A composite carbon-supported PtCoRu catalyst, its preparation method and application

Abstract

This invention provides a composite carbon support PtCoRu catalyst, its preparation method, and its application, while solving the problems of poor activity and durability at the working potential of existing catalysts and poor corrosion resistance of carbon supports for high-potential catalysts. The preparation method includes: (1) adding the carbon support to a mixture of deionized water and alcohol and stirring to form a carbon slurry, adding a cerium and tungsten precursor solution to the carbon slurry, and reducing it with a dual reducing agent to obtain a W-Ce-C composite carbon support; (2) adding the composite support obtained in (1) to a mixture of DMF and alcohol and stirring to form a carbon slurry, then adding platinum, cobalt, and a small amount of ruthenium precursor, and preparing a PtCoRu / W-Ce-C alloy catalyst by hydrothermal reaction. The catalyst prepared by this invention has a small difference between the active metal loading and the theoretical loading, and exhibits high catalytic activity and stability as a cathode catalyst for proton exchange membrane fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell catalyst technology, and relates to a composite carbon support PtCoRu catalyst, its preparation method and application, especially a method for preparing a PtCoRu / W-Ce-C cathode catalyst for proton exchange membrane fuel cells. Technical Background

[0002] Proton exchange membrane fuel cells (PEMFCs) are highly efficient and clean energy conversion devices that generate electricity from hydrogen without producing carbon dioxide or other emissions. PEMFCs offer advantages such as high power density, high specific energy, and environmental friendliness, making them ideal power sources for electric vehicles, stationary and portable devices. The oxygen reduction reaction (ORR) at the PEMFC cathode is considered the limiting half-cell reaction for fuel-to-electricity conversion. ORR is a core reaction in new energy technologies including fuel cells and metal-air batteries, requiring expensive and scarce precious metal platinum as a catalyst to overcome the relatively sluggish oxygen reduction reaction kinetics. Therefore, developing low-cost, highly active, and long-life cathode oxygen reduction catalysts is crucial for the development of energy technologies such as fuel cells. Currently, Pt-based alloys are recognized as the next-generation ORR catalyst, but stability remains the biggest obstacle to their practical application. Catalyst surface engineering, constructing core-shell catalysts and doping / alloying with other highly stable precious metal elements, or designing novel nanocrystalline-support composite materials are considered effective methods to address this problem.

[0003] Cost, performance, and durability are the three major obstacles to the commercialization of proton exchange membrane fuel cells (PEMFCs). Durability refers to the ability of a material or product to resist long-term damage from both its own inherent properties and environmental factors. Typically, localized and overall anode undergassing caused by start-up / shutdown, load changes, operational errors, and external environmental factors are significant factors accelerating fuel cell degradation. When a partial hydrogen undergassing occurs on the anode side during start-up / shutdown, a high potential exceeding 1.3V is generated at the cathode, accelerating carbon support corrosion. Carbon support corrosion causes the agglomeration and growth of precious metal catalyst particles, reducing the active sites for electrochemical reactions. Furthermore, carbon support corrosion adversely affects the transport of protons, electrons, and gases, leading to irreversible performance loss. To avoid hydrogen undergassing and high potential and to monitor voltage changes in real time, fuel cell systems typically employ costly voltage monitors (CVMs). Removing costly system components such as CVMs simplifies the fuel cell system and significantly reduces costs. Therefore, modifying the carbon support to provide superior high-potential durability allows for the development of increasingly simplified fuel cell systems that prevent high potentials, not only efficiently improving the performance of PEMFCs but also significantly reducing their application costs.

