A NiFeX LDH@MWCNT nanocomposite material and its preparation method and application
The preparation of NiFeX LDH@MWCNT nanocomposite material was solved by microwave-assisted method, and the problem of low OER efficiency in hydrogen production by electrolyzing water was achieved, efficient and low-cost catalyst preparation was achieved, and the efficiency of the anode oxygen evolution reaction was improved.
Patent Information
- Application Number
- CN202210961453.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-11
- Publication Date
- 2025-08-19
- Estimated Expiration
- 2042-08-11
AI Technical Summary
The existing process of electrolyzing hydrogen production has low efficiency of the anode oxygen evolution reaction (OER), insufficient reserves of precious metals on commercial catalysts and expensive, and the existing LDHs preparation methods have a long reaction time and are difficult to control the morphology, which affects the catalyst performance.
The NiFeX LDH@MWCNT nanocomposite was prepared by microwave-assisted method. By reacting multi-walled carbon nanotubes with NiFeX salt and urea in a microwave reactor, NiFeX LDH@MWCNT nanocomposite was formed, and the high specific surface area of MWCNT and the catalytic activity of NiFeX were used to improve the OER efficiency.
It realizes a large-scale preparation of NiFeX LDH@MWCNT nanocomposite with simple operation, good controllability and high repeatability. As a catalyst, it significantly improves the efficiency of the anode oxygen evolution reaction and reduces costs.
Smart Images
Figure CN115369419B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of preparation of organic porous nanomaterials, and in particular relates to a NiFeX LDH@MWCNT nanocomposite material and a preparation method and application thereof. Background Art
[0002] Using electricity to decompose water, the most abundant resource on Earth, into hydrogen and oxygen is a green and environmentally friendly solution to energy needs. Currently, the biggest obstacle to large-scale hydrogen production by water electrolysis is the anodic oxygen evolution reaction (OER), but its slow kinetics lead to overall low reaction efficiency. Therefore, selecting a suitable catalyst to accelerate the OER reaction kinetics and reduce the reaction barrier is a feasible solution. Existing commercial OER catalysts are mostly precious metal-based catalysts (such as RuO2, IrO2, etc.). Although they exhibit excellent OER catalytic performance, they are difficult to achieve large-scale application due to their high price and lack of reserves. Therefore, the development of cheap and efficient non-precious metal-based catalysts is of great significance.
[0003] Recently, transition-metal-based layered double hydroxides (LDHs) have attracted considerable attention for their excellent catalytic activity. Currently, LDHs are prepared by a variety of methods, including hydrothermal / solvothermal, chemical bath deposition, microwave-assisted synthesis, ion exchange, and electrodeposition. However, with the exception of microwave-assisted synthesis, all other methods suffer from long reaction times. Furthermore, without treatment at a specific temperature and pressure, controlling the material's morphology is difficult, hindering the efficient preparation of electrocatalysts. Summary of the Invention
[0004] In order to solve the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a NiFeX LDH@MWCNT nanocomposite material and a preparation method and application thereof.
[0005] The purpose of the present invention is achieved through the following technical solutions:
[0006] A method for preparing a NiFeX LDH@MWCNT nanocomposite material comprises the following steps:
[0007] (1) First, multi-walled carbon nanotubes are dissolved in a solvent and uniformly dispersed by ultrasonication, and then nickel nitrate, iron nitrate, a salt containing an element X and urea are added and stirred to form a uniform solution; X is selected from Mo 6+ 、Mn 2+ and Cs + Any of the following;
[0008] (2) placing the solution obtained in step (1) in a microwave reactor, heating it to 100-200° C. under a nitrogen atmosphere, and keeping it warm for 1-10 minutes to react. After the reaction is completed, centrifuging it several times with water and anhydrous ethanol, respectively, and finally washing it alternately with water and anhydrous ethanol several times. After drying, the NiFeX LDH@MWCNT nanocomposite material is prepared.
