Functionalized Graphene-Supported Pt-Based Alloy Catalysts and Their Preparation Methods and Applications

Abstract

This application relates to a functionalized graphene-supported Pt-based alloy catalyst, a preparation method thereof, and an application thereof. The preparation method comprises the following steps: mixing a carbon material loaded with a first metal and graphene to obtain a mixture; in the presence of a reducing gas and a solvent, causing the mixture and a metal salt of a second metal to undergo a reduction reaction, and taking the solid-phase substance after the reduction reaction; in the presence of an inert gas and a solvent, causing the solid-phase substance after the reduction reaction and a Pt salt to undergo a metal displacement reaction; taking the solid-phase substance after the displacement reaction and mixing it with an organic acid, and calcining in the presence of an inert gas. The preparation method provided by this application improves the catalytic performance and stability of the functionalized graphene-supported Pt-based alloy catalyst in the ORR in an acidic medium, and is more conducive to its application in proton exchange membrane fuel cells.

Description

Technical Field

[0001] The present application relates to the technical field of chemical catalytic materials, and particularly relates to a Pt-based alloy catalyst supported by functionalized graphene, a preparation method thereof, and an application thereof. Background Art

[0002] With the reduction of non-renewable fossil fuels, the global energy crisis has gradually intensified. As one of the new clean energies, proton exchange membrane fuel cells (PEMFCs) have broad development prospects. As the core electrochemical reaction of PEMFCs, the oxygen reduction reaction (ORR), the activity of the catalyst is one of the most critical factors restricting the performance of ORR and the application of PEMFCs. In addition to Pt-based noble metal catalysts, people have devoted more energy to seeking catalysts with lower costs and higher performances, mainly divided into three categories: Pt-based alloys, transition metal oxides, and non-metal carbon materials.

[0003] At present, Pt-based alloy nanomaterials are the only catalysts used in PEMFCs in acidic media due to their excellent ORR catalytic activity. Generally speaking, Pt-based alloy catalysts need to be supported on a carbon carrier to exhibit better performance. The main carbon carriers include carbon black, carbon nanotubes, graphene, etc. In recent years, graphene has become one of the most excellent catalyst carriers due to its excellent mechanical properties, thermodynamic properties, good electrical conductivity, electrochemical properties, anti-electrochemical corrosion properties, and large specific surface area. With the continuous in-depth research, functionalized graphene, that is, introducing active functional groups on the surface of graphene, plays a promoting role in providing more active sites and improving the adhesion and stability of Pt alloys, such as nitrogen-doped graphene, reduced graphene oxide, etc. Therefore, the Pt-based alloy catalyst supported by functionalized graphene is one of the new catalysts with lower costs and relatively excellent performances.

[0004] The traditional preparation of functionalized graphene-supported Pt-based alloy catalysts mainly follows the following steps: (1) functionalizing graphene, such as introducing functional groups on graphene through oxidants such as KMnO4, H2O2, O3 at ultra-high temperature and ultra-long reaction time, and filtering and washing to remove excess oxidants; (2) mixing functionalized graphene, Pt salt, and other metal salts, adding a reducing agent to reduce metal ions to obtain metal elements, such as strong reducing agents NaBH4, NH3, N2H4, hydrazine hydrate, weak reducing agents such as ascorbic acid, vitamin C, citric acid, ethylene glycol, etc., to obtain a precursor (hydroxide precipitate) under an alkaline pH environment; (3) finally calcining in an inert atmosphere to obtain the final functionalized graphene-supported Pt-based alloy catalyst. It can be seen that the traditional preparation method is generally to react functionalized graphene with metal salts to obtain catalyst precursors. In the process of reducing metal salts to obtain metal elements, the added reducing agent will also reduce some of the functional groups of graphene (-O-, -OH, -COOH, etc.), and the effect of graphene functionalization will be weakened. At the same time, the complete structure and conductivity of graphene will be slightly damaged, which has an adverse effect on ORR performance. Moreover, the reduction environment of Pt alloy is generally an alkaline environment. The catalyst prepared in this environment is not conducive to proton transport during the operation of PEMFC.

