Carbon material containing molybdenum carbide-molybdenum nitride heterostructure and preparation method and application thereof

Abstract

The application discloses a carbon material containing a molybdenum carbide-molybdenum nitride heterostructure and a preparation method and application thereof. The composition of the carbon material containing the molybdenum carbide-molybdenum nitride heterostructure includes a porous carbon matrix and a molybdenum carbide-molybdenum nitride heterostructure layer in-situ grown on the surface of the porous carbon matrix, and the composition of the molybdenum carbide-molybdenum nitride heterostructure layer includes molybdenum carbide and molybdenum nitride. The carbon material containing the molybdenum carbide-molybdenum nitride heterostructure has the advantages of excellent catalytic performance, good structural stability, high mechanical strength and the like when used as an electrode material for water electrolysis hydrogen production, can effectively reduce the energy consumption of water electrolysis hydrogen production and improve the efficiency of water electrolysis hydrogen production, and has the advantages of low production cost, wide raw material sources and simple preparation method, and is suitable for large-scale industrial production and application.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of hydrogen production by electrolysis of water, and particularly relates to a carbon material containing a molybdenum carbide-molybdenum nitride heterostructure and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen has the advantages of light mass, high energy density, high calorific value, no pollution in combustion and the like, and is considered to be one of the most promising energy sources. However, hydrogen energy is not an energy resource that exists in nature in large quantities, but needs to be obtained by artificial production. Among a large number of hydrogen production methods, the method of hydrogen production by electrolysis of water has the advantages of simple preparation process, cleanness, no pollution, and mature technology, and is currently recognized as the best method of hydrogen production in application prospect.

[0003] The reaction of hydrogen production by electrolysis of water (OWS) includes a cathode hydrogen evolution reaction (HER) and an anode oxygen evolution reaction (OER), the HER reaction involves a two-electron transfer process, and the OER reaction involves a four-electron transfer process. At present, the energy consumption of hydrogen production by electrolysis of water is high (the electricity consumption is about 4.5 kWh / Nm 3 H2~5.5 kWh / Nm 3 H2), and the main reason is that the energy barrier of the OER reaction is high, and the reaction kinetics rate is slow, which seriously affects the efficiency of hydrogen production by electrolysis of water. Studies have shown that the use of high-efficiency catalytic electrode materials to reduce the activation energy of the reaction can effectively reduce the energy consumption of hydrogen production by electrolysis of water. Therefore, in the hydrogen production by electrolysis of water, how to improve the activity of the electrode catalytic material, reduce the overpotential of the oxygen evolution reaction and improve the stability of the electrode material is crucial. At present, the commercial electrode material is mainly a noble metal material (for example, a platinum-based material for the HER reaction, and a ruthenium / iridium-based material for the OER reaction), although the catalytic performance of the noble metal material is excellent, but the noble metal elements such as platinum, ruthenium and iridium are limited in the earth, the price fluctuates greatly, the production cost is high, and the long-term stability of the noble metal material at high potential is poor, which seriously limits the large-scale application of the noble metal material in the field of hydrogen production by electrolysis of water.

[0004] Therefore, it is of great significance to develop an electrode material with excellent catalytic performance, good stability, low production cost and wide raw material sources. SUMMARY

[0005] The application aims to provide a carbon material containing a molybdenum carbide-molybdenum nitride heterostructure and a preparation method and application thereof.

[0006] The technical scheme adopted by the application is as follows:

[0007] A carbon material containing a molybdenum carbide-molybdenum nitride heterostructure, which comprises a porous carbon matrix and a molybdenum carbide-molybdenum nitride heterostructure layer in-situ grown on the surface of the porous carbon matrix; the molybdenum carbide-molybdenum nitride heterostructure layer comprises molybdenum carbide and molybdenum nitride.

