Direct methanol fuel cell catalyst and preparation method thereof
By loading a platinum-iron-cobalt-nickel-copper high-entropy alloy onto carbon nanotubes, the stability and kinetics problems of direct methanol fuel cell catalysts were solved, achieving high ORR and MOR performance, improving catalyst stability and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG SCI-TECH UNIV
- Filing Date
- 2025-12-22
- Publication Date
- 2026-05-05
AI Technical Summary
Existing direct methanol fuel cell catalysts suffer from poor stability and slow kinetics in the methanol oxidation (MOR) and oxygen reduction (ORR) reactions, which limits their commercial application.
A catalyst was prepared by using vertically oriented carbon nanotubes as a conductive network and loading them with a platinum-iron-cobalt-nickel-copper high-entropy alloy through steps such as hydrolysis-pyrolysis, hydrothermal reaction, and plasma reduction, thereby enhancing the catalytic active sites and stability.
This improved the specific surface area and number of active sites of the catalyst, enhanced the electrocatalytic performance of ORR and MOR, improved the stability of the catalyst, and reduced the cost.
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Figure CN121983598A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of methanol fuel cell catalyst technology, specifically to a direct methanol fuel cell catalyst and its preparation method. Background Technology
[0002] Human demand for energy is growing ever stronger and becoming increasingly difficult to meet. Currently, the world's enormous energy demand relies primarily on non-renewable fossil fuels, which have negative environmental impacts. However, with the gradual prosperity of the global economy, reducing fossil fuel consumption and addressing the resulting environmental problems has become an urgent challenge for society. Filling the gap between energy demand and supply, and finding abundant unconventional energy resources, has become a pressing task for modern society.
[0003] Fuel cells, as an emerging clean and efficient energy conversion technology, are gradually becoming a substitute for fossil fuels. Among various types of fuel cells, direct methanol fuel cells are an ideal choice due to their suitability for light vehicles and portable devices. A key strategy for achieving sustainable energy is to develop efficient, economical, and environmentally friendly catalysts to improve the performance of energy storage and conversion devices.
[0004] To date, numerous studies have explored the use of platinum (Pt) and its modified electrocatalysts to improve the efficiency of methanol oxidation. Platinum-based nanocubes, nanorods, nanoflowers, and composite materials of platinum with metal oxides (such as Fe₂O₃, TiO₂, SnO₂, MnO, Cu₂O, and ZnO) and conductive polymers have been widely applied in both acidic and alkaline media. Furthermore, palladium-based materials, transition metal-based materials, metal-organic frameworks (MOFs), and their derivatives have become current research hotspots. Among different types of fuel cells, direct methanol fuel cells are an excellent choice for light vehicles and portable devices. The production of energy storage and conversion equipment using highly mature, economical, and green catalysts can achieve sustainable energy development.
[0005] ORR, as a key reaction in fuel cells and metal-air batteries, has achieved relatively mature development. In contrast, poor stability and slow kinetics make MOR a bottleneck for DMFCs, limiting their commercialization. Summary of the Invention
[0006] One of the technical problems to be solved by the present invention is to provide a direct methanol fuel cell catalyst and its preparation method, which has the characteristics of high specific surface area, multiple active sites, excellent performance, low cost and long-term stability.
[0007] This application provides a direct methanol fuel cell catalyst, the structural unit of which is a vertically oriented carbon nanotube as a conductive network, and a platinum-iron-cobalt-nickel-copper high-entropy alloy is loaded on the conductive network.
[0008] This application also provides a method for preparing a catalyst for a direct methanol fuel cell, specifically including the following steps:
[0009] S1 was used to prepare vertically oriented carbon nanotubes;
[0010] S1.1 The carbon cloth is subjected to hydrolysis and pyrolysis treatment, and a thin layer of silica is loaded on the surface of the carbon cloth;
[0011] S1.2 Carbon nanotubes are grown in situ on the surface of the carbon cloth after the treatment in step S1.1 using chemical vapor deposition. In a high-temperature tube furnace under an inert atmosphere at a temperature of 800-900℃, a carbon source solution is introduced through a micro-injection pump to obtain a hybrid material, denoted as VACNTs@CC.
[0012] S2 hydrothermal reaction supported iron-cobalt-nickel-copper nanosheets to obtain iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes, denoted as FeCoNiCu LDH / VACNTs@CC;
[0013] S3 immersed the obtained iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes in chloroplatinic acid solution to load platinum ions, denoted as PtFeCoNiCu@VACNTs@CC.
[0014] In an argon-hydrogen atmosphere, S4 utilizes radio frequency plasma technology to perform plasma reduction treatment on iron-cobalt-nickel-copper hydroxide@vertically oriented nanotubes that have been soaked in chloroplatinic acid solution, thereby obtaining a direct methanol fuel cell catalyst, denoted as P-PtFeCoNiCu@VACNTs@CC.
[0015] Preferably, before the carbon cloth undergoes hydrolysis and pyrolysis treatment, the carbon cloth is placed in an inert atmosphere and heated at 4-6°C for 1 minute. -1 After the heating rate reaches 800-900℃, hold the temperature for 25-35 minutes to remove the polymer film on the surface of the carbon cloth.
[0016] Preferably, the hydrolysis and pyrolysis treatment in step S1.1 is as follows: first, measure toluene, then add the same amount of tetraethyl orthosilicate and silicon tetrachloride, and then sonicate for 25-35 minutes to obtain the precursor solution. Soak the carbon cloth in the precursor solution for 1 hour, take it out and dry it, keep it at 150-250℃ for 60 minutes, and then keep it at 800-900℃ for 55-65 minutes to load a thin layer of silicon dioxide on the surface of the carbon cloth.
