A bifunctional in-doped Ni2Mo3N@Mo2C binary heterojunction catalyst, a preparation method and application thereof

Abstract

The application discloses a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst and a preparation method and application thereof. A dimethyl imidazole solution is slowly added into a Mo salt solution to obtain a suspension liquid containing a Mo metal organic framework Mo-MOF; the suspension liquid is left to stand, and a precipitate is centrifuged and washed, and vacuum dried to obtain the Mo-MOF containing the Mo metal organic framework; a Ni salt, an In salt and the Mo-MOF are added into an anhydrous ethanol solution to perform ion exchange, and the precursor is vacuum dried to obtain the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst. The catalyst material has excellent basic oxygen evolution and urea oxidation activity, and has a good application prospect in electrocatalytic decomposition of water, urea-assisted electrolysis of water and treatment of sewage containing urea.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocatalysis, and particularly relates to a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst, a preparation method and application thereof. BACKGROUND

[0002] The continuous increase of global carbon emissions and the increasingly severe global energy crisis have prompted people to urgently seek sustainable clean energy to replace fossil fuels. Hydrogen is widely concerned due to its high conversion rate and non-polluting combustion characteristics. Compared with traditional hydrogen production technology, electrocatalytic hydrogen production is considered an ideal method due to its high purity and high efficiency of hydrogen production. Electrocatalytic water splitting includes two half-reactions: hydrogen evolution reaction (2H2O + 4e - → 2H2 + 2OH - ) at the cathode and oxygen evolution reaction (4OH - → O2 + 2H2O + 4e - ) at the anode. However, the inherent slow kinetic characteristics of the electrocatalytic oxygen evolution reaction (OER) make the overall energy conversion efficiency of water splitting relatively low. Therefore, reasonably designing efficient OER electrocatalysts and developing alternative anode oxidation catalysts are the key to improving the efficiency of electrocatalytic hydrogen production.

[0003] The thermodynamic equilibrium potential of urea electro-oxidation reaction (UOR, 0.37 V vs. RHE) is much lower than that of OER (1.23 V vs. RHE), which is proved to be a promising anode reaction. Therefore, urea-assisted water electrolysis not only helps to save energy for hydrogen production, but also provides a green and sustainable strategy for wastewater management. Although UOR has a lower thermodynamic advantage than OER in alkaline solution, UOR (UOR: CO(NH2)2 + 6OH - → N2 + 5H2O + CO2 + 6e - ) is a complex 6-electron transfer process, and its kinetics is relatively slow. Some noble metal catalysts (such as IrO2 and RuO2 for OER; Pt and Pd for UOR) are widely used due to their excellent electrocatalytic activity, but their scarcity, high cost and single function limit their large-scale application. Therefore, developing bifunctional catalysts for high-performance OER and UOR to replace noble metal catalysts is a necessary way to achieve clean hydrogen production. SUMMARY

[0004] In order to solve the above-mentioned defects existing in the prior art, the purpose of the present application is to provide a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst as well as a preparation method and application thereof. The catalyst prepared by the method exhibits excellent catalytic performance in the water electrolysis oxygen evolution reaction, and the oxygen evolution overpotential is significantly lower than that of a commercial RuO2 catalyst. The material also exhibits excellent catalytic activity for the urea catalytic oxidation reaction. The use of non-noble metals as active components greatly reduces the preparation cost, and has significant economic benefits.

[0005] The present application is realized by the following technical solutions.

[0006] In one aspect of the present application, a preparation method of a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst is provided, which comprises the following steps:

[0007] a. Dissolve dimethylimidazole in a mixed solution of anhydrous ethanol and methanol to obtain a dimethylimidazole solution; dissolve Mo salt in a mixed solution of anhydrous ethanol and methanol to obtain a Mo salt solution;

[0008] b. At room temperature, slowly add the dimethylimidazole solution to the Mo salt solution at a molar ratio of dimethylimidazole to Mo element of (9-11):(0.9-1.1), stir to obtain a suspension containing Mo metal organic framework Mo-MOF; let the suspension stand, remove the supernatant, centrifuge and wash the precipitate, vacuum dry the obtained solid to obtain Mo-MOF containing Mo metal organic framework;

[0009] c. Add Ni salt, In salt and Mo-MOF to an anhydrous ethanol solution at a molar ratio of Ni element to In element of (0.9-1):(0.9-1) and a ratio of the sum of the mass of Ni element and In element to the mass of Mo-MOF of (0.35-0.75):1, stir for ion exchange, wash, centrifuge and vacuum dry to obtain a precursor;

[0010] d. Calcine the precursor under a protective atmosphere, and naturally cool to room temperature to obtain a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst.