[0005] Therefore, finding a catalyst preparation method that is conducive to proton transport and retains the complete structure of functionalized graphene is crucial to improving ORR catalytic activity and PEMFC performance. Summary of the invention

[0006] Based on this, it is necessary to provide a new method for preparing functionalized graphene-supported Pt-based alloy catalysts to improve their catalytic performance and stability in acidic medium ORR.

[0007] In one aspect of the present application, a method for preparing a functionalized graphene-supported Pt-based alloy catalyst is provided, which comprises the following steps:

[0008] mixing a carbon material loaded with a first metal and graphene to obtain a mixture;

[0009] In the presence of a reducing gas and a solvent, causing the mixture and the metal salt of the second metal to undergo a reduction reaction, and obtaining a solid phase substance after the reduction reaction;

[0010] In the presence of an inert gas and a solvent, allowing the solid phase material after the reduction reaction to undergo a metal replacement reaction with a Pt salt;

[0011] The solid phase material after the replacement reaction is mixed with an organic acid and calcined in the presence of an inert gas;

[0012] Among them, the metal activity of the first metal is weaker than that of Pt, the metal activity of the second metal is stronger than that of Pt, and each step in the preparation method is carried out in a non-alkaline environment.

[0013] In some embodiments, the first metal includes one or more of Pd, Au, Rh, Ru, and Ir.

[0014] In some embodiments, the second metal includes one or more of Cu, Fe, Co, Ni, and Zn.

[0015] In some embodiments, the molar ratio of metal ions in the metal salts of the first metal and the second metal is (2-5):1.

[0016] In some embodiments, the molar ratio of metal ions in the metal salt of the second metal to Pt ions in the Pt salt is (0.5-1):1.

[0017] In some embodiments, the temperature of the metal displacement reaction is 50°C to 80°C, and the time of the metal displacement reaction is 5h to 8h.

[0018] In some embodiments, the Pt salt is added dropwise to the reaction system of the metal displacement reaction in the form of a salt solution, wherein the concentration of the Pt salt is 1 mmol / L to 8 mmol / L, and the dropping rate of the Pt salt solution is 0.5 ml / min to 2 ml / min.

[0019] In some embodiments, the organic acid includes one or more of acetic acid, propionic acid, succinic acid, tartaric acid, malic acid, citric acid, and oxalic acid.

[0020] In some embodiments, the mass ratio of the solid-phase substance after the displacement reaction to the organic acid is 1:(0.5-1).

[0021] In some embodiments, the temperature of the calcination is 200°C to 400°C, and the time of the calcination is 30 min to 120 min.

[0022] On the other hand, the present application provides a Pt-based alloy catalyst supported on functionalized graphene prepared by the above preparation method.

[0023] On another aspect, the present application further provides the application of the above catalyst in the ORR reaction in an acidic medium and a proton exchange membrane fuel cell.

[0024] The present application provides a new preparation idea and method, which improves the catalytic performance and stability of the Pt-based alloy catalyst supported on functionalized graphene in the ORR in acidic media, and is beneficial to be applied in proton exchange membrane fuel cells. Compared with the prior art, the present application has at least the following beneficial effects:

[0025] (1) For the preparation method provided by the present application, there is no need to use alkaline reagents to obtain the Pt-based alloy. Therefore, no alkaline reagents appear in the whole preparation process of the preparation method provided by the present application, which ensures the preparation of the catalyst in a non-alkaline environment, is beneficial to improving the proton transport ability of the catalyst and the ORR activity in acidic media, and is suitable for use as a cathode catalyst in PEMFC.

[0026] (2) For the preparation method provided by the present application, the step of graphene functionalization is placed at the last step of the whole preparation process, which ensures that the necessary groups can be fully introduced onto the graphene without being affected by the reducing agent to reduce the functionalization effect, maintains the structural integrity and conductivity of the graphene, and at the same time avoids the formation of oxides by metal ions affected by oxygen-containing functional groups, which is beneficial to improving the ORR catalytic activity and stability.