[0017] Preferably, the preparation method of the carbon source solution in step S1.2 is as follows: weigh ferrocene, then measure anhydrous ethanol and xylene, and finally extract ethylenediamine, stir evenly, and the carbon source solution is obtained, wherein ferrocene is 600 mg, anhydrous ethanol is 9.8 ml, xylene is 9.8 ml and ethylenediamine is 0.4 ml.
[0018] Preferably, the preparation process of step S2 includes: dissolving iron transition metal salt, cobalt transition metal salt, nickel transition metal salt, copper transition metal salt, urea and ammonium fluoride in deionized water, stirring thoroughly to dissolve, placing vertically oriented carbon nanotubes, reacting at 110-130℃ for 5-7 hours, after the reaction is completed, cooling and removing, rinsing with deionized water and ethanol, and drying for 6-24 hours.
[0019] Preferably, the iron transition metal salt is one or more of FeSO4, FeCl3, FeCl2, and Fe(NH2SO3)3; the cobalt transition metal salt is one or more of Co(NO3)2·6H2O, CoCl2·6H2O, Co(CH3COO)2·4H2O, CoSO4·6H2O, and CoCl2; and the nickel transition metal salt is NiC. 10 H 14 One or more of O4, NiCl2·6H2O, Ni(NO3)2·6H2O, NiC4H6O4·4H2O, and NiCO3 are used; the copper transition metal salt is one or more of CuCl2·2H2O, CuSO4·5H2O, Cu(CH3COO)2·H2O, and Cu(NO3)2·3H2O.
[0020] Preferably, the molar ratio of FeCl3·3H2O:Co(NO3)2·6H2O:Ni(NO3)2·6H2O:Cu(NO3)2·3H2O is 1:1:1:1.
[0021] Preferably, in step S3, the concentration of the chloroplatinic acid solution is 0.1 mol / L chloroplatinic acid, and the soaking time is 10-14 h.
[0022] Preferably, step S4 specifically involves: placing platinum-loaded iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes into a ceramic boat, placing the ceramic boat into a plasma-enhanced chemical vapor deposition (PECVD) apparatus, introducing argon and hydrogen gas, performing plasma reduction, maintaining the tube temperature at 500°C, the tube pressure at 20 Pa, the discharge power at 100 W, and the discharge time at 30-90 min.
[0023] Compared with the prior art, the present invention has the following advantages:
[0024] This application utilizes a carbon cloth substrate with a larger specific surface area and higher conductivity. Loading vertically oriented carbon nanotubes onto this substrate allows for better loading of metal particles and increases the number of active sites. The HEA (High-Efficiency Alloy) is an alloy composed of five or more elements at high concentrations (5-35 at%), exhibiting advantages such as strong corrosion resistance, abundant atomic interfaces, and high mechanical strength. The introduction of plasma provides more defects and active sites, while simultaneously reducing hydroxides to the alloy, thus improving catalytic activity and stability.
[0025] The direct methanol fuel cell catalyst of this application exhibits excellent ORR and MOR electrocatalytic performance. The introduction of a high-entropy alloy in the preparation method can improve catalytic performance, enhance corrosion resistance, reduce costs, improve structural stability, and regulate electronic properties, resulting in better activity for both the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR). The specific reasons are as follows:
[0026] (1) Vertically oriented carbon nanotubes possess excellent electrical conductivity and provide a large specific surface area. Their vertical alignment allows for more efficient contact with reactants, which is crucial for applications such as catalytic reactions, gas adsorption, and batteries. The high surface area enhances the catalytic activity of electrode materials, particularly by providing more active sites. Vertical alignment further improves conductivity and reduces electron transport resistance within the material. In electrochemical applications, this efficient electron transport helps improve the performance of batteries and supercapacitors, especially for high power density applications. In electrochemical reactions, the structure of vertically oriented carbon nanotubes helps improve the interfacial contact between the electrode and electrolyte, reducing interfacial resistance. For devices such as direct methanol fuel cells (DMFCs), the vertical alignment of carbon nanotubes improves the contact efficiency between reactants and electrodes, thereby enhancing battery performance.
[0027] (2) Loading iron-cobalt-nickel-copper sheet hydroxide onto the surface of vertically oriented carbon nanotubes is to reduce platinum ions and hydroxide together in the next step to form high-entropy alloy particles that adhere to the surface of carbon nanotubes and are not easily detached, thereby improving stability.
[0028] (3) In plasma-enhanced chemical vapor deposition equipment, the introduction of argon-hydrogen plasma can enhance the defects and vacancies of the material, obtain more active sites, and at the same time reduce hydroxides and platinum ions into alloys, making them have excellent activity that can be applied to methanol fuel cells. Attached Figure Description
[0029] Figure 1 The image shows the microstructure of the methanol fuel cell catalyst prepared in Example 1 under a scanning electron microscope (SEM) (scale bar 1 μm).
[0030] Figure 2Linear sweep voltammetry (LSV) plots of oxygen reduction reaction (ORR) for Example 1, Comparative Examples 1, 2, 3, 4, and a commercial Pt / C catalyst;
[0031] Figure 3 Cyclic voltammetry (CV) plots of methanol oxidation (MOR) in Example 1, Comparative Examples 1, 2, 3, 4, and a commercial Pt / C catalyst. Detailed Implementation
[0032] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.
[0033] A direct methanol fuel cell catalyst has a structural unit consisting of vertically oriented carbon nanotubes as a conductive network, on which a platinum-iron-cobalt-nickel-copper high-entropy alloy is loaded.
