Carbon material loaded Ni / NiO heterojunction composite catalyst and preparation method thereof

Abstract

The invention discloses a carbon material loaded Ni / NiO heterojunction composite catalyst and a preparation method thereof.The preparation method comprises the following steps that S1, nickel metal salt and a metal chelating agent are added into a solvent and stirred until the nickel metal salt and the metal chelating agent are completely dissolved, and a mixed solution is obtained; s2, adding a carbon material carrier into the mixed solution, heating, stirring, carrying out reflux condensation, and then filtering, drying and grinding a product to obtain a precursor; s3, transferring the precursor to a tubular furnace, and calcining in a protective atmosphere to obtain a Ni / C composite material; and S4, annealing the Ni / C composite material in air to oxidize the Ni part on the surface into NiO to form a Ni / NiO heterojunction so as to obtain the carbon material loaded Ni / NiO heterojunction composite catalyst. The process conditions are mild, the catalyst cost is low, the activity is high, the efficiency of catalytic cracking and hydrogen transfer reaction can be remarkably improved, and technical support is provided for efficient exploitation and transportation of heavy oil.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to a carbon-supported Ni / NiO heterojunction composite catalyst and its preparation method. Background Technology

[0002] The core of heavy oil extraction lies in reducing its high viscosity. In-situ catalytic reforming technology offers a new approach to this. This technology treats the reservoir as a reactor, using catalysts to directly crack and reform the heavy oil under formation conditions, fundamentally altering its molecular composition and achieving permanent viscosity reduction. Among these technologies, hydrocracking reforming, by introducing a hydrogen source and catalyst into the reaction, not only significantly inhibits coking and promotes impurity removal, but also efficiently converts heavy components into light components, achieving permanent viscosity reduction and oil quality improvement, demonstrating significant advantages.

[0003] The core of this technology lies in the performance of the catalyst. Currently, catalysts suffer from problems such as low catalytic efficiency and incomplete cracking of asphaltenes. Catalyst research and development is moving towards low-temperature high efficiency, long-term stability, and environmental friendliness. Summary of the Invention

[0004] To address the aforementioned problems, this invention aims to provide a carbon-supported Ni / NiO heterojunction composite catalyst and its preparation method.

[0005] The technical solution of the present invention is as follows: On the one hand, a method for preparing a carbon-supported Ni / NiO heterojunction composite catalyst is provided, comprising the following steps: S1: Add nickel metal salt and metal chelating agent to the solvent and stir until completely dissolved to obtain a mixed solution; S2: Add a carbon material carrier to the mixed solution, heat and stir, reflux and condense, then filter, dry and grind the product to obtain the precursor; S3: The precursor is transferred to a tube furnace and calcined under a protective atmosphere to obtain a Ni / C composite material; S4: Anneal the Ni / C composite material in air to oxidize the surface Ni portion to NiO, forming a Ni / NiO heterojunction, and obtain a carbon-supported Ni / NiO heterojunction composite catalyst.

[0006] Preferably, in step S1, the nickel metal salt is any one or more of nickel nitrate hexahydrate, nickel chloride, nickel citrate hydrate, nickel acetate tetrahydrate, and nickel ammonium nitrate.

[0007] Preferably, in step S1, the metal chelating agent is any one or more of 8-hydroxyquinoline, 2,2'-bibenzimidazole, N,N'-dimethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, 2,2'-bipyridine, 1,10-phenanthroline, 2,2':6',2''-terpyridine, and porphyrin.

[0008] Preferably, in step S1, the solvent is any one or more of methanol, anhydrous ethanol, and isopropanol.

[0009] Preferably, in step S1, the molar ratio of the nickel metal salt to the metal chelating agent is 1:2~4.

[0010] Preferably, in step S1, the stirring is performed magnetically at 20℃~30℃ and 200rpm~400rpm for 0.5h~1h.

[0011] Preferably, in step S2, the carbon material carrier is any one or more of graphene, carbon nanotubes, carbon quantum dots, and carbon black.

[0012] Preferably, in step S2, when heating and stirring, the magnetic stirring is performed at 55℃~75℃ and 400rpm~600rpm for 3h~5h.

[0013] Preferably, in step S3, calcination is carried out at 550℃~650℃ for 2h~3h; in step S4, annealing is carried out at 350℃~450℃ for 1h~2h.