[0009] Preferably, in step (1), the concentration of the multi-walled carbon nanotubes in the solution is 0.01 to 2 g / L, more preferably 0.2 g / L. The sample prepared under this condition has the highest catalytic performance.
[0010] Preferably, in step (1), the molar ratio of nickel element to iron element in nickel nitrate and iron nitrate is 8:1 to 1:1, more preferably 3:1.
[0011] Preferably, in step (1), the concentration of urea in the solution is 0.01 to 1 mol / L, more preferably 0.25 mol / L.
[0012] Preferably, in step (1), the salt containing element X is one of manganese nitrate, sodium molybdate and cesium carbonate.
[0013] Preferably, in step (1), the concentration of element X in the salt of element X in the solution is 0.001 to 0.5 mol / L, more preferably 0.05 mol / L.
[0014] Preferably, in step (2), the power of the microwave reactor is 150-675W, more preferably 375W.
[0015] Preferably, in step (2), the pressure of the nitrogen atmosphere is 0.15 MPa. This gas can act as a carrier gas to promote the flow of gas in the container and ensure sufficient reaction.
[0016] Preferably, in step (2), the number of centrifugation with water and anhydrous ethanol is 2 times. If the number of centrifugation is insufficient, the obtained product cannot be dried.
[0017] Preferably, in step (2), the number of times of alternate rinsing with water and anhydrous ethanol is 3 times.
[0018] The NiFeX LDH@MWCNT nanocomposite material is prepared by the above-mentioned method for preparing the NiFeX LDH@MWCNT nanocomposite material.
[0019] The above-mentioned NiFeX LDH@MWCNT nanocomposite material is used as an anode oxygen evolution reaction catalyst in hydrogen production by water splitting.
[0020] Compared with the prior art, the present invention has the following beneficial effects:
[0021] The method of the present invention uses a microwave-assisted one-step process to generate NiFeX LDH@MWCNT nanocomposites. This method is simple to operate, has good controllability, good reproducibility, and can be prepared on a large scale. It provides a reliable sample preparation method for the microwave-based preparation of LDH materials for use in water electrolysis to produce oxygen. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is the X-ray diffraction pattern of the NiFe LDH@MWCNT nanocomposite material prepared in Comparative Example 1.
[0023] Figure 2 This is the X-ray photoelectron spectrum of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1.
[0024] Figure 3 These are the scanning electron microscope images and element distribution images of the NiFe LDH@MWCNT nanocomposite material prepared in Comparative Example 1, where a to c correspond to the scanning electron microscope images, and d corresponds to the element distribution image.
[0025] Figure 4 These are the transmission electron microscopy images and selected area electron diffraction images of the NiFe LDH@MWCNT nanocomposite material prepared in Comparative Example 1, wherein a to c are electron microscopy images at different magnifications, d is a high-resolution transmission electron microscopy image, and d1 is a selected area electron diffraction image.
[0026] Figure 5 The figure in the middle is a comparison chart of various performance tests of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1 and the NiFeLDH@rGO nanocomposite prepared in Comparative Example 2, wherein a is the oxygen evolution polarization curve, b is the Tafel slope, c is the impedance diagram, and d is the stability test of the NiFe LDH@MWCNT nanocomposite.
[0027] Figure 6 These are the transmission electron microscopy images and selected area electron diffraction images of the NiFeMn LDH@MWCNT nanocomposite prepared in Example 1, where a to c correspond to scanning electron microscopy images, d corresponds to a high-resolution transmission microscopy image, and d1 corresponds to a selected area electron diffraction image.
[0028] Figure 7 Transmission electron micrographs of the NiFeMo LDH@MWCNT nanocomposite prepared in Example 2 at different magnifications.
[0029] Figure 8These are transmission electron microscopy images and selected area electron diffraction images of the NiFeCs LDH@MWCNT nanocomposite prepared in Example 3, where a to c correspond to scanning electron microscopy images, and d corresponds to a selected area electron diffraction image.