[0034] Its preparation method specifically includes the following steps:
[0035] (a) Preparation of vertically oriented carbon nanotubes;
[0036] (ii) Hydrothermal reaction loading of iron cobalt nickel copper hydroxide nanosheets to obtain iron cobalt nickel copper hydroxide@vertically oriented carbon nanotubes;
[0037] (iii) Immerse iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes in chloroplatinic acid to load platinum ions;
[0038] (iv) Platinum iron cobalt nickel copper hydroxide@vertically oriented carbon nanotubes were subjected to plasma reduction treatment in an argon-hydrogen atmosphere using radio frequency plasma technology;
[0039] The preparation process in step (II) includes: dissolving iron transition metal salt, cobalt transition metal salt, nickel transition metal salt, copper transition metal salt, urea and ammonium fluoride in deionized water, stirring thoroughly to dissolve, pouring into a polytetrafluoroethylene (PTFE) inner liner, placing vertically oriented carbon nanotubes inside, and then placing the PTFE inner liner into a high-pressure reactor. The reactor is then reacted at 120°C for 6-24 hours. After the reaction is completed and cooled, the reactor is removed, rinsed with deionized water and ethanol, and dried in an oven for 6-24 hours to obtain iron cobalt nickel copper hydroxide@vertically oriented carbon nanotubes, denoted as FeCoNiCu LDH@VACNTs@CC.
[0040] The iron transition metal salt is one or more of FeSO4, FeCl3, FeCl2, and Fe(NH2SO3)3; the cobalt transition metal salt is one or more of Co(NO3)2·6H2O, CoCl2·6H2O, Co(CH3COO)2·4H2O, CoSO4·6H2O, and CoCl2; the nickel transition metal salt is NiC 10 H 14 One or more of O4, NiCl2·6H2O, Ni(NO3)2·6H2O, NiC4H6O4·4H2O, and NiCO3 are used, and the copper transition metal salt is one or more of CuCl2·2H2O, CuSO4·5H2O, Cu(CH3COO)2·H2O, and Cu(NO3)2·3H2O.
[0041] Example 1
[0042] The preparation method of a direct methanol fuel cell catalyst (P-PtFeCoNiCu@VACNTs@CC) supported on the surface of vertically oriented carbon nanotubes using a platinum-iron-cobalt-nickel-copper high-entropy alloy includes the following steps:
[0043] (I) Synthesis of vertically oriented carbon nanotubes:
[0044] Cut a 3*4cm piece 2 Raw carbon cloth is placed in a tube furnace and heated at 5°C for 5 minutes under an inert atmosphere. -1 After the heating rate reaches 850℃, it is kept at that temperature for 30 minutes to remove the polymer film on the surface of the carbon cloth.
[0045] Hydrolysis process: Take a 100mL beaker and a 20mL graduated cylinder. First, use the graduated cylinder to measure 18mL of toluene and transfer it into the beaker. Use a pipette to draw the same amount of tetraethyl orthosilicate and silicon tetrachloride and transfer them into the beaker. Sonicate in an ultrasonic cleaner for 30 minutes to prepare the precursor solution. Transfer the carbon cloth material that has undergone heat treatment in the first step into the beaker and soak it in the precursor solution for 1 hour. Take it out and use water vapor to dry the surface of the carbon cloth material so that a thin layer of silicon dioxide is loaded on the surface of the carbon cloth.
[0046] Pyrolysis process: The material obtained from the hydrolysis process is transferred into a high-temperature tube furnace, and an inert gas (Ar) is introduced. 2) The gas flow rate was set to 200 sccm, and the heating rate of the tube furnace was set to 5℃ / min. The temperature was first maintained at 200℃ for 60 min, and then at 850℃ for 60 min. A thin layer of silica was loaded onto the surface of the carbon cloth after hydrolysis and pyrolysis treatment.
[0047] Carbon nanotubes were grown in situ on the surface of carbon cloth material using chemical vapor deposition (CVD). First, a carbon source solution was prepared. A 100 mL beaker and a 20 mL graduated cylinder were used. 600 mg of ferrocene (the catalyst for carbon nanotube growth) was weighed and transferred into the beaker. Then, 9.8 mL of anhydrous ethanol and xylene (49%) were measured separately using the graduated cylinder. Finally, 400 μL of ethylenediamine (2%) was drawn up using a pipette. The solution was stirred with a glass rod for 30 min and then ultrasonically stirred for 1 h in an ultrasonic cleaner. The prepared solution was then transferred into a 20 mL syringe. The surface-treated carbon cloth material obtained in the second step was placed in a high-temperature tube furnace, and an inert gas (Ar2 or N2) was introduced. 2) When the temperature reaches 850℃, a prepared carbon source solution is simultaneously introduced using a micro-injection pump, ultimately yielding VACNTs@CC hybrid materials.
[0048] (II) Synthesis of iron-cobalt-nickel-copper hydroxide:
[0049] 0.2 mmol FeCl3·3H2O, 0.2 mmol Co(NO3)2·6H2O, 0.2 mmol Ni(NO3)2·6H2O, 0.2 mmol Cu(NO3)2·3H2O, 3.6 mmol urea, and 1.5 mmol ammonium fluoride were dissolved in 40 ml of deionized water and stirred thoroughly until dissolved. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and vertically oriented carbon nanotubes were placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 120 °C for 6 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 12 h to obtain iron-cobalt-nickel-copper hydroxide@oriented carbon nanotubes, denoted as FeCoNiCu LDH@VACNTs@CC.
[0050] (III) Loading of platinum precursor
[0051] The iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes were immersed in chloroplatinic acid to load a platinum precursor; the iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes obtained in step (II) were immersed in chloroplatinic acid with a concentration of 0.1 mol / L for 12 h, and then dried to obtain iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes containing a platinum precursor.
