A methanol fuel cell catalyst and a method for preparing the same

Abstract

This invention discloses a methanol fuel cell catalyst and its preparation method. The catalyst's structural unit uses nitrogen-doped iron-based carbon nanotubes loaded with iron and cobalt single atoms as a conductive network, with platinum uniformly loaded onto this network. The preparation method includes the following steps: S1, preparing nitrogen-doped iron-based carbon nanotubes; S2, loading iron-cobalt hydroxide nanosheets via hydrothermal reaction to obtain iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes; S3, reducing the iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes in a reducing atmosphere using CVD to obtain iron-cobalt single atoms@nitrogen-doped iron-based carbon nanotubes; S4, loading platinum onto the iron-cobalt single atoms@nitrogen-doped iron-based carbon nanotubes under an inert atmosphere using magnetron sputtering to obtain platinum@iron-cobalt single atoms@nitrogen-doped iron-based carbon nanotubes, which serve as the methanol fuel cell catalyst, exhibiting high specific surface area, numerous active sites, excellent performance, low cost, and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of methanol fuel cell catalyst technology, and in particular relates to a methanol fuel cell catalyst and its preparation method. Background Technology

[0002] Direct methanol fuel cells (DMFCs) offer advantages such as low operating temperature, high power density, and convenient fuel storage, making them a viable alternative to expensive lithium-ion batteries in electronic devices. The principle of DMFCs is based on the electrochemical reactions of methanol and oxygen at the anode and cathode, respectively. Thermodynamic calculations have yielded a theoretical potential of 1.21 V for DMFCs at 25°C, and measurements have shown that methanol conversion efficiency in DMFCs reaches as high as 96.4%. However, the slow reaction kinetics of the methanol oxidation reaction (MOR) and the methanol cross-effect reduce the cell efficiency, resulting in an actual operating potential lower than the theoretical value. The principle of a fuel cell is to convert chemical energy into electrical energy through a sustainable process; its efficiency depends on the kinetics of the oxygen reduction reaction (ORR) at the cathode. Therefore, developing a kinetically fast and methanol-resistant electrocatalyst is of great significance.

[0003] Ordinary planar substrates cannot achieve efficient loading of Pt. In contrast, carbon-based catalysts have many advantages, such as high conductivity, tunable porous structure, good chemical stability, and low cost, and have been widely studied in the field of energy electrochemistry. However, carbon materials have a limited number of active sites, and the catalytic activity of a single site is insufficient. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned related technologies, this application provides a 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.

[0005] This application provides a methanol fuel cell catalyst, characterized in that its structural unit uses nitrogen-doped iron-based carbon nanotubes loaded with iron and cobalt single atoms as a conductive network, and metallic platinum is uniformly loaded on the conductive network.

[0006] This application also provides a method for preparing a methanol fuel cell catalyst, comprising the following steps: S1 was used to prepare nitrogen-doped iron-based carbon nanotubes, denoted as FeNCNTs / CC; S2 hydrothermal reaction supported iron cobalt hydroxide nanosheets to obtain iron cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes, denoted as CoFe LDH@FeNCNTs / CC; In a reducing atmosphere, iron cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes were reduced by CVD to obtain iron cobalt single atom@nitrogen-doped iron-based carbon nanotubes, denoted as CoFe(SA)@FeNCNTs / CC; In an inert atmosphere, platinum was loaded onto iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes by magnetron sputtering to obtain platinum@iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes, denoted as Pt@CoFe(SA)@FeNCNTs / CC, which is the catalyst for methanol fuel cells.

[0007] Preferably, the preparation process in step S1 is as follows: S1.1 Cut the carbon cloth and place it in ethanol and deionized water in sequence for ultrasonic cleaning; S1.2 The ultrasonically treated carbon cloth is placed in FeSO4 solution and soaked at 55-65℃ for 11-13 hours. The iron-coated carbon cloth is then removed and dried to obtain iron-coated carbon cloth. S1.3 The iron-coated carbon cloth is heated to 450-550℃ at a heating rate of 4-6℃ / min under an argon-ammonia atmosphere, held at this temperature for 25-35min, and then cooled. Melamine is placed on top of the nitrided iron-coated carbon cloth, and heated to 800-900℃ at a heating rate of 9-11℃ / min under an argon atmosphere, held at this temperature for 120min, and the reaction is completed. After cooling, the nitrogen-doped iron-based carbon nanotubes are removed.

[0008] Preferably, the concentration of FeSO4 solution in step S1.2 is 0.2 mol / L, and the amount of melamine added in step S1.3 is positively correlated with the carbon cloth area at 0.25 g / cm2.

