A MoS2@PNAC composite material, its preparation method, and its application in hydrogen evolution reaction.

Abstract

This invention belongs to the field of electrocatalytic materials, providing a MoS2@PNAC composite material, its preparation method, and its application in the hydrogen evolution reaction. The preparation method of the MoS2@PNAC composite material includes: S1, mixing polyethylene terephthalate (PET) with MgO and performing pyrolysis; after pyrolysis, acid washing removes residual MgO, and the resulting acid-washed product is washed and dried to obtain plastic-derived carbon; S2, activating the plastic-derived carbon to obtain plastic-derived activated carbon; S3, nitrogen-doping the plastic-derived activated carbon to obtain plastic-derived nitrogen-doped activated carbon; S4, mixing the plastic-derived nitrogen-doped activated carbon with a sulfur source and a molybdenum source, and performing a hydrothermal reaction to obtain the MoS2@PNAC composite material. The composite material of this invention exhibits high HER catalytic activity, low overpotential, and strong cycle stability in alkaline systems, making it suitable for alkaline water electrolysis hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials, specifically relating to a MoS2@PNAC composite material, its preparation method, and its application in the hydrogen evolution reaction (HER), aiming to improve hydrogen evolution efficiency and reduce the overpotential of the reaction. Background Technology

[0002] Hydrogen, as a clean energy source, has broad application prospects. In the process of producing hydrogen through water electrolysis, the efficiency of the hydrogen evolution reaction (HER) at the cathode directly determines the overall energy consumption and production cost. Currently, molybdenum-based materials such as MoS2 are widely studied as non-noble metal electrocatalysts for HER, exhibiting good catalytic performance under alkaline conditions. However, the poor conductivity and limited number of active sites of MoS2 materials restrict its catalytic performance.

[0003] To improve the catalytic performance of MoS2, it is often used in combination with other materials. For example, using carbon-based materials such as activated carbon (AC) as a support can effectively increase the surface active sites of MoS2 and improve its conductivity. However, existing carbon-based supports mostly use carbon fiber felt, graphene aerogel, etc., and catalysts formed by supporting MoS2 on these supports have drawbacks such as high overpotential and insufficient stability in alkaline water electrolysis scenarios.

[0004] Therefore, developing carbon-based supports that are adapted to alkaline systems and have better performance has become the key to improving the performance of MoS2-based HER catalysts. Summary of the Invention

[0005] To address the issues of high overpotential and insufficient stability in existing carbon-based catalysts supported on MoS2 during alkaline water electrolysis, this invention provides a MoS2@PNAC composite material, its preparation method, and its application in hydrogen evolution reactions.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a MoS2@PNAC composite material, comprising: S1, polyethylene terephthalate is mixed with MgO and pyrolyzed; after pyrolysis, residual MgO is removed by acid washing, and the resulting acid-washed product is washed and dried to obtain plastic-derived carbon; S2, activate the plastic-derived carbon to obtain plastic-derived activated carbon; S3, Nitrogen doping of plastic-derived activated carbon yields nitrogen-doped plastic-derived activated carbon; S4, plastic-derived nitrogen-doped activated carbon is mixed with a sulfur source and a molybdenum source and subjected to a hydrothermal reaction to obtain the MoS2@PNAC composite material.

[0007] Preferably, in S1, the mass ratio of polyethylene terephthalate to MgO is 1:(1~3).

[0008] Preferably, in S1, the pyrolysis temperature is 850~950℃.

[0009] Preferably, S2 specifically involves: mixing plastic-derived carbon with KOH, activating it by heat treatment under a protective atmosphere, and then washing and drying the resulting product to obtain plastic-derived activated carbon.

[0010] Preferably, S3 specifically involves: subjecting plastic-derived activated carbon to a hydrothermal reaction with urea to obtain plastic-derived nitrogen-doped activated carbon.

[0011] Preferably, in S4, the molybdenum source is (NH4)6Mo7O 24 ·4H2O, the sulfur source is thiourea.

[0012] Furthermore, in S4, the hydrothermal reaction temperature is 170~190℃.

[0013] Preferably, in the MoS2@PNAC composite material, the mass ratio of plastic-derived nitrogen-doped activated carbon to MoS2 is (0.25~1.0):1.

[0014] Secondly, the present invention provides a MoS2@PNAC composite material obtained by the preparation method described above.

