Direct methanol fuel cell bifunctional catalyst and preparation method thereof
By loading high-entropy alloy nanoparticles on carbon nanotubes and performing plasma modification treatment to form P-HEA-p-CNT@CC catalyst, the problems of low activity and poor stability of direct methanol fuel cell catalysts are solved, and efficient electrocatalytic performance and anti-poisoning ability are achieved.
Patent Information
- Application Number
- CN202510641013.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-09-12
AI Technical Summary
Existing direct methanol fuel cell catalysts have problems with low activity and poor stability, especially in the methanol oxidation reaction and oxygen reduction reaction, where the kinetics are slow and they are susceptible to poisoning.
Carbon nanotubes are used as conductive substrates, defects are introduced through dielectric barrier discharge, and high-entropy alloy nanoparticles composed of five transition metal elements are loaded. Combined with plasma modification treatment, P-HEA-p-CNT@CC catalysts are formed.
It improves the charge transfer efficiency of the catalyst, reduces the reaction energy barrier, enhances the catalytic activity and selectivity, improves the performance of oxygen reduction and methanol oxidation reactions, improves the cycle stability and charge-discharge performance of the catalyst, and reduces the consumption of precious metals.
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Figure CN120637511A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of direct methanol fuel cell catalysts, and in particular relates to a direct methanol fuel cell dual-function catalyst and a preparation method thereof. Background Art
[0002] Direct methanol fuel cells (DMFCs) hold great promise for applications in portable power sources and electric vehicles due to their high energy density, low-temperature operation, and easy fuel storage. However, their commercialization is hampered by sluggish kinetics of the methanol oxidation reaction (MOR) at the anode, catalyst poisoning, and high overpotential of the oxygen reduction reaction (ORR) at the cathode. Currently, platinum-based catalysts, while highly active, are expensive and susceptible to poisoning by intermediates such as CO.
[0003] In recent years, high-entropy alloys (HEAs) have demonstrated excellent anti-poisoning capabilities and catalytic stability due to the synergistic effects of their multiple components. However, their low conductivity and agglomeration have limited their application. Carbon nanotubes (CNTs) are ideal supports for manipulating electronic structure through doping and defect engineering, but traditional methods have difficulty precisely controlling defect density and distribution. Therefore, developing a bifunctional catalyst that combines high activity, stability, and low cost is key to the development of DMFCs. Summary of the Invention
[0004] The present invention aims to provide a dual-function catalyst for direct methanol fuel cells, which solves the problems of low activity and poor stability of existing catalysts through the synergistic effect of high entropy alloys and defect-rich carbon nanotubes.
[0005] The present invention provides a dual-function catalyst for direct methanol fuel cells. The structural unit of the catalyst uses carbon nanotubes as a conductive substrate, defects are introduced on the surface through dielectric barrier discharge, and the catalyst is loaded with high-entropy alloy nanoparticles composed of five transition metal elements.
[0006] The present invention provides a method for preparing a bifunctional catalyst for a direct methanol fuel cell, comprising the following steps:
[0007] S1 prepared carbon nanotubes, denoted as CNT@CC;
[0008] S2 uses dielectric barrier discharge technology to create defects on the surface of CNT@CC to obtain defect-rich carbon nanotubes, which are denoted as p-CNT@CC;
[0009] S3 synthesized multi-component high entropy alloy nanoparticles by oil bath method, denoted as HEA NPs;
[0010] In step S4, HEA NPs are loaded onto the p-CNT@CC prepared in step S2, and Ar / NH3 plasma treatment is performed to prepare a direct methanol fuel cell bifunctional catalyst, which is recorded as P-HEA-p-CNT@CC.
[0011] Preferably, the dielectric barrier discharge conditions in step S2 are: discharge voltage 30V, discharge current 60-90mA, in air atmosphere, and treatment time 1 minute to obtain p-CNT@CC.
[0012] Preferably, step S3 includes the following steps:
[0013] S3.1 Dissolve Pt(acac)2, Ni(acac)2, Fe(acac)3, Co(acac)3, and Cu(acac)2 in a mixture of 1-octadecene and oleylamine;
[0014] S3.2 Place the solution prepared in S3.1 in an oil bath at 75-85°C under nitrogen protection and maintain for 25-35 minutes, then raise the temperature again to 180-200°C, maintain under stirring for 1 hour, and then cool to 25°C;
[0015] S3.3 The black colloidal product was collected by centrifugation and washed to obtain HEA NPs, which were dispersed in cyclohexane for storage.
[0016] Preferably, in step S3.1, the molar ratio of Pt(acac)2, Ni(acac)2, Fe(acac)3, Co(acac)3, and Cu(acac)2 is 1:1:1:1:1.
[0017] Preferably, in step S3.1, the volume ratio of 1-octadecene to oleylamine is 5:9.
[0018] Preferably, step S4 includes the following steps:
[0019] S4.1 Stir the p-CNT@CC obtained in step S2 with HEA NPs dispersed in cyclohexane overnight to load the HEA NPs on the p-CNT@CC;
[0020] S4.2 was taken out and dried to obtain p-CNT@CC loaded with HEA NPs;
[0021] S4.3 Place it in a high-temperature tube furnace, Ar / H2 mixed gas, and heat it to 400℃ at the same heating rate and hold for 4h to obtain HEA-p-CNT@CC;
[0022] S4.4 Place HEA-p-CNT@CC into a plasma-enhanced chemical vapor deposition device, introduce Ar / NH3, and perform plasma modification. The pressure inside the tube is 20 Pa, the discharge power is 75 W, and the discharge time is 30 min to obtain P-HEA-p-CNT@CC.