[0027] (3) For the preparation method provided by the present application, there are no redundant oxidants or reducing agents in the whole preparation process, so there is no need to remove them. The separation means applied can only involve centrifugal separation and does not involve cumbersome steps such as filtration and washing, which simplifies the preparation process. Description of the Drawings

[0028] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0029] Figure 1 TEM photograph of the catalyst prepared in Example 1;

[0030] Figure 2 CV data curve of the catalyst prepared in Example 1 before and after 1000 ORR test cycles;

[0031] Figure 3 CV data curve of the catalyst prepared in Comparative Example 1 before and after 1000 ORR test cycles;

[0032] Figure 4 LSV comparison curve of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2. Detailed Embodiments

[0033] To facilitate the understanding of this application, the following will provide a more comprehensive description of this application with reference to the relevant accompanying drawings. The preferred embodiments of this application are given in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of this application more thorough and comprehensive.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application in this specification are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0035] In this document, among the technically characterized features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0036] In this document, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0037] In this document, regarding the units of data ranges, if the unit is only attached after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 0.3~0.5m / s means that the units of the left endpoint "0.3" and the right endpoint "0.5" are both m / s (meters per second).

[0038] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each separately disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0039] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0040] The term "Pd / C" refers to a carbon material loaded with Pd nanoparticles. Pd / C in this application can be obtained commercially.

[0041] The term "high-purity graphene" refers to graphene without grafting of any functional groups.

[0042] On the one hand, this application provides a method for preparing a Pt-based alloy catalyst supported on functionalized graphene, including the following steps:

[0043] (a) Mix a carbon material loaded with a first metal and graphene to obtain a mixture;

[0044] (b) In the presence of a reducing gas and a solvent, carry out a reduction reaction between the mixture and a metal salt of a second metal, and take the solid-phase substance after the reduction reaction;

[0045] (c) In the presence of an inert gas and a solvent, carry out a metal displacement reaction between the solid-phase substance after the reduction reaction and a Pt salt;

[0046] (d) Mix the solid-phase substance after the displacement reaction with an organic acid and calcine in the presence of an inert gas;

[0047] Among them, the metal activity of the first metal is weaker than that of Pt, and the metal activity of the second metal is stronger than that of Pt. All steps in this preparation method are carried out in a non-basic environment.

[0048] In some embodiments, the first metal includes one or more of Pd, Au, Rh, Ru and Ir. In some preferred embodiments, the first metal is Pd.

[0049] In some embodiments, the second metal includes one or more of Cu, Fe, Co, Ni and Zn. In some preferred embodiments, the second metal is Cu.

[0050] In some embodiments, in the graphene loaded with a first metal and a second metal, the molar ratio of metal ions in the metal salts of the first metal and the second metal is (2-5):1. Understandably, the molar ratio of metal ions in the metal salts of the first metal and the second metal may include but is not limited to 2:1, 3:1, 4:1, 5:1.

[0051] In the carbon material loaded with the first metal, the first metal exists in the form of nanoparticles. For example, Pd / C. The metal salt of the second metal can be any soluble salt that provides the second metal ions in the presence of a solvent. In some specific embodiments, the second metal is Cu, and the metal salt of the second metal can be CuCl2, Cu(NO3)2 or CuSO4, and the solvent is water or a mixed solvent of water and alcohol, and the alcohol can be methanol or ethanol.

[0052] In some specific embodiments, the carbon material loaded with the first metal nanoparticles is Pd / C, and the metal salt of the second metal is a Cu salt. Preferably, the mass fraction of Pd in Pd / C is 20% - 60%.

[0053] The method of mixing the carbon material loaded with the first metal and graphene in step (a) can be any conventional method, such as mechanical stirring, solution method, etc.

[0054] The method of taking the solid-phase substance after the reduction reaction in step (b) can be any method well-known to those skilled in the art, such as centrifugation, filtration, etc. After obtaining the solid-phase substance, it is preferably dried. The drying method can be arbitrarily selected from the conventional methods in the art, such as natural air drying, oven drying, vacuum drying or freeze drying.