[0015] Secondly, the present invention provides the application of the MoS2@PNAC composite material as an electrocatalyst in the hydrogen evolution reaction.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes MgO as a template to pyrolyze polyethylene terephthalate (PET), followed by activation, nitrogen doping, and hydrothermal composite processes to obtain a MoS2@PNAC composite material with controllable structure and excellent performance. Firstly, the plastic-derived carbon support prepared using MgO as a template is activated, resulting in plastic-derived activated carbon rich in mesoporous and microporous structures. The nitrogen adsorption-desorption isotherm exhibits a typical type IV curve, with an H4 type hysteresis line appearing in the P / P0 = 0.4-0.95 range. The mesopore size is concentrated in the 5-20 nm range, while the micropore size is mainly distributed around 0.6 nm, resulting in a specific surface area as high as 200.15 m². 2 / g provides abundant loading sites and good electron transport channels for MoS2. Secondly, compared with transition metal oxide catalysts such as ZnO, Fe2O3, and Co3O4 (which participate in the decarboxylation reaction during polyester carbonization, easily leading to metal ions remaining in the carbon skeleton, competing with MoS2 for electrons and causing catalytic site poisoning), this invention uses MgO as a physical template agent. It only regulates the pore structure of the carbon material through the space occupation effect, does not participate in the chemical reaction of polyethylene terephthalate pyrolysis, and can be completely removed by acid washing, resulting in a carbon support without metal residue. Thanks to the adaptability of the carbon support pore structure and the characteristic of no metal residue, the composite material of this invention has significant advantages in HER catalytic performance and stability in alkaline systems: 1) higher catalytic activity and significantly lower overpotential at 10 mA·cm -2 At the specified current density, the catalyst of this invention exhibits an overpotential of only 117 mV, demonstrating outstanding hydrogen evolution catalytic activity; 2) the reaction kinetics are faster, and the Tafel slope is superior, with the catalyst of this invention having a Tafel slope of 55.07 mV·dec. -1 3) Excellent long-term stability and higher current density retention rate: after 24 hours of continuous catalysis, the current density retention rate of the catalyst of this invention reaches 92%, effectively suppressing the poisoning phenomenon of catalytic sites caused by metal residues; 4) Extremely strong cycle stability and superior structural integrity: after 1000 CV cycles, the overpotential of the catalyst of this invention only increases by 8 mV, indicating good structural integrity of the carbon support, which is suitable for the long-term catalytic application requirements of hydrogen evolution reaction. In summary, this invention uses MgO as a physical template agent to pyrolyze polyethylene terephthalate, obtaining a MoS2@PNAC composite material with controllable structure, excellent conductivity, abundant active sites, and excellent stability, which is suitable for the field of alkaline water electrolysis for hydrogen production. Attached Figure Description

[0017] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The image shows SEM images of PNAC and MoS2@PNAC-0.5 in Example 1.

[0019] Figure 2 The image shows the EDS plot of MoS2@PNAC-0.5 in Example 1.

[0020] Figure 3The XRD patterns and Raman spectra of PNAC and MoS2@PNAC-0.5 in Example 1 are shown below: (a) XRD pattern of PNAC; (b) Raman spectrum of PNAC; (c) XRD pattern of MoS2@PNAC-0.5; (d) Raman spectrum of MoS2@PNAC-0.5.

[0021] Figure 4 The image shows the XPS plot of MoS2@PNAC-0.5 in Example 1.

[0022] Figure 5 The following are the nitrogen adsorption-desorption isotherms and pore size distribution diagrams of MoS2@PNAC-0.5 in Example 1: (a) is the nitrogen adsorption-desorption isotherm; (b) is the pore size distribution diagram.

[0023] Figure 6 The electrochemical performance of MoS2@PNAC in Examples 1-3 is shown in (a) and (b) is shown in (c) and (d) at 10, 20, and 50 mA / cm². 2 (c) Overpotential comparison bar chart at current density; (d) Electrochemical impedance spectroscopy (EIS) plot; (c) Tafel slope plot.

[0024] Figure 7 The CV curves are for MoS2@PNAC in Examples 1-3.

[0025] Figure 8 The following are the stability data of MoS2@PNAC-0.5 in Example 1: (a) is a graph showing the stable current density for up to 24 hours; (b) is the polarization curve before and after 1000 CV cycles. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0028] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0029] The preparation method of the MoS2@PNAC composite material of the present invention includes: S1, polyethylene terephthalate is mixed with MgO and pyrolyzed; after pyrolysis, residual MgO is removed by acid washing, and the resulting acid-washed product is washed and dried to obtain plastic-derived carbon; S2, activate the plastic-derived carbon to obtain plastic-derived activated carbon; S3, Nitrogen doping of plastic-derived activated carbon yields nitrogen-doped plastic-derived activated carbon; S4, plastic-derived nitrogen-doped activated carbon is mixed with a sulfur source and a molybdenum source and subjected to a hydrothermal reaction to obtain the MoS2@PNAC composite material.

