A ternary ordered alloy catalyst for fuel cells and a method for preparing the same
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI INST OF SPACE POWER SOURCES
- Filing Date
- 2024-12-13
- Publication Date
- 2026-06-16
Smart Images
Figure CN119852425B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterials technology, specifically to a ternary ordered alloy catalyst for fuel cells and its preparation method. Background Technology
[0002] The oxygen reduction reaction (ORR) is one of the key reactions in proton exchange membrane fuel cells (PEMFCs). As the primary cathode reaction, the ORR is responsible for reducing oxygen to water or other oxygen-containing compounds, releasing electrons that can then be used to generate electricity. Carbon-supported Pt nanoparticle (Pt / C) catalysts are the most widely used cathode catalysts in PEMFCs. However, in the acidic operating environment of PEMFCs, Pt nanoparticles are prone to dissolution and migration, leading to the loss of active sites and resulting in poor activity / durability of the Pt / C catalyst. Furthermore, Pt is scarce and expensive in the Earth's crust, causing the cost of the Pt / C catalyst to account for more than 50% of the total cost of the fuel cell, hindering the large-scale production and application of PEMFCs.
[0003] Over the past decade, alloying Pt with other transition metals (hereinafter referred to as "M") such as Fe, Co, Ni, and Cu has reduced the energy of d-orbital electrons, weakening the adsorption strength of oxygen reduction reaction (ORR) intermediates (such as OH*, O*, OOH*, etc.) on the catalyst surface. This has significantly improved the activity of the cathode catalyst and reduced the amount of Pt used. In disordered face-centered cubic solid solution structures, M and Pt are randomly distributed. M has poor electrochemical stability and higher activity on the alloy surface than Pt, making it easier for M to participate in the electrochemical reaction. This leads to the easy dissolution of M during actual use, reducing the activity and stability of the catalyst. In contrast, in ordered intermetallic structures (such as tetragonal L10 or cubic L12 structures), M and Pt are arranged in a specific stoichiometric ratio and a highly ordered manner, exhibiting strong interatomic interactions. This can significantly slow down the dissolution of M, thereby significantly improving the activity and stability of the catalyst. CN116404182A discloses a low-platinum ternary alloy catalyst and its preparation method, but its synthesis process is complex and a disordered solid solution alloy is synthesized. In actual use, the metal in the alloy will gradually dissolve, resulting in a serious degradation of the membrane electrode performance.
[0004] Therefore, improving the orderliness of the alloy can significantly slow down the dissolution of the metal, enhance the activity and stability of the catalyst, and thus improve the performance of the fuel cell. Summary of the Invention
[0005] The purpose of this invention is to improve the degree of order and inhibit metal dissolution by doping lanthanide elements into platinum-cobalt binary ordered alloy catalysts, thereby solving the problem of reduced catalyst activity and stability.
[0006] To achieve the above objectives, the present invention provides a method for preparing a ternary ordered alloy catalyst for fuel cells, the method comprising:
[0007] Step 1: Disperse carbon black in an aqueous alcohol solution and a surfactant to obtain a carbon black solution;
[0008] Step 2: Prepare platinum precursor solution, cobalt precursor solution and lanthanide precursor solution respectively;
[0009] Step 3: Mix the carbon black solution, platinum precursor solution, cobalt precursor solution and lanthanide precursor solution, and pass a reducing gas to perform thermal reduction to obtain a ternary ordered alloy catalyst; the thermal reduction temperature is 700℃-1000℃ and the time is 0.5h-2h.
[0010] Optionally, in step 2, the platinum precursor includes at least one or more of H2PtCl6, K2PtCl4, ammonium chloroplatinate, and platinum acetylacetonate; the cobalt precursor includes at least one or more of cobalt chloride, cobalt nitrate, and cobalt acetate; and the lanthanide precursor is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium precursors.
[0011] Optionally, in step 3, the molar ratio of platinum atoms, cobalt atoms and lanthanide atoms is (1-3):(0.25-4):(1-1.5).
[0012] Optionally, in step 1, the volume ratio of water to anhydrous ethanol in the aqueous alcohol solution is (1-2):(1-3), and the mass ratio of carbon black to the aqueous alcohol solution is (1-2):(1-3).
[0013] Optionally, before step 1, the carbon black is further etched with sulfuric acid, wherein the mass ratio of carbon black to sulfuric acid is (1-1.5):(1-2), and the etching time is 12-14 hours.
