A gd-nc material, a preparation method and application thereof

Abstract

The application discloses a kind of Gd-NC materials, the material is metal atom and N doped carbon material, the metal atom at least includes Gd.The material of the application, with rare earth metal Gd as active center, the selection of oxygen reduction catalyst is widened;And with excellent conductivity, high specific surface area, surface defect is more, and the advantages such as good hydrophilicity.Compared with commercial Pt / C, the prepared catalyst has more correct half-wave potential and better stability, can be applied in metal-air battery, fuel cell and other electrochemical new clean energy equipment, has important significance.In addition, the material of the application performs excellently in low-frequency wave-absorbing field, and can also add more choices for the development of wave-absorbing material.The preparation steps of the material of the application are simple, and raw material is low in price, preparation method is simple, and can be mass-produced.

Description

Technical Field

[0001] This invention relates to the fields of electrochemical catalysts and electromagnetic wave absorption technology, and particularly to a Gd-NC material, its preparation method, and its applications. Background Technology

[0002] To alleviate the pressure of traditional energy demand, developing renewable and sustainable energy sources to replace them is urgently needed. Renewable electrochemical energy conversion and storage systems (such as metal-air batteries, fuel cells, and water splitting devices) are among the most promising technologies for addressing energy and environmental challenges. The oxygen reduction reaction (ORR), as one of the core reactions in various renewable energy storage and conversion devices, currently relies heavily on the catalytic action of precious metals for commercialization due to its slow kinetics, severely hindering the development and effective utilization of these new clean energy sources.

[0003] Pt and nanocomposites are generally considered the most effective commercial ORR catalysts, but they still suffer from serious economic and performance problems, such as scarcity, high cost, poor durability, cross-effects, and methanol poisoning. To address these issues with precious metals, current research on ORR catalysts is increasingly shifting towards single-atom MNC catalysts with transition metal elements (Fe, Co, Mn, Zn, Cu, etc.) as active centers. Among the various MNC catalysts discovered so far, Fe-NC catalysts with Fe as the active center are considered the most promising alternative to Pt-based catalysts due to their high ORR activity. However, to date, non-precious SAC (single-atom catalysts) with platinum-competitive ORR activity are still limited to a few transition metal elements.

[0004] Furthermore, with the rapid development of electronic devices and wireless communications, people are increasingly concerned about serious electromagnetic pollution and radiation problems. Electromagnetic pollution and radiation not only interfere with electronic devices but also harm the environment and human health. Currently, the solution to these problems mainly relies on the reflection and absorption of electromagnetic waves. Microwave absorption is highly efficient and can completely suppress the propagation, reflection, and re-polluting of electromagnetic waves. In recent years, extensive research has been conducted both domestically and internationally on electromagnetic absorbing materials, aiming to develop electromagnetic absorbing materials with strong absorption capacity, wide absorption bandwidth, thin absorber thickness, and light weight. Carbon-based materials can achieve synergistic effects of multiple loss mechanisms through magnetic nanoparticle modification and / or the construction of different microstructures, thereby obtaining better interfacial impedance matching and a stronger attenuation coefficient, thus improving wave absorption performance. Based on this viewpoint, rare earth-based single atoms or atomic active sites may be the most effective sites for microwave absorption. However, there are currently no studies characterizing the microwave absorption of rare earth element single-atom materials. Therefore, developing rare earth atomic microwave absorbing materials can broaden its selection and is of great significance for the development of microwave absorbing materials.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a Gd-NC material for oxygen reduction catalysis, overcoming the shortcomings of existing oxygen reduction catalysts such as high raw material cost and complex catalyst preparation. This oxygen reduction catalyst also possesses advantages such as excellent conductivity, high surface area, numerous surface defects, and good hydrophilicity. Furthermore, this material exhibits excellent absorption performance in the low-frequency electromagnetic wave domain, broadening the selection of absorbing materials for future development.

[0007] Another object of the present invention is to provide a method for preparing the Gd-NC material, and also to provide its use in the fields of catalysis and microwave absorption.

[0008] To achieve the above objectives, the present invention provides

[0009] A Gd-NC material, characterized in that the material is a carbon material doped with metal atoms and N, wherein the metal atoms include at least Gd.