[0023] Preferably, step S1 includes the following steps:
[0024] S1.1 Cut the carbon cloth and sonicate it with ethanol for 5 minutes;
[0025] S1.2 Pour the prepared potassium permanganate solution and continue ultrasonication for 5 minutes. Remove and rinse with deionized water and ethanol.
[0026] S1.3 Soak the carbon cloth in a 0.2 M FeSO4 solution at 60°C for 12 hours and dry it in an oven.
[0027] S1.4 Place the dried carbon cloth into a porcelain boat and heat it in a tube furnace under an Ar / NH3 flow at 500°C for 30 minutes.
[0028] S1.5 Add melamine to the porcelain boat, place the sample on top of the porcelain boat, and then heat to 850℃ in an argon atmosphere at a flow rate of 50mL / min and keep warm for 2 hours to allow CFs to grow on CC to produce CNT@CC.
[0029] Compared with the prior art, the present invention has the following advantages:
[0030] The catalyst has excellent ORR and MOR electrocatalytic performance. The use of high entropy alloys and the introduction of plasma modification treatment in the preparation method can improve charge transfer efficiency, reduce reaction energy barriers, improve electrocatalytic activity and selectivity, enhance ORR and MOR reaction performance, and improve cycle stability and charge-discharge performance. The specific reasons are as follows:
[0031] (1) Carbon nanotubes themselves have excellent electrical conductivity. The electronegativity of nitrogen is much greater than that of carbon, which makes the electrically neutral carbon material doped with nitrogen positively charged and easy to deposit metal nanoparticles. At the same time, the carbon material can promote the adsorption of oxygen and the decomposition of intermediate peroxides. The nitrogen-containing functional groups can increase the electron affinity with the matrix and promote the ability of the metal to donate electrons, thereby improving the activity of the catalyst. Carbon nanotubes have rich void structures and abundant active sites, which can make them exhibit excellent electrocatalytic oxygen reduction performance. Carbon nanotubes have a high specific surface area and a stable three-dimensional structure, which can make electrochemically active substances more easily attached to the surface of carbon nanotubes, improving their catalytic performance.
[0032] (2) Dielectric barrier plasma discharge treatment of carbon nanotubes creates some defects on the surface of carbon nanotubes, making it easier for high-entropy alloys to be loaded on the carbon nanotubes and improving the bonding strength between the carrier and the catalyst. Plasma treatment can introduce new chemical bonds and functional groups on the surface of the carrier, making the bond between the carrier and the catalyst stronger. This not only prevents the catalyst from falling off or agglomerating from the carrier during the reaction, but also improves the stability and service life of the catalyst.
[0033] (3) High entropy alloys are loaded on carbon nanotubes to achieve low consumption of precious metals while maintaining their high activity. Significant progress has been made in the application of Pt high entropy alloy catalysts in methanol fuel cells. High entropy alloys are composed of multiple metal elements, and there is a synergistic effect between Pt and other metals. The electronic structures and chemical properties of different metals influence each other, which can adjust the d-band center position of Pt, optimize the adsorption and desorption ability of the catalyst for methanol oxidation reaction intermediates, make the reaction easier to proceed, and thus improve the catalytic activity. In addition, more active sites can be added. The mixture of multiple metal elements and the unique crystal structure of high entropy alloys may produce more active sites. These active sites can provide more reaction sites, making it easier for methanol molecules to adsorb and react, thereby accelerating the reaction rate and improving the performance of the battery.
[0034] (3) Chemical vapor deposition (PECVD) modification of the catalyst surface to improve the catalytic activity and durability of the bifunctional catalyst; in plasma-enhanced chemical vapor deposition equipment, the introduction of Ar / NH3 plasma can enhance the stability and conductivity of the material, making it have excellent bifunctional activity that can be applied to direct methanol fuel cells. Plasma treatment can produce more defects, vacancies and active sites on the catalyst surface. These newly added active sites can provide more places for the adsorption and reaction of methanol molecules, making the reaction more likely to occur, thereby significantly improving the activity of the catalyst; optimizing the electronic structure, the electronic structure of the atoms on the catalyst surface, and adjusting its chemical activity. The electron cloud density on the catalyst surface can be changed, thereby optimizing the catalyst's adsorption and desorption ability for methanol oxidation intermediates, reducing the reaction energy barrier, and increasing the reaction rate; enhancing anti-poisoning ability: plasma modification can adjust the chemical properties of the catalyst surface, so that the catalyst's adsorption characteristics for intermediates in the methanol oxidation reaction, such as carbon monoxide (CO), change. Reduce the adsorption intensity of CO on the catalyst surface and reduce the occupation of CO on the catalyst active sites, thereby enhancing the catalyst's anti-poisoning ability. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 The microscopic morphology of P-HEA-p-CNT@CC prepared in Example 1 under a scanning electron microscope (SEM) (scale bar 500 nm);
[0036] Figure 2 Linear sweep voltammetry (LSV) plots of oxygen reduction reaction (ORR) of Example 1, Comparative Examples 1, 2, 3, 4, and a commercial Pt / C catalyst;
[0037] Figure 3 1 is a linear sweep voltammetry (LSV) diagram of methanol oxidation reaction (MOR) of Example 1, Comparative Examples 1, 2, 3, 4, and a commercial Pt / C catalyst. DETAILED DESCRIPTION
[0038] The following description of embodiments of the present invention is provided in conjunction with the accompanying drawings, in which various details of the embodiments of the present invention are included to facilitate understanding. These details should be considered as merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.
