Platinum-loaded nitrogen-doped graphene and preparation method and application thereof

Abstract

The application relates to the technical field of graphene, in particular to platinum-loaded nitrogen-doped graphene as well as a preparation method and application thereof. The preparation method of the platinum-loaded nitrogen-doped graphene comprises the following steps: mixing graphene oxide, a platinum salt and a solvent to form a mixed solution, and then performing a hydrothermal reaction to prepare graphene oxide-platinum salt composite powder; mixing the graphene oxide-platinum salt composite powder with an amino compound, and performing ball milling to prepare amino-modified graphene oxide-platinum salt composite powder; and performing microwave irradiation on the amino-modified graphene oxide-platinum salt composite powder to prepare platinum-loaded nitrogen-doped graphene. The preparation process is simple, and the prepared platinum-loaded nitrogen-doped graphene has good oxygen reduction catalytic activity.

Description

Technical Field

[0001] This application relates to the field of graphene technology, and in particular to a platinum-nitrogen-doped graphene, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are increasingly becoming a research focus as a novel clean energy source. The membrane electrode assembly (MEA), often referred to as the heart of a PEMFC, is a core component of the technology, and the anode and cathode catalysts are crucial for improving MEA performance.

[0003] Platinum-carbon catalysts are currently the most widely used and commercially mature catalysts in proton exchange membrane fuel cells. Traditional platinum-carbon catalysts use relatively large platinum metal particles, which are prone to agglomeration during use, reducing catalyst lifespan and catalytic activity. To enhance catalytic activity while reducing production costs, researchers have chosen to modify platinum-carbon catalysts. Currently, novel platinum-carbon catalysts are mainly prepared through two pathways: alloying platinum metal particles and modifying the matrix material supporting the platinum metal particles. Alloying platinum metal particles refers to platinum forming a Pt-M alloy with transition metals and supporting it on a carbon matrix. Modification of the support typically focuses on improving its specific surface area, conductivity, and chemical stability. The modification methods used are often liquid-phase or solid-phase synthesis processes, such as using three-dimensional graphene as a template to electrodeposit platinum nanoparticles on the surface via electrical pulses, chemically depositing platinum-silver alloy nanoparticles on the graphene surface using different redox potentials, or growing platinum particles on carbon nanotube supports through impregnation combined with thermal reduction.

[0004] However, these methods are typically complex and time-consuming. Furthermore, liquid-phase preparation processes often use large amounts of organic solvents and surfactants, which are difficult to remove completely, leading to the introduction of impurities. The use of large amounts of organic solvents also increases subsequent processing costs. Solid-phase preparation processes usually require high-temperature sintering, resulting in high energy consumption. Moreover, the preparation of small-sized platinum metal particles requires prolonged thermal reflux, leading to long reaction cycles and increased production costs. Summary of the Invention

[0005] Therefore, it is necessary to provide a platinum-nitrogen-doped graphene, its preparation method, and its application. The preparation method is simple, does not introduce impurities, and the obtained platinum-nitrogen-doped graphene can improve the oxygen reduction catalytic activity when used as a fuel cell catalyst.

[0006] In a first aspect, this application provides a method for preparing platinum-nitrogen-doped graphene, which includes the following steps:

[0007] Graphene oxide, platinum salt, and solvent are mixed to form a mixture, which is then subjected to a hydrothermal reaction to prepare graphene oxide-platinum salt composite powder.

[0008] The graphene oxide-platinum salt composite powder was mixed with an amino compound and ball-milled to prepare an amino-modified graphene oxide-platinum salt composite powder; and

[0009] Platinum-nitrogen-doped graphene was prepared by microwave irradiation of the amino-modified graphene oxide-platinum salt composite powder.

[0010] In some embodiments, the platinum salt includes chloroplatinic acid and / or platinum acetate.

[0011] In some embodiments, the amino compound includes ammonia and / or urea.

[0012] In some embodiments, the graphene oxide has 1 to 10 layers and an oxygen content of 30 at% to 60 at%.

[0013] In some embodiments, the mass ratio of carbon atoms in the graphene oxide to platinum atoms in the platinum salt is (0.5–3):1.

[0014] In some embodiments, the mass ratio of carbon atoms in the graphene oxide-platinum salt composite powder to nitrogen atoms in the amino compound is (1-10):1.

[0015] In some embodiments, the hydrothermal reaction is carried out at a temperature of 80°C to 120°C for a time of 0.5 h to 3 h.

