Small biological molecule based-cobalt / molybdenum disulfide composite material as well as preparation method and application thereof

Abstract

The invention discloses a biological small molecule based-cobalt / molybdenum disulfide composite material as well as a preparation method and application thereof. According to the preparation method, small biological molecules are taken as a carbon material, and are subjected to vulcanization treatment on the basis of a one-step hydrothermal method, so that the small biological molecules, cobalt and molybdenum disulfide can be compounded to generate the small biological molecule-based cobalt / molybdenum disulfide composite material. The composite material has high electrochemical hydrogen evolution performance and catalytic activity, can be comparable to a commercial 20wt% platinum-carbon catalyst, is simple in synthesis process and low in cost, and has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon nanocomposite material preparation, and in particular relates to a bio-small molecule-based cobalt / molybdenum disulfide composite material and a preparation method and application thereof. Background Art

[0002] The ever-increasing global demand for energy has led to a worsening energy crisis. The energy crisis and environmental pollution caused by the severe consumption of fossil fuels have become key issues that need to be urgently addressed in social development. Advances in clean energy conversion technologies have become a necessary condition for supporting the development of sustainable and renewable energy systems in the future. Hydrogen, with its high energy density and harmless combustion products, can be used as a clean energy source to solve energy problems and reduce carbon emissions, and is considered an ideal secondary energy carrier. Among them, "green hydrogen" produced from renewable energy is hydrogen energy that can meet the needs of clean energy conversion. Currently, the most ideal strategy for producing "green hydrogen" is hydrogen production technology based on water electrolysis via electrocatalytic reactions.

[0003] Precious metals such as Pt, Ir, Ru and their compounds have been shown to have excellent hydrogen and oxygen evolution reaction performance. However, precious metals have small reserves on Earth and high costs, which are not conducive to large-scale promotion and utilization. Therefore, in order to meet the low-cost and high-efficiency industrial supply, there is an urgent need to develop catalysts with high activity, stability and excellent water electrolysis performance. Among the many new electrocatalytic materials, metal-carbon composites have always been a class of materials that researchers have paid close attention to. Metal-carbon-based materials are a new type of composite material that combines metals or metal compounds with carbon materials. Their structure can be easily adjusted to obtain materials with high electrocatalytic performance.

[0004] Currently, carbon materials are readily available from abundant raw materials, particularly biomass or bio-based small molecules, which offer a wealth of green, renewable resources. Alkaloid molecules, with their multiple hydrogen-bonding structures and low HOMO energy levels, can be directly pyrolyzed to form flaky carbon materials. This new class of carbon materials offers the advantages of simple synthesis, sustainability, ease of control, and scalability, making them highly researchable.

[0005] Cathodes composed of transition metal-based electrocatalysts are being extensively studied for the electrocatalytic hydrogen evolution reaction (HER). Their materials mainly include metal carbides, metal sulfides, metal nitrides, and metal phosphides. Among them, transition metal disulfides are low-cost material systems with strong engineering versatility and have recently emerged as potential candidates that can significantly promote hydrogen evolution. Molybdenum disulfide, as a representative transition metal dichalcogenide-based catalyst, has been widely studied in the field of catalytic hydrogen evolution reaction (HER). However, the limited edge active sites and poor conductivity of crystalline MoS2 are the key factors limiting its HER performance.

[0006] Studies have shown that cobalt is dispersed at the atomic level in Co-MoS2, which not only helps to improve the utilization rate of metal atoms, but also increases the number of active sites, thereby accelerating the electron transfer rate and further improving the electrocatalytic hydrogen evolution performance. Therefore, cobalt doping can provide more active sites for the prepared catalyst. However, when combining metals with carbon materials to improve catalytic performance, some issues must be considered, such as how to ensure that the metal and the biological small molecule carbon material are tightly combined to avoid phase separation or interface defects; how to optimize the morphology and structure of the composite material so that its active sites can be fully exposed; and the stability of the catalyst during long-term use must also be considered, such as preventing the agglomeration, shedding or oxidation of molybdenum disulfide to ensure the durability of its catalytic performance. These are still quite challenging. Summary of the Invention

[0007] To seek more efficient methods for combining small biomolecules with metal compounds, the present invention provides a cobalt / molybdenum disulfide composite material based on small biomolecules, as well as its preparation method and application. This method, which requires no template or pretreatment agent, directly uses small biomolecules as precursors. Through a one-step hydrothermal process and sulfurization treatment, the small biomolecules are combined with metallic cobalt and molybdenum disulfide, resulting in a composite material with high hydrogen evolution performance and catalytic activity.