[0011] Preferably, the molybdenum salt is one of MoCl5 or MoCl3.

[0012] Preferably, the Ni salt is one of NiCO3, Ni(NO2)2, NiSO4, NiCl2 or Ni(NO3)2.

[0013] Preferably, the In salt is one of In(NO3)3, InCl3 or In2(SO4)3.

[0014] As preferred, in step a, the volume ratio of anhydrous ethanol to methanol is 1:1, and the concentration of the Mo salt solution is 0.03-0.05 mol / L.

[0015] As preferred, in step b, the suspension is centrifuged after standing for 10-15 hours to remove the supernatant, and the obtained solid is washed with anhydrous ethanol by centrifugation for 3-4 times, and then vacuum dried for 2-5 hours.

[0016] As preferred, in step c, the ion exchange is performed for 5-8 hours, the centrifugal washing is performed for 2-3 times, and the vacuum drying is performed at 50-60℃ for 2-5 hours.

[0017] As preferred, in step d, the protective atmosphere is a mixed gas of 5% hydrogen and 95% argon.

[0018] As preferred, in step d, the calcination temperature is 750-850℃, the temperature rising speed is 3-5℃ / min, and the holding time is 3-6 hours.

[0019] In another aspect of the present application, a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst prepared by the above method is provided.

[0020] The present application has the following beneficial effects due to the above technical solutions:

[0021] 1. The ion exchange reaction is performed on the Mo-MOF precursor, so that the elements are uniformly distributed, and the Ni2Mo3N and Mo2C components are uniformly dispersed, which is beneficial to obtain an interface-rich heterojunction catalyst for the formed bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst (In-Ni2Mo3N@Mo2C heterojunction catalyst), and promotes the alkaline electrolytic water oxygen evolution reaction and the urea catalytic oxidation reaction.

[0022] 2. The In-Ni2Mo3N@Mo2C binary heterojunction constructed by the present application adjusts the electronic structure of the material due to the doping of In, accelerates the reaction kinetics, and is beneficial to reduce the overpotential.

[0023] 3. The binary heterojunction In-Ni2Mo3N@Mo2C catalyst provided by the present application can perform efficient electrolytic water oxygen evolution reaction under alkaline conditions, and only needs 170mV overpotential at a current density of 10mA cm -2 .

[0024] 4. The binary heterojunction In-Ni2Mo3N@Mo2C catalyst provided by the present application can perform efficient urea catalytic oxidation reaction under alkaline conditions, and only needs 1.24V to reach a current density of 10mA cm -2 .

[0025] 5. Compared with the commonly used noble metal oxide RuO2, the raw material cost of the application is lower, and the catalytic performance is better than that of the noble metal RuO2 catalyst, and has higher stability.

[0026] 6. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst provided by the application has the advantages of easy raw materials, simple process, simple required equipment, and being conducive to mass production. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings described herein are used to provide further understanding of the application, constitute a part of the application, and do not constitute an improper limitation on the application, and in the drawings:

[0028] Figure 1 is the XRD pattern and standard card spectrum of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst (In-Ni2Mo3N@Mo2C catalyst) sample prepared in Example 1;

[0029] Figure 2 is a scanning electron microscope photo of the In-Ni2Mo3N@Mo2C catalyst sample;

[0030] Figure 3 is a scanning electron microscope photo of the Ni2Mo3N@Mo2C sample of Comparative Example 1;

[0031] Figure 4 is a scanning electron microscope photo of the Mo2C sample of Comparative Example 2;

[0032] Figure 5 is an electrochemical polarization curve diagram of the In-Ni2Mo3N@Mo2C catalyst, the sample Ni2Mo3N@Mo2C in Comparative Example 1, and the sample Mo2C in Comparative Example 2 in the oxygen evolution reaction;

[0033] Figure 6 is a comparison diagram of the electrochemical polarization curves of the In-Ni2Mo3N@Mo2C catalyst and the commercial RuO2 catalyst in the oxygen evolution reaction;

[0034] Figure 7 is an electrochemical polarization curve diagram of the In-Ni2Mo3N@Mo2C catalyst, the sample Ni2Mo3N@Mo2C in Comparative Example 1, and the sample Mo2C in Comparative Example 2 in the catalytic oxidation of urea;

[0035] Figure 8 is a polarization curve diagram of the In-Ni2Mo3N@Mo2C catalyst in the catalytic oxidation of urea;

[0036] Figure 9is a stability test diagram of the oxygen evolution reaction of the In-Ni2Mo3N@Mo2C catalyst in 1M KOH solution. DETAILED DESCRIPTION

[0037] The present application will be described in detail below with reference to the accompanying drawings and specific examples, which are used to explain the present application but not as a limitation thereof.