[0010] Preferably, in the above technical solution, the material has a particle size of 700-800 μm. 2 g -1 The specific surface area is large; it has a self-supporting three-dimensional structure and is in the form of graphene sheets; the elemental content percentage of Gd:N:C in the oxygen reduction catalyst is 1-5:1-10:80-95.

[0011] Preferably, in the above technical solution, the metal atoms in the material further include one or more of Fe, Co, and Mn.

[0012] A method for preparing the above-mentioned material includes the following:

[0013] (1) Add N-containing carbon precursor and metal salt to a ball milling jar containing template agent and ball mill complex to form a complex with metal ion coordination.

[0014] (2) The complex is dried, thermally decomposed under the protection of an inert gas, then rinsed, dried, and then thermally decomposed again to obtain metal atom-NC material.

[0015] Preferably, in the above technical solution, the metal salt is a Gd salt, and more preferably, the Gd salt is gadolinium chloride hexahydrate; the molar ratio of Gd salt to the carbon precursor of N is 1-2:1-3.

[0016] Preferably, in the above technical solution, the metal salt is one or more of Fe, Co, and Mn salts, preferably Fe salt, and the Fe salt is ferrous chloride tetrahydrate; after rinsing in step (2), the sample is centrifuged to obtain the sample; an ethanol solution containing Gd salt is added to the sample, and the sample is ultrasonically stirred until the ethanol is completely evaporated, and then a second thermal pyrolysis is performed to obtain the multi-metal atom-NC catalyst.

[0017] Preferably, in the above technical solution, the molar ratio of one or more of the N-containing carbon precursors: Fe, Co, and Mn salts to Gd salt is 1:2-4:0.5-1.

[0018] Preferably, in the above technical solution, the N-containing carbon precursor is 2,6-diaminopyridine; and / or the template agent is sodium chloride.

[0019] Preferably, in the above technical solution, the ball milling time is 12-24 hours and the ball milling speed is 450-600 r / min;

[0020] Preferably, in the above technical solution, the complex is dried at 70-90℃ for 8-10 hours; the thermal pyrolysis reaction conditions are thermal pyrolysis at 800-950℃ for 1-2 hours.

[0021] Preferably, in the above technical solution, rinsing includes immersing the pyrolyzed material in H2SO4 solution at 80℃-100℃ for 8-12 hours, filtering and washing with water multiple times until the filtrate is neutral, and drying the filtered sample under vacuum conditions for 5-10 hours at a drying temperature of 60-100℃.

[0022] The material is used for electrochemical oxygen reduction catalysis and electromagnetic wave absorption.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The novel material of this invention uses rare earth metal Gd as the active center, which is the first discovery in the research of oxygen reduction catalysts, thus broadening the selection of oxygen reduction catalysts; it also has the advantages of excellent conductivity, high specific surface area, many surface defects, and good hydrophilicity. Compared with commercial Pt / C, the prepared catalyst has a more positive half-wave potential and better stability, and can be applied in new electrochemical clean energy devices such as metal-air batteries and fuel cells, which is of great significance.

[0025] (2) The preparation steps of the material of the present invention are simple, the raw materials are inexpensive, the preparation method is simple, and it can be produced on a large scale.

[0026] (3) The catalyst of the present invention can be widely used in the field of electrochemical oxygen reduction materials, as well as for absorbing electromagnetic waves. Attached Figure Description

[0027] Figure 1 XRD patterns of Gd-NC materials;

[0028] Figure 2 SEM images of Gd-NC materials;

[0029] Figure 3 HAADF STEM and EELS energy spectra of Gd-NC materials;

[0030] Figure 4 Nitrogen adsorption / desorption isotherms of Gd-NC materials;

[0031] Figure 5 ORR polarization curves of Gd-NC materials with different proportions in 1.0 MkOH electrolyte in Examples 1-4;

[0032] Figure 6 ORR polarization curves of Fe-Gd diatomic materials in 1.0 MkOH electrolyte.

[0033] Figure 7 Electron transfer number and hydrogen peroxide yield of Fe-Gd diatomic materials in 1.0 MkOH electrolyte;

[0034] Figure 8 ORR polarization curves of Fe-Gd diatomic materials in 0.5M H2SO4 electrolyte;

[0035] Figure 9 Electron transfer number and hydrogen peroxide yield of Fe-Gd diatomic materials in 0.5M H2SO4 electrolyte;

[0036] Figure 10 Example 1: Microwave absorption performance of Gd-NC material absorbing powder.