[0039] Example 1
[0040] A bifunctional catalyst for direct methanol fuel cells, whose structural units use carbon nanotubes as a conductive substrate, defects are introduced on the surface through dielectric barrier discharge, and are loaded with high-entropy alloy nanoparticles composed of five transition metal elements.
[0041] The preparation method comprises the following steps:
[0042] Synthesis of S1 carbon nanotubes:
[0043] First, a 4×4 carbon cloth was cut and ultrasonicated with ethanol for 5 minutes. Then, a prepared potassium permanganate solution was poured into the cloth and ultrasonicated continuously for 5 minutes. After removal, it was rinsed continuously with deionized water and ethanol. The carbon cloth was immersed in a 0.2M FeSO4 solution at 60°C for 12 hours and dried in an oven. The dried carbon cloth was then placed in a porcelain boat and heated at 500°C in a tube furnace under an Ar / NH3 flow (flow rate: 80mL / min) for 30 minutes. Finally, 2g of melamine was added to the porcelain boat, and the sample was placed on top of the porcelain boat. It was then heated to 850°C in an argon atmosphere (flow rate: 50mL / min) and kept warm for 2 hours. This led to the growth of CFs on CC, forming CF@CC and CNT@CC.
[0044] S2 uses dielectric barrier discharge technology to create defects on the surface of CNT@CC:
[0045] The dielectric barrier discharge conditions are: discharge voltage 30V, discharge current 60-90mA, air atmosphere, treatment time 1min, the surface defect density of carbon nanotubes is increased, and defect-rich carbon nanotubes are obtained, which are recorded as p-CNT@CC.
[0046] S3 synthesizes multi-element high entropy alloy nanoparticles by oil bath method:
[0047] In an Erlenmeyer flask, 0.1 mmol Pt(acac)2, 0.1 mmol Ni(acac)2, 0.1 mmol Fe(acac)3, 0.1 mmol Co(acac)3, and 0.1 mmol Cu(acac)2 were dissolved in a mixture of 5 ml 1-octadecene and 9 ml oleylamine. Under nitrogen, the mixture was heated in an 80°C oil bath for 30 minutes, then raised to 190°C and maintained under magnetic stirring for 1 hour before cooling to 25°C. The black colloidal product was collected by centrifugation and washed twice with ethanol to produce multinary high-entropy alloy nanoparticles, designated HEA NPs. Finally, the HEA NPs were stored in cyclohexane for further use.
[0048] S4: HEA NPs are loaded onto the p-CNT@CC prepared in step S2 and subjected to Ar / NH3 plasma treatment:
[0049] HEA NPs were loaded onto the p-CNT@CC prepared in step S2.
[0050] The synthesized p-CNT@CC was stirred overnight with HEA NPs dispersed in cyclohexane. The HEA NPs were then loaded onto the p-CNT@CC. After removal and drying, the HEA NPs-loaded p-CNT@CC was obtained. This p-CNT@CC was then placed in a high-temperature tube furnace and heated to 400°C at the same rate using an AR / H2 mixture for 4 hours, yielding the HEA-p-CNT@CC.
[0051] Ar / NH3 plasma treatment
[0052] The above samples were placed in a plasma-enhanced chemical vapor deposition equipment, and Ar / NH3 was introduced for plasma modification. The pressure in the tube was 20 Pa, the discharge power was 75 W, and the discharge time was 30 min. The obtained direct methanol fuel cell bifunctional catalyst was recorded as P-HEA-p-CNT@CC.
[0053] The morphology of the P-HEA-p-CNT@CC sample obtained in the verification example was analyzed by scanning electron microscopy (SEM). Figure 1 As shown in the figure, the P-HEA-p-CNT@CC sample is a uniform carbon nanotube with a relatively rough surface and a stable structure.
[0054] Bifunctional catalytic performance evaluation:
[0055] The electrocatalytic performance of the prepared direct methanol fuel cell bifunctional catalyst sample was carried out in a three-electrode device using an electrochemical workstation (CHI760E).
[0056] Preparation of the working electrode for ORR and MOR performance testing: Before using a rotating disk electrode (RDE), a glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder. The electrode was then rinsed repeatedly with deionized water, ultrasonically dried for several seconds, and dried at room temperature before use. Circular holes with a diameter of 4 mm were punched into the prepared carbon cloth using a hole punch. The DMFC bifunctional catalyst sample was bonded to the electrode using 5 wt.% Nafion as a binder. After drying, the sample was tested. Electrochemical performance testing: A standard three-electrode electrochemical system was used, with a platinum counter electrode, a saturated calomel electrode (SCE), and the prepared working electrode as the reference electrode. The test solution was 0.5 M H2SO4 solution (pH = 1). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg2Cl2) + 0.2415 + 0.059 pH. Before the linear sweep voltammetry (LSV) test, the working electrode was charged at 10 mVs -1 The electrochemical performance was evaluated by cyclic voltammetry (CV) for 50 cycles at a scan rate of 1.5 Å. All electrochemical tests were performed at room temperature.