[0008] To achieve the above object, the present invention adopts the following technical solutions: One of the purposes of the present invention is to provide a method for preparing a bio-small molecule-based cobalt / molybdenum disulfide composite material, which comprises the following steps: 1) The biomolecules are placed in a high-temperature tube furnace for high-temperature carbonization to obtain biomolecule carbon materials; 2) uniformly dispersing the bio-small molecule carbon material obtained in step 1), metal cobalt, and molybdenum disulfide in N,N-dimethylformamide (DMF) to obtain a mixed solution; adding a sulfur source after stirring, and transferring the mixture into a reactor after mixing. The reactor is placed in an oven for heating and static reaction; after the reaction is completed, the reactor is removed from the oven, naturally cooled, vacuum filtered, dried, and ground to obtain a composite material; 3) The composite material obtained in step 2) is placed in a high-temperature tube furnace again for vulcanization treatment, and then naturally cooled and ground to obtain the bio-small molecule-based cobalt / molybdenum disulfide composite material.

[0009] Furthermore, the bio-small molecule in step 1) is selected from any one or more of adenine, guanine, xanthine, hypoxanthine, cytosine, and uracil.

[0010] Furthermore, the temperature of the high-temperature carbonization in step 1) is 800-1100°C, and the time is 2 h.

[0011] Furthermore, the molar ratio of the bio-small molecule carbon material to the cobalt and molybdenum elements used in step 2) is 2:1:7 to 6:1:7.

[0012] Furthermore, in step 2), the sulfur source is added after stirring for 3 h.

[0013] Furthermore, the sulfur source in step 2) includes any one or more of thiourea, carbon disulfide, and thioacetamide.

[0014] Furthermore, in step 2), the molar ratio of the amount of the sulfur source added to the solid matter in the mixed solution is 1:1 to 4:1.

[0015] Furthermore, in step 2), the temperature of the heating and standing reaction is 160-200° C., and the time is 12-36 h.

[0016] Furthermore, in step 3), sulfur powder needs to be added during the sulfurization treatment.

[0017] Furthermore, the mass ratio of the sulfur powder to the composite material is 5:1 to 15:1.

[0018] Furthermore, in step 3), the temperature of the sulfurization treatment is 300-600° C., and the time is 1-3 h.

[0019] The second purpose of the present invention is to protect a bio-small molecule-based cobalt / molybdenum disulfide composite material prepared by the above method.

[0020] The third purpose of the present invention is to protect the application of the bio-small molecule-based-cobalt / molybdenum disulfide composite material as an electrocatalyst, specifically, to protect the application of the bio-small molecule-based-cobalt / molybdenum disulfide composite material as an electrocatalyst for hydrogen evolution reaction, oxygen evolution reaction or redox reaction.

[0021] The present invention is based on the hydrothermal reaction and then performs a sulfurization treatment to prepare a bio-small molecule-based cobalt / molybdenum disulfide composite material. On the one hand, hydrothermal sulfurization has a higher sulfurization effect and can more deeply introduce sulfur elements into the material structure, thereby forming a more uniform sulfurized layer, so that the material can still remain stable under high temperature or harsh environment; on the other hand, the synthesis method not only retains the advantage of the structural diversity of bio-small molecule carbon materials, but also utilizes the high catalytic activity of metals, thereby significantly improving the electrocatalytic performance of the composite material and broadening its application range in the field of electrocatalysis. In terms of catalytic performance, due to its structural characteristics, the edge active centers on the (002) surface of the molybdenum disulfide nanoflower sheet can more effectively contact the hydrogen ions in the solution, thereby significantly reducing the resistance of electrons to the transmission between the molybdenum disulfide layers. In addition, the bio-based small molecule carbon material shows good performance in electronic conduction, further reducing the resistance between the two phases of the catalyst.

[0022] Compared with the prior art, the present invention has the following advantages: (1) The synthesis process is simple, environmentally friendly, and low-cost, making it suitable for large-scale industrial production.

[0023] (2) The multiple hydrogen bond interactions and structural diversity between bio-small molecules can lead to the self-assembly of new carbon materials. This type of bio-small molecule carbon material exhibits the advantages of simple synthesis, sustainability, easy regulation, and scalability, and has strong research value and application prospects.

[0024] (3) Without any template or pretreatment agent, a sulfurization treatment is performed on the basis of a one-step hydrothermal method to synthesize a bio-small molecule-based cobalt / molybdenum disulfide composite material by combining the bio-small molecule with metal cobalt and molybdenum disulfide. Compared with a single hydrothermal reaction, the electrochemical hydrogen evolution performance of the material can be improved.