[0004] Platinum-cobalt alloy catalysts are considered the most promising cathode catalysts for PEMFCs, exhibiting superior catalytic activity and resistance to poisoning compared to platinum-carbon catalysts. Preparing high-performance platinum-cobalt catalysts to replace platinum-carbon catalysts is expected to significantly reduce platinum usage, thereby lowering fuel cell costs. Currently, the main problem with platinum-cobalt alloy catalysts is their poor stability. Most reported studies have prepared platinum-cobalt catalysts with low active metal loadings, and the preparation of long-life catalysts typically employs complex and difficult-to-operate methods requiring precise control of the synthesis process, such as sulfur anchoring, nitrogen or carbon encapsulation. Summary of the Invention

[0005] This invention addresses the shortcomings of current fuel cell catalysts, such as low activity and poor stability at operating potential, and the susceptibility of catalyst carbon supports to corrosion and reduced durability when the anode is under-gasified and the cathode is at high potential. It provides a simple method for preparing a PtCoRu / W-Ce-C catalyst with high activity, high stability, and strong corrosion resistance of platinum-cobalt-ruthenium active metals supported on cerium-tungsten modified high specific surface area carbon.

[0006] This invention differs from the preparation of ordered alloy catalysts, as it does not require extremely high calcination temperatures or complex N / C encapsulation steps to prevent nano-metal agglomeration during high-temperature treatment. The prepared catalyst exhibits excellent stability in both 30,000 accelerated lifetime cycling (ADT) cycles at an operating potential (0.6V-0.9V) and 10,000 ADT cycles at a high potential (1.0V-1.5V). The preparation methods mainly involve W-Ce-C composite support preparation and active metal loading.

[0007] A method for preparing a composite carbon-supported PtCoRu catalyst includes the following steps:

[0008] Step 1, preparing cerium and tungsten-modified high specific surface area carbon to prepare W-Ce-C composite support, including:

[0009] (1) Weigh a certain amount of carbon carrier and add it to a certain amount of deionized water and alcohol mixture. Stir for 24 to 48 hours to form a carbon slurry solution. The volume ratio of deionized water to alcohol is 1:0.5 to 1:1. The alcohol is one of methanol, anhydrous ethanol, ethylene glycol, and isopropanol.

[0010] (2) Weigh out a certain amount of cerium nitrate and tungstates such as ammonium tungstate, ammonium metatungstate, sodium tungstate, and sodium metatungstate according to the C:Ce and C:W mass ratios of 1:0.01 to 1:0.1 and 1:0.05 to 1:0.2, respectively, and dissolve them in deionized water. Use two peristaltic pumps to simultaneously and very slowly add the cerium nitrate solution and tungstate solution to the carbon slurry prepared in step (1). After stirring for 24 to 48 hours, adjust the pH of the solution to 9-10 with 1 mol / L NaOH and continue stirring for 2 to 8 hours.

[0011] (3) Using a peristaltic pump, slowly add two of the following reducing agents to the mixed solution obtained in step (2): sodium borohydride, hydrazine hydrate, ascorbic acid, and ammonium acetate. After adding the reducing agents, stir for 1 hour, transfer the solution to a round-bottom flask, and reflux in an oil bath at 80℃~120℃ for 2~12 hours. After cooling, filter and wash the solution, and vacuum dry and grind the product to obtain the W-Ce-C composite carrier.

[0012] Step 2, preparing the PtCoRu / W-Ce-C catalyst, including:

[0013] (4) Add the carbon support and benzoic acid obtained in step (3) to a mixed solution of N,N-dimethylformamide (DMF) and alcohol, and stir for 16-48 h to form a carbon slurry solution. The volume ratio of DMF to alcohol is 1:0.1 to 1:0.4, and the alcohol is one of methanol, ethanol, ethylene glycol, and isopropanol.

[0014] (5) Dissolve platinum acetylacetone, cobalt acetylacetone, and ruthenium acetylacetone in DMF solution and slowly add them to the carbon slurry in step (4) using a peristaltic pump. Stir for 12–24 h, then transfer the mixed solution to a hydrothermal reactor and react at 150–180 °C for 5–12 h. The loading of each active metal is as follows: Pt:W-Ce-C carrier mass ratio is 1:0.8–1:1, Pt:Co molar ratio is 1:0.2–1:0.6, and Pt:Ru molar ratio is 1:0.01–1:0.03.

