Preparation method and application of nano needle-shaped g-C3N4-FeNiMnCo composite material

Abstract

The invention belongs to the field of composite material electro-catalysis, and discloses a preparation method and application of a nano needle-shaped g-C3N4-FeNiMnCo composite material, and the nano needle-shaped g-C3N4-FeNiMnCo composite material is particularly used for producing hydrogen by electrolyzing water. The preparation method comprises the following steps: firstly, preparing g-C3N4, and then preparing the g-C3N4-FeNiMnCo composite material through a hydrothermal method. The nanoneedle of the obtained material is of a single-crystal fibrous structure which is smooth in surface and uniform in morphology, the top end is sharp, the diameter is uniform, the one-dimensional nanoneedle structure with the high aspect ratio provides an ideal path for rapid longitudinal transmission of charges, and exposure of more high-activity catalytic sites located at the edge and the defect position is facilitated. Meanwhile, tight interface coupling is formed between the FeNiMnCo high-entropy alloy nanoparticles and the g-C3N4 substrate, the structure can effectively promote interface charge transfer, and intrinsic activity and stability of the FeNiMnCo high-entropy alloy nanoparticles in the water electrolysis reaction are synergistically improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of composite materials electrocatalysis, and particularly relates to a preparation method of a nano needle-shaped g-C3N4-FeNiMnCo composite material and application thereof. BACKGROUND

[0002] Hydrogen energy has become a key carrier for global energy transformation due to its green and low-carbon advantages. Water electrolysis for hydrogen production is considered as the most promising hydrogen production technology due to its safety and non-pollution. However, the current water electrolysis has low efficiency and high cost of catalytic electrodes, which limits its large-scale application. Therefore, it is of great significance to develop high-efficiency and low-cost catalysts for promoting the development of hydrogen energy. The catalysts effectively improve the catalytic activity of the materials and reduce the overpotential by introducing defects, atomic doping, and constructing heterostructures. SUMMARY

[0003] In view of the deficiencies in the prior art, the application provides a preparation method of a nano needle-shaped g-C3N4-FeNiMnCo composite material and application thereof. The application uses graphite-like carbon-nitrogen material as a carrier, constructs a special nano needle structure, introduces defect engineering to improve the stability and durability, uses the super large specific surface area of the nano needle structure to provide rich catalytic active sites and mass transfer channels, and makes the transition metal-metal exist in the form of an alloy on the carrier. The catalyst synthesized on the g-C3N4 carrier by using non-noble metals effectively reduces the cost of the catalyst, forms an alloy structure, increases the specific surface area, improves the catalytic activity, and effectively reduces the dependence of the catalyst on noble metal materials.

[0004] The application achieves the above technical objectives through the following technical means.

[0005] A preparation method of a nano needle-shaped g-C3N4-FeNiMnCo composite material, comprising the following steps:

[0006] (1) Preparation of g-C3N4:

[0007] Take urea and place it in a crucible, and program the temperature to the calcination temperature in a muffle furnace. After calcination, grind the yellow powder after natural cooling, wash the product with deionized water several times, and vacuum dry to obtain pure g-C3N4;

[0008] (2) Preparation of g-C3N4-FeNiMnCo composite material by hydrothermal method.

[0009] The g-C3N4 is dispersed in deionized water, ultrasonic dispersion is carried out, Fe (NO3) 3 ·9H2O, Ni(NO3) 2 ·6H2O, Co(NO3) 2 ·6H2O and MnSO4 ·H2O are dissolved in deionized water under stirring, stirring is carried out, NH4F is added to carry out etching defect process, the mixed solution is transferred to a hydrothermal reaction kettle, hydrothermal reaction is carried out, after the reaction is completed, the precipitate is collected by centrifugation, and the precipitate is washed with deionized water and ethanol alternately for several times, and then dried to obtain a nano needle-shaped g-C3N4-FeNiMnCo composite material.

[0010] In step (1), the calcination temperature is 550 DEG C, the calcination time is 4h, and the temperature rising rate is 5 DEG C / min; the temperature of vacuum drying is 80 DEG C, and the time is 12h.