[0057] The ORR LSV curves of P-HEA-p-CNT@CC sample and commercial 20wt.% Pt / C catalyst were tested in 0.5M H2SO4 solution saturated with O2 at a rotation speed of 1600rpm. The results are shown in Figure 2. Figure 2 The P-HEA-p-CNT@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.8995 V vs. RHE and a half-wave potential of 0.7495 V vs. RHE. The P-HEA-p-CNT@CC sample exhibited a high limiting current density of 26.06 mA cm -2 , which is higher than that of commercial Pt / C catalyst (14.96 mA cm -2 ), indicating that the P-HEA-p-CNT@CC sample has faster reaction kinetics in the ORR electrocatalytic process.
[0058] The MOR catalytic activity of P-HEA-p-CNT@CC samples was tested in 0.5M H2SO4+1M CH3OH solution saturated with N2 using a rotating disk electrode (RDE). Figure 3The LSV curves of the MOR catalytic performance of the P-HEA-p-CNT@CC sample show that the P-HEA-p-CNT@CC sample has excellent MOR electrocatalytic activity, and its specific activity is 52.94 mA / cm -2 and 33.07 mA / cm -2 , which are 3.95 times and 13.55 times that of 20wt.% Pt / C. Under the same test conditions, they are far superior to commercial Pt / C catalysts, indicating that the P-HEA-p-CNT@CC sample has excellent MOR electrocatalytic activity.
[0059] Comparative Example 1:
[0060] The preparation method of a high entropy alloy-supported carbon nanotube-surface direct methanol fuel cell bifunctional catalyst (HEA-CNT@CC) specifically comprises the following steps:
[0061] Synthesis of S1 carbon nanotubes:
[0062] First, a 4×4 carbon cloth was cut and ultrasonicated with ethanol for 5 minutes. Then, a prepared potassium permanganate solution was poured into the cloth and ultrasonicated continuously for 5 minutes. After removal, it was rinsed continuously with deionized water and ethanol. The carbon cloth was immersed in a 0.2M FeSO4 solution at 60°C for 12 hours and dried in an oven. The dried carbon cloth was then placed in a porcelain boat and heated at 500°C in a tube furnace under an Ar / NH3 flow (flow rate: 80mL / min) for 30 minutes. Finally, 2g of melamine was added to the porcelain boat, and the sample was placed on top of the porcelain boat. It was then heated to 850°C in an argon atmosphere (flow rate: 50mL / min) and kept warm for 2 hours. This led to the growth of CFs on CC, forming CF@CC and CNT@CC.
[0063] S2 synthesizes multi-element high entropy alloy nanoparticles by oil bath method:
[0064] In an Erlenmeyer flask, 0.1 mmol of Pt(acac)2, 0.1 mmol of Ni(acac)2, 0.1 mmol of Fe(acac)3, 0.1 mmol of Co(acac)3, and 0.1 mmol of Cu(acac)2 were dissolved in a mixture of 5 ml of 1-octadecene and 9 ml of oleylamine. Under nitrogen, the mixture was heated in an 80°C oil bath for 30 minutes, then raised to 190°C and maintained under magnetic stirring for 1 hour before cooling to 25°C. The black colloidal product was collected by centrifugation and washed twice with ethanol. This yielded multi-component high-entropy alloy nanoparticles, designated HEA NPs. Finally, the black colloidal product was stored in cyclohexane for further use.
[0065] S3 loads the prepared multi-element high entropy alloy nanoparticles on the surface of carbon nanotubes:
[0066] The synthesized CNT@CC was stirred with HEA NPs dispersed in cyclohexane overnight, and then the HEA NPs were loaded onto the CNT@CC. After removal and drying, the HEA NPs-loaded CNT@CC was obtained.
[0067] It was placed in a high-temperature tube furnace with AR / H2 mixed gas, heated to 400℃ at the same heating rate and maintained for 4h to obtain HEA-CNT@CC.
[0068] The morphology of the HEA-CNT@CC sample obtained in the verification example was analyzed by scanning electron microscopy (SEM). Figure 1 As shown in the figure, the HEA-CNT@CC sample is a uniform carbon nanotube with a relatively rough surface and a stable structure.
[0069] Bifunctional catalytic performance evaluation:
[0070] The electrocatalytic performance of the prepared direct methanol fuel cell bifunctional catalyst sample was carried out in a three-electrode device using an electrochemical workstation (CHI760E).
[0071] Preparation of the working electrode for ORR and MOR performance testing: Before using a rotating disk electrode (RDE), a glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder. The electrode was then rinsed repeatedly with deionized water, ultrasonically dried for several seconds, and dried at room temperature before use. Circular holes with a diameter of 4 mm were punched into the prepared carbon cloth using a hole punch. The DMFC bifunctional catalyst sample was bonded to the electrode using 5 wt.% Nafion as a binder. After drying, the sample was tested. Electrochemical performance testing: A standard three-electrode electrochemical system was used, with a platinum counter electrode, a saturated calomel electrode (SCE), and the prepared working electrode as the reference electrode. The test solution was 0.5 M H2SO4 solution (pH = 1). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg2Cl2) + 0.2415 + 0.059 pH. Before the linear sweep voltammetry (LSV) test, the working electrode was charged at 10 mVs -1 The electrochemical performance was evaluated by cyclic voltammetry (CV) for 50 cycles at a scan rate of 1.5 Å. All electrochemical tests were performed at room temperature.
