Method for producing electrode catalyst for fuel cell

Abstract

To provide a method of continuously producing a palladium core platinum shell supported carbon fuel cell catalyst by directly reacting a platinum compound aqueous solution and an aqueous suspension of the palladium supported carbon powder by preventing deposition on a transfer path inner wall due to precipitation of the palladium supported carbon powder having relatively large specific gravity.SOLUTION: The loss of raw material associated with transfer can be reduced by: using first mixing means to mix a platinum compound aqueous solution and an aqueous suspension of a palladium supported carbon powder so as to form a mixed suspension; using second mixing means to mix the mixed suspension and a gas so as to form a slug flow in which these mixed suspension and gas flow alternately; and employing means of sequentially transferring the slug flow to a reaction vessel so as to cause reaction at a prescribed temperature.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for continuously producing an electrode catalyst for a fuel cell. [Background technology]

[0002] Fuel cells are expected to be an energy system that can generate electricity without emitting carbon dioxide when hydrogen is used as fuel. Polymer electrolyte fuel cells (PEFCs), which operate at low temperatures, are being developed as generators to be installed in mobile vehicles, including automobiles. Reducing the cost of these PEFC systems is a challenge. For this reason, there is a need to reduce the amount of platinum used in the oxygen electrode (cathode), which uses a large amount of expensive platinum, in other words, to develop a cathode catalyst with high oxygen reduction catalytic activity.

[0003] Patent Document 1 describes a catalyst in which platinum particles are finely and highly dispersed on a carbon support to improve the platinum utilization rate, thereby improving the specific surface area per platinum mass (electrochemically active surface area, ECSA). Patent Document 2 and Non-Patent Document 1 describe alloy catalysts in which the activity per active site (area specific activity, SA) is improved. Patent Document 3, Patent Document 4, and Non-Patent Document 2 describe core-shell catalysts as catalysts that can simultaneously improve ECSA and SA.

[0004] Core-shell catalysts are ideal catalysts because they can simultaneously improve ECSA and SA, but because they require atomic-level control, they have been synthesized in small-scale batch reactors during the research and development stage. However, when trying to achieve the production volumes required in the future, it becomes difficult to control the process inside the reactor when scaled up using the batch method, which increases production costs, so new production methods are needed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-94529 [Patent Document 2] Patent Publication No. 2018-6107 [Patent Document 3] U.S. Patent 7,691,780 [Patent Document 4] Patent Publication No. 2020-145154 [Non-Patent Document 1] Journal of The Electrochemical Society, 146 (10) 3750-3756 (1999) [Non-patent document 2] J. AM. CHEM. SOC., 131 (47) 17298-17302 (2009) Summary of the Invention [Problem to be solved by the invention]

[0006] In the production of fuel cell catalysts that support a core-shell catalyst on the surface of carbon powder, particularly the method of directly reacting an aqueous suspension of palladium-supported carbon powder with an aqueous platinum compound to form a platinum shell on the surface of palladium, production is carried out using a batch process that does not require the transfer of the suspension, making it easier to manage the suspension and reaction. However, to increase production volume, it is necessary to increase the size of the batch equipment or the number of batch equipment, which significantly increases capital investment costs. Furthermore, when using a larger batch equipment, it is difficult to uniformize the production conditions. Furthermore, when attempting to carry out the above reaction continuously, the relatively heavy palladium-supported carbon powder settles and adheres to the inner walls of the transfer channel, causing problems with the transfer of the aqueous suspension.

[0007] The object of the present invention is to provide a transport route by sedimentation of palladium-loaded carbon powder, which has a relatively high specific gravity. The present invention provides a method for continuously producing a palladium core / platinum shell-supported carbon catalyst by preventing adhesion to the inner wall and directly reacting an aqueous suspension of palladium-supported carbon powder with an aqueous platinum compound solution. [Means for solving the problem]

[0008] The inventors solved the above-mentioned problem of impeded transport of the aqueous suspension by mixing the aqueous suspension from a second tank containing the aqueous suspension with an aqueous platinum compound solution using a first mixer at a linear velocity of 0.13 m / s or more to prevent adhesion to the inner walls of the transport path due to settling of the palladium-supported carbon powder in the aqueous suspension. Next, the mixed suspension and gas are mixed using a second mixer to form a slug flow in which the mixed suspension and gas flow alternately. They then discovered that by sequentially transferring the mixed suspension to at least three reaction tanks set at different temperatures and reacting at the predetermined reaction temperatures, a platinum shell is formed on the surface of the palladium, making it possible to continuously produce a palladium core-platinum shell-supported carbon catalyst.