[0014] Optionally, in step 1, the surfactant includes at least one or more of Triton X-114, Triton X-100, Triton X-45, sodium dodecyl sulfate, and Tween-20.
[0015] Optionally, in step 3, the mixing method includes ultrasound and stirring, with the ultrasound time being 60-180 minutes and the stirring time being 10-15 hours.
[0016] Optionally, step 3 further includes solvent removal before introducing the reducing gas; the solvent removal method is any one of freeze drying, natural air drying, baking, water bath evaporation, rotary evaporation, or oil bath evaporation.
[0017] Optionally, in step 3, the reducing gas is either a nitrogen-hydrogen mixture or an argon-hydrogen mixture.
[0018] The present invention also provides a ternary ordered alloy catalyst for fuel cells obtained by any of the above preparation methods.
[0019] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:
[0020] 1) Doping lanthanides into platinum-cobalt binary ordered alloy catalysts to form ternary ordered alloy catalysts. Due to the large atomic radius of lanthanides, the compressive strain of the platinum-cobalt system is changed, thereby affecting the electronic structure of platinum, cobalt and lanthanides, so that the three are arranged in a highly ordered manner, thus improving the degree of order. The ordered occupation of the three metal atoms at the corresponding lattice points in the crystal lattice makes the formation of more stable chemical bonds between the metals, and the interaction is enhanced, thereby significantly slowing down the dissolution of cobalt and lanthanides, which helps to improve the activity and stability of the ternary ordered alloy catalyst.
[0021] 2) Furthermore, using a ternary ordered alloy catalyst as the cathode catalyst in a proton exchange membrane fuel cell can improve the power density of the fuel cell, thereby improving the performance of the fuel cell. Attached Figure Description
[0022] Figure 1 This is a TEM image of the ternary ordered alloy catalyst of Example 1 of the present invention; wherein b is a partial magnified view of a.
[0023] Figure 2 The images show the XRD diffraction patterns of the ternary ordered alloy catalysts of Comparative Example 1 and Examples 1-3 of the present invention; where b is a partially enlarged view of a.
[0024] Figure 3 The oxygen reduction activity test curves of the ternary ordered alloy catalysts of Comparative Example 1 and Examples 1-3 of the present invention are shown; where a is the linear voltammetry curve and b is the cyclic voltammetry curve.
[0025] Figure 4 This is a stability performance test diagram of the ternary ordered alloy catalyst of Example 1 of the present invention.
[0026] Figure 5 The power density test graphs show the ternary ordered alloy catalysts of Comparative Example 1 and Examples 1-3 of the present invention as cathode catalysts for proton exchange membrane fuel cells. Detailed Implementation
[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0029] As described in the background section, Pt is alloyed with other transition metals M to form Pt-M alloy catalysts. In the disordered face-centered cubic solid solution structure, M and Pt are randomly distributed. M has poor electrochemical stability and higher activity on the alloy surface than Pt, making it easier for M to participate in the electrochemical reaction. This leads to the easy dissolution of M during actual use, reducing the activity and stability of the catalyst. In contrast, in the ordered intermetallic structure, M and Pt are arranged according to a specific stoichiometric ratio and a highly ordered manner, exhibiting strong interatomic interactions. This can significantly slow down the dissolution of the metal, thereby significantly improving the activity and stability of the catalyst.
[0030] To improve the activity and stability of the catalyst, this invention dops lanthanides into a platinum-cobalt binary ordered alloy catalyst to form a ternary ordered alloy catalyst. The lanthanides allow platinum, cobalt, and lanthanides to arrange themselves in a highly ordered manner, increasing the degree of order. Simultaneously, the strong interactions between the ordered metals significantly slow down the dissolution of cobalt and lanthanides, thus improving the activity and stability of the ternary ordered alloy catalyst. Specifically, this invention provides a method for preparing a ternary ordered alloy catalyst for fuel cells, the method comprising:
[0031] Step 1: Disperse carbon black in an aqueous alcohol solution and a surfactant to obtain a carbon black solution.
[0032] In this step, the mass ratio of carbon black to the aqueous alcohol solution is (1-2):(1-3), and the volume ratio of water to anhydrous ethanol in the aqueous alcohol solution is (1-2):(1-3). The ultrasonic dispersibility of carbon black in the aqueous alcohol solution is 60-180 min. After ultrasonication, a surfactant is added and stirred for 10-15 h. After stirring, the resulting carbon black solution is kept at 25°C and stirred for later use. Because of the strong interaction forces between carbon black particles, they are prone to agglomeration, affecting dispersibility. The addition of a surfactant can reduce the interaction forces between carbon black particles, weaken their agglomeration tendency, and achieve uniform dispersion of carbon black.
