Preparation method of platinum-carbon catalyst and platinum-carbon catalyst

Abstract

The invention discloses a preparation method of a platinum-carbon catalyst and the platinum-carbon catalyst, and the method comprises the following steps: pretreating a carbon carrier to obtain a target carbon carrier; carrying out platinum loading on the target carbon carrier by adopting a platinum precursor to obtain an initial platinum-carbon catalyst; dipping the initial platinum-carbon catalyst in the amino compound solution to obtain a dipping mixture; the concentration of the amino compound solution is 0.1-10 mmol / L; carrying out ultrasonic treatment on the impregnated mixture for 20-30 minutes at room temperature to obtain an intermediate platinum-carbon catalyst; and carrying out vacuum drying on the intermediate platinum-carbon catalyst at 60-80 DEG C for 8-16 hours to obtain the platinum-carbon catalyst. The amino compound solution is used for modifying the catalyst, the interaction between platinum particles and an oxygen-containing intermediate in the oxygen reduction process is weakened, and the catalytic activity of the platinum-carbon catalyst is improved.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a method for preparing a platinum-carbon catalyst and a platinum-carbon catalyst. Background Art

[0002] Proton exchange membrane fuel cells fueled by hydrogen are expected to become the next generation of clean energy systems due to their high energy conversion efficiency, high energy density, clean and pollution-free. One of the key technologies for the development of hydrogen fuel cells is to improve the reaction kinetics of the cathode oxygen reduction reaction (ORR) and improve the high cost and poor durability of the catalyst. Currently, the ORR catalyst with the highest application value is the platinum-carbon catalyst, but it still has some shortcomings. On the one hand, the scarcity of platinum resources leads to high prices, which increases the system cost of the fuel cell; on the other hand, the platinum particles of the platinum-carbon catalyst are prone to dissolution and shedding during use, resulting in performance degradation and affecting the battery life. Therefore, how to improve the platinum utilization rate of the platinum-carbon catalyst and enhance the catalytic activity and stability is of great significance to promoting the large-scale application of fuel cells. Summary of the invention

[0003] The present application provides a method for preparing a platinum-carbon catalyst and a platinum-carbon catalyst. The catalyst is modified by using an amino compound solution, thereby weakening the interaction between platinum particles and oxygen-containing intermediates during the oxygen reduction process and improving the catalytic activity of the platinum-carbon catalyst.

[0004] In one aspect, the present application provides a method for preparing a platinum-carbon catalyst, the method comprising:

[0005] Pretreating the carbon carrier to obtain a target carbon carrier;

[0006] Using a platinum precursor to load platinum on the target carbon carrier to obtain an initial platinum-carbon catalyst;

[0007] The initial platinum-carbon catalyst is impregnated in an amino compound solution to obtain an impregnation mixture; in the impregnation mixture, the content of the initial platinum-carbon catalyst is 0.5-1.5 g / L; and the concentration of the amino compound solution is 0.1-10 mmol / L;

[0008] The impregnation mixture is subjected to ultrasonic treatment for 20-30 minutes at room temperature to obtain an intermediate platinum-carbon catalyst; the ultrasonic treatment corresponds to an ultrasonic power of 80-120 W;

[0009] The intermediate platinum-carbon catalyst is vacuum dried at 60-80° C. for 8-16 hours to obtain the platinum-carbon catalyst.

[0010] Furthermore, the use of a platinum precursor to load platinum on the target carbon carrier to obtain an initial platinum-carbon catalyst comprises:

[0011] Mixing the target carbon carrier, the platinum precursor and a solvent to obtain an initial mixture;

[0012] Stirring the initial mixture at 60-80° C. until the stirring product is in a sticky paste state, thereby obtaining an intermediate mixture;

[0013] The intermediate mixture is freeze-dried to obtain a freeze-dried product; the freeze-drying time is 12-20 hours;

[0014] The freeze-dried product is heat-treated in an atmosphere of reducing gas to obtain the initial platinum-carbon catalyst; the reducing gas is hydrogen or a hydrogen-argon mixture; the heat treatment temperature corresponding to the heat treatment is 100-400° C., and the heat treatment time is 0.5-4h.

[0015] Furthermore, the target carbon carrier, the platinum precursor and a solvent are mixed to obtain an initial mixture, comprising:

[0016] The target carbon carrier is placed in the solvent for dispersion to obtain a mixture of the target carbon carrier and the solvent; the solvent is one or more of ultrapure water and ethanol; the dispersion mass ratio of the target carbon carrier to the solvent is 1: (30-50);

[0017] The solution containing the platinum precursor is added to the mixture of the target carbon carrier and the solvent, and ultrasonic dispersion treatment is performed in an ice-water bath to obtain the initial mixture; the ultrasonic dispersion treatment time is 20-30 minutes.

[0018] Furthermore, the pretreatment of the carbon carrier to obtain the target carbon carrier comprises:

[0019] Using an oxidizing acid solution to acid-wash the carbon support to obtain an initial carbon support;

[0020] The initial carbon carrier is vacuum dried at 60-80° C. for 12-24 hours to obtain a target carbon carrier.