[0038] The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst provided by the embodiment of the present application comprises the following steps:

[0039] Step 1, dissolve dimethylimidazole in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a dimethylimidazole solution with a concentration of 0.4 mol / L; dissolve Mo salt (one of MoCl5 and MoCl3) in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a solution with a concentration of 0.04 mol / L;

[0040] Step 2, at room temperature, slowly add the dimethylimidazole solution to the Mo salt (one of MoCl5 and MoCl3) solution according to a molar ratio of dimethylimidazole to Mo element of (9-11):(0.9-1.1), and fully stir to obtain a suspension containing Mo metal organic framework Mo-MOF; then centrifuge and remove the supernatant after the suspension is left to stand for 10-15 hours, wash the centrifuged solid with anhydrous ethanol for 3-4 times, and finally dry the obtained solid in a vacuum drying oven at 50-60℃ for 2-5 hours to obtain Mo-MOF containing Mo metal organic framework;

[0041] Step 3, according to a molar ratio of Ni element to In element of (0.9-1):(0.9-1) and a mass ratio of the sum of the mass of Ni element and In element to the mass of Mo-MOF of (0.35-0.75):1, weigh a certain amount of Ni salt (one of NiCl2, NiCO3, Ni(NO2)2, NiSO4 or Ni(NO3)2), In salt (one of In(NO3)3, InCl3 or In2(SO4)3) and Mo-MOF obtained in step 2, place them in a beaker, add anhydrous ethanol solution, stir uniformly, perform ion exchange for 5-8 hours, finally wash, centrifuge 2-3 times, and vacuum dry at 50-60℃ for 2-5 hours to obtain a precursor;

[0042] Step 4, the precursor obtained in step 3 was placed in a tube furnace, and a mixed gas of 5% hydrogen and 95% argon was introduced, and the temperature was raised to 750-850°C at a heating rate of 3-5°C / min for calcination treatment, and the temperature was kept for 3-6 hours, and then the temperature was naturally reduced to room temperature, to obtain a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst (In-Ni2Mo3N@Mo2C catalyst).

[0043] The application will be further illustrated by different examples.

[0044] Example 1

[0045] (1) Dimethylimidazole was dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a dimethylimidazole solution, and MoCl5 was dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a Mo salt solution, according to a molar ratio of dimethylimidazole to Mo element of 10:1;

[0046] (2) The dimethylimidazole solution obtained in step (1) was slowly added to the Mo salt solution at room temperature according to a molar ratio of dimethylimidazole to Mo element of 10:1.1, and a Mo metal-organic framework Mo-MOF was obtained by fully stirring; then the suspension was left to stand for 12 hours, and the supernatant was removed by centrifugation, and the centrifugation was repeated 3 times with anhydrous ethanol, and finally the obtained solid was placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain the Mo-MOF containing the Mo metal-organic framework;

[0047] (3) According to a molar ratio of Ni element to In element of 0.9:1 and a mass ratio of the sum of the mass of Ni element and In element to the mass of Mo-MOF of 0.45:1, NiCl2, InCl3 and Mo-MOF were weighed and placed in a beaker, anhydrous ethanol solution was added, and stirring was performed uniformly for ion exchange for 6 hours, and finally washing-centrifugation was performed twice, and vacuum drying was performed at 60°C for 2 hours to obtain a precursor;

[0048] (4) The precursor obtained in step (3) was placed in a tube furnace, and a mixed gas of 10% hydrogen and 95% argon was introduced, and the temperature was raised to 800°C at a heating rate of 3°C / min for 6 hours, and then the temperature was naturally reduced to room temperature to obtain the In-Ni2Mo3N@Mo2C catalyst.

[0049] Figure 1 The XRD pattern of the sample prepared in Example 1. In the XRD pattern of the In-Ni2Mo3N@Mo2C catalyst, the characteristic diffraction peaks belonging to Ni2Mo3N and Mo2C can be clearly observed, which fully proves the successful preparation of the In-Ni2Mo3N@Mo2C catalyst.

