multi-bubble nanotube and preparation method and application thereof
Amorphous multi-bubble nanotubes of manganese oxide/cerium oxide were prepared by electrospinning, which solved the problem of low catalytic activity of electrocatalytic ammonia synthesis catalysts at room temperature and pressure, and achieved high ammonia yield and Faraday efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2023-02-16
- Publication Date
- 2026-07-21
AI Technical Summary
Existing catalysts for electrocatalytic ammonia synthesis have low catalytic activity, yield, and Faraday efficiency at room temperature and pressure.
Amorphous multi-bubble nanotubes of manganese oxide/cerium oxide were prepared by electrospinning. By controlling the formation of a one-dimensional linear structure in the sample, a composite multi-bubble nanotube structure was formed by confined reaction and high-temperature calcination. This structure was then used as an electrocatalyst for the electrocatalytic conversion of nitrogen into ammonia.
Excellent ammonia yield and Faraday efficiency were achieved at room temperature and pressure, thus improving the electrocatalytic performance of the catalyst.
Smart Images
Figure CN116121806B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrocatalysis of energy storage materials, specifically relating to a manganese oxide / cerium oxide amorphous multi-bubble nanotube, its preparation method and application. Background Technology
[0002] Ammonia (NH3) is not only an important carrier of carbon-free energy storage and transport in living organisms, but also a basic chemical raw material for fertilizer production. Since the beginning of the 21st century, the rapid growth of the world's population and the urgent need for food have driven the rapid development of ammonia synthesis technology. Currently, global ammonia production is approximately 200 million tons per year; however, the main industrial ammonia synthesis method remains the traditional Haber-Bosch catalytic process. This method utilizes nitrogen and hydrogen as raw materials to directly synthesize ammonia under high temperature, high pressure, and the presence of an iron-based catalyst, and is considered one of the most significant discoveries of the last century. Furthermore, after more than 100 years of development, the current Haber-Bosch catalytic ammonia synthesis process can control the temperature to around 450℃, and the pressure has been reduced from the original 100 MPa to below 30 MPa. However, the conversion efficiency of this method is still very low, only 10-15%, and the reaction conditions and operating procedures remain very demanding, requiring not only robust reaction vessels but also real-time removal of the product ammonia to drive the reaction forward. In addition, this process inevitably contributes to approximately 1.6% of global CO2 greenhouse gas emissions. Therefore, novel green and sustainable ammonia synthesis methods have become a research hotspot.
[0003] Electrocatalytic ammonia synthesis, as an emerging synthetic method in recent years, boasts significant advantages and characteristics such as being green, having mild reaction conditions, and being highly efficient. Compared to the traditional Haber-Bosch process, the electrocatalytic method reduces energy consumption by using renewable secondary energy, electricity, and allows for the identification of the optimal test potential through testing, thus improving energy utilization. Furthermore, the electrocatalytic ammonia synthesis reaction is carried out under ambient temperature and pressure conditions, and the testing equipment is relatively simple to set up. Therefore, the electrocatalytic ammonia synthesis method holds promise for large-scale application. However, current catalysts used for electrocatalytic ammonia synthesis generally suffer from low catalytic activity, low yield, and low Faradaic efficiency under ambient temperature and pressure. Therefore, developing a catalyst that can efficiently catalyze the synthesis of ammonia from nitrogen at ambient temperature and pressure is particularly necessary. Summary of the Invention
[0004] The purpose of this invention is to solve the technical problems of low catalytic activity, low yield and low Faraday efficiency of existing catalysts used for electrocatalytic ammonia synthesis at room temperature and pressure, and to provide a manganese oxide / cerium oxide amorphous multi-bubble nanotube, its preparation method and application.
[0005] One objective of this invention is to provide a method for preparing amorphous multi-bubble nanotubes of manganese oxide / cerium oxide, the method comprising the following steps:
[0006] S1: Mix the cerium source, carbon source and organic solvent, then add a co-solvent and stir until completely dissolved to obtain solution A;
[0007] S2: Add manganese source and organic solvent to solution A, mix well, add binder dropwise, and stir continuously at room temperature for 12 hours to obtain precursor solution;
[0008] S3: The precursor solution is electrospun into fibers and then calcined in air to obtain amorphous polybubbly nanotubes of manganese oxide / cerium oxide.