[0016] In some embodiments, the power of the microwave irradiation is 1kW to 15kW, and the duration is 5s to 300s.

[0017] In some embodiments, the ball mill rotates at a speed of 200 rpm to 500 rpm for a time of 0.5 h to 3 h.

[0018] In some embodiments, the method for forming the mixture includes:

[0019] The graphene oxide is dispersed in water to form a graphene oxide dispersion.

[0020] The platinum salt is dissolved in an organic solvent to form a platinum salt solution; and

[0021] The dispersion is mixed with the platinum salt solution to form the mixture;

[0022] Optionally, the organic solvent includes ethanol and / or ethylene glycol.

[0023] Secondly, this application provides a platinum-nitrogen-doped graphene prepared by the preparation method described above.

[0024] Thirdly, this application provides the application of the aforementioned platinum-nitrogen-doped graphene as a fuel cell catalyst.

[0025] Fourthly, this application provides a membrane electrode comprising a proton exchange membrane and a catalyst layer disposed adjacent to the proton exchange membrane, wherein the catalyst layer comprises the platinum-nitrogen-doped graphene described above.

[0026] Fifthly, this application provides a proton exchange membrane fuel cell, which includes the membrane electrode described above.

[0027] The method for preparing platinum-nitrogen-doped graphene provided in this application involves a short-time hydrothermal reaction to react platinum ions in a platinum salt with oxygen-containing functional groups on the surface of graphene oxide, thereby binding platinum ions to the surface of graphene oxide. A ball milling process is then used to electrostatically adsorb and bind amino groups from an amino compound to composite functional groups on the surface of graphene oxide. Microwave irradiation is then used to replace the carbon atoms modified by functional groups in the graphene oxide with nitrogen atoms from the amino compounds, thus achieving nitrogen doping of the matrix material. Simultaneously, the high-energy effect of microwave irradiation reduces platinum ions to metallic platinum nanoparticles, and the removal of oxygen-containing functional groups reduces graphene oxide back to graphene, thereby obtaining platinum-nitrogen-doped graphene.

[0028] The preparation method provided in this application achieves the simultaneous loading of small-sized platinum nanoparticles onto the matrix material through a simple hydrothermal reaction, ball milling process, and microwave irradiation, thus realizing both nitrogen doping and platinum nanoparticle loading. After doping the matrix material with nitrogen atoms, the presence of nitrogen atoms enhances its binding force with platinum nanoparticles, strengthens the adhesion of platinum nanoparticles to the graphene surface, reduces the shedding of platinum nanoparticles during the catalytic process, and improves the stability of platinum-doped nitrogen-coated graphene as a fuel cell catalyst. Furthermore, the platinum nanoparticles loaded by this method have a small particle size and are uniformly distributed on the graphene surface. The presence of nitrogen atoms provides more catalytic active sites, enabling good catalytic activity even with a low platinum nanoparticle loading. In addition, nitrogen-doped graphene, as a matrix material, has a complete structure, good flexibility, and excellent conductivity, which further improves the overall electrochemical performance of the material while reducing platinum particle agglomeration.

[0029] In summary, the preparation method provided in this application is simple and convenient, with rapid reaction, no need for long-term reflux reaction and high-temperature treatment, and no need to use large amounts of strong acids, strong bases and organic solvents. The preparation process is green and environmentally friendly, reduces post-processing costs, and does not introduce impurities. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 TEM image of platinum nitrogen-doped graphene prepared in Example 1;

[0032] Figure 2 EDS surface scan composition distribution of platinum nitrogen-doped graphene prepared in Example 1;

[0033] Figure 3 XPS elemental analysis chromatogram of platinum nitrogen-doped graphene prepared in Example 1;

[0034] Figure 4 XPS elemental analysis chromatogram of platinum nitrogen-doped graphene prepared in Example 2;

[0035] Figure 5 XPS elemental analysis chromatogram of platinum nitrogen-doped graphene prepared in Example 3;

[0036] Figure 6 XPS elemental analysis of platinum nitrogen-doped graphene prepared in Example 4;

[0037] Figure 7 XPS elemental analysis chromatogram of platinum nitrogen-doped graphene prepared in Example 5;

[0038] Figure 8 XPS elemental analysis of the platinum-loaded graphene prepared in Comparative Example 1.

[0039] Figure 9 The ORR performance curves of platinum nitrogen-doped graphene prepared in Example 1, platinum nitrogen-doped graphene prepared in Comparative Example 1, and platinum nitrogen-doped graphene prepared in Comparative Example 2 are compared.