[0014] On the other hand, a carbon-supported Ni / NiO heterojunction composite catalyst is also provided, which is prepared by the preparation method of the carbon-supported Ni / NiO heterojunction composite catalyst described in any one of the above-mentioned methods.

[0015] The beneficial effects of this invention are: The process conditions of this invention are mild, and the catalyst is low-cost and highly active, which can significantly improve the efficiency of catalytic cracking and hydrogen transfer reactions, providing technical support for the efficient extraction and transportation of heavy oil. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic diagram illustrating the principle of the carbon-supported Ni / NiO heterojunction composite catalyst of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0019] On one hand, the present invention provides a method for preparing a carbon-supported Ni / NiO heterojunction composite catalyst, comprising the following steps: S1: Add nickel metal salt and metal chelating agent to the solvent and stir until completely dissolved to obtain a mixed solution.

[0020] In one specific embodiment, the nickel metal salt is any one or more of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), nickel chloride (NiCl2), nickel citrate hydrate (Ni3(C6H5O7)2·H2O), nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O), and nickel ammonium nitrate ([Ni(NH3)4](NO3)2), and the metal chelating agent is 8-hydroxyquinoline (C9H7NO) or 2,2'-bibenzimidazole (C 14 H 10 N4), N,N'-dimethylethylenediamine (C4H) 12 N2), N,N,N',N'-Tetramethylethylenediamine (C6H) 16 N2), 2,2'-bipyridine (C 10 H8N2), 1,10-phenanthroline (C 12 H8N2), 2,2':6',2''-terpyridine (C 15 H 11 N3), porphyrin (C 84 H 90 N8O 12 S4) is any one or more of the following, wherein the solvent is any one or more of methanol (CH4O), anhydrous ethanol (C2H6O), and isopropanol (C3H8O).

[0021] It should be noted that the solvents used in the above embodiments are only preferred solvents of the present invention, and their purpose is to dissolve the nickel metal salt and the metal chelating agent. In addition to the solvents used in the above embodiments, other existing solvents that can achieve this purpose can also be applied to the present invention.

[0022] In one specific embodiment, the molar ratio of the nickel metal salt to the metal chelating agent is 1:2~4.

[0023] In one specific embodiment, the stirring is performed magnetically at 20°C to 30°C and 200 rpm to 400 rpm for 0.5 h to 1 h. It should be noted that the purpose of stirring is to completely dissolve the nickel metal salt and the metal chelating agent in the solvent. Besides the preferred stirring conditions in this embodiment, other stirring conditions that achieve this purpose are also applicable to this invention.

[0024] S2: Add a carbon material carrier to the mixed solution, heat and stir, then reflux and condense, and then filter, dry and grind the product to obtain the precursor.

[0025] In one specific embodiment, the carbon material carrier is any one or more of graphene, carbon nanotubes, carbon quantum dots, and carbon black.

[0026] In one specific embodiment, during heating and stirring, magnetic stirring is performed at 55℃~75℃ and 400rpm~600rpm for 3h~5h.

[0027] In one specific embodiment, the drying process is carried out under vacuum at 40°C to 60°C; the grinding process is carried out by grinding thoroughly with an agate mortar until uniform.

[0028] S3: The precursor is transferred to a tube furnace and calcined under a protective atmosphere to obtain a Ni / C composite material.

[0029] In one specific embodiment, calcination is performed at 550°C to 650°C for 2 to 3 hours. Optionally, the heating rate during calcination is 10°C / min, and the protective atmosphere is nitrogen or helium.

[0030] S4: Anneal the Ni / C composite material in air to oxidize the surface Ni portion to NiO, forming a Ni / NiO heterojunction, and obtain a carbon-supported Ni / NiO heterojunction composite catalyst.

[0031] In one specific embodiment, annealing is performed at 350°C to 450°C for 1 to 2 hours.

[0032] On the other hand, the present invention also provides a carbon-supported Ni / NiO heterojunction composite catalyst, which is prepared by the preparation method of the carbon-supported Ni / NiO heterojunction composite catalyst described in any one of the above-mentioned methods.

[0033] In this invention, such as Figure 1 As shown, the carbon-supported Ni / NiO heterojunction composite catalyst exhibits strong chemical bonding forces at the heterojunction interface, effectively inhibiting the migration, agglomeration, and sintering of active components under harsh reaction conditions, thus preventing catalyst structural damage. This characteristic ensures that the catalyst maintains high activity over a long period in high-temperature, high-pressure, and heavy oil complex environments, significantly extending its service life.