[0055] In some specific embodiments, steps (a) and (b) are:

[0056] (a) Ultrasonicating Pd / C and graphene in a water-alcohol mixed solution sufficiently to form a suspension;

[0057] (b) Continuously stirring the suspension in an H2 atmosphere, then adding an aqueous solution of Cu salt, stirring in an H2 atmosphere, and centrifuging to separate the solid-phase substance.

[0058] Preferably, the mass fraction of Pd in Pd / C is 20% - 60%, and the concentration of the aqueous solution of Cu salt can be 1 mmol / L - 8 mmol / L.

[0059] Preferably, the volume ratio of the water-alcohol mixed solution is water:ethanol = 1:1 - 2:1.

[0060] Preferably, the ultrasonic time is 0.5 - 3 h.

[0061] Preferably, the suspension is stirred for 0.5 to 4 h under an H2 atmosphere. After adding the Cu salt aqueous solution, it is stirred for 4 to 12 h under an H2 atmosphere.

[0062] In step (c), the Pt salt can dissociate into Pt ions in the solvent, including but not limited to H2PtCl4, K2PtCl4, Na2PtCl4, and their combinations. The solvent can be water or a mixed solvent of water and alcohol, and the alcohol can be methanol or ethanol.

[0063] In some embodiments, the molar ratio of the metal ions in the metal salt of the second metal to the Pt ions in the Pt salt is (0.5 to 1):1.

[0064] In some preferred embodiments, the Pt salt is added dropwise to the reaction system of the metal displacement reaction in the form of a salt solution. Preferably, the concentration of the Pt salt is 1 mmol / L to 8 mmol / L, and the dropping rate of the Pt salt solution is 0.5 ml / min to 2 ml / min.

[0065] In some preferred embodiments, the solid-phase material after the reduction reaction can be first dispersed in a solvent to form a homogeneous dispersion, and then the Pt salt is added to the dispersion.

[0066] In some embodiments, the temperature of the metal displacement reaction is 50°C to 80°C, and the time of the metal displacement reaction is 5 h to 8 h. Preferably, the heating rate during the metal displacement reaction is 3 to 6°C / min.

[0067] The method for taking the solid-phase material after the displacement reaction in step (d) can be any method known to those skilled in the art, such as centrifugation, filtration, etc. After obtaining the solid-phase material, it is preferably dried. The drying method can be arbitrarily selected from conventional methods in the art, such as natural air drying, oven drying, vacuum drying, or freeze drying.

[0068] In some specific embodiments, the solid-phase material is obtained by centrifugal separation. The rotation speed of the centrifugal separation can be 10000 to 20000 rpm, and the centrifugation time can be 10 to 40 min.

[0069] The organic acid undergoes thermal decomposition under the calcination conditions. The thermal decomposition products are grafted onto the graphene, introducing functional groups such as hydroxyl groups and carboxylic acid groups into the original graphene. While functionalizing, the complete structure and good conductivity of the graphene are retained. The functionalized graphene as a carrier active site can make the loaded metal particles adhere more stably.

[0070] The organic acid can include but not limited to acetic acid, propionic acid, succinic acid, tartaric acid, malic acid, citric acid, oxalic acid, and their combinations. In some preferred embodiments, the organic acid is citric acid.

[0071] The graphene used as a raw material in this application can be high-purity graphene, reduced graphene oxide (rGO), or a combination thereof. The high-purity graphene can be purchased from Suzhou Kaifa New Materials Technology Co., Ltd., with the CAS number BKMK2001.

[0072] The thickness of the graphene used as a raw material in this application can be 1 - 3 nm, the size can be 2 - 10 μm, the number of layers can be 3 - 10, and the specific surface area can be 250 - 400 m 2 / g.

[0073] In some embodiments, the mass ratio of the solid-phase substance after the displacement reaction to the organic acid can be 1:(0.5 - 1).