[0009] Preferably, the preparation process of step S2 is as follows: nitrogen-doped iron-based carbon nanotubes are placed in a polar aprotic solvent solution of iron salt, cobalt salt and zinc salt, reacted at 160-180℃ for 9-11 hours, removed, washed and dried to obtain iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes.

[0010] Preferably, in step S2, the polar aprotic solvent solution of the iron salt, cobalt salt, and zinc salt is a formamide solution of ferrous chloride, cobalt chloride, and zinc chloride, wherein the concentration of Fe2+ is 0.015 mol / L, the concentration of Co2+ is 0.015 mol / L, and the concentration of Zn2+ is 0.07 mol / L.

[0011] Preferably, the preparation process of step S3 is as follows: iron cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes are placed together with melamine, and under an argon-hydrogen atmosphere, the temperature is raised to 850-950℃ at a heating rate of 4-6℃ / min, and held at this temperature for 2.5-3.5h. After the reaction is completed, the mixture is cooled to obtain iron cobalt single atom@nitrogen-doped iron-based carbon nanotubes.

[0012] Preferably, the magnetron sputtering conditions in step S4 are: under an argon atmosphere, a pressure of 3 Pa, direct current, a power of 75 W, and a sputtering time of 12 min.

[0013] Compared with the prior art, the present invention has the following advantages: The transition metal single atoms (iron-cobalt single atoms) supported in the preparation method provide excellent electrocatalytic performance. The secondary-grown carbon nanotubes provide a larger specific surface area, enabling the substrate to have more loading and catalytic sites and improving conductivity. Magnetron sputtering reduces the amount of precious metal platinum used, providing better catalytic performance, improving cycle stability and charge-discharge performance, and giving the methanol fuel cell catalyst excellent ORR and MOR electrocatalytic performance. The specific reasons are as follows: Nitrogen-doped iron-based carbon nanotubes possess excellent electrical conductivity. Nitrogen's electronegativity is far greater than carbon's, making the electrically neutral carbon material positively charged by nitrogen doping, thus facilitating the deposition of metal nanoparticles. Simultaneously, nitrogen-doped carbon materials can promote oxygen adsorption and the decomposition of intermediate peroxides. Nitrogen-containing functional groups increase the electron affinity with the matrix, enhancing the metal's ability to donate electrons and thereby improving catalyst activity. Nitrogen-doped iron-based carbon nanotubes have abundant porosity and iron-based active sites, enabling them to exhibit excellent electrocatalytic oxygen reduction performance. Furthermore, their high specific surface area and stable three-dimensional structure allow electrochemically active substances to easily adhere to the carbon nanotube surface, improving their catalytic performance. Carbon nanotubes integrate two transition metal single-atom phases into the same catalyst. Their high conductivity promotes electron transport, while their surface functional groups (such as defects and heteroatom doping) can anchor single atoms and modulate their electronic states, maximizing atomic utilization. Theoretically, each metal atom can serve as an active site, achieving near 100% atomic utilization. The unique electronic structure of single atoms (such as uncoordinated sites and charge transfer) can significantly enhance catalytic activity, exhibiting a significant quantum size effect.

[0014] Magnetron sputtering of Pt can precisely control the dispersion of Pt, forming a highly dispersed load, reducing the amount of precious metals used and lowering costs. At the same time, it combines with the intrinsic conductivity of NCNTs to greatly improve conductivity. Furthermore, it strengthens the metal-carrier interaction through direct bonding, optimizes the electronic structure, and enhances resistance to poisoning. Attached Figure Description

[0015] Figure 1 Microstructure of Pt@CoFe(SA)NCNTs@FeNCNTs / CC prepared in Example 1 under a scanning electron microscope (SEM); Figure 2Linear sweep voltammetry (LSV) plots of oxygen reduction reaction (ORR) for Example 1, Comparative Examples 1, 2, 3, 4, and a commercial catalyst. Figure 3 Linear sweep voltammetry (LSV) plots of methanol oxidation (MOR) in Example 1, Comparative Examples 1, 2, 3, 4, and a commercial catalyst. Detailed Implementation

[0016] 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.

[0017] The present invention will be further described in detail below with reference to specific embodiments.