[0009] Further specifying, the cerium source in S1 includes cerium nitrate hexahydrate and / or cerium carbonate.
[0010] Further specifying, the carbon source in S1 is anhydrous citric acid.
[0011] Further specifying, the organic solvent in S1 is DMF (N,N-dimethylformamide) or DMA (N,N-dimethylacetamide).
[0012] Further specifying, the co-solvent in S1 is acetic acid or nitric acid.
[0013] Further specifying, the mass ratio of cerium source to carbon source in S1 is (0.6~1.0):1.
[0014] Further specifying, the volume ratio of organic solvent to co-solvent in S1 is (5-9):1
[0015] Further specifying, the manganese source in S2 includes manganese nitrate hexahydrate and / or manganese carbonate.
[0016] Further specifying, the organic solvent in S2 is anhydrous ethanol.
[0017] Further specifying, the binder in S2 is PVP (polyvinylpyrrolidone).
[0018] Further specifying, the molar ratio of manganese source in S2 to cerium source in S1 is (1.5~2.2):1.
[0019] Further specified, the ratio of the total amount of organic solvent in S1 and organic solvent in S2 to the binder is (10-15) mL: 1 g.
[0020] Further specified, the inner diameter of the electrospinning syringe needle in S3 is 0.5–5 mm.
[0021] Further specifying the electrospinning parameters in S3, the positive voltage at the needle tip is 15–20 kV, the distance between the needle tip and the current collector is 15–20 cm, and the injection rate is 0.4–0.6 mL·h. -1 The humidity is 25-30% RH.
[0022] Further specifying, the calcination process in S3 is: at 1-2℃ for min... -1 Heat the temperature at a rate of 500–700℃ and hold for 30–60 minutes.
[0023] The second objective of this invention is to provide a manganese oxide / cerium oxide amorphous multi-bubble nanotube prepared by the above method, which is a composite of amorphous amorphous phase Mn2O3 and amorphous amorphous phase CeO2.
[0024] Further specifying, the manganese oxide / cerium oxide amorphous multi-bubble nanotubes are one-dimensional multi-bubble nanotubes with loose bubbles in the tube wall.
[0025] The third objective of this invention is to provide an application of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared by the above method in the electrocatalytic reduction of nitrogen to ammonia.
[0026] A fourth objective of this invention is to provide a nitrogen-fixing catalyst comprising amorphous polybubbly nanotubes of manganese oxide / cerium oxide prepared by the method described above.
[0027] The significant advantages of this invention compared to existing technologies are:
[0028] (1) This invention uses electrospinning to synthesize filamentous polymer precursors to control the formation of a one-dimensional linear structure in the sample, effectively avoiding the independent nucleation of manganese and cerium ions during subsequent sintering. Utilizing a confined reaction, high-temperature calcination first decomposes the outer polymer and salt, forming a stable outer shell. Subsequently, the internal fibers shrink due to the decomposition of the polymer and salt, and upon reaching a certain degree, the outer shell is repeatedly formed. Simultaneously, bubbles are formed in the tube wall through the decomposition of the polymer and salt, constructing a multi-bubble nanotube structure composed of cerium oxide and manganese oxide. The confined space, the thermal decomposition of the polymer and salt, and the inductive effect of cerium oxide play a decisive role in the structure, morphology, and properties of the amorphous cerium oxide / manganese oxide multi-bubble nanotube composite, demonstrating a synergistic mechanism and forming an organic unity.
[0029] (2) The method provided by the present invention can synthesize amorphous multi-bubble nanotubes of manganese oxide / cerium oxide with excellent electrocatalytic nitrogen reduction performance. When used as a catalyst in the electrocatalytic conversion of nitrogen to ammonia, it has excellent ammonia yield and Faraday efficiency. Attached Figure Description
[0030] Figure 1aSEM image of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared in Example 1;
[0031] Figure 1b for Figure 1a Enlarged image;
[0032] Figure 2 The image shows the structural characterization of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared in Example 1; where a is the XRD pattern, bd is the HRTEM image, e is the auto-correlation image and FFT of the corresponding region, f is the SAED spectrum, and gj is the EDS surface scan image.