[0072] The ORR LSV curve of HEA-CNT@CC sample was tested in 0.5M H2SO4 solution saturated with O2 at a rotation speed of 1600rpm using a rotating disk electrode (RDE). Figure 2The HEA-CNT@CC sample exhibits high ORR electrocatalytic activity, with an onset potential of 0.8565 V vs. RHE and a half-wave potential of 0.63 V vs. RHE. The HEA-CNT@CC sample exhibits a high limiting current density of 22.21 mA cm -2 , indicating that the reaction kinetics of the HEA-CNT@CC sample in the ORR electrocatalytic process is lower than that of the P-HEA-p-CNT@CC catalyst under the same conditions.
[0073] The MOR catalytic activity of HEA-CNT@CC samples was tested in a 0.5M H2SO4+0.5M CH3OH solution saturated with N2 using a rotating disk electrode (RDE). Figure 3 The LSV curve of the MOR catalytic performance of the HEA-CNT@CC sample shows that its specific activity is 16.32 mA / cm -2 ,4.60mA / cm -2 , which is lower than that of P-HEA-p-CNT@CC catalyst under the same conditions.
[0074] Comparative Example 2:
[0075] The preparation method of a high entropy alloy-supported carbon nanotube-surface direct methanol fuel cell bifunctional catalyst (HEA-p-CNT@CC) specifically comprises the following steps:
[0076] Synthesis of S1 carbon nanotubes:
[0077] First, a 4×4 carbon cloth was cut and ultrasonicated with ethanol for 5 minutes. Then, a prepared potassium permanganate solution was poured into the cloth and ultrasonicated continuously for 5 minutes. After removal, it was rinsed continuously with deionized water and ethanol. The carbon cloth was immersed in a 0.2M FeSO4 solution at 60°C for 12 hours and dried in an oven. The dried carbon cloth was then placed in a porcelain boat and heated at 500°C in a tube furnace under an Ar / NH3 flow (flow rate: 80mL / min) for 30 minutes. Finally, 2g of melamine was added to the porcelain boat, and the sample was placed on top of the porcelain boat. It was then heated to 850°C in an argon atmosphere (flow rate: 50mL / min) and kept warm for 2 hours. This led to the growth of CFs on CC, forming CF@CC and CNT@CC.
[0078] S2 uses dielectric barrier discharge technology to create defects on the surface of CNT@CC:
[0079] The dielectric barrier discharge conditions are: discharge voltage 30V, discharge current 60-90mA, air atmosphere, treatment time 1min, the surface defect density of carbon nanotubes is increased, and defect-rich carbon nanotubes are obtained, which are recorded as p-CNT@CC.
[0080] S3 synthesizes multi-element high entropy alloy nanoparticles by oil bath method:
[0081] In an Erlenmeyer flask, 0.1 mmol of Pt(acac)2, 0.1 mmol of Ni(acac)2, 0.1 mmol of Fe(acac)3, 0.1 mmol of Co(acac)3, and 0.1 mmol of Cu(acac)2 were dissolved in a mixture of 5 ml of 1-octadecene and 9 ml of oleylamine. Under nitrogen, the mixture was heated in an 80°C oil bath for 30 minutes, then raised to 190°C and maintained under magnetic stirring for 1 hour before cooling to 25°C. The black colloidal product was collected by centrifugation and washed twice with ethanol. This yielded multi-component high-entropy alloy nanoparticles, designated HEA NPs. Finally, the black colloidal product was stored in cyclohexane for further use.
[0082] S4 loads the prepared high entropy alloy on the surface of carbon nanotubes:
[0083] The synthesized p-CNT@CC was stirred with HEA NPs dispersed in cyclohexane overnight, and then the HEA NPs were loaded onto the p-CNT@CC. After removal and drying, the HEA NPs-loaded p-CNT@CC was obtained.
[0084] It was placed in a high-temperature tube furnace with AR / H2 mixed gas, heated to 400℃ at the same heating rate and maintained for 4h to obtain HEA-p-CNT@CC.
[0085] The morphology of the HEA-p-CNT@CC sample obtained in the verification example was analyzed by scanning electron microscopy (SEM). Figure 1 As shown in the figure, the HEA-p-CNT@CC sample is a uniform carbon nanotube with a relatively rough surface and a stable structure.
[0086] Bifunctional catalytic performance evaluation:
[0087] The electrocatalytic performance of the prepared direct methanol fuel cell bifunctional catalyst sample was carried out in a three-electrode device using an electrochemical workstation (CHI760E).
[0088] Preparation of the working electrode for ORR and MOR performance testing: Before using a rotating disk electrode (RDE), a glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder. The electrode was then rinsed repeatedly with deionized water, ultrasonically dried for several seconds, and dried at room temperature before use. Circular holes with a diameter of 4 mm were punched into the prepared carbon cloth using a hole punch. The DMFC bifunctional catalyst sample was bonded to the electrode using 5 wt.% Nafion as a binder. After drying, the sample was tested. Electrochemical performance testing: A standard three-electrode electrochemical system was used, with a platinum counter electrode, a saturated calomel electrode (SCE), and the prepared working electrode as the reference electrode. The test solution was 0.5 M H2SO4 solution (pH = 1). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg2Cl2) + 0.2415 + 0.059 pH. Before the linear sweep voltammetry (LSV) test, the working electrode was charged at 10 mVs -1 The electrochemical performance was evaluated by cyclic voltammetry (CV) for 50 cycles at a scan rate of 1.5 Å. All electrochemical tests were performed at room temperature.