[0018] A methanol fuel cell catalyst, the structural unit of which is a nitrogen-doped iron-based carbon nanotube with iron and cobalt single atoms loaded as a conductive network, and metallic platinum uniformly loaded on the conductive network, is prepared by means of the following steps: S1 Preparation of Nitrogen-Doped Iron-Based Carbon Nanotubes S1.1 Cut the carbon cloth and place it in ethanol and deionized water in sequence for ultrasonic cleaning; S1.2 The ultrasonically treated carbon cloth is placed in FeSO4 solution with a concentration of 0.2 mol / L and soaked at 55-65℃ for 11-13 hours. The iron-coated carbon cloth is then removed and dried to obtain iron-coated carbon cloth. S1.3 The iron-coated carbon cloth is heated to 450-550℃ at a heating rate of 4-6℃ / min under an argon-ammonia atmosphere, held for 25-35min, and then cooled. Melamine is placed on top of the nitrided iron-coated carbon cloth, with the amount of melamine added being positively correlated with the carbon cloth area at 0.25g / cm2. Under an argon atmosphere, the temperature is increased to 800-900℃ at a heating rate of 9-11℃ / min, held for 120min, and the reaction is completed. After cooling, the nitrogen-doped iron-based carbon nanotubes are obtained, denoted as FeNCNTs / CC. S2 hydrothermal reactive supported iron-cobalt hydroxide nanosheets Nitrogen-doped iron-based carbon nanotubes were placed in a formamide solution of ferrous chloride, cobalt chloride, and zinc chloride, and reacted at 160-180℃ for 9-11 hours. After removal, washing, and drying, iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes were obtained, denoted as CoFeLDH@FeNCNTs / CC, with Fe2+ concentration of 0.015 mol / L, Co2+ concentration of 0.015 mol / L, and Zn2+ concentration of 0.07 mol / L. S3 placed cobalt iron hydroxide@nitrogen-doped iron-based carbon nanotubes together with melamine, and heated to 850-950℃ at a heating rate of 4-6℃ / min under an argon-hydrogen atmosphere. After holding at this temperature for 2.5-3.5h, the reaction was completed and the mixture was cooled to obtain cobalt iron single atom@nitrogen-doped iron-based carbon nanotubes, denoted as CoFe(SA)@FeNCNTs / CC. In an inert atmosphere, platinum was loaded onto iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes by magnetron sputtering. The magnetron sputtering conditions were: argon atmosphere, pressure of 3 Pa, DC power of 75 W, sputtering time of 12 min, to obtain platinum@iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes, denoted as Pt@CoFe(SA)@FeNCNTs / CC, which is the catalyst for methanol fuel cells.

[0019] Example 1 A method for preparing a methanol fuel cell catalyst includes the following steps: (a) Preparation of nitrogen-doped iron-based carbon nanotubes: Cut a 3*4cm² piece of carbon cloth and place it in ethanol and deionized water respectively, sonicating for 15 min each time. Weigh 3.892g FeSO₄•7H₂O, dissolve it in 70mL of deionized water, stir well, and then place the sonicated carbon cloth in it. Soak it at 60℃ for 12 h. After that, take out the iron-coated carbon cloth and dry it in an oven for 12 h. Place the dried iron-coated carbon cloth on a ceramic boat and put it in a tube furnace. Introduce argon and ammonia gas, and heat it to 500℃ at a heating rate of 5℃ / min. Hold it at this temperature for 30 min for nitriding. After cooling, take out the ceramic boat. Weigh 3g of melamine and place it in the ceramic boat above the iron-coated carbon cloth for nitriding. Place it in a tube furnace, introduce argon gas, and heat it to 850℃ at a heating rate of 10℃ / min for further annealing. Hold it at this temperature for 120 min. After the reaction is complete, cool it and take out the nitrogen-doped iron-based carbon nanotubes, denoted as FeNCNTs / CC.

[0020] (ii) Hydrothermal reaction loading of iron-cobalt hydroxide nanosheets to obtain CoFeLDH@FeNCNTs / CC: 0.15 g of ferrous chloride tetrahydrate, 0.18 g of cobalt chloride hexahydrate, and 0.48 g of zinc chloride were dissolved in 50 ml of formamide and stirred thoroughly. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and nitrogen-doped iron-based carbon nanotubes were placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 170 °C for 10 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 10 h to obtain cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes, denoted as CoFeLDH@FeNCNTs / CC.

[0021] (III) CoFe LDH@FeNCNTs / CC was reduced in a reducing atmosphere using CVD to obtain CoFe(SA)@FeNCNTs / CC: The dried iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes were placed on a ceramic boat, and 4g of melamine was weighed and placed together in a corundum tube furnace. Argon and hydrogen gas were introduced, and the temperature was raised to 900℃ at a rate of 5℃ / min for further annealing. After holding at this temperature for 180min, the reaction was completed. After cooling, the nanotubes were removed to obtain iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes, denoted as CoFe(SA)@FeNCNTs / CC.

