Ternary alloy catalyst for fuel cell cathode and preparation method of ternary alloy catalyst

Abstract

The invention provides a ternary alloy catalyst for a fuel cell cathode, which ensures that a membrane electrode is not subjected to destructive shear stress in a detection process, ensures that the membrane electrode which is qualified through an air tightness test is not subjected to an air tightness problem in subsequent product assembly, and ensures the yield of the assembled product. The device comprises an upper jig plate, the upper jig plate comprises an upper jig plate body, the central area of the lower surface of the upper jig plate body is used for pressing and attaching the upper surface of upper-layer carbon paper of a membrane electrode to be detected to form a first pressing and attaching central area, and a first sealing ring is embedded in the periphery of the first pressing and attaching central area on the lower surface of the upper jig plate body; the lower jig plate comprises a lower jig plate body, the central area of the upper surface of the lower jig plate body is used for pressing and attaching the lower surface of lower layer carbon paper of the membrane electrode to be detected to form a second pressing and attaching central area, and a second sealing ring is embedded in the periphery of the second pressing and attaching central area on the upper surface of the lower jig plate body.

Description

Technical Field

[0001] This invention relates to the technical field of fuel cell manufacturing, specifically to a ternary alloy catalyst for fuel cell cathodes. The invention also provides a method for preparing the ternary alloy catalyst. Background Technology

[0002] Fuel cells offer advantages such as high efficiency, environmental friendliness, and quiet operation. They directly convert chemical energy into electrical energy through electrochemical reactions, resulting in high efficiency and virtually no pollutant emissions. Among them, proton exchange membrane fuel cells (PEMFCs) are widely used in transportation, portable devices, and stationary power sources due to their rapid start-up, high power density, and low operating temperature. As the core component of a PEMFC, the membrane electrode assembly (MEA) determines the cell's performance and lifespan, and the most critical part of the MEA is the catalyst coating membrane (CCM), which directly affects the efficiency and stability of the electrochemical reaction.

[0003] Platinum (Pt) possesses excellent electrocatalytic activity, efficiently catalyzing the oxygen reduction and hydrogen oxidation reactions in fuel cells. These two reactions are crucial steps in generating electricity from fuel cells. Furthermore, as a catalyst, Pt selectively promotes the desired electrochemical reactions, reducing unnecessary side reactions and thus improving the energy conversion efficiency and stability of the fuel cell. However, Pt is a rare and expensive metal. To reduce the amount of Pt used while maintaining its catalytic performance, commercial carbon-supported platinum (Pt / C) catalysts are typically used to prepare CCMs. The active component (Pt nanoparticles) is adsorbed onto the carbon support (C) through physical processes. Compared to the early platinum black catalysts used in fuel cells, the Pt / C catalyst reduces the amount of Pt used by an order of magnitude while maintaining catalytic activity comparable to platinum black. Secondly, the spatial confinement of Pt nanoparticles by the carbon support suppresses the aggregation effect of Pt nanoparticles, which helps extend the lifespan of the Pt / C catalyst. Additionally, the carbon-based support of the Pt / C catalyst is a material with high electrical conductivity, which is beneficial for electron transport.

[0004] However, commercial carbon-supported platinum catalysts have the following drawbacks when used as cathode catalysts in PEMFCs:

[0005] First, for the oxygen reduction reaction, the specific mass activity of the carbon-supported platinum catalyst is only about 0.1 A / mg, which still has room for improvement;

[0006] Second, although carbon-supported platinum-cobalt catalysts can improve the specific activity to 0.17-0.18 A / mg, the transition metal cobalt is prone to oxidation at the high potential of fuel cell operation, and then continuously dissolves in the acidic environment of operation. Therefore, the stability of ordinary platinum-cobalt alloys is not sufficient to meet the application requirements; at the same time, the stability of carbon-supported platinum catalysts also needs to be improved.

[0007] Third, the active component of commercial carbon-supported platinum catalysts is pure platinum nanoparticles. Due to the scarcity of platinum resources, reducing the material cost of catalysts is also one of the future directions for catalyst development.

[0008] Therefore, there is an urgent need to develop a high-performance catalyst for fuel cell cathodes that has promising commercial applications. Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a ternary alloy catalyst for fuel cell cathodes, which exhibits good specific mass activity and promising commercial application prospects.

[0010] A ternary alloy catalyst for a fuel cell cathode, characterized in that it is Pt 15 Co3Ti2 / NPC G，N The catalyst has an active component with a core-shell structure, primarily composed of Pt. 15 The catalyst uses Co3Ti2 as the core and a 2-3 atomic layer shell as the support, with nanoporous carbon NPC as the catalyst carrier. G， N.

[0011] A further feature is that the mass fraction of the metal active component is not less than 20%.