[0033] In some embodiments, the surfactant includes at least one or more of Triton X-114, Triton X-100, Triton X-45, sodium dodecyl sulfate, and Tween-20.
[0034] Prior to step 1, the carbon black is further etched with sulfuric acid. The carbon black is ultrasonically dispersed in sulfuric acid at a mass ratio of (1-1.5):(1-2), and then etched in a 60°C oven for 12-14 hours. After etching, the carbon black is centrifuged, washed, and then dried in a vacuum drying oven. The purpose of etching the carbon black with sulfuric acid is to remove other organic impurities and metal ions, thereby improving the purity and quality of the carbon black.
[0035] Step 2: Prepare platinum precursor solution, cobalt precursor solution and lanthanide precursor solution respectively.
[0036] In some embodiments, the platinum precursor includes at least one or more of H₂PtCl₆, K₂PtCl₄, ammonium chloroplatinate, and platinum acetylacetonate; the mass of platinum in the platinum precursor is 1%-40% of the mass of the carbon support; the cobalt precursor includes at least one or more of cobalt chloride, cobalt nitrate, and cobalt acetate; the lanthanide precursor is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium precursors. The molar ratio of platinum atoms, cobalt atoms, and lanthanide atoms is (1-3):(0.25-4):(1-1.5), which can significantly improve the order of the ternary ordered alloy. Platinum precursor solutions, cobalt precursor solutions, and lanthanide precursor solutions of different concentrations can be prepared as needed.
[0037] Step 3: Mix the carbon black solution, platinum precursor solution, cobalt precursor solution and lanthanide precursor solution, and pass a reducing gas to perform thermal reduction to obtain a ternary ordered alloy catalyst; the thermal reduction temperature is 700℃-1000℃ and the time is 0.5h-2h.
[0038] After mixing the carbon black solution, platinum precursor solution, cobalt precursor solution, and lanthanide precursor solution, stirring is started for 10-15 hours. The purpose of stirring is to ensure more complete mixing of the precursor solution and carbon black solution, which is more conducive to the subsequent loading of the precursor onto the carbon black. After stirring is complete, the solvent is removed and a reducing gas is introduced for thermal reduction.
[0039] In some embodiments, the solvent removal method is any one of freeze drying, natural air drying, baking, water bath evaporation, rotary evaporation, or oil bath evaporation.
[0040] In some embodiments, the reducing gas is either a nitrogen-hydrogen mixture or an argon-hydrogen mixture. The ternary ordered alloy catalyst obtained by thermal reduction is arranged in a highly ordered manner, exhibiting a high degree of order. The orderly occupation of corresponding lattice points in the crystal lattice by the three metal atoms leads to the formation of more stable chemical bonds between the metals, enhancing their interaction and thus significantly slowing down the dissolution of the metals. Consequently, the activity and stability of the ternary ordered alloy catalyst are improved.
[0041] The sulfuric acid, chloroplatinic acid hexahydrate, cobalt nitrate hexahydrate, and cerium nitrate used in Comparative Example 1 and Examples 1-3 were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The preparation methods are as follows: 2.72 ml of sulfuric acid (18.4 mol / L) was dissolved in 1 L of water to obtain 0.05 mol / L sulfuric acid; 20 mg of chloroplatinic acid hexahydrate was dissolved in 1 ml of water to obtain a 20 mg / ml chloroplatinic acid hexahydrate solution; 20 mg of cobalt nitrate hexahydrate was dissolved in 1 ml of water to obtain a 20 mg / ml cobalt nitrate hexahydrate solution; and 10 mg of cerium nitrate was dissolved in 1 ml of water to obtain a 10 mg / ml cerium nitrate solution.
[0042] Comparative Example 1
[0043] 30 mg of carbon black was placed in 30 ml of sulfuric acid (0.05 mol / L) and sonicated for 60 min. It was then etched in a 60 °C oven for 12 h, centrifuged, washed, and dried in a vacuum drying oven. 20 mg of the dried carbon black was placed in 20 ml of an alcoholic-water solution and sonicated for 60 min. 5 mg of Triton X-114 was added, and the mixture was magnetically stirred for 10 h to obtain a carbon black solution. Then, 0.734 ml of chloroplatinic acid hexahydrate solution (20 mg / ml) and 0.084 ml of cobalt nitrate hexahydrate solution (20 mg / ml) were added sequentially to the carbon black solution. After magnetic stirring for 12 h, the solvent was removed by rotary evaporation. Finally, the solution was thermally reduced at 900 °C for 2 h in a tubular furnace under an argon-hydrogen mixture. After cooling, a binary ordered alloy catalyst was obtained.