[0011] In step (2), the amount ratio of g-C3N4, deionized water, Fe (NO3) 3 ·9H2O, Ni(NO3) 2 ·6H2O, Co(NO3) 2 ·6H2O, MnSO4 ·H2O and NH4F is 0.1mmol:40mL:0.5mmol:0.5mmol:0.05mmol:0.01-0.05mmol:1.5mmol.

[0012] The ultrasonic dispersion time is 30min; the stirring time is 2h;

[0013] The temperature of hydrothermal reaction is 110-130 DEG C, and the time is 8-12h;

[0014] The drying temperature is 80 DEG C, and the time is 12h.

[0015] The nano needle-shaped g-C3N4-FeNiMnCo composite material prepared in the application is used to prepare an electrode for electrolysis of water to produce hydrogen.

[0016] The beneficial effects of the application are:

[0017] The composite material obtained in the application has a special nano needle structure, and the nano needle structure has a large specific surface area, provides rich catalytic active sites and mass transfer channels, and makes transition metals-metal exist in the form of alloy on the carrier.

[0018] First, under the condition of 120 DEG C, 12h hydrothermal reaction, metal ions are hydrolyzed, nucleated and directionally grown. The hydrothermal environment provides high temperature and high pressure conditions, promotes the preferential growth of crystals along a specific crystal face. The etching and defect guiding effect of NH4F plays a key role in the growth of the nano needle structure, and F - For some metal ions, especially Fe 3+ , Mn 2+The metal salts have strong complexation, and in the case of the optimal experimental formula, the special proportion of the metal salts leads to the content of Fe 3+ and Ni 2+ being much higher than that of Co 2 + and Mn 2+ , and the Fe / Ni-based system is more sensitive to etching, Fe 3+ has strong complexation with F - , and high content of Fe 3+ makes the etching effect more significant, and Mn 2+ is also easy to form a complex with F - , thereby enhancing the etching effect. Meanwhile, the introduction of Mn 2+ stabilizes the crystal field and has a fine-tuning effect on the growth kinetics, and Co 2+ and Ni 2+ have relatively weak complexation with F - , and they are enriched at the "skeleton" or new nucleation points after etching, serving as a "ridge" or stable structure for one-dimensional growth.

[0019] Secondly, the pre-dispersed g-C3N4 provides abundant surface sites, and metal ions are adsorbed on the surface thereof by electrostatic attraction or coordination, thereby limiting the free movement and random aggregation of metal ions or initial crystal nuclei in the solution. The lamellar structure of g-C3N4 itself may physically hinder the surface thereof from large-area two-dimensional planar spreading growth. On the contrary, it may guide the crystal to grow vertically to the surface thereof or promote the formation of high-density nucleation points in local areas, and these nucleation points are more likely to develop into needle-like structures when subjected to F⁻ etching and guiding in the subsequent process. The interlayer or surface defects of g-C3N4 may also provide confined spaces to promote the formation of one-dimensional structures.

[0020] Thirdly, the hydrothermal time and temperature are optimized. The hydrothermal synthesis temperature of 120℃ is high enough to promote crystal growth and F⁻ etching reaction, but it is not too high to cause structure destruction or phase transition. The hydrothermal synthesis time of 12h is long enough to ensure sufficient F⁻ etching and the crystal can grow along the one-dimensional direction guided by F⁻ to form a nanoneedle structure with uniform size and clear morphology. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 SEM image of the g-C3N4-FeNiMnCo composite material obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with the drawings and specific examples, but the scope of protection of the present application is not limited thereto.

[0023] Example 1

[0024] A nanoneedle-shaped g-C3N4-FeNiMnCo composite material and a preparation method thereof, the preparation method comprising:

[0025] (1) preparing g-C3N4.

[0026] Take 10 g of urea and place it in a crucible. Heat it in a muffle furnace at a rate of 5 ℃ / min to 550 ℃, and calcine for 4 h. After natural cooling, grind the yellow powder. Wash the product with deionized water 3 times, and dry it in a vacuum at 80 ℃ for 12 h to obtain pure g-C3N4.

[0027] (2) hydrothermal method for preparing g-C3N4-FeNiMnCo composite material.