[0008] A preparation method of the carbon material containing a molybdenum carbide-molybdenum nitride heterostructure as described above comprises the following steps:

[0009] 1) transversely slicing wood, and then carbonizing the wood in a protective atmosphere to obtain porous carbon;

[0010] 2) placing the porous carbon as a working electrode in an electrolyte containing a molybdenum source to perform electrodeposition, thereby obtaining porous carbon with molybdenum oxide in-situ grown on the surface of the porous carbon;

[0011] 3) placing the porous carbon with molybdenum oxide in-situ grown on the surface of the porous carbon and melamine in a protective atmosphere to perform heating and reaction, thereby obtaining the carbon material containing a molybdenum carbide-molybdenum nitride heterostructure.

[0012] Preferably, the wood in step 1) is at least one of shrubs and trees.

[0013] Further preferably, the wood in step 1) is poplar.

[0014] Preferably, the protective atmosphere in step 1) is a nitrogen atmosphere or an argon atmosphere.

[0015] Preferably, the carbonization in step 1) is performed at a temperature of 300-1000°C, and the carbonization time is 1-15h.

[0016] Preferably, the molybdenum source in the electrolyte containing a molybdenum source in step 2) is a molybdenum salt.

[0017] Further preferably, the molybdenum source in the electrolyte containing a molybdenum source in step 2) is at least one of ammonium heptamolybdate, sodium molybdate and molybdenum pentachloride.

[0018] Preferably, the concentration of the molybdenum source in the electrolyte containing a molybdenum source in step 2) is 0.001-3mol / L.

[0019] Preferably, the solvent in the electrolyte containing a molybdenum source in step 2) is at least one of water, ethanol, ethanolamine, diethanolamine, triethanolamine, N,N-dimethylformamide and ethylenediamine.

[0020] Preferably, the electrodeposition in step 2) is performed at a deposition potential of 0V to -2.0V (relative to a reference electrode), and the electrodeposition time is 0.1-10h.

[0021] Preferably, the protective atmosphere in step 3) is a nitrogen atmosphere or an argon atmosphere.

[0022] Preferably, the reaction in step 3) is carried out at a temperature of 200-1000℃, and the reaction time is 0.5-5h.

[0023] The application of the carbon material containing the molybdenum carbide-molybdenum nitride heterostructure as described above in the electrolysis of water to produce hydrogen.

[0024] The carbon material containing the molybdenum carbide-molybdenum nitride heterostructure of the present application has the advantages of excellent catalytic performance, good structural stability, high mechanical strength, etc. when used as an electrode material for the electrolysis of water to produce hydrogen, and can effectively reduce the energy consumption and improve the efficiency of the electrolysis of water to produce hydrogen. Moreover, the production cost is low, the raw material sources are wide, and the preparation method is simple, so it is suitable for large-scale industrial production and application.

[0025] Specifically,

[0026] 1) The composition of the carbon material containing the molybdenum carbide-molybdenum nitride heterostructure of the present application includes a porous carbon matrix and a molybdenum carbide-molybdenum nitride heterostructure layer grown in situ on the surface of the porous carbon matrix. The porous carbon matrix has good electrical conductivity and high specific surface area, and can provide abundant active sites and electron transport channels. The molybdenum carbide-molybdenum nitride heterostructure can improve the activity of the active sites, expose more active sites, and thus improve the electrocatalytic activity. In addition, the performance of the molybdenum carbide-molybdenum nitride heterostructure can be adjusted and optimized by controlling the concentration of the molybdenum source in the electrolyte, the deposition potential and time, and the amount of melamine, and has good repeatability.

[0027] 2) The carbon material containing the molybdenum carbide-molybdenum nitride heterostructure of the present application has a three-dimensional hierarchical porous structure, low-curvature microchannels, adjustable hydrophilicity / hydrophobicity, and good mechanical properties. It has a large electrochemically active area, high intrinsic electrochemical activity, adjusted electronic structure, and reduced water dissociation energy barrier. It can construct an efficient gas-liquid-solid three-phase reaction interface for the electrolysis of water, and the use of wood-based carbon as the substrate is conducive to further reducing the cost of large-scale production.

[0028] 3) The carbon material containing the molybdenum carbide-molybdenum nitride heterostructure of the present application has good structural stability and high mechanical strength, and can effectively resist volume expansion and structural damage, exhibiting excellent electrolysis of water performance and stability.