[0044] Example 1
[0045] 30 mg of carbon black was placed in 30 ml of sulfuric acid (0.05 mol / L) and sonicated for 60 min. It was then etched in a 60 °C oven for 12 h, centrifuged, washed, and dried in a vacuum drying oven. 20 mg of the dried carbon black was placed in 20 ml of a water-alcohol solution and sonicated for 60 min. 5 mg of Triton X-114 was added, and the mixture was magnetically stirred for 10 h to obtain a carbon black solution. Then, 0.734 ml of chloroplatinic acid hexahydrate solution (20 mg / ml), 0.084 ml of cobalt nitrate hexahydrate solution (20 mg / ml), and 0.068 ml of cerium nitrate solution (10 mg / ml) were added sequentially to the carbon black solution. After magnetic stirring for 12 h, the solvent was removed by rotary evaporation. Finally, the solution was thermally reduced at 900 °C for 2 h in a tube furnace under an argon-hydrogen mixture. After cooling, a ternary ordered alloy catalyst was obtained. Figure 1 The image shown is a morphology image of ternary ordered alloy particles.
[0046] Example 2
[0047] The preparation method of the ternary ordered alloy catalyst is the same as in Example 1, except that the amount of cobalt nitrate hexahydrate solution (20 mg / ml) and cerium nitrate solution (10 mg / ml) added is replaced with 0.269 ml and 0.220 ml, respectively.
[0048] Example 3
[0049] The preparation method of the ternary ordered alloy catalyst is the same as in Example 2, except that the thermal reduction temperature is replaced with 1000℃.
[0050] Figure 2 The XRD diffraction patterns of Comparative Example 1 and Examples 1-3 (where b is a magnified view of a) are shown. Compared with the standard card, the characteristic diffraction peaks of Examples 1-2 have shifted, indicating that cerium atom doping was successful. Example 3 shows that at 700℃-1000℃, changing only the thermal reduction temperature does not affect the characteristic diffraction peaks, indicating that cerium atom doping was successful.
[0051] Example 4
[0052] The oxygen reduction activity of the ternary ordered alloy catalyst was characterized using a three-electrode electrochemical workstation. The ternary ordered alloy catalyst served as the working electrode, platinum as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a 0.1 M HClO4 solution. Cyclic voltammetry was used to test the oxygen reduction activity of the catalyst. Cyclic voltammetry was performed in a nitrogen-saturated 0.1 M HClO4 solution, scanning the potential range from +0.05 to +1.00 V (compared to the reversible hydrogen electrode) at a scan rate of 50 mV / s. -1 To obtain the electrochemical active area (e.g. Figure 3 As shown in b), further linear voltammetry curve testing can be used to obtain mass activity and specific activity (e.g., ...). Figure 3(As shown in a). The intrinsic activity parameters of the catalyst, such as mass activity, specific activity, and electrochemical active area, can be calculated using the Koutecky-Levich equation and the platinum loading in the feed. The calculated mass activity of the ternary ordered alloy catalyst in Example 1 is 0.57 A / mg, and the specific activity is 1.18 mA / cm². 2 The electrochemical active area is 48.5m². 2 / g; The ternary ordered alloy catalyst of Example 2 has a mass activity of 0.24 A / mg and a specific activity of 0.35 mA / cm². 2 The electrochemical active area is 68.91m². 2 / g; The ternary ordered alloy catalyst of Example 3 has a mass activity of 0.197 A / mg and a specific activity of 0.221 mA / cm². 2 The electrochemical active area is 89.47m². 2 / g; The mass activity of the binary ordered alloy catalyst in Comparative Example 1 was 0.105 A / mg, and the specific activity was 0.035 mA / cm². 2 The electrochemical active area is 84.67m². 2 / g; indicates that when the molar ratio of platinum, cobalt, and cerium atoms is appropriate, the ternary ordered alloy catalyst has better mass activity, specific activity, and electrochemical active area.