[0028] Take 0.1 mmol of g-C3N4 and disperse it in 40 ml of deionized water, and ultrasonic it for 30 min. Add 0.5 mmol of Fe(NO3)3·9H2O, 0.5 mmol of Ni(NO3)2·6H2O, 0.05 mmol of Co(NO3)2·6H2O, and 0.05 mmol of MnSO4·H2O to deionized water under stirring, and stir for 2 h. Add 1.5 mmol of NH4F to perform defect etching process. Transfer the mixed solution to a 100 ml hydrothermal reactor, and react at 120 ℃ for 12 h. Then, centrifugally collect the precipitate, wash it with deionized water and ethanol alternately 3 times, and dry it at 80 ℃ for 12 h to obtain a nanoneedle-shaped g-C3N4-FeNiMnCo composite material, which is recorded as sample 3.

[0029] Figure 1The SEM image of the nanoneedle-like g-C3N4-FeNiMnCo composite material obtained in the present application is shown in Figure (a), which shows the fine structural details of the composite material at high magnification (x100k). At this resolution, it can be seen more clearly that the nanoneedles present a single-crystal fibrous structure with a smooth surface and uniform morphology, with sharp tips. In terms of size, the individual nanoneedles are uniformly distributed in the range of 50-100 nanometers, which is typical of one-dimensional nanomaterials; and their length can reach 1-3 micrometers, thereby giving them a high aspect ratio. This high-aspect-ratio one-dimensional nanoneedle structure not only provides an ideal path for the rapid longitudinal transmission of electric charges, but also facilitates the exposure of more high-activity catalytic sites located at the edges and defects. At the same time, the FeNiMnCo high-entropy alloy nanoparticles form a tight interface coupling with the g-C3N4 substrate, and this structure can effectively promote the interface charge transfer and synergistically improve the intrinsic activity and stability of the material in the water electrolysis reaction. Figure (b) shows the overall morphology of the g-C3N4-FeNiMnCo composite material prepared at a lower magnification (x50.0k). As can be observed from the figure, the material presents a micro-morphology composed of a large number of nanoneedle-like structures, which are relatively uniformly distributed and constitute the basic framework of the material. The nanoscale structure of the material has a micron-scale macroscopic aggregation morphology, and successfully self-assembles into a three-dimensional network architecture composed of a high-density, interwoven distribution of nanoneedle-like structures. This overall morphology ensures that the material has a large specific surface area and abundant pore structure, which is conducive to the mass transfer of reactants and products.

[0030] An electrode was prepared using the nanoneedle-like g-C3N4-FeNiMnCo composite material obtained in the present example.

[0031] 5 mg of g-C3N4-FeNiMnCo composite material, 1 mg of acetylene black as a conductive agent, and 0.1 ml of Nafion solution were mixed, ultrasonicated for 30 min to form a uniform slurry, 50 microliters of the slurry were sprayed on the surface of a pretreated 1 cm*1 cm nickel foam (the pretreatment method was to sequentially ultrasonically clean the surface of the nickel foam with 3% hydrochloric acid solution, acetone, anhydrous ethanol, and deionized water for 15 min to remove impurities and oil stains), and vacuum dried at 60°C for 6h, with a loading of about 1 mg / cm 2 to obtain a g-C3N4-FeNiMnCo / NF electrode.

[0032] To evaluate the hydrogen production performance of the prepared g-C3N4-FeNiMnCo / NF electrode, we tested the working electrode prepared above on an electrochemical workstation at room temperature using a standard three-electrode system. In terms of test environment, 1.0 M KOH solution (strong alkaline environment) was used as the electrolyte to simulate the actual working conditions of current industrial water electrolysis. The working electrode used the g-C3N4-FeNiMnCo / NF electrode prepared above, the counter electrode used a carbon rod, and the reference electrode used a Hg / HgO electrode. All test potentials were converted to potentials relative to the reversible hydrogen electrode according to the Nernst equation. The test methods included LSV, EIS, CV, etc. The catalytic activity and onset potential of the hydrogen evolution reaction were evaluated by linear sweep voltammetry (LSV). At the same time, the electrochemical active area and charge transfer rate of the electrode were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy, respectively.