[0025] (4) The composite material has high catalytic activity and exhibits excellent electrocatalytic performance when applied to electrochemical hydrogen evolution catalysis. It is superior to most current molybdenum-based hydrogen evolution catalysts and is very close to the hydrogen evolution performance of commercial 20 wt% platinum-carbon catalysts. It also has excellent electrochemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FESEM images of Co@CX (a), MoS2@CX (b) and Co / MoS2@CX (c) prepared in the examples.

[0027] Figure 2 LSV performance diagram (a) and corresponding Tafel slope diagram (b) of CX, Co@CX, MoS2@CX, Co / MoS2-CX and Co / MoS2@CX prepared in the examples applied to HER test in 1 M KOH.

[0028] Figure 3 XRD spectra of CX, Co@CX, MoS2@CX, Co / MoS2-CX and Co / MoS2@CX prepared in the examples. DETAILED DESCRIPTION

[0029] A bio-small molecule-based cobalt / molybdenum disulfide composite material, the preparation of which comprises the following steps: 1) The biomolecules were placed in a high-temperature tube furnace and carbonized at 800-1100°C for 2 h to obtain biomolecule carbon materials; 2) The biomolecule carbon material obtained in step 1), metallic cobalt, and molybdenum disulfide are uniformly dispersed in N,N-dimethylformamide (DMF) at a molar ratio of 2:1:7 to 6:1:7 to obtain a mixed solution; after stirring for 3 hours, a sulfur source is added at a mass ratio of 5:1 to 15:1 to the solid matter in the mixed solution, and the mixture is transferred to a reactor. The reactor is placed in an oven and heated at 160°C to 200°C for 12 to 36 hours. After the reaction is completed, the reactor is removed from the oven, cooled naturally, vacuum filtered, dried, and ground to obtain a composite material; 3) The composite material obtained in step 2) is placed in a high-temperature tube furnace again, sulfur powder is added at a mass ratio of 5:1 to 15:1 to the composite material, and sulfurization treatment is performed at 300-600°C for 1-3 hours. After natural cooling and grinding, a bio-small molecule-based cobalt / molybdenum disulfide composite material is obtained.

[0030] Wherein, the biological small molecule in step 1) is selected from any one or more of adenine, guanine, xanthine, hypoxanthine, cytosine, and uracil.

[0031] The sulfur source in step 2) includes any one or more of thiourea, carbon disulfide, and thioacetamide.

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] The test conditions in the examples are as follows: the scanning electron microscope (SEM) test instrument model is Regulus8100; the HER performance test is carried out using a Shanghai Chenhua CHI660e electrochemical workstation. The HER electrocatalytic performance of the sample is tested in 1 M KOH. Before the test, the electrolyte is purged with nitrogen for 30 minutes. The test is carried out in a three-electrode electrolytic cell, in which the counter electrode is a carbon rod electrode, the reference electrode is an Ag / AgCl electrode, and the catalyst is supported on carbon paper with a loading of 1 mg / cm 2 X-ray powder diffraction (XRD) was performed using a RIGAKU Ultima IV with a Cu-Ka (x = 1.5406A) radiation source and a graphite monochromator. The operating voltage was 35 kV, the operating current was 35 mA, the scanning step was 0.02°, and the scanning speed was 5° min. -1 , the scanning range is 5° to 80°, and the experimental data are analyzed using the software MDIJade6.5.

[0034] Example 1: S1: Place 2 g of xanthine in a high-temperature tube furnace and carbonize it at 1000 °C for 2 h to obtain a black bio-small molecule carbon material, which is denoted as CX.

[0035] S2: Take 100 mg of the biological small molecule carbon material obtained in S1 and 0.029 g Co(NO3)2·6H2O and evenly disperse them in 30 mL N,N dimethylformamide (DMF), and stir to obtain a mixed solution; then put the obtained mixed solution into a 50 mL reactor, place the reactor in an oven, heat it to 180°C, let it react for 24 hours, then take it out, naturally cool to room temperature, vacuum filter it, and place it in a 60°C oven to dry for 12 hours, and then grind it with a mortar to obtain a composite material, recorded as Co-CX.

[0036] S3: Take 50 mg of the composite material obtained from S2 and place it in the middle position of a high-temperature tube furnace. Heat it to 500 °C at a rate of 5 °C / min. After carbonization for 2 h, cool it naturally and grind it thoroughly to obtain a bio-small molecule-based cobalt composite material, which is recorded as Co@CX.

[0037] Example 2: S1: Place 2 g of xanthine in a high-temperature tube furnace and carbonize it at 1000 °C for 2 h to obtain a black bio-small molecule carbon material, which is denoted as CX.