[0022] (iv) Pt@CoFe(SA)NCNTs@FeNCNTs / CC were obtained by magnetron sputtering under an inert atmosphere: Iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes were cut into 1*4cm2 pieces and placed in a magnetron sputtering instrument. Under an argon atmosphere, at 3Pa, DC, and 75W, metallic platinum was sputtered for 12min to obtain the methanol fuel cell catalyst, denoted as Pt@CoFe(SA)NCNTs@FeNCNTs / CC.

[0023] Catalytic performance evaluation: The electrocatalytic performance of the prepared methanol fuel cell catalyst sample was tested using an electrochemical workstation (CHI760E) in a three-electrode configuration.

[0024] Preparation of working electrodes for ORR and MOR performance testing: Before using the rotating disk electrode (RDE), the glassy carbon electrode (GCE, d=4.0mm) 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 4mm diameter hole was punched in the prepared carbon cloth, and 5wt.% Nafion was used as a binder to firmly adhere the zinc-air battery bifunctional catalyst sample to the electrode. After drying, the sample was tested. As a control experiment, a commercial 20wt.% Pt / C catalyst was selected for ORR and MOR testing, coated onto the carbon cloth. The preparation method was the same as for the samples described above. Electrochemical performance testing: A standard three-electrode electrochemical testing system was used, with a platinum sheet electrode as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and the working electrode prepared above. The test solution was a 0.5M H2SO4 solution. 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 activated for 50 cycles by cyclic voltammetry (CV) at a scan rate of 10 m / Vs prior to linear sweep voltammetry (LSV) testing. All electrochemical measurements were performed at room temperature.

[0025] The ORR (Orientation-Reduction) LSV (Low-Speed ​​Value) curves of the Pt@CoFe(SA)NCNTs@FeNCNTs / CC sample and the commercial 20wt.% Pt / C catalyst in 0.5M H2SO4 solution saturated with O2 and rotated at 1600 rpm were tested using a rotating disk electrode (RDE). The results are as follows: Figure 2 As shown.

[0026] The Pt@CoFe(SA)NCNTs@FeNCNTs / CC sample exhibited high ORR electrocatalytic activity, with a half-wave potential of 0.775 V vs. RHE and an onset potential of 0.862 V vs. RHE, which is higher than that of commercial Pt / C catalysts. This indicates that the Pt@CoFe(SA)NCNTs@FeNCNTs / CC sample has fast reaction kinetics in the ORR electrocatalysis process.

[0027] The catalytic activity of MOR was also tested using RED (Reactive Chromatography). The CV (Chemical Vibration Calculation) curve for MOR was measured in a mixed solution of 0.5 M H₂SO₄ and 0.5 M CH₃OH saturated with N₂. A commercial 20 wt.% Pt / C catalyst was tested under the same conditions, and the results are as follows: Figure 3 As shown, the forward oxidation peak (If) and backward scanning peak (Ib) of the Pt@CoFe(SA)NCNTs@FeNCNTs / CC sample are 0.97 A / mgPt and 1.00 A / mgPt, respectively, with a ratio of If / Ib=0.97, both higher than those of commercial catalysts (If=0.57 A / mgPt, Ib=0.63 A / mgPt, If / Ib=0.90).

[0028] This indicates that the Pt@CoFe(SA)NCNTs@FeNCNTs / CC sample exhibits excellent MOR electrocatalytic performance and durability.

[0029] Comparative Example 1: The preparation method of a catalyst (Pt@Co(SA)NCNTs@FeNCNTs / CC) with cobalt metal single atoms supported on the surface of nitrogen-doped iron-based carbon nanotubes and sputtered with Pt includes the following steps: (a) Preparation of nitrogen-doped iron-based carbon nanotubes: Cut a 3*4cm² piece of carbon cloth and place it in ethanol and deionized water respectively, sonicating for 15 min each time. Weigh 3.892g FeSO₄•7H₂O, dissolve it in 70mL of deionized water, stir well, and then place the sonicated carbon cloth in it. Soak it at 60℃ for 12 h. After that, take out the iron-doped carbon cloth and dry it in an oven for 12 h. Place the dried iron-doped carbon cloth on a ceramic boat and put it in a tube furnace. Introduce argon and ammonia gas, and heat it to 500℃ at a heating rate of 5℃ / min. Hold it at this temperature for 30 min for nitriding. After cooling, take out the ceramic boat. Weigh 3g melamine and place it in the ceramic boat above the iron-doped carbon cloth for nitriding. Place it in a tube furnace, introduce argon gas, and heat it to 850℃ at a heating rate of 10℃ / min for further annealing. Hold it at this temperature for 120 min. After the reaction is complete, cool it and take out the nitrogen-doped iron-based heterogeneous carbon nanotubes, denoted as FeNCNTs / CC.