[0052] (iv) Synthesis of Platinum Iron Cobalt Nickel Copper@Vertically Oriented Carbon Nanotubes@Carbon Cloth
[0053] Platinum-loaded iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes were placed in a ceramic boat, which was then placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus. Argon and hydrogen gas were introduced for plasma reduction. The temperature inside the tube was 500℃, the pressure inside the tube was 20Pa, the discharge power was 100W, and the discharge time was 60min. The resulting direct methanol fuel cell catalyst is denoted as P-PtFeCoNiCu@VACNTs@CC.
[0054] The morphology of the P-PtFeCoNiCu@VACNTs@CC sample obtained from the verification example was analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, the P-PtFeCoNiCu@VACNTs@CC sample consists of uniform nanoparticles loaded on vertically oriented carbon nanotubes, exhibiting a stable structure.
[0055] Bifunctional catalytic performance evaluation:
[0056] The electrocatalytic performance of the prepared direct methanol fuel cell catalyst samples was tested using an electrochemical workstation (CHI760E) in a three-electrode setup.
[0057] Preparation of working electrodes for ORR and MOR performance testing: Before using the rotating disk electrode (RDE), the glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder, then repeatedly rinsed with deionized water, ultrasonically dried for several seconds, and dried at room temperature for later use. A 4 mm diameter hole was punched in the prepared carbon cloth, and 5 wt.% Nafion was used as a binder to firmly adhere the direct methanol fuel cell catalyst sample to the electrode. After drying, the sample was tested. As a control, a commercial 20 wt.% Pt / C catalyst was selected for the ORR test and coated onto the carbon cloth for testing. A commercial 20 wt.% Pt / C catalyst was selected for the MOR test, and the preparation method was the same as the above sample. Electrochemical performance testing: A standard three-electrode electrochemical testing system was used during the testing process. The counter electrode was a stone-ground rod electrode, the reference electrode was a saturated calomel electrode (SCE), and the working electrode prepared above was used. The test solution was a 0.1 M H2SO4 solution (pH = 0). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg₂Cl₂) + 0.2415 + 0.059pH. The working electrode was operated at 10 mV / s prior to linear sweep voltammetry (LSV) testing. -1 The scan rate was activated by cyclic voltammetry (CV) for 50 cycles. All electrochemical tests were performed at room temperature.
[0058] The ORR (Orientation-Reduction) LSV (Low-Speed Value) curves of P-PtFeCoNiCu@VACNTs@CC samples and commercial 20 wt.% Pt / C catalyst in 1 M H₂SO₄ solution saturated with O₂ were tested using a rotating disk electrode (RDE) at 1600 rpm. The results are as follows: Figure 2 As shown, the P-PtFeCoNiCu@VACNTs@CC sample exhibits high ORR electrocatalytic activity, with an onset potential of 0.886 V vs. RHE and a half-wave potential of 0.761 V vs. RHE. These values are higher than those of commercial Pt / C catalysts (0.831 V vs. RHE and 0.732 V vs. RHE), indicating that the P-PtFeCoNiCu@VACNTs@CC sample possesses rapid reaction kinetics in the ORR electrocatalytic process.
[0059] The MOR catalytic activity was tested using a rotating disk electrode (RDE) on P-PtFeCoNiCu@VACNTs@CC samples in a saturated N2 solution of 0.5 M H2SO4 + 0.5 M CH3OH. Figure 3 The CV curves of the MOR catalytic performance of the P-PtFeCoNiCu@VACNTs@CC sample are shown, with a mass activity of 2.33 A mg. -1 Pt It outperforms commercial Pt / C catalysts under the same conditions.
[0060] Comparative Example 1
[0061] The preparation method of platinum metal supported catalyst on carbon cloth surface (P-Pt@CC) specifically includes the following steps:
[0062] (I) Synthesis of platinum precursor-supported carbon cloth
[0063] Cut a 3*4cm piece 2 Raw carbon cloth is placed in a tube furnace and heated at 5°C for 5 minutes under an inert atmosphere. -1 After the heating rate reaches 850℃, it is kept at that temperature for 30 minutes to remove the polymer film on the surface of the carbon cloth; the carbon cloth is then immersed in 0.1 mol / L chloroplatinic acid for 12 hours, removed and dried to obtain carbon cloth containing platinum ions.
[0064] (II) Catalysts supported on carbon cloth surface
[0065] Platinum ion-containing carbon cloth was placed in a ceramic boat, which was then placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus. Argon and hydrogen gas were introduced for plasma reduction. The temperature inside the tube was 500°C, the pressure inside the tube was 20 Pa, the discharge power was 100 W, and the discharge time was 60 min. The resulting platinum metal catalyst supported on the surface of the carbon cloth was denoted as P-Pt@CC.
[0066] Bifunctional catalytic performance evaluation:
[0067] The electrocatalytic performance of the prepared direct methanol fuel cell catalyst samples was tested using an electrochemical workstation (CHI760E) in a three-electrode setup.
[0068] Preparation of working electrodes for ORR and MOR performance testing: Before using the rotating disk electrode (RDE), the glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder, then repeatedly rinsed with deionized water, ultrasonically dried for several seconds, and dried at room temperature for later use. A 4 mm diameter hole was punched in the prepared carbon cloth, and 5 wt.% Nafion was used as a binder to firmly adhere the direct methanol fuel cell catalyst sample to the electrode. After drying, the sample was tested. As a control, a commercial 20 wt.% Pt / C catalyst was selected for the ORR test and coated onto the carbon cloth for testing. A commercial 20 wt.% Pt / C catalyst was selected for the MOR test, and the preparation method was the same as the above sample. Electrochemical performance testing: A standard three-electrode electrochemical testing system was used during the testing process. The counter electrode was a stone-ground rod electrode, the reference electrode was a saturated calomel electrode (SCE), and the working electrode prepared above was used. The test solution was a 0.1 M H2SO4 solution (pH = 0). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg₂Cl₂) + 0.2415 + 0.059pH. The working electrode was operated at 10 mV / s prior to linear sweep voltammetry (LSV) testing. -1 The scan rate was activated by cyclic voltammetry (CV) for 50 cycles. All electrochemical tests were performed at room temperature.