[0030] Figure 9 This is a comparison diagram of the oxygen evolution polarization curves and Tafel slope diagrams of the NiFeMn LDH@MWCNT nanocomposite prepared in Example 1, the NiFeMnLDH nanomaterial prepared in Comparative Example 3, and the NiFeMn LDH@rGO nanocomposite prepared in Comparative Example 4, where a corresponds to the oxygen evolution polarization curve and b corresponds to the Tafel slope.
[0031] Figure 10 3 is a comparison chart of various performance tests of the NiFeCs LDH@MWCNT nanocomposite prepared in Example 3, the NiFeCsLDH nanomaterial prepared in Comparative Example 5, and the NiFeCs LDH@rGO nanocomposite prepared in Comparative Example 6, wherein a is the oxygen evolution polarization curve, b is the Tafel slope, c is the impedance diagram, and d is the stability test of the NiFeCs LDH@MWCNT nanocomposite. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0033] The microwave reactor used in the examples and comparative examples was purchased from Zhengzhou Bangboshi Instrument Equipment Co., Ltd., model MCR-3.
[0034] Comparative Example 1
[0035] A method for preparing a NiFe LDH@MWCNT nanocomposite material comprises the following steps:
[0036] (1) Using 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, and 0.02 g multi-walled carbon nanotubes as raw materials, 50 ml ethylene glycol and 50 ml deionized water as solvent, the multi-walled carbon nanotubes were first dissolved in the solvent and ultrasonicated for 15 minutes; immediately after the ultrasonication, the remaining raw materials were added and magnetically stirred for 15 minutes to form a uniform solution;
[0037] (2) Transfer the resulting solution into a three-necked flask;
[0038] (3) The three-necked flask was then transferred to a microwave reactor, a thermometer was inserted into the left port, a condenser was inserted into the middle port, and nitrogen (pressure of 0.15 MPa) was introduced into the right port to prevent the reaction from being too intense;
[0039] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0040] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0041] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol, respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately. Finally, the NiFe LDH@MWCNT nanocomposite material was obtained after drying.
[0042] Comparative Example 2
[0043] A method for preparing a NiFe LDH@rGO nanocomposite material comprises the following steps:
[0044] (1) Using 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea and 0.02 g graphene oxide as raw materials, 50 ml ethylene glycol and 50 ml deionized water as solvent, first dissolve the graphene oxide in the solvent and ultrasonicate for 15 minutes; immediately after the ultrasonication, add the remaining raw materials and magnetically stir for 15 minutes to form a uniform solution;
[0045] (2) Transfer the resulting solution into a three-necked flask;
[0046] (3) The three-necked flask was then transferred to a microwave reactor, a thermometer was inserted into the left port, a condenser was inserted into the middle port, and nitrogen (pressure of 0.15 MPa) was introduced into the right port to prevent the reaction from being too intense;
[0047] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0048] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0049] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol, respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately. Finally, the NiFe LDH@rGO nanocomposite material was obtained after drying.
[0050] Figure 1 The X-ray diffraction pattern of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1. Figure 1It can be seen that the (003), (101), (012), (110), and (113) planes in the material corresponding to the typical peaks of NiFe LDH@MWCNT have no obvious changes. It is worth noting that the (002) plane of MWCNT (multi-walled carbon nanotubes) and the (006) crystal plane of NiFe LDH seem to have a strong interaction due to their close positions, resulting in a large angle displacement of the two peaks in this part. However, since it is only a single peak, not all peaks in the entire spectrum have shifted, it is judged that the reason may be that the macroscopic residual stress has caused lattice distortion. In fact, from Figure 1 It can be observed that the (110) and (113) crystal planes of NiFe LDH are almost merged together. This merger is usually caused by residual stress, which leads to grain refinement and the diffraction peaks become broad and mixed.