[0033] Figure 3 ad are TEM images of different locations of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared in Example 1;
[0034] Figure 4a Yield curves of manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared in Example 1 as catalysts at different voltages;
[0035] Figure 4b The Faraday efficiency diagram of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared in Example 1 as catalysts at different voltages. Detailed Implementation
[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.
[0038] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.
[0039] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.
[0040] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.
[0041] Example 1:
[0042] The preparation method of manganese oxide / cerium oxide amorphous multi-bubble nanotubes in this embodiment is carried out according to the following steps:
[0043] S1: Mix 0.5 mmol Ce(NO3)3·6H2O, 0.25 g anhydrous citric acid and 8 mL LDMF (N,N-dimethylformamide), then add 1 mL acetic acid and stir magnetically at room temperature until completely dissolved to obtain solution A;
[0044] S2: Add 1 mmol Mn(NO3)2·H2O and 4 mL anhydrous ethanol to solution A, mix well, and then add 1.1 g PVP (Mw≈1300000) dropwise. Stir continuously at room temperature for 12 h to obtain the precursor solution.
[0045] S3: The precursor solution was transferred to a syringe with an inner diameter of 0.5 mm, electrospun into fibers, and then calcined in air. The electrospinning parameters were: positive voltage at the needle tip of 16 kV, distance between the needle tip and the current collector of 16 cm, and injection rate of 0.4 mL / h. -1 The humidity was 25% RH, and the calcination process was as follows: at 1℃ min -1 The temperature was increased to 550℃ and then held at 550℃ for 30 min to obtain a composite of amorphous Mn2O3 and amorphous CeO2, namely manganese oxide / cerium oxide amorphous multi-bubble nanotubes.
[0046] Morphological and structural characterization:
[0047] Figure 1a -b is the SEM image of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes obtained in Example 1. As can be seen from Figure 1, the manganese oxide / cerium oxide composite material exhibits a one-dimensional nanotube structure.
[0048] Figure 2 a is the XRD pattern of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes obtained in Example 1. Figure 2 As can be seen, Mn₂O₃ has no obvious diffraction peaks, and CeO₂ has poor crystallinity, belonging to amorphous CeO₂ and amorphous Mn₂O₃. Figure 2 c and 2d high-resolution transmission electron microscopy (HRTEM) also show that the sample is mostly amorphous. Similarly, from the corresponding fast Fourier transform (FFT) analysis in 2e, strong diffraction points and negligible diffraction rings were observed, which are typical characteristics of amorphous samples. Figure 2 Selected area electron diffraction (SAED) of f also confirmed the poor crystallinity of the sample. This observation is consistent with the XRD characterization results.
[0049] Figure 3 This is a TEM image of the amorphous polybubble nanotubes of manganese oxide / cerium oxide obtained in Example 1. Figure 3 As can be seen, the nanotubes exhibit a loose, multi-bubble structure.
[0050] Electrocatalytic performance test:
[0051] The testing process is as follows:
[0052] First, 1 mg of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes obtained in Example 1 was added to a 2 mL centrifuge tube. 190 μL of anhydrous ethanol was then added to the centrifuge tube and ultrasonically dispersed in an ice-water bath for 30 min. Then, 10 μL of Nafion (all-sulfonic acid resin) reagent was added to the centrifuge tube and ultrasonically dispersed in an ice-water bath for another 30 min until an ink-like slurry was formed. 20 μL of Nafion was then evenly coated onto a 1 cm * 1 cm hydrophilic carbon paper and dried at room temperature for 12 h.
[0053] The prepared carbon paper was then fixed in the electrode holder as the working electrode, 0.1 mol / L sodium sulfate solution was used as the electrolyte, platinum electrode was used as the counter electrode, and silver / silver chloride electrode was used as the reference electrode. An H-type electrolytic cell was used, and the current-time (it) test was performed at different voltages using an electrochemical workstation (CHI760E).
[0054] The calculated results are shown in Figure 4. As can be seen from Figure 4, the manganese oxide / cerium oxide amorphous multi-bubble nanotubes of Example 1 of this invention exhibit excellent catalytic performance as an electrocatalytic catalyst for nitrogen reduction to ammonia. Under an applied voltage of -0.2V vs RHE, it achieves a yield of 61.12 μg mg / kg. -1 h -1 The ammonia yield and Faraday efficiency were 45.25%.