[0030] (ii) Hydrothermal reaction loading of iron-cobalt hydroxide nanosheets to obtain CoLDH@FeNCNTs / CC: 0.18 g of cobalt chloride hexahydrate and 0.48 g of zinc chloride were dissolved in 50 ml of formamide and stirred thoroughly. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and nitrogen-doped iron-based carbon nanotubes were placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 170 °C for 10 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 10 h to obtain CoLDH@FeNCNTs / CC.

[0031] (III) CoLDH@FeNCNTs / CC was reduced in a reducing atmosphere using CVD to obtain Co(SA)NCNTs@FeNCNTs / CC: The dried cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes were placed on a ceramic boat, and 4g of melamine was weighed and placed together in a corundum tube furnace. Argon and hydrogen gas were introduced, and the temperature was raised to 900℃ at a rate of 5℃ / min for further annealing. After holding at this temperature for 180min, the reaction was completed. After cooling, the iron-cobalt single-atom@carbon nanotube@nitrogen-doped iron-based carbon nanotubes were taken out and labeled as Co(SA)NCNTs@FeNCNTs / CC.

[0032] Pt@Co(SA)NCNTs@FeNCNTs / CC was obtained by magnetron sputtering under an inert atmosphere. A 1*4 cm² piece of Co(SA)NCNTs@FeNCNTs / CC was cut and placed in a magnetron sputtering instrument. Platinum metal was sputtered for 12 min under an argon atmosphere, at 3 Pa, DC, and 75 W. The resulting methanol fuel cell catalyst was denoted as Pt@Co(SA)NCNTs@FeNCNTs / CC.

[0033] Catalytic performance evaluation: The LSV curves of the ORR of Pt@Co(SA)NCNTs@FeNCNTs / CC sample and commercial 20wt.% Pt / C catalyst in 0.5M H2SO4 solution saturated with O2 were tested using a rotating disk electrode (RDE) at 1600 rpm. Figure 2 As shown.

[0034] The Pt@Co(SA)NCNTs@FeNCNTs / CC sample exhibited ORR electrocatalytic performance of 0.731 V vs. RHE at half-wave potential and 0.835 V vs. RHE at onset potential.

[0035] This indicates that the Pt@Co(SA)NCNTs@FeNCNTs / CC sample exhibits relatively fast reaction kinetics during the ORR electrocatalysis process.

[0036] The catalytic activity of MOR was also tested using RED (Reactive Chromatography). The CV (Chemical Activity Regulator) curve for MOR was measured in a mixed solution of 0.5 M H₂SO₄ and 0.5 M CH₃OH saturated with N₂. A commercial 20 wt.% Pt / C catalyst was tested under the same conditions, and the results are as follows: Figure 3 As shown, the forward oxidation peak (If) and backward scanning peak (Ib) of the Pt@CoNCNTs@FeNCNTs / CC sample are 0.37 A / mgPt and 0.49 A / mgPt, respectively, and the ratio of the two peaks is If / Ib=0.76.

[0037] Comparative Example 2: The preparation method of a catalyst (Pt@Fe(SA)NCNTs@FeNCNTs / CC) with iron metal single atoms supported on the surface of nitrogen-doped iron-based carbon nanotubes and sputtered Pt includes the following steps: (a) Preparation of nitrogen-doped iron-based carbon nanotubes: Cut a 3*4cm² piece of carbon cloth and place it in ethanol and deionized water respectively, sonicating for 15 min each time. Weigh 3.892g FeSO₄•7H₂O, dissolve it in 70mL of deionized water, stir well, and then place the sonicated carbon cloth in it. Soak it at 60℃ for 12 h. After that, take out the iron-coated carbon cloth and dry it in an oven for 12 h. Place the dried iron-coated carbon cloth on a ceramic boat and put it in a tube furnace. Introduce argon and ammonia gas, and heat it to 500℃ at a heating rate of 5℃ / min. Hold it at this temperature for 30 min for nitriding. After cooling, take out the ceramic boat. Weigh 3g of melamine and place it in the ceramic boat above the iron-coated carbon cloth for nitriding. Put it in a tube furnace, introduce argon gas, and heat it to 850℃ at a heating rate of 10℃ / min for further annealing. Hold it at this temperature for 120 min. After the reaction is complete, cool it and take out the nitrogen-doped iron-based carbon nanotubes, denoted as FeNCNTs / CC.

