A method for preparing a platinum-carbon catalyst

Abstract

The present invention discloses a method for preparing a platinum-carbon catalyst, comprising: S1. preparing three kinds of liquids, namely, conductive carbon black dispersion liquid, platinum-containing precursor solution and alkali solution; S2. continuously passing the three kinds of liquids into a pre-reactor through a feeding system, mixing and pre-reacting, and obtaining a reaction slurry; S3. continuously allowing the reaction slurry to enter a plurality of parallel microchannel reactors for reaction; S4. passing the slurry into a microchannel mixer, and reacting with an acidic neutralizing liquid for neutralization; S5. passing the neutralized slurry into a solid-liquid phase separator, separating the catalyst solid, and then obtaining a platinum-carbon catalyst after impurity removal and drying. The method for preparing the platinum-carbon catalyst of the present invention solves the problem of capacity amplification in the research and development and production of traditional catalysts, and at the same time adopts a continuous production mode to realize online parameter monitoring, effectively maintaining the batch stability and reliability of the catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a method for preparing a platinum-carbon catalyst. Background Art

[0002] As a power generation device that can directly convert the chemical energy of hydrogen into electrical energy and achieve efficient external work, hydrogen fuel cells have the advantages of high energy density and zero emissions. In the context of the advocacy of green energy around the world today, they have huge development potential.

[0003] As an electrochemical conversion device that converts chemical energy into electrical energy, the product performance of fuel cells depends largely on the performance and dosage of their high-performance precious metal catalysts. As the technology matures, thanks to the increasing utilization of precious metals in fuel cell catalysts, the amount of precious metals consumed per unit power of fuel cells has also decreased. However, as the industry matures, its demand for precious metal catalysts, especially platinum-carbon catalysts, is on the rise. Due to the differences in product positioning and technical routes of various battery stack and membrane electrode manufacturers, each has different requirements for the loading, performance requirements and detailed characteristics of fuel cell membrane electrode catalysts, resulting in uncertainty and risk in the research and development and production of catalysts.

[0004] Since the catalysts used in fuel cells are precious metal-supported catalysts, they are characterized by high preparation costs. They are developed only through microgram-level experiments during the research and development stage. The "three transfers" of flow, mass transfer and heat transfer in the subsequent amplification process are prominent, and it is difficult to completely repeat the laboratory and research and development results. Therefore, for mass production of precious metal catalysts, there are problems such as large equipment investment and high risk costs. At the same time, due to the needs of product development, for different models of products (mainly manifested in different loadings, different raw materials and different reaction conditions), various mass production parameters need to be confirmed separately, and cannot be simply unified into a single process or equipment. The product development cycle is long and the uncertainty is high.

[0005] At present, the mainstream catalyst preparation process is mainly microwave ethylene glycol reduction method, such as CN201410838137.4-Fuel Cell, a platinum-carbon catalyst and its preparation method, CN202010971392.1-Platinum-carbon catalyst and its preparation method, using direct configuration of mixed reaction solution, batch reactor reaction. However, the parameters of each batch are difficult to control, resulting in poor consistency of product batches. For example, in CN201811603474.X-A platinum-carbon catalyst for fuel cell production and its preparation method, although it uses continuous microwave reaction to improve the equipment capacity, it uses microwave direct heating method, the parameters are difficult to control, and there are certain difficulties in mass production. Patent CN201910513116.8-A preparation method of platinum-carbon catalyst based on microreactor, although it uses a microchannel reactor, the number of reactors is only one, which can only meet the single production capacity requirements, and its reactants are also mixed in advance, and there will be some pre-reaction mechanisms that cause differences in product consistency. Patent CN202110831034.5-A platinum-carbon catalyst and its preparation method, which pre-mixes all products before the microchannel reactor, has the same limitations as the above patents, and the above patents do not add online monitoring before and after the continuous reaction process. If there is a parameter deviation in the product, it is difficult to discover and intervene in the first time. Summary of the invention

[0006] The present invention provides a modular catalyst mass production preparation technology with controllable production capacity, which solves the problem of capacity expansion in traditional catalyst research and development and production. At the same time, it adopts a continuous production mode to realize online parameter monitoring, effectively maintaining the batch stability and reliability of the catalyst.