[0040] Figure 10 XPS elemental analysis of platinum-nitrogen-doped graphene prepared in Comparative Example 2;

[0041] Figure 11 This is a TEM image of the platinum-nitrogen-doped graphene prepared in Comparative Example 2. Detailed Implementation

[0042] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0044] To address the requirements of high specific surface area, excellent conductivity, and high chemical stability in the matrix material of platinum-carbon catalysts, modification of the matrix of traditional platinum-carbon catalysts is necessary. However, current methods for modifying the platinum-carbon catalyst matrix typically suffer from problems such as complex preparation processes, long processing times, high energy consumption, and the generation of large amounts of organic waste liquid, resulting in high production costs and the easy introduction of impurities during the preparation process. Therefore, this application provides a method for preparing platinum-nitrogen-doped graphene. This method utilizes a short-time hydrothermal reaction to react platinum ions from a platinum salt with oxygen-containing functional groups on the surface of graphene oxide sheets, thereby binding platinum ions to the graphene oxide surface. A ball milling process is then used to electrostatically adsorb and bind amino groups from an amino compound to the functional groups on the graphene oxide surface. Microwave irradiation is then used to replace the carbon atoms modified by functional groups in the graphene oxide with nitrogen atoms from the amino group, thus achieving nitrogen doping of the matrix material. Simultaneously, the high-energy effect of microwave irradiation reduces platinum ions to metallic platinum nanoparticles, and the removal of oxygen-containing functional groups reduces graphene oxide back to graphene, thereby obtaining platinum-nitrogen-doped graphene.

[0045] The preparation method provided in this application achieves the simultaneous loading of small-sized platinum nanoparticles onto the matrix material through a simple hydrothermal reaction, ball milling process, and microwave irradiation, thus realizing both nitrogen doping and platinum nanoparticle loading. After doping the matrix material with nitrogen atoms, the presence of nitrogen atoms enhances its binding force with platinum nanoparticles, strengthens the adhesion of platinum nanoparticles to the graphene surface, and improves the stability of platinum-loaded nitrogen-doped graphene as a fuel cell catalyst. Furthermore, the platinum nanoparticles loaded by this method have a small particle size and are uniformly distributed on the graphene surface. The presence of nitrogen atoms provides more catalytic active sites, enabling good catalytic activity even with a low platinum nanoparticle loading. In addition, nitrogen-doped graphene, as a matrix material, has a complete structure, good flexibility, and excellent conductivity, which reduces platinum particle agglomeration and further improves the overall electrochemical performance of the material.

[0046] In summary, the preparation method provided in this application is simple and convenient, with rapid reaction, no need for long-term reflux reaction and high-temperature treatment, and no need to use large amounts of strong acids, strong bases and organic solvents. The preparation process is green and environmentally friendly, reduces post-processing costs, and does not introduce impurities.

[0047] In a first aspect, this application provides a method for preparing platinum-nitrogen-doped graphene, comprising the following steps:

[0048] Step S100: After mixing graphene oxide, platinum salt and solvent to form a mixture, perform a hydrothermal reaction to prepare graphene oxide-platinum salt composite powder.

[0049] In this application, the choice of platinum salt is not limited, and platinum salts commonly used in the field of platinum-carbon catalyst preparation can be selected. In some embodiments, the platinum salt includes chloroplatinic acid and / or platinum acetate. It is understood that the platinum salt can be in hydrate form; for example, chloroplatinic acid can specifically be chloroplatinic acid hexahydrate.

[0050] In some embodiments, the number of graphene oxide layers is 1 to 10, and the oxygen content is 30 at% to 60 at%.

[0051] In some embodiments, the mass ratio of carbon atoms in graphene oxide to platinum atoms in platinum salt is (0.5-3):1, and may also be 0.7:1, 0.9:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, or 2.7:1.

[0052] In this application, the conditions for the hydrothermal reaction are not limited, and commonly used reaction temperatures and times in the art can be selected. In some embodiments, the hydrothermal reaction temperature is 80°C to 120°C, and the time is 0.5h to 3h.

[0053] In some embodiments, the method for forming the mixture described above can be selected from one of the following methods:

[0054] Mix graphene oxide, platinum salt, water, and organic solvent together; or

[0055] First, dissolve graphene oxide in water to form a dispersion, then dissolve platinum salt in an organic solvent to form a platinum salt solution; finally, mix the dispersion and the platinum salt solution.

