Carbon-based composite material based on leather collagen as well as preparation method and application of carbon-based composite material

Abstract

The invention discloses a leather collagen-based carbon-based composite material as well as a preparation method and application thereof, and the method comprises the following steps: uniformly mixing metal cations (Ti < 4 + >, Al < 3 + >, Co < 2 + > and the like) with leather collagen fibers by an inorganic tanning method to obtain precursor powder; placing the precursor powder in a high-temperature tube furnace, calcining at 600-1000 DEG C under the protection of inert gas, and etching through inorganic acid to obtain a carbon fiber material; and uniformly mixing the carbon fiber material with molybdenum salt, and carrying out heat treatment at 600-1000 DEG C to obtain the molybdenum carbide / carbon fiber composite material. According to the method disclosed by the invention, an organic carbon skeleton formed by heat treatment of the leather collagen fibers is utilized to carbonize a molybdenum source, and in-situ nitrogen doping is realized based on rich functional groups on the side chain of collagen, so that good hydrogen evolution reaction activity of the material is favorably realized. Meanwhile, the method disclosed by the invention develops a new application field for leather collagen fiber resources mainly used in the leather industry.

Description

Technical Field

[0001] The present invention belongs to the field of energy, and relates to a preparation method of a carbon-based composite material, in particular to a carbon fiber / molybdenum carbide composite material and its preparation method and application. Background Art

[0002] Hydrogen energy has many advantages such as high combustion calorific value, wide utilization forms, and environmental friendliness, and will play a crucial role in the future energy landscape. In the process of hydrogen energy development and utilization, hydrogen production in the upstream of the industry is crucial for promoting the development of the hydrogen economy. At present, the main industrial hydrogen production routes include hydrogen production from fossil fuels, hydrogen production from chemical raw materials, and hydrogen production by electrolysis of water. Compared with other hydrogen production processes, hydrogen production by the hydrogen evolution reaction in the cathode process of electrolysis of water has the advantages of rich sources, simple equipment, no pollutant emission in the preparation process, and high purity of the obtained hydrogen. In recent years, combining the electrolysis of water hydrogen production process with renewable energy power generation technologies (such as wind power generation or photovoltaic power generation, etc.) can effectively consume surplus valley electricity and make up for the deficiencies of the fluctuations of wind power and photovoltaic power, which not only improves the energy utilization rate but also effectively alleviates the energy consumption problem of electrolysis of water hydrogen production. Platinum group materials are ideal hydrogen evolution catalysts, but their high price and rare reserves greatly limit the large-scale application of electrolysis of water hydrogen production technology. Therefore, the development of economical, efficient, and stable non-precious metal hydrogen evolution catalytic materials is of great significance for promoting the practical application process of electrolysis of water hydrogen production.

[0003] Molybdenum carbide (Mo2C) is an interstitial compound formed by filling carbon atoms into the lattice interstices of molybdenum. Due to the hybridization of the s and p orbitals of carbon atoms with the d orbitals of the metal, the d band is broadened, endowing Mo2C with a platinum-like electronic structure. In 2012, the research group of Professor Xile Hu at the Swiss Federal Institute of Technology in Lausanne discovered that molybdenum carbide exhibits good catalytic performance and stability for the hydrogen evolution reaction. Since then, this type of material has begun to stand out in the field of electrocatalytic hydrogen evolution. The synthesis methods of Mo2C include temperature-programmed reduction method (generally, using oxides of Mo to react with reducing gases such as CH4, H2, CO, etc. at a temperature of about 1000 °C according to a set program), vacuum in-situ carbothermal reduction method (generally, first forming a precursor containing metal and organic matter by chemical method or simply mechanical mixing method, and an oxidation-reduction reaction occurs between the molybdenum source and the carbon source during the high-temperature reaction of the precursor under vacuum conditions), etc. Common types of carbon sources include methane, phenolic resin, and biomass carbon sources, etc. Compared with carbon sources such as methane and phenolic resin, renewable natural biomass resources have the characteristics of rich sources, easy access, and environmental friendliness. Its molecular skeleton is mainly composed of carbon elements, and the corresponding carbon materials can be directly obtained through high-temperature carbonization. Leather collagen fibers mainly come from the skins of livestock animals such as cattle, sheep, and pigs. The basic structural unit, the collagen molecule, is a triple helix composed of three peptide chains. Hydrogen bonds formed between the peptide groups of each helix connect the three helices together to form a collagen molecule. Multiple collagen molecules are connected end to end and arranged in parallel in a 1 / 4 staggered structure to form collagen microfibrils, and multiple collagen microfibrils further aggregate into collagen fibrils and collagen fibers with a larger diameter. It can be said that leather collagen fibers themselves are a network structure with a special chemical structure and supramolecular structure, which is incomparable to many synthetic polymer materials.

