A colloidal-assisted growth CNT / WC platinum-loaded composite material, its preparation method and application

Abstract

This invention discloses a colloidal-assisted growth CNT / WC platinum-loaded composite material, its preparation method, and its application. The preparation method of the CNT / WC platinum-loaded composite material includes the following steps: (1) preparing an iron hydroxide colloidal solution and adding an appropriate amount of ammonium metatungstate to prepare a mixed solution; (2) injecting the mixed solution into ethanol under ultrasound using a microporous membrane syringe to obtain a solid product; (3) oxidizing the solid sample at high temperature, and then reducing and carbonizing the oxidized sample under a hydrogen-rich atmosphere using a programmed temperature rise-gas-solid reaction method, and cooling after carbonization to obtain an Fe / CNT / WC sample; (4) obtaining the CNT / WC platinum-loaded composite material using a displacement method. This invention provides the application of the CNT / WC platinum-loaded composite material as an electrocatalyst in hydrogen-oxygen fuel cells, which significantly improves the hydrogen evolution performance of the cathode reaction in hydrogen-oxygen fuel cells compared to ordinary commercial Pt / C catalysts.

Description

Technical Field

[0001] This invention relates to a CNT / WC composite material, its preparation method, and its application as an electrocatalyst in hydrogen-oxygen fuel cells. Background Technology

[0002] Composite materials are materials composed of two or more materials with different properties, combined macroscopically through physical or chemical methods to achieve new properties. The various materials complement each other, creating a synergistic effect that makes the overall performance of the composite material superior to that of the original constituent materials, thus meeting various requirements.

[0003] Tungsten carbide (WC) is a metallic carbide with platinum-like catalytic activity, and therefore has been widely used in catalysts and catalyst matrices in recent years. Numerous studies have shown that tungsten carbide can be widely applied in many fields of electrocatalysis, especially as a matrix, where it exhibits synergistic effects with active metals from the noble metal series, thereby improving the overall performance of composite materials. Carbon nanotubes (CNTs) are one-dimensional carbon materials that can be prepared by chemical vapor deposition (CVD) using transition metals such as iron, cobalt, and nickel as catalysts. They possess high rigidity and are often used to support the spatial structure of composite materials. Furthermore, carbon nanotubes have excellent tunability, which can be used to control the structure of composite materials. Simultaneously, due to their excellent electrical conductivity, carbon nanotubes are widely used in electrocatalysis. Platinum metal exhibits excellent electrocatalytic activity in the electrolysis of water to produce hydrogen. The composite of platinum and CNT / WC has significant potential value in improving material performance. How to utilize more tunable processes to prepare platinum-loaded CNT / WC materials with special structures will be a valuable research hotspot.

[0004] The composite of tungsten carbide and platinum must address two key challenges: First, the in-situ growth of carbon nanotubes, as the catalysts used for growing carbon nanotubes are prone to particle agglomeration during the high-temperature carbonization process; second, how to load platinum onto tungsten carbide and whether a stable bonding structure can be formed. Otherwise, even if a combination is achieved, the two are merely a simple superposition, with negligible influence on their electronic structure, and the composite material's functionality cannot be demonstrated.

[0005] Combining the concept of composite materials, the combination of a stable WC matrix and highly dispersed and stably bonded platinum nanoparticles holds promise for mutual compensation, thereby further enhancing performance. Therefore, this type of research is highly favored by materials scientists, especially those working on related engineering applications. However, developing a method that can control both the particle size of the WC matrix and the distribution of platinum on the surface remains challenging. Currently, platinum-loaded materials are commonly prepared using liquid-phase potassium borohydride reduction (reference: APPL CATAL B-ENVIRON, 106, 3–4, 423-432). However, this method is influenced by numerous factors, such as the concentration of potassium borohydride, pH value, and the rate and order of addition, all of which affect the morphology and particle size of metallic platinum. Especially in large-scale preparation, the agglomeration of platinum is difficult to address, leading to challenges in cost control and process standardization, making large-scale preparation difficult and representing a significant challenge in materials preparation.