[0069] The LSV curves of the ORR of P-Pt@CC samples and commercial 20 wt.% Pt / C catalyst in 1 M H2SO4 solution saturated with O2 were tested using a rotating disk electrode (RDE) at 1600 rpm. The results are as follows: Figure 2 As shown, the P-Pt@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.871 V vs. RHE and a half-wave potential of 0.605 V vs. RHE. This is lower than that of the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0070] The MOR catalytic activity was tested using a rotating disk electrode (RDE) on P-Pt@CC samples in a saturated N2 solution of 0.5 M H2SO4 + 0.5 M CH3OH. Figure 3 The CV curve of the MOR catalytic performance of the P-Pt@CC sample is shown, with a mass activity of 0.64 Amg. -1 PtIt is lower than the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0071] Comparative Example 2
[0072] (I) Synthesis of vertically oriented carbon nanotubes:
[0073] Cut a 3*4cm piece 2 Raw carbon cloth is placed in a tube furnace and heated at 5°C for 5 minutes under an inert atmosphere. -1 After the heating rate reaches 850℃, hold for 30 minutes to remove the polymer film on the carbon cloth surface. Take a 100mL beaker and a 20mL graduated cylinder. First, use the graduated cylinder to measure 18mL of toluene and transfer it into the beaker. Use a pipette to draw the same amount of tetraethyl orthosilicate and silicon tetrachloride and transfer them into the beaker. Sonicate in an ultrasonic cleaner for 30 minutes to prepare the precursor solution. Transfer the carbon cloth material after the first heat treatment into the beaker and soak it in the precursor solution for 1 hour. Remove it and dry the surface of the carbon cloth material with steam to load a thin layer of silica on the surface of the carbon cloth. Pyrolysis process: Transfer the material obtained from the hydrolysis process into a high-temperature tube furnace and introduce an inert gas (Ar). 2) The gas flow rate was set to 200 sccm, and the heating rate of the tube furnace was set to 5℃ / min. The temperature was first maintained at 200℃ for 60 min, and then at 850℃ for 60 min. A thin layer of silica was loaded onto the carbon cloth surface after hydrolysis and pyrolysis treatment. Carbon nanotubes were grown in situ on the carbon cloth surface using chemical vapor deposition. First, a carbon source solution was prepared. A 100 mL beaker and a 20 mL graduated cylinder were used. 600 mg of ferrocene (catalyst for carbon nanotube growth) was weighed and transferred into the beaker. Then, 9.8 mL of anhydrous ethanol and xylene (49%) were measured using the graduated cylinder. Finally, 400 μL of ethylenediamine (2%) was drawn using a pipette. The solution was stirred with a glass rod for 30 min, then ultrasonically stirred for 1 h in an ultrasonic cleaner. The prepared solution was transferred into a 20 mL syringe. The surface-treated carbon cloth material obtained in the second step was placed in a high-temperature tube furnace, and an inert gas (Ar2 or N2) was introduced. 2) When the temperature reaches 850℃, a prepared carbon source solution is simultaneously introduced using a micro-injection pump, ultimately yielding VACNTs@CC hybrid materials.
[0074] (II) Material Synthesis of Vertically Oriented Carbon Nanotubes Loaded with Platinum Precursors
[0075] The vertically oriented carbon nanotubes from step (I) were immersed in 0.1 mol / L chloroplatinic acid for 12 h, then removed and dried to obtain vertically oriented carbon nanotubes containing platinum precursors.
[0076] (III) Synthesis of materials with platinum metal supported on vertically oriented carbon nanotubes
[0077] The above-mentioned platinum ion-containing vertically oriented carbon nanotube composite material was placed in a ceramic boat, which was then placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus. Argon and hydrogen gas were introduced for plasma reduction. The temperature inside the tube was 500℃, the pressure inside the tube was 20Pa, the discharge power was 100W, and the discharge time was 60min. The resulting platinum metal catalyst supported on the surface of the carbon cloth was denoted as P-Pt@VACNTs@CC.
[0078] Bifunctional catalytic performance evaluation:
[0079] The electrocatalytic performance of the prepared direct methanol fuel cell catalyst samples was tested using an electrochemical workstation (CHI760E) in a three-electrode setup.
[0080] Preparation of working electrodes for ORR and MOR performance testing: Before using the rotating disk electrode (RDE), the glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder, then repeatedly rinsed with deionized water, ultrasonically dried for several seconds, and dried at room temperature for later use. A 4 mm diameter hole was punched in the prepared carbon cloth, and 5 wt.% Nafion was used as a binder to firmly adhere the direct methanol fuel cell catalyst sample to the electrode. After drying, the sample was tested. As a control, a commercial 20 wt.% Pt / C catalyst was selected for the ORR test and coated onto the carbon cloth for testing. A commercial 20 wt.% Pt / C catalyst was selected for the MOR test, and the preparation method was the same as the above sample. Electrochemical performance testing: A standard three-electrode electrochemical testing system was used during the testing process. The counter electrode was a stone-ground rod electrode, the reference electrode was a saturated calomel electrode (SCE), and the working electrode prepared above was used. The test solution was a 0.1 M H2SO4 solution (pH = 0). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg₂Cl₂) + 0.2415 + 0.059pH. The working electrode was operated at 10 mV / s prior to linear sweep voltammetry (LSV) testing. -1 The scan rate was activated by cyclic voltammetry (CV) for 50 cycles. All electrochemical tests were performed at room temperature.