[0029] 4) The carbon material containing the molybdenum carbide-molybdenum nitride heterostructure of the present application has low production cost, wide raw material sources, and simple preparation method, and is suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flow chart for the preparation of the carbon material containing the molybdenum carbide-molybdenum nitride heterostructure in the present application.

[0031] Figure 2 XRD pattern of Mo2N / Mo2C@CW in Example 1.

[0032] Figure 3 SEM, TEM, SAED and EDS pattern of Mo2N / Mo2C@CW in Example 1.

[0033] Figure 4 HER performance chart of carbon material containing molybdenum carbide-molybdenum nitride heterostructure in Examples 1-5.

[0034] Figure 5 Tafel slope chart of Mo2N / Mo2C@CW in Example 1.

[0035] Figure 6 Nyquist chart of CW and Mo2N / Mo2C@CW in Example 1.

[0036] Figure 7 Electrochemical active area chart of Mo2N / Mo2C@CW in Example 1.

[0037] Figure 8 Water contact angle test result chart of CW and Mo2N / Mo2C@CW in Example 1. DETAILED DESCRIPTION

[0038] The application will be further explained and described with reference to specific examples.

[0039] Example 1:

[0040] A carbon material containing molybdenum carbide-molybdenum nitride heterostructure is prepared by the following method (the preparation flow chart is shown in Figure 1

[0041] 1) Poplar wood is cut into wood pieces with a size of 4 cm x 2 cm x 0.1 cm in transverse direction (perpendicular to the growth direction), washed with water, dried in a forced air drying oven at 80℃ overnight, and then placed in a quartz tube furnace, and heated from room temperature to 500℃ at a heating rate of 5℃ / min, kept for 1.5 h, and then heated to 900℃ at a heating rate of 5℃ / min, kept for 1 h, to obtain porous carbon (denoted as CW);

[0042] 2) 1 mmol of (NH4)6Mo7O 24 ​• 4H2O was added to 60 mL of deionized water, stirred and dissolved to prepare a molybdenum salt solution, then porous carbon was used as a working electrode (WE), a Hg / HgO electrode was used as a reference electrode (CE), a carbon rod electrode was used as a counter electrode (RE), the molybdenum salt solution was used as an electrolyte to assemble a three-electrode system, then electricity was passed to deposit at a potential of -0.9 V (relative to the Hg / HgO electrode) for 30 min, then the porous carbon was taken out and washed with deionized water several times, then placed in a blast drying oven at 60°C for 12 h to obtain the porous carbon with molybdenum oxide grown in-situ on the surface (denoted as Mo2O3@CW);

[0043] 3) The porous carbon with molybdenum oxide grown in-situ on the surface was placed in a quartz tube furnace, 0.5 g of melamine was placed upstream of the quartz tube furnace, nitrogen was introduced, then the temperature was raised from room temperature to 500°C at a rate of 5°C / min, and held for 1 h, then the temperature was continued to be raised to 800°C at a rate of 5°C / min, and held for 2 h to obtain the carbon material containing molybdenum carbide-molybdenum nitride heterostructure (denoted as Mo2N / Mo2C@CW).

[0044] Performance test:

[0045] 1) The X-ray diffraction (XRD) pattern of the carbon material containing molybdenum carbide-molybdenum nitride heterostructure (Mo2N / Mo2C@CW) in this example is shown in Figure 2 .

[0046] It can be seen from Figure 2 that the characteristic peaks at 37.4° and 63.1° belong to the diffraction peaks of the (111) and (220) crystal planes of Mo2N respectively, and the characteristic peaks at 34.3° and 39.3° belong to the diffraction peaks of the (021) and (121) crystal planes of Mo2C respectively, indicating that Mo2C-Mo2N heterostructure is indeed contained in Mo2N / Mo2C@CW.

[0047] 2) The scanning electron microscope (SEM) image, transmission electron microscope (TEM) image, selected area electron diffraction (SAED) image and EDS energy spectrum of the carbon material containing molybdenum carbide-molybdenum nitride heterostructure (Mo2N / Mo2C@CW) in this example are shown in Figure 3 (a, b and c are SEM images, d is a TEM image, e is a SAED image, and f, g, h and i are EDS energy spectrum images).