[0089] The ORR LSV curve of HEA-p-CNT@CC sample was tested in 0.5M H2SO4 solution saturated with O2 at a rotation speed of 1600rpm using a rotating disk electrode (RDE). Figure 2 The P-HEA-p-CNT@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.8555 V vs. RHE and a half-wave potential of 0.72 V vs. RHE. The HEA-p-CNT@CC sample exhibited a high limiting current density of 18.84 mA cm -2 , indicating that the reaction kinetics of the HEA-p-CNT@CC sample in the ORR electrocatalytic process is lower than that of the P-HEA-p-CNT@CC catalyst under the same conditions.
[0090] The MOR catalytic activity of HEA-p-CNT@CC samples was tested in a 0.5M H2SO4+0.5M CH3OH solution saturated with N2 using a rotating disk electrode (RDE). Figure 3 The LSV curve of the MOR catalytic performance of the HEA-p-CNT@CC sample shows that its specific activity is 24.44 mA / cm -2 ,13.21mA / cm -2 , which is lower than that of P-HEA-p-CNT@CC catalyst under the same conditions.
[0091] Comparative Example 3:
[0092] The preparation method of a direct methanol fuel cell bifunctional catalyst composed of a high entropy alloy supported on the surface of carbon nanotubes (P-HEA-CNT@CC) specifically comprises the following steps:
[0093] Synthesis of S1 carbon nanotubes:
[0094] First, a 4×4 carbon cloth was cut and ultrasonicated with ethanol for 5 minutes. Then, a prepared potassium permanganate solution was poured into the cloth and ultrasonicated continuously for 5 minutes. After removal, it was rinsed continuously with deionized water and ethanol. The carbon cloth was immersed in a 0.2M FeSO4 solution at 60°C for 12 hours and dried in an oven. The dried carbon cloth was then placed in a porcelain boat and heated at 500°C in a tube furnace under an Ar / NH3 flow (flow rate: 80mL / min) for 30 minutes. Finally, 2g of melamine was added to the porcelain boat, and the sample was placed on top of the porcelain boat. It was then heated to 850°C in an argon atmosphere (flow rate: 50mL / min) and kept warm for 2 hours. This led to the growth of CFs on CC, forming CF@CC and CNT@CC.
[0095] S2 synthesizes multi-element high entropy alloy nanoparticles by oil bath method:
[0096] In an Erlenmeyer flask, 0.1 mmol of Pt(acac)2, 0.1 mmol of Ni(acac)2, 0.1 mmol of Fe(acac)3, 0.1 mmol of Co(acac)3, and 0.1 mmol of Cu(acac)2 were dissolved in a mixture of 5 ml of 1-octadecene and 9 ml of oleylamine. Under nitrogen, the mixture was heated in an 80°C oil bath for 30 minutes, then raised to 190°C and maintained under magnetic stirring for 1 hour before cooling to 25°C. The black colloidal product was collected by centrifugation and washed twice with ethanol. This yielded multi-component high-entropy alloy nanoparticles, designated HEA NPs. Finally, the black colloidal product was stored in cyclohexane for further use.
[0097] S3 HEA NPs are loaded onto the p-CNT@CC prepared in step S2 and subjected to Ar / NH3 plasma treatment:
[0098] HEA NPs were loaded onto the p-CNT@CC prepared in step S2.
[0099] The synthesized p-CNT@CC was stirred overnight with HEA NPs dispersed in cyclohexane. The HEA NPs were then loaded onto the p-CNT@CC. After removal and drying, the HEA NPs-loaded p-CNT@CC was obtained. This p-CNT@CC was then placed in a high-temperature tube furnace and heated to 400°C at the same rate using an AR / H2 mixture for 4 hours, yielding the HEA-p-CNT@CC.
[0100] Ar / NH3 plasma treatment
[0101] The above samples were placed in a plasma-enhanced chemical vapor deposition equipment, and Ar / NH3 was introduced for plasma modification. The pressure in the tube was 20 Pa, the discharge power was 75 W, and the discharge time was 30 min. The obtained direct methanol fuel cell bifunctional catalyst was recorded as P-HEA-p-CNT@CC.
[0102] The morphology of the P-HEA-CNT@CC sample obtained in the verification example was analyzed by scanning electron microscopy (SEM). Figure 1 As shown in the figure, the P-HEA-CNT@CC sample is a uniform carbon nanotube with a relatively rough surface and a stable structure.
[0103] Bifunctional catalytic performance evaluation:
[0104] The electrocatalytic performance of the prepared direct methanol fuel cell bifunctional catalyst sample was carried out in a three-electrode device using an electrochemical workstation (CHI760E).
[0105] Preparation of the working electrode for ORR and MOR performance testing: Before using a rotating disk electrode (RDE), a glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder. The electrode was then rinsed repeatedly with deionized water, ultrasonically dried for several seconds, and dried at room temperature before use. Circular holes with a diameter of 4 mm were punched into the prepared carbon cloth using a hole punch. The DMFC bifunctional catalyst sample was bonded to the electrode using 5 wt.% Nafion as a binder. After drying, the sample was tested. Electrochemical performance testing: A standard three-electrode electrochemical system was used, with a platinum counter electrode, a saturated calomel electrode (SCE), and the prepared working electrode as the reference electrode. The test solution was 0.5 M H2SO4 solution (pH = 1). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg2Cl2) + 0.2415 + 0.059 pH. Before the linear sweep voltammetry (LSV) test, the working electrode was charged at 10 mVs -1 The electrochemical performance was evaluated by cyclic voltammetry (CV) for 50 cycles at a scan rate of 1.5 Å. All electrochemical tests were performed at room temperature.