[0021] Furthermore, the carbon carrier is acid-washed with an oxidizing acid solution to obtain an initial carbon carrier, comprising:

[0022] The carbon carrier is mixed with the oxidizing acid solution, and stirred at room temperature-100° C. to obtain a mixture of the carbon carrier and the oxidizing acid solution; the stirring time is 1-4 hours;

[0023] The mixture of the carbon support and the oxidizing acid solution is filtered and washed with deionized water until the filtrate is neutral to obtain the initial carbon support.

[0024] Furthermore, the oxidizing acid solution is one of nitric acid solution, ammonium persulfate solution, sulfuric acid solution, and hydrogen peroxide solution; and the concentration of the oxidizing acid solution is 0.2-10 mol / L.

[0025] Furthermore, the amino compound solution is one of melamine solution, methylguanamine solution, cyanuric acid solution, and cyanuric acid solution;

[0026] The carbon carrier is one or more of XC-72, EC-300J, EC-600JD, MH-18, and BP2000.

[0027] Furthermore, the platinum loading in the platinum-carbon catalyst is 40-70%.

[0028] Furthermore, the platinum precursor is one of chloroplatinic acid, potassium chloroplatinate, tetraammineplatinum, dinitrodiammineplatinum, and hexahydroxyplatinic acid.

[0029] On the other hand, a platinum-carbon catalyst is provided, which is prepared by the above-mentioned preparation method; the surface of the target carbon carrier of the platinum-carbon catalyst includes a plurality of evenly distributed platinum particles, and the particle size of the platinum particles is 2-5 nm.

[0030] The preparation method of the platinum-carbon catalyst and the platinum-carbon catalyst provided in this application have the following technical effects:

[0031] The present application pre-treats a carbon carrier to obtain a target carbon carrier; uses a platinum precursor to load the target carbon carrier with platinum to obtain an initial platinum-carbon catalyst; impregnates the initial platinum-carbon catalyst in an amino compound solution to obtain an impregnation mixture; in the impregnation mixture, the content of the initial platinum-carbon catalyst is 0.5-1.5 g / L; the concentration of the amino compound solution is 0.1-10 mmol / L; the impregnation mixture is ultrasonically treated for 20-30 min at room temperature to obtain an intermediate platinum-carbon catalyst; the ultrasonic power corresponding to the ultrasonic treatment is 80-120 W; the intermediate platinum-carbon catalyst is vacuum dried for 8-16 h at 60-80 ° C to obtain a platinum-carbon catalyst. The present application uses an amino compound solution to modify the catalyst, which weakens the interaction between platinum particles and oxygen-containing intermediates during oxygen reduction, improves the catalytic activity of the platinum-carbon catalyst, and effectively improves the problem of poor catalyst performance at higher platinum loadings.

[0032] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions and advantages of the embodiments of this specification or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a schematic flow chart of a method for preparing a platinum-carbon catalyst provided in an embodiment of this specification;

[0035] Figure 2 is a schematic diagram of a process for preparing a target carbon carrier provided in an embodiment of this specification;

[0036] Figure 3 This is a schematic diagram of a process for pre-treating a carbon carrier provided in an embodiment of this specification;

[0037] Figure 4 It is a schematic diagram of a process for preparing an initial platinum-carbon catalyst provided in the examples of this specification;

[0038] Figure 5 is a schematic diagram of a process for obtaining an initial mixture provided in an embodiment of this specification;

[0039] Figure 6 is a transmission electron microscopy image of a melamine-modified platinum-carbon catalyst provided in the examples of this specification;

[0040] Figure 7 This is a transmission electron micrograph of a methylguanamine-modified platinum-carbon catalyst provided in the examples of this specification. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0042] The following is a preparation method of a platinum-carbon catalyst of the present application, specifically as follows Figure 1 As shown, the method may include:

[0043] S1: pretreating the carbon carrier to obtain a target carbon carrier.

[0044] Furthermore, if Figure 2As shown, the pretreatment of the carbon carrier to obtain the target carbon carrier may include:

[0045] S11: washing the carbon support with an oxidizing acid solution to obtain an initial carbon support;

[0046] S12: vacuum drying the initial carbon carrier at 60-80° C. for 12-24 hours to obtain a target carbon carrier.

[0047] In the embodiment of the present application, the carbon carrier is first pretreated by acid washing the carbon carrier with an oxidizing acid solution, and then vacuum drying is performed at 60-80°C for 12-24 hours to obtain the pretreated carbon carrier, i.e., the above-mentioned target carbon carrier, for use.

[0048] The embodiments of the present application can remove impurities by pretreating the carbon support and introduce more oxygen-containing functional groups on the surface of the carbon support, thereby enhancing the interaction between the carbon support and platinum and effectively increasing the platinum loading in the platinum-carbon catalyst.

[0049] Furthermore, if Figure 3 As shown, the step of acid washing the carbon support with an oxidizing acid solution to obtain an initial carbon support may include:

[0050] S111: mixing the carbon support and the oxidizing acid solution, and stirring the mixture at room temperature -100°C to obtain a mixture of the carbon support and the oxidizing acid solution; the stirring time is 1-4 hours;

[0051] S112: filtering the mixture of the carbon support and the oxidizing acid solution, and washing with deionized water until the filtrate is neutral, to obtain the initial carbon support.