[0081] The LSV curves of the ORR of P-Pt@VACNTs@CC samples and commercial 20 wt.% Pt / C catalyst in 1 M H2SO4 solution saturated with O2 were tested using a rotating disk electrode (RDE) at 1600 rpm. The results are as follows: Figure 2As shown, the P-Pt@VACNTs@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.866 V vs. RHE and a half-wave potential of 0.622 V vs. RHE. This is lower than that of the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0082] The MOR catalytic activity was tested using a rotating disk electrode (RDE) on P-Pt@VACNTs@CC samples in a 0.5M H₂SO₄ + 0.5M CH₃OH solution saturated with N₂. Figure 3 The CV curves of the MOR catalytic performance of the P-Pt@VACNTs@CC sample are shown, with a mass activity of 1.02 A mg. -1 Pt It is lower than the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0083] Comparative Example 3
[0084] (I) Synthesis of carbon cloth supported by iron-cobalt-nickel-copper hydroxide
[0085] Cut a 3*4cm piece 2 Raw carbon cloth is placed in a tube furnace and heated at 5°C for 5 minutes under an inert atmosphere. -1 After the heating rate reached 850℃, it was kept at that temperature for 30 min to remove the polymer film on the surface of the carbon cloth. 0.2 mmol FeCl3·3H2O, 0.2 mmol Co(NO3)2·6H2O, 0.2 mmol Ni(NO3)2·6H2O, 0.2 mmol Cu(NO3)2·3H2O, 3.6 mmol urea and 1.5 mmol ammonium fluoride were dissolved in 40 ml of deionized water and stirred thoroughly until dissolved. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and then the carbon cloth was placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 120℃ for 6 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 12 h to obtain iron cobalt nickel copper hydroxide@carbon cloth, denoted as FeCoNiCuLDH@CC.
[0086] (II) Loading of platinum precursor
[0087] The iron cobalt nickel copper hydroxide@carbon cloth was immersed in chloroplatinic acid to load a platinum precursor; the iron cobalt nickel copper hydroxide@carbon cloth obtained in step (I) was immersed in chloroplatinic acid with a concentration of 0.1 mol / L for 12 h, and then dried to obtain iron cobalt nickel copper hydroxide@carbon cloth containing a platinum precursor.
[0088] (III) Synthesis of Platinum Iron Cobalt Nickel Copper@Carbon Cloth
[0089] Platinum-loaded iron-cobalt-nickel-copper hydroxide@carbon cloth was placed in a ceramic boat, which was then placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus. Argon and hydrogen gas were introduced for plasma reduction. The tube was kept at a temperature of 500°C, a pressure of 20 Pa, a discharge power of 100 W, and a discharge time of 60 min. The resulting direct methanol fuel cell catalyst was designated as P-PtFeCoNiCu@CC.
[0090] Bifunctional catalytic performance evaluation:
[0091] The electrocatalytic performance of the prepared direct methanol fuel cell catalyst samples was tested using an electrochemical workstation (CHI760E) in a three-electrode setup.
[0092] Preparation of working electrodes for ORR and MOR performance testing: Before using the rotating disk electrode (RDE), the glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder, then repeatedly rinsed with deionized water, ultrasonically dried for several seconds, and dried at room temperature for later use. A 4 mm diameter hole was punched in the prepared carbon cloth, and 5 wt.% Nafion was used as a binder to firmly adhere the direct methanol fuel cell catalyst sample to the electrode. After drying, the sample was tested. As a control, a commercial 20 wt.% Pt / C catalyst was selected for the ORR test and coated onto the carbon cloth for testing. A commercial 20 wt.% Pt / C catalyst was selected for the MOR test, and the preparation method was the same as the above sample. Electrochemical performance testing: A standard three-electrode electrochemical testing system was used during the testing process. The counter electrode was a stone-ground rod electrode, the reference electrode was a saturated calomel electrode (SCE), and the working electrode prepared above was used. The test solution was a 0.1 M H2SO4 solution (pH = 0). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg₂Cl₂) + 0.2415 + 0.059pH. The working electrode was operated at 10 mV / s prior to linear sweep voltammetry (LSV) testing. -1 The scan rate was activated by cyclic voltammetry (CV) for 50 cycles. All electrochemical tests were performed at room temperature.