[0056] First, water and an organic solvent are mixed to form a mixed solvent, and then graphene oxide and platinum salt are mixed into the organic solution.

[0057] Preferably, the method for forming the mixture includes:

[0058] Graphene oxide is dispersed in water to form a graphene oxide dispersion.

[0059] Platinum salts are dissolved in organic solvents to form platinum salt solutions; and

[0060] The dispersion is mixed with a platinum salt solution to form a mixture.

[0061] In some embodiments, the organic solvent is an alcohol solvent, including ethanol and / or ethylene glycol.

[0062] Optionally, the amount of water used is 1 mL to 10 mL relative to 1 mg of graphene oxide.

[0063] Optionally, the amount of organic solvent used is 1 mL to 15 mL relative to 1 mg of graphene oxide.

[0064] In some embodiments, the hydrothermal reaction is followed by a step of washing and / or drying the product obtained from the hydrothermal reaction. The specific methods of washing and drying are not limited; for example, washing can be done by vacuum filtration, and drying can be done by freeze drying.

[0065] Step S200: Mix the graphene oxide-platinum salt composite powder with an amino compound, and ball mill to prepare amino-modified graphene oxide-platinum salt composite powder. Specifically, the amino-modified graphene oxide-platinum salt composite powder refers to the graphene oxide-platinum salt composite precursor formed by the electrostatic adsorption and bonding between amino groups and functional groups on the surface of graphene oxide.

[0066] In some embodiments, the mass ratio of carbon atoms in the graphene oxide-platinum salt composite powder to nitrogen atoms in the amino compound is any value between (1 to 10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1.

[0067] In some embodiments, the amino compound includes ammonia and / or urea. Preferably, the amino compound is ammonia. Ammonia is commercially available, for example, with an ammonia concentration of 25%.

[0068] In this application, the ball milling process parameters are not limited, as long as they are sufficient to uniformly mix the graphene oxide-platinum salt mixed powder with the amination reagent and to form amino modification. In some embodiments, the ball milling speed is 200 rpm to 500 rpm, and the time is 0.5 h to 3 h.

[0069] In some embodiments, after ball milling, the process further includes washing and / or drying the amino-modified graphene oxide-platinum salt composite powder. The specific methods of washing and drying are not limited; for example, washing can be performed by vacuum filtration, and drying can be performed by freeze drying.

[0070] Step S300: Microwave irradiation is performed on amino-modified graphene oxide-platinum salt composite powder to prepare platinum nitrogen-doped graphene.

[0071] It is understood that microwave irradiation can be carried out in any microwave reactor commonly used in the art. In some embodiments, the power of microwave irradiation is 1kW to 15kW, for example 2kW, 5kW, 8kW, 10kW, 12kW.

[0072] In some embodiments, the microwave irradiation time is 5s to 300s, for example 10s, 20s, 50s, 80s, 100s, 120s, 150s, 200s, 220s, 250s, and 280s.

[0073] In some embodiments, microwave irradiation is performed in a protective gas atmosphere, wherein the protective gas specifically includes nitrogen and / or argon.

[0074] In one specific embodiment, the preparation method of platinum nitrogen-doped graphene includes the following steps:

[0075] Graphene oxide is dispersed in water to form a graphene oxide dispersion, and platinum salt is dissolved in an organic solvent to form a platinum salt solution. The dispersion and the platinum salt solution are then mixed to form a mixture.

[0076] The mixture was subjected to a hydrothermal reaction at 80℃~120℃ for 0.5h~3h to prepare graphene oxide-platinum salt mixed powder.

[0077] Amino-modified graphene oxide-platinum salt composite powder was prepared by mixing graphene oxide-platinum salt composite powder with an amino compound and ball milling at 200 rpm to 500 rpm for 0.5 h to 3 h.

[0078] Platinum-nitrogen-doped graphene was prepared by microwave irradiation of amino-modified graphene oxide-platinum salt composite powder at 1kW to 15kW for 5s to 300s under a protective gas atmosphere.