[0007] The present invention provides a method for preparing a platinum-carbon catalyst, comprising the following steps:

[0008] S1. Prepare three liquids including conductive carbon black dispersion liquid, platinum-containing precursor solution and alkali solution;

[0009] S2. The three feed solutions are continuously introduced into the pre-reactor through the feeding system in a predetermined ratio, and the three feed solutions are fully mixed and pre-reacted in the pre-reactor using a microchannel mixer to obtain a reaction slurry;

[0010] S3. The reaction slurry after the pre-reaction continuously enters a plurality of parallel microchannel reactors for reaction;

[0011] S4. The slurry after the reaction is passed into a microchannel mixer and neutralized with an acidic neutralizing solution;

[0012] S5. The neutralized slurry is passed into a solid-liquid phase separator to separate the catalyst solid, and then the platinum-carbon catalyst is obtained after impurity removal and drying;

[0013] Wherein, monitoring devices are arranged at the inlets of the pre-reactor and the microchannel reactor, and the monitoring devices are used for online monitoring of the pH value, viscosity, particle size distribution and temperature of the slurry entering the pre-reactor and the microchannel reactor.

[0014] In step S1 of the present invention, the conductive carbon black dispersion liquid is composed of conductive carbon black, polyol, water and surfactant, and its solid content is preferably 0.1-2.0%;

[0015] Preferably, the conductive carbon black is selected from one or more of Lion Carbon Black EC600J, EC300J, ECP300JD, Cabot Carbon Black XC-72, BP2000 and carbon nanotubes;

[0016] Preferably, the polyol is selected from one or more of propylene glycol, glycerol, and ethylene glycol;

[0017] Preferably, the surfactant is selected from one of Tween 40, Tween 80 and Triton X-100.

[0018] Preferably, the preparation method of the conductive carbon black dispersion liquid is: after mixing the raw materials, sequentially subjecting the raw materials to shear emulsification, ultrasonic dispersion, cell crushing and high-pressure homogenization treatment to obtain the conductive carbon black dispersion liquid.

[0019] In step S1 of the present invention, the platinum-containing precursor solution is composed of a platinum salt and water. Preferably, the platinum salt is one of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate;

[0020] The weight ratio of the platinum salt to water is preferably 1:20 to 50 based on the weight of platinum.

[0021] In step S1 of the present invention, the alkali solution is composed of hydroxide and water. Preferably, the hydroxide is sodium hydroxide or potassium hydroxide, and the weight ratio of the hydroxide to water is preferably 1:9-20.

[0022] In step S2 of the present invention, the weight ratio of the conductive carbon black dispersion liquid and the platinum-containing precursor solution introduced into the pre-reactor is preferably 1:9 to 7:3, based on the weight of platinum solid and the weight of conductive carbon black.

[0023] Preferably, in steps S2 and S3, the physicochemical parameters of the slurry are controlled by a monitoring device as follows:

[0024] The pH value of the slurry is 12-14, the solid content is 0.2-2.0%, and the temperature is not greater than 30°C;

[0025] The particle size distribution of the slurry is: 3μm≤D50≤5μm, 4μm≤D90≤6μm;

[0026] The viscosity of the slurry is less than the maximum viscosity that the microchannel reactor can handle.

[0027] Preferably, in step S2, the reaction temperature of the pre-reaction is 10-30° C., and the reaction time is 8-24 h.

[0028] Preferably, in step S2, the microchannel mixer used in the pre-reactor is a small-flux microchannel mixer.