[0006] Therefore, developing composite catalysts with simple preparation conditions and stable, controllable platinum dispersion is a key and important approach to significantly improve the activity of composite nanocatalysts. Furthermore, if the platinum dispersion can be effectively controlled and the preparation steps reduced, production time, energy consumption, and associated production costs can be significantly decreased.

[0007] To date, there have been no reports on the preparation of CNT / WC platinum-loaded composite materials using a microporous membrane colloidal-assisted method. Summary of the Invention

[0008] The first technical problem to be solved by the present invention is to provide a microporous membrane colloidal-assisted preparation method for CNT / WC platinum-loaded composite materials. The composite material prepared by this method has stable bonding between its components, good thermal stability, and the particle size of the CNT / WC platinum-loaded composite material can be controlled at the nanometer to micrometer level to adapt to different application environments.

[0009] The second technical problem to be solved by the present invention is to provide a CNT / WC platinum-loaded composite material.

[0010] The third technical problem to be solved by the present invention is to provide the application of the CNT / WC platinum-loaded composite material as an electrocatalyst in hydrogen-oxygen fuel cells.

[0011] The technical solution of the present invention will be described in detail below.

[0012] In a first aspect, the present invention provides a method for preparing a CNT / WC platinum-loaded composite material, the method comprising the following steps:

[0013] (1) Take an appropriate amount of ferric nitrate nonahydrate and an appropriate amount of urea in a container, and control the mass ratio of urea to ferric nitrate nonahydrate to be 2:0.5-2. Add deionized water, and the amount of deionized water added is 5-15 mL / g based on the mass of urea. Heat to 60-90℃ and stir for 5-10 min to obtain ferric hydroxide colloidal solution. Take the prepared colloidal solution and add an appropriate amount of ammonium metatungstate to prepare a mixed solution, wherein the atomic mass ratio of tungsten to iron is 4:0.1-2, preferably 4:0.25-1, and more preferably 4:0.75.

[0014] (2) Prepare a microporous membrane syringe. The microporous membrane syringe consists of a syringe, a piston rod that matches the syringe, and a microporous hydrophobic membrane. The other end of the syringe is sealed with a microporous hydrophobic membrane. The syringe controls the piston rod to ensure that the solution in the syringe passes through the microporous hydrophobic membrane and enters from one side to the other. Before use, the syringe is activated in a 50-90% ethanol solution. Take the mixed solution prepared in step (1) and place it in the syringe of the microporous membrane syringe. Take ethanol in an open container so that the volume ratio of the mixed solution in the syringe to ethanol is 5:50-150. Place the open container in an ultrasonic machine for ultrasonication. Control the piston rod to inject the mixed solution in the microporous membrane syringe into the ethanol in the ultrasonication at room temperature. When injecting, insert the microporous membrane into the ethanol. After injection, sonicate for 10-30 minutes. Centrifuge the turbid liquid after ultrasonication and take the precipitate after centrifugation to dry in a vacuum oven at 50-80℃.

[0015] (3) The dried sample obtained in step (2) is oxidized in a muffle furnace at 400℃~700℃ for 1~4h. Then, the oxidized sample is reduced and carbonized in a hydrogen-rich atmosphere using a programmed temperature rise-gas-solid reaction method. After carbonization, the sample is cooled to obtain Fe / CNT / WC sample. The hydrogen-rich atmosphere is a mixture of H2 and CO gas.

[0016] (4) The Fe / CNT / WC sample obtained in step (3) is placed in a certain amount of chloroplatinic acid solution for displacement reaction according to the required platinum loading. The solid obtained from the displacement reaction is then separated into solid and liquid and dried to obtain CNT / WC platinum-loaded composite material.