[0015] (6) After the above reaction is completed, the reactor is cooled to room temperature by a fan, the solution is taken out and stirred for 16-24 hours, washed by vacuum filtration with deionized water and ethanol, dried under vacuum at 80°C for 8-12 hours, and ground to obtain PtCoRu / W-Ce-C catalyst.

[0016] The composite carbon support PtCoRu catalyst prepared by the above preparation method includes a W-Ce-C composite support and PtCoRu active metal components, wherein: the cerium and tungsten addition amounts are: C:Ce mass ratio of 1:0.01 to 1:0.1, and C:W mass ratio of 1:0.05 to 1:0.2; the active metal loading amounts are: Pt:W-Ce-C support mass ratio of 1:0.8 to 1:1, Pt:Co molar ratio of 1:0.2 to 1:0.6, and Pt:Ru molar ratio of 1:0.01 to 1:0.03.

[0017] The specific beneficial effects of this invention are as follows:

[0018] 1) The catalyst preparation method according to the above steps is simple to control pH value throughout the preparation process. It does not involve steps such as ultrasonic dispersion, high calcination temperature, and acid washing, which are not convenient for subsequent scale-up production. It does not require the addition of dispersants, modifiers, etc. to form a complex system. It uses common solvents and reducing agents. The main control steps of the preparation method are easy-to-control steps such as stirring time, heating temperature, and solution addition rate. It is simple and practical, and the catalyst has good reproducibility. It is easy to achieve mass production in the future.

[0019] 2) Using cerium-tungsten modified high specific surface area carbon as a support, the prepared ruthenium-doped platinum-cobalt-ruthenium alloy catalyst exhibits superior specific activity (≥440 mA / mgPt). A small amount of ruthenium doping has minimal impact on catalyst activity but significantly improves stability. Electrochemical testing shows that the catalyst not only exhibits excellent stability (attenuation rate ≤5%) under 30,000 accelerated life cycle (ADT) cycles at a working voltage (0.6V-0.9V), but also maintains excellent stability (attenuation rate ≤20%) after 30,000 ADT cycles at a high potential (1.0V-1.5V) followed by 10,000 ADT cycles.

[0020] 3) The DMF and alcohol used in the preparation method serve as both dual solvents and dual reducing agents, resulting in an ideal reduction loading effect. The actual platinum loading measured by inductively coupled plasma spectrometry (ICP) was less than 5% different from the theoretical loading. The active metal was uniformly dispersed with very little agglomeration. Attached Figure Description

[0021] Figure 1 Pt3Co1Ru 0.09 Transmission electron microscopy image (200 nm) of the / W-Ce-C catalyst.

[0022] Figure 2 Pt3Co1Ru 0.09 Transmission electron microscopy image (100 nm) of the / W-Ce-C catalyst.

[0023] Figure 3 This is a schematic diagram illustrating the stability of the Pt3Co / W-Ce-C catalyst.

[0024] Figure 4 Pt3Co1Ru 0.03 A schematic diagram of the stability of the / W-Ce-C catalyst.

[0025] Figure 5 Pt3Co1Ru 0.09 A schematic diagram of the stability of the / W-Ce-C catalyst.

[0026] Figure 6 Pt3Co1Ru 0.9A schematic diagram of the stability of the / W-Ce-C catalyst. Detailed Implementation

[0027] To further illustrate the present invention, the following detailed description of the preparation method of the ternary alloy supported on the composite support catalyst provided by the present invention is provided in conjunction with the embodiments, but it should not be construed as a limitation on the scope of protection of the present invention.

[0028] The carbon support used in this embodiment has a specific surface area of ​​1095 m². 2 / g (DFT method summary). Unless otherwise specified, all reagents and instruments used are commercially available standard products.