[0029] Preferably, in step S3, the heating method of the microchannel reactor is one of heat exchange heating, microwave heating and thermal radiation heating; the reaction temperature is 80 to 135° C., and the reaction time is 2 to 10 min;

[0030] Preferably, the total reactant flow rate of the multiple parallel microchannel reactors is 5 to 100 L / h.

[0031] Preferably, in step S5, a ceramic membrane filtration system is used to separate the solid and liquid phases.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention uses a plurality of microchannel reactors, microchannel mixers and microchannel separators. The heat exchange method in the microchannel uses an oil bath and a water bath method, which will not cause temperature deviation, and has the characteristics of flexible and controllable output and good batch consistency.

[0034] 2. The present invention adopts multiple replaceable and detachable parallel microreactors to achieve simple and controllable production line capacity; the use of microreactors as a reaction means ensures the consistency of catalyst performance in each batch; at the same time, compared with traditional kettle reactors, microreactors have no amplification effect and can be better combined with research and development to achieve mass production.

[0035] 3. The present invention adds multiple sensors before, during and after the reaction to control the reaction parameters online, thereby ensuring the safety of production quality. At the same time, due to the continuous production mode and the fact that the raw materials are not pre-mixed before the formal reaction, once a parameter abnormality occurs, it can be discovered and intervened in the first place, thereby effectively reducing material losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The process flow chart of synthesizing platinum-carbon catalyst in the embodiment of the present invention;

[0037] Figure 2 This is a microscopic TEM image of the catalyst product produced in an embodiment of the present invention;

[0038] Figure 3 The electrochemical CV test performance curve of the platinum-carbon catalyst produced in the embodiment of the present invention;

[0039] Figure 4 This is the electrochemical LSV test performance curve of the platinum-carbon catalyst produced in the embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0042] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0043] See also Figure 1 The present invention provides a modular catalyst mass production preparation technology with controllable production capacity, which specifically adopts the following technical solutions:

[0044] S1. First, a conductive carbon black dispersion liquid, a platinum-containing precursor solution and an alkali solution are prepared step by step.

[0045] In the present invention, the conductive carbon black dispersion liquid is composed of conductive carbon black, polyol, water and surfactant, wherein the solid content is preferably 0.1-2.0%. Preferably, the conductive carbon black is selected from one or more of Lion Carbon Black EC600J, EC300J, ECP300JD, Cabot Carbon Black XC-72, BP2000 and carbon nanotubes; preferably, the polyol is selected from one or more of propylene glycol, glycerol and ethylene glycol; preferably, the surfactant is selected from one of Tween 40, Tween 80 and Triton X-100.

[0046] In the present invention, the amount of conductive carbon black dispersion liquid prepared can be flexibly increased or decreased according to the target production capacity required. When preparing the conductive carbon black dispersion liquid, after mixing the raw materials, the dispersion process of shear emulsification, ultrasonic dispersion, cell crushing and high-pressure homogenization can be carried out in sequence to improve the dispersion effect of the raw materials. When performing continuous dispersion treatment, in order to prove production capacity and save equipment time, preferably, the number of each dispersion equipment should correspond to its processing time. For example, high-speed shear emulsification for 60 minutes, ultrasonic dispersion for 30 minutes, cell crushing for 10 minutes and high-pressure homogenization for 10 minutes, then the ratio of the number of processing equipment in each dispersion stage - high-speed shear emulsification: ultrasonic dispersion: cell crushing: high-pressure homogenization = 6:3:1:1, so that the amount of slurry processed per unit time in each dispersion link can be equal, thereby achieving continuous preparation.

[0047] Preferably, the continuous dispersion process may select an integrated continuous dispersion device, which simultaneously has dispersion functions such as shear dispersion, ultrasonic wall breaking and homogenization defoaming, and can realize online monitoring and continuous discharging.

[0048] In the present invention, the platinum-containing precursor solution is obtained by dissolving a platinum salt in water and mixing them evenly. The platinum salt is one of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate; the weight ratio of the platinum salt to water is preferably 1:20 to 50 based on the weight of platinum. Similarly, the amount of platinum precursor solution prepared can be flexibly increased or decreased according to the target production capacity required.