[0079] Secondly, this application also provides a platinum-nitrogen-doped graphene prepared by the above-described preparation method. The presence of nitrogen atoms in this platinum-nitrogen-doped graphene can enhance the bonding force between the matrix material and platinum nanoparticles, strengthen the adhesion of platinum nanoparticles to the graphene surface, reduce the shedding of platinum nanoparticles during the catalytic process, and improve the stability of platinum-nitrogen-doped graphene as a fuel cell catalyst. Moreover, the platinum nanoparticles loaded by this method have a small particle size and are uniformly distributed on the graphene surface. At the same time, the presence of nitrogen atoms provides more catalytic active sites, which can maintain good catalytic activity even with a low loading of platinum nanoparticles. In addition, the nitrogen-doped graphene, as a matrix material, has a complete structure, good flexibility, and excellent conductivity, which can further improve the overall electrochemical performance of the material while reducing platinum particle agglomeration.

[0080] In some embodiments, the nitrogen doping amount in the platinum-loaded nitrogen-doped graphene is 2 wt% to 10 wt%, and the platinum loading is 10 wt% to 40 wt%.

[0081] In some embodiments, the loaded platinum nanoparticles in the platinum-nitrogen-doped graphene have a particle size of 2 nm to 10 nm. The platinum nanoparticles in the platinum-nitrogen-doped graphene provided in this application have a smaller size, resulting in stronger catalytic activity. The platinum nanoparticles are more uniformly distributed on the surface of the graphene matrix, which has good conductivity and flexibility, greatly reducing the shedding and aggregation of platinum particles during the catalytic process.

[0082] Thirdly, this application further provides the application of the aforementioned platinum-nitrogen-doped graphene as a catalyst. This catalyst can be used in the oxygen reduction catalysis reaction at the electrode of a fuel cell.

[0083] Fourthly, this application provides a membrane electrode comprising a proton exchange membrane and a catalyst layer disposed adjacent to the proton exchange membrane, wherein the catalyst layer comprises the platinum-nitrogen-doped graphene described above.

[0084] It is understood that the catalyst layer can be located on one side of the proton exchange membrane, or it can be located on both sides of the proton exchange membrane. The catalyst layer can be formed on the proton exchange membrane using a coating process.

[0085] Fifthly, this application provides a proton exchange membrane fuel cell, which includes the membrane electrode described above.

[0086] The present application will be further described in detail below with reference to specific embodiments.

[0087] The method for testing the oxygen content in graphene oxide is: thermogravimetric analysis; ammonia concentration is 25%.

[0088] Example 1

[0089] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 40 at%) and disperse it in 50 mL of deionized water to obtain a graphene oxide dispersion. Weigh 240 mg of chloroplatinic acid hexahydrate and disperse it in 60 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the graphene oxide dispersion and stir until homogeneous to obtain a graphene oxide-chloroplatinic acid mixture.

[0090] 2) The graphene oxide-chloroplatinic acid mixture obtained in step 1) was added to a 200 mL hydrothermal reactor and hydrothermally reacted at 120 °C for 40 min. After hydrothermal reaction, the mixture was filtered, washed, and freeze-dried to obtain graphene oxide-chloroplatinic acid composite powder.

[0091] 3) The graphene oxide-chloroplatinic acid composite powder obtained in step 2) was mixed with 2 mL of ammonia water and ball-milled at 300 rpm for 40 min. After ball milling, the powder was washed and dried to obtain amino-modified graphene oxide-chloroplatinic acid composite powder. Under an argon protective atmosphere, the amino-modified graphene oxide-chloroplatinic acid composite powder was placed in the reaction chamber of a microwave reactor and irradiated with microwaves at 10 kW for 1 min to obtain platinum nitrogen-doped graphene.

[0092] Depend on Figure 1 As can be seen, the nitrogen-doped graphene provided in this embodiment is uniformly loaded with nanoscale platinum metal nanoparticles on its surface, and the size of the platinum metal nanoparticles is less than 10 nm. The particles are independent of each other and do not agglomerate. Figure 2 Figures 1 and 2 show the EDS energy dispersive spectroscopy (EDS) spectra. Figure 1a shows the microstructure of platinum-doped graphene, and Figure 2b shows the EDS surface scan composition distribution of platinum under the corresponding microstructure. Comparing Figures 1 and 2b reveals that platinum nanoparticles are uniformly distributed on the surface of the nitrogen-doped graphene matrix. Figure 3 XPS elemental analysis showed that the nitrogen doping content in the platinum-loaded nitrogen-doped graphene prepared in this embodiment was 4.12 wt%, and the platinum loading was 36.61 wt%. The ORR performance of the platinum-loaded nitrogen-doped graphene provided in this embodiment is as follows: Figure 9 As shown.