[0029] Example 1

[0030] (1) Weigh 1.00 g of carbon support, grind for ten minutes, and dissolve in 200 ml of a mixed solution of ethylene glycol and deionized water (volume ratio 1:1). Stir for 30 h to form a carbon slurry. Weigh 0.31 g of cerium(III) nitrate hexahydrate and 0.09 g of sodium tungstate (dihydrate), and dissolve them in 10 ml of deionized water respectively. Use a peristaltic pump to add the precursor solution to the carbon slurry solution at a rate of 0.5 ml / min. After the addition is complete, continue stirring at room temperature for 24 h. Adjust the pH of the solution to 10 using 1 mol / L NaOH, and stir for another 2 h. Use a peristaltic pump to add 10 ml of 5% sodium borohydride aqueous solution and 10 ml of hydrazine hydrate to the above mixed solution at a rate of 1 ml / min. After the reducing agent is added, stir for 1 h, transfer the solution to a round-bottom flask, reflux in an oil bath at 120 °C for 4 h, cool the solution, filter and wash, vacuum dry the product, grind it, and obtain the W-Ce-C composite support.

[0031] (2) Weigh 0.2 g of W-Ce-C composite carrier and 1.8 g of benzoic acid and dissolve them in 44 ml of a mixture of DMF and ethylene glycol (volume ratio 1:0.1). Stir for 48 h to form a carbon slurry solution. Dissolve 0.4 g of platinum acetylacetonate, 0.12 g of cobalt(III) acetylacetonate, and 0.004 g of ruthenium(III) acetylacetonate in 36 ml of DMF solution and add the solution to the carbon slurry at a rate of 0.2 ml / min using a peristaltic pump. Stir for 12 h, then transfer the mixture to a hydrothermal reactor and react at 170 °C for 12 h. Filter the reaction solution and wash with anhydrous ethanol and deionized water. Dry under vacuum at 80 °C to obtain Pt3Co1Ru. 0.03 / W-Ce-C catalyst.

[0032] Electrochemical performance characterization of the catalyst revealed that the initial mass activity (MA) and electrochemical specific surface area (ECSA) of the catalyst in Example 1 were not significantly different from the initial activities of the catalysts in Example 2, Comparative Example 1, and Comparative Example 2, with MA and ECSA both around 500 mA / mg. Pt and 55m 2 / g Pt In this embodiment, Pt3Co1Ru 0.03 / W-Ce-C catalyst (see W-Ce-C catalyst) Figure 4 After 30,000 cycles of ADT at operating voltage (0.6V-0.9V), the MA decayed by 19.93%, while the ECSA showed virtually no decay. (Pt3Co1Ru) 0.03 / W-Ce-C and the Pt3Co / W-Ce-C catalyst in Comparative Example 1 (see [link]) Figure 3 The performance is comparable, indicating that when the molar ratio of Pt:Ru is 1:0.01, the addition of the active metal Ru has little effect on the stability of the catalyst.

[0033] Example 2

[0034] (1) Preparation of composite carrier: Same as step (1) of Example 1;

[0035] (2) Weigh 0.2 g of W-Ce-C composite carrier and 1.8 g of benzoic acid and dissolve them in 44 ml of a mixture of DMF and ethylene glycol (volume ratio 1:0.1). Stir for 48 h to form a carbon slurry solution. Dissolve 0.4 g of platinum acetylacetonate, 0.12 g of cobalt(III) acetylacetonate, and 0.012 g of ruthenium(III) acetylacetonate in 36 ml of DMF solution and add the solution to the carbon slurry at a rate of 0.2 ml / min using a peristaltic pump. Stir for 12 h, then transfer the mixture to a hydrothermal reactor and react at 170 °C for 12 h. Filter the reaction solution and wash with anhydrous ethanol and deionized water. Dry under vacuum at 80 °C to obtain Pt3Co1Ru. 0.09 / W-Ce-C catalyst.