[0017] In step (1) of this invention, the composite material is achieved by using urea hydrolysis in a mixed solution to generate ferric hydroxide colloid. Specifically, three chemical reactions occur in the mixed solution. First, urea undergoes hydrolysis at 60-90°C to produce ammonia. Then, the ammonia combines with water in the solution to form ammonia water and ionizes to generate a large number of hydroxide ions. Finally, iron ions combine with hydroxide ions to generate ferric hydroxide colloid, which adheres to the solid in the solution in step (2), thereby achieving the composite material. The urea content, temperature, and time all affect the formation of the colloid. If the urea content is too low, not enough hydroxide ions will be generated in the solution to combine with iron ions to form a colloid. If the urea content is too high, an excessive amount of hydroxide ions will be generated and rapidly combine with iron ions, resulting in aggregated ferric hydroxide, which cannot achieve good dispersion of iron. Experimental results show that the urea content should be set to a mass ratio of urea to ferric nitrate of 2:0.5-2, with a preferred mass ratio of 2:1-1.5. Temperature directly determines the hydrolysis rate of urea, thus affecting the formation rate of ferric hydroxide colloid. When the temperature is below 60°C, urea in the solution does not undergo hydrolysis. When the temperature reaches above 60°C, the higher the temperature, the faster the hydrolysis of urea. However, when the temperature is above 95°C, the solution temperature approaches the boiling point of water, causing a large amount of urea to hydrolyze and iron ions to hydrolyze themselves to form aggregated iron hydroxide. Preferably, the heating temperature is 80-90°C and the stirring time is 5-10 minutes.

[0018] In step (2) of this invention, the microporous hydrophobic membrane used is a PP polypropylene microporous filter membrane with a pore size of 0.1 μm. The microporous membrane syringe can be prepared using the following method: the head of a disposable medical syringe is cut off and smoothed, the microporous hydrophobic membrane is placed on the syringe head and bonded with hot melt adhesive to achieve end sealing, thus obtaining the microporous membrane syringe. Since the PP polypropylene microporous filter membrane is a hydrophobic membrane, the syringe with the microporous membrane needs to be activated in an ethanol solution before use. The activated microporous membrane is modified into a hydrophilic membrane that can be permeated by water. For the selection of the microporous membrane and the preparation process of the syringe, it is necessary to ensure that the syringe is resistant to ethanol and can maintain a certain stability during ethanol ultrasonication without leakage. The syringe needs to ensure that the solution enters from one side of the microporous membrane to the other. In step (2) of this invention, ultrasonic treatment is used to fully disperse the colloid and ammonium metatungstate in anhydrous ethanol. Appropriately extending the ultrasonic treatment time helps to obtain a more uniformly dispersed precursor turbidity; the preferred ultrasonic treatment time is 10–30 minutes. In specific implementation, the ultrasonic conditions can be: ultrasonic power of 50-100W and ultrasonic frequency of 20-40KHz. The ultrasonically treated turbid liquid is centrifuged, and the precipitate after centrifugation is dried in a vacuum oven at 50-80℃. Excessive temperature will cause the precursor to agglomerate, and the preferred drying temperature is 50-60℃.

[0019] In step (3) of this invention, the dried precipitate obtained in step (2) is oxidized in an air atmosphere in a muffle furnace at 600°C for 2 hours to completely oxidize the sample. The oxidized solid is then placed in a tube furnace and carbonized in a hydrogen-rich atmosphere to prepare an iron / tungsten carbide / carbon nanotube composite material (Fe-WC-CNT). The hydrogen-rich atmosphere is a mixture of H2 and CO, preferably with CO at a flow rate of 100–200 ml / min and H2 at a flow rate of 10–50 ml / min. The preferred carbonization conditions are: heating to 800–900°C at a heating rate of 3–7°C / min and holding for 1–3 hours.