[0093] Example 2

[0094] The preparation method of Example 2 is basically the same as that of Example 1, except for the mass ratio of platinum atoms in chloroplatinic acid hexahydrate to carbon atoms in graphene oxide; the specific steps are as follows:

[0095] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 40 at%) and disperse it in 50 mL of deionized water to obtain a graphene oxide dispersion. Weigh 120 mg of chloroplatinic acid hexahydrate and disperse it in 30 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the graphene oxide dispersion and stir until homogeneous to obtain a graphene oxide-chloroplatinic acid mixture.

[0096] 2) Add the graphene oxide-chloroplatinic acid mixture obtained in step 1) into a 200 mL hydrothermal reactor and hydrothermally react at 120 °C for 30 min. After hydrothermal reaction, filter, wash, and freeze dry to obtain graphene oxide-chloroplatinic acid composite powder.

[0097] 3) The graphene oxide-chloroplatinic acid composite powder obtained in step 2) was mixed with 2 mL of ammonia water and ball-milled at 300 rpm for 40 min. After ball milling, the powder was washed and dried to obtain amino-modified graphene oxide-chloroplatinic acid composite powder. Under an argon protective atmosphere, the amino-modified graphene oxide-chloroplatinic acid composite powder was placed in the reaction chamber of a microwave reactor and irradiated with microwaves at 10 kW for 1 min to obtain platinum nitrogen-doped graphene.

[0098] through Figure 4 The XPS elemental analysis results show that the nitrogen doping content in the platinum-loaded nitrogen-doped graphene prepared in this embodiment is 3.81 wt%, and the platinum loading is 19.52 wt%.

[0099] Example 3

[0100] The preparation method of Example 3 is basically the same as that of Example 1, except for the mass ratio of carbon atoms to nitrogen atoms in ammonia water in the graphene oxide-chloroplatinic acid composite powder. The specific steps are as follows:

[0101] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 40 at%) and disperse it in 50 mL of deionized water to obtain a graphene oxide dispersion. Weigh 240 mg of chloroplatinic acid hexahydrate and disperse it in 60 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the graphene oxide dispersion and stir until homogeneous to obtain a graphene oxide-chloroplatinic acid mixture.

[0102] 2) Add the graphene oxide-chloroplatinic acid mixture obtained in step 1) into a 200 mL hydrothermal reactor and hydrothermally react at 120 °C for 40 min. After hydrothermal reaction, filter, wash, and freeze dry to obtain graphene oxide-chloroplatinic acid composite powder.

[0103] 3) The graphene oxide-chloroplatinic acid composite powder obtained in step 2) was mixed with 10 mL of ammonia water and ball-milled at 500 rpm for 40 min. After ball milling, the powder was washed and dried to obtain amino-modified graphene oxide-chloroplatinic acid composite powder. Under an argon protective atmosphere, the amino-modified graphene oxide-chloroplatinic acid composite powder was placed in the reaction chamber of a microwave reactor and irradiated with microwaves at 10 kW for 1 min to obtain platinum nitrogen-doped graphene. Figure 5 The XPS elemental analysis results show that the nitrogen doping content in the platinum-loaded nitrogen-doped graphene prepared in this embodiment is 8.17 wt%, and the platinum loading is 35.85 wt%.

[0104] Example 4

[0105] The preparation method of Example 4 is basically the same as that of Example 1, except for the microwave irradiation power; the specific steps are as follows:

[0106] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 35 at%) and disperse it in 50 mL of deionized water to obtain a graphene oxide dispersion. Weigh 240 mg of chloroplatinic acid hexahydrate and disperse it in 60 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the graphene oxide dispersion and stir until homogeneous to obtain a graphene oxide-chloroplatinic acid mixture.

[0107] 2) Add the graphene oxide-chloroplatinic acid mixture obtained in step 1) into a 200 mL hydrothermal reactor and hydrothermally react at 120 °C for 40 min. After hydrothermal reaction, filter, wash, and freeze dry to obtain graphene oxide-chloroplatinic acid composite powder.

[0108] 3) The graphene oxide-chloroplatinic acid composite powder obtained in step 2) was mixed with 2 mL of ammonia water and ball-milled at 300 rpm for 40 min. After ball milling, the powder was washed and dried to obtain amino-modified graphene oxide-chloroplatinic acid composite powder. Under a nitrogen protective atmosphere, the amino-modified graphene oxide-chloroplatinic acid composite powder was placed in the reaction chamber of a microwave reactor and irradiated with microwaves at 6 kW for 1 min to obtain platinum nitrogen-doped graphene. Figure 6 The XPS elemental analysis results show that the nitrogen doping content in the platinum-loaded nitrogen-doped graphene prepared in this embodiment is 3.57 wt%, and the platinum loading is 28.31 wt%.