[0053] Example 5
[0054] The stability of the ternary ordered alloy catalyst of Example 1 was characterized using a three-electrode electrochemical workstation. The ternary ordered alloy catalyst was used as the working electrode, platinum as the counter electrode, and saturated Ag / AgCl as the reference electrode. The electrolyte was a 0.1 M HClO4 solution. The stability of the catalyst was tested by linear voltammetry. Linear voltammetry was performed in an oxygen-saturated 0.1 M HClO4 solution, covering a potential range of +0.6 to +1.10 V (compared to the reversible hydrogen electrode), at a scan rate of 100 mV / s. -1 A total of 20,000 scans were performed. For example... Figure 4 As shown, the current density gradually increases with the increase of the potential difference, but the difference is small under different scanning cycles, indicating that the ternary ordered alloy catalyst of Example 1 has good stability.
[0055] Example 6
[0056] The power density of a low-temperature proton exchange membrane fuel cell was tested using a ternary ordered alloy catalyst as the cathode catalyst. The anode was a 20% Pt / C catalyst, and the cathode was a ternary ordered alloy catalyst. The platinum loadings at the anode and cathode were 0.1 and 0.2 mg / cm³, respectively. 2 The battery temperature is 60℃, and the back pressure on both the anode and cathode sides is 100kPa. For example... Figure 5 As shown, the product of current density and battery voltage is the power density. The peak power densities of the proton exchange membrane fuel cells in Comparative Example 1 and Examples 1-3 are 631 mW / cm². 2 738mW / cm 2 646mW / cm 2 582mW / cm 2 The power densities are not significantly different, indicating that the ternary ordered alloy catalyst prepared by the method of this embodiment has good application prospects as a cathode catalyst for proton exchange membrane fuel cells.
[0057] In summary, this invention involves doping a platinum-cobalt binary ordered alloy catalyst with lanthanides to form a ternary ordered alloy catalyst. The lanthanides alter the compressive strain of the platinum-cobalt system, thereby affecting the electronic structure of platinum, cobalt, and lanthanides, causing them to arrange themselves in a highly ordered manner, thus increasing the degree of order. The ordered occupation of the three metal atoms at corresponding lattice points in the crystal lattice leads to more stable chemical bonds between the metals, enhancing their interactions and significantly slowing the dissolution of cobalt and lanthanides. This contributes to improving the activity and stability of the ternary ordered alloy catalyst. Using this ternary ordered alloy catalyst as the cathode catalyst in a proton exchange membrane fuel cell can increase the power density of the fuel cell, thereby improving its performance.
[0058] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A method for preparing a ternary ordered alloy catalyst for fuel cells, characterized in that, The method includes: Step 1: Disperse carbon black in an aqueous alcohol solution and a surfactant to obtain a carbon black solution; Step 2: Prepare platinum precursor solution, cobalt precursor solution and lanthanide precursor solution respectively; Step 3: Mix the carbon black solution, platinum precursor solution, cobalt precursor solution and lanthanide precursor solution, and pass a reducing gas to perform thermal reduction to obtain a ternary ordered alloy catalyst; the thermal reduction temperature is 700℃-1000℃ and the time is 0.5h-2h. The molar ratio of platinum atoms, cobalt atoms and lanthanide atoms is (1-3):(0.25-4):(1-1.5).
2. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, In step 2, the platinum precursor includes at least one or more of H2PtCl6, K2PtCl4, ammonium chloroplatinate, and platinum acetylacetonate; the cobalt precursor includes at least one or more of cobalt chloride, cobalt nitrate, and cobalt acetate; and the lanthanide precursor is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium precursors.
3. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, In step 1, the volume ratio of water to anhydrous ethanol in the aqueous alcohol solution is (1-2):(1-3), and the mass ratio of carbon black to the aqueous alcohol solution is (1-2):(1-3).
4. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, Before step 1, the process further includes etching the carbon black with sulfuric acid, wherein the mass ratio of carbon black to sulfuric acid is (1-1.5):(1-2), and the etching time is 12-14 hours.
5. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, In step 1, the surfactant includes at least one or more of Triton X-114, Triton X-100, Triton X-45, sodium dodecyl sulfate, and Tween-20.
6. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, In step 3, the mixing method includes ultrasound and stirring, with ultrasound time of 60-180 minutes and stirring time of 10-15 hours.
7. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, Step 3 includes solvent removal before introducing the reducing gas; the solvent removal method is any one of freeze drying, natural air drying, baking, water bath evaporation, rotary evaporation or oil bath evaporation.
8. The method for preparing a ternary ordered alloy catalyst for fuel cells as described in claim 1, characterized in that, In step 3, the reducing gas is either a nitrogen-hydrogen mixture or an argon-hydrogen mixture.
9. A ternary ordered alloy catalyst for fuel cells obtained by the preparation method according to any one of claims 1-8.