[0037] Table 1. XPS elemental content test results of Gd-NC materials with different proportions in Examples 1-4. Detailed Implementation

[0038] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0039] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0040] Example 1

[0041] In this embodiment, 2,6-diaminopyridine (DMP) was used as the N and C source precursor, and gadolinium chloride hexahydrate was used as the metal salt (Gd metal source) to prepare a new gadolinium-based nitrogen-carbon material.

[0042] In this example, 2,6-diaminopyridine (DMP) was used as the precursor to prepare the sample. The metal salt used was gadolinium chloride hexahydrate (GdCl3·6H2O). 3+ The molar ratio of the drug to DMP was 1:2, with a fixed amount of DMP (2 mmol / L, 0.4366 g). Different proportions of the drug were added to an agate ball mill jar, mixed with 20 g of NaCl and 18 ml of ethanol, and milled for 18 h at a mill speed of 500 r / min. The milled samples were then dried in an 80 °C air oven and placed in a tube furnace for pyrolysis at 850 °C in a N2 atmosphere for 2 h, with a heating rate of 5 °C / min. -1 The pyrolysis sample was acid-washed in 0.5 M H₂SO₄ at 80 °C for 12 h, then filtered and washed multiple times with ultrapure water until neutral. Finally, it was centrifuged with ethanol and dried in a vacuum oven at 80 °C for 8 h. The dried sample was then pyrolyzed again at 850 °C in a N₂ atmosphere for 1 h to obtain the Gd-NC catalyst. The samples were labeled as Gd₁N₂C according to different proportions.

[0043] Example 2

[0044] The difference between this implementation and Example 1 lies in the ratio of added Gd salt to DMP. Sample Gd 3+ The molar ratio of DMP to Gd1N1C is 1:1.

[0045] Example 3

[0046] The difference between this implementation and Example 1 lies in the ratio of added Gd salt to DMP. Sample Gd 3+ The molar ratio of DMP to Gd1N3C is 1:3.

[0047] Example 4

[0048] The difference between this implementation and Example 1 lies in the ratio of added Gd salt to DMP. Sample Gd 3+ The molar ratio of Gd2N1C to DMP is 2:1.

[0049] Example 5

[0050] This example uses Fe-NC catalyst as a basis, introducing Gd to form a Fe-Gd-NC bimetallic atom catalyst. In this embodiment, 2,6-diaminopyridine (DMP) is used as the N and C source precursors, and gadolinium chloride hexahydrate (Gd metal source) and ferrous chloride tetrahydrate (Fe metal source) are used as metal salts to prepare novel iron-gadolinium-based bimetallic atom nitrogen-carbon materials.

[0051] The specific preparation method is as follows: 0.6548 g DMP and 2.3858 g FeCl2·4H2O were added to an agate ball mill jar, mixed with 20 g NaCl and 18 ml ethanol, and ball-milled for 12 h. The ball-milled sample was then dried in an 80 °C air oven and thermally pyrolyzed in a tube furnace at 850 °C in a N2 atmosphere for 2 h. The pyrolyzed sample was acid-washed in 0.5 M H2SO4 at 80 °C for 12 h, then filtered, washed multiple times with ultrapure water until neutral, and finally centrifuged with ethanol. The prepared catalyst was divided into two portions. One portion was added to an ethanol solution containing 20 mg GdCl3·6H2O and ultrasonically stirred in a water bath at room temperature until the ethanol was completely evaporated. Both samples were then thermally pyrolyzed again at 850 °C in a N2 atmosphere for 1 h to obtain the Fe-NC catalyst and the Fe-Gd-NC catalyst.

[0052] The oxygen reduction catalysts prepared in Examples 1-5 were characterized and analyzed.

[0053] X-ray diffraction patterns (XRD) were acquired using an X-ray diffractometer.

[0054] The morphology and microstructure of the catalyst samples were characterized using scanning electron microscopy (SEM) and high-angle annular dark-field imaging scanning transmission electron microscopy (HAADF-STEM), respectively.

[0055] Electron energy loss spectroscopy (EELS) was used to detect the elemental composition and chemical environment of the catalyst.