[0038] S2: Take 100 mg of the bio-small molecule carbon material obtained in S1 and 0.123 g (NH4)6Mo7O 24 4H2O was uniformly dispersed in 30 mL of N,N-dimethylformamide (DMF) and stirred to obtain a mixed solution. After stirring for 3 h, 0.228 g of CS(NH)2 was added. The resulting mixed solution was then placed in a 50 mL reactor, which was placed in an oven and heated to 180°C. The reactor was allowed to react for 24 h before being taken out and naturally cooled to room temperature. After vacuum filtration, the mixture was dried in an oven at 60°C for 12 h and then ground in a mortar to obtain a composite material, designated as MoS2-CX.

[0039] S3: Take 50 mg of the composite material obtained by S2 and place it in the downstream of a high-temperature tube furnace, and place 500 mg of sulfur powder upstream to assist in sulfurization treatment. The temperature is raised to 500 °C at a rate of 5 °C / min. After sulfurization for 2 hours, it is naturally cooled and fully ground to obtain a bio-small molecule-based molybdenum disulfide composite material, which is recorded as MoS2@CX.

[0040] Example 3: S1: Place 2 g of xanthine in a high-temperature tube furnace and carbonize it at 1000 °C for 2 h to obtain a black bio-small molecule carbon material, which is denoted as CX.

[0041] S2: 100 mg of the bio-small molecule carbon material obtained in S1, 0.029 g Co(NO3)2·6H2O and 0.123 g (NH4)6Mo7O 24 4H2O was evenly dispersed in 30 mL of N,N-dimethylformamide (DMF) and stirred to obtain a mixed solution. After stirring for 3 h, 0.228 g of CS(NH)2 was added. The resulting mixed solution was then placed in a 50 mL reactor, which was placed in an oven and heated to 180°C. The reactor was allowed to react for 24 h before being taken out and naturally cooled to room temperature. After vacuum filtration, the mixture was dried in an oven at 60°C for 12 h and then ground in a mortar to obtain a composite material, designated as Co / MoS2-CX.

[0042] Example 4: S1: 2 g of xanthine was placed in a high-temperature tube furnace and carbonized at 1000 °C for 2 h to obtain a black bio-small molecule carbon material, which was recorded as CX.

[0043] S2: 100 mg of the bio-small molecule carbon material obtained in S1, 0.029 g Co(NO3)2·6H2O and 0.123 g (NH4)6Mo7O 24 4H2O was evenly dispersed in 30 mL of N,N-dimethylformamide (DMF) and stirred to obtain a mixed solution. After stirring for 3 h, 0.228 g of CS(NH)2 was added. The resulting mixed solution was then placed in a 50 mL reactor, which was placed in an oven and heated to 180°C. The reactor was allowed to react for 24 h before being taken out and naturally cooled to room temperature. After vacuum filtration, the mixture was dried in an oven at 60°C for 12 h and then ground in a mortar to obtain a composite material, designated as Co / MoS2-CX.

[0044] S3: Take 50 mg of the composite material obtained from S2 and place it in the downstream of a high-temperature tube furnace, and place 500 mg of sulfur powder upstream for sulfurization treatment. The temperature is raised to 500 °C at a rate of 5 °C / min. After sulfurization for 2 h, it is naturally cooled and fully ground to obtain a bio-small molecule-based cobalt / molybdenum disulfide composite material, which is recorded as Co / MoS2@CX.

[0045] The prepared Co@CX, MoS2@CX and Co / MoS2@CX were observed using field emission scanning electron microscopy (FESEM). Figure 1 .like Figure 1As shown in the figure, simple metal cobalt doping has no obvious effect on the morphology of the biological small molecule carbon material, which still maintains a flaky graphitized structure (a); after the transition metal molybdenum disulfide is doped into the biological small molecule carbon material, the original flaky graphitized structure is transformed into a three-dimensional structure with nanoflowers (b); and when cobalt and molybdenum disulfide are co-doped into the biological small molecule carbon material, the formation of nanoflowers is more significant (c). This morphological change not only increases the exposure of active sites, but also improves the electron transfer efficiency and the mechanical strength of the material by forming a three-dimensional network structure, further improving the catalytic performance and stability of the material.