[0012] A method for preparing a ternary alloy catalyst for a fuel cell cathode, characterized by comprising the following steps:

[0013] S1. Add chloroplatinic acid hydrate to ultrapure water to obtain solution A;

[0014] S2. Add cobalt chloride hexahydrate to solution A to obtain solution B;

[0015] S3. Add a hydrochloric acid solution of titanium trichloride (TiCl3) to solution B to obtain a mixed precursor solution;

[0016] S4, To the carrier NPC G，N The mixed precursor solution was added dropwise to obtain C;

[0017] S5. Perform ultrasonic treatment on C to obtain D;

[0018] S6. Freeze D at low temperature to obtain E;

[0019] S7. E is subjected to vacuum biochemical drying to obtain F;

[0020] S8. F is heated and cleaned under a high-temperature H2 / Ar mixed gas flow, then dried and sealed for storage to obtain Pt. 15 Co3Ti2 / NPC G，N catalyst.

[0021] Its further features are:

[0022] In step S1, the chemical formula of chloroplatinic acid hydrate is H₂PtCl₆·nH₂O, and the concentration of H₂PtCl₆ in the obtained solution A is 2–5 × 10⁻⁶. -3 mol;

[0023] In step S2, the chemical formula of cobalt chloride hexahydrate is CoCl2·6H2O, and the content of CoCl2 in solution B is 10-20% of H2PtCl6;

[0024] The amount of TiCl3 in the mixed precursor solution of step S3 is 100-200% of H2PtCl6;

[0025] In step S5, the ultrasonic frequency of the ultrasonic treatment is 30-50kHz, the ultrasonic power is 500-1000W, the temperature of the ultrasonic water bath is 10-15℃, and the ultrasonic time is 30-60 minutes.

[0026] In step S6, the freezing parameters are: freezing temperature of -50 to -70°C and freezing time of 2 to 4 hours;

[0027] In step S7, the vacuum biochemical drying process is as follows: with a fidelity of <10Pa, E is raised by 10°C every 1 to 2 hours from a low temperature, and finally raised to about 80°C and kept at that temperature for 4 to 6 hours.

[0028] In step S8, F is heated under a high-temperature H2 / Ar mixed gas flow of 700℃~900℃ for 2~4 hours, wherein the H2 flow rate is 10~50ml / min and the Ar flow rate is 200~800ml / min, and then cleaned, dried and sealed for storage; the final Pt is obtained. 15 Co3Ti2 / NPC G，N The mass fraction of the metal active component in the catalyst is not less than 20%.

[0029] The ternary alloy catalyst for the fuel cell cathode of this invention is Pt. 15 Co3Ti2 / NPC G，N Catalysts, which enable catalysts to have good specific mass activity and have good commercial application prospects. Detailed Implementation

[0031] A ternary alloy catalyst for the cathode of a fuel cell, which is Pt 15 Co3Ti2 / NPC G，N The catalyst has an active component with a core-shell structure, primarily composed of Pt. 15 The catalyst uses Co3Ti2 as the core and a 2-3 atomic layer shell as the shell, with nanoporous carbon (NPC) as the support. G，NThe mass fraction of the active metal component is not less than 20%.

[0032] A method for preparing a ternary alloy catalyst for a fuel cell cathode includes the following steps:

[0033] The first part involves preparing a mixed precursor solution, which includes steps S1-S3:

[0034] S1. Add chloroplatinic acid hydrate, whose chemical formula is H₂PtCl₆··nH₂O, to ultrapure water to obtain solution A. The concentration of H₂PtCl₆ in solution A is 2–5 × 10⁻⁶. -3 mol;

[0035] S2. Add cobalt chloride hexahydrate, whose chemical formula is CoCl2·6H2O, to solution A to obtain solution B. The content of CoCl2 in solution B is 10-20% of H2PtCl6.

[0036] S3. Add a hydrochloric acid solution of titanium trichloride (TiCl3) to solution B to obtain a mixed precursor solution. The amount of TiCl3 in the mixed precursor solution is 100-200% of H2PtCl6.

[0037] The second part, taking the carrier, includes steps S4-S8:

[0038] S4, To the carrier NPC G，N The mixed precursor solution was added dropwise to obtain C;

[0039] S5. Perform ultrasonic treatment on C to obtain D, wherein the ultrasonic frequency of the ultrasonic treatment is 30-50kHz, the ultrasonic power is 500-1000W, the ultrasonic water bath temperature is 10-15℃, and the ultrasonic time is 30-60 minutes.

[0040] S6. Freeze D at low temperature to obtain E. The freezing temperature is -50 to -70℃ and the freezing time is 2 to 4 hours.