[0030] Using transition metal oxides as catalysts in polyester carbonization can easily lead to residual impurities on the carbon support, competition for electrons with MoS2, and poisoning of catalytic sites. Furthermore, the pore structure is often monolithic, affecting subsequent catalytic performance. This invention uses MgO as a physical template and pore-forming agent. MgO does not participate in the chemical reaction of polyethylene terephthalate pyrolysis. It regulates the pore structure of the carbon material solely through the space occupancy effect and can be completely removed by acid washing with dilute hydrochloric acid. The carbon material has no metal residue, does not form non-hydrogen evolution active sites, and can regulate the pore structure of the carbon support, improving the active sites and electron transport performance of MoS2. The resulting MoS2@PNAC composite material, as an electrocatalyst, can significantly improve the efficiency and stability of the electrocatalytic water splitting reaction.

[0031] In some embodiments of the present invention, in S1, the mass ratio of polyethylene terephthalate to MgO is 1:(1~3), more preferably 1:2.

[0032] In some embodiments of the present invention, in S1, the pyrolysis temperature is 850~950°C, the time is 2 hours, and the pyrolysis is carried out in an inert atmosphere, such as nitrogen. For example, the preferred pyrolysis temperature is 900°C, and the time is 2 hours. At 800°C, PET carbonization is incomplete, resulting in low carbon yield, poor graphitization, a significant decrease in specific surface area, weak MgO template effect, and easy collapse of the pore structure. At 850~950°C, PET is completely carbonized, MgO is stable, and the mesoporous structure is well developed. Temperatures exceeding 1000°C easily lead to MgO sintering, excessive carbon graphitization, and destruction of the pore structure.

[0033] In this invention, the activation of plastic-derived carbon can be achieved by physical activation or chemical activation. The activation gas used in physical activation can be water vapor or carbon dioxide, etc.; the activating agent used in chemical activation can be potassium hydroxide (KOH), sodium hydroxide (NaOH), etc.

[0034] In some embodiments of the present invention, S2 specifically involves: mixing plastic-derived carbon with KOH, activating it at 800°C for 2 hours under a protective atmosphere, and then washing and drying the resulting product to obtain plastic-derived activated carbon.

[0035] More specifically: Plastic-derived carbon and KOH are ultrasonically mixed evenly in water, then dried. The dried product is further activated at 800°C for 2 hours under a protective atmosphere. The activated product is washed with an acidic solution to remove residual KOH, and then repeatedly washed with water and anhydrous ethanol, and dried to obtain plastic-derived activated carbon.

[0036] The mass ratio of plastic-derived carbon to KOH can be 1:2, the protective atmosphere can be, for example, nitrogen, and the acidic solution can be 1 M HCl.

[0037] In this invention, nitrogen doping of plastic-derived activated carbon can be performed using either high-temperature gas-phase doping or a combined liquid-phase-pyrolysis method. The preferred method in this invention is the combined liquid-phase-pyrolysis method, using urea as the nitrogen source for nitrogen doping.

[0038] In some embodiments of the present invention, S3 specifically involves: mixing plastic-derived activated carbon with urea in water and carrying out a hydrothermal reaction to obtain plastic-derived nitrogen-doped activated carbon.

[0039] For example, plastic-derived activated carbon and urea are dissolved in water, ultrasonically mixed, and then hydrothermally reacted at 170~190°C for 12 hours. The resulting product is repeatedly washed with water and anhydrous ethanol and then dried to obtain plastic-derived nitrogen-doped activated carbon.

[0040] The mass ratio of plastic-derived activated carbon to urea is 1:(3~8), more preferably 1:(4~6), and most preferably 1:5. A mass ratio less than 1:3 results in excessively low nitrogen content and weak electrocatalytic improvement; a ratio greater than 1:8 leads to a severe urea excess, producing large amounts of NH3 and melamine-like byproducts, causing a decrease in catalytic activity instead of an increase. Therefore, the mass ratio of plastic-derived activated carbon to urea should be controlled at 1:(3~8).