[0051] Figure 2 This is the X-ray photoelectron spectrum of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1. Figure 2 The valence states of the elements O, Ni, and Fe shown are consistent with those of NiFe LDH.
[0052] Figure 3 The scanning electron microscope images and element distribution images of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1, where a to c correspond to the scanning electron microscope images and d corresponds to the element distribution image. Figure 3 It can be seen that the tubular MWCNTs (multi-walled carbon nanotubes) are interwoven together to form a solid block structure, with a large number of NiFe LDH particles attached to it. The energy spectrum shows that the Ni, Fe, and C elements are evenly distributed.
[0053] Figure 4 The transmission electron microscopy images and selected area electron diffraction images of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1 are shown, where a to c are electron microscopy images at different magnifications, d is a high-resolution transmission electron microscopy image, and d1 is a selected area electron diffraction image. The image d shows that the lattice fringe spacing is 0.190nm and 0.203nm, corresponding to the (018) crystal plane of NiFe LDH and the 101 crystal plane of MWCNT, respectively. Figure 4 It can be seen that NiFe LDH and MWCNT structures can be well combined to form a heterostructure, and the target product is successfully prepared.
[0054] Figure 5The figure below is a comparison of the performance tests of the NiFe LDH@MWCNT nanocomposite prepared in Comparative Example 1 and the NiFeLDH@rGO nanocomposite prepared in Comparative Example 2, where a is the oxygen evolution polarization curve, b is the Tafel slope, c is the impedance diagram, and d is the stability test of the NiFe LDH@MWCNT nanocomposite. 2 The overpotential in this case is 296 mV; the Tafel slope is 57.38 mV / dec.
[0055] Specifically, the test was carried out in a standard three-electrode electrolytic cell system. The working electrode was a glassy carbon electrode (GC, CHI104), loaded with 20 g of powder sample; the reference electrode was a mercury / mercury oxide electrode (Hg / HgO, CHI152); the counter electrode was a graphite rod; the electrolyte was a 1 M KOH solution, and the glassware was cleaned with diluted HCl before the experiment to remove impurities.
[0056] The test steps and test conditions for the oxygen evolution polarization curve are as follows: after installing the three-electrode system, connect it to the workstation, scan 20 CV (cyclic voltammetry) cycles, and start the test after ensuring that the material is stable; the CV cycle test voltage range is 0-0.8V, the scanning mode is forward scan, and the rate is 0.1V / s; the oxygen evolution polarization curve test voltage range is 0-0.8V, and the scanning rate is 0.005V / s.
[0057] The test steps and test conditions of Tafel slope are as follows: After determining the oxygen evolution polarization curve, according to the Tafel equation, that is, The dynamic properties of the material, namely the Tafel diagram, are obtained.
[0058] The test steps and test conditions of the impedance diagram are as follows: after the oxygen evolution polarization curve test is completed, the impedance test is started, and the frequency range is selected from 0.01 to 100,000 Hz.
[0059] The stability test procedure and test conditions are as follows: First, perform 20 CV cycles in the 0-0.8V vs. RHE range at a scan rate of 0.1V / s. Then, perform LSV testing, which is recorded as the initial data. Then, perform 2000 CV cycles in the same range and then perform LSV testing to obtain test data. By comparing the difference between the test data and the initial data, the stability difference of the material can be determined.
[0060] from Figure 5 As can be seen in Figures a and b, the overpotential and Tafel slope of the LDH composited with MWCNTs are lower than those with rGO, indicating that the MWCNT composite material is more effective than rGO. The impedance graph in Figure c supports this conclusion. The results in Figure d demonstrate the excellent stability of the MWCNT composite sample. Figure 5Overall, it is shown that the choice of MWCNT for composite materials is more advantageous than similar products. The reason is presumably that MWCNT has a higher specific surface area and active sites.