[0074] Understandably, in order to make the solid-phase substance after the displacement reaction and the organic acid more uniform, in some embodiments, the organic acid can be configured into an aqueous solution of the organic acid and then mixed with the solid-phase substance after the displacement reaction, and mixed evenly by ultrasonic waves. Preferably, the concentration of the aqueous solution of the organic acid is 5 - 8 mg / mL. Understandably, due to the presence of moisture, before calcination, the moisture needs to be removed by drying means, and the drying method can be arbitrarily selected from conventional methods in the art, such as natural air drying, oven drying, vacuum drying, or freeze drying.

[0075] In some embodiments, the calcination temperature can be 200°C - 400°C, and the calcination time can be 30 min - 120 min.

[0076] In another aspect of this application, a Pt-based alloy catalyst supported by functionalized graphene prepared by any of the above preparation methods is provided.

[0077] In yet another aspect of this application, the application of the above catalyst in the ORR reaction in an acidic medium and a proton exchange membrane fuel cell is also provided, for example, as a cathode catalyst of a proton exchange membrane fuel cell.

[0078] The following are specific examples. The purpose is to further elaborate on this application to help those skilled in the art and researchers further understand this application. The relevant technical conditions do not constitute any limitation to this application. Any form of modification within the scope of the claims of this application is within the protection scope of the claims of this application.

[0079] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods. The instruments are all conventional selections in the art. The experimental methods without specific conditions noted in the examples are carried out according to conventional conditions, such as the conditions described in the literature, books, or the methods recommended by the manufacturers.

[0080] The meanings of the following English abbreviations are as follows:

[0081] Pd / C represents activated carbon loaded with palladium nanoparticles;

[0082] Cu-Pd / G represents graphene loaded with copper nanoparticles and palladium nanoparticles;

[0083] PdPt / G represents graphene loaded with palladium nanoparticles and platinum nanoparticles;

[0084] PdPt / CA-G represents functionalized graphene loaded with palladium nanoparticles and platinum nanoparticles, and the functional groups in the graphene are provided by the thermal decomposition of citric acid;

[0085] CA-G represents functionalized graphene, and the functional groups in the graphene are provided by the thermal decomposition of citric acid;

[0086] Cu-Pd / CA-G represents functionalized graphene loaded with copper nanoparticles and palladium nanoparticles, and the functional groups in the graphene are provided by the thermal decomposition of citric acid.

[0087] Example 1

[0088] (1) 0.265 g of Pd / C and 0.2 g of graphene were ultrasonically treated in 50 ml of a water-alcohol mixed solution (water:ethanol = 1:1) for 1 h to form a homogeneous suspension. The suspension was continuously stirred in a H2 atmosphere for 2 h, and then 50 ml of a 5 mmol / L CuCl2 solution was added. The mixture was stirred in a H2 atmosphere for 6 h, centrifuged at 20000 rpm for 30 min, and the nanoparticles Cu-Pd / G were obtained.

[0089] (2) The obtained Cu-Pd / G was redispersed in 50 ml of a water-alcohol mixed solution (water:ethanol = 1:1), and 50 ml of a 5 mmol / L K2PtCl4 solution was dropped in at a rate of 1 ml / min to undergo a metal transfer displacement reaction with Cu. The reaction temperature was 60 °C, the heating rate was 5 °C / min, the reaction was carried out in a N2 atmosphere for 6 h, centrifuged at 20000 rpm for 30 min, and dried in an oven to obtain the precursor PdPt / G.

[0090] (3) 100 mg of citric acid (CA) and 15 ml of water were prepared into an aqueous solution, and then 100 mg of PdPt / G was added and mixed. After ultrasonic homogenization, it was dried in vacuo and calcined at 300 °C for 60 min in an Ar atmosphere, and then cooled to room temperature to obtain the PdPt / CA-G catalyst.

[0091] Example 2

[0092] The preparation method was basically the same as that of Example 1, except that CuCl2 was replaced by FeCl3 and K2PtCl4 was replaced by Na2PtCl4.