[0020] In step (4) of this invention, platinum loading is achieved by platinum replacement of iron / tungsten carbide / carbon nanotube composite particles in a platinum-containing compound solution. The platinum content in the composite material is controlled by the feeding ratio of the iron / tungsten carbide / carbon nanotube composite particles to the chloroplatinic acid solution. Preferably, the platinum-containing compound solution is a chloroplatinic acid solution with a concentration of 3–10 mmol / L; the chloroplatinic acid solution is fed in at a mass of Pt of 5%–20% of the mass of the prepared platinum / tungsten carbide / carbon nanotube composite material; the preferred replacement temperature is 30–80°C, and the preferred replacement time is 5–12 hours. After the replacement reaction, the composite material may still contain iron. The presence of this iron does not reduce its electrocatalytic performance, so it generally does not need to be removed. If removal is required, the iron can be removed by acid washing the solid obtained after the replacement reaction in a 10–20% hydrochloric acid solution for 1–3 hours.

[0021] Secondly, the present invention provides a CNT / WC platinum-loaded composite material prepared according to the above preparation method.

[0022] Thirdly, this invention provides the application of the aforementioned CNT / WC platinum-supported composite material (Pt / CNT / WC) as an electrocatalyst in hydrogen-oxygen fuel cells. Results show that the aforementioned CNT / WC platinum-supported composite material significantly improves catalytic conversion efficiency compared to commercial Pt / C.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) Advantages of the preparation method: This invention utilizes the hydrolysis of urea in a mixed solution to generate stable ferric hydroxide colloid, which adheres to amine metatungstate. CNT / WC is obtained through oxidative carbonization, achieving uniform distribution of Fe on the support surface. Furthermore, the reactivity of Fe is utilized to achieve good dispersion of platinum on the support surface through a substitution reaction. In the CNT / WC platinum-loaded composite material (Pt / CNT / WC), Pt is obtained through in-situ substitution of Fe, eliminating many steps and the consumption of reducing agents and other raw materials in conventional Pt-loading methods. The process is simple, and costs are effectively reduced. The Pt loading of the composite material can be easily controlled by the amount of Fe introduced and the amount of chloroplatinic acid solution added later, making the operation simple and convenient.

[0025] (2) Advantages of the structure and performance of CNT / WC platinum-loaded composite materials: Due to the in-situ replacement of the load, the components of the CNT / WC platinum-loaded composite material are stably bonded and the effective components are not easily detached, thereby improving the utilization rate of Pt and enhancing the catalytic activity; the use of carbon nanotubes as a support in the composite material increases the stability of the catalyst, and the coexistence of WC and Pt further enhances the catalytic activity of the platinum-loaded catalyst; the particle size of the composite material can be controlled by the carbon nanotube support, and can be adjusted to the nanometer to micrometer level to adapt to different application environments.

[0026] (3) Advantages of CNT / WC platinum-loaded composite material as an electrocatalyst in hydrogen-oxygen fuel cells: CNT / WC platinum-loaded composite material as an electrocatalyst has significantly improved hydrogen evolution performance in the cathode reaction of hydrogen-oxygen fuel cells compared with ordinary commercial Pt / C catalyst. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope (SEM) image of the CNT / WC platinum-loaded composite material prepared in Example 1 of the present invention.

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the oxidized sample prepared in Example 1 of the present invention.

[0029] Figure 3 The figures show the characterization of the hydrogen evolution catalytic activity of the CNT / WC platinum-loaded composite material and the commercial Pt / C (5% platinum loading) prepared in Examples 1, 2, 3, and 4 of this invention. The commercial Pt / C (5% platinum loading) used in the tests was purchased from Aladdin Reagent (Shanghai) Co., Ltd.; the counter electrode was a platinum electrode, and the reference electrode was a saturated calomel electrode; the solution used in the tests was a 0.5M sulfuric acid aqueous solution, and the scan rate was 50 mV / s.

[0030] Figure 4 This is a photograph of the suspension formed after microporous membrane injection in Comparative Example 2 of the present invention.

