Preparation method of platinum-based alloy rare earth metal oxide fuel cell anode catalyst

Abstract

The invention discloses a preparation method of a platinum-based alloy rare earth metal oxide fuel cell anode catalyst, relates to a preparation method of a platinum-based alloy oxide fuel cell catalyst, and aims to solve the technical problems that the existing methanol fuel cell anode catalyst is low in catalytic activity and prone to carbon monoxide poisoning. The method comprises the following steps: firstly, preparing a CeO2 catalyst carrier material by adopting a hydrothermal synthesis method, then mixing corresponding precursor solutions of Pt, Sn and Cu used for preparing a PtSnCu alloy with the CeO2 catalyst carrier material, carrying out an oil bath heating reaction, and then separating, washing and drying to obtain the catalyst PtSnCu / CeO2. The initial capacity of the catalyst in an acidic electrolyte is 1010.5-1163.3 mA mgPt <-1 >, the initial capacity is 680.65-820.4 mA mgPt <-1 > after 500 cycles, the retention rate is 67.4%-70.5%, and the catalyst can be used in the field of methanol fuel cells.

Description

Technical Field

[0001] The present invention belongs to the field of material synthesis technology and relates to a method for preparing a platinum-based alloy oxide fuel cell catalyst. Background Art

[0002] Compared to hydrogen fuel cells, direct methanol fuel cells (DMFCs) offer advantages such as low temperature, fast start-up, clean fuel, and simple structure, and have broad application prospects in portable electronic products. Methanol fuel cells are expected to become a new and efficient fuel cell due to their low fuel cost, high energy conversion rate, and freedom from the limitations of the Carnot cycle.

[0003] Methanol fuel cell anodes require excellent oxygen reduction activity and durability. Currently, platinum, platinum alloys, and metal oxides are the most widely studied catalyst materials for methanol fuel cells. Compared to other materials, platinum alloy catalysts have attracted considerable attention due to their high catalytic activity, excellent stability, and relatively low cost. However, MOR-like CO intermediates are prone to poisoning on the Pt surface, a major factor limiting the catalytic performance of Pt-based catalysts.

[0004] The article "On the design of atomic diffusion Pt 47 Sn 12 Cu 41 Starting from typical PtCu nanocrystals, we adopt an atomic Sn diffusion strategy to construct well-defined PtCu nanostructures. 47 Sn 12 Cu 41 Octapod metal nanoframes, which are used as catalysts to promote ethanol oxidation, have a catalytic activity of 3.10 Amg -1 Pt , and can also promote the carbon-carbon bond breakage and oxidation of toxic CO intermediates, but its ability to resist CO poisoning is limited. Summary of the Invention

[0005] This invention aims to address the technical issues of low catalytic activity and susceptibility to carbon monoxide poisoning in existing methanol fuel cell anode catalysts by providing a method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst. The invention produces a highly efficient bifunctional catalyst material, PtSnCu / CeO2, with excellent electrochemical performance and strong resistance to CO poisoning.

[0006] The method for preparing the platinum-based alloy rare earth metal oxide fuel cell anode catalyst of the present invention is carried out according to the following steps: 1. Preparation of CeO2 catalyst support material by hydrothermal synthesis: (1) Add sodium chloride and sodium hydroxide to distilled water and stir to obtain solution A; add cerium nitrate to water and stir to obtain solution B; then add solution B to solution A and stir to obtain a mixed solution; (2) The mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave, which was placed in a blast drying oven and maintained at a temperature of 150-190 °C for 12-26 h for hydrothermal reaction. After the reaction was completed, the solid phase was centrifuged, washed, and vacuum-dried to obtain a CeO2 precursor. (3) Grind the CeO2 precursor and place it in a porcelain boat, then place the porcelain boat in a tube furnace filled with argon gas, heat it to 400~900℃ and calcine it for 2~6 hours. After cooling, the CeO2 catalyst support material is obtained. 2. The corresponding Pt, Sn, and Cu salt solutions used to prepare the PtSnCu alloy are mixed with the CeO2 catalyst carrier material, and ethylene glycol and distilled water are added, and the mixture is evenly mixed by ultrasonication to obtain a precursor solution; the precursor solution is placed in an oil bath at 120-160°C for 1-4 hours; the solid phase is separated by centrifugation, and then washed and vacuum-dried to obtain a platinum-based alloy rare earth metal oxide fuel cell anode catalyst, which is recorded as PtSnCu / CeO2.