[0046] The HER performance of the prepared CX, Co@CX, Co / MoS2-CX, MoS2@CX and Co / MoS2@CX was tested by linear voltammetry (LSV). Figure 2 .like Figure 2 As shown, in 1 M KOH solution, when it reaches 10 mA / cm 2 At a current density of 1.5 wt%, the overpotentials of CX, Co@CX, MoS2@CX, Co / MoS2-CX and Co / MoS2@CX were 471 mV, 303 mV, 177 mV, 103 mV and 53 mV, respectively, indicating that the composite material with CX as the carrier and co-doped with cobalt and molybdenum disulfide has the best HER performance after further sulfurization (a), which is close to the hydrogen evolution catalytic performance of commercial 20 wt% platinum-carbon catalyst (37 mV). Further, based on the obtained LSV curve data, the Tafel slope curve (b) was obtained using the formula η=a+b×log |j|. The results showed that the Tafel slopes of CX, Co@CX, MoS2@CX, Co / MoS2-CX and Co / MoS2@CX were 181.63 mV / Dec, 132.92 mV / Dec, 90.32 mV / Dec, 124.39 mV / Dec and 54.13 mV / Dec, respectively, indicating that Co / MoS2@CX has excellent kinetics and its Tafel slope is smaller than that of commercial Pt / C catalyst (56 mV / Dec).

[0047] The phase composition of the samples was analyzed by X-ray powder diffraction (XRD). Figure 3 shown. Figure 3It can be seen that CX has broad diffraction peaks near 26° and 43° (corresponding to the (002) and (100) crystal planes of graphite, respectively), indicating the presence of a disordered graphitized structure. Sample Co@CX exhibits characteristic diffraction peaks at 41.68°, 44.76°, and 47.57°. Comparison with the standard PDF card shows that these peaks are attributed to Co (PDF#97-005-3806), indicating that metallic cobalt has been doped into the carbon material. Compared to CX, the spectrum of sample MoS2@NG exhibits diffraction peaks attributed to MoS2 (PDF#04-008-2232), indicating that high-temperature sulfurization can effectively generate the MoS2 phase. Comparing the samples Co / MoS2-CX and Co / MoS2@CX, it can be seen that the diffraction peaks of Co and MoS2 in Co / MoS2-CX are not obvious because it has not been subjected to high-temperature sulfurization, while the spectrum of Co / MoS2@CX shows characteristic diffraction peaks belonging to both Co and MoS2 phases. This further illustrates that sulfurization on the basis of hydrothermal reaction can better integrate the metal components into the material structure, thereby making the resulting material have better catalytic activity and stability.

[0048] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a bio-small molecule-based cobalt / molybdenum disulfide composite material, characterized by: The following steps are involved: 1) The biomolecules are placed in a high-temperature tube furnace for high-temperature carbonization to obtain biomolecule carbon materials; 2) uniformly dispersing the bio-small molecule carbon material obtained in step 1), metal cobalt, and molybdenum disulfide in N,N-dimethylformamide to obtain a mixed solution; adding a sulfur source after stirring, and transferring the mixture into a reactor for heating and allowing to react; after the reaction is completed, naturally cooling the reactor, vacuum filtering, drying, and grinding to obtain a composite material; 3) The composite material obtained in step 2) is placed in a high-temperature tube furnace again for vulcanization treatment, and then naturally cooled and ground to obtain the bio-small molecule-based cobalt / molybdenum disulfide composite material.

2. The preparation method according to claim 1, wherein: Step 1) The biomolecule is selected from any one or more of adenine, guanine, xanthine, hypoxanthine, cytosine, and uracil.

3. The preparation method according to claim 1, wherein: In step 1), the high-temperature carbonization temperature is 800-1100°C and the time is 2 h.

4. The preparation method according to claim 1, wherein: The molar ratio of the bio-small molecule carbon material to the cobalt and molybdenum elements used in step 2) is 2:1:7 to 6:1:

7.

5. The preparation method according to claim 1, wherein: In step 2), the molar ratio of the sulfur source added to the solid matter in the mixed solution is 1:1 to 4:1; the sulfur source includes any one or more of thiourea, carbon disulfide, and thioacetamide.

6. The preparation method according to claim 1, wherein: Step 2) The temperature of the heating and standing reaction is 160-200°C and the time is 12-36 hours.

7. The preparation method according to claim 1, wherein: Step 3) The temperature of the sulfurization treatment is 300-600°C and the time is 1-3 hours.

8. A bio-small molecule-based cobalt / molybdenum disulfide composite material prepared by the method according to any one of claims 1 to 7.

9. Use of the bio-small molecule-based cobalt / molybdenum disulfide composite material as claimed in claim 8 as an electrocatalyst.

10. The use according to claim 9, characterized in that: The electrocatalyst is applied to hydrogen evolution reaction, oxygen evolution reaction or redox reaction.

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