[0106] The ORR LSV curve of P-HEA-CNT@CC sample was tested in 0.5M H2SO4 solution saturated with O2 at a rotation speed of 1600rpm using a rotating disk electrode (RDE). Figure 2The P-HEA-CNT@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.8785 V vs. RHE and a half-wave potential of 0.85 V vs. RHE. The P-HEA-CNT@CC sample exhibited a high limiting current density of 24.63 mA cm -2 , indicating that the reaction kinetics of the P-HEA-CNT@CC sample in the ORR electrocatalytic process is lower than that of the P-HEA-p-CNT@CC catalyst under the same conditions.
[0107] The MOR catalytic activity of P-HEA-CNT@CC samples was tested in a 0.5M H2SO4+0.5M CH3OH solution saturated with N2 using a rotating disk electrode (RDE). Figure 3 The LSV curve of the MOR catalytic performance of the P-HEA-CNT@CC sample shows that its specific activity is 42.99 mA / cm -2 ,19.82mA / cm -2 , which is lower than that of P-HEA-p-CNT@CC catalyst under the same conditions.
[0108] Comparative Example 4:
[0109] The preparation method of a direct methanol fuel cell bifunctional catalyst (P-HEA-p@CC) with high entropy alloy supported on the surface of carbon nanotubes specifically comprises the following steps:
[0110] S1 carbon cloth processing:
[0111] First, cut a 4×4 carbon cloth, ultrasonicate it with ethanol for 5 minutes, then pour it into the prepared potassium permanganate solution and continue ultrasonicating it for 5 minutes. After taking it out, rinse it continuously with deionized water and ethanol, and dry it in an oven.
[0112] S2 plasma treatment of carbon nanotubes to form defect-rich carbon nanotubes:
[0113] The dielectric barrier discharge conditions are: discharge voltage 30V, discharge current 60-90mA, air atmosphere, treatment time 1min, the surface defect density of carbon nanotubes is increased, and defect-rich carbon nanotubes are obtained, which are recorded as p@CC.
[0114] S3 synthesizes multi-element high entropy alloy nanoparticles by oil bath method:
[0115] In an Erlenmeyer flask, 0.1 mmol of Pt(acac)2, 0.1 mmol of Ni(acac)2, 0.1 mmol of Fe(acac)3, 0.1 mmol of Co(acac)3, and 0.1 mmol of Cu(acac)2 were dissolved in a mixture of 5 ml of 1-octadecene and 9 ml of oleylamine. Under nitrogen, the mixture was heated in an 80°C oil bath for 30 minutes, then raised to 190°C and maintained under magnetic stirring for 1 hour before cooling to 25°C. The black colloidal product was collected by centrifugation and washed twice with ethanol. This yielded multi-component high-entropy alloy nanoparticles, designated HEA NPs. Finally, the black colloidal product was stored in cyclohexane for further use.
[0116] S4: HEA NPs are loaded onto the p-CNT@CC prepared in step S2 and subjected to Ar / NH3 plasma treatment:
[0117] HEA NPs were loaded onto the p-CNT@CC prepared in step S2.
[0118] The synthesized p-CNT@CC was stirred overnight with HEA NPs dispersed in cyclohexane. The HEA NPs were then loaded onto the p-CNT@CC. After removal and drying, the HEA NPs-loaded p-CNT@CC was obtained. This p-CNT@CC was then placed in a high-temperature tube furnace and heated to 400°C at the same rate using an AR / H2 mixture for 4 hours, yielding the HEA-p-CNT@CC.
[0119] Ar / NH3 plasma treatment
[0120] The above samples were placed in a plasma-enhanced chemical vapor deposition equipment, and Ar / NH3 was introduced for plasma modification. The pressure in the tube was 20 Pa, the discharge power was 75 W, and the discharge time was 30 min. The obtained direct methanol fuel cell bifunctional catalyst was recorded as P-HEA-p-CNT@CC.
[0121] The morphology of the P-HEA-p@CC sample obtained in the verification example was analyzed by scanning electron microscopy (SEM). Figure 1 As shown in the figure, the P-HEA-p@CC sample is a uniform carbon nanotube with a relatively rough surface and a stable structure.
[0122] Bifunctional catalytic performance evaluation:
[0123] The electrocatalytic performance of the prepared direct methanol fuel cell bifunctional catalyst sample was carried out in a three-electrode device using an electrochemical workstation (CHI760E).
[0124] Preparation of the working electrode for ORR and MOR performance testing: Before using a rotating disk electrode (RDE), a glassy carbon electrode (GCE, d = 4.0 mm) was polished to a mirror finish using a polishing cloth containing Al2O3 powder. The electrode was then rinsed repeatedly with deionized water, ultrasonically dried for several seconds, and dried at room temperature before use. Circular holes with a diameter of 4 mm were punched into the prepared carbon cloth using a hole punch. The DMFC bifunctional catalyst sample was bonded to the electrode using 5 wt.% Nafion as a binder. After drying, the sample was tested. Electrochemical performance testing: A standard three-electrode electrochemical system was used, with a platinum counter electrode, a saturated calomel electrode (SCE), and the prepared working electrode as the reference electrode. The test solution was 0.5 M H2SO4 solution (pH = 1). All potentials were calculated using the Nernst equation with reference to the reversible hydrogen electrode (RHE): E(RHE) = E(Hg / Hg2Cl2) + 0.2415 + 0.059 pH. Before the linear sweep voltammetry (LSV) test, the working electrode was charged at 10 mVs -1 The electrochemical performance was evaluated by cyclic voltammetry (CV) for 50 cycles at a scan rate of 1.5 Å. All electrochemical tests were performed at room temperature.