[0041] In some embodiments of the present invention, in step S4, the molybdenum source is (NH4)6Mo7O 24 ·4H2O, the sulfur source is thiourea, (NH4)6Mo7O 24 The mass ratio of 4H₂O to thiourea is 1:(1.5~2.5), for example, 1:2. (NH₄)₆Mo₇O 24 When the mass ratio of 4H₂O to thiourea is 1:1, sulfur is severely insufficient, making it almost impossible to form pure MoS₂. A large amount of unsulfurized Mo oxides (such as MoO₃ and MoO₂) will inevitably be present. (NH₄)₆Mo₇O 24 When the mass ratio of 4H2O to thiourea is 1:1.5, it just meets the "minimum safe excess" requirement, and can ensure that the sulfidation is basically complete under standard hydrothermal conditions (180℃, 12h).

[0042] In some embodiments of the present invention, in S4, the temperature of the hydrothermal reaction is 170~190°C and the time is 12 hours.

[0043] In some embodiments of the present invention, the mass ratio of plastic-derived nitrogen-doped active carbon to MoS2 in the MoS2@PNAC composite material is (0.25~1.0):1.

[0044] The MoS2@PNAC composite material prepared by the above method of the present invention has good electrocatalytic activity and stability, and can be used as an electrocatalyst for catalyzing hydrogen evolution reaction in alkaline water electrolysis.

[0045] Example 1 Step 1, Precursor Preparation and Pyrolysis: Cut the waste PET empty bottles into 2 mm × 2 mm fragments, wash them alternately with deionized water and ethanol to remove surface impurities, and then dry them at 70°C for 4 hours.

[0046] Step 2: Purification to obtain PC: 2 g of PET prepared in Step 1 was thoroughly mixed with 4 g of MgO and pyrolyzed in a tube furnace under N2 atmosphere at 900°C for 2 hours. After pyrolysis, the resulting black powder was collected, soaked in 1 M HCl to remove residual MgO, and then repeatedly washed with deionized water and anhydrous ethanol to remove impurities. Finally, the washed powder was dried at 60°C to obtain plastic-derived carbon, labeled as PC.

[0047] Step 3: High-temperature heat treatment activation: Mix 2 g of PC prepared in Step 2 with 4 g of KOH and dissolve in deionized water, then sonicate the solution for 6 hours. Dry the mixture at 80°C for 12 hours. Next, place the dried mixture in a tube furnace and heat treat and activate it at 800°C for 2 hours under a N2 atmosphere.

[0048] Step 4: Post-processing purification to obtain PAC: The powder obtained in Step 3 was thoroughly washed with 1 M HCl to remove residual KOH, and the pH was adjusted to 7. Then, it was repeatedly washed with deionized water and anhydrous ethanol to remove impurities. Finally, the washed powder was dried at 60°C to obtain plastic-derived activated carbon, labeled as PAC.

[0049] Step 5: Synthesis of Plastic-Derived Nitrogen-Doped Activated Carbon (PNAC): 2 g of PAC powder prepared in Step 4 was mixed with 10 g of urea and dissolved in 50 mL of deionized water. The mixture was sonicated for 6 hours, then transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 hours. The resulting precipitate was repeatedly washed with deionized water and anhydrous ethanol, and dried at 60°C to obtain plastic-derived nitrogen-doped activated carbon, labeled PNAC.

[0050] Step 6, Synthesis of MoS2@PNAC: 1 g of (NH4)6Mo7O 24 • 4H₂O and 2 g of thiourea were dissolved in 50 mL of deionized water. 0.5 g of PNAC was added to the solution, and the mixture was sonicated for 2 hours to ensure homogeneity. The solution was transferred to a 100 mL PTFE-lined reactor and reacted at 180°C for 12 hours. After the reaction, the reactor was cooled to room temperature, the product was collected, and repeatedly washed with deionized water and anhydrous ethanol to remove impurities. The mixture was dried at 60°C to obtain a black solid, labeled MoS₂@PNAC-0.5.

[0051] Example 2 Step 1, Precursor Preparation and Pyrolysis: Cut the waste PET empty bottles into 2 mm × 2 mm fragments, wash them alternately with deionized water and ethanol to remove surface impurities, and then dry them at 70°C for 4 hours.

[0052] Step 2: Purification to obtain PC: 2 g of PET prepared in Step 1 was thoroughly mixed with 4 g of MgO and pyrolyzed in a tube furnace under N2 atmosphere at 900°C for 2 hours. After pyrolysis, the resulting black powder was collected, soaked in 1 M HCl to remove residual MgO, and then repeatedly washed with deionized water and anhydrous ethanol to remove impurities. Finally, the washed powder was dried at 60°C to obtain plastic-derived carbon, labeled as PC.