[0004] Continuously developing and sustainably utilizing biomass is a topic of great significance. The main application field of traditional animal skin resources is the leather industry, but its utilization rate is still less than 50% of the resource volume. The scientific laws hidden in leather chemistry indicate that the future utilization value of leather collagen can far exceed the scope of leather making and can have an important impact on the technological development of many fields. Utilizing animal skin resources to construct high-performance catalytic materials is of great significance for both the non-leather application of leather collagen fiber resources and the development of non-precious metal hydrogen evolution catalytic materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method for synthesizing molybdenum carbide / carbon fiber composite materials using natural biomass leather collagen fibers and its application in the field of electrocatalytic hydrogen production, which solves the problem of the generation and emission of harmful gases accompanied by traditional molybdenum carbide synthesis methods. This method uses the organic carbon skeleton formed by the heat treatment of leather collagen fibers to carbonize the molybdenum source, and realizes in-situ nitrogen doping based on the rich functional groups on the collagen side chains, which helps to achieve good hydrogen evolution reaction activity of the material.

[0006] To achieve the above object, the present invention provides a method for preparing a molybdenum carbide / carbon fiber composite material, which method comprises: achieving uniform mixing of metal cations (Ti 4+ 、Al 3+ 、Co 2+ etc.) and skin collagen fibers through an inorganic tanning method to obtain a precursor powder; placing the precursor powder in a high-temperature tube furnace, calcining at 600-1000 °C under inert gas protection and etching with an inorganic acid to obtain a carbon fiber material; uniformly mixing the carbon fiber material with a molybdate and performing heat treatment at 600-1000 °C to obtain a molybdenum carbide / carbon fiber composite material.

[0007] Preferably, in the preparation process of the precursor powder, the metal salt is selected from one or two of titanium sulfate, titanium chloride, aluminum sulfate, aluminum chloride, cobalt sulfate, and cobalt chloride.

[0008] Preferably, in the preparation process of the precursor powder, the dosage of the metal salt is 5-20 g, the dosage of the skin collagen fiber is 5-20 g, and the dosage of the solvent deionized water is 200-600 ml.

[0009] Preferably, in the preparation process of the precursor powder, the pH of the solution system is first adjusted to 1-3 with one of sulfuric acid, hydrochloric acid, and nitric acid, and then adjusted to 4-6 with one of sodium hydroxide, sodium bicarbonate, and ammonia water.

[0010] Preferably, in the preparation process of the precursor powder, the reaction temperature is 20-100 °C and the reaction time is 2-24 h.

[0011] Preferably, in the preparation process of the carbon fiber material, the calcination temperature is 600-1000 °C, the heating rate is 3-10 °C / min, and the calcination time is 1-4 h. More preferably, the calcination temperature is 800-1000 °C, the heating rate is 3-8 °C / min, and the calcination time is 2-4 h.