[0033] As you can see from Table 1, the current density of the electrode prepared from sample 3 obtained in this embodiment was tested to be 10 mA / cm 2 , the HER overpotential was 159 mV, and the ECSA was 74.75 cm 2 / mg.

[0034] Example 2

[0035] A nanoneedle-shaped g-C3N4-FeNiMnCo composite material and a preparation method thereof, the preparation method comprising:

[0036] (1) Preparation of g-C3N4, the steps being the same as steps (1) of Example 1.

[0037] (2) Hydrothermal preparation of g-C3N4-FeNiMnCo composite material.

[0038] 0.1 mmol of g-C3N4 was dispersed in 40 ml of deionized water and ultrasonicated for 30 min. 0.5 mmol of Fe (NO3)3·9H2O, 0.5 mmol of Ni(NO3)2·6H2O, 0.05 mmol of Co(NO3)2·6H2O, and 0.01 mmol of MnSO4·H2O were dissolved in deionized water under stirring, and stirred for 2 h. 1.5 mmol of NH4F was added for defect etching process, and the mixed solution was transferred to a 100 ml hydrothermal reactor, reacted at 120°C for 12 h, and then centrifuged to collect the precipitate. The precipitate was washed with deionized water and ethanol alternately for 3 times, and dried at 80°C for 12 h to obtain a nanoneedle-shaped g-C3N4-FeNiMnCo composite material, which was denoted as sample 1.

[0039] The sample 1 nanoneedle-shaped g-C3N4-FeNiMnCo composite material obtained in the embodiment is used to prepare an electrode, and test results show that the current density is 10 mA / cm 2 , the HER overpotential is 240 mV, and the ECSA is 48.25 cm 2 / mg.

[0040] Embodiment 3

[0041] A nanoneedle-shaped g-C3N4-FeNiMnCo composite material and a preparation method thereof, the preparation method comprising:

[0042] (1) preparing g-C3N4, the steps being the same as steps (1) of embodiment 1.

[0043] (2) preparing g-C3N4-FeNiMnCo composite material by a hydrothermal method.

[0044] 0.1 mmol of g-C3N4 is dispersed in 40 ml of deionized water and ultrasonically treated for 30 min. 0.5 mmol of Fe (NO3)3·9H2O, 0.5 mmol of Ni(NO3)2·6H2O, 0.05 mmol of Co(NO3)2·6H2O and 0.03 mmol of MnSO4·H2O are dissolved in deionized water under stirring, and stirred for 2 h. 1.5 mmol of NH4F is added to perform a defect etching process. The mixed solution is transferred to a 100 ml hydrothermal reactor, and reacted at 120°C for 12 h. Then, the precipitate is collected by centrifugation, washed with deionized water and ethanol alternately for 3 times, and dried at 80°C for 12 h to obtain a nanoneedle-shaped g-C3N4-FeNiMnCo composite material, which is recorded as sample 2.

[0045] The sample 2 nanoneedle-shaped g-C3N4-FeNiMnCo composite material obtained in the embodiment is used to prepare an electrode, and test results show that the current density is 10 mA / cm 2 , the HER overpotential is 217 mV, and the ECSA is 50.75 cm 2 / mg.

[0046] Embodiment 4

[0047] A nanoneedle-shaped g-C3N4-FeNiMnCo composite material and a preparation method thereof, the preparation method comprising:

[0048] (1) preparing g-C3N4, the steps being the same as steps (1) of embodiment 1.

[0049] (2) preparing g-C3N4-FeNiMnCo composite material by a hydrothermal method.

[0050] Take 0.1 mmol g-C3N4 dispersed in 40 ml deionized water, ultrasonic 30 min. Add 0.5 mmol Fe (NO3)3·9H2O, 0.5 mmol Ni(NO3)2·6H2O, 0.05 mmol Co(NO3)2·6H2O, 0.05 mmol MnSO4·H2O in deionized water under stirring, stirring for 2 h, adding 1.5 mmol NH4F to etch the defect process, transfer the mixed solution to 100 ml hydrothermal reactor, react at 120℃ for 8h, then centrifugal collection of precipitate, washed with deionized water and ethanol alternately 3 times, 80℃ drying 12h, get nanometer needle g-C3N4-FeNiMnCo composite material, recorded as sample 4.