[0049] In the present invention, the alkali solution is obtained by dissolving a hydroxide in water. The hydroxide is sodium hydroxide or potassium hydroxide, and the weight ratio of the hydroxide to water is preferably 1:9 to 20. The amount of alkali solution prepared can be flexibly increased or decreased according to the target production capacity required.

[0050] S2. The three feed liquids are continuously introduced into the pre-reactor through the feeding system according to a predetermined ratio, and the three feed liquids are fully mixed and pre-reacted in the pre-reactor using a microchannel mixer to obtain a reaction slurry.

[0051] In the present invention, the weight ratio of the conductive carbon black dispersion liquid and the platinum-containing precursor solution introduced into the pre-reactor is preferably 1:9 to 7:3, based on the weight of platinum solid and the weight of conductive carbon black.

[0052] In the synthesis process of the platinum-carbon catalyst, if the reaction raw materials are mixed in advance, the reaction will start slowly. Although it is not heated to the reaction temperature, a slow reaction will occur, which will lead to differences in the consistency of the product. In the present invention, the raw materials are not mixed in advance, but three kinds of feed liquids are prepared in advance. Since the reaction raw materials will not contact each other, no pre-reaction will occur, thereby avoiding differences in the consistency of the product.

[0053] In the present invention, the prepared three feed liquids can be placed in a feed liquid cylinder with stirring, and the uniformity of the feed liquids can be ensured by continuous stirring. Then, the three feed liquids continuously enter the pre-reactor through a feeding system, and the feeding system can accurately control the material flow of the three feed liquids, which is conducive to improving the consistency of the reaction slurry.

[0054] In the present invention, after the three feed liquids enter the pre-reactor, they are mixed in the pre-reactor and start pre-reaction. The pre-reactor uses a microchannel mixer for mixing, and its mixing principle is far superior to that of the traditional kettle reactor, so the mixing process is very uniform, and the problem of poor product consistency caused by uneven mixing will not occur. The platinum-carbon catalyst prepared by the pre-reaction has a more uniform distribution of metal particles and better performance.

[0055] In some embodiments, the pre-reactor uses a high-throughput microchannel mixer (with a processing capacity greater than 100 ml / min), followed by a reactor. The size of the microchannel mixer belongs to the microscale category, and the direct advantage is that the diffusion time is very short and the mixing process is very fast. The reaction slurry after the microchannel mixer is then placed in a stirred reactor for pre-reaction, and the pre-reaction temperature is preferably 10 to 30 ° C, and the pre-reaction time is preferably 8 to 24 hours.

[0056] In other embodiments, the pre-reactor uses a small-flux microchannel mixer (with a processing volume of less than 10 ml / min), and then directly enters multiple microchannel reactors at the same set flow rate through multiple three-way outlets. Using a small-flux microchannel mixer to directly perform pre-reaction can accurately control the slurry pre-reaction time and effectively increase the uniformity and consistency of the slurry pre-reaction.

[0057] In the present invention, the flow rates of the three feed solutions entering the pre-reactor can be controlled according to the production of catalysts with different loadings, and only the reaction pH, the relative ratio of the metal and the carbon carrier, and the system viscosity need to be controlled. In addition, the processing capacity of the pre-reactor can be flexibly increased or decreased according to the target production capacity to be produced.

[0058] In the present invention, before the three feed liquids enter the pre-reactor and before entering the multiple parallel microchannel reactors for reaction, the key characteristic physicochemical parameters of the slurry are continuously detected online, including: pH value, viscosity, particle size distribution and temperature of the slurry. These physicochemical parameters have a great influence on the performance of the synthesized catalyst. Therefore, through online monitoring, it is not only beneficial to improve the consistency of the slurry and ensure the consistency of the performance of the synthesized catalyst, but also when the slurry parameters are abnormal, they can be discovered in the first time, which can effectively reduce material losses.