[0009] Therefore, the present invention provides the following aspects. A step (step 1) of preparing an aqueous platinum compound solution in a first tank by dissolving a platinum compound in an acidic aqueous solution; a step (step 2) of preparing an aqueous suspension of palladium-supported carbon powder in a second tank by suspending palladium-supported carbon powder in pure water; a step (step 3) of sequentially removing a portion of the aqueous suspension from the second tank and imparting kinetic energy to the aqueous suspension at a linear velocity equal to or greater than a predetermined velocity; a step (step 4) of mixing the aqueous platinum compound solution removed from the first tank with a portion of the aqueous suspension to which kinetic energy has been applied, using a first mixing means, to obtain a mixed suspension; a step (step 5) of mixing the mixed suspension obtained in step 4 with a gas by a second mixing means to form a slug flow in which the mixed suspension and the gas flow alternately; This is a method for continuously producing a palladium core-platinum shell-supported carbon catalyst, comprising: a step (step 6) of continuously supplying the slug flow formed in step 5 to the inlet of a first reaction vessel in N-stage continuous-tank reactors (N=3 or more) connected in series, reacting the slug flow in each of the N-stage reactors in turn, and continuously removing the slug flow from the outlet of the Nth reactor, thereby forming a platinum shell on the surface of the palladium.

[0010] In addition, in the above configuration, In the above step 3, the second tank is provided with a circulation path that exits from a lower part or a side part of the tank and returns to an upper part or a side part of the tank, and a liquid feed pump that is provided midway along the circulation path; The liquid feed pump may be configured to forcibly circulate the aqueous suspension in the circulation path with kinetic energy at a linear velocity equal to or greater than a predetermined velocity.

[0011] In addition, in the above configuration, In the step 4, the aqueous suspension is taken out through a branch path branching off from the circulation path, The aqueous platinum compound solution removed from the first tank and the water suspension removed from the first tank may be mixed to obtain a mixed suspension.

[0012] In addition, in the above configuration, In the above step 6, the inlet of the reaction tank in a predetermined stage (n-1 stage) is located at a lower position than the outlet of the reaction tank in the preceding stage ((n-2) stage), and the outlet of the reaction tank in the predetermined stage (n-1 stage) is located at a higher position than the inlet of the reaction tank in the subsequent stage (n stage), The set temperature of the reaction tank in a given stage (n-1 stage) may be higher than the set temperature of the reaction tank in the preceding stage ((n-2) stage) and lower than the set temperature of the reaction tank in the subsequent stage (n stage). [Effects of the Invention]

[0013] According to the present invention, it is possible to prevent the relatively heavy palladium-supported carbon powder from settling on the inner walls of the transport path during transport.The object of the present invention is to provide a method for continuously producing a palladium-core, platinum-shell-supported carbon catalyst by preventing the relatively heavy palladium-supported carbon powder from settling and adhering to the inner walls of the transport path, and by directly reacting an aqueous suspension of palladium-supported carbon powder with an aqueous platinum compound solution. DETAILED DESCRIPTION OF THE INVENTION

[0014] The method for producing an electrode catalyst for a fuel cell according to the present invention will be described in detail below.

[0015] The present invention includes a step (step 1) of preparing an aqueous platinum compound solution in a first tank by dissolving a platinum compound in an acidic aqueous solution.

[0016] Examples of the acidic aqueous solution include a 0.05 to 0.5 mol / L aqueous solution of hydrochloric acid, sulfuric acid, and nitric acid, etc. A concentration of 0.1 to 0.2 mol / L is preferably used.

[0017] The platinum compound used here is a compound that can form a platinum shell on the surface of palladium under the conditions described below, and examples thereof include dinitrodiammine platinum, chloroplatinic acid, potassium chloroplatinate, and platinum chloride. The temperature at which the platinum compound is dissolved in the acidic aqueous solution is 5 to 60°C, preferably 10 to 30°C. The applicable platinum concentration is 0.008 to 1.42 g / L, and preferably 0.069 to 0.426 g / L.