[0093] The LSV curves of the ORR of P-PtFeCoNiCu@CC sample and commercial 20wt.% Pt / C catalyst in 1M H2SO4 solution saturated with O2 were tested using a rotating disk electrode (RDE) at 1600 rpm. The results are as follows: Figure 2 As shown, the P-PtFeCoNiCu@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.864 V vs. RHE and a half-wave potential of 0.743 V vs. RHE. This is lower than that of the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0094] The MOR catalytic activity was tested using a rotating disk electrode (RDE) on a P-PtFeCoNiCu@CC sample in a 0.5 M H₂SO₄ + 0.5 M CH₃OH solution saturated with N₂. Figure 3 The CV curves of the MOR catalytic performance of the P-PtFeCoNiCu@CC sample are shown, with a mass activity of 1.32 A mg. -1 Pt It is lower than the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0095] Comparative Example 4
[0096] (I) Synthesis of vertically oriented carbon nanotubes:
[0097] Cut a 3*4cm piece 2 Raw carbon cloth is placed in a tube furnace and heated at 5°C for 5 minutes under an inert atmosphere. -1 After the heating rate reaches 850℃, hold for 30 minutes to remove the polymer film on the carbon cloth surface. Take a 100mL beaker and a 20mL graduated cylinder. First, use the graduated cylinder to measure 18mL of toluene and transfer it into the beaker. Use a pipette to draw the same amount of tetraethyl orthosilicate and silicon tetrachloride and transfer them into the beaker. Sonicate in an ultrasonic cleaner for 30 minutes to prepare the precursor solution. Transfer the carbon cloth material after the first heat treatment into the beaker and soak it in the precursor solution for 1 hour. Remove it and dry the surface of the carbon cloth material with steam to load a thin layer of silica on the surface of the carbon cloth. Pyrolysis process: Transfer the material obtained from the hydrolysis process into a high-temperature tube furnace and introduce an inert gas (Ar). 2) The gas flow rate was set to 200 sccm, and the heating rate of the tube furnace was set to 5℃ / min. The temperature was first maintained at 200℃ for 60 min, and then at 850℃ for 60 min. A thin layer of silica was loaded onto the carbon cloth surface after hydrolysis and pyrolysis treatment. Carbon nanotubes were grown in situ on the carbon cloth surface using chemical vapor deposition. First, a carbon source solution was prepared. A 100 mL beaker and a 20 mL graduated cylinder were used. 600 mg of ferrocene (catalyst for carbon nanotube growth) was weighed and transferred into the beaker. Then, 9.8 mL of anhydrous ethanol and xylene (49%) were measured using the graduated cylinder. Finally, 400 μL of ethylenediamine (2%) was drawn using a pipette. The solution was stirred with a glass rod for 30 min, then ultrasonically stirred for 1 h in an ultrasonic cleaner. The prepared solution was transferred into a 20 mL syringe. The surface-treated carbon cloth material obtained in the second step was placed in a high-temperature tube furnace, and an inert gas (Ar2 or N2) was introduced. 2) When the temperature reaches 850℃, a prepared carbon source solution is simultaneously introduced using a micro-injection pump, ultimately yielding VACNTs@CC hybrid materials.
[0098] (II) Synthesis of iron-cobalt-nickel-copper hydroxide:
[0099] 0.2 mmol FeCl3·3H2O, 0.2 mmol Co(NO3)2·6H2O, 0.2 mmol Ni(NO3)2·6H2O, 0.2 mmol Cu(NO3)2·3H2O, 3.6 mmol urea, and 1.5 mmol ammonium fluoride were dissolved in 40 ml of deionized water and stirred thoroughly until dissolved. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and vertically oriented carbon nanotubes were placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 120 °C for 6 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 12 h to obtain iron-cobalt-nickel-copper hydroxide@oriented carbon nanotubes, denoted as FeCoNiCu LDH@VACNTs@CC.
[0100] (III) Loading of platinum precursor
[0101] The iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes were immersed in chloroplatinic acid to load a platinum precursor; the iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes obtained in step (II) were immersed in chloroplatinic acid with a concentration of 0.1 mol / L for 12 h, removed and dried to obtain iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes@carbon cloth containing a platinum precursor.
[0102] (iv) Synthesis of Platinum Iron Cobalt Nickel Copper@Vertically Oriented Carbon Nanotubes@Carbon Cloth
[0103] Platinum-loaded iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes were placed in a ceramic boat, which was then placed in a chemical vapor deposition apparatus. Argon and hydrogen gas were introduced for tubular furnace annealing and reduction. The temperature inside the tube was 500℃ and the pressure inside the tube was 20Pa. The resulting direct methanol fuel cell catalyst is denoted as T-PtFeCoNiCu@VACNTs@CC.
[0104] Platinum-loaded iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes were placed in a ceramic boat, which was then placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus. Argon and hydrogen gas were introduced for plasma reduction. The temperature inside the tube was 500℃, the pressure inside the tube was 20Pa, the discharge power was 100W, and the discharge time was 60min. The resulting direct methanol fuel cell catalyst is denoted as P-PtFeCoNiCu@VACNTs@CC.
[0105] Bifunctional catalytic performance evaluation:
[0106] The electrocatalytic performance of the prepared direct methanol fuel cell catalyst samples was tested using an electrochemical workstation (CHI760E) in a three-electrode setup.
[0107] Preparation of working electrodes for ORR and MOR performance testing: Before using the rotating disk electrode (RDE), the glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder, then repeatedly rinsed with deionized water, ultrasonically dried for several seconds, and dried at room temperature for later use. A 4 mm diameter hole was punched in the prepared carbon cloth, and 5 wt.% Nafion was used as a binder to firmly adhere the direct methanol fuel cell catalyst sample to the electrode. After drying, the sample was tested. As a control, a commercial 20 wt.% Pt / C catalyst was selected for the ORR test and coated onto the carbon cloth for testing. A commercial 20 wt.% Pt / C catalyst was selected for the MOR test, and the preparation method was the same as the above sample. Electrochemical performance testing: A standard three-electrode electrochemical testing system was used during the testing process. The counter electrode was a stone-ground rod electrode, the reference electrode was a saturated calomel electrode (SCE), and the working electrode prepared above was used. The test solution was a 0.1 M H2SO4 solution (pH = 0). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg₂Cl₂) + 0.2415 + 0.059pH. The working electrode was operated at 10 mV / s prior to linear sweep voltammetry (LSV) testing. -1 The scan rate was activated by cyclic voltammetry (CV) for 50 cycles. All electrochemical tests were performed at room temperature.
[0108] The LSV curves of the ORR of the T-PtFeCoNiCu@VACNTs@CC sample and the commercial 20wt.% Pt / C catalyst in a 1M H2SO4 solution saturated with O2 were tested using a rotating disk electrode (RDE) at 1600 rpm. The results are as follows: Figure 2 As shown, the T-PtFeCoNiCu@VACNTs@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.844 V vs. RHE and a half-wave potential of 0.622 V vs. RHE. This is lower than that of the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0109] The MOR catalytic activity was tested using a rotating disk electrode (RDE) on a T-PtFeCoNiCu@VACNTs@CC sample in a saturated N2 solution of 0.5 M H2SO4 + 0.5 M CH3OH. Figure 3 The CV curves of the MOR catalytic performance of the T-PtFeCoNiCu@VACNTs@CC sample are shown, with a mass activity of 1.38 A mg. -1 Pt It is lower than the P-PtFeCoNiCu@VACNTs@CC catalyst under the same conditions.