[0052] In an embodiment of the present application, the carbon carrier is first mixed with an oxidizing acid solution and stirred at room temperature -100°C for 1-4 hours. The mixture of the carbon carrier and the oxidizing acid solution is then filtered and washed with deionized water until the filtrate is neutral. The filter cake obtained is the initial carbon carrier mentioned above. The target carbon carrier can be obtained by vacuum drying the initial carbon carrier.

[0053] In the embodiments of the present application, the mixing molar ratio of the carbon carrier to the oxidizing acid may be (4-10):1, and the specific mixing ratio may be adjusted according to the acid washing process.

[0054] In the embodiment of the present application, the carbon carrier can be one or more of XC-72, EC-300J, EC-600JD, MH-18, BP2000, and the carbon carrier is used as one of the raw materials for preparing the platinum-carbon catalyst. The convenient acquisition channel can improve the convenience of the overall preparation process of the platinum-carbon catalyst.

[0055] The embodiment of the present application uses an oxidizing acid to treat the carbon carrier, which can increase the concentration of hydroxyl groups on the surface and in the pores of the carbon carrier, enhance the interaction between the carbon carrier and platinum, ensure that platinum can be evenly distributed on the surface of the carbon carrier, and avoid the problem of decreased catalytic performance of the catalyst due to platinum agglomeration, thereby improving the catalytic performance.

[0056] Furthermore, the oxidizing acid solution is one of nitric acid solution, ammonium persulfate solution, sulfuric acid solution, and hydrogen peroxide solution; and the concentration of the oxidizing acid solution is 0.2-10 mol / L.

[0057] In the embodiments of the present application, the carbon carrier is pretreated mainly by pickling with an oxidizing acid solution. The oxidizing acid solution may be one of nitric acid solution, ammonium persulfate solution, sulfuric acid solution, and hydrogen peroxide solution. The concentration of the oxidizing acid solution may be 0.2-10 mol / L. The specific selection and concentration of the oxidizing acid solution may be adjusted according to actual conditions.

[0058] The embodiments of the present application can achieve pretreatment of the carbon carrier by selecting an oxidizing acid solution of appropriate concentration to pickle the carbon carrier, effectively improve the surface properties of the carbon carrier, enhance the interaction between the carbon carrier and platinum, and increase the platinum loading on the carbon carrier.

[0059] S2: using a platinum precursor to load platinum on the target carbon carrier to obtain an initial platinum-carbon catalyst.

[0060] Furthermore, if Figure 4 As shown, the process of loading the target carbon carrier with platinum using a platinum precursor to obtain an initial platinum-carbon catalyst may include:

[0061] S21: mixing the target carbon carrier, the platinum precursor and a solvent to obtain an initial mixture;

[0062] S22: stirring the initial mixture at 60-80° C. until the stirring product is in a viscous paste state, thereby obtaining an intermediate mixture;

[0063] S23: freeze-drying the intermediate mixture to obtain a freeze-dried product; the freeze-drying time is 12-20 hours;

[0064] S24: heat-treating the freeze-dried product in an atmosphere of reducing gas to obtain the initial platinum-carbon catalyst; the reducing gas is hydrogen or a hydrogen-argon mixture; the heat treatment temperature corresponding to the heat treatment is 100-400° C., and the heat treatment time is 0.5-4h.

[0065] In the embodiment of the present application, after obtaining the target carbon carrier, it is necessary to load the target carbon carrier with platinum particles, first mix the target carbon carrier, the platinum precursor and the solvent to obtain an initial mixture, and continuously magnetically stir and impregnate the obtained initial mixture at 60-80°C until most of the liquid disappears, that is, the product of the stirring treatment is sticky and yogurt-like, and then the stirred product is placed in a freeze dryer for freeze drying, and then the freeze-dried product is placed in a crucible and heat-treated in an atmosphere of reducing gas, and the initial platinum-carbon catalyst can be obtained after the heat treatment. Among them, the freeze drying treatment time can be 12-20h, the reducing gas can be hydrogen or hydrogen-argon mixed gas (10% hydrogen-argon mixed gas), the heat treatment temperature corresponding to the heat treatment during reduction can be 100-400°C, and the heat treatment time can be 0.5-4h.

[0066] In the embodiment of the present application, when heat treatment is performed in an atmosphere of reducing gas, it may be a single heat treatment or two or more heat treatments. When multiple heat treatments are performed, the temperature and time of each heat treatment may be set to be different or the same.

[0067] In an embodiment of the present application, the above-mentioned heat treatment step may include:

[0068] The freeze-dried product is subjected to a heat treatment in a reducing gas atmosphere to obtain a heat-treated product; the temperature corresponding to the heat treatment is 100-400° C. and the time is 0.5-4 hours;

[0069] The product of the primary heat treatment is subjected to a secondary heat treatment in the atmosphere of the reducing gas to obtain an initial platinum-carbon catalyst; the temperature corresponding to the secondary heat treatment is 100-400° C. and the time is 0.5-4 hours.

[0070] In an embodiment of the present application, the above-mentioned heat treatment step may also include:

[0071] The freeze-dried product is subjected to a primary heat treatment at 150° C. for 1 hour in an atmosphere of reducing gas to obtain a primary heat-treated product;

[0072] The product of the primary heat treatment is subjected to a secondary heat treatment at 200°C-0.5h in the atmosphere of the reducing gas to obtain an initial platinum-carbon catalyst.