[0041] S7. E is subjected to vacuum biochemical drying to obtain F. During the vacuum biochemical drying process, the accuracy is <10Pa. E is raised from a low temperature by 10°C every 1 to 2 hours, and finally raised to about 80°C and kept at a constant temperature for 4 to 6 hours.

[0042] S8. Heat F in a H2 / Ar mixed gas flow at a high temperature of 700℃~900℃ for 2~4 hours, wherein the H2 flow rate is 10~50ml / min and the Ar flow rate is 200~800ml / min, and then clean, dry and seal for storage.

[0043] The final Pt 15 Co3Ti2 / NPCG，N The mass fraction of the metal active component in the catalyst is not less than 20%.

[0044] In step S8, F is heated under a high-temperature H2 / Ar mixed gas flow of 700℃~900℃ for 2~4 hours, wherein the H2 flow rate is 10~50ml / min and the Ar flow rate is 200~800ml / min, and then cleaned, dried and sealed for storage; the final Pt is obtained. 15 Co3Ti2 / NPC G，N The mass fraction of the metal active component in the catalyst is not less than 20%.

[0045] The Pt of this invention was prepared using an electrochemical workstation and a three-electrode system. 15 Co3Ti2 / NPC G，N The catalyst (20% metal content) was used as a specific example, the commercial Pt3Co / C catalyst (20% metal content) was used as a comparative example 1, and the commercial Pt / C (20% platinum content) was used as a comparative example 2. The catalytic activity of the oxygen reduction reaction was characterized by experiments.

[0046] Electrochemical tests show that the specific mass activity of the catalyst in the specific embodiment is 3 times that of the Pt / C catalyst and 70% higher than that of the Pt3Co / C catalyst.

[0047] From the perspective of catalyst design principles, catalysts used for oxygen reduction reactions need to have moderate adsorption strength; on the one hand, so that reactants can be stably adsorbed and participate in the reaction; on the other hand, so that products can be desorbed in a timely manner.

[0048] According to the d-band center model theory, +1.88 eV is the ideal value for the binding energy between oxygen and the catalyst surface. An adsorption energy of +1.88 eV can form stable adsorption, forming a key oxygen-containing intermediate, and the adsorption strength is not too strong, avoiding the blockage of active sites on the catalyst surface. It should be noted that the smaller the binding energy between a metal and oxygen, the easier it is for the metal to adsorb oxygen. Since the binding energy between Pt and O is +1.6 eV, which is lower than the ideal value of +1.88 eV, Pt has a slightly stronger adsorption effect on oxygen. Therefore, it is necessary to introduce a second or third element to appropriately suppress the adsorption strength of Pt on oxygen-containing intermediates. This is the core starting point for the preparation of highly active fuel cell cathode catalysts in this invention.

[0049] Due to the slight lattice contraction of the Pt3Co alloy, when the lattice of the platinum-cobalt alloy contracts and becomes shorter, the overlap of Pt's d orbitals increases, resulting in a wider d band width and a downward shift of the d band center. This weakens the adsorption strength of Pt with oxygen-containing intermediates, which is the key to improving the specific mass activity of Pt3Co.

[0050] This invention introduces a third metallic element, Ti, into the Pt3Co alloy. By controlling the amount of Ti precursor added, the d-band center position of Pt can be more precisely controlled, appropriately weakening the binding energy between platinum atoms and oxygen-containing intermediates, bringing it closer to the ideal value of +1.88 eV. Through repeated experiments, the inventors determined that the atomic ratio n(Pt):n(Co):n(Ti) = 15:3:2 is the atomic ratio with the highest catalytic activity for the oxygen reduction reaction, based on the Pt3Co alloy. This is the Pt alloy prepared by this invention. 15 Co3Ti2 / NPC G，N The reason why catalysts have high specific mass activity.

[0051] Evaluation of Pt through accelerated decay test 15 Co3Ti2 / NPC G，N Durability of catalysts (20% metal content), commercial Pt3Co / C catalysts (20% metal content), and commercial Pt / C (20% platinum content); electrolyte solution was nitrogen-saturated 0.5M sulfuric acid solution, scan rate was 100 mV / s, and scan potential range was 0.6 V. RHE -1.05V RHE The number of scans is 20,000.

[0052] Similar to the BOL specific mass activity test method, the EOL specific mass activity of the three catalysts was measured sequentially, and the results are listed in Table 1;

[0053]

[0054] Table 1

[0055] After repeated experiments, the inventors selected high-temperature treatment (700–900℃) to reduce Pt, Co, and Ti elements. Under high temperature, platinum is more easily segregated into Pt. 15 The surface of Co3Ti2 forms a shell several atomic layers thick, creating a unique core-shell structure. This platinum shell effectively prevents the dissolution of transition metals Co and Ti, exhibiting better stability under acidic conditions. This is the Pt prepared in this invention. 15 Co3Ti2 / NPC G，N The catalyst exhibits good durability due to both high-temperature treatment and NPC. G，N The support also allows for effective control over the catalyst particle size.