[0038] (ii) Hydrothermal reaction loading of iron hydroxide nanosheets to obtain Fe LDH@FeNCNTs / CC: 0.15 g of ferric chloride tetrahydrate and 0.48 g of zinc chloride were dissolved in 50 ml of formamide and stirred thoroughly. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and nitrogen-doped iron-based carbon nanotubes were placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 170 °C for 10 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 10 h to obtain FeLDH@FeNCNTs / CC.

[0039] (III) FeLDH@FeNCNTs / CC was reduced in a reducing atmosphere using CVD to obtain Fe(SA)NCNTs@FeNCNTs / CC: The dried FeLDH@FeNCNTs / CC was placed on a ceramic boat, and 4g of melamine was weighed and placed together in a corundum tube furnace. Argon and hydrogen gas were introduced, and the temperature was raised to 900℃ at a rate of 5℃ / min for further annealing. After holding at this temperature for 180min, the reaction was completed. After cooling, the sample was taken out and recorded as Fe(SA)NCNTs@FeNCNTs / CC.

[0040] (iv) Obtaining Pt@Fe(SA)NCNTs@FeNCNTs / CC by magnetron sputtering under an inert atmosphere: A 1*4 cm² piece of Fe(SA)NCNTs@FeNCNTs / CC was cut and placed in a magnetron sputtering instrument. Platinum metal was sputtered for 12 min under an argon atmosphere, at 3 Pa, DC, and 75 W. The resulting methanol fuel cell catalyst is denoted as Pt@Fe(SA)NCNTs@FeNCNTs / CC.

[0041] Catalytic performance evaluation: The LSV curves of the ORR of Pt@Fe(SA)NCNTs@FeNCNTs / CC sample and commercial 20 wt.% Pt / C catalyst in 0.5 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.

[0042] The Pt@Fe(SA)NCNTs@FeNCNTs / CC sample exhibited ORR electrocatalytic performance of 0.701 V vs. RHE at half-wave potential and 0.812 V vs. RHE at onset potential.

[0043] The catalytic activity of MOR was also tested using RED (Reactive Chromatography). The CV (Chemical Activity Regulator) curve for MOR was measured in a mixed solution of 0.5 M H₂SO₄ and 0.5 M CH₃OH saturated with N₂. A commercial 20 wt.% Pt / C catalyst was tested under the same conditions, and the results are as follows: Figure 3 As shown, the forward oxidation peak (If) and backward scanning peak (Ib) of the Pt@FeNCNTs@FeNCNTs / CC sample are 0.28 A / mgPt and 0.37 A / mgPt, respectively, and the ratio of the two peaks is If / Ib=0.76.

[0044] Comparative Example 3: The preparation method of the iron-cobalt alloy supported catalyst (Pt@CoFe@FeNCNTs / CC) sputtered on the surface of nitrogen-doped iron-based carbon nanotubes includes the following steps: (a) Preparation of nitrogen-doped iron-based carbon nanotubes; Cut a 3*4cm² piece of carbon cloth and place it in ethanol and deionized water respectively, sonicating for 15 min each time. Weigh 3.892g FeSO₄•7H₂O, dissolve it in 70mL of deionized water, stir well, and then place the sonicated carbon cloth in it. Soak it at 60℃ for 12 h. After that, take out the iron-coated carbon cloth and dry it in an oven for 12 h. Place the dried iron-coated carbon cloth on a ceramic boat and put it in a tube furnace. Introduce argon and ammonia gas, and heat it to 500℃ at a heating rate of 5℃ / min. Hold it at this temperature for 30 min for nitriding. After cooling, take out the ceramic boat. Weigh 3g of melamine and place it in the ceramic boat above the iron-coated carbon cloth for nitriding. Place it in a tube furnace, introduce argon gas, and heat it to 850℃ at a heating rate of 10℃ / min for further annealing. Hold it at this temperature for 120 min. After the reaction is complete, cool it and take out the nitrogen-doped iron-based carbon nanotubes, denoted as FeNCNTs / CC.