[0073] The embodiment of the present application adopts the impregnation method to prepare the initial platinum-carbon catalyst. The overall preparation process is simple and feasible, and can effectively avoid the agglomeration of platinum during the heat treatment process by controlling the temperature and time of the heat treatment, ensuring that the platinum can be evenly loaded on the carbon carrier, thereby improving the catalytic performance.

[0074] Furthermore, if Figure 5 As shown, the mixing of the target carbon carrier, the platinum precursor and the solvent to obtain an initial mixture may include:

[0075] S211: dispersing the target carbon carrier in the solvent to obtain a mixture of the target carbon carrier and the solvent; the solvent is one or more of ultrapure water and ethanol; the dispersion mass ratio of the target carbon carrier to the solvent is 1:(30-50);

[0076] S212: adding the solution containing the platinum precursor to the mixture of the target carbon carrier and the solvent, and performing ultrasonic dispersion treatment in an ice-water bath to obtain the initial mixture; the ultrasonic dispersion treatment time is 20-30 minutes.

[0077] In an embodiment of the present application, in order to uniformly load the platinum particles on the target carbon carrier, it is necessary to first prepare a mixed solution of the target carbon carrier and a platinum precursor. The target carbon carrier obtained by pretreatment is dispersed in a solvent, and then a solution containing a platinum precursor is added, and ultrasonic dispersion treatment is performed under an ice-water bath, and the suspension finally obtained is the above-mentioned initial mixture. Among them, the above-mentioned solvent can be one or more of ultrapure water and ethanol, the dispersion mass ratio of the target carbon carrier to the solvent can be 1: (30-50), and the ultrasonic dispersion treatment time can be 20-30min. The time of ultrasonic dispersion treatment can be appropriately adjusted according to the actual dispersion situation. If the dispersion is uneven, the ultrasonic time can be extended to obtain a more uniformly mixed initial mixture.

[0078] The embodiment of the present application obtains a uniform mixture of the target carbon carrier, the platinum precursor and the solvent, so that the platinum particles can be uniformly loaded on the target carbon carrier, thereby improving the catalytic activity of the catalyst.

[0079] Furthermore, the platinum precursor is one of chloroplatinic acid, potassium chloroplatinate, tetraammineplatinum, dinitrodiammineplatinum, and hexahydroxyplatinic acid.

[0080] In the embodiment of the present application, the concentration of the solution containing the platinum precursor can be 0.192 mol / L, and the amount of platinum loaded on the target carbon carrier can be controlled by the amount of the platinum precursor solution added. The platinum precursor can be one of chloroplatinic acid, potassium chloroplatinate, tetraammine platinum, dinitrodiammine platinum, and hexahydroxyplatinic acid.

[0081] The embodiment of the present application uses a solution containing a platinum precursor as a platinum source. The platinum loading can be regulated by adjusting the amount of solution added to achieve the preparation of platinum-carbon catalysts with different platinum loadings. The regulation method is simple and easy to implement, making the preparation process of the platinum-carbon catalyst more flexible and controllable.

[0082] S3: impregnating the initial platinum-carbon catalyst into an amino compound solution to obtain an impregnation mixture; in the impregnation mixture, the content of the initial platinum-carbon catalyst is 0.5-1.5 g / L; and the concentration of the amino compound solution is 0.1-10 mmol / L.

[0083] In the embodiment of the present application, the catalyst is modified by using an amino-containing solution, and the initial platinum-carbon catalyst prepared above is impregnated in an amino compound solution by an impregnation method, and the mass of the initial platinum-carbon catalyst corresponding to each 1L of the amino compound solution can be 0.5-1.5g, so as to ensure that the initial platinum-carbon catalyst can be fully impregnated in the amino compound solution. The concentration of the amino compound solution can be 0.1-10mmol / L.

[0084] S4: subjecting the impregnation mixture to ultrasonic treatment for 20-30 minutes at room temperature to obtain an intermediate platinum-carbon catalyst; the ultrasonic treatment corresponds to an ultrasonic power of 80-120W.

[0085] In the embodiments of the present application, an ultrasonic method can be used to fully impregnate the catalyst with the amino compound solution. If a large amount of catalyst needs to be impregnated, the ultrasonic time can be appropriately extended, and the ultrasonic power can be appropriately increased to ensure that the catalyst is fully modified.

[0086] In the embodiments of the present application, the number of ultrasonic treatments can be single or multiple times. When multiple ultrasonic treatments are performed, the parameter settings for each ultrasonic treatment can be the same or different. The ultimate goal is to ensure that the amino compound solution can fully impregnate the catalyst to achieve modification of the catalyst.

[0087] In an embodiment of the present application, the above-mentioned ultrasonic treatment step may include:

[0088] The impregnation mixture is subjected to a first ultrasound for 10 minutes at room temperature to obtain a first ultrasound product; the ultrasound power corresponding to the first ultrasound is 80-120 W;

[0089] The product of the first ultrasound was subjected to a second ultrasound for 15 minutes at room temperature to obtain an intermediate platinum-carbon catalyst; the ultrasonic power corresponding to the first ultrasound was 80-120W.