[0018] Here, the platinum compound aqueous solution can be prepared in the first tank by dissolving the platinum compound in an acidic aqueous solution in a location different from the first tank and then pouring the resulting platinum compound aqueous solution into the first tank, or alternatively, the platinum compound can be dissolved in an acidic aqueous solution in the first tank and then prepared in the first tank.

[0019] The present invention includes a step (step 2) of preparing an aqueous suspension of palladium-supported carbon powder in a second tank by suspending palladium-supported carbon powder in pure water.

[0020] The carbon powder used in the present invention is not particularly limited, and may be a carbon support used to support platinum in the production of an electrode catalyst, preferably carbon, specifically carbon black such as furnace black, channel black, and acetylene black.

[0021] The palladium-supported carbon powder is advantageously one in which 10 to 60 wt % of 3 to 10 nm palladium particles are supported on the surface of the carbon powder, and preferably 30 to 50 wt % of 4 to 7 nm palladium particles are supported.

[0022] The concentration of palladium-supported carbon in the aqueous suspension can be 0.25 to 4.0 g / L, and preferably 1.0 to 2.0 g / L.

[0023] Here, the aqueous suspension of palladium-supported carbon powder can be prepared in the second tank by suspending palladium-supported carbon powder in pure water in a location different from the second tank and then pouring the resulting aqueous suspension into the second tank. Alternatively, the aqueous suspension of palladium-supported carbon powder can be prepared in the second tank by suspending palladium-supported carbon powder in pure water in the second tank. Here, to prevent the palladium-supported carbon powder from settling in the second tank, the aqueous suspension can be stirred in the second tank by rotating a stirring blade at 0 rpm to 600 rpm, preferably 300 rpm to 500 rpm.

[0024] The present invention further comprises a step (step 3) of sequentially withdrawing a portion of the aqueous suspension from the second tank and applying kinetic energy to the aqueous suspension at a linear velocity equal to or greater than a predetermined velocity; and a step (step 4) of mixing the aqueous platinum compound solution removed from the first tank with a portion of the water suspension to which kinetic energy has been applied, using a first mixing means, to obtain a mixed suspension.

[0025] The above step 3 may be carried out by any means that allows the aqueous suspension to be sent to the next step without settling.

[0026] For example, in the above step 3, the aqueous suspension is sent to the next step at a linear velocity of at least a predetermined velocity, for example, at least 0.13 m / s.

[0027] In the step 3, the second tank is provided with a circulation path that exits from a lower part or a side part of the tank and returns to an upper part or a side part of the tank, and a liquid transfer pump that is provided in the middle of the circulation path; The liquid feed pump can be configured to forcibly circulate the aqueous suspension in the circulation path with kinetic energy at a linear velocity equal to or greater than a predetermined velocity.

[0028] The circulation path is a path for extracting an aqueous suspension of palladium-loaded carbon powder from the bottom or side of the second tank using a liquid transfer pump and injecting it into the top or side of the second tank to circulate the liquid. Here, a capillary tube can be used as the circulation path. The capillary tube is preferably made of a material that is resistant to carbon adhesion, such as a fluororesin such as PFA or PTFE, or a corrosion-resistant metal material such as glass or titanium. The inner diameter of the capillary tube can be φ4 to 12 mm, and preferably φ4 to 8 mm.

[0029] The linear flow velocity in the circulation path is, for example, 0.13 m / s or more. If the linear flow velocity is less than 0.13 m / s, sufficient kinetic energy is not imparted to the palladium-loaded carbon powder, causing the palladium-loaded carbon powder to settle on the inner wall of the circulation path (e.g., a capillary).

[0030] In step 4, the aqueous suspension may be taken out through a branch path branching off from the circulation path, and the aqueous platinum compound solution taken out from the first tank may be mixed with the aqueous suspension to obtain a mixed suspension.

[0031] The branch path can be a thin tube. The thin tube is preferably made of a material that is resistant to carbon adhesion, such as a fluororesin such as PFA or PTFE, or a corrosion-resistant metal material such as glass or titanium. The inner diameter of the thin tube can be φ4 to 12 mm, and preferably φ4 to 8 mm. In addition, when the aqueous suspension is taken out from a branch path branching off from the circulation path, a pump may be used to take out the suspension.