[0007] Furthermore, the hydrothermal treatment in step 1 (2) is performed at 180°C for 24 h.

[0008] Furthermore, the vacuum drying in step 1 (2) is carried out in a vacuum drying oven at a temperature of 60-70°C for 8-12 hours.

[0009] Furthermore, the calcination temperature in step 1 (3) is 600°C and the calcination time is 4 hours.

[0010] Furthermore, the oil bath temperature in step 2 is 140°C and the oil bath time is 2 hours. Under these conditions, the one-pot reduction method can uniformly reduce the PtSnCu alloy on the CeO2 catalyst support, thereby improving the methanol oxidation activity of the catalyst.

[0011] The present invention adjusts the electronic structure of the PtSnCu catalyst by doping the rare earth element Ce (1.12) with low electronegativity (relative to the Pauling electronegativity scale) to improve its battery electrochemical performance. In the PtSnCu / CeO2 of the present invention, the significant difference in electronegativity between Ce and Pt (2.28) leads to a strong electronic interaction between Ce and Pt. In addition, CeO2 acts as a Ce 3+ / Ce 4+The PtSnCu / CeO2 catalyst has a strong catalytic capacity for CO oxidation. The catalyst has an initial capacity of 1010.5~1163.3 mA mg in an acidic electrolyte at a scan rate of 50 mV / s between -0.63 and 0.52 V (MOR). Pt -1 , after 500 cycles, it can maintain 680.65~820.4mA mg Pt -1 The capacity retention rate is 67.4%~70.5%, and it has excellent stability and high CO tolerance in acidic media. The cost is relatively low, which can improve the stability and anti-CO poisoning ability of methanol fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the XRD pattern of the CeO2 catalyst support material prepared in step 1 of Example 1; Figure 2 XRD patterns of PtSnCu / CeO2 prepared in Example 1 and PtSnCu / C prepared in Comparative Example 1; Figure 3 This is a scanning electron microscope image of PtSnCu / CeO2 prepared in Example 1; Figure 4 The electrochemical impedance spectroscopy (EIS) diagrams are for the PtSnCu / CeO2 catalyst prepared in Example 1, the PtSnCu / C prepared in Comparative Example 1, and commercial Pt / C; Figure 5 Graph showing the cycle performance of the PtSnCu / CeO2 catalyst prepared in Example 1, the PtSnCu / C catalyst prepared in Comparative Example 1, and commercial Pt / C. DETAILED DESCRIPTION

[0013] The present invention will be further described below with reference to specific embodiments and corresponding drawings.

[0014] Example 1: This example is a method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst, which is carried out according to the following steps: 1. Preparation of CeO2 catalyst support material by hydrothermal synthesis: (1) Add 1 g of sodium chloride and 7.2 g of sodium hydroxide to 20 mL of distilled water and stir evenly to obtain solution A; add 0.652 g of cerium nitrate to 10 mL of water and stir evenly to obtain solution B; then slowly add solution B to solution A and stir for 30 minutes to mix evenly to obtain a mixed solution; (2) The mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal autoclave, which was placed in a forced air drying oven and maintained at 180 °C for 24 h for hydrothermal reaction. After the reaction was completed, the solid phase was centrifuged and then washed three times with a 1:1 mixture of water and ethanol, and dried in a vacuum drying oven at 60 °C for 12 h to obtain a CeO2 precursor. (3) Grind the CeO2 precursor and place it in a porcelain boat, then place the porcelain boat in a tube furnace filled with argon gas, heat it to 600℃ and calcine it for 4h. After cooling, the CeO2 catalyst support material is obtained. 2. Add 1.335 mL of 0.0192 M chloroplatinic acid solution, 10 mg of copper chloride, 0.54 mL of 0.021 M stannous chloride and 20 mg of CeO2 catalyst carrier material into a round-bottom flask, then add 30 mL of ethylene glycol and 20 mL of ultrapure water, and mix them evenly by ultrasonic treatment for 1 hour to obtain a precursor solution; put the precursor solution into an oil bath at 140°C for 2 hours; separate the solid phase by centrifugation, wash it three times with ethanol, and dry it in a vacuum drying oven at 60°C for 12 hours to obtain a platinum-based alloy rare earth metal oxide fuel cell catalyst material, recorded as PtSnCu / CeO2.