[0031] Figure 5 This is a schematic diagram of the preparation in step (2) of the present invention. Detailed Implementation

[0032] The following embodiments, in conjunction with the accompanying drawings, will further illustrate the present invention, but the scope of protection of the present invention is not limited thereto:

[0033] The microporous membrane syringe used in this embodiment of the invention is prepared by the following method: the needle part of a 5mL disposable medical syringe is cut off and smoothed; a PP polypropylene microporous filter membrane with a pore size of 0.1μm is placed at the syringe head and bonded with hot melt adhesive (e.g., ...). Figure 5 As shown in the figure, the ends are sealed to prepare a microporous membrane syringe.

[0034] Example 1:

[0035] Take 0.67g of ferric nitrate nonahydrate and 0.89g of urea in a beaker, wherein the mass ratio of urea to ferric nitrate is 2:1.5. Add 5ml of deionized water, heat to 90℃, and stir for 10min to obtain a ferric hydroxide colloidal solution.

[0036] Before use, the microporous membrane syringe is activated in 70% ethanol solution for 5 minutes. 0.5g of ammonium metatungstate is mixed with 5ml of prepared ferric hydroxide colloidal solution and placed in the syringe barrel. The atomic mass ratio of tungsten to iron is 4:0.75. 150ml of ethanol is placed in a beaker and ultrasonicated in an ultrasonic machine with a power of 100W and an ultrasonic frequency of 40KHZ. The mixed solution is injected into the ethanol solution during ultrasonication through the syringe. During injection, the membrane should be immersed in the ethanol solution. After injection, ultrasonication is performed for 30 minutes. The turbid liquid after ultrasonication is centrifuged and the precipitate is dried in a vacuum oven at 50℃. The dried solid is oxidized in a muffle furnace at 600℃ for 2 hours to obtain solid A.

[0037] The oxidized sample A was carbonized in a tube furnace under a mixed atmosphere of CO (100 ml / min) and H2 (20 ml / min). The carbonization temperature was increased to 900℃ at a programmed rate of 5℃ / min and held for 3 hours. After cooling, Fe-WC-CNT particles were obtained. The obtained particles were immersed in a 5 mmol / L chloroplatinic acid solution at 80℃, wherein the chloroplatinic acid solution contained 5% Pt by mass of the target composite material. After holding at room temperature for 8 hours, the particles were filtered, washed, and dried to obtain the CNT / WC platinum-loaded composite material. Figure 1 The image shows a scanning electron microscope (SEM) image of the prepared CNT / WC platinum-loaded composite material. Figure 2 This is a scanning electron microscope (SEM) image of sample A after oxidation in Example 1.

[0038] The prepared CNT / WC platinum-supported composite material was used to prepare an electrocatalyst. The specific steps included:

[0039] (1) Pretreatment of working electrode: First, polish the working electrode (glassy carbon electrode) to a mirror finish with Al2O3 powder and clean it. Then, activate the glassy carbon electrode in 0.2mol / L KCl + 1mmol / L K3Fe(CN)6 solution and perform cyclic voltammetry scans in the potential range of -0.1 to 0.5V at a scan rate of 50mV / s. When the peak potential difference of the obtained cyclic voltammetry curve is about 70mV, the electrode is ready for use.

[0040] (2) Preparation of working electrode: Weigh 3 mg of CNT / WC platinum-loaded composite material and place it in a sample tube. Add 390 μL of ethanol and 10 μL of 5% Nafion to prepare an emulsion. After ultrasonic dispersion for 30 min, a uniform catalyst slurry is obtained. Use a micropipette to pick up 5 μL of the catalyst slurry and drop it onto the surface of the glassy carbon electrode. Dry at 50 °C to obtain the working electrode.

[0041] (3) The test was conducted using a three-port H-type electrolytic cell, with a platinum electrode as the counter electrode and a saturated calomel electrode as the reference electrode; the test solution was sulfuric acid solution (0.5M), and the scan rate was 50 mV / s. The results are as follows: Figure 3 As shown.

[0042] (4) Using commercially available Pt / C (5% platinum loading, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) as a comparison, the working electrode was prepared and tested according to the same method described above, and the results are as follows: Figure 3 As shown.