[0059] Preferably, before the three liquid feeds enter the pre-reactor and before entering the multiple parallel microchannel reactors for reaction, the pH value of the liquid feed is controlled to be 12-14 through online monitoring, the particle size distribution of the reaction slurry is 3μm≤D50≤5μm, 4μm≤D90≤6μm, the viscosity of the reactants should be less than the maximum viscosity that the microchannel reactor can handle, and the inlet slurry temperature is not more than 30°C.

[0060] In the present invention, the chloroplatinic acid reduction reaction needs to be carried out under alkaline conditions. If the pH of the feed liquid is inappropriate, the chloroplatinic acid reduction reaction cannot be guaranteed. The amount of solid content determines the reaction efficiency and uniformity. If the solid content is too low, although it is uniform, the efficiency is low. If the solid content is too high, the slurry uniformity may decrease and it is not easy to disperse. The temperature of the feed liquid is also very important. If the temperature of the feed liquid is too high, the reaction will start early during the pre-reaction treatment process, causing the system to deteriorate. In addition, the particle size of the slurry also has an effect on the reaction. If the slurry particle size is too large, the utilization rate of the carrier will decrease. Therefore, the pH value of the feed liquid or slurry monitored by the online monitoring system is 12 to 14, the particle size distribution is: 3μm≤D50≤5μm, 4μm≤D90 ≤6μm, the viscosity of the reactant should be less than the maximum viscosity that the microchannel reactor can handle, and the inlet slurry temperature is not more than 30°C. Since the microchannel reactor does not have high requirements for viscosity, the viscosity of the general feed liquid meets the requirements.

[0061] S3. The reaction slurry after the pre-reaction is continuously fed into a plurality of parallel microchannel reactors for reaction.

[0062] In the present invention, the reaction slurry that is fully mixed and pre-reacted enters multiple high-temperature microchannel reactors at the same set flow rate through multiple three-way outlets to react. The multiple microchannel reactors are connected in parallel and can be disassembled and replaced, so the number of parallel microchannel reactors can be flexibly increased or decreased according to the production capacity. Preferably, the total reactant flow rate of the multiple parallel microchannel reactors is 5 to 100 L / h.

[0063] The heating method of the microchannel reactor can be selected from heat exchange heating, microwave heating and thermal radiation heating, wherein the heat exchange heating is preferably an oil bath or a water bath, and no temperature deviation occurs. The reaction temperature is preferably 80 to 135°C, and the reaction time is preferably 2 to 10 minutes.

[0064] S4. The slurry after the reaction is introduced into a microchannel mixer to undergo a neutralization reaction with an acidic neutralizing solution.

[0065] In the present invention, the slurry that has completed the high-temperature rapid reaction is continuously introduced into the microchannel mixer, firstly rapidly cooled by heat exchange, and then mixed with the acidic neutralizing liquid. By controlling the ratio of the acidic solution to the reaction slurry, the pH value of the slurry is monitored in real time to be 7.

[0066] S5. The neutralized slurry is passed into a solid-liquid phase separator to separate the catalyst solid, and then the platinum-carbon catalyst is obtained after impurity removal and drying.

[0067] After being neutralized with an acid solution, the material is collected and continuously fed into a ceramic membrane filtration system to reduce the content of organic matter, inorganic salts and other impurities in the slurry, and then subjected to batch positive pressure filtration, vacuum drying and test bottling.

[0068] The platinum-carbon catalyst prepared by the present invention can have a noble metal loading of 10% to 70%.

[0069] Example 1

[0070] It is planned to prepare a platinum-carbon catalyst with a production capacity of more than 200g / d and a platinum loading of 50%, and adopt the following production technology plan.

[0071] 1. Prepare conductive carbon black dispersion liquid, platinum-containing precursor solution and alkali solution step by step.