[0056] The oxygen reduction performance of the catalyst was tested using cyclic voltammetry (CV) and two-electrode voltammetry (DECV). CV activation was performed in the cyclic voltammetry range of 0.05–1.1 V at a scan rate of 50 mV·s. -1 The test electrolytes were alkaline KOH (0.1M) and acidic H2SO4 (0.5M). ORR performance was tested using DECV in O2-saturated and N2-saturated electrolytes at a test value of 5 mV·s. -1 The scan rate and rotation speed were the same at 1600 rpm, and the voltage and CV tests were performed identically. For comparison, the performance of 20 wt% commercial Pt / c (mass loading of 20) was also tested under the same conditions. For accurate comparison, the half-wave potential E1 / 2 is denoted as a current density of 3.0 mA / cm². -2The potential at that time.

[0057] like Figure 1 The XRD pattern of the Gd-NC catalyst prepared in Example 1 is shown, in which peaks are shown at 24° and 42.3°, pointing to the (002) and (100) planes of graphitic carbon, indicating that the catalyst is highly graphitized.

[0058] like Figure 2 The image shows a SEM image of the Gd-NC catalyst prepared in Example 1. The image shows that the GdNC catalyst has a self-supporting three-dimensional structure, resembling graphene sheets.

[0059] like Figure 3 The HAADF STEM and EELS spectra of the Gd-NC catalyst prepared in Example 1 are shown. The bright spots represent Gd metal atoms on the carbon nanosheets, indicating a uniform distribution of the metal active center atoms. Furthermore, the electron energy loss spectrum (EELS) was captured to detect the catalyst composition, showing that the catalyst is composed of Gd, N, and C.

[0060] like Figure 4 The nitrogen adsorption / desorption isotherms of the Gd-NC catalyst prepared in Example 1 are shown for testing specific surface area. The figure shows that the curve for the GdNC catalyst between 0 and 1.0P / P0 exhibits a type IV hysteresis loop, with a specific surface area of ​​788.73 m². 2 g -1 .

[0061] like Figure 5 The figures show the ORR polarization curves of Gd-NC catalysts with different proportions in Examples 1-4 in 1.0 MkOH electrolyte; among them, the half-wave potential of Gd1N2C is the best at 0.89 V, which is 30 mV higher than that of Pt / C at 0.86 V; the half-wave potentials of Gd1N1C are 0.87 V, Gd1N3C is 0.865 V, and Gd2N1C is 0.82 V.

[0062] Figure 6 ORR polarization curve of Fe-Gd diatomic catalyst in 1.0 MKOH electrolyte.

[0063] Figure 7 Electron transfer number and hydrogen peroxide yield of Fe-Gd diatomic catalyst in 1.0 MKOH electrolyte;

[0064] Figure 8 ORR polarization curves of Fe-Gd diatomic catalyst in 0.5M H2SO4 electrolyte;

[0065] Figure 9 Electron transfer number and hydrogen peroxide yield of Fe-Gd diatomic catalyst in 0.5 M H₂SO₄ electrolyte. From... Figure 5-8 It can be seen that the GdNC catalyst prepared in Example 1 has a half-wave potential of 0.89V under alkaline conditions, which exceeds that of commercial Pt / C (0.86V) by 30mV; the Fe-Gd-NC catalyst prepared in Example 5 has a half-wave potential of 0.92V under alkaline conditions, which is far greater than that of Pt / C, and also reaches 0.80V under acidic conditions. Moreover, the introduction of Gd under both acidic and alkaline conditions effectively improves its 4-electron selectivity.

[0066] Figure 10 Example 1: Microwave absorption performance of Gd-NC material absorbing powder

[0067] The dielectric constant of Gd-NC absorbing powder is as follows: Figure 10 As shown in (ab), the absorber with a load of only 5% and mixed with paraffin was measured using a network vector analyzer. The real part (ε′) of the dielectric constant gradually decreases from low frequency to high frequency, ranging from 11.5 to 6.3, while the imaginary part of the dielectric constant remains basically unchanged in the low-to-mid frequency region (2-10 GHz), and then gradually decreases in the high frequency region, ranging from 0.3 to 4.1.