[0012] Preferably, in the preparation process of the carbon fiber material, the inorganic acid etching is selected from one of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid, and the etching time is 2-24 h. More preferably, the inorganic acid is selected from one of hydrochloric acid or hydrofluoric acid, and the etching time is 8-24 h.

[0013] Preferably, in the preparation process of the molybdenum carbide / carbon fiber composite material, the mass ratio of carbon fiber to ammonium molybdate is (1-3):(4-7).

[0014] Preferably, in the preparation process of the molybdenum carbide / carbon fiber composite material, the heat treatment temperature is 600-1000 °C, the heating rate is 3-10 °C / min, and the heat treatment time is 1-4 h. More preferably, the heat treatment temperature is 800-1000 °C, the heating rate is 3-8 °C / min, and the heat treatment time is 2-4 h.

[0015] Another object of the present invention is to provide the application of the molybdenum carbide / carbon fiber composite material in electrocatalytic hydrogen evolution.

[0016] For the molybdenum carbide / carbon fiber composite material, its preparation method and application of the present invention, compared with the prior art, the present invention has the following beneficial effects: using natural biomass skin collagen fiber as the carbon source is more green and environmentally friendly than traditional organic carbon sources, and at the same time promotes the high-value utilization of animal skin resources; the skin collagen fiber after inorganic tanning can maintain its special microstructure after high-temperature calcination, and the formed carbon fiber can improve the conductivity of the material; in-situ nitrogen doping is realized based on the rich functional groups on the collagen side chain, which helps to achieve good hydrogen evolution reaction activity of the material. Description of the Drawings

[0017] Figure 1 shows XRD pattern of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention.

[0018] Figure 2 XRD pattern of the material prepared in Comparative Example 1 of the present invention.

[0019] Figure 3 Raman spectrum of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention.

[0020] Figure 4 Raman spectrum of the material prepared in Comparative Example 2 of the present invention.

[0021] Figure 5 TEM image of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention.

[0022] Figure 6 XPS image of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention.

[0023] Figure 7 Hydrogen evolution polarization curve of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention.

[0024] Figure 8 Tafel curve of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention. Detailed Embodiments

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] Embodiment 1: A method for preparing a molybdenum carbide / carbon fiber composite material, the method comprising:

[0027] Weigh 15 g of hide collagen fibers and disperse them in 400 mL of ultrapure water. Dropwise add hydrochloric acid to adjust the pH to 1.8 - 2.0, then add 15 g of titanium sulfate and 15 g of cobalt sulfate. React for 6 h under stirring, then dropwise add sodium bicarbonate to adjust the pH to 3.8 - 4.0, and continue to react at 40˚C for 12 h. After filtration, washing, and drying, a precursor powder is obtained. Heat the obtained precursor to 800˚C at a rate of 3˚C / min in argon and hold for 2 h, then etch with hydrofluoric acid for 24 h. After filtration, washing, and drying, a carbon fiber material is obtained. Weigh 1 g of the obtained carbon fiber material and 2 g of ammonium heptamolybdate, grind them in an agate mortar for 0.5 h, then place them in a tube furnace, heat to 800˚C at a rate of 3˚C / min in argon and hold for 2 h to obtain the molybdenum carbide / carbon fiber composite material.

[0028] Comparative Example 1: A method for preparing a composite material, the method comprising:

[0029] Weigh 15 g of hide collagen fibers and disperse them in 400 mL of ultrapure water. Dropwise add hydrochloric acid to adjust the pH to 1.8 - 2.0, then add 15 g of titanium sulfate and 15 g of cobalt sulfate. React for 6 h under stirring, then dropwise add sodium bicarbonate to adjust the pH to 3.8 - 4.0, and continue to react at 40˚C for 12 h. After filtration, washing, and drying, a precursor powder is obtained. Heat the obtained precursor to 800˚C at a rate of 3˚C / min in argon and hold for 2 h, then etch with hydrofluoric acid for 24 h. After filtration, washing, and drying, a carbon fiber material is obtained. Weigh 1 g of the obtained carbon fiber material and 2 g of ammonium heptamolybdate, grind them in an agate mortar for 0.5 h, then place them in a tube furnace, heat to 600˚C at a rate of 3˚C / min in argon and hold for 2 h to obtain the molybdenum carbide / carbon fiber composite material.