[0032] When mixing the aqueous platinum compound solution and the water suspension, a first mixing means called a tube connector, connection joint, or hose fitting, which has a T-shaped or Y-shaped external shape and is made of a fluororesin such as PFA or PTFE, can be used.

[0033] The present invention includes a step (step 5) of mixing the mixed suspension obtained in step 4 with a gas by a second mixing means to form a slug flow in which the mixed suspension and the gas flow alternately.

[0034] When mixing the mixed suspension and the gas to form a slug flow in which the mixed suspension and the gas flow alternately, a second mixing means called a tube connector, connection joint, or hose fitting, which has a Y-shaped or T-shaped external shape and is made of a fluororesin such as PFA or PTFE, can be used.

[0035] When the mixed suspension and gas are introduced into the mixing means, the mixture is mixed due to the surface tension of the mixed suspension and gas. A slug flow is formed in which the suspension and the gas flow alternately, and the gas can be, for example, air, nitrogen, or an inert gas such as argon.

[0036] In the slug flow, the mixed suspension and the gas flow alternately. Within the mixed suspension (section) separated by the gas, there are regions where the flow velocity is relatively fast in the center of the capillary tube and relatively slow near the inner wall of the capillary tube. However, because the section is separated by the gas, spontaneous internal convection occurs within the region, and even if the overall speed of the slug flow is slower than the predetermined linear velocity, a substantial flow velocity can be ensured. Therefore, the palladium-loaded carbon powder does not settle on the inner wall of the liquid-transporting capillary tube, which serves as the transport path to the first reaction vessel in the next step.

[0037] Capillary tubes can be used for the piping between step 4 and step 5, and between step 5 and step 6. The material of the capillary tube is preferably a fluororesin such as PFA or PTFE, which has almost no carbon adsorption, and the inner diameter of the capillary tube can be φ4 to 12 mm, preferably φ4 to 8 mm.

[0038] By providing steps 3 to 5, the raw material that is initially introduced can be transferred to the subsequent step 6 without settling, settling down, adhering or remaining along the route.

[0039] The present invention includes a step (step 6) of continuously supplying the slug stream formed in step 5 to the inlet of a first reaction vessel in N-stage continuous-tank reactors (N=3 or more) connected in series, reacting the slug stream in each of the N stages in turn, and continuously removing the slug stream from the outlet of the Nth reactor, thereby forming a platinum shell on the surface of the palladium.

[0040] A continuous tank reactor refers to a reactor in which a tank-type reactor is operated continuously. The reaction tank of the reactor may be a stirred tank that can heat the contents inside the tank. The capacity of the reaction tank can be selected as desired, taking into account the amount of catalyst produced. For example, it can be 0.5 L to 5 L. The reaction fluid inside the tank is thoroughly mixed by stirring, and the temperature and concentration of the reaction fluid become approximately constant inside the tank before being discharged from the outlet of the reaction tank.

[0041] In the present invention, the reaction temperature conditions used in conventional batch reactors, i.e., the thermal history of heating a mixed suspension from room temperature to a predetermined temperature, are replaced by three or more stages of reactors with preset temperatures, thereby ensuring continuous production.

[0042] The set temperatures of multiple reaction vessels can be set so that the temperature of a subsequent reaction vessel is higher than or equal to the set temperature of a previous reaction vessel. For example, in the case of three reaction vessels, the temperatures can be set so that the first reaction vessel is 50°C, the second reaction vessel is 65°C, and the third reaction vessel is 80°C. Also, for example, in the case of four reaction vessels, the temperatures can be set so that the first reaction vessel is 50°C, the second reaction vessel is 65°C, and the third and fourth reaction vessels are 80°C, thereby making it possible to double the residence time at 80°C compared to the residence time at other temperatures.

[0043] For example, three reactors each have an inlet and an outlet. The inlet of the second reactor (second reactor) is connected to the outlet of the first reactor (first reactor), and the outlet of the second reactor (second reactor) is connected to the inlet of the third reactor. These connections may be direct or via a pump.

[0044] Capillary tubes can be used for the piping between the reaction vessels in step 6. The material of the capillary tubes is preferably a fluororesin such as PFA or PTFE, which has almost no carbon adsorption, and the inner diameter of the capillary tubes can be φ4 to 12 mm, preferably φ4 to 8 mm.