[0034] At the heterojunction interface, due to lattice mismatch and strong electronic interactions, a large number of vacancies and defects can be spontaneously induced. These defect structures themselves are highly efficient catalytic active centers, which can greatly promote the breaking of heteroatom bonds such as CS and CN, that is, promote hydrodesulfurization and hydrodenitrogenation reactions, and effectively crack long-chain alkanes and aromatics in heavy oil, thereby achieving deep viscosity reduction and quality improvement.

[0035] Vacancies and defects induced at the heterojunction interface can serve as highly efficient activation centers for hydrogen, promoting the dissociation of hydrogen into active hydrogen. Simultaneously, the interfacial electric field can effectively regulate electron flow, accelerating the transfer of active hydrogen to reactant molecules, thereby significantly increasing the hydrocracking reaction rate and effectively suppressing condensation coking reactions, thus improving the yield of light oil.

[0036] Example 1 A carbon-supported Ni / NiO heterojunction composite catalyst is prepared by the following steps: (1) Weigh 1 mmol (0.291 g) of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 2 mmol (0.360 g) of 1,10-phenanthroline (C 12 H8N2) was dissolved in 60 mL of anhydrous ethanol and stirred at room temperature for 30 min until completely dissolved, forming a clear solution.

[0037] (2) Add 1.0g of carbon black carrier to the above solution, then transfer the mixture to an oil bath, heat and stir at 55°C and reflux and condense for 4h.

[0038] (3) Filter the obtained mixture and wash the filter cake three times with anhydrous ethanol. Place the filter material in a vacuum drying oven and dry it at 40°C for 24 hours. Then grind it thoroughly with an agate mortar to obtain the precursor powder.

[0039] (4) The precursor powder is transferred to a tube furnace and heated to 550°C at a rate of 10°C / min under a nitrogen atmosphere. The mixture is then calcined at this temperature for 3 hours to obtain a Ni / C composite material. The Ni / C composite material is annealed in air at 350°C for 2 hours to oxidize the surface Ni to NiO, forming a Ni / NiO heterojunction, thus obtaining a carbon-supported Ni / NiO heterojunction composite catalyst.

[0040] Example 2 A carbon-supported Ni / NiO heterojunction composite catalyst is prepared by the following steps: (1) Weigh 1 mmol (0.130 g) of nickel chloride (NiCl2) and 3 mmol (0.469 g) of 2,2'-bipyridine (C 10 H8N2) was dissolved in 70 mL of methanol and stirred at room temperature until completely dissolved to form a homogeneous solution.

[0041] (2) Add 1.2g of carbon nanotube carrier to the above solution, and then place the mixture in a 65℃ oil bath, heat and stir and reflux and condense for 3h.

[0042] (3) The obtained mixture was filtered and washed thoroughly with methanol. The filter cake was dried in a vacuum drying oven at 50°C for 24 hours and then ground evenly in an agate mortar to obtain precursor powder.

[0043] (4) The precursor powder is placed in a tube furnace and heated to 600°C at a rate of 10°C / min under a helium atmosphere, and calcined at this temperature for 2.5 h to obtain a Ni / C composite material; the Ni / C composite material is annealed in air at 400°C for 1.5 h to oxidize the surface Ni to NiO, forming a Ni / NiO heterojunction, and obtaining a carbon-supported Ni / NiO heterojunction composite catalyst.

[0044] Example 3 A carbon-supported Ni / NiO heterojunction composite catalyst is prepared by the following steps: (1) Weigh 1 mmol (0.259 g) nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O) and 4 mmol (0.581 g) 8-hydroxyquinoline (C9H7NO), dissolve them in 75 mL of isopropanol, and stir until completely dissolved.

[0045] (2) Add 1.5g of carbon quantum dots to the above solution, heat and stir at 75°C and reflux and condense for 3h.

[0046] (3) The mixture was filtered and washed with isopropanol. The resulting solid was dried in a vacuum drying oven at 60°C for 24 hours and then ground to obtain precursor powder.