[0061] Comparative Example 3
[0062] A method for preparing a NiFeMn LDH nanomaterial comprises the following steps:
[0063] (1) 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, and 0.005 mol Mn(NO3)2·xH2O were used as raw materials, 50 ml ethylene glycol and 50 ml deionized water were used as solvents, and magnetic stirring was performed for 15 minutes to form a homogeneous solution;
[0064] (2) Transfer the resulting solution into a three-necked flask;
[0065] (3) The three-necked flask was then transferred to a microwave reactor, a thermometer was inserted into the left port, a condenser was inserted into the middle port, and nitrogen (pressure of 0.15 MPa) was introduced into the right port to prevent the reaction from being too intense;
[0066] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0067] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0068] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeMn LDH nanomaterial.
[0069] Comparative Example 4
[0070] A method for preparing a NiFeMn LDH@rGO nanocomposite material comprises the following steps:
[0071] (1) Using 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, 0.005 mol Mn(NO3)2·xH2O, and 0.02 g graphene oxide as raw materials, 50 ml ethylene glycol and 50 ml deionized water as solvent, the graphene oxide was first dissolved in the solvent and ultrasonicated for 15 minutes; after the ultrasonication, the remaining raw materials were immediately added and magnetically stirred for 15 minutes to form a homogeneous solution;
[0072] (2) Transfer the resulting solution into a three-necked flask;
[0073] (3) The three-necked flask was then transferred to a microwave reactor, a thermometer was inserted into the left port, a condenser was inserted into the middle port, and nitrogen (pressure of 0.15 MPa) was introduced into the right port to prevent the reaction from being too intense;
[0074] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0075] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0076] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeMn LDH@rGO nanocomposite material.
[0077] Example 1
[0078] A method for preparing a NiFeMn LDH@MWCNT nanocomposite material comprises the following steps:
[0079] (1) 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, 0.005 mol Mn(NO3)2·xH2O, and 0.02 g multi-walled carbon nanotubes were used as raw materials, and 50 ml ethylene glycol and 50 ml deionized water were used as solvent. The multi-walled carbon nanotubes were first dissolved in the solvent and ultrasonicated for 15 minutes. After the ultrasonication, the remaining raw materials were immediately added and magnetically stirred for 15 minutes to form a uniform solution.
[0080] (2) Transfer the resulting solution into a three-necked flask;
[0081] (3) Then transfer the three-necked flask into a microwave reactor, insert a thermometer into the left port, insert a condenser into the middle port, and introduce nitrogen into the right port to prevent the reaction from being too intense;
[0082] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0083] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0084] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeMn LDH@MWCNT nanocomposite material.
[0085] This embodiment also provides a NiFeMn LDH@MWCNT nanocomposite material obtained by the method. 2The overpotential at this current density is 305 mV, the Tafel slope is 43.35 mV / dec, and the charge transfer impedance is as low as 19.98 Ω.
[0086] Example 2
[0087] A method for preparing a NiFeMo LDH@MWCNT nanocomposite material comprises the following steps:
[0088] (1) 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, 0.005 mol Na2MoO4·2H2O, and 0.02 g multi-walled carbon nanotubes were used as raw materials, and 50 ml ethylene glycol and 50 ml deionized water were used as solvent. The multi-walled carbon nanotubes were first dissolved in the solvent and ultrasonicated for 15 minutes. After the ultrasonication, the remaining raw materials were immediately added and magnetically stirred for 15 minutes to form a homogeneous solution.
[0089] (2) Transfer the resulting solution into a three-necked flask;
[0090] (3) Then transfer the three-necked flask into a microwave reactor, insert a thermometer into the left port, insert a condenser into the middle port, and introduce nitrogen into the right port to prevent the reaction from being too intense;
[0091] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0092] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0093] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeMo LDH@MWCNT nanocomposite material.