[0125] The ORR LSV curve of P-HEA-p@CC sample was tested in 0.5M H2SO4 solution saturated with O2 at a rotation speed of 1600rpm using a rotating disk electrode (RDE). Figure 2 The P-HEA-p@CC sample exhibited high ORR electrocatalytic activity, with an onset potential of 0.8145 V vs. RHE and a half-wave potential of 0.0.5525 V vs. RHE. The P-HEA-p@CC sample also exhibited a high limiting current density of 18.23 mA cm -2 , indicating that the reaction kinetics of the P-HEA-p@CC sample in the ORR electrocatalytic process is lower than that of the P-HEA-p-CNT@CC catalyst under the same conditions.
[0126] The MOR catalytic activity of P-HEA-p@CC sample was tested in 0.5M H2SO4+0.5M CH3OH solution saturated with N2 using a rotating disk electrode (RDE). Figure 3 The LSV curves of the MOR catalytic performance of the P-HEA-p@CC samples show that their specific activities are 10.19 mA / cm -2 and 2.19 mA / cm -2 , which is lower than that of P-HEA-p-CNT@CC catalyst under the same conditions.
[0127] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.
Claims
1. A bifunctional catalyst for a direct methanol fuel cell, characterized by: Its structural unit uses carbon nanotubes as a conductive substrate, defects are introduced on the surface through dielectric barrier discharge, and it is loaded with high-entropy alloy nanoparticles composed of five transition metal elements.
2. A method for preparing a bifunctional catalyst for a direct methanol fuel cell according to claim 1, characterized in that: The following steps are involved: S1 prepared carbon nanotubes, denoted as CNT@CC; S2 uses dielectric barrier discharge technology to create defects on the surface of CNT@CC to obtain defect-rich carbon nanotubes, which are denoted as p-CNT@CC; S3 synthesized multi-component high entropy alloy nanoparticles by oil bath method, denoted as HEA NPs; In step S4, HEA NPs are loaded onto the p-CNT@CC prepared in step S2, and Ar / NH3 plasma treatment is performed to prepare a direct methanol fuel cell bifunctional catalyst, which is recorded as P-HEA-p-CNT@CC.
3. The method for preparing a bifunctional catalyst for direct methanol fuel cells according to claim 2, characterized in that: In step S2 , the dielectric barrier discharge conditions are: discharge voltage 30 V, discharge current 60-90 mA, in air atmosphere, and treatment time 1 minute to obtain p-CNT@CC.
4. The method for preparing a bifunctional catalyst for a direct methanol fuel cell according to claim 2, wherein: Step S3 includes the following steps: S3.1 Dissolve Pt(acac)2, Ni(acac)2, Fe(acac)3, Co(acac)3, and Cu(acac)2 in a mixture of 1-octadecene and oleylamine; S3.2 Place the solution prepared in S3.1 in an oil bath at 75-85°C under nitrogen protection and maintain for 25-35 minutes, then raise the temperature again to 180-200°C, maintain under stirring for 1 hour, and then cool to 25°C; S3.3 The black colloidal product was collected by centrifugation and washed to obtain HEA NPs, which were dispersed in cyclohexane for storage.
5. The method for preparing a bifunctional catalyst for a direct methanol fuel cell according to claim 4, characterized in that: The molar ratio of Pt(acac)2, Ni(acac)2, Fe(acac)3, Co(acac)3, and Cu(acac)2 in step S3.1 is 1:1:1:1:
1.
6. The method for preparing a bifunctional catalyst for a direct methanol fuel cell according to claim 4, characterized in that: The volume ratio of 1-octadecene to oleylamine in step S3.1 is 5:
9.
7. The method for preparing a bifunctional catalyst for a direct methanol fuel cell according to claim 2, wherein: The step S4 comprises the following steps: S4.1 Stir the p-CNT@CC obtained in step S2 with HEA NPs dispersed in cyclohexane overnight to load the HEA NPs on the p-CNT@CC; S4.2 was taken out and dried to obtain p-CNT@CC loaded with HEA NPs; S4.3 Place it in a high-temperature tube furnace, Ar / H2 mixed gas, and heat it to 400℃ at the same heating rate and hold for 4h to obtain HEA-p-CNT@CC; S4.4 Place HEA-p-CNT@CC into a plasma-enhanced chemical vapor deposition device, introduce Ar / NH3, and perform plasma modification. The pressure inside the tube is 20 Pa, the discharge power is 75 W, and the discharge time is 30 min to obtain P-HEA-p-CNT@CC.
8. The method for preparing a bifunctional catalyst for a direct methanol fuel cell according to claim 2, wherein: Step S1 includes the following steps: S1.1 Cut the carbon cloth and sonicate it with ethanol for 5 minutes; S1.2 Pour the prepared potassium permanganate solution and continue ultrasonication for 5 minutes. Remove and rinse with deionized water and ethanol. S1.3 Soak the carbon cloth in a 0.2 M FeSO4 solution at 60°C for 12 hours and dry it in an oven. S1.4 Place the dried carbon cloth into a porcelain boat and heat it in a tube furnace under an Ar / NH3 flow at 500°C for 30 minutes. S1.5 Add melamine to the porcelain boat, place the sample on top of the porcelain boat, and then heat to 850℃ in an argon atmosphere at a flow rate of 50mL / min and keep warm for 2 hours to allow CFs to grow on CC to produce CNT@CC.