[0093] Comparative Example 1

[0094] First, functionalize graphene with CA to obtain CA-G, and then perform alloying of metals and load them on CA-G. The specific steps are as follows:

[0095] (1) Prepare an aqueous solution of 100 mg of citric acid (CA) and 15 ml of water, then add 100 mg of graphene and mix them evenly by ultrasonic treatment. After vacuum drying, calcine at 300 °C for 60 min in an Ar atmosphere, and cool to room temperature to obtain the functionalized graphene support CA-G.

[0096] (2) Ultrasonically treat 0.265 g of Pd / C and 0.2 g of CA-G in 50 ml of a water-alcohol mixed solution (water:ethanol = 1:1) for 1 h to form a uniform suspension. Continuously stir the suspension in a H2 atmosphere for 2 h, then add 50 ml of a 5 mmol / L CuCl2 solution and stir in a H2 atmosphere for 6 h. Centrifuge at 20000 rpm for 30 min to obtain the nanoparticles Cu-Pd / CA-G.

[0097] (3) Redisperse the obtained Cu-Pd / CA-G in 50 ml of a water-alcohol mixed solution (water:ethanol = 1:1), and dropwise add 50 ml of a 5 mmol / L K2PtCl4 solution at a rate of 1 ml / min to carry out a metal transfer displacement reaction with Cu. The reaction temperature is 60 °C, and the heating rate is 5 °C / min. React in a N2 atmosphere for 6 h, centrifuge at 20000 rpm for 30 min, and dry in an oven to obtain the final catalyst, labeled as PdPt / CA-G-1.

[0098] Comparative Example 2

[0099] Prepare a PdPt alloy catalyst supported on functionalized graphene under an alkaline environment. The specific steps are as follows:

[0100] (1) Ultrasonically treat 0.265 g of Pd / C and 0.2 g of graphene in 50 ml of a water-alcohol mixed solution (water:ethanol = 1:1) for 1 h to form a uniform suspension, continuously stir for 2 h, and then dropwise add 50 ml of a 5 mmol / L K2PtCl4 solution at a rate of 1 ml / min and stir thoroughly for 1 h.

[0101] (2) Dropwise add 300 ml of a 0.3 mol / L NaBH4 solution to the mixed dispersion in (1), stir for 6 h to fully react. The precipitate is washed and filtered three times and dried in an oven to obtain the precursor PdPt / G.

[0102] (3) Prepare an aqueous solution with 100 mg of citric acid (CA) and 15 ml of water, then add 100 mg of PdPt / G and mix well by ultrasonic treatment. After vacuum drying, calcine at 300 °C for 60 min in an Ar atmosphere and cool to room temperature to obtain the final catalyst, labeled as PdPt / CA-G-2.

[0103] Perform morphology and catalytic performance tests on the materials prepared in Examples 1-2 and Comparative Examples 1-2.

[0104] Among them, the test conditions or test standards for each performance test item are as follows:

[0105] 1. Morphology

[0106] Use a scanning electron microscope and a transmission electron microscope to study the morphology of the materials.

[0107] 2. Catalytic performance

[0108] ORR test: In an O2-saturated 0.5 mol / L H2SO4 medium, the catalyst loading is 80 μg / cm 2 , CV voltage scanning range: -0.2 V to 1.0 V vs. Ag / AgCl, scanning rate 50 mV / s, and compare 1000 cycles. LSV voltage scanning range: -0.2 V to 1.0 V vs. Ag / AgCl, scanning rate 5 mV / s, rotation speed 1600 rpm.

[0109] The results are as follows:

[0110] 1. The transmission electron microscope photograph of the catalyst prepared in Example 1 is as Figure 1 shown. It can be seen from Figure 1 that Pt and Pd in the catalyst are evenly distributed as nanoparticles on the surface of graphene. The catalyst prepared in Example 2 has similar morphological characteristics.