[0030] Comparative Example 2: A method for preparing a composite material, the method comprising:

[0031] Weigh 15 g of skin collagen fibers and disperse them into 400 mL of ultrapure water. Dropwise add hydrochloric acid to adjust the pH to 1.8 - 2.0, then add 15 g of titanium sulfate. React for 6 h under stirring, then dropwise add sodium bicarbonate to adjust the pH to 3.8 - 4.0, and continue to react at 40˚C for 12 h. After filtration, washing, and drying, a precursor powder is obtained. Heat the obtained precursor in argon at a rate of 3˚C / min to 800˚C and hold for 2 h, then etch with hydrofluoric acid for 24 h. After filtration, washing, and drying, a carbon fiber material is obtained. Weigh 1 g of the obtained carbon fiber material and 2 g of ammonium heptamolybdate, grind them in an agate mortar for 0.5 h, then place them in a tube furnace, heat in argon at a rate of 3˚C / min to 800˚C and hold for 2 h to obtain a molybdenum carbide / carbon fiber composite material.

[0032] Experimental Example 1: Phase Testing

[0033] Perform phase detection on the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention. As As shown in Figure 1 shown, it is the XRD pattern of the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention. It can be seen from the figure that diffraction peaks of the (100), (002), (101), (102), (110), (103), (200), (112), and (201) crystal planes belonging to hexagonal molybdenum carbide (Mo2C, PDF#35 - 0787) are observed at 2θ = 34.35°, 37.98°, 39.39°, 52.12°, 61.53°, 69.57°, 72.38°, 74.65°, and 75.51° respectively. The XRD results indicate that the crystalline phase component in the material is molybdenum carbide. Since the main form of carbon is amorphous carbon, no diffraction peaks belonging to carbon fibers appear in the XRD.

[0034] As Figure 2 shown, it is the XRD pattern of the material prepared in Comparative Example 1 of the present invention. It can be seen from the figure that there are diffraction peaks of molybdenum dioxide (MoO2).

[0035] From the comparison of the materials prepared in Example 1 and Comparative Example 1, it can be known that to prepare the molybdenum carbide / carbon fiber composite material of the present invention, an appropriate heat treatment reaction temperature must be selected. If the temperature is too low, only the high - valence oxide of molybdenum can be reduced to obtain a low - valence oxide, and a sufficient carbonization reaction to form molybdenum carbide cannot occur.

[0036] Experimental Example 2: Raman Spectrum Testing

[0037] Perform Raman spectrum detection on the molybdenum carbide / carbon fiber composite material prepared in Example 1 of the present invention. As Figure 3As shown, it is the Raman spectrum of the molybdenum carbide / carbon fiber composite prepared in Example 1 of the present invention. It can be seen from the figure that obvious Raman characteristic peaks of carbon materials appear at Raman shifts of 1340 cm -1 and 1590 cm -1 positions. The D peak at 1340 cm -1 is the valley scattering between a phonon and a defect, and the G peak at 1590 cm -1 is generated by the in-plane vibration of carbon atoms sp 2 . The I G / I D value of the material can be calculated from the Raman spectrum. A large I G / I D value means that the carbon in the sample has a higher degree of graphitization. The I G / I D value of the molybdenum carbide / carbon fiber composite prepared in Example 1 is 1.06.

[0038] As Figure 4 shown, it is the Raman spectrum of the material prepared in Comparative Example 2 of the present invention. It can be seen from the figure that the I G / I D value of this material is 0.91.