[0036] Electrochemical performance characterization results show that Pt3Co1Ru 0.09 / W-Ce-C catalyst (see W-Ce-C catalyst) Figure 5 After 30,000 cycles of ADT at an operating voltage of 0.6V-0.9V, the MA decay was 4.90%, and the ECSA decay was 1.90%. Compared to the platinum-cobalt catalyst without Ru in Comparative Example 1, Pt3Co1Ru... 0.09 The stability of MA of the / W-Ce-C catalyst was improved by about 10%; after 10,000 cycles of ADT at high potential (1.0-1.5V), MA decayed by 18.00%, ECSA decayed by 18.00%, and the high potential decay was less than 20%, indicating that the catalyst has good support corrosion resistance.

[0037] Comparative Example 1

[0038] (1) Preparation of composite carrier: Same as step (1) of Example 1;

[0039] A carbon slurry solution was formed by stirring for 48 h. 0.4 g of platinum acetylacetonate and 0.12 g of cobalt(III) acetylacetonate were dissolved in 36 ml of DMF solution and added to the carbon slurry using a peristaltic pump at a rate of 0.2 ml / min. The mixture was stirred for 12 h, and then transferred to a hydrothermal reactor and reacted at 170 °C for 12 h. The reacted solution was filtered and washed with anhydrous ethanol and deionized water. The Pt3Co / W-Ce-C catalyst was obtained by vacuum drying at 80 °C.

[0040] Electrochemical performance characterization showed that the Pt3Co / W-Ce-C catalyst (see...) Figure 3 After 30,000 cycles of ADT at a working voltage (0.6V-0.9V), the mass specific activity (MA) decreased by 15%, while the electrochemical specific surface area (ECSA) showed no decrease.

[0041] Comparative Example 2

[0042] (1) Preparation of composite carrier: Same as step (1) of Example 1;

[0043] (2) Weigh 0.2 g of W-Ce-C composite carrier and 1.8 g of benzoic acid and dissolve them in 44 ml of a mixture of DMF and ethylene glycol (volume ratio 1:0.1). Stir for 48 h to form a carbon slurry solution. Dissolve 0.4 g of platinum acetylacetone, 0.12 g of cobalt(III) acetylacetone, and 0.12 g of ruthenium(III) acetylacetone in 36 ml of DMF solution and add the solution to the carbon slurry at a rate of 0.2 ml / min using a peristaltic pump. Stir for 12 h, then transfer the mixture to a hydrothermal reactor and react at 170 °C for 12 h. Filter the reaction solution and wash with anhydrous ethanol and deionized water. Dry under vacuum at 80 °C to obtain Pt3Co1Ru. 0.9 / W-Ce-C catalyst.

[0044] Electrochemical performance characterization showed that Pt3Co1Ru 0.9 / W-Ce-C catalyst (see W-Ce-C catalyst) Figure 6 After 30,000 cycles of ADT at operating voltage (0.6V-0.9V), the MA decayed by 5.28%, and the ECSA decayed by 6.89%; in this comparative example, Pt3Co1Ru 0.9 / W-Ce-C and Pt3Co1Ru in Example 2 0.09 The performance of the / W-Ce-C catalysts is comparable, indicating that further increasing the amount of active metal Ru in the catalyst has little effect on improving the catalyst performance. Considering cost, the catalyst performance is better when the molar ratio of Pt:Ru is 1:0.03.

Claims

1. A composite carbon-supported PtCoRu catalyst, characterized in that, The catalyst comprises a W-Ce-C composite support and a PtCoRu active metal component; the preparation method of the W-Ce-C composite support includes: adding the carbon support to a mixture of deionized water and alcohol and stirring to form a carbon slurry; adding a cerium precursor and a tungsten precursor solution to the carbon slurry; adjusting the pH of the solution to 9-10; and reducing it using a dual reducing agent composed of sodium borohydride and hydrazine hydrate to obtain the W-Ce-C composite carbon support; wherein: The amounts of cerium and tungsten added are: a C:Ce mass ratio of 1:0.01 to 1:0.1, and a C:W mass ratio of 1:0.05 to 1:0.2; The active metal loading is as follows: the mass ratio of Pt:W-Ce-C carrier is 1:0.8~1:1, the molar ratio of Pt:Co is 1:0.2~1:0.6, and the molar ratio of Pt:Ru is 1:0.01~1:0.03; The PtCoRu active metal component is loaded onto a W-Ce-C composite carrier by reacting in a hydrothermal reactor at 150~180℃.