[0047] (4) The precursor powder is placed in a tube furnace and heated to 650°C at 10°C / min under a nitrogen atmosphere and calcined for 2 hours to obtain a Ni / C composite material; the Ni / C composite material is annealed in air at 450°C for 1 hour to oxidize the surface Ni to NiO and form a Ni / NiO heterojunction to obtain a carbon-supported Ni / NiO heterojunction composite catalyst.

[0048] Example 4 A carbon-supported Ni / NiO heterojunction composite catalyst is prepared by the following steps: (1) Weigh 1 mmol (0.572 g) of nickel citrate hydrate (Ni3(C6H5O7)2·H2O) and 2.5 mmol (0.220 g) of N,N'-dimethylethylenediamine (C4H 12 N2) was dissolved in 70 mL of a mixture of anhydrous ethanol and methanol (volume ratio 1:1) and stirred until completely dissolved.

[0049] (2) Add 1.0g of graphene carrier to the above solution, heat and stir at 60℃ and reflux and condense for 5h.

[0050] (3) The reaction mixture was filtered and washed. The filter cake was dried under vacuum at 45°C for 24 hours and then ground evenly to obtain precursor powder.

[0051] (4) The precursor powder is placed in a tube furnace and heated to 600°C at 10°C / min under a nitrogen atmosphere and calcined for 3 hours to obtain a Ni / C composite material; the Ni / C composite material is annealed in air at 400°C for 1 hour to oxidize the surface Ni to NiO and form a Ni / NiO heterojunction to obtain a carbon-supported Ni / NiO heterojunction composite catalyst.

[0052] Comparative Example 1 Unlike Example 1, step (4) in this comparative example does not use a multi-step impregnation-annealing method, but a mechanical mixing method. Specifically: (4) Dissolve the precursor powder and 1 mmol (0.075 g) of nickel oxide (NiO) in 60 mL of ammonia water, stir and react at 30 °C for 4 h, filter and wash the mixture after reaction, and dry it under vacuum at 45 °C for 24 h to obtain carbon-supported Ni / NiO composite catalyst.

[0053] Comparative Example 2 Unlike Example 1, step (4) of this comparative example does not use the multi-step impregnation-annealing method, but rather the hydrothermal solvent method. Specifically: (4) The precursor powder was ultrasonically dispersed in 100 mL of deionized water. The dispersion was transferred to a sealed reaction vessel and stirred for 4 h at 140 °C and 1 MPa. The mixture after reaction was filtered, washed, and vacuum dried at 45 °C for 24 h to obtain carbon-supported Ni / NiO composite catalyst.

[0054] Test Example 1 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.5g of the catalyst from Examples 1-4 and Comparative Examples 1-2 (0.5% of the crude oil mass) and 1g of tetrahydronaphthalene hydrogen donor (1% of the crude oil mass) were added respectively. The reactor was sealed and reacted at 220℃ for 18h. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected and analyzed.

[0055] (1) The viscosity of crude oil before and after the reaction was tested using a viscometer. The specific test method is as follows: A certain amount of oil sample before and after the reaction was placed in a beaker and heated in an oven at 50℃ for 10 min to 15 min. At the same time, the constant temperature water bath of the viscometer was adjusted to 50℃ and kept at that temperature. Then, about 2 mL of heavy oil was drawn with a syringe and evenly injected into the sample cell of the viscometer. The rotor speed was set to 0.03 rpm to 0.05 rpm, and the torque was maintained at about 50%. Finally, the viscosity was measured, and the viscosity reduction rate was obtained by (crude oil viscosity before reaction - crude oil viscosity after reaction) / crude oil viscosity before reaction × 100%.

[0056] (2) X-ray photoelectron spectroscopy (XPS) was used to characterize the interfacial interactions and oxygen vacancy density in the catalyst.

[0057] (3) According to NB / SH / T 0509-2010 Petroleum Asphalt Four-Component Determination Method, analyze the composition ratio of asphaltene and resin in crude oil before and after the reaction, and compare the catalytic viscosity reduction effect of different catalysts.