[0053] Step 3: High-temperature heat treatment activation: Mix 2 g of PC prepared in Step 2 with 4 g of KOH and dissolve in deionized water, then sonicate the solution for 6 hours. Dry the mixture at 80°C for 12 hours. Next, place the dried mixture in a tube furnace and heat treat and activate it at 800°C for 2 hours under a N2 atmosphere.

[0054] Step 4: Post-processing purification to obtain PAC: The powder obtained in Step 3 was thoroughly washed with 1 M HCl to remove residual KOH, and the pH was adjusted to 7. Then, it was repeatedly washed with deionized water and anhydrous ethanol to remove impurities. Finally, the washed powder was dried at 60°C to obtain plastic-derived activated carbon, labeled as PAC.

[0055] Step 5: Synthesis of Plastic-Derived Nitrogen-Doped Activated Carbon (PNAC): 2 g of PAC powder prepared in Step 4 was mixed with 10 g of urea and dissolved in 50 mL of deionized water. The mixture was sonicated for 6 hours, then transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 hours. The resulting precipitate was repeatedly washed with deionized water and anhydrous ethanol, and dried at 60°C to obtain plastic-derived nitrogen-doped activated carbon, labeled PNAC.

[0056] Step 6, Synthesis of MoS2@PNAC: 1 g of (NH4)6Mo7O 24 • 4H₂O and 2 g of thiourea were dissolved in 50 mL of deionized water. 0.25 g of PNAC was added to the solution, and the mixture was sonicated for 2 hours to ensure homogeneity. The solution was transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 hours. After the reaction, the reactor was cooled to room temperature, the product was collected, and repeatedly washed with deionized water and anhydrous ethanol to remove impurities. The mixture was dried at 60°C to obtain a black solid, labeled MoS₂@PNAC-0.25.

[0057] Example 3 Step 1, Precursor Preparation and Pyrolysis: Cut the waste PET empty bottles into 2 mm × 2 mm fragments, wash them alternately with deionized water and ethanol to remove surface impurities, and then dry them at 70°C for 4 hours.

[0058] Step 2: Purification to obtain PC: 2 g of PET prepared in Step 1 was thoroughly mixed with 4 g of MgO and pyrolyzed in a tube furnace under N2 atmosphere at 900°C for 2 hours. After pyrolysis, the resulting black powder was collected, soaked in 1 M HCl to remove residual MgO, and then repeatedly washed with deionized water and anhydrous ethanol to remove impurities. Finally, the washed powder was dried at 60°C to obtain plastic-derived carbon, labeled as PC.

[0059] Step 3: High-temperature heat treatment activation: Mix 2 g of PC prepared in Step 2 with 4 g of KOH and dissolve in deionized water, then sonicate the solution for 6 hours. Dry the mixture at 80°C for 12 hours. Next, place the dried mixture in a tube furnace and heat treat and activate it at 800°C for 2 hours under a N2 atmosphere.

[0060] Step 4: Post-processing purification to obtain PAC: The powder obtained in Step 3 was thoroughly washed with 1 M HCl to remove residual KOH, and the pH was adjusted to 7. Then, it was repeatedly washed with deionized water and anhydrous ethanol to remove impurities. Finally, the washed powder was dried at 60°C to obtain plastic-derived activated carbon, labeled as PAC.

[0061] Step 5: Synthesis of Plastic-Derived Nitrogen-Doped Activated Carbon (PNAC): 2 g of PAC powder prepared in Step 4 was mixed with 10 g of urea and dissolved in 50 mL of deionized water. The mixture was sonicated for 6 hours, then transferred to a 100 mL polytetrafluoroethylene-lined reactor and reacted at 180°C for 12 hours. The resulting precipitate was repeatedly washed with deionized water and anhydrous ethanol, and dried at 60°C to obtain plastic-derived nitrogen-doped activated carbon, labeled PNAC.

[0062] Step 6, Synthesis of MoS2@PNAC: 1 g of (NH4)6Mo7O 24 • 4H₂O and 2 g of thiourea were dissolved in 50 mL of deionized water. 1 g of PNAC was added to the solution, and the mixture was sonicated for 2 hours to ensure homogeneity. The solution was transferred to a 100 mL PTFE-lined reactor and reacted at 180°C for 12 hours. After the reaction, the reactor was cooled to room temperature, the product was collected, and repeatedly washed with deionized water and anhydrous ethanol to remove impurities. The mixture was dried at 60°C to obtain a black solid, labeled MoS₂@PNAC-1.0.

[0063] The following describes the microscopic characterization and performance testing of the materials prepared in each embodiment.