[0050] Example 2

[0051] (1) According to the molar ratio of dimethyl imidazole to Mo element being 9:1.1, dimethyl imidazole is dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a dimethyl imidazole solution; MoCl5 is dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a Mo salt solution;

[0052] (2) At room temperature, the dimethyl imidazole solution obtained in step (1) is slowly added dropwise into the Mo salt solution according to the molar ratio of dimethyl imidazole to Mo element being 9:1, and a suspension containing Mo metal organic framework Mo-MOF is obtained after sufficient stirring; then the suspension is left to stand for 10 hours, the supernatant is removed by centrifugation, the obtained solid is washed with anhydrous ethanol by centrifugation for 3 times, and finally the obtained solid is placed in a vacuum drying oven and dried at 55℃ for 3 hours to obtain Mo-MOF containing Mo metal organic framework;

[0053] (3) According to the molar ratio of Ni element to In element being 1:0.9 and the mass ratio of the sum of the mass of Ni element and In element to the mass of Mo-MOF being 0.75:1, Ni(NO2)2, In(NO3)3 and Mo-MOF are weighed and placed in a beaker, anhydrous ethanol solution is added, stirred uniformly, ion exchange is carried out for 5 hours, finally washed and centrifuged for 3 times, and vacuum dried at 50℃ for 5 hours to obtain a precursor;

[0054] (4) The precursor obtained in step (3) is placed in a tube furnace, a mixed gas of 10% hydrogen and 95% argon is introduced, the temperature is raised to 750℃ at a temperature rising rate of 4℃ / min, and kept for 5 hours, and the temperature is naturally reduced to room temperature to obtain an In-Ni2Mo3N@Mo2C catalyst.

[0055] Example 3

[0056] (1) According to the molar ratio of dimethyl imidazole to Mo element being 11:1, dimethyl imidazole is dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a dimethyl imidazole solution; MoCl3 is dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a Mo salt solution;

[0057] (2) At room temperature, the dimethyl imidazole solution obtained in step (1) is slowly added dropwise into the Mo salt solution according to the molar ratio of dimethyl imidazole to Mo element being 11:0.9, and a suspension containing Mo metal organic framework Mo-MOF is obtained after sufficient stirring; then the suspension is left to stand for 15 hours, the supernatant is removed by centrifugation, the obtained solid is washed with anhydrous ethanol by centrifugation for 3 times, and finally the obtained solid is placed in a vacuum drying oven and dried at 50℃ for 5 hours to obtain Mo-MOF containing Mo metal organic framework;

[0058] (3) According to the molar ratio of Ni element to In element being 1:1 and the ratio of the sum of the mass of Ni element and In element to the mass of Mo-MOF being 0.35:1, NiCO3, In2(SO4)3 and Mo-MOF are weighed and placed in a beaker, anhydrous ethanol solution is added, stirred uniformly, ion exchange is performed for 8 hours, finally washed and centrifuged 3 times, and the precursor is obtained by vacuum drying at 55℃ for 3 hours;

[0059] (4) The precursor obtained in step (3) is placed in a tube furnace, a mixed gas of 10% hydrogen and 95% argon is introduced, the temperature is raised to 850℃ at a temperature rising rate of 5℃ / min, and the temperature is kept for 3 hours, and the In-Ni2Mo3N@Mo2C catalyst is obtained after the temperature naturally decreases to room temperature.

[0060] Comparative Example 1

[0061] This comparative example provides a Ni2Mo3N@Mo2C catalyst, and the preparation process is as follows:

[0062] (1) According to the molar ratio of dimethyl imidazole to Mo element being 10:1, dimethyl imidazole is dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a dimethyl imidazole solution; and MoCl5 is dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a Mo salt solution;

[0063] (2) At room temperature, the dimethyl imidazole solution obtained in step (1) is slowly added dropwise into the Mo salt solution according to the molar ratio of dimethyl imidazole to Mo element being 10:1.1, and the Mo metal organic framework Mo-MOF is obtained by fully stirring; then the suspension is left to stand for 12 hours, the supernatant is removed by centrifugation, the obtained solid is washed and centrifuged 3 times with anhydrous ethanol, and finally the obtained solid is placed in a vacuum drying oven and dried at 60℃ for 2 hours to obtain the Mo-MOF containing Mo metal organic framework;

[0064] (3) The same amount of NiCl2 and Mo-MOF as in Example 1 is weighed and placed in a beaker, anhydrous ethanol solution is added, stirred uniformly, ion exchange is performed for 6 hours, finally washed and centrifuged 2 times, and the precursor is obtained by vacuum drying at 60℃ for 2 hours;

[0065] (4) The precursor obtained in step (3) is placed in a tube furnace, a mixed gas of 10% hydrogen and 95% argon is introduced, the temperature is raised to 800℃ at a temperature rising rate of 3℃ / min, and the temperature is kept for 6 hours, and the Ni2Mo3N@Mo2C catalyst is obtained after the temperature naturally decreases to room temperature.