[0090] In an embodiment of the present application, the above-mentioned ultrasonic treatment step may also include:

[0091] The impregnation mixture was sonicated once for 10 min at room temperature to obtain a sonicated product;

[0092] Performing a second ultrasonic treatment on the first ultrasonic product for 15 min at room temperature to obtain a second ultrasonic product;

[0093] The secondary ultrasonic product was ultrasonicated three times for 5 min at room temperature to obtain an intermediate platinum-carbon catalyst.

[0094] S5: vacuum drying the intermediate platinum-carbon catalyst at 60-80° C. for 8-16 hours to obtain the platinum-carbon catalyst.

[0095] In the embodiment of the present application, after the catalyst is fully impregnated with the amino compound solution, a vacuum drying method can be used to dry it to obtain a final dry platinum-carbon catalyst. The vacuum drying temperature can be 60-80°C and the time can be 8-16 hours. The specific temperature and time can be adjusted according to the actual drying conditions to ensure that a dry platinum-carbon catalyst is obtained.

[0096] Furthermore, the platinum loading in the platinum-carbon catalyst is 40-70%.

[0097] In the embodiments of the present application, the platinum loading in the platinum-carbon catalyst can be regulated by adjusting the amount of platinum precursor solution added to achieve controllability of the platinum loading. For the platinum-carbon catalyst finally prepared, the actual platinum loading can be obtained by thermogravimetric analysis.

[0098] In the embodiments of the present application, the platinum loading in the platinum-carbon catalyst can be 40-70%. If the platinum loading is too high, the platinum particles will agglomerate during the use of the platinum-carbon catalyst, which will affect the catalytic performance of the platinum-carbon catalyst. If the platinum loading is too low, the catalytic activity of the platinum-carbon catalyst will be too low, which will affect the catalytic effect. Therefore, the platinum loading needs to be controlled within a suitable range, that is, to ensure a higher platinum loading, while avoiding excessively high platinum loading that causes platinum agglomeration and affects the catalytic performance.

[0099] The embodiments of the present application can obtain a platinum-carbon catalyst with a high platinum loading and a high catalytic activity by controlling the platinum loading in the platinum-carbon catalyst within a suitable range; moreover, the controllability of the platinum loading also improves the preparation method of the platinum-carbon catalyst and the applicability of the platinum-carbon catalyst, so as to realize the preparation of platinum-carbon catalysts with different platinum loadings according to different usage requirements.

[0100] Furthermore, the amino compound solution is one of melamine solution, methylguanamine solution, cyanuric acid solution, and cyanuric acid solution;

[0101] The carbon carrier is one or more of XC-72, EC-300J, EC-600JD, MH-18, and BP2000.

[0102] In the examples of the present application, the poor stability of the traditional platinum-carbon catalyst is mainly due to the oxidation of the platinum surface during the reaction, which causes the dissolution, aggregation and migration of platinum ions, resulting in a decrease in catalytic performance. Therefore, the use of an amino compound solution to modify the catalyst can weaken the interaction between platinum particles and oxygen-containing intermediates during the oxygen reduction process and improve the durability of the catalyst material. The amino compound solution can be one of a melamine solution, a methylguanamine solution, a cyanuric acid solution, and a cyanuric acid solution.

[0103] In the embodiments of the present application, the carbon carrier can be one or more of XC-72, EC-300J, EC-600JD, MH-18, and BP2000. The raw materials for preparation can be easily obtained, which can improve the convenience of the overall preparation process.

[0104] The embodiment of the present application uses an amino compound solution to modify the catalyst, which can effectively improve the catalytic performance of the catalyst; and the carbon carrier raw material acquisition channel is simple, making the overall preparation process simpler and improving the convenience of preparation.

[0105] In the embodiments of the present application, a carbon carrier is pretreated with an oxidizing acid solution to increase the concentration of hydroxyl groups on the surface and in the pores of the carrier, improve the hydrophobic properties of the carrier, enhance the interaction between the carrier and platinum, and increase the platinum loading; a platinum-carbon catalyst is prepared by an impregnation method, the operation process is simple, and the problem of platinum agglomeration during the heat treatment process can be avoided by reasonably controlling the temperature and time of the heat treatment to ensure that the platinum can be evenly loaded on the carbon carrier; the catalyst is modified by an amino compound solution, which can weaken the interaction between the platinum particles and the oxygen-containing intermediates during the oxygen reduction process, so that the prepared catalyst has higher mass specific activity and area specific activity, effectively improves the catalytic activity of the catalyst, and improves the problem of poor catalytic performance of the catalyst when the platinum loading is high.

[0106] The present application also provides a platinum-carbon catalyst, which is prepared by the above-mentioned preparation method; the surface of the target carbon carrier of the platinum-carbon catalyst includes a plurality of evenly distributed platinum particles, and the particle size of the platinum particles is 2-5 nm. The even distribution of platinum can make the catalyst have better catalytic performance, so as to avoid the problem of decreased catalytic performance of the catalyst due to platinum agglomeration.