[0048] It can be seen from a, b and c in Figure 3 that the Mo2N-Mo2C heterostructure is uniformly grown in the vertical pipe of the porous carbon (CW);

[0049] It can be seen from d in Figure 3 that the Mo2N / Mo2C@CW contains and The lattice spacing of a belongs to the (121) and (021) crystal planes of Mo2C, respectively, The lattice spacing of a belongs to the (111) crystal plane of Mo2N.

[0050] From the EDS mapping of Fig. 6b, it can be seen that the C, N and Mo elements in Mo2N / Mo2C@CW are uniformly distributed. Figure 3 From the selected area electron diffraction pattern of Fig. 6c, it can be seen that the Mo2N / Mo2C@CW clearly shows the (021) crystal plane of Mo2C and the (111) crystal plane of Mo2N.

[0051] From the EDS mapping of Fig. 6b, it can be seen that the C, N and Mo elements in Mo2N / Mo2C@CW are uniformly distributed. Figure 3 From the EDS mapping of Fig. 6b, it can be seen that the C, N and Mo elements in Mo2N / Mo2C@CW are uniformly distributed.

[0052] Example 2:

[0053] A carbon material containing a molybdenum carbide-molybdenum nitride heterostructure (denoted as Mo2N / Mo2C@CW-0.8V), except that the electrodeposition potential in step 2) is adjusted from "-0.9V" to "-0.8V" during preparation, and the rest is exactly the same as Example 1.

[0054] Example 3:

[0055] A carbon material containing a molybdenum carbide-molybdenum nitride heterostructure (denoted as Mo2N / Mo2C@CW-1.0V), except that the electrodeposition potential in step 2) is adjusted from "-0.9V" to "-1.0V" during preparation, and the rest is exactly the same as Example 1.

[0056] Example 4:

[0057] A carbon material containing a molybdenum carbide-molybdenum nitride heterostructure (denoted as Mo2N / Mo2C@CW-0.4g), except that the amount of melamine in step 3) is adjusted from "0.5g" to "0.4g" during preparation, and the rest is exactly the same as Example 1.

[0058] Example 5:

[0059] A carbon material containing a molybdenum carbide-molybdenum nitride heterostructure (denoted as Mo2N / Mo2C@CW-0.6g), except that the amount of melamine in step 3) is adjusted from "0.5g" to "0.6g" during preparation, and the rest is exactly the same as Example 1.

[0060] Performance test:

[0061] 1) HER performance of the carbon materials containing molybdenum carbide-molybdenum nitride heterostructures in Examples 1-5 (HER performance testing process is as follows: a three-electrode electrochemical cell was assembled using the carbon materials containing molybdenum carbide-molybdenum nitride heterostructures in Examples 1-5 as the working electrode, an Hg / HgO electrode as the reference electrode, a carbon rod electrode as the counter electrode, and a 1 mol / L KOH solution as the electrolyte. The test was then performed using a CHI660E electrochemical workstation). (See figure below.) Figure 4 (A commercial Pt / C electrode is used for comparison, denoted as Pt / C@CW) is shown.

[0062] Depend on Figure 4 As can be seen from a, the Mo2N / Mo2C@CW in Example 1 only requires an ultra-low overpotential of 193mV to achieve 100mA·cm. -2 The current density is superior to that of Mo2N / Mo2C@CW-0.8V(η) in Example 2. 100 =234mV), Mo2N / Mo2C@CW-1.0V in Example 3 (η 100 =324mV) and commercial Pt / C electrodes (η 100 =267mV);

[0063] Depend on Figure 4 As can be seen from b, the Mo2N / Mo2C@CW in Example 1 only requires an ultra-low overpotential of 193mV to obtain 100mA·cm. -2 The current density is superior to that of Mo2N / Mo2C@CW-0.4g(η) in Example 3. 100 =291mV) and Mo2N / Mo2C@CW-0.6g (η) in Example 4 100 =248mV).

[0064] 2) The Tafel slope diagram of the carbon material (Mo2N / Mo2C@CW) with a molybdenum carbide-molybdenum nitride heterostructure in Example 1 is shown below. Figure 5 (A commercial Pt / C catalyst is used as a comparison, denoted as Pt / C) is shown.