[0058] The test results are shown in Tables 1 and 2: Table 1. Test results of catalysts in Example 1 and Comparative Examples 1-2

[0059] As shown in Table 1, Comparative Example 1, the mechanical mixing method, is merely a physical mixing process and cannot form effective chemical bonds and electronic interactions between Ni and NiO, leading to the separation of active components and limited synergistic effect, thus resulting in the worst viscosity reduction effect. Comparative Example 2, the hydrothermal solvent method, reacts in solution and can initially construct a certain heterostructure, but the resulting heterojunction is incomplete, limiting the upper limit of performance. In contrast, Example 1 of this invention ensures high dispersion of active components on the carrier through impregnation, and then constructs a complete and stable Ni / NiO heterojunction through a controllable annealing step. By actively constructing a new structure with a complete heterojunction and high oxygen vacancy density, the synergistic effect of Ni and NiO is maximized, thereby achieving a qualitative leap in the viscosity reduction rate of heavy oil from 50% to over 80% without significantly increasing costs.

[0060] Table 2 Catalyst Test Results in Examples 1-4

[0061] As can be seen from Table 2, the catalysts obtained in Examples 1-4 of this invention can all effectively reduce the viscosity of extra-heavy oil, with a viscosity reduction rate of over 80%; and can effectively catalyze the cracking of macromolecular asphaltenes and gums in extra-heavy oil, reducing the proportion of asphaltenes and gums in crude oil from the original 48% to 28%-39%. Among them, the catalyst obtained in Example 3 has the best viscosity reduction effect in hydrocatalytic cracking.

[0062] Test Example 2 Furthermore, in order to more clearly and in detail introduce the application of the carbon-supported Ni / NiO heterojunction composite catalyst provided in the embodiments of the present invention, the catalyst obtained in Example 3, which has the best catalytic viscosity reduction effect in Test Example 1 above, will be used in conjunction with specific embodiments to illustrate the changes in different catalyst dosages, reaction temperatures, and reaction times, so as to demonstrate the wide applicability and optimization effect of the invention.

[0063] Example 5: 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.3g of the catalyst from Example 3 (0.3% of the crude oil mass) and 1g of tetrahydronaphthalene hydrogen donor (1% of the crude oil mass) were added. The reactor was sealed and reacted at 200℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected for analysis.

[0064] Example 6: 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.5g of the catalyst from Example 3 (0.5% of the crude oil mass) and 1g of tetrahydronaphthalene hydrogen donor (1% of the crude oil mass) were added. The reactor was sealed and reacted at 200℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected for analysis.

[0065] Example 7 (i.e., the test example of the catalyst in Example 3 of Test Example 1 above): 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.5g of the catalyst from Example 3 (0.5% of the crude oil mass) and 1g of tetrahydronaphthalene hydrogen donor (1% of the crude oil mass) were added. The reactor was sealed and reacted at 220°C for 18h. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected for analysis.

[0066] Example 8: 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.5g of the catalyst from Example 3 (0.5% of the crude oil mass) and 1g of decahydronaphthalene hydrogen donor (1% of the crude oil mass) were added. The reactor was sealed and reacted at 240℃ for 18h. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected for analysis.

[0067] Example 9: 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.7g of the catalyst from Example 3 (0.7% of the crude oil mass) and 1g of decahydronaphthalene hydrogen donor (1% of the crude oil mass) were added. The reactor was sealed and reacted at 240℃ for 18h. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected for analysis.

[0068] Example 10: 100g of extra-heavy oil was placed in a high-pressure reactor, and 0.7g of the catalyst from Example 3 (0.7% of the crude oil mass) and 1g of decahydronaphthalene hydrogen donor (1% of the crude oil mass) were added. The reactor was sealed and reacted at 240℃ for 24h. After the reaction was completed, the mixture was cooled to room temperature, and the product was collected for analysis.

[0069] The product analysis results of the above embodiments are shown in Table 3: Table 3 Test results of the catalyst in Example 3 under various conditions

[0070] As shown in Table 3, under different conditions, the catalyst obtained in Example 3 can effectively reduce the viscosity of extra-heavy oil, catalytically crack the macromolecular asphaltenes and gums in extra-heavy oil, and reduce the proportion of asphaltenes and gums in crude oil components. However, the actual application effect is affected by different catalyst dosages, reaction temperatures, and reaction times. (1) Comparing Example 5 and Example 6, under the same temperature and reaction time, the amount of catalyst was increased from 0.3% to 0.5%. The increase in amount directly increased the total number of active sites in the reaction system, enabling more heavy component molecules to be cracked, thereby improving the viscosity reduction rate.