[0107] Embodiment 1:

[0108] This embodiment provides a platinum-carbon catalyst and a preparation method thereof, and the specific preparation method includes:

[0109] 2 g of carbon black carrier MH-18 was placed in a 4M nitric acid solution, and then treated in a water bath at 80°C for 4 h. After the treatment, it was fully washed with ultrapure water until the filtrate was neutral, and dried in a vacuum oven at 60°C overnight to obtain the target carbon carrier.

[0110] Weigh 1.5 g of the target carbon carrier prepared above, ultrasonically disperse it in 60 mL of ultrapure water, then add 40 mL of chloroplatinic acid solution (concentration 0.192 M) to prepare a suspension, ultrasonically disperse it for 30 min, and continuously evaporate it under 70 ° C with magnetic stirring until most of the liquid disappears. The whole is in a viscous yogurt-like state and then placed in a freeze dryer for freeze drying for 15 h. The freeze-dried product is placed in a crucible and heat-treated in a 10% hydrogen-argon mixed gas for reduction. The heat treatment reduction temperature is 150 ° C and the time is 1 h to obtain an initial platinum-carbon catalyst; wherein the mass content of Pt metal is 50%;

[0111] The initial platinum-carbon catalyst prepared above was immersed in a 1 mmol / L melamine aqueous solution, subjected to ultrasound for 30 min, and then vacuum dried to obtain a melamine-modified platinum-carbon catalyst. The transmission electron microscopy image of the melamine-modified platinum-carbon catalyst prepared above is as follows: Figure 6 shown.

[0112] Embodiment 2:

[0113] This embodiment provides a platinum-carbon catalyst and a preparation method thereof, and the specific preparation method includes:

[0114] 2 g of carbon black carrier MH-18 was placed in a 0.2 M aqueous solution of ammonium persulfate, and then treated in a water bath at 80°C for 4 h. After the treatment, it was fully washed with ultrapure water until the filtrate was neutral, and dried in a vacuum oven at 60°C overnight to obtain the target carbon carrier.

[0115] Weigh 1.2 g of the target carbon carrier prepared above, ultrasonically disperse it in 52 mL of ultrapure water, then add 48 mL of chloroplatinic acid solution (concentration 0.192 M) to prepare a suspension, ultrasonically disperse it for 30 min, and continuously evaporate it under 70 ° C with magnetic stirring until most of the liquid disappears. The whole is in a viscous yogurt-like state and then placed in a freeze dryer for freeze drying for 15 h. The freeze-dried product is placed in a crucible and heat-treated in a 10% hydrogen-argon mixed gas for reduction. The heat treatment reduction temperature is 400 ° C and the time is 1.5 h to obtain an initial platinum-carbon catalyst; wherein the mass content of Pt metal is 60%;

[0116] The initial platinum-carbon catalyst prepared above was immersed in a 1 mmol / L methylguanamine aqueous solution, ultrasonicated for 30 min, and then vacuum dried to obtain a methylguanamine-modified platinum-carbon catalyst. The transmission electron microscopy image of the methylguanamine-modified platinum-carbon catalyst prepared above is as follows: Figure 7 shown.

[0117] Comparative Example 1:

[0118] This comparative example provides a platinum-carbon catalyst and a preparation method thereof, and the specific preparation method includes:

[0119] 2 g of carbon black carrier MH-18 was placed in a 4M nitric acid solution, and then treated in a water bath at 80°C for 4 h. After the treatment, it was fully washed with ultrapure water until the filtrate was neutral, and dried in a vacuum oven at 60°C overnight to obtain the target carbon carrier.

[0120] Weigh 1.5 g of the target carbon carrier prepared above, ultrasonically disperse it in 60 mL of ultrapure water, then add 40 mL of chloroplatinic acid solution (concentration 0.192 M) to prepare a suspension, ultrasonically disperse it for 30 min, and continuously evaporate it under 70 ° C with magnetic stirring until most of the liquid disappears. The whole is viscous yogurt-like and then placed in a freeze dryer for freeze drying for 15 h, and the freeze-dried product is placed in a crucible and heat-treated in 10% hydrogen-argon mixed gas for reduction. The heat treatment reduction temperature is 150 ° C and the time is 1 h to obtain a platinum-carbon catalyst; wherein the mass content of Pt metal is 50%;

[0121] Comparative Example 2:

[0122] This comparative example provides a platinum-carbon catalyst and a preparation method thereof, and the specific preparation method includes:

[0123] 2 g of carbon black carrier MH-18 was placed in a 0.2 M aqueous solution of ammonium persulfate, and then treated in a water bath at 80°C for 4 h. After the treatment, it was fully washed with ultrapure water until the filtrate was neutral, and dried in a vacuum oven at 60°C overnight to obtain the target carbon carrier.

[0124] Weigh 1.2 g of the target carbon carrier prepared above, ultrasonically disperse it in 52 mL of ultrapure water, then add 48 mL of chloroplatinic acid solution (concentration 0.192 M) to prepare a suspension, ultrasonically disperse it for 30 min, and continuously evaporate it under 70 ° C with magnetic stirring until most of the liquid disappears. The whole is viscous yogurt-like and then placed in a freeze dryer for freeze drying for 15 h. The freeze-dried product is placed in a crucible and heat-treated in a 10% hydrogen-argon mixed gas for reduction. The heat treatment reduction temperature is 400 ° C and the time is 1.5 h to obtain a platinum-carbon catalyst; wherein the mass content of Pt metal is 60%;

[0125] In the examples of the present application, the preparation process of the platinum-carbon catalyst in Comparative Example 1 is similar to that in Example 1, except that Comparative Example 1 does not use melamine solution for modification; the preparation process of the platinum-carbon catalyst in Comparative Example 2 is similar to that in Example 2, except that Comparative Example 2 does not use methylguanamine solution for modification.