[0039] From the comparison of the materials prepared in Example 1 and Comparative Example 2, it can be known that if a molybdenum carbide / carbon fiber composite with a higher degree of graphitization is to be prepared, a metal cobalt salt with a graphitization catalytic effect needs to be added to the raw materials.

[0040] Experimental Example 3 Morphology Test

[0041] The transmission electron microscope was used to observe the microscopic morphology of the molybdenum carbide / carbon fiber composite. As Figure 5 shown, it is the TEM image of the molybdenum carbide / carbon fiber composite prepared in Example 1 of the present invention. It can be seen from the figure that the material is mainly composed of carbon fibers with a diameter of about 100 nm and molybdenum carbide crystal particles with a particle size of about 6 nm. The carrier effect of carbon fibers provides the necessary conditions for the nanosizing and uniform distribution of molybdenum carbide, and the nanosized material helps to fully expose enough hydrogen evolution active sites.

[0042] Experimental Example 4 Surface State Test

[0043] The X-ray photoelectron spectroscopy was used to observe the microscopic morphology of the molybdenum carbide / carbon fiber composite. As Figure 6As shown in the figure, it is the XPS diagram of the molybdenum carbide / carbon fiber composite prepared in Example 1 of the present invention. It can be seen from the figure that the main elements existing on the material surface are Mo, C, N, and O. Among them, the O element is caused by the inevitable oxidation of the carbide in the air, and the N element is derived from the in-situ doping of the rich functional groups on the collagen side chain during the heat treatment process, which helps to achieve good hydrogen evolution reaction activity of the material.

[0044] Experimental Example 5 Electrochemical Hydrogen Evolution Performance Test

[0045] Test conditions: The electrochemical hydrogen evolution performance tests were all carried out on a VersaStat3 type electrochemical workstation. The experiment adopted a typical three-electrode system. A graphite electrode (d = 5 mm) was used as the counter electrode, a saturated calomel electrode (SCE) was used as the reference electrode, and a glassy carbon electrode (GCE, d = 5 mm) loaded with a quantitative catalyst sample was used as the working electrode. The hydrogen evolution activity of the material in an acidic (0.5 M H2SO4) electrolyte was tested.

[0046] Preparation of the working electrode: Weigh 5 mg of the material (the molybdenum carbide / carbon fiber composite prepared in Example 1 of the present invention), disperse it in 500 μL of anhydrous ethanol and deionized water respectively, then add 30 μL of Nafion (5 wt%), and ultrasonicate for 1 h to form a uniform slurry. Then add 10 μL of polyvinylidene fluoride solution (solvent: N-methylpyrrolidone, concentration: 5 wt%), and continue ultrasonication for 1 min to obtain the catalyst slurry. Take 10 μL of the slurry and drop it on the surface of the pre-polished glassy carbon electrode, and let it dry naturally to be used as the working electrode. Among them, the loading area of the catalyst on the electrode is 0.25 mg / cm 2 .

[0047] Catalytic performance test: At the equilibrium potential, since the oxidation rate and reduction rate of the hydrogen electrode are equal, no hydrogen gas will be evolved. Only when there is a cathodic current passing through the electrode so that the reduction reaction rate is much greater than the oxidation reaction rate, will hydrogen gas be evolved. At a certain current density, the difference between the electrode potential and the equilibrium potential is called the overpotential at this current density, denoted by the symbol η. In the field of hydrogen evolution, the internationally common criterion is to evaluate the electrocatalytic hydrogen evolution performance of the material according to the overpotential (η10) at a current density of 10 mA / cm 2 . The smaller η10 is, the smaller the potential required for the catalyst to reach this current density, and the better the electrocatalytic hydrogen evolution performance. The overpotential was tested by linear sweep voltammetry (LSV) at a scanning rate of 5 mV / s, and the obtained curve is called the hydrogen evolution polarization curve.