[0051] The sample 4 nanometer needle g-C3N4-FeNiMnCo composite material obtained by the example is used to prepare an electrode, and the test shows that the current density is 10 mA / cm 2 , the HER overpotential is 245 mV, and the ECSA is 47 cm 2 / mg.

[0052] Example 5

[0053] A nanometer needle g-C3N4-FeNiMnCo composite material and a preparation method thereof, the preparation method comprising:

[0054] (1) preparing g-C3N4, the steps are the same as step (1) of example 1.

[0055] (2) hydrothermal method for preparing g-C3N4-FeNiMnCo composite material.

[0056] Take 0.1 mmol g-C3N4 dispersed in 40 ml deionized water, ultrasonic 30 min. Add 0.5 mmol Fe (NO3)3·9H2O, 0.5 mmol Ni(NO3)2·6H2O, 0.05 mmol Co(NO3)2·6H2O, 0.05 mmol MnSO4·H2O in deionized water under stirring, stirring for 2 h, adding 1.5 mmol NH4F to etch the defect process, transfer the mixed solution to 100 ml hydrothermal reactor, react at 120℃ for 8h, then centrifugal collection of precipitate, washed with deionized water and ethanol alternately 3 times, 80℃ drying 12h, get nanometer needle g-C3N4-FeNiMnCo composite material, recorded as sample 4.

[0057] The sample 5 nanometer needle g-C3N4-FeNiMnCo composite material obtained by the example is used to prepare an electrode, and the test shows that the current density is 10 mA / cm 2The HER overpotential was 225 mV and the ECSA was 50.5 cm 2 / mg.

[0058] Table 1. Performance test of samples obtained in each example

[0059]

[0060] The above embodiments are preferred embodiments of the present application, but the present application is not limited to the above embodiments, and any obvious improvement, replacement or modification made by those skilled in the art without departing from the essential content of the present application shall fall within the protection scope of the present application.

Claims

1. A method for preparing a nano needle-shaped g-C3N4-FeNiMnCo composite material, characterized in that, Comprising the following steps: (1) Preparation of g-C3N4: Take urea into a crucible, and program the temperature to calcination temperature in a muffle furnace. After calcination, grind the yellow powder after natural cooling. Wash the product with deionized water several times, and dry in vacuum to obtain pure g-C3N4; (2) Preparation of g-C3N4-FeNiMnCo composite material by hydrothermal method: Take g-C3N4 and disperse in deionized water, and ultrasonic dispersion. Add Fe(NO3)3·9H2O, Ni(NO3)2·6H2O, Co(NO3)2·6H2O, and MnSO4·H2O into deionized water under stirring condition, and stir. Add NH4F to etch defects, transfer the mixed solution to a hydrothermal reactor, and perform hydrothermal reaction. After reaction, centrifugal collect the precipitate, wash with deionized water and ethanol alternately for several times, and dry to obtain nano-needle-shaped g-C3N4-FeNiMnCo composite material.

2. The production method according to claim 1, wherein In step (1), the calcination temperature is 550℃, the calcination time is 4h, and the heating rate is 5℃ / min; the vacuum drying temperature is 80℃, and the time is 12h.

3. The production method according to claim 1, wherein In step (2), the amount ratio of g-C3N4, deionized water, Fe(NO3)3·9H2O, Ni(NO3)2·6H2O, Co(NO3)2·6H2O, MnSO4·H2O, and NH4F is 0.1mmol:40mL:0.5mmol:0.5mmol:0.05mmol:0.01~0.05mmol:1.5mmol.

4. The production method according to claim 1, wherein In step (2), the ultrasonic dispersion time is 30min; and the stirring time is 2h.

5. The production method according to claim 1, wherein In step (2), the hydrothermal reaction temperature is 110-130℃, and the time is 8-12h.

6. The production method according to claim 1, wherein In step (2), the drying temperature is 80℃, and the time is 12h.

7. Use of the nano-needle-shaped g-C3N4-FeNiMnCo composite material prepared by the preparation method of any one of items 1-6 to make an electrode for electrolysis of water to produce hydrogen.

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