[0094] Comparative Example 5
[0095] A method for preparing a NiFeCs LDH nanomaterial comprises the following steps:
[0096] (1) 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, and 0.005 mol Cs2CO3 were used as raw materials, 50 ml ethylene glycol and 50 ml deionized water were used as solvents, and magnetic stirring was performed for 15 minutes to form a homogeneous solution;
[0097] (2) Transfer the resulting solution into a three-necked flask;
[0098] (3) Then transfer the three-necked flask into a microwave reactor, insert a thermometer into the left port, insert a condenser into the middle port, and introduce nitrogen into the right port to prevent the reaction from being too intense;
[0099] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0100] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0101] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeCs LDH nanomaterial.
[0102] Comparative Example 6
[0103] A method for preparing a NiFeCs LDH@rGO nanocomposite material comprises the following steps:
[0104] (1) Using 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, 0.005 mol Cs2CO3, and 0.02 g graphene oxide as raw materials, 50 ml ethylene glycol and 50 ml deionized water as solvent, the graphene oxide was first dissolved in the solvent and ultrasonicated for 15 minutes; after the ultrasonication, the remaining raw materials were immediately added and magnetically stirred for 15 minutes to form a uniform solution;
[0105] (2) Transfer the resulting solution into a three-necked flask;
[0106] (3) Then transfer the three-necked flask into a microwave reactor, insert a thermometer into the left port, insert a condenser into the middle port, and introduce nitrogen into the right port to prevent the reaction from being too intense;
[0107] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0108] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0109] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeCs LDH@rGO nanocomposite material.
[0110] Example 3
[0111] A method for preparing a NiFeCs LDH@MWCNT nanocomposite material comprises the following steps:
[0112] (1) Using 3 mmol nickel nitrate, 1 mmol iron nitrate, 0.025 mol urea, 0.005 mol Cs2CO3, and 0.02 g multi-walled carbon nanotubes as raw materials, 50 ml ethylene glycol and 50 ml deionized water as solvent, the multi-walled carbon nanotubes were first dissolved in the solvent and ultrasonicated for 15 minutes; immediately after the ultrasonication, the remaining raw materials were added and magnetically stirred for 15 minutes to form a homogeneous solution;
[0113] (2) Transfer the resulting solution into a three-necked flask;
[0114] (3) Then transfer the three-necked flask into a microwave reactor, insert a thermometer into the left port, insert a condenser into the middle port, and introduce nitrogen into the right port to prevent the reaction from being too intense;
[0115] (4) Raise the temperature of the microwave reactor from room temperature to 180°C and then maintain it for 3 minutes;
[0116] (5) After the reaction is completed, wait for the microwave reactor to cool to room temperature and take out the three-necked flask;
[0117] (6) The obtained reaction solution was centrifuged twice with deionized water and anhydrous ethanol respectively, and then rinsed three times with deionized water and anhydrous ethanol alternately, and finally dried to obtain the NiFeCs LDH@MWCNT nanocomposite material.
[0118] Figure 6 The transmission electron microscopy images and selected area electron diffraction images of the NiFeMn LDH@MWCNT nanocomposite prepared in Example 1, where a to c correspond to scanning electron microscopy images, d corresponds to a high-resolution transmission microscopy image, and d1 corresponds to a selected area electron diffraction image. Figure 6 As can be seen, Figures a to c show that the NiFeMn LDH@MWCNT nanocomposite has a typical tubular structure, representing the morphology of MWCNT, and is loaded with LDH. Figure d shows that the (018) crystal plane of LDH and the (101) crystal plane of MWCNT form a heterostructure. Figure d1 observes the diffraction rings formed by the NiFeMn LDH@MWCNT material, corresponding to the (110) crystal plane of LDH and the (006) crystal plane of MWCNT, respectively.
[0119] Figure 7 Transmission electron micrographs of the NiFeMo LDH@MWCNT nanocomposite prepared in Example 2 at different magnifications.
[0120] Figure 8 Transmission electron microscopy images and selected area electron diffraction images of the NiFeCs LDH@MWCNT nanocomposite prepared in Example 3, wherein a to c correspond to scanning electron microscopy images, and d corresponds to a selected area electron diffraction image. Figure 8 It can be seen that: a~c show that in addition to the unique tubular structure ((003) plane of MWCNT), the LDH structure of NiFeCs LDH@MWCNT can also be clearly observed, corresponding to the (110) crystal plane of the LDH structure.