[0015] Comparative Example 1: This comparative example is to prepare a PtSnCu / C catalyst, and the specific steps are as follows: 1.335 mL of 0.0192 M chloroplatinic acid solution, 10 mg of copper chloride, 0.54 mL of 0.021 M stannous chloride and 20 mg of carbon powder were added to a round-bottom flask, and then 30 mL of ethylene glycol and 20 mL of ultrapure water were added, and the mixture was ultrasonically mixed for 1 h to obtain a precursor solution; the precursor solution was placed in an oil bath at 140°C for 2 h; the solid phase was centrifuged, washed three times with ethanol, and dried in a vacuum drying oven at 60°C for 12 h to obtain the catalyst PtSnCu / C.

[0016] The XRD pattern of the CeO2 catalyst support material prepared in step 1 of Example 1 is as follows: Figure 1 As shown in the figure, it can be seen that the CeO2 catalyst support was successfully synthesized, and it can also be seen that the CeO2 catalyst support material has a high degree of crystallinity.

[0017] The XRD patterns of PtSnCu / CeO2 prepared in Example 1 and PtSnCu / C prepared in Comparative Example 1 are shown in FIG. Figure 2 As shown, from Figure 2 It can be seen that the peak of Pt (111) at 39.8° shifts positively, proving the synthesis of the alloy.

[0018] The scanning electron microscope photo of PtSnCu / CeO2 prepared in Example 1 is as follows: Figure 3As shown, from Figure 3 As can be seen, the PtSnCu / CeO2 composite is composed of a PtSnCu alloy and a hexahedral CeO2 support. The highly dispersed Pt, Sn, and Cu active components on the CeO2 support surface increase the number and utilization of active sites. The synergistic effect of CeO2 and PtSnCu nanoparticles promotes the adsorption of *OH and the removal of adjacent *CO, stabilizing the structure of the active components and enhancing the catalyst's methanol oxidation activity.

[0019] The electrochemical performance of the PtSnCu / CeO2 catalyst prepared in Example 1, the PtSnCu / C prepared in Comparative Example 1, and commercial Pt / C were simultaneously tested. The method was as follows: 2 mg of the catalyst was placed in a 5 ml vial, 2 ml of anhydrous ethanol was added, and ultrasonication was performed for 30 minutes. 10 μl of the mixed solution was applied to a glassy carbon electrode (GC, inner diameter 4 mm), followed by 5 μl of Nafion solution and allowed to dry naturally. Electrochemical analysis was performed using a CHI750E electrochemical workstation. In a three-electrode system, a glassy carbon electrode served as the working electrode, a Hg / Hg2SO4 electrode served as the reference electrode, and a platinum sheet served as the counter electrode. Testing was performed in a 0.5 M H2SO4 + 0.5 M CH3OH electrolyte at room temperature (scan rate: 50 mV / s).

[0020] The electrochemical impedance spectroscopy (EIS) curves of the PtSnCu / CeO2 catalyst prepared in Example 1, the PtSnCu / C prepared in Comparative Example 1 and the commercial Pt / C were tested. Figure 4 As shown, from Figure 4 It can be seen that PtSnCu / CeO2 has the lowest charge transfer resistance, which also shows that the charge transfer rate of PtSnCu / CeO2 catalyst is the fastest in the MOR process.