[0109] Example 5

[0110] The preparation method of Example 5 is basically the same as that of Example 1, except for the microwave irradiation time; the specific steps are as follows:

[0111] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 35 at%) and disperse it in 50 mL of deionized water to obtain a graphene oxide dispersion. Weigh 240 mg of chloroplatinic acid hexahydrate and disperse it in 60 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the graphene oxide dispersion and stir until homogeneous to obtain a graphene oxide-chloroplatinic acid mixture.

[0112] 2) Add the graphene oxide-chloroplatinic acid mixture obtained in step 1) into a 200 mL hydrothermal reactor and hydrothermally react at 120 °C for 40 min. After hydrothermal reaction, filter, wash, and freeze dry to obtain graphene oxide-chloroplatinic acid composite powder.

[0113] 3) The graphene oxide-chloroplatinic acid composite powder obtained in step 2) was mixed with 2 mL of ammonia water and ball-milled at 300 rpm for 40 min. After ball milling, the powder was washed and dried to obtain amino-modified graphene oxide-chloroplatinic acid composite powder. Under a nitrogen protective atmosphere, the amino-modified graphene oxide-chloroplatinic acid composite powder was placed in the reaction chamber of a microwave reactor and irradiated with microwaves at 10 kW for 3 min to obtain platinum-nitrogen-doped graphene. Figure 7 The XPS elemental analysis results show that the nitrogen doping content in the platinum-loaded nitrogen-doped graphene prepared in this embodiment is 3.61 wt%, and the platinum loading is 27.66 wt%.

[0114] Comparative Example 1

[0115] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that nitrogen doping was not performed. The specific steps are as follows:

[0116] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 40 at%) and disperse it in 50 mL of deionized water to obtain a graphene oxide dispersion. Weigh 240 mg of chloroplatinic acid hexahydrate and disperse it in 60 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the graphene oxide dispersion and stir until homogeneous to obtain a graphene oxide-chloroplatinic acid mixture.

[0117] 2) Add the graphene oxide-chloroplatinic acid mixture obtained in step 1) into a 200 mL hydrothermal reactor and hydrothermally react at 120 °C for 40 min. After hydrothermal reaction, filter, wash and dry to obtain graphene oxide-chloroplatinic acid composite powder.

[0118] 3) Under an Ar protective gas atmosphere, the graphene oxide-chloroplatinic acid composite powder obtained in step 2) was placed into the reaction chamber of a microwave reactor and irradiated with microwaves at 10 kW for 1 min to obtain platinum-loaded graphene. The XPS elemental analysis and ORR catalytic performance diagrams of the platinum-loaded graphene prepared in this comparative example are shown below. Figure 8 and Figure 9 As shown. (The sentence is incomplete and requires more context.) Figure 8 The XPS elemental analysis results show that the loading of platinum nanoparticles in the platinum-loaded graphene prepared in this comparative example is 25.07 wt%. The loading of platinum nanoparticles in the platinum-loaded graphene without nitrogen addition is correspondingly reduced, and the oxygen reduction catalytic performance of the catalyst is reduced due to the lack of nitrogen atom synergistic effect.

[0119] Comparative Example 2

[0120] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that nitrogen-doped graphene is prepared first, and then platinum nanoparticles are loaded onto it. The specific steps are as follows:

[0121] 1) Weigh 200 mg of graphene oxide (2 layers, oxygen content 40 at%) and mix it with 2 mL of ammonia water. Then, ball mill the mixture at 300 rpm for 40 min. After ball milling, wash and dry the mixture to obtain amino-based graphene powder.

[0122] 2) Disperse the aminated graphene powder obtained in step 1) in 50 mL of deionized water to obtain an aminated graphene dispersion. Weigh 240 mg of chloroplatinic acid hexahydrate and disperse it in 60 mL of ethylene glycol to obtain a chloroplatinic acid solution. Slowly add the chloroplatinic acid solution to the aminated graphene dispersion and stir until homogeneous to obtain an aminated graphene-chloroplatinic acid mixture.