[0064] (1) Material characterization Scanning electron microscopy (SEM) was used to acquire SEM images of PNAC and MoS2@PNAC-0.5 to analyze surface morphology. Energy-dispersive X-ray spectroscopy (EDS) was used to determine the successful introduction of target elements and their chemical states in MoS2@PNAC-0.5. X-ray diffraction (XRD) was used to record the crystal structures of PNAC and MoS2@PNAC-0.5. Raman spectroscopy was used to acquire Raman spectra of PNAC and MoS2@PNAC-0.5 to analyze their molecular structures. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemical state of MoS2@PNAC-0.5, focusing on detailed spectra of C, Mo, and S. After pretreatment at 120°C under vacuum, nitrogen adsorption-desorption tests were used to obtain the specific surface area and pore size distribution of MoS2@PNAC-0.5 to analyze its pore structure characteristics.

[0065] SEM image of PNAC in Example 1 ( Figure 1 As shown in (a) and (b), the PNAC material exhibits a rich porous structure, with the sample as a whole displaying a loose, continuous microstructure resembling foam. This is attributed to a series of reactions between the template agent MgO and the activator KOH on the material surface, forming defect vacancies. The SEM images of MoS2@PNAC-0.5 (…) Figure 1 As can be clearly observed in (c) to (f), a large number of nanoflower-like multilayer MoS2 nanostructures were formed on the PNAC support.

[0066] Figure 2 The EDS image of MoS2@PNAC-0.5 shows that carbon, nitrogen, molybdenum and sulfur coexist in the MoS2@PNAC-0.5 material, indicating that nitrogen has been successfully doped into PAC to form PNAC, and that Mo and S elements are uniformly distributed in the sample.

[0067] Figure 3 XRD patterns and Raman spectra of PNAC and MoS2@PNAC-0.5 are shown. Figure 3 As shown in (a), the XRD pattern of PNAC shows two broad peaks near 24° and 45°, corresponding to the (002) and (101) crystal planes of graphitic carbon, respectively, indicating the successful synthesis of the graphitic carbon structure. Figure 3 As shown in (c), the Raman spectrum of PNAC at 1342 cm⁻¹ -1 and 1587 cm -1 A characteristic peak exists at 1342 cm⁻¹. -1 The peak corresponds to the D band peak of graphite carbon, confirming that the sample is rich in structural defects; 1587 cm⁻¹ -1 The peak corresponds to the G-band peak (reflecting the sp² hybridization state of carbon atoms and the fundamental vibrational modes of the graphite structure). For example... Figure 3As shown in (b), the XRD data of MoS2@PNAC-0.5 are in high agreement with the standard PDF card of MoS2. The (002) and (100) crystal planes are typical diffraction peaks of MoS2, and their high intensity indicates that MoS2 was successfully synthesized in the composite sample. Figure 3 (d) Comparison of the Raman spectra of MoS2@PNAC-0.5 and MoS2, 376 cm⁻¹ -1 and 406 cm -1 The characteristic peaks at the point correspond to the MoS2E¹2g and A1g vibrational modes coexisting in the two samples, respectively reflecting the different vibrational modes of sulfur atoms relative to molybdenum atoms and between sulfur atoms within the layer plane.

[0068] Figure 4 XPS plot for MoS2@PNAC-0.5. (Example) Figure 4 As shown in (a), the sample contains oxygen, nitrogen, carbon, molybdenum, and sulfur. Figure 4 As shown in (b), the fine C 1s spectrum was fitted with peaks to obtain three peaks at 289.1 eV, 286.1 eV and 284.9 eV, which correspond to carbon in C=O, CO and CC / C=C, respectively, proving that the material contains a large amount of plastic-derived carbon. Figure 4 (c) shows Mo 6+ 3d3 / 2, Mo 4+ 3d3 / 2, Mo 4+ The 3d5 / 2 and S 2s peaks are located at 236.2 eV, 233.1 eV, 229.2 eV, and 226.5 eV, respectively; among which Mo 6+ The 3d3 / 2 indicates the presence of +6 valence molybdenum in the sample, while Mo... 4+ Characteristic peaks prove the presence of +4 valent molybdenum. For example... Figure 4 As shown in (d), the double peaks of sulfur at the 162.8 eV and 160.9 eV energy levels represent S. 2- The 2p¹ / ² and 2p³ / ² peaks, at 161.4 eV, may represent the peak S. 2- The ligand peak at 168.3 eV indicates the presence of sulfur in a high-valence oxidation state (such as sulfate) in the sample.