[0045] (ii) Hydrothermal reaction loading of iron-cobalt hydroxide nanosheets to obtain CoFeLDH@FeNCNTs / CC: 0.15 g ferric chloride tetrahydrate, 0.18 g cobalt chloride hexahydrate, and 0.48 g zinc chloride were dissolved in 50 ml formamide and stirred thoroughly. The solution was poured into a polytetrafluoroethylene (PTFE) liner, and nitrogen-doped iron-based carbon nanotubes were placed inside. The PTFE liner was then placed in a high-pressure reactor and reacted at 170 °C for 10 h. After the reaction was completed and cooled, the solution was removed, rinsed with deionized water and ethanol, and dried in an oven for 10 h to obtain CoFeLDH@FeNCNTs / CC.

[0046] (III) CoFeLDH@FeNCNTs / CC was reduced in a reducing atmosphere using CVD to obtain CoFe@FeNCNTs / CC: The dried CoFe LDH@FeNCNTs / CC was placed on a porcelain boat. Without weighing melamine, argon-hydrogen gas was directly introduced, and the temperature was raised to 900℃ at a rate of 5℃ / min for further annealing. After holding at this temperature for 180min, the reaction was completed. After cooling, the mixture was removed to obtain CoFe@FeNCNTs / CC.

[0047] (iv) Pt@CoFe@FeNCNTs / CC were obtained by magnetron sputtering under an inert atmosphere: A 1*4 cm² piece of CoFe@FeNCNTs / CC was cut and placed in a magnetron sputtering instrument. Platinum metal was sputtered for 12 min under an argon atmosphere, at 3 Pa, DC, and 75 W. The resulting methanol fuel cell catalyst is denoted as Pt@CoFe@FeNCNTs / CC.

[0048] Catalytic performance evaluation: The ORR (Orientation-Reduction) LSV (Low-Speed ​​Value) curves of the Pt@CoFe@FeNCNTs / CC sample and the commercial 20wt.% Pt / C catalyst in 0.5M 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.

[0049] The Pt@CoFe@FeNCNTs / CC sample exhibited ORR electrocatalytic performance of 0.732 V vs. RHE and 0.812 V vs. RHE.

[0050] The catalytic activity of MOR was also tested using RED (Reactive Chromatography). The CV (Chemical Activity Regulator) curve for MOR was measured in a mixed solution of 0.5 M H₂SO₄ and 0.5 M CH₃OH saturated with N₂. A commercial 20 wt.% Pt / C catalyst was tested under the same conditions, and the results are as follows: Figure 3As shown, the Pt@CoFe@FeNCNTs / CC sample exhibits almost no peaks in the forward oxidation peak (If) and backward scanning peak (Ib).

[0051] Comparative Example 4: The preparation method of a catalyst (Pt@FeNCNTs / CC) for sputtering Pt onto the surface of nitrogen-doped iron-based carbon nanotubes includes the following steps: (a) Preparation of nitrogen-doped iron-based carbon nanotubes; Cut a 3*4cm² piece of carbon cloth and place it in ethanol and deionized water respectively, sonicating for 15 min each time. Weigh 3.892g FeSO₄•7H₂O, dissolve it in 70mL of deionized water, stir well, and then place the sonicated carbon cloth in it. Soak it at 60℃ for 12 h. After that, take out the iron-coated carbon cloth and dry it in an oven for 12 h. Place the dried iron-coated carbon cloth on a ceramic boat and put it in a tube furnace. Introduce argon and ammonia gas, heat it to 500℃ at a heating rate of 5℃ / min, and hold it at that temperature for 30 min for nitriding. After cooling, take out the ceramic boat. Weigh 3g of melamine and place it in the ceramic boat above the iron-coated carbon cloth for nitriding. Put it in a tube furnace, introduce argon gas, and heat it to 850℃ at a heating rate of 10℃ / min for further annealing. After holding at that temperature for 120 min, the reaction is complete. After cooling, take out the nitrogen-doped iron-based carbon nanotubes, denoted as FeNCNTs / CC.

[0052] (ii) Pt@FeNCNTs / CC were obtained by magnetron sputtering under an inert atmosphere: A 1*4 cm² piece of FeNCNTs / CC was cut and placed in a magnetron sputtering instrument. Platinum metal was sputtered for 12 min under an argon atmosphere, at 3 Pa, DC, and 75 W. The resulting methanol fuel cell catalyst is denoted as Pt@FeNCNTs / CC.

[0053] Catalytic performance evaluation: The LSV curve of the ORR of Pt@FeNCNTs / CC sample in 0.5M H2SO4 solution saturated with O2 was tested using a rotating disk electrode (RDE) at a rotation speed of 1600 rpm. The results are as follows: Figure 2 As shown.

[0054] The Pt@FeNCNTs / CC sample exhibited ORR electrocatalytic performance of 0.686 V vs. RHE at half-wave potential and 0.783 V vs. RHE at onset potential.