[0043] Example 2:

[0044] Take 0.503g of ferric nitrate nonahydrate and 0.774g of urea in a beaker, wherein the mass ratio of urea to ferric nitrate is 2:1.3. Add 6ml of deionized water, heat to 85℃, and stir for 7min to obtain a ferric hydroxide colloidal solution.

[0045] Before use, the microporous membrane syringe is activated in 70% ethanol solution for 5 minutes. 0.5g of ammonium metatungstate is mixed with 5ml of prepared ferric hydroxide colloidal solution and placed in the syringe barrel. The atomic mass ratio of tungsten to iron is 4:1. 130ml of ethanol is placed in a beaker and ultrasonicated in an ultrasonic machine with a power of 100W and an ultrasonic frequency of 40KHZ. The mixed solution is injected into the ethanol solution during ultrasonication through the syringe. During injection, the membrane should be immersed in the ethanol solution. After injection, ultrasonication is performed for 25 minutes. The turbid liquid after ultrasonication is centrifuged and the precipitate is dried in a vacuum oven at 55℃. The dried solid is oxidized in a muffle furnace at 500℃ for 3 hours to obtain solid A.

[0046] The oxidized sample A was carbonized in a tube furnace under a mixed atmosphere of CO (150 ml / min) and H2 (30 ml / min). The carbonization temperature was increased to 850°C at a programmed rate of 4°C / min and held for 2 hours. After cooling, Fe-WC-CNT particles were obtained. The obtained particles were immersed in a 6 mmol / L chloroplatinic acid solution at 70°C. The chloroplatinic acid solution contained 6% Pt by mass of the target composite material. After holding at room temperature for 9 hours, the particles were filtered, washed, and dried to obtain the CNT / WC platinum-loaded composite material.

[0047] Performance tests were conducted according to the electrocatalyst preparation and application method of Example 1, and the results are as follows: Figure 3 As shown.

[0048] Example 3:

[0049] Take 0.335g of ferric nitrate nonahydrate and 0.558g of urea in a beaker, wherein the mass ratio of urea to ferric nitrate is 2:1.2. Add 7ml of deionized water, heat to 85℃, and stir for 9min to obtain a ferric hydroxide colloidal solution.

[0050] Before use, the microporous membrane syringe is activated in 70% ethanol solution for 5 minutes. 0.5g of ammonium metatungstate is mixed with 5ml of prepared ferric hydroxide colloidal solution and placed in the syringe barrel. The atomic mass ratio of tungsten to iron is 4:0.5. 140ml of ethanol is placed in a beaker and ultrasonicated in an ultrasonic machine with a power of 100W and an ultrasonic frequency of 40KHZ. The mixed solution is injected into the ethanol during ultrasonication through the syringe. During injection, the membrane should be immersed in the ethanol solution. After injection, ultrasonication is performed for 20 minutes. The turbid liquid after ultrasonication is centrifuged and the precipitate is dried in a vacuum oven at 55℃. The dried solid is oxidized in a muffle furnace at 550℃ for 3 hours to obtain solid A.

[0051] The oxidized sample A was carbonized in a tube furnace under a mixed atmosphere of CO (130 ml / min) and H2 (25 ml / min). The carbonization temperature was increased to 850°C at a programmed rate of 6°C / min and held for 2 hours. After cooling, Fe-WC-CNT particles were obtained. The obtained particles were immersed in a 7 mmol / L chloroplatinic acid solution at 60°C. The chloroplatinic acid solution contained 7% Pt by mass of the target composite material. After holding at room temperature for 12 hours, the particles were filtered, washed, and dried to obtain the CNT / WC platinum-loaded composite material.

[0052] Performance tests were conducted according to the electrocatalyst preparation and application method of Example 1, and the results are as follows: Figure 3 As shown.