[0045] A slug flow consisting of an alternating flow of mixed suspension and gas is introduced into the inlet of the first reaction vessel and transferred sequentially to N reaction vessels.

[0046] The mixed suspension is heated to a predetermined temperature in multiple reaction vessels, and the palladium on the surface of the palladium particles of the palladium-supported carbon powder is dissolved (oxidized), platinum is precipitated (reduced), and a platinum shell is formed on the surface of the palladium particles, resulting in a palladium core-platinum shell-supported carbon catalyst.

[0047] In the above step 6, the inlet of the reaction tank at a predetermined stage (n-1 stage) may be located lower than the outlet of the reaction tank at the preceding stage ((n-2) stage), the outlet of the reaction tank at the predetermined stage (n-1 stage) may be located higher than the inlet of the reaction tank at the subsequent stage (n stage), and the set temperature of the reaction tank at the predetermined stage (n-1 stage) may be higher than the set temperature of the reaction tank at the preceding stage ((n-2) stage) and lower than the set temperature of the reaction tank at the subsequent stage (n stage).

[0048] Specifically, the mixed suspension can be transferred between reactors by utilizing the phenomenon in which the mixed suspension overflowing from the top of a reactor falls due to gravity to the next reactor. For example, the inlet of the second reactor can be installed lower than the outlet of the first reactor so that the mixed suspension flows down from the first reactor to the second reactor at an inclination angle of 30 to 60 degrees.

[0049] Furthermore, the set temperatures of the multiple reaction vessels are set so that the temperature of the subsequent reaction vessel is higher than the set temperature of the preceding reaction vessel, thereby minimizing the number of vessels and replacing the reaction temperature conditions used in conventional batch vessels, i.e., the thermal history of heating the mixed suspension from room temperature to a predetermined temperature.

[0050] In the first reaction tank, the mixed suspension is heated to a set temperature I, and the gas for forming the slug flow (for example, air, nitrogen, or an inert gas such as argon) is separated and discharged. [Example]

[0051] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0052] Example 1 An aqueous solution of platinum compounds was prepared in the first tank (volume 2 L) by dissolving 0.57 g of K2PtCl4 as a platinum source per 1 L of 0.1 mol / L H2SO4 aqueous solution. The temperature was set to room temperature.

[0053] An aqueous suspension (concentration of palladium-loaded carbon in the aqueous suspension was 2 g / L) was prepared in a second tank (volume 2 L) by dispersing 2 g of palladium-loaded carbon (Pd / C) with 46 wt.% Pd nanoparticles (average particle size: 5.3 nm) per 1 L of ultrapure water. The aqueous suspension was stirred at 450 rpm with a stirring blade to prevent settling in the second tank.

[0054] The aqueous suspension was circulated from the second tank using a pump at 400 ml / min (linear velocity: 0.53 m / s).The aqueous suspension was then branched off from the circulation path (capillary tube: inner diameter 4 mm) and collected at 1 L / h.Meanwhile, the aqueous platinum compound solution was collected from the first tank at 1 L / h and mixed in the T-shaped capillary tube to obtain a mixed suspension.

[0055] The mixed suspension and air were then mixed in a narrow tube to form a slug flow in which the mixed suspension and the gas flowed alternately.

[0056] Next, a four-stage continuous tank reactor connected in series was used, and the insides of the four reaction tanks (volume 0.5 L) were filled with pure water. The first reaction tank was kept at 50°C, the second reaction tank at 60°C, the third reaction tank at 70°C, and the fourth reaction tank at 80°C. In this state, the mixed suspension and gas were alternately introduced into the first reaction tank. The supply of slug flow into the reactor was started.

[0057] In a continuous reactor reaction, the inlet of the reactor at a given stage (n-1 stage) was set at a lower position than the outlet of the reactor at the previous stage ((n-2) stage), and the outlet of the reactor at a given stage (n-1 stage) was set at a higher position than the inlet of the reactor at the subsequent stage (n stage). In addition, the reactors were connected directly to the outlet and inlet without using a pump.

[0058] After reaching a steady state, the suspension obtained from the outlet of the fourth reactor was collected, separated into solid and liquid by filtration, washed with pure water, and then dried to obtain 2 g of palladium core platinum shell catalyst per hour.