[0072] (1) Conductive carbon black dispersion liquid

[0073] Conductive carbon black XC72R is evenly dispersed in isopropanol, and the weight ratio of XC72R: isopropanol is 1:99. After the slurry is weighed using a balance, each 2L slurry is a batch, and the following dispersion process is used: high-speed shear emulsification for 60 minutes, ultrasonic dispersion for 30 minutes, cell crushing for 10 minutes, and high-pressure homogenization for 10 minutes. In order to achieve a daily output of 200g, 10kg / d needs to be prepared, and a total of 5 batches are processed. In order to ensure production capacity and save equipment time, continuous dispersion treatment is carried out, that is, the equipment quantity ratio is high-speed shear emulsification: ultrasonic dispersion: cell crushing: high-pressure homogenization = 6:3:1:1.

[0074] (2) Platinum-containing precursor solution

[0075] The platinum precursor used is hexahydrate chloroplatinic acid solid, the ratio of hexahydrate chloroplatinic acid solid to water is 1:20, and after dissolution, it is stirred for 2 hours to make it uniform. In order to achieve a daily output of 200g, at least 5kg / d of platinum precursor solution needs to be prepared.

[0076] (3) Alkaline solution

[0077] Sodium hydroxide is dissolved in ultrapure water to prepare the alkali solution, the ratio of sodium hydroxide to water is 1:9, and after dissolution, it is stirred for 2 hours to make it uniform. In order to achieve a daily output of 200g, at least 1.6kg / d of platinum precursor solution needs to be prepared.

[0078] 2. Place the three raw material liquids in a stirring liquid barrel, and the three liquids enter the pre-reactor continuously. The pre-reactor uses a small-flux microchannel mixer to directly perform pre-reaction. The reaction temperature in the pre-reaction microchannel reactor is set to 25℃±0.1℃. Before the three liquids enter the pre-reactor and before entering multiple parallel microchannel reactors for reaction, the key characteristic physical and chemical parameters of the slurry are continuously tested online. The main measured pH value is 12-14, the particle size distribution of the reaction slurry is 3μm≤D50≤5μm, 4μm≤D90≤6μm, the viscosity of the reactants should be less than the maximum viscosity that the microchannel reactor can handle, and the inlet slurry temperature is not more than 30℃.

[0079] 3. The catalyst reaction slurry that has been fully mixed and pre-reacted enters multiple high-temperature microchannel reactors through multiple three-way outlets at the same set flow rate. The maximum processing capacity of each reactor is 5L per hour. To meet the above production capacity, at least 2 high-temperature microchannel reactors need to be connected in parallel. The reactor is set to a reaction temperature of 125℃±0.1℃ and a reaction time of 12min.

[0080] 4. The slurry that has completed the high-temperature rapid reaction will then continuously enter the microchannel mixer, first heat exchange and quickly cool to 25°C, and then mix with the acidic neutralizing solution. By controlling the ratio of the acidic solution to the reaction slurry, the pH value is monitored in real time to be 7. The material is then collected and continuously enters the ceramic membrane filtration system to reduce the content of organic matter, inorganic salts and other impurities in the slurry, and then positive pressure filtration, vacuum drying and test bottling are carried out in batches.

[0081] Performance Testing

[0082] The platinum-carbon catalyst product prepared in the example was analyzed by transmission electron microscopy to evaluate the microscopic morphology of the product. The electron microscope analysis pictures are as follows: Figure 2 As shown in the figure, it can be seen that the platinum particles have high dispersion, good particle size uniformity, and are evenly distributed on the surface of the conductive carbon black. The carrier has obvious pore characteristics, no pore structure collapse or blockage, and the product purity is high.

[0083] The prepared platinum-carbon catalyst was tested on a rotating disk electrode, the effective electrochemical active area was calculated by cyclic voltammetry, and the catalyst specific mass activity was evaluated by linear scanning method. The results are shown in Figure 3-4 shown.

[0084] Figure 3-4 The results show that the platinum-carbon catalyst prepared by the method of the present invention has excellent performance, good consistency, and meets the needs of large-scale preparation.