[0055] The catalytic activity of MOR was also tested using RED (Reactive Chromatography). The CV (Chemical Activity Regulator) curve for MOR was measured in a mixed solution of 0.5 M H₂SO₄ and 0.5 M CH₃OH saturated with N₂. A commercial 20 wt.% Pt / C catalyst was tested under the same conditions, and the results are as follows: Figure 3 As shown, the forward oxidation peak (If) and backward scanning peak (Ib) of the Pt@CoFe@FeNCNTs / CC sample are 0.32 A / mgPt and 0.34 A / mgPt, respectively, and the ratio of the two peaks is If / Ib=0.94.

[0056] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0057] The above description is merely a specific embodiment of this application. However, 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 scope of the technology 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 methanol fuel cell catalyst, characterized in that, Its structural unit uses nitrogen-doped iron-based carbon nanotubes loaded with iron and cobalt single atoms as a conductive network, with metallic platinum uniformly loaded on the conductive network.

2. A method for preparing a methanol fuel cell catalyst as described in claim 1, characterized in that, Includes the following steps: S1 Preparation of nitrogen-doped iron-based carbon nanotubes; S2 hydrothermal reaction supported iron cobalt hydroxide nanosheets to obtain iron cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes; In a reducing atmosphere, iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes were reduced by CVD to obtain iron-cobalt single-atom@nitrogen-doped iron-based carbon nanotubes. In an inert atmosphere, platinum is loaded onto iron-cobalt single atoms@nitrogen-doped iron-based carbon nanotubes by magnetron sputtering to obtain platinum@iron-cobalt single atoms@nitrogen-doped iron-based carbon nanotubes, which is the catalyst for methanol fuel cells.

3. The method for preparing a methanol fuel cell catalyst according to claim 2, characterized in that, The preparation process in step S1 is as follows: S1.1 Cut the carbon cloth and place it in ethanol and deionized water in sequence for ultrasonic cleaning; S1.2 The ultrasonically treated carbon cloth is placed in FeSO4 solution and soaked at 55-65℃ for 11-13 hours. The iron-coated carbon cloth is then removed and dried to obtain iron-coated carbon cloth. S1.3 The iron-coated carbon cloth is heated to 450-550℃ at a heating rate of 4-6℃ / min under an argon-ammonia atmosphere, held at this temperature for 25-35min, and then cooled. Melamine is placed on top of the nitrided iron-coated carbon cloth, and heated to 800-900℃ at a heating rate of 9-11℃ / min under an argon atmosphere, held at this temperature for 120min, and the reaction is completed. After cooling, the nitrogen-doped iron-based carbon nanotubes are removed.

4. The method for preparing a methanol fuel cell catalyst according to claim 3, characterized in that, In step S1.2, the concentration of FeSO4 solution is 0.2 mol / L, and in step S1.3, the amount of melamine added is positively correlated with the carbon cloth area, which is 0.25 g / cm2.

5. The method for preparing a methanol fuel cell catalyst according to claim 2, characterized in that, The preparation process of step S2 is as follows: nitrogen-doped iron-based carbon nanotubes are placed in a polar aprotic solvent solution of iron salt, cobalt salt and zinc salt, reacted at 160-180℃ for 9-11 hours, removed, cleaned and dried to obtain iron-cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes.

6. The method for preparing a methanol fuel cell catalyst according to claim 5, characterized in that, In step S2, the polar aprotic solvent solutions for the iron, cobalt, and zinc salts are formamide solutions of ferrous chloride, cobalt chloride, and zinc chloride, wherein the concentrations of Fe2+ are 0.015 mol / L, Co2+ are 0.015 mol / L, and Zn2+ are 0.07 mol / L.

7. The method for preparing a methanol fuel cell catalyst according to claim 1, characterized in that, The preparation process of step S3 is as follows: iron cobalt hydroxide@nitrogen-doped iron-based carbon nanotubes are placed together with melamine, and under an argon-hydrogen atmosphere, the temperature is raised to 850-950℃ at a heating rate of 4-6℃ / min. After holding at this temperature for 2.5-3.5h, the reaction is completed, and the mixture is cooled to obtain iron cobalt single atom@nitrogen-doped iron-based carbon nanotubes.

8. The method for preparing a methanol fuel cell catalyst according to claim 1, characterized in that, The conditions for magnetron sputtering in step S4 are: under an argon atmosphere, a pressure of 3 Pa, DC power, a power of 75 W, and a sputtering time of 12 min.

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