[0126] In the examples of the present application, the platinum-carbon catalysts prepared in Examples 1-2 and Comparative Examples 1-2 are configured into slurries for electrochemical testing. The specific steps are as follows: a certain amount of platinum-carbon catalyst is weighed, and 50 μL of 5% Nafion solution (naphthol solution), 2 mL of deionized water and 2 mL of isopropanol are added in sequence; ultrasonication with a power of not less than 200 W is used for 30 minutes to mix the slurry evenly, and the water bath temperature must be kept at no more than 20 ° C during the ultrasonic process; according to the catalyst loading on the electrode surface of 50 μg / cm 2 -200μg / cm 2 , take an appropriate amount of the dispersed slurry and evenly drip it onto the smooth and clean surface of the disk electrode twice, let it dry naturally and completely, and use it as the working electrode; place the working electrode obtained above in an electrolytic cell to construct a three-electrode system; wherein the reference electrode is a reversible hydrogen electrode (RHE), the counter electrode is a platinum sheet, and the electrolyte is a 0.1M perchloric acid solution saturated with N2.

[0127] In the embodiment of the present application, the steps of testing the cyclic voltammetry curve are as follows: first, the catalyst is activated at a scanning speed of 200 mV / s until the hydrogen desorption peak area no longer increases, and then scanned at a speed of 20 mV / s for 3 cycles, and the potential scanning range is 0.025V-1.2V (relative to RHE); the hydrogen desorption charge in the voltage range of 0.05-0.4V is integrated, and the hydrogen adsorption value of the Pt surface monolayer is 0.21mC cm -2 , the electrochemical active area of ​​the catalyst was obtained by normalizing it according to the mass of Pt.

[0128] In the present embodiment, the calculation formula of electrochemical active area (ECSA) is as follows:

[0129]

[0130] Where S is the integrated area, C is the hydrogen hydroxide adsorption charge constant on the smooth Pt surface, 0.21 mC cm -2 , v is the scan rate, mPt is the amount of Pt loaded on the working electrode, μg cm -2 .

[0131] In the embodiment of the present application, the steps of testing the oxygen reduction linear scanning curve are as follows: the above-mentioned electrolyte is replaced with a 0.1M perchloric acid solution saturated with O2, and scanned for 3 circles at a scanning speed of 10mV / s and an electrode speed of 1600rpm. The potential scanning range is 0.025V-1.2V (relative to RHE), and the kinetic diffusion current is calculated according to the Koutecky-Levich formula. Finally, the current value at a potential of 0.9V is taken to calculate the MA (mass specific activity), and the calculation is shown as follows:

[0132]

[0133] Where j is the experimentally measured current, jk is the dynamic current of the rotating disk, and jd is the limiting current.

[0134] The calculation formula of MA is as follows:

[0135]

[0136] The calculation formula of SA (area specific activity) is as follows:

[0137]

[0138] In the examples of the present application, the platinum-carbon catalysts prepared in the above examples 1-2 and comparative examples 1-2 were electrochemically tested, and the test results are shown in Table 1 below. As can be seen from Table 1, the modification of the catalyst using an amino compound solution does not significantly reduce the Pt loading on the catalyst, and after modification by an amino compound solution, the mass specific activity and area specific activity of the catalyst are significantly higher than those of the catalyst not modified by the amino compound solution, which indicates that the modification of the catalyst using an amino compound solution can effectively improve the catalytic activity of the catalyst to obtain a catalyst with better catalytic performance.

[0139] Table 1. Catalyst performance test results

[0140]

[0141] In the embodiments of the present application, Figure 6 is a transmission electron microscopy image of the melamine-modified platinum-carbon catalyst prepared in Example 1, Figure 7 is a transmission electron micrograph of the methylguanamine-modified platinum-carbon catalyst prepared in Example 2. Figure 6 and Figure 7 It can be seen that the platinum-carbon catalyst prepared by the preparation method of the platinum-carbon catalyst provided in the embodiment of the present application, wherein the platinum particles can be evenly distributed on the carbon carrier, can effectively avoid the problem of easy agglomeration of the platinum particles.