[0065] Depend on Figure 5 It can be seen that Mo2N / Mo2C@CW exhibits a value of 96 mV·dec -1 The Tafel slope is slightly lower than that of commercial Pt / C catalysts (161 mV·dec). -1 ).

[0066] 3) The Nyquist plots of the porous carbon (denoted as CW) and the carbon material containing a molybdenum carbide-molybdenum nitride heterostructure (Mo2N / Mo2C@CW) in Example 1 are shown below. Figure 6 As shown.

[0067] Depend onFigure 6 It can be seen that Mo2N / Mo2C@CW has extremely low impedance.

[0068] 4) Electrochemical active area diagram of the carbon material (Mo2N / Mo2C@CW) with molybdenum carbide-molybdenum nitride heterostructure in Example 1 (the test procedure is as follows: cyclic voltammetry scans were performed at different scan rates within the selected voltage range using a CHI660E electrochemical workstation, and the obtained curves are shown below). Figure 7 'a' in the middle, from Figure 7 By selecting a certain voltage in 'a' and calculating the corresponding two currents, the electrochemically active surface area can be obtained, and the graph is shown below. Figure 7 b) in Figure 7 As shown.

[0069] Depend on Figure 7 It can be seen that Mo2N / Mo2C@CW exhibits a high double-layer capacitance (C dl =38.51mF·cm -2 This corresponds to a higher electrochemical active area.

[0070] 5) The water contact angle test results of the porous carbon (denoted as CW) and the carbon material containing molybdenum carbide-molybdenum nitride heterostructure (Mo2N / Mo2C@CW) in Example 1 are shown in the figure below. Figure 8 As shown.

[0071] Depend on Figure 8 It can be seen that CW exhibits a water contact angle of 120°, while Mo2N / Mo2C@CW exhibits a hydrophilic angle of 0°, indicating that Mo2N / Mo2C@CW has excellent hydrophilicity.

[0072] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for producing a carbon material containing a molybdenum carbide-molybdenum nitride heterostructure, characterized by, The method comprises the following steps: 1) cutting wood into transverse slices and carbonizing the wood in a protective atmosphere to obtain porous carbon; 2) placing the porous carbon as a working electrode in an electrolyte containing a molybdenum source to perform electrodeposition, thereby obtaining porous carbon with molybdenum oxide in-situ grown on the surface of the porous carbon; 3) placing the porous carbon with molybdenum oxide in-situ grown on the surface of the porous carbon and melamine in a protective atmosphere and heating to perform a reaction, thereby obtaining carbon material containing molybdenum carbide-molybdenum nitride heterostructures; The electrodeposition in step 2) is performed under the condition that the deposition potential is 0V to -2.0V, and the electrodeposition time is 0.1h to 10h. The reaction in step 3) is performed under the condition that the temperature is 200℃ to 1000℃, and the reaction time is 0.5h to 5h. The composition of the carbon material containing molybdenum carbide-molybdenum nitride heterostructures comprises a porous carbon matrix and a molybdenum carbide-molybdenum nitride heterostructure layer in-situ grown on the surface of the porous carbon matrix; the composition of the molybdenum carbide-molybdenum nitride heterostructure layer comprises molybdenum carbide and molybdenum nitride.

2. The method of claim 1, wherein: The wood in step 1) is at least one of shrubs and trees.

3. The production method according to claim 1 or 2, characterized by: The carbonization in step 1) is performed under the condition that the temperature is 300℃ to 1000℃, and the carbonization time is 1h to 15h.

4. The method of claim 1, wherein: The molybdenum source in the electrolyte containing a molybdenum source in step 2) is a molybdenum salt.

5. The production method according to claim 1 or 4, characterized by: The concentration of the molybdenum source in the electrolyte containing a molybdenum source in step 2) is 0.001mol / L to 3mol / L.

6. The method of claim 1 or 4, wherein: Step 2) the solvent in the electrolyte containing the molybdenum source is at least one of water, ethanol, ethanolamine, diethanolamine, triethanolamine, N,N dimethylformamide, ethylenediamine.

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