[0059] In Example 1, it was confirmed that a palladium core-platinum shell-supported carbon catalyst could be continuously produced for 5 hours by continuously adding an aqueous platinum compound solution to the first tank and an aqueous suspension to the second tank. If the additions were continued, continuous production for even longer periods would be possible.

[0060] (Comparative Example 1) In Comparative Example 1, a palladium core-platinum shell-supported carbon was produced in a batch process.

[0061] In a 1 L separable flask, 300 mg of palladium-loaded carbon (palladium loading rate: 46 wt.%, average palladium particle size: 5.2 nm) was dispersed in 500 mL of 0.1 mol / L sulfuric acid solution containing one atomic layer of K2PtCl4, the platinum compound used as the platinum shell raw material, to obtain a suspension. The suspension was heated from room temperature to 70 °C and held for 3 hours. The suspension was filtered, washed, and dried to obtain 0.3 g of palladium-core platinum-shell catalyst.

[0062] (Comparative Example 2) Comparative Example 2 is a liquid transfer method without liquid circulation or slug flow. In this comparative example, the palladium-loaded carbon powder settled on the inner wall of the capillary tube that transfers the liquid to the reaction tank, making continuous treatment impossible.

[0063] The palladium core platinum shell catalysts of Example and Comparative Example 1 were evaluated by electrochemical measurement, and the results are shown in Table 1. [Table 1]

[0064] As can be seen from Table 1, the ORR activity of the palladium core-platinum shell-supported carbon of Comparative Example 1, which was produced batchwise, is equivalent to that of Example 1, and it is clear that the present invention is effective as a continuous production method for a palladium core-platinum shell-supported carbon catalyst.

Claims

1. A step (step 1) of preparing an aqueous platinum compound solution in a first tank by dissolving a platinum compound in an acidic aqueous solution; a step (step 2) of preparing an aqueous suspension of palladium-supported carbon powder in a second tank by suspending palladium-supported carbon powder in pure water; a step (step 3) of sequentially removing a portion of the aqueous suspension from the second tank and imparting kinetic energy to the aqueous suspension at a linear velocity equal to or greater than a predetermined velocity; a step (step 4) of mixing the aqueous platinum compound solution removed from the first tank with a portion of the aqueous suspension to which kinetic energy has been applied, using a first mixing means, to obtain a mixed suspension; a step (step 5) of mixing the mixed suspension obtained in step 4 with a gas by a second mixing means to form a slug flow in which the mixed suspension and the gas flow alternately; Step 6: continuously supplying the slug stream formed in Step 5 to the inlet of a first reactor in N-stage continuous-tank reactors (N=3 or more) connected in series, reacting the slug stream in each of the N-stage reactors in turn, and continuously removing the slug stream from the outlet of the Nth reactor, thereby forming a platinum shell on the surface of the palladium; A method for continuously producing a palladium core-platinum shell-supported carbon catalyst, comprising:

2. In the above step 3, the second tank is provided with a circulation path that exits from a lower part or a side part of the tank and returns to an upper part or a side part of the tank, and a liquid feed pump that is provided midway along the circulation path; 2. The method for continuously producing a palladium core-platinum shell-supported carbon catalyst according to claim 1, wherein the liquid feed pump forcibly circulates the aqueous suspension in the circulation path with kinetic energy at a linear velocity equal to or greater than a predetermined velocity.

3. In the step 4, the aqueous suspension is taken out through a branch path branching off from the circulation path, 3. The method for continuously producing a palladium core-platinum shell-supported carbon catalyst according to claim 2, wherein the aqueous platinum compound solution removed from the first tank and the water suspension removed from the second tank are mixed to obtain a mixed suspension.

4. In the above step 6, the inlet of the reaction tank in a predetermined stage (n-1 stage) is located lower than the outlet of the reaction tank in the preceding stage ((n-2) stage), and the outlet of the reaction tank in the predetermined stage (n-1 stage) is located higher than the inlet of the reaction tank in the subsequent stage (n stage), The set temperature of the reaction tank in a predetermined stage (n-1 stage) is higher than the set temperature of the reaction tank in the previous stage ((n-2) stage) and lower than the set temperature of the reaction tank in the subsequent stage (n stage).

4. A method for continuously producing a palladium core-platinum shell-supported carbon catalyst according to claim 1.

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