[0121] Figure 9 This is a comparison diagram of the oxygen evolution polarization curves and Tafel slope diagrams of the NiFeMn LDH@MWCNT nanocomposite prepared in Example 1, the NiFeMnLDH nanomaterial prepared in Comparative Example 3, and the NiFeMn LDH@rGO nanocomposite prepared in Comparative Example 4, where a corresponds to the oxygen evolution polarization curve and b corresponds to the Tafel slope.
[0122] Specifically, the test was carried out in a standard three-electrode electrolytic cell system. The working electrode was a glassy carbon electrode (GC, CHI104), loaded with 20 g of powder sample; the reference electrode was a mercury / mercury oxide electrode (Hg / HgO, CHI152); the counter electrode was a graphite rod; the electrolyte was a 1 M KOH solution, and the glassware was cleaned with diluted HCl before the experiment to remove impurities.
[0123] The test steps and test conditions for the oxygen evolution polarization curve are as follows: after installing the three-electrode system, connect it to the workstation, scan 20 CV (cyclic voltammetry) cycles, and start the test after ensuring that the material is stable; the CV cycle test voltage range is 0-0.8V, the scanning mode is forward scan, and the rate is 0.1V / s; the oxygen evolution polarization curve test voltage range is 0-0.8V, and the scanning rate is 0.005V / s.
[0124] The test steps and test conditions of Tafel slope are as follows: After determining the oxygen evolution polarization curve, according to the Tafel equation, that is, The dynamic properties of the material, namely the Tafel diagram, are obtained.
[0125] from Figure 9 It can be seen that NiFeMn LDH@MWCNT has a better effect than pure NiFeMn LDH and NiFeMn LDH composited with rGO, which shows that MWCNT can strongly interact with NiFeMn LDH and jointly promote the improvement of reaction efficiency.
[0126] Figure 10 3 is a comparison chart of various performance tests of the NiFeCs LDH@MWCNT nanocomposite prepared in Example 3, the NiFeCsLDH nanomaterial prepared in Comparative Example 5, and the NiFeCs LDH@rGO nanocomposite prepared in Comparative Example 6, wherein a is the oxygen evolution polarization curve, b is the Tafel slope, c is the impedance diagram, and d is the stability test of the NiFeCs LDH@MWCNT nanocomposite.
[0127] Specifically, the test steps and test conditions of the oxygen evolution polarization curve are as follows:
[0128] Specifically, the test was carried out in a standard three-electrode electrolytic cell system. The working electrode was a glassy carbon electrode (GC, CHI104), loaded with 20 g of powder sample; the reference electrode was a mercury / mercury oxide electrode (Hg / HgO, CHI152); the counter electrode was a graphite rod; the electrolyte was a 1 M KOH solution, and the glassware was cleaned with diluted HCl before the experiment to remove impurities.
[0129] The test steps and test conditions for the oxygen evolution polarization curve are as follows: after installing the three-electrode system, connect it to the workstation, scan 20 CV (cyclic voltammetry) cycles, and start the test after ensuring that the material is stable; the CV cycle test voltage range is 0-0.8V, the scanning mode is forward scan, and the rate is 0.1V / s; the oxygen evolution polarization curve test voltage range is 0-0.8V, and the scanning rate is 0.005V / s.
[0130] The test steps and test conditions of Tafel slope are as follows: After determining the oxygen evolution polarization curve, according to the Tafel equation, that is, The dynamic properties of the material, namely the Tafel diagram, are obtained.
[0131] The test steps and test conditions of the impedance diagram are as follows: after the oxygen evolution polarization curve test is completed, the impedance test is started, and the frequency range is selected from 0.01 to 100,000 Hz.