2. A method for preparing a composite carbon-supported PtCoRu catalyst as described in claim 1, characterized in that, Includes the following steps: Step 1, preparing cerium and tungsten-modified high specific surface area carbon to prepare W-Ce-C composite support, including: Step (1.1) Measure a certain amount of deionized water and alcohol and stir them evenly. Add a certain amount of carbon with high specific surface area and stir for a period of time to form a carbon slurry solution. Step (1.2) Weigh a certain amount of cerium precursor and tungsten precursor and dissolve them in deionized water. After they are completely dissolved, use two peristaltic pumps to slowly add the cerium precursor and tungsten precursor solutions to the carbon slurry solution at the same time. After the addition is complete, continue to stir at room temperature for a period of time. Adjust the pH of the solution to 9-10 using 1mol / L NaOH and stir for a period of time. Step (1.3) Use a peristaltic pump to slowly add the aqueous solutions of the two reducing agents to the mixed solution obtained in step (1.2). After adding the reducing agents, stir and transfer the solution into a round-bottom flask. Heat the solution in an oil bath at 80~120℃ for a period of time. After the solution is cooled, filter and wash it. Dry the product under vacuum and grind it to obtain the W-Ce-C composite carrier. Step 2, preparing the PtCoRu / W-Ce-C catalyst, including: Step (2.1) Add the W-Ce-C composite carrier and benzoic acid to the mixture of N,N-dimethylformamide and alcohol, and stir for a period of time to form a carbon slurry solution; Step (2.2) Dissolve platinum acetylacetone, cobalt acetylacetone and ruthenium acetylacetone in N,N-dimethylformamide solution, and slowly add it to the above carbon slurry using a peristaltic pump. Stir for a period of time, then transfer the mixed solution into a hydrothermal reactor and react at 150~180℃ for a period of time. Step (2.3) After the reaction is complete, the reactor is cooled to room temperature by a fan. The solution is taken out and stirred for a period of time. It is washed by vacuum filtration with deionized water and ethanol, dried under vacuum at 80°C, and ground to obtain the PtCoRu / W-Ce-C catalyst.

3. The preparation method according to claim 2, characterized in that, In step (1.1), the volume ratio of deionized water to alcohol is 1:0.5 to 1:1; the alcohol is one of methanol, ethanol, ethylene glycol, and isopropanol.

4. The preparation method according to claim 2, characterized in that, The cerium precursor mentioned in step (1.2) is cerium nitrate, and the tungsten precursor is either ammonium tungstate or ammonium metatungstate.

5. The preparation method according to claim 2, characterized in that, The mass ratio of sodium borohydride to hydrazine hydrate added is 0.05~1:0.

2.

6. The preparation method according to claim 2, characterized in that... In step (2.1), the alcohol is one of methanol, ethanol, ethylene glycol, and isopropanol.

7. The preparation method according to claim 2, characterized in that, In step (2.1), the volume ratio of DMF to alcohol is 1:0.1 to 1:0.

4.

8. The preparation method according to any one of claims 2-7, characterized in that: In steps (1.1) and (1.2), the stirring time is 24~48h; In step (1.3), the reflux heating time is 2~12h; In step (2.1), the stirring time is 16~48h; In step (2.2), the stirring time is 12~24h and the reaction time is 5~12h; In step (2.3), the stirring time is 16~24h.

9. The application of the composite carbon support PtCoRu catalyst as described in claim 1 as a cathode catalyst in a proton exchange membrane fuel cell.

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