[0066] Figure 2 and Figure 3Scanning electron microscope images of In-Ni2Mo3N@Mo2C catalyst and Ni2Mo3N@Mo2C catalyst in Comparative Example 1, respectively. Compared with Ni2Mo3N@Mo2C, the In-Ni2Mo3N@Mo2C catalyst has more uniform particle size distribution and less agglomeration, indicating that the introduction of In is conducive to inhibiting the agglomeration of the material during synthesis and exposing more catalytically active sites.

[0067] Comparative Example 2

[0068] The present comparative example provides a Mo2C catalyst, which is prepared as follows:

[0069] (1) Dimethylimidazole was dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a dimethylimidazole solution according to a molar ratio of dimethylimidazole to Mo element of 10:1. MoCl5 was dissolved in a mixed solution of anhydrous ethanol and methanol in a volume ratio of 1:1 to obtain a Mo salt solution;

[0070] (2) The dimethylimidazole solution obtained in step (1) was slowly added to the Mo salt solution at room temperature according to a molar ratio of dimethylimidazole to Mo element of 10:1.1, and a Mo metal-organic framework Mo-MOF was obtained by fully stirring; then the suspension was left to stand for 12 hours, the supernatant was removed by centrifugation, the centrifugation was washed with anhydrous ethanol for 3 times, and finally the obtained solid was placed in a vacuum drying oven and dried at 60°C for 2 hours to obtain the Mo-MOF containing Mo metal-organic framework;

[0071] (3) The same amount of Mo-MOF as in Example 1 was weighed into a beaker, anhydrous ethanol solution was added, stirred uniformly, ion exchange was carried out for 6 hours, and finally washed-centrifuged 2 times, vacuum dried at 60°C for 2 hours to obtain a precursor;

[0072] (4) The precursor obtained in step (3) was placed in a tube furnace, a mixed gas of 10% hydrogen and 95% argon was introduced, the temperature was raised to 800°C at a rate of 3°C / min, and the temperature was kept for 6 hours, and then the temperature was naturally reduced to room temperature to obtain a Mo2C catalyst.

[0073] The prepared catalysts were characterized by scanning electron microscopy, and the results are shown in Figures 2 to 4 In-Ni2Mo3N@Mo2C, Comparative Example 1 sample Ni2Mo3N@Mo2C and Comparative Example 2 sample Mo2C all exhibit irregular nanoparticles, and In-Ni2Mo3N@Mo2C is more uniform than the other samples, indicating that In doping can reduce the agglomeration during catalyst preparation and is conducive to exposing more catalytically active sites.

[0074] Figure 5Linear voltammetric scans of In-Ni2Mo3N@Mo2C (Example 1), Ni2Mo3N@Mo2C (Comparative Example 1), and Mo2C (Comparative Example 2) in the oxygen evolution reaction are shown. The figures demonstrate that In doping and the construction of the binary heterostructure significantly promote the electrocatalytic activity of the oxygen evolution reaction. Meanwhile, as... Figure 6 As shown, compared to commercial RuO2, the binary heterostructure In-Ni2Mo3N@Mo2C catalyst requires lower overpotentials to achieve 10, 50, and 100 mA cm⁻¹. -2 The current density when the overpotential is 10 mA cm -2 At this time, the overpotential of In-Ni2Mo3N@Mo2C is 170mV, which shows excellent electrocatalytic oxygen evolution performance.

[0075] Figure 7 The figures show the linear voltammetric scans of In-Ni2Mo3N@Mo2C from Example 1, Ni2Mo3N@Mo2C from Comparative Example 1, and Mo2C from Comparative Example 2 in the catalytic oxidation of urea. As can be seen from the figures, In doping and the construction of the binary heterostructure significantly promote the activity of the catalytic oxidation of urea. Figure 8 As shown, the binary heterostructure In-Ni2Mo3N@Mo2C catalyst requires only 1.24V, 1.29V, and 1.37V to achieve 10, 50, and 100 mA cm⁻¹, respectively. -2 The current density indicates that it has excellent urea catalytic oxidation performance.