[0110] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A catalyst for a direct methanol fuel cell, characterized in that, Its structural unit consists of vertically oriented carbon nanotubes as a conductive network, with a platinum-iron-cobalt-nickel-copper high-entropy alloy loaded on this conductive network.
2. A method for preparing a direct methanol fuel cell catalyst as described in claim 1, characterized in that, Specifically, it includes the following steps: S1 was used to prepare vertically oriented carbon nanotubes; S1.1 The carbon cloth is subjected to hydrolysis and pyrolysis treatment, and a thin layer of silica is loaded on the surface of the carbon cloth; S1.2 The carbon cloth treated in step S1.1 is used to grow carbon nanotubes in situ on the surface of the carbon cloth material by chemical vapor deposition. In a high-temperature tube furnace under an inert atmosphere at a temperature of 800-900℃, a carbon source solution is introduced through a micro-injection pump to obtain a hybrid material, denoted as VACNTs@CC. S2 hydrothermal reaction supported iron-cobalt-nickel-copper nanosheets to obtain iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes, denoted as FeCoNiCu LDH / VACNTs@CC; S3 immersed the obtained iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes in chloroplatinic acid solution to load platinum ions, denoted as PtFeCoNiCu@VACNTs@CC. In an argon-hydrogen atmosphere, S4 utilizes radio frequency plasma technology to perform plasma reduction treatment on iron-cobalt-nickel-copper hydroxide@vertically oriented nanotubes that have been soaked in chloroplatinic acid solution, thereby obtaining a direct methanol fuel cell catalyst, denoted as P-PtFeCoNiCu@VACNTs@CC.
3. The method for preparing the direct methanol fuel cell catalyst according to claim 2, characterized in that, Before the carbon cloth undergoes hydrolysis and pyrolysis treatment, the carbon cloth is placed in an inert atmosphere and heated at 4-6℃ for min. -1 After the heating rate reaches 800-900℃, hold the temperature for 25-35 minutes to remove the polymer film on the surface of the carbon cloth.
4. The method for preparing the direct methanol fuel cell catalyst according to claim 2, characterized in that, The hydrolysis and pyrolysis treatment in step S1.1 is as follows: First, measure toluene, then add the same amount of tetraethyl orthosilicate and silicon tetrachloride, and then sonicate for 25-35 minutes to obtain the precursor solution. Soak the carbon cloth in the precursor solution for 1 hour, take it out and dry it, keep it at 150-250℃ for 60 minutes, and then keep it at 800-900℃ for 55-65 minutes to load a thin layer of silicon dioxide on the surface of the carbon cloth.
5. The method for preparing a direct methanol fuel cell catalyst according to claim 2, characterized in that, The specific method for preparing the carbon source solution in step S1.2 is as follows: Weigh ferrocene, then measure anhydrous ethanol and xylene, and finally extract ethylenediamine. Stir evenly to obtain the carbon source solution, in which ferrocene is 600 mg, anhydrous ethanol is 9.8 ml, xylene is 9.8 ml and ethylenediamine is 0.4 ml.
6. The method for preparing a direct methanol fuel cell catalyst according to claim 2, characterized in that, The preparation process of step S2 includes: dissolving iron transition metal salt, cobalt transition metal salt, nickel transition metal salt, copper transition metal salt, urea and ammonium fluoride in deionized water, stirring thoroughly to dissolve, placing vertically oriented carbon nanotubes, reacting at 110-130℃ for 5-7 hours, after the reaction is completed, cooling and removing, rinsing with deionized water and ethanol, and drying for 6-24 hours.
7. The method for preparing a direct methanol fuel cell catalyst according to claim 6, characterized in that, The iron transition metal salt is one or more of FeSO4, FeCl3, FeCl2, and Fe(NH2SO3)3; the cobalt transition metal salt is one or more of Co(NO3)2·6H2O, CoCl2·6H2O, Co(CH3COO)2·4H2O, CoSO4·6H2O, and CoCl2; the nickel transition metal salt is NiC 10 H 14 One or more of O4, NiCl2·6H2O, Ni(NO3)2·6H2O, NiC4H6O4·4H2O, and NiCO3 are used, and the copper transition metal salt is one or more of CuCl2·2H2O, CuSO4·5H2O, Cu(CH3COO)2·H2O, and Cu(NO3)2·3H2O.
8. The method for preparing a direct methanol fuel cell catalyst according to claim 6, characterized in that, The molar ratio of FeCl3·3H2O:Co(NO3)2·6H2O:Ni(NO3)2·6H2O:Cu(NO3)2·3H2O is 1:1:1:
1.
9. The method for preparing a direct methanol fuel cell catalyst according to claim 2, characterized in that, In step S3, the concentration of the chloroplatinic acid solution is 0.1 mol / L chloroplatinic acid, and the soaking time is 10-14 h.
10. The method for preparing the direct methanol catalyst according to claim 2, characterized in that, Step S4 is as follows: Platinum-loaded iron-cobalt-nickel-copper hydroxide@vertically oriented carbon nanotubes are placed in a ceramic boat, the ceramic boat is placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus, argon and hydrogen are introduced, and plasma reduction is performed. The temperature inside the tube is 500℃, the pressure inside the tube is 20Pa, the discharge power is 100W, and the discharge time is 30-90min.