[0069] Figure 5 The images show the nitrogen adsorption-desorption isotherms and pore size distribution of MoS2@PNAC-0.5. Figure 5 As shown in Figure (a), the nitrogen adsorption-desorption isotherm of MoS2@PNAC-0.5 exhibits a typical Type IV curve, with an H4-type hysteresis loop appearing in the P / P0 = 0.4–0.95 range, indicating that the sample is rich in mesoporous and microporous structures. The calculated specific surface area of ​​the sample is as high as 200.15 m². 2 / g. Figure 5The pore size distribution of the BJH method in (b) shows that the mesopore size is concentrated in the range of 5~20 nm, while the micropore size is mainly distributed around 0.6 nm.

[0070] (2) Performance testing This invention evaluates the performance of the prepared materials, including the following aspects: 1) Electrode preparation: Cut nickel foam into 1 × 2 cm pieces. 2 The flakes were ultrasonically cleaned sequentially for 30 minutes each in 1 M HCl, acetone, anhydrous ethanol, and deionized water. 10 mg of catalyst powder was dissolved in 1 mL of a mixed solution consisting of deionized water, anhydrous ethanol, and 5% Nafion solution, with a deionized water:ethanol:Nafion ratio of 10:9:1. The resulting mixture was ultrasonically treated in a centrifuge tube for 30 minutes and then uniformly coated onto nickel foam to form a working electrode. After drying, the electrode was ready for electrochemical performance testing.

[0071] 2) Electrochemical testing was conducted on a CHI660e electrochemical workstation using a standard three-electrode system with a 1.0 M KOH solution as the electrolyte. A Hg / HgO electrode was used as the reference electrode, a carbon rod as the counter electrode, and a catalyst-coated nickel foam as the working electrode. 3) The electrode was activated by cyclic voltammetry (CV) using linear sweep voltammetry (LSV) at 1 mV s. -1 The activity of the hydrogen evolution reaction was evaluated at the scan rate. 4) Electrochemical double-layer capacitance (CDL): Measured by CV scanning in the non-Radidatic region at scan rates of 20, 40, 60, 80, and 100 mV s. -1 The electrochemically active surface area (ECSA) is estimated using the formula ECSA = CDL / Cs, where Cs is taken as 0.04 mF cm⁻¹ in 1.0 M KOH. -2 ; 5) Electrochemical Impedance (EIS): EIS in the frequency range of 10 6 Up to 10 -2 The vibration occurs within Hz, with an amplitude of 5 mV.

[0072] Figure 6The polarization spectral density (LSV) plot in (a) shows that the hydrogen evolution current density of PNAC as a function of potential is generally lower than that of pure nickel foam substrate, indicating that PNAC has almost no catalytic activity. Although the unsupported MoS2 material has poor conductivity and fewer active sites, its activity is still significantly higher than that of nickel foam. Compared with MoS2 material, the catalytic activity of MoS2@PNAC (MoS2@PNAC-0.5, MoS2@PNAC-0.25, MoS2@PNAC-1.0) with different PNAC contents prepared in Examples 1-3 is further improved, among which MoS2@PNAC-0.5 has the best performance.

[0073] pass Figure 6 (b) at 10, 20, and 50 mA / cm 2 The overpotential comparison histogram at current densities shows that PNAC at 10, 20, and 50 mA / cm²... 2 The highest overpotentials were required at the highest current densities (278, 372, and 490 mV, respectively); while the overpotentials of the MoS2@PNAC samples were significantly lower than those of PNAC and pure MoS2 at all current densities, with MoS2@PNAC-0.5 requiring the lowest overpotential to achieve the same current density (at 10, 20, and 50 mA / cm). 2 The overpotentials at current densities were 117, 134, and 158 mV, respectively. While the performance of MoS2@PNAC-0.25 and MoS2@PNAC-1.0 was slightly lower, it was still superior to unsupported MoS2.

[0074] Figure 6 (c) shows the electrochemical impedance spectroscopy (EIS) plot. The distance between the curve and the horizontal axis represents the charge transfer resistance (Rct). The Rct values ​​of MoS2@PNAC-0.25, MoS2@PNAC-0.5, and MoS2@PNAC-1.0 are 5.98, 3.09, and 4.39 Ω, respectively, all lower than those of nickel foam (76.86 Ω) and pure MoS2 (12.15 Ω). This indicates that MoS2@PNAC has a lower charge transfer resistance, faster electron transport on the electrochemical surface, and higher catalytic activity. Among them, MoS2@PNAC-0.5 has the smallest Rct, corresponding to the optimal catalytic performance, which is consistent with the conclusion of the LSV curve.