[0021] At the same temperature and in the same electrolyte, the PtSnCu / CeO2 catalyst prepared in Example 1, the PtSnCu / C prepared in Comparative Example 1, and the commercial Pt / C were subjected to cyclic voltammetry (CV) curve tests. The obtained cyclic voltammetry (CV) curves are shown in FIG. Figure 5 As shown, continuous CV scanning is a method to evaluate stability. Figure 5 It can be seen that the PtSnCu / CeO2 catalyst prepared in Example 1 has an initial capacity of 1043.5 mA mg between -0.63 and 0.52 V (MOR) at a scan rate of 50 mV / s. Pt -1 , after 500 cycles, it can maintain 695.65 mA mg Pt -1The capacity retention rate is 66.9%, while the initial capacities of Pt / C and PtSnCu / C are 665 mA mg Pt -1 、435.5 mA mg Pt -1 , and after 500 cycles were 421 mA mg Pt -1 、409 mAmg Pt -1 , and capacity retention rates of 63.3% and 93.9%, respectively. This demonstrates CO tolerance and structural stability. The figure shows that the PtSnCu / CeO2 catalyst prepared in Example 1 exhibits superior CO poisoning resistance and electrochemical performance. The PtSnCu / CeO2 catalyst prepared in Example 1 exhibits low charge transfer resistance, high methanol oxidation (MOR) activity, and high CO tolerance in an acidic electrolyte. This is due to the combined properties of Sn, Cu, and CeO2 in the methanol oxidation reaction, which effectively optimize the catalyst's catalytic activity and CO poisoning resistance. The strong metal-support interaction (SMSI) between the PtSnCu alloy and CeO2 effectively modulates the Pt d-band center, thereby weakening the intermediate's adsorption capacity for *CO and *COOH. Furthermore, when Sn and Cu are added to the Pt catalyst, electrons transfer from Sn and Cu to Pt. This increases the electron cloud density on the Pt surface and the corresponding increase in the d orbital electron cloud density of the Pt atoms. The adsorption of CO molecules onto the Pt surface is achieved through the formation of σ bonds between the lone pair of electrons at the carbon end of CO and the empty d orbital of Pt, while the Pt d orbital electrons are fed back to the antibonding π orbital of CO to form π bonds. After the addition of Sn and Cu, the density of the Pt d orbital electron cloud increases, and more electrons are fed back to the CO antibonding π orbital, resulting in a weakening of the CO bond in the CO molecule and the adsorption bond strength between CO and Pt. This makes it easier for CO to desorb from the catalyst surface, improves the stability of the catalyst, and reduces the degradation and deactivation of the catalyst during fuel cell operation. CeO2 can provide additional oxygen species through the release and reoxidation of lattice oxygen, promoting the oxidation of intermediates such as CO, thereby improving the catalyst's resistance to CO poisoning. These synergistic mechanisms jointly drive the excellent methanol oxidation performance of PtSnCu / CeO2.

[0022] Example 2: The preparation method of the platinum-based alloy rare earth metal oxide fuel cell anode catalyst of this embodiment is carried out according to the following steps: 1. Preparation of CeO2 catalyst support material by hydrothermal synthesis: (1) Add 1 g of sodium chloride and 7.2 g of sodium hydroxide to 20 mL of distilled water and stir evenly to obtain solution A; add 0.652 g of cerium nitrate to 10 mL of water and stir evenly to obtain solution B; then slowly add solution B to solution A and stir for 30 minutes to mix evenly to obtain a mixed solution; (2) The mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal autoclave, which was placed in a forced air drying oven and maintained at 190 °C for 20 h for hydrothermal reaction. After the reaction was completed, the solid phase was centrifuged and washed three times with a 1:1 mixture of water and ethanol, and dried in a vacuum drying oven at 60 °C for 12 h to obtain a CeO2 precursor. (3) Grind the CeO2 precursor and place it in a porcelain boat, then place the porcelain boat in a tube furnace filled with argon, heat it to 400℃ and calcine it for 6h. After cooling, the CeO2 catalyst support material is obtained. 2. Add 1.335 mL of 0.0192 M chloroplatinic acid solution, 10 mg of copper chloride, 0.54 mL of 0.021 M stannous chloride and 20 mg of CeO2 catalyst support material into a round-bottom flask, then add 30 mL of ethylene glycol and 20 mL of ultrapure water, and mix them evenly by ultrasonication for 1 hour to obtain a precursor solution; place the precursor solution in an oil bath at 120 °C for 4 hours; separate the solid phase by centrifugation, wash it three times with ethanol, and dry it in a vacuum drying oven at 60 °C for 12 hours to obtain a platinum-based alloy rare earth metal oxide fuel cell catalyst material, recorded as PtSnCu / CeO2-400.

[0023] The same method as in Example 1 was used to test the initial capacity of the platinum-based alloy rare earth metal oxide fuel cell catalyst material PtSnCu / CeO2-400 prepared in Example 2 to be 1010.5 mA mg Pt -1 , the capacity after 500 cycles is maintained at 680.65 mA mg Pt -1 , the capacity retention rate is 67.4%.