[0056] The Pt prepared in this invention was studied using an electrochemical workstation and a three-electrode system. 15 Co3Ti2 / NPC G，NCarbon monoxide removal tests were conducted on catalysts (20% metal content), commercial Pt3Co / C catalysts (20% metal content), and commercial Pt / C (20% platinum content) to calculate the active area of ​​the hydrogen region, denoted as ECSA. CO ;

[0057] The Pt prepared in this invention was studied using an electrochemical workstation and a three-electrode system. 15 Co3Ti2 / NPC G，N Blank cyclic voltammetry curves were performed on the catalyst (20% metal content), commercial Pt3Co / C catalyst (20% metal content), and commercial Pt / C (20% platinum content) to calculate the active area in the hydrogen region, denoted as ECSA. H ;

[0058] The results are shown in Table 2:

[0059] <![CDATA[ECSA CO

m 2 / g

m 2 / g

[0060] Table 2

[0061] As can be seen from Table 2, through (ECSA) CO / ECSA H It can be seen that Pt 15 Co3Ti2 / NPC G，N The ratio is 1.43, very close to 1.5, which proves that the ternary alloy Pt 15 The presence of a platinum surface layer in Co3Ti2.

[0062] In summary, the Pt provided by this invention 15 Co3Ti2 / NPC G，N The catalyst is a core-shell structured, highly active, long-life ternary alloy catalyst with promising commercial application prospects.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0064] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A ternary alloy catalyst for a fuel cell cathode, wherein the catalyst is Pt 15 Co3Ti2 / NPC G，N The catalyst has an active component with a core-shell structure, primarily composed of Pt. 15 The catalyst uses Co3Ti2 as the core and a 2-3 atomic layer shell as the support, with nanoporous carbon NPC as the catalyst carrier. G，N .

2. The ternary alloy catalyst for a fuel cell cathode according to claim 1, characterized in that: The mass fraction of the active metal component is not less than 20%.

3. A method for preparing a ternary alloy catalyst for a fuel cell cathode as described in claim 1 or 2, characterized in that, It includes the following steps: S1. Add chloroplatinic acid hydrate to ultrapure water to obtain solution A; S2. Add cobalt chloride hexahydrate to solution A to obtain solution B; S3. Add a hydrochloric acid solution of titanium trichloride (TiCl3) to solution B to obtain a mixed precursor solution; S4, To the carrier NPC G，N The mixed precursor solution was added dropwise to obtain C; S5. Perform ultrasonic treatment on C to obtain D; S6. Freeze D at low temperature to obtain E; S7. E is subjected to vacuum biochemical drying to obtain F; S8. F is heated and cleaned under a high-temperature H2 / Ar mixed gas flow, then dried and sealed for storage to obtain Pt. 15 Co3Ti2 / NPC G，N catalyst.

4. The method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 3, characterized in that: In step S1, the chemical formula of chloroplatinic acid hydrate is H₂PtCl₆·nH₂O, and the concentration of H₂PtCl₆ in the obtained solution A is 2–5 × 10⁻⁶. -3 mol.

5. The method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 4, characterized in that: In step S2, the chemical formula of cobalt chloride hexahydrate is CoCl2·6H2O, and the content of CoCl2 in solution B is 10-20% of H2PtCl6.

6. The method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 3, characterized in that: The amount of TiCl3 in the mixed precursor solution of step S3 is 100-200% of H2PtCl6.

7. The method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 3, characterized in that: In step S5, the ultrasonic frequency of the ultrasonic treatment is 30-50kHz, the ultrasonic power is 500-1000W, the temperature of the ultrasonic water bath is 10-15℃, and the ultrasonic time is 30-60 minutes.

8. The method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 3, characterized in that: In step S6, the freezing parameters are: freezing temperature of -50 to -70°C and freezing time of 2 to 4 hours.

9. The method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 3, characterized in that: In step S7, the vacuum biochemical drying process is as follows: with a fidelity of <10Pa, E is increased by 10°C every 1 to 2 hours from a low temperature, and finally raised to about 80°C and kept at a constant temperature for 4 to 6 hours.

10. A method for preparing a ternary alloy catalyst for a fuel cell cathode according to claim 3, characterized in that: In step S8, F is heated under a high-temperature H2 / Ar mixed gas flow of 700℃~900℃ for 2~4 hours, wherein the H2 flow rate is 10~50ml / min and the Ar flow rate is 200~800ml / min, and then cleaned, dried and sealed for storage; the final Pt is obtained. 15 Co3Ti2 / NPC G，N The mass fraction of the metal active component in the catalyst is not less than 20%.

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