[0055] Example 2
[0056] The preparation method of manganese oxide / cerium oxide amorphous multi-bubble nanotubes in this embodiment is carried out according to the following steps:
[0057] S1: Mix 0.5 mmol Ce2(CO3)3·H2O, 0.25 g anhydrous citric acid and 8 mL LDMF (N,N-dimethylformamide), then add 1 mL acetic acid and stir magnetically at room temperature until completely dissolved to obtain solution A;
[0058] S2: Add 1.0 mmol MnCO3 and 4 mL anhydrous ethanol to solution A, mix well, and then add 1.1 g PVP (Mw≈1300000) dropwise. Stir continuously at room temperature for 12 h to obtain the precursor solution.
[0059] S3: The precursor solution was transferred to a syringe with an inner diameter of 0.5 mm, electrospun into fibers, and then calcined in air. The electrospinning parameters were: positive voltage at the needle tip of 16 kV, distance between the needle tip and the current collector of 16 cm, and injection rate of 0.4 mL / h. -1 The humidity was 25% RH, and the calcination process was as follows: at 1℃ min -1 The temperature was increased to 550℃ and then held at 550℃ for 30 min to obtain a composite of amorphous Mn2O3 and amorphous CeO2, namely manganese oxide / cerium oxide amorphous multi-bubble nanotubes.
[0060] Example 3
[0061] The preparation method of manganese oxide / cerium oxide amorphous multi-bubble nanotubes in this embodiment is carried out according to the following steps:
[0062] S1: Mix 0.5 mmol Ce(NO3)3·6H2O, 0.25 g anhydrous citric acid and 8 mL DMA (N,N-dimethylacetamide), then add 1 mL nitric acid and stir magnetically at room temperature until completely dissolved to obtain solution A;
[0063] S2: Add 1.0 mmol Mn(NO3)2·H2O and 4 mL anhydrous ethanol to solution A, mix well, and then add 1.1 g PVP (Mw≈1300000) dropwise. Stir continuously at room temperature for 12 h to obtain the precursor solution.
[0064] S3: The precursor solution was transferred to a syringe with an inner diameter of 0.5 mm, electrospun into fibers, and then calcined in air. The electrospinning parameters were: positive voltage at the needle tip of 16 kV, distance between the needle tip and the current collector of 16 cm, and injection rate of 0.4 mL / h. -1 The humidity was 25% RH, and the calcination process was as follows: at 1℃ min -1 The temperature was increased to 550℃ and then held at 550℃ for 30 min to obtain a composite of amorphous Mn2O3 and amorphous CeO2, namely manganese oxide / cerium oxide amorphous multi-bubble nanotubes.
[0065] Example 4
[0066] The preparation method of manganese oxide / cerium oxide amorphous multi-bubble nanotubes in this embodiment is carried out according to the following steps:
[0067] S1: Mix 0.5 mmol Ce(NO3)3·6H2O, 0.25 g anhydrous citric acid and 8 mL LDMF (N,N-dimethylformamide), then add 1 mL acetic acid and stir magnetically at room temperature until completely dissolved to obtain solution A;
[0068] S2: Add 1.0 mmol Mn(NO3)2·H2O and 4 mL anhydrous ethanol to solution A, mix well, and then add 1.1 g PVP (Mw≈1300000) dropwise. Stir continuously at room temperature for 12 h to obtain the precursor solution.
[0069] S3: The precursor solution is transferred to a syringe with an inner diameter of 0.5 mm, electrospun into fibers, and then calcined in air. The electrospinning parameters are: positive voltage at the needle tip of 20 kV, distance between the needle tip and the current collector of 20 cm, and injection rate of 0.6 mL / h. -1 The humidity is 30% RH, and the calcination process is as follows: at 1℃ min -1 The temperature was increased to 550℃ and then held at 550℃ for 30 min to obtain a composite of amorphous Mn2O3 and amorphous CeO2, namely manganese oxide / cerium oxide amorphous multi-bubble nanotubes.
[0070] Example 5
[0071] The preparation method of manganese oxide / cerium oxide amorphous multi-bubble nanotubes in this embodiment is carried out according to the following steps:
[0072] S1: Mix 0.5 mmol Ce(NO3)3·6H2O, 0.25 g anhydrous citric acid and 8 mL LDMF (N,N-dimethylformamide), then add 1 mL acetic acid and stir magnetically at room temperature until completely dissolved to obtain solution A;
[0073] S2: Add 1.0 mmol Mn(NO3)2·H2O and 4 mL anhydrous ethanol to solution A, mix well, and then add 1.1 g PVP (Mw≈1300000) dropwise. Stir continuously at room temperature for 12 h to obtain the precursor solution.