[0085] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for preparing a platinum-carbon catalyst, characterized in that: The following steps are involved: S1. preparing three liquids including a conductive carbon black dispersion liquid, a platinum-containing precursor solution and an alkali solution; S2. The three feed solutions are continuously introduced into the pre-reactor through the feeding system in a predetermined ratio, wherein the three feed solutions are fully mixed and pre-reacted in the pre-reactor using a microchannel mixer to obtain a reaction slurry; S3. The reaction slurry after the pre-reaction continuously enters a plurality of parallel microchannel reactors for reaction; S4. The slurry after the reaction is passed into a microchannel mixer and neutralized with an acidic neutralizing solution; S5. The neutralized slurry is passed into a solid-liquid phase separator to separate the catalyst solid, and then subjected to impurity removal and drying to obtain the platinum-carbon catalyst; Wherein, a monitoring device is provided at the inlet of the pre-reactor and the microchannel reactor, and the monitoring device is used to online monitor the pH value, viscosity, particle size distribution and temperature of the slurry entering the pre-reactor and the microchannel reactor; In step S1, the platinum-containing precursor solution is composed of a platinum salt and water, the platinum salt is one of chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate; the weight ratio of the platinum salt to the water is 1:20-50 based on the weight of platinum; the alkali solution is composed of a hydroxide and water, the hydroxide is sodium hydroxide or potassium hydroxide, and the weight ratio of the hydroxide to water is 1:9-20; In step S2, the weight ratio of the conductive carbon black dispersion liquid and the platinum-containing precursor solution introduced into the pre-reactor is 1:9 to 7:3, based on the weight of the platinum solid and the weight of the conductive carbon black; In steps S2 and S3, the physicochemical parameters of the slurry are controlled by the monitoring device as follows: The pH value of the slurry is 12 to 14, the solid content is 0.2 to 2.0%, and the temperature is not more than 30°C; The particle size distribution of the slurry is: 3μm≤D50≤5μm, 4μm≤D90≤6μm; The viscosity of the slurry is less than the maximum viscosity that the microchannel reactor can handle.

2. The method for preparing a platinum-carbon catalyst according to claim 1, characterized in that: In step S1, the conductive carbon black dispersion liquid consists of conductive carbon black, polyol, water and surfactant, and has a solid content of 0.1 to 2.0%; The conductive carbon black is selected from one or more of Lion Carbon Black EC600J, EC300J, ECP300JD, Cabot Carbon Black XC-72, BP2000 and carbon nanotubes; The polyol is selected from one or more of propylene glycol, glycerol, and ethylene glycol; The surfactant is selected from one of Tween 40, Tween 80 and Triton X-100.

3. The method for preparing a platinum-carbon catalyst according to claim 2, characterized in that: In step S1, the preparation method of the conductive carbon black dispersion liquid is: after mixing the raw materials, sequentially subjecting them to shear emulsification, ultrasonic dispersion, cell crushing and high-pressure homogenization treatment to obtain the conductive carbon black dispersion liquid.

4. The method for preparing a platinum-carbon catalyst according to claim 1, characterized in that: In step S2, the reaction temperature of the pre-reaction is 10 to 30° C., and the reaction time is 8 to 24 hours.

5. The method for preparing a platinum-carbon catalyst according to claim 1, characterized in that: In step S2, the microchannel mixer used in the pre-reactor is a small-flux microchannel mixer.

6. The method for preparing a platinum-carbon catalyst according to claim 1, characterized in that: In step S3, the heating method of the microchannel reactor is one of heat exchange heating, microwave heating and thermal radiation heating; the reaction temperature is 80-135° C., and the reaction time is 2-10 min; The total reactant flow rate of multiple parallel microchannel reactors is 5 ~ 100L / h.

7. The method for preparing a platinum-carbon catalyst according to claim 1, characterized in that: In step S5, a ceramic membrane filtration system is used to separate the solid and liquid phases.

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