[0111] 2. Figure 2 Shows the CV data of the catalyst prepared in Example 1 before and after 1000 cycles of ORR test. The CV of PdPt / CA-G has no obvious attenuation, indicating that its stability and durability for ORR in acidic medium are very good. Similarly, the CV of the catalyst prepared in Example 2 also has no obvious attenuation. Figure 3 Shows the CV data of the catalyst prepared in Comparative Example 1 before and after 1000 cycles of ORR test. The CV of PdPt / CA-G-1 has obvious attenuation. By Figure 2 and Figure 3From the comparison, it can be seen that the stability of PdPt / CA-G-1 is worse than that of PdPt / CA-G. This may be because the reduction environment for preparing the PdPt alloy in Comparative Example 1 also reduced some functional groups on CA-G. As a result, the active sites of the functionalized graphene as a carrier decreased, leading to unstable attachment of the loaded PdPt particles. Moreover, the graphene structure was damaged and the conductivity decreased, thus resulting in unstable ORR performance.

[0112] 3. Figure 4 Figure 5 shows the LSV comparison curves of the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2. The half-wave potential and limiting current of PdPt / CA-G are the largest, indicating that PdPt / CA-G has the optimal ORR catalytic performance. Compared with the catalyst PdPt / CA-G-1 prepared by first functionalizing graphene and the catalyst PdPt / CA-G-2 prepared under alkaline conditions, the PdPt alloy in PdPt / CA-G has the highest activity and is also most conducive to proton transport under acidic conditions, making it the most suitable cathode catalyst for PEMFC.

[0113] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope described in this specification.

[0114] The above-described embodiments merely represent several implementation manners of the present application, which are convenient for understanding the technical solutions of the present application specifically and in detail. However, it should not be construed as a limitation on the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can be made, and these all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning, or limited experiments based on the technical solutions provided in the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the content of the appended claims, and the specification and drawings can be used to explain the content of the claims.

Claims

1. A preparation method of a functionalized graphene-supported Pt-based alloy catalyst, characterized in that, It consists of the following steps: Mix the carbon material loaded with the first metal and graphene to obtain a mixture; In the presence of a reducing gas and a solvent, carry out a reduction reaction between the mixture and the metal salt of the second metal, and take the solid-phase substance after the reduction reaction; In the presence of an inert gas and a solvent, carry out a metal displacement reaction between the solid-phase substance after the reduction reaction and the Pt salt; Take the solid-phase substance after the displacement reaction and mix it with an organic acid, and calcine it in the presence of an inert gas; Wherein, the metal activity of the first metal is weaker than that of Pt, the metal activity of the second metal is stronger than that of Pt, and each step in the preparation method is carried out in a non-basic environment.

2. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, characterized in that, The first metal includes one or more of Pd, Au, Rh, Ru, and Ir.

3. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, characterized in that, The second metal includes one or more of Cu, Fe, Co, Ni, and Zn.

4. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, characterized in that, The molar ratio of metal ions in the metal salts of the first metal and the second metal is (2 - 5):

1.

5. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 4, characterized in that, The molar ratio of metal ions in the metal salt of the second metal and Pt ions in the Pt salt is (0.5 - 1):

1.

6. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, characterized in that, The temperature of the metal displacement reaction is 50°C to 80°C, and the time of the metal displacement reaction is 5h to 8h.

7. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 6, characterized in that, The Pt salt is added dropwise to the reaction system of the metal displacement reaction in the form of a salt solution, wherein the concentration of the Pt salt is 1 mmol / L to 8 mmol / L, and the dropping rate of the Pt salt solution is 0.5 ml / min to 2 ml / min.

8. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, characterized in that, The organic acid includes one or more of acetic acid, propionic acid, succinic acid, tartaric acid, malic acid, citric acid, and oxalic acid.

9. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, wherein, The mass ratio of the solid-phase substance after the displacement reaction and the organic acid is 1:(0.5 - 1).

10. The preparation method of the functionalized graphene-supported Pt-based alloy catalyst according to claim 1, characterized in that, The temperature of the calcination is 200°C to 400°C, and the time of the calcination is 30 min to 120 min.

11. A Pt-based alloy catalyst supported on functionalized graphene prepared by the preparation method according to any one of claims 1 to 10.

12. Use of the catalyst according to claim 11 in an acidic medium ORR reaction and a proton exchange membrane fuel cell.

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