[0068] Figure 10 (c) The Gd-NC reflection loss diagram shows that when the thickness is 2.3 mm, it exhibits the lowest reflection loss value (RL) of -63.1 dB in the mid-to-low frequency range, with an effective absorption bandwidth of 4.7 GHz (EAB, RL ≤ -10 dB, electromagnetic wave absorption > 90.0%), effectively covering the 6.6-10.8 GHz band. At a thickness of 2.5 mm, it has the highest EAB value of 4.7 GHz and an RL value of -34.4 dB. Furthermore, when the thickness is less than 5 mm, it can effectively cover the 4-18 GHz band. Gd-NC absorbing powder is primarily characterized by dielectric loss, exhibiting extremely strong dielectric loss in the mid-to-low frequency range. This indicates that Gd-NC absorbing powder demonstrates a strong absorption loss capability in the mid-to-low frequency band.

[0069] Figure 10 In (d), each semicircle is called a Cole-Cole semicircle, representing a Debye relaxation process. The material exhibits dipole orientation polarization. The straight lines in the graph represent conductivity loss. The more semicircles or semicircular curves in the graph, the stronger the dielectric loss capability of the material, exhibiting excellent microwave absorption performance. The graph shows the presence of Cole-Cole semicircles, indicating the existence of a Debye relaxation process in the material. The curves in the low-to-mid-frequency range are semicircular, while those in the high-frequency range are linear, indicating the existence of multiple dielectric loss mechanisms in the material.

[0070] Table 1 shows the XPS elemental content test results of Gd-NC materials with different ratios in Examples 1-3. It can be seen that the final elemental content of the catalysts obtained from samples with different precursor-to-metal source ratios are different, with Gd1N2C having the highest Gd content of 3.18%.

[0071] Table 1

[0072]

[0073] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A Gd-NC material, characterized in that, The material is a carbon material doped with metal atoms and N, wherein the metal atoms include at least Gd; The material has a density of 700-800m. 2 g -1 The material has a specific surface area; it has a self-supporting three-dimensional structure and is in the form of graphene sheets; the elemental content percentage of Gd:N:C in the material is 1-5:1-10:80-95.

2. The material according to claim 1, characterized in that, The metal atoms also include one or more of Fe, Co, and Mn.

3. A method for preparing the material according to any one of claims 1-2, characterized in that, Includes the following: (1) Add N-containing carbon precursor and metal salt to a ball milling jar containing template agent and ball mill complex to form a complex with metal ion coordination. (2) The complex is dried, thermally decomposed under the protection of an inert gas, then rinsed, dried, and then thermally decomposed again to obtain metal atom-NC material.

4. The method for preparing the material according to claim 3, characterized in that, The metal salt is a Gd salt, which is gadolinium chloride hexahydrate; the molar ratio of Gd salt to the carbon precursor of N is 1-2:1-3.

5. The method for preparing the material according to claim 3, characterized in that, The metal salt is one or more of Fe, Co, and Mn salts, and the Fe salt is ferrous chloride tetrahydrate; after rinsing in step (2), the sample is centrifuged to obtain the sample; an ethanol solution containing Gd salt is added to the sample, and the sample is ultrasonically stirred until the ethanol is completely evaporated, and then a second thermal pyrolysis is performed to obtain the multi-metal atom-NC material.

6. The method for preparing the material according to claim 5, characterized in that, The molar ratio of N-containing carbon precursors: one or more of Fe, Co, and Mn salts to Gd salt is 1:2-4:0.5-1.

7. The method for preparing the material according to any one of claims 3-6, characterized in that, The nitrogen-containing carbon precursor is 2,6-diaminopyridine; and / or the template agent is sodium chloride.

8. The method for preparing the material according to claim 3, characterized in that, The ball milling time is 12-24 hours, and the ball milling speed is 450-600 r / min; The drying of the complex and / or the drying of the complex are carried out at 70-90℃ for 8-10 hours; the thermal pyrolysis reaction conditions are thermal pyrolysis at 800-950℃ for 1-2 hours. The rinsing and / or washing process includes immersing the pyrolyzed material in H2SO4 solution at 80℃-100℃ for 8-12 hours, filtering and washing with water multiple times until the filtrate is neutral, and drying the filtered sample under vacuum for 5-10 hours at a temperature of 60-100℃.

9. A use of the material as described in any one of claims 1-2, characterized in that, The Gd-NC material is used for electrochemical oxygen reduction catalysis and absorption of electromagnetic waves.

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