[0024] Example 3: This example is a method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst, which is carried out according to the following steps: 1. Preparation of CeO2 catalyst support material by hydrothermal synthesis: (1) Add 1 g of sodium chloride and 7.2 g of sodium hydroxide to 20 mL of distilled water and stir to obtain solution A. Add 0.652 g of cerium nitrate to 10 mL of water and stir to obtain solution B. Then, slowly add solution B to solution A and stir for 30 min to mix well to obtain a mixed solution. (2) The mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal autoclave, which was placed in a forced air drying oven and maintained at 150 °C for 26 h for hydrothermal reaction. After the reaction was completed, the solid phase was centrifuged and washed three times with a 1:1 mixture of water and ethanol, and dried in a vacuum drying oven at 60 °C for 12 h to obtain a CeO2 precursor. (3) The CeO2 precursor was ground and placed in a porcelain boat, which was then placed in a tube furnace filled with argon gas. The temperature was raised to 900 °C and calcined for 2 h. After cooling, the CeO2 catalyst support material was obtained. 2. Add 1.335 mL of 0.0192 M chloroplatinic acid solution, 10 mg of copper chloride, 0.54 mL of 0.021 M stannous chloride and 20 mg of CeO2 catalyst support material into a round-bottom flask, then add 30 mL of ethylene glycol and 20 mL of ultrapure water, and mix them evenly by ultrasonication for 1 h to obtain a precursor solution; place the precursor solution in an oil bath at 150 °C for 2 h; separate the solid phase by centrifugation, wash it three times with ethanol, and dry it in a vacuum drying oven at 60 °C for 12 h to obtain a platinum-based alloy rare earth metal oxide fuel cell catalyst material, recorded as PtSnCu / CeO2-900.

[0025] The same method as in Example 1 was used to test the initial capacity of the platinum-based alloy rare earth metal oxide fuel cell catalyst material PtSnCu / CeO2-900 prepared in Example 3 to be 1163.2 mA mg Pt -1 , the capacity after 500 cycles is maintained at 820.4 mA mg Pt -1 , the capacity retention rate is 70.5%.

Claims

1. A method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst, characterized in that: The method proceeds as follows:

1. Preparation of CeO2 catalyst support material by hydrothermal synthesis: (1) Add sodium chloride and sodium hydroxide to distilled water and stir to obtain solution A; add cerium nitrate to water and stir to obtain solution B; then add solution B to solution A and stir to mix evenly; A mixed solution is obtained; (2) The mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal autoclave, which was placed in a blast drying oven and maintained at a temperature of 150-190 °C for 12-26 h for hydrothermal reaction. After the reaction was completed, the solid phase was centrifuged, washed, and vacuum-dried to obtain a CeO2 precursor. (3) Grind the CeO2 precursor and place it in a porcelain boat, then place the porcelain boat in a tube furnace filled with argon gas, heat it to 400~900℃ and calcine it for 2~6 hours. After cooling, the CeO2 catalyst support material is obtained.

2. The corresponding Pt, Sn, and Cu salt solutions used to prepare the PtSnCu alloy are mixed with the CeO2 catalyst carrier material, and then ethylene glycol and distilled water are added, and ultrasonic mixing is performed to obtain a precursor solution; the precursor solution is placed in an oil bath at 120-160°C for 1-4 hours; the solid phase is separated by centrifugation, and then washed and vacuum-dried to obtain a platinum-based alloy rare earth metal oxide fuel cell catalyst material, which is recorded as PtSnCu / CeO2.

2. The method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst according to claim 1, characterized in that: The hydrothermal treatment in step 1 (2) is performed at 180°C for 24 h.

3. The method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst according to claim 1 or 2, characterized in that: The vacuum drying in step 1 (2) is carried out in a vacuum drying oven at a temperature of 60-70°C for 8-12 hours.

4. The method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst according to claim 1 or 2, characterized in that: The calcination temperature in step 1 (3) is 600°C and the calcination time is 4 hours.

5. The method for preparing a platinum-based alloy rare earth metal oxide fuel cell anode catalyst according to claim 1 or 2, characterized in that: The oil bath temperature in step 2 is 140° C., and the oil bath time is 2 h.

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