[0075] Figure 6 In the middle (d), which is the Tafel slope plot, it can be seen that the Tafel slope of MoS2@PNAC-0.5 is 55.07 mV·dec -1 It is significantly smaller than MoS2@PNAC-0.25 (89.48 mV·dec). -1 ) and MoS2@PNAC-1.0 (74.56 mV·dec -1This indicates that its charge transfer dynamics are faster.

[0076] Figure 7 This is a CV curve graph. Figure 7 Figures (a)-(c) show the CV curves of MoS2@PNAC-0.25, MoS2@PNAC-0.5 and MoS2@PNAC-1.0 at scan rates of 20-100 mV / s. Figure 7 The middle (d) shows the Cdl values ​​of six materials: MoS2@PNAC-0.5 has the largest Cdl (88.98 mF / cm). 2 The concentration was higher than that of MoS2@PNAC-0.25 (64.08 mF / cm). 2 ) and MoS2@PNAC-1.0 (77.56 mF / cm) 2 This indicates that it has the largest active surface area and can expose the most active sites.

[0077] Figure 8 The graphs show the stable current density of MoS2@PNAC-0.5 for up to 24 hours and the polarization curves before and after 1000 CV cycles. From Figure 8 As can be seen in (a), at 10 mA / cm 2 After 24 hours of continuous operation at an overpotential of 117 mV corresponding to the reference current density, the current density only slightly decreased to 92% of the initial value, indicating that the catalyst has good stability. Furthermore, as... Figure 8 As shown in (b), by comparing the polarization curves before and after 1000 CV cycles in the potential range of 0 to -0.20 V (vs RHE), it was found that the LSV curve shifted only slightly towards higher overpotentials after cycling—reaching 10 mA / cm. 2 The overpotential required for the current density increases slightly from the initial 117 mV to 125 mV.

[0078] In summary, it can be seen that PNAC, as a support, combined with MoS2, can improve the conductivity of MoS2-based catalysts, reduce overpotential, and enhance the activity and cycle stability of hydrogen evolution reaction. The MoS2@PNAC composite electrocatalyst of this invention exhibits excellent hydrogen evolution performance, and its preparation method is simple, scalable, and has broad application prospects, particularly suitable for low-cost green hydrogen production.

[0079] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing a MoS2@PNAC composite material, characterized in that, include: S1, polyethylene terephthalate is mixed with MgO and pyrolyzed; after pyrolysis, residual MgO is removed by acid washing, and the resulting acid-washed product is washed and dried to obtain plastic-derived carbon; S2, activate the plastic-derived carbon to obtain plastic-derived activated carbon; S3, Nitrogen doping of plastic-derived activated carbon yields nitrogen-doped plastic-derived activated carbon; S4, plastic-derived nitrogen-doped activated carbon is mixed with a sulfur source and a molybdenum source and subjected to a hydrothermal reaction to obtain the MoS2@PNAC composite material.

2. The method for preparing the MoS2@PNAC composite material according to claim 1, characterized in that, In S1, the mass ratio of polyethylene terephthalate to MgO is 1:(1~3).

3. The method for preparing the MoS2@PNAC composite material according to claim 1, characterized in that, In S1, the pyrolysis temperature is 850~950℃.

4. The method for preparing the MoS2@PNAC composite material according to claim 1, characterized in that, S2 specifically involves mixing plastic-derived carbon with KOH, activating it through heat treatment under a protective atmosphere, and then washing and drying the resulting product to obtain plastic-derived activated carbon.

5. The method for preparing the MoS2@PNAC composite material according to claim 1, characterized in that, S3 specifically involves a hydrothermal reaction of plastic-derived activated carbon with urea to obtain plastic-derived nitrogen-doped activated carbon.

6. The method for preparing the MoS2@PNAC composite material according to claim 1, characterized in that, In S4, the molybdenum source is (NH4)6Mo7O 24 ·4H2O, the sulfur source is thiourea.

7. The method for preparing the MoS2@PNAC composite material according to claim 6, characterized in that, In S4, the hydrothermal reaction temperature is 170~190℃.

8. The method for preparing the MoS2@PNAC composite material according to claim 1, characterized in that, In the MoS2@PNAC composite material, the mass ratio of plastic-derived nitrogen-doped active carbon to MoS2 is (0.25~1.0):

1.

9. The MoS2@PNAC composite material obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the MoS2@PNAC composite material according to claim 9 as an electrocatalyst in the hydrogen evolution reaction.

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