[0053] Example 4:

[0054] Take 0.168g of ferric nitrate nonahydrate and 0.336g of urea in a beaker, with a mass ratio of urea to ferric nitrate of 2:1. Add 5ml of deionized water, heat to 80℃, and stir for 5min to obtain a ferric hydroxide colloidal solution.

[0055] Before use, the microporous membrane syringe is activated in 70% ethanol solution for 5 minutes. 0.5g of ammonium metatungstate is mixed with 5ml of prepared ferric hydroxide colloidal solution and placed in the syringe barrel. The atomic mass ratio of tungsten to iron is 4:0.25. 120ml of ethanol is placed in a beaker and ultrasonicated in an ultrasonic machine with a power of 100W and an ultrasonic frequency of 40KHZ. The mixed solution is injected into the ethanol during ultrasonication through the syringe. During injection, the membrane should be immersed in the ethanol solution. After injection, ultrasonication is performed for 30 minutes. The turbid liquid after ultrasonication is centrifuged and the precipitate after centrifugation is dried in a vacuum oven at 60℃. The dried solid is oxidized in a muffle furnace at 700℃ for 1 hour to obtain solid A.

[0056] The oxidized sample A was carbonized in a tube furnace under a mixed atmosphere of CO (100 ml / min) and H2 (50 ml / min). The carbonization temperature was increased to 800°C at a programmed rate of 5°C / min and held for 3 hours. After cooling, Fe-WC-CNT particles were obtained. The obtained particles were immersed in a 5 mmol / L chloroplatinic acid solution at 50°C. The chloroplatinic acid solution contained 5% Pt by mass of the target composite material. After holding at room temperature for 9 hours, the particles were filtered, washed, and dried to obtain the CNT / WC platinum-loaded composite material.

[0057] Performance tests were conducted according to the electrocatalyst preparation and application method of Example 1, and the results are as follows: Figure 3 As shown.

[0058] Comparative Example 1

[0059] Take 0.67g of ferric nitrate nonahydrate and 0.89g of urea in a beaker, with a mass ratio of urea to ferric nitrate of 2:1.5. Add 5ml of deionized water, heat to 100℃, and stir for 30min. At this time, the ferric hydroxide colloidal solution will precipitate. The precipitated ferric hydroxide cannot pass through the membrane through the syringe, and the CNT / WC platinum-loaded composite material cannot be obtained.

[0060] Comparative Example 2

[0061] Take 0.67g of ferric nitrate nonahydrate and 0.335g of urea in a beaker, wherein the mass ratio of urea to ferric nitrate is 1:2. Add 5ml of deionized water, heat to 70℃, and stir for 3min to obtain a ferric hydroxide colloidal solution.

[0062] Before use, activate the microporous membrane syringe in 70% ethanol solution for 5 minutes. Mix 0.5g of ammonium metatungstate with 5ml of prepared ferric hydroxide colloidal solution and place the mixture into the syringe barrel. The atomic mass ratio of tungsten to iron is 4:0.75. Place 150ml of ethanol in a beaker and sonicate it in an ultrasonic machine with a power of 100W and an ultrasonic frequency of 40kHz. Inject the mixed solution into the ethanol solution during sonication using the syringe. During injection, the membrane should be immersed in the ethanol solution. The image after injection is shown below. Figure 4 As shown, because ferric nitrate was not completely hydrolyzed, residual iron ions were present in the ethanol solution, making it impossible to precisely control the atomic mass ratio of tungsten and iron.