[0048] The slope of the Tafel curve reveals the kinetic characteristics of the hydrogen evolution reaction. A smaller Tafel slope means a faster hydrogen evolution rate on the electrode modified by the catalyst. The polarization curve is replotted with the overpotential as the ordinate and the logarithm of the absolute value of the current density (log|j|) as the abscissa. Since a large number of hydrogen bubbles are generated at a high overpotential, the curve deviates from the linear region in the high test voltage range. The Tafel slope is determined by the slope of the linear part of the fitted curve. The linear part satisfies the Tafel formula: η = blog j + a, where η is the overpotential, j is the current density, a is the Tafel coefficient, and b is the Tafel slope.

[0049] By evaluating the overpotential at the same current density in the hydrogen evolution polarization curve or the current density achieved at the same overpotential, the catalytic activity of the sample can be intuitively judged. Simply put, the smaller the overpotential required to reach a certain specific current density, the higher the hydrogen evolution efficiency and the lower the required cost; or at the same specific overpotential, the larger the current density achieved, the faster the electron transfer rate and the higher the hydrogen evolution efficiency. From Figure 7 the hydrogen evolution polarization curve diagram, it can be seen that for a current density of 10 mA / cm 2 , the molybdenum carbide / carbon fiber composite material only requires an overpotential of 168 mV.

[0050] The Tafel slope is a commonly used indicator for evaluating the kinetic reaction process of a catalyst. The smaller the Tafel slope, the lower the hydrogen evolution overpotential required to increase the same kinetic current density, the smaller the hydrogen evolution resistance, and the higher the catalytic efficiency. From Figure 8 the Tafel curve diagram, it can be seen that the Tafel slope of the molybdenum carbide / carbon fiber composite material is 59 mV / dec, indicating that the material has a good hydrogen evolution reaction rate.

[0051] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A carbon-based composite material based on skin collagen and its preparation method, characterized in that, It includes the following parts: (1) Mix and react metal salts such as Ti 4+ , Al 3+ , Co 2+ with skin collagen fibers to obtain precursor powder; (2) Place the precursor powder in a high-temperature tube furnace, calcine at 600-1000 °C under the protection of an inert gas and etch with inorganic acid to obtain a carbon fiber material; (3) Uniformly mix the carbon fiber material with molybdenum salt and perform heat treatment at 600-1000 °C to obtain a molybdenum carbide / carbon fiber composite material.

2. The preparation method according to claim 1, characterized in that, In the step (1), the metal salt is selected from one or two of titanium sulfate, titanium chloride, aluminum sulfate, aluminum chloride, cobalt sulfate, and cobalt chloride. The dosage of the metal salt is 5-20 g, the dosage of the skin collagen fiber is 5-20 g, and the dosage of the solvent deionized water is 200-600 ml.

3. The preparation method according to claim 1, characterized in that, In the step (1), in the solution system, first select one of sulfuric acid, hydrochloric acid, and nitric acid to adjust the pH to 1-3, and then select one of sodium hydroxide, sodium bicarbonate, and ammonia water to adjust the pH to 4-6. The reaction temperature is 20-100 °C, and the reaction time is 2-24 h.

4. The preparation method according to claim 1, characterized in that, In the step (2), the heating rate of the calcination is 3-10 °C / min, and the time of the calcination is 1-4 h.

5. The preparation method according to claim 1, characterized in that, In the step (2), the inorganic acid etching selects one of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid, and the etching time is 2-24 h.

6. The preparation method according to claim 1, characterized in that, In the step (3), the mass ratio of the carbon fiber to ammonium molybdate is (1-3):(4-7).

7. The preparation method according to claim 1, characterized in that, In the step (3), the heating rate of the heat treatment is 3-10 °C / min, and the time of the heat treatment is 1-4 h.

8. A molybdenum carbide / carbon fiber composite material prepared by the method according to any one of claims 1-7.

9. Application of the molybdenum carbide / carbon fiber composite material according to claim 8 in electrocatalytic hydrogen evolution.

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