[0076] Application example:

[0077] The application of an In-Ni2Mo3N@Mo2C electrocatalyst prepared by the method described above in the alkaline oxygen evolution reaction and catalytic oxidation of urea includes:

[0078] 5 mg of catalyst sample (including In-Ni2Mo3N@Mo2C, Ni2Mo3N@Mo2C, Mo2C, and RuO2) was co-dispersed with 1 mg of Ketjen black in a mixed solvent of 50 μL Nafion solution and 1 mL ethanol. The mixture was then sonicated for 30 minutes to prepare a uniform catalyst ink. Subsequently, the obtained catalyst ink was uniformly drop-coated onto a 1×1.5 cm... 2 The electrode was prepared by drying it on a carbon cloth substrate under vacuum for 1 hour.

[0079] The electrochemical performance test was performed using a standard three-electrode system to evaluate the oxygen evolution reaction and the urea oxidation reaction. Specifically, the oxygen evolution reaction test was performed in 1M KOH electrolyte, while the urea oxidation reaction test was performed in a mixed electrolyte of 1M KOH and 0.5M urea. The working electrode was a carbon cloth loaded with catalyst ink, the counter electrode was a carbon rod, and the reference electrode was a saturated calomel electrode. The polarization curve of the catalyst was determined using linear sweep voltammetry (LSV) at a scan rate of 5mV s -1 In addition, the long-term stability of the catalyst was evaluated using chronoamperometry (i-t curve).

[0080] Figure 9 Figure 1 is a graph of the stability test results for the In-Ni2Mo3N@Mo2C catalyst. As can be seen from the graph, the binary heterojunction In-Ni2Mo3N@Mo2C catalyst exhibits excellent stability, indicating that the catalyst has good commercial application prospects.

[0081] The present application is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present application, those skilled in the art can make some substitutions and modifications to some technical features without creative labor, and these substitutions and modifications are all within the protection scope of the present application.

Claims

1. A preparation method of a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst, characterized in that, The method comprises the following steps: a. dissolving dimethylimidazole in a mixed solution of anhydrous ethanol and methanol to obtain a dimethylimidazole solution; dissolving a Mo salt in a mixed solution of anhydrous ethanol and methanol to obtain a Mo salt solution; b. slowly adding the dimethylimidazole solution into the Mo salt solution at room temperature according to a molar ratio of dimethylimidazole to Mo element of (9-11):(0.9-1.1), stirring to obtain a suspension containing Mo metal-organic framework Mo-MOF; standing the suspension, removing the supernatant, centrifugally washing the precipitate, vacuum drying the obtained solid to obtain Mo-MOF containing Mo metal-organic framework; c. adding a Ni salt, an In salt and the Mo-MOF into an anhydrous ethanol solution according to a molar ratio of Ni element to In element of (0.9-1):(0.9-1) and a ratio of the sum of the mass of the Ni element and the In element to the mass of the Mo-MOF of (0.35-0.75):1, stirring to perform ion exchange, washing, centrifuging and vacuum drying to obtain a precursor; d. calcining the precursor under a protective atmosphere, naturally reducing to room temperature to obtain a bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst.

2. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, The Mo salt is one of MoCl5 or MoCl3.

3. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, The Ni salt is one of NiCO3, Ni(NO2)2, NiSO4, NiCl2 or Ni(NO3)2.

4. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, The In salt is one of In(NO3)3, InCl3 or In2(SO4)3.

5. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, In step a, the volume ratio of anhydrous ethanol to methanol is 1:

1.

6. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, In step b, the suspension is centrifuged to remove the supernatant after standing for 10-15 hours, the obtained solid is washed with anhydrous ethanol and centrifuged for 3-4 times, and the obtained solid is vacuum dried for 2-5 hours; In step c, the ion exchange is performed for 5-8 hours, the washing is performed for 2-3 times, and the vacuum drying is performed at 50-60℃ for 2-5 hours.

7. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, In step d, the protective atmosphere is a mixed gas of 5% hydrogen and 95% argon.

8. The preparation method of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 1, characterized in that, In step d, the calcination temperature is 750-850℃, the heating rate is 3-5℃ / min, and the holding time is 3-6 hours.

9. A bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst prepared by the method according to any one of claims 1-8.

10. Application of the bifunctional In-doped Ni2Mo3N@Mo2C binary heterojunction catalyst according to claim 9 in electrolytic water and catalytic oxidation of urea.

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