[0074] S3: The precursor solution was transferred to a syringe with an inner diameter of 0.5 mm, electrospun into fibers, and then calcined in air. The electrospinning parameters were: positive voltage at the needle tip of 16 kV, distance between the needle tip and the current collector of 16 cm, and injection rate of 0.4 mL / h. -1 The humidity was 25% RH, and the calcination process was as follows: at 2℃ for 1 minute -1 The temperature was increased to 700℃ and then held at 700℃ for 30 min to obtain a composite of amorphous Mn2O3 and amorphous CeO2, namely manganese oxide / cerium oxide amorphous multi-bubble nanotubes.
[0075] The manganese oxide / cerium oxide amorphous multi-bubble nanotubes obtained in Examples 2-5 were observed by SEM, TEM and XRD. The results showed that the obtained materials were all amorphous, multi-bubble nanotube structures.
[0076] The electrocatalytic performance of manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared in Examples 2-5 was tested according to the electrocatalytic performance testing method used in Example 1. The results show that the manganese oxide / cerium oxide amorphous multi-bubble nanotube catalyst of the present invention exhibits excellent electrocatalytic performance, achieving an ammonia yield as high as 60 ± 5 μgh under an applied voltage of -0.2 V vs RHE. -1 mg cat -1 And its excellent Faraday efficiency is approximately 45±5%.
[0077] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing amorphous multi-bubble nanotubes of manganese oxide / cerium oxide, characterized in that, This method is performed in the following steps: S1: Mix the cerium source, carbon source and organic solvent, then add a co-solvent and stir until completely dissolved to obtain solution A; S2: Add manganese source and organic solvent to solution A, mix well, add binder dropwise, and stir continuously at room temperature for 12 hours to obtain precursor solution; S3: The precursor solution was electrospun into fibers and then calcined in air to obtain manganese oxide / cerium oxide amorphous multi-bubble nanotubes. The carbon source in S1 is anhydrous citric acid, and the mass ratio of cerium source to carbon source is (0.6~1.0):1; The binder in S2 is PVP, the molar ratio of manganese source in S2 to cerium source in S1 is (1.5~2.2):1, and the ratio of total organic solvent to binder in S1-2 is (10~15) mL:1 g. The calcination process in S3 is as follows: at 1~2℃ min... -1 Heat the temperature to 500~700℃ at a rapid rate and hold for 30~60 min; Manganese oxide / cerium oxide amorphous multi-bubble nanotubes are a composite of amorphous amorphous phase Mn2O3 and amorphous amorphous phase CeO2, and are one-dimensional multi-bubble nanotubes with loose bubbles in the tube wall.
2. The method according to claim 1, characterized in that, The cerium source in S1 includes cerium nitrate hexahydrate and / or cerium carbonate, the organic solvent is DMF or DMA, the co-solvent is acetic acid or nitric acid, and the volume ratio of organic solvent to co-solvent is (5~9):
1.
3. The method according to claim 1, characterized in that, The manganese source in S2 includes manganese nitrate hexahydrate and / or manganese carbonate, and the organic solvent is anhydrous ethanol.
4. The method according to claim 1, characterized in that, The inner diameter of the needle in the S3 electrospinning injector is 0.5~5 mm.
5. The method according to claim 1, characterized in that, The electrospinning parameters in S3 are as follows: positive voltage at the needle tip is 15~20 kV, distance between the needle tip and the current collector is 15~20 cm, and injection rate is 0.4~0.6 mL. h -1 The humidity is 25~30% RH.
6. The manganese oxide / cerium oxide amorphous polybubble nanotubes prepared by the method according to any one of claims 1-5, characterized in that, It is a complex of amorphous Mn2O3 and amorphous CeO2.
7. The application of the manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared by the method of any one of claims 1-5 in the electrocatalytic reduction of nitrogen to ammonia.
8. A nitrogen-fixing catalyst, characterized in that, It includes manganese oxide / cerium oxide amorphous multi-bubble nanotubes prepared by the method of any one of claims 1-5.