[0071] (2) Comparing Examples 6-8, under the same catalyst dosage, as the catalytic temperature increases, the catalyst activity is enhanced and the reaction rate increases. The thermal energy can drive effective catalytic cracking and hydrogen transfer reaction, thereby achieving a higher viscosity reduction rate and asphaltene conversion rate. At the same time, as the reaction time increases, heavy molecules are fully cracked and hydrogenated and stabilized, which improves the viscosity reduction and conversion effect.

[0072] (3) Compared with Examples 8-10, further increasing the amount of catalyst did not significantly improve the viscosity reduction effect, indicating that there are sufficient active sites, which can effectively synergistically complete hydrogen transfer and cracking catalysis. Further increasing the reaction time actually worsened the viscosity reduction effect, indicating that excessively long reaction time would trigger secondary reactions. Free radicals or unstable intermediates in the system would have more time to undergo condensation reactions, generating new coke C precursors, which might deteriorate the product properties or cause coking and deactivation of the catalyst surface.

[0073] These examples fully demonstrate the effectiveness and flexibility of carbon-supported Ni / NiO heterojunction composite catalysts in reducing viscosity during crude oil catalytic cracking, especially under optimized conditions (such as Examples 7 and 8), where viscosity reduction rates of over 90% and a significant reduction in the proportion of asphaltenes can be achieved.

[0074] In summary, the catalyst prepared by this invention can significantly improve the efficiency of catalytic cracking and hydrogen transfer reactions. Compared with the prior art, this invention represents a significant advancement.

[0075] The above description is merely a representative embodiment of the present invention and is not intended to limit the present invention in any way. Any embodiment made by those skilled in the art without departing from the scope of the present invention and utilizing the disclosed technical content is an equivalent embodiment of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a carbon material-supported Ni / NiO heterojunction composite catalyst, characterized by, The method comprises the following steps: S1: adding a nickel metal salt and a metal chelating agent into a solvent, stirring until completely dissolved to obtain a mixed solution; S2: adding a carbon material carrier to the mixed solution, heating and stirring and refluxing and condensing, and then filtering, drying and grinding the product to obtain a precursor; S3: transferring the precursor to a tube furnace, calcining under a protective atmosphere to obtain a Ni / C composite material; S4: annealing the Ni / C composite material in air, partially oxidizing the surface Ni to NiO to form a Ni / NiO heterojunction, and obtaining a carbon material loaded Ni / NiO heterojunction composite catalyst.

2. The method for preparing a carbon material-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized by, In step S1, the nickel metal salt is any one or more of nickel nitrate hexahydrate, nickel chloride, nickel citrate hydrate, nickel acetate tetrahydrate, and nickel ammonium nitrate.

3. The method for preparing the carbon-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized in that, In step S1, the metal chelating agent is any one or more of 8-hydroxyquinoline, 2,2'-bipyridine, N,N'-dimethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, 2,2'-bipyridine, 1,10-phenanthroline, 2,2':6',2''-terpyridine, and porphyrin.

4. The method for preparing the carbon-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized in that, In step S1, the solvent is any one or more of methanol, anhydrous ethanol, and isopropanol.

5. The method for preparing the carbon-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized in that, In step S1, the molar ratio of the nickel metal salt to the metal chelating agent is 1:2-4.

6. The method for preparing the carbon-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized in that, In step S1, when stirring, the magnetic stirring is performed at 20-30°C and 200-400 rpm for 0.5-1 h.

7. The method for preparing the carbon-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized in that, In step S2, the carbon material carrier is any one or more of graphene, carbon nanotubes, carbon quantum dots, and carbon black.

8. The method for preparing the carbon-supported Ni / NiO heterojunction composite catalyst according to claim 1, characterized in that, In step S2, when heating and stirring, the magnetic stirring is performed at 55-75°C and 400-600 rpm for 3-5 h.

9. The method for preparing a carbon material supported Ni / NiO heterojunction composite catalyst according to any one of claims 1-8, characterized in that, In step S3, when calcining, the calcining is performed at 550-650°C for 2-3 h; and in step S4, when annealing, the annealing is performed at 350-450°C for 1-2 h.

10. A carbon material-supported Ni / NiO heterojunction composite catalyst, characterized in that, The carbon material loaded Ni / NiO heterojunction composite catalyst is prepared by the method of any one of claims 1-9.

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