[0132] The stability test procedure and test conditions are as follows: First, perform 20 CV cycles in the 0-0.8V vs. RHE range at a scan rate of 0.1V / s. Then, perform LSV testing, which is recorded as the initial data. Then, perform 2000 CV cycles in the same range and then perform LSV testing to obtain test data. By comparing the difference between the test data and the initial data, the stability difference of the material can be determined.
[0133] from Figure 10 It can be seen that the NiFe LDH doped with Cs and composited with MWCNT exhibits excellent electrochemical performance. Figure a shows that at 10 mA / cm 2 Under the conditions of CV, the overpotential is 283 mV, and Figure (b) shows a Tafel slope as low as 53.40 mV / dec. Figure (c) shows that the Faradaic impedance of NiFeCs LDH@MWCNT calculated from the EIS spectrum is 35.84 Ω, while the initial NiFeCs LDH reaches 106.6 Ω. In addition, Figure (d) shows that NiFeCs LDH@MWCNT exhibits extremely strong electrochemical stability, and after 2000 cycles, most of the electrochemical activity of the material is still retained. This indicates that the Cs element has a strong synergistic effect with MWCNT.
[0134] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a NiFeX LDH@MWCNT nanocomposite material, characterized in that: The steps include: (1) First, multi-walled carbon nanotubes are dissolved in a solvent and dispersed evenly by ultrasonication. Then, nickel nitrate, iron nitrate, a salt containing element X, and urea are added and stirred to form a uniform solution; X is Cs + ; The solvent is ethylene glycol and deionized water; (2) The solution prepared in step (1) is placed in a microwave reactor, heated to 100-200° C. under a nitrogen atmosphere, and kept warm for 1-10 minutes to react. After the reaction is completed, the solution is centrifuged several times with water and anhydrous ethanol, respectively, and finally rinsed alternately with water and anhydrous ethanol several times. After drying, the NiFeX LDH@MWCNT nanocomposite material is prepared.
2. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to claim 1, characterized in that: The concentration of the multi-walled carbon nanotubes in the solution in step (1) is 0.01-2 g / L.
3. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to claim 2, characterized in that: In the nickel nitrate and ferric nitrate of step (1), the molar ratio of nickel element to iron element is 8:1 to 1:
1.
4. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to claim 2 or 3, characterized in that: The concentration of the multi-walled carbon nanotubes in the solution in step (1) is 0.2 g / L; and the molar ratio of nickel to iron in the nickel nitrate and iron nitrate in step (1) is 3:
1.
5. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to any one of claims 1 to 3, characterized in that: In the salt of element X in step (1), the concentration of element X in the solution is 0.001-0.5 mol / L; The concentration of urea in the solution in step (1) is 0.01~1 mol / L.
6. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to claim 5, characterized in that: In the salt of element X in step (1), the concentration of element X in the solution is 0.05 mol / L; and in the solution of urea in step (1), the concentration is 0.25 mol / L.
7. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to any one of claims 1 to 3, characterized in that: The salt containing element X in step (1) is cesium carbonate; The power of the microwave reactor in step (2) is 150~675W.
8. The method for preparing a NiFeX LDH@MWCNT nanocomposite material according to claim 7, characterized in that: The pressure of the nitrogen atmosphere in step (2) is 0.15 MPa; The number of centrifugation with water and anhydrous ethanol in step (2) is 2 times; The number of times of alternate rinsing with water and anhydrous ethanol in step (2) is 3 times.
9. A NiFeX LDH@MWCNT nanocomposite material prepared by the method for preparing a NiFeX LDH@MWCNT nanocomposite material according to any one of claims 1 to 8.
10. Use of the NiFeX LDH@MWCNT nanocomposite material according to claim 9 as an anode oxygen evolution reaction catalyst in hydrogen production by hydrolysis.
Citation Information
Patent Citations
Preparation method of Bi@NiFe-LDH / NF composite material
CN112695334A