[0123] 3) The mixture of aminographene-chloroplatinic acid obtained in step 2) was added to a 200 mL hydrothermal reactor and hydrothermally reacted at 120 °C for 40 min. After hydrothermal reaction, the mixture was filtered, washed, and freeze-dried to obtain aminographene-chloroplatinic acid composite powder. Under an argon protective atmosphere, the aminographene-chloroplatinic acid composite powder was placed in the reaction chamber of a microwave reactor and irradiated with microwaves at 10 kW for 1 min to obtain platinum nitrogen-doped graphene.

[0124] through Figure 10 XPS elemental analysis showed that the nitrogen doping content in the platinum-loaded nitrogen-doped graphene prepared in this comparative example was 5.32 wt%, and the platinum loading was 15.27 wt%. Figure 11 The TEM microstructure images shown indicate that prior nitrogen doping affects the subsequent loading of platinum nanoparticles, significantly reducing the dispersion of platinum nanoparticles in the matrix and thus impacting the oxygen reduction catalytic performance of the catalyst. The ORR catalytic performance of platinum-nitrogen-doped graphene provided in this comparative example is shown in the figure below. Figure 9 As shown.

[0125] The specific steps for ORR catalytic performance testing are as follows:

[0126] 4 mg each of the graphene powders prepared in Example 1 and Comparative Examples 1-2 were dispersed in 50 μL of 5% naphthol solution in 2 mL of isopropanol to prepare electrode solutions. 8 μL of the electrode solution was then dropped onto a surface with an area of ​​0.196 cm². 2 The platinum electrode surface was naturally dried and used as the oxygen electrode. Oxygen reduction catalysis was performed in an oxygen-saturated three-electrode system using 0.5M dilute sulfuric acid solution as the electrolyte, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode.

[0127] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A method for preparing platinum-nitrogen-doped graphene, characterized in that, Includes the following steps: Graphene oxide, platinum salt, and solvent are mixed to form a mixture, which is then subjected to a hydrothermal reaction to prepare graphene oxide-platinum salt composite powder. The graphene oxide-platinum salt composite powder was mixed with an amino compound and ball-milled to prepare an amino-modified graphene oxide-platinum salt composite powder; and Platinum-nitrogen-doped graphene was prepared by microwave irradiation of the amino-modified graphene oxide-platinum salt composite powder. The amino compound includes ammonia and / or urea; In the prepared platinum-nitrogen-doped graphene, the particle size of the loaded platinum metal is 2 nm to 10 nm.

2. The preparation method according to claim 1, characterized in that, The platinum salts include chloroplatinic acid and / or platinum acetate.

3. The preparation method according to claim 1, characterized in that, The graphene oxide has 1 to 10 layers and an oxygen content of 30 at% to 60 at%.

4. The preparation method according to claim 1, characterized in that, The mass ratio of carbon atoms in the graphene oxide to platinum atoms in the platinum salt is (0.5~3):

1.

5. The preparation method according to claim 4, characterized in that, The mass ratio of carbon atoms in the graphene oxide-platinum salt composite powder to nitrogen atoms in the amino compound is (1~10):

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The hydrothermal reaction is carried out at a temperature of 80℃ to 120℃ for a time of 0.5 h to 3 h.

7. The preparation method according to any one of claims 1 to 5, characterized in that, The microwave irradiation power is 1 kW to 15 kW, and the duration is 5 s to 300 s.

8. The preparation method according to any one of claims 1 to 5, characterized in that, The ball mill operates at a speed of 200 rpm to 500 rpm for a time of 0.5 h to 3 h.

9. The preparation method according to any one of claims 1 to 5, characterized in that, The method for forming the mixture includes: The graphene oxide is dispersed in water to form a graphene oxide dispersion. The platinum salt is dissolved in an organic solvent to form a platinum salt solution; and The dispersion is mixed with the platinum salt solution to form the mixture.

10. The preparation method according to claim 9, characterized in that, The organic solvents include ethanol and / or ethylene glycol.

11. Platinum-nitrogen-doped graphene prepared by the preparation method according to any one of claims 1 to 10.

12. The application of platinum-nitrogen-doped graphene as described in claim 11 as a fuel cell catalyst.

13. A membrane electrode, characterized in that, It includes a proton exchange membrane and a catalyst layer disposed adjacent to the proton exchange membrane, wherein the catalyst layer includes platinum-nitrogen-doped graphene as described in claim 11.

14. A proton exchange membrane fuel cell, characterized in that, Includes the membrane electrode as described in claim 13.

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