[0142] It can be seen from the embodiments provided by the present application that the present application pre-treats the carbon carrier to obtain a target carbon carrier; uses a platinum precursor to load the target carbon carrier with platinum to obtain an initial platinum-carbon catalyst; impregnates the initial platinum-carbon catalyst in an amino compound solution to obtain an impregnation mixture; in the impregnation mixture, the content of the initial platinum-carbon catalyst is 0.5-1.5 g / L; the concentration of the amino compound solution is 0.1-10 mmol / L; the impregnation mixture is ultrasonically treated for 20-30 minutes at room temperature to obtain an intermediate platinum-carbon catalyst; the ultrasonic power corresponding to the ultrasonic treatment is 80-120 W; the intermediate platinum-carbon catalyst is vacuum dried at 60-80°C for 8-16 hours to obtain a platinum-carbon catalyst. The present application pretreats a carbon carrier with an oxidizing acid solution to increase the concentration of hydroxyl groups on the carrier surface and in the pores, enhances the interaction between the carrier and platinum, and increases the platinum loading; prepares a platinum-carbon catalyst by an impregnation method, which has a simple operation process and can avoid the problem of platinum agglomeration during the heat treatment process by reasonably controlling the temperature and time of the heat treatment, so as to ensure that the platinum can be uniformly loaded on the carbon carrier; modifies the catalyst by an amino compound solution, which can weaken the interaction between the platinum particles and the oxygen-containing intermediates during the oxygen reduction process, so that the prepared catalyst has higher mass specific activity and area specific activity, effectively improves the catalytic activity of the catalyst, and improves the problem of poor catalytic performance of the catalyst when the platinum loading is high.

[0143] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a platinum-carbon catalyst, characterized in that: The method comprises: Pretreating the carbon carrier to obtain a target carbon carrier; Using a platinum precursor to load platinum on the target carbon carrier to obtain an initial platinum-carbon catalyst; The initial platinum-carbon catalyst is impregnated in an amino compound solution to obtain an impregnation mixture; in the impregnation mixture, the content of the initial platinum-carbon catalyst is 0.5-1.5 g / L; and the concentration of the amino compound solution is 0.1-10 mmol / L; The impregnation mixture is subjected to ultrasonic treatment for 20-30 minutes at room temperature to obtain an intermediate platinum-carbon catalyst; the ultrasonic treatment corresponds to an ultrasonic power of 80-120 W; The intermediate platinum-carbon catalyst is vacuum dried at 60-80° C. for 8-16 hours to obtain the platinum-carbon catalyst.

2. The method according to claim 1, characterized in that: The method of using a platinum precursor to load platinum on the target carbon carrier to obtain an initial platinum-carbon catalyst comprises: Mixing the target carbon carrier, the platinum precursor and a solvent to obtain an initial mixture; Stirring the initial mixture at 60-80° C. until the stirring product is in a sticky paste state, thereby obtaining an intermediate mixture; The intermediate mixture is freeze-dried to obtain a freeze-dried product; the freeze-drying time is 12-20 hours; The freeze-dried product is heat-treated in an atmosphere of reducing gas to obtain the initial platinum-carbon catalyst; the reducing gas is hydrogen or a hydrogen-argon mixture; the heat treatment temperature corresponding to the heat treatment is 100-400° C., and the heat treatment time is 0.5-4h.

3. The method according to claim 2, characterized in that The target carbon carrier, the platinum precursor and the solvent are mixed to obtain an initial mixture, comprising: The target carbon carrier is placed in the solvent for dispersion to obtain a mixture of the target carbon carrier and the solvent; the solvent is one or more of ultrapure water and ethanol; the dispersion mass ratio of the target carbon carrier to the solvent is 1: (30-50); The solution containing the platinum precursor is added to the mixture of the target carbon carrier and the solvent, and ultrasonic dispersion treatment is performed in an ice-water bath to obtain the initial mixture; the ultrasonic dispersion treatment time is 20-30 minutes.

4. The method according to claim 1, characterized in that The pretreatment of the carbon carrier to obtain the target carbon carrier comprises: Using an oxidizing acid solution to acid-wash the carbon support to obtain an initial carbon support; The initial carbon carrier is vacuum dried at 60-80° C. for 12-24 hours to obtain a target carbon carrier.

5. The method according to claim 4, characterized in that The step of acid washing the carbon support with an oxidizing acid solution to obtain an initial carbon support comprises: The carbon carrier is mixed with the oxidizing acid solution, and stirred at room temperature-100° C. to obtain a mixture of the carbon carrier and the oxidizing acid solution; the stirring time is 1-4 hours; The mixture of the carbon support and the oxidizing acid solution is filtered and washed with deionized water until the filtrate is neutral to obtain the initial carbon support.

6. The method according to claim 4, characterized in that The oxidizing acid solution is one of nitric acid solution, ammonium persulfate solution, sulfuric acid solution and hydrogen peroxide solution; the concentration of the oxidizing acid solution is 0.2-10 mol / L.

7. The method according to claim 1, characterized in that The amino compound solution is one of melamine solution, methylguanamine solution, cyanuric acid solution, and cyanuric acid solution; The carbon carrier is one or more of XC-72, EC-300J, EC-600JD, MH-18, and BP2000.

8. The method according to claim 1, characterized in that: The platinum loading in the platinum-carbon catalyst is 40-70%.

9. The method according to claim 3, characterized in that: The platinum precursor is one of chloroplatinic acid, potassium chloroplatinate, tetraammineplatinum, dinitrodiammineplatinum, and hexahydroxyplatinic acid.

10. A platinum-carbon catalyst, characterized in that The platinum-carbon catalyst is prepared by the preparation method according to any one of claims 1 to 9; the surface of the target carbon carrier of the platinum-carbon catalyst comprises a plurality of evenly distributed platinum particles, and the particle size of the platinum particles is 2-5 nm.

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