Claims

1. A method for preparing a CNT / WC platinum-loaded composite material, characterized in that: The preparation method includes the following steps: (1) Take an appropriate amount of ferric nitrate nonahydrate and an appropriate amount of urea in a container, and control the mass ratio of urea to ferric nitrate nonahydrate to be 2:0.5-2. Add deionized water, and the amount of deionized water added is 5-15 mL / g based on the mass of urea. Heat to 60-90℃ and keep warm for 5-10 min to obtain ferric hydroxide colloidal solution. Take the prepared colloidal solution and add an appropriate amount of ammonium metatungstate to prepare a mixed solution, wherein the atomic mass ratio of tungsten to iron is 4:0.1-2. (2) Prepare a microporous membrane syringe. The microporous membrane syringe consists of a syringe, a piston rod that matches the syringe, and a microporous hydrophobic membrane. The other end of the syringe is sealed with a microporous hydrophobic membrane. The syringe controls the piston rod to ensure that the solution in the syringe passes through the microporous hydrophobic membrane and enters from one side to the other. Before use, the syringe is activated in a 50-90% ethanol solution. Take the mixed solution prepared in step (1) and place it in the syringe of the microporous membrane syringe. Take ethanol in an open container so that the volume ratio of the mixed solution in the syringe to ethanol is 5:50-150. Place the open container in an ultrasonic machine for ultrasonication. Control the piston rod to inject the mixed solution in the microporous membrane syringe into the ethanol in the ultrasonication at room temperature. When injecting, insert the microporous membrane into the ethanol. After injection, sonicate for 10-30 minutes. Centrifuge the turbid liquid after ultrasonication and take the precipitate after centrifugation to dry in a vacuum oven at 50-80℃. (3) The dried sample obtained in step (2) is oxidized in a muffle furnace at 400℃~700℃ for 1~4h. Then, the oxidized sample is reduced and carbonized in a hydrogen-rich atmosphere using a programmed temperature rise-gas-solid reaction method. After carbonization, the sample is cooled to obtain Fe / CNT / WC sample. The hydrogen-rich atmosphere is a mixture of H2 and CO gas. (4) The Fe / CNT / WC sample obtained in step (3) is placed in a certain amount of chloroplatinic acid solution for displacement reaction according to the required platinum loading. The solid obtained from the displacement reaction is then separated into solid and liquid and dried to obtain CNT / WC platinum-loaded composite material.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of urea to ferric nitrate is 2:1 to 1.5; the heating temperature is 80 to 90°C; and the stirring time is 5 to 10 minutes.

3. The preparation method according to claim 1, characterized in that: In step (1), the atomic mass ratio of tungsten to iron is 4:0.25 to 1.

4. The preparation method according to claim 3, characterized in that: In step (1), the atomic mass ratio of tungsten to iron is 4:0.

75.

5. The preparation method according to claim 1, characterized in that: In step (2), the microporous hydrophobic membrane used is a PP polypropylene microporous filter membrane with a pore size of 0.1 μm.

6. The preparation method according to claim 1 or 3, characterized in that: The microporous membrane syringe was prepared by the following method: the head of a disposable medical syringe was cut off and smoothed, a microporous hydrophobic membrane was placed on the syringe head and bonded with hot melt adhesive to achieve end sealing, thus obtaining the microporous membrane syringe.

7. The preparation method according to claim 1, characterized in that: In step (2), the precipitate after centrifugation is dried in a vacuum oven at 50-60℃.

8. The preparation method according to claim 1, characterized in that: In step (3), oxidation is carried out at 600℃ for 2 hours.

9. The preparation method according to claim 1, characterized in that: In step (3), the hydrogen-rich atmosphere is a mixture of H2 and CO, wherein CO is 100-200 ml / min and H2 is 10-50 ml / min; the carbonization conditions are: heating to 800-900℃ at a heating rate of 3-7℃ / min and holding for 1-3 hours.

10. The preparation method according to claim 1, characterized in that: In step (4), the concentration of the chloroplatinic acid solution is 3-10 mmol / L; the chloroplatinic acid solution is added at a mass of 5%-20% of the mass of the prepared CNT / WC platinum-loaded composite material containing Pt; the displacement temperature is 30-80℃ and the displacement time is 5-12 hours.

11. The CNT / WC platinum-loaded composite material prepared by the method according to claim 1.

12. The application of the CNT / WC platinum-supported composite material as described in claim 11 as an electrocatalyst in hydrogen-oxygen fuel cells.

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