Nitrogen-doped carbon carrier confined rhodium-praseodymium double-monatomic catalyst as well as preparation method and application thereof

Abstract

The invention provides a nitrogen-doped carbon carrier confined rhodium-praseodymium double-monatomic catalyst and a preparation method and application thereof.The preparation method includes the steps that 1, Zn (NO3) 2.6 H2O, a precursor of Rh and a precursor of Pr are dispersed in methyl alcohol, and a homogeneous solution A is obtained; the molar ratio of the Rh element to the Pr element is (10-11): (7-8); (2) dissolving 2-methylimidazole in methanol to obtain a homogeneous solution B; (3) mixing the homogeneous solution A and the homogeneous solution B, reacting under pressurization, and centrifuging a reaction product to obtain a first composite solid; (4) washing and drying the first composite solid, and then carrying out heat treatment to obtain a second composite solid; and (5) carrying out acid pickling, suction filtration, drying and grinding on the second composite solid to obtain the nitrogen-doped carbon carrier confined rhodium-praseodymium double-monatomic catalyst. The RhPr / NC double-monatomic catalyst shows excellent hydroxidability and long-term CO poisoning resistance stability under an acidic condition.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and particularly relates to a rhodium-praseodymium dual single-atom catalyst confined on a nitrogen-doped carbon support, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a high-energy-density, zero-carbon-emission secondary energy source, is a crucial direction for achieving global energy structure transformation. Fuel cells, a novel power generation technology that can directly and efficiently convert chemical energy into electrical energy, represent a significant application of hydrogen energy. Proton exchange membrane fuel cells (PEMFCs), due to their low operating temperature, high energy conversion efficiency, and rapid dynamic response capabilities, are considered one of the core technologies for future clean energy transportation and distributed power generation.

[0003] Currently, PEMFCs can only use expensive high-purity hydrogen as fuel on the anode side, instead of inexpensive crude hydrogen containing a small amount of CO. This cost-limiting factor restricts the widespread adoption of PEMFCs. This is because CO has extremely high adsorption strength at catalyst active sites (such as Pt, Rh, etc.). CO in H2 preferentially occupies reaction sites on the catalyst, thus hindering the adsorption of H2 and the catalyst (1 ppm CO in H2 can cause a surface blockage rate of over 90%), resulting in a significant suppression of the HOR process. CO molecules donate electrons to the empty orbitals of the metal through their 4σ and 5σ orbitals, and the metal d orbitals feed back electrons to the π antibonding orbitals of CO to form strong chemical adsorption bonds (Pt-CO, Rh-CO, etc.), making the active sites occupied and difficult to desorb, significantly reducing the battery's output power and durability.

[0004] Therefore, designing catalytic centers with low CO adsorption energies is an ideal approach to solving this problem. Simultaneously, since water is also a reactant in the electro-oxidation of CO, specific catalytic sites capable of activating water at sufficiently low potentials are required. However, currently available catalysts do not yet meet these stringent requirements. For example, the best CO-tolerant catalyst to date, PtRu / C, requires a high Pt content (>0.4 mg⋅cm⁻¹). -2 This technology aims to provide specific battery performance in the presence of CO, but its direction of operation is contrary to the need for cost reduction.

[0005] To address these challenges, researchers have proposed various control strategies, such as constructing bimetallic alloys or developing single-atom catalysts (SACs). Single-atom catalysts, by anchoring metal atoms in an atomically dispersed manner on a support, can significantly improve atom utilization and effectively control their electronic structure. However, since hydrogen dissociation typically requires synergistic action between adjacent bimetallic sites, single-atom catalysts still face significant challenges in efficiently catalyzing the hydrogen oxidation reaction (HOR). Against this backdrop, developing single-atom catalysts capable of simultaneously and stably catalyzing both HOR and CO electro-oxidation reactions (COOR), achieving full activation of CO and H2O at low potentials, holds significant research value and application prospects. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, its preparation method and application. The RhPr / NC dual single-atom catalyst prepared by this method exhibits excellent HOR activity and long-term CO poisoning resistance under acidic conditions.

[0007] This invention provides a method for preparing a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, comprising the following steps:

[0008] (1) Disperse Zn(NO3)2·6H2O, Rh precursor and Pr precursor in methanol to obtain homogeneous solution A; the molar ratio of Rh element to Pr element is (10~11):(7~8);

[0009] (2) Dissolve 2-methylimidazole in methanol to obtain homogeneous solution B;

[0010] (3) The homogeneous solution A and homogeneous solution B are mixed and reacted under pressure. The reaction product is centrifuged to obtain the first composite solid.

[0011] (4) The first composite solid is washed, dried and then heat-treated to obtain the second composite solid;

[0012] (5) The second composite solid is acid washed, filtered, dried and ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support confined to resist CO poisoning of proton exchange membrane fuel cell anode.

[0013] Preferably, the heat treatment temperature is 900~1000℃ and the time is 55~65min;

[0014] The heat treatment atmosphere is a mixture of H2 and Ar.

[0015] Preferably, the pressurized reaction is carried out in an autoclave;

[0016] The pressure reaction was carried out at a temperature of 115~125℃ for 3.5~4.5 hours.

[0017] Preferably, the mass-to-volume ratio of 2-methylimidazole to methanol is (0.65~0.66) g:15 mL.

[0018] Preferably, the precursor of Rh is Rh(acac)3;

[0019] The precursor of Pr is PrCl3·7H2O.

[0020] Preferably, the mass-to-volume ratio of Zn(NO3)2·6H2O, Rh(acac)3, PrCl3·6H2O and methanol in step (1) is (0.59~0.60) g: (53~54) mg: (34.5~35.5) mg: (7~8) mL.

[0021] Preferably, the acid used for pickling is perchloric acid; the concentration of perchloric acid is 0.09~0.111 mol / L; and the pickling time is 11~13 h.

[0022] Preferably, the filter cake is washed with ultrapure water during the filtration process in step (5);

[0023] The drying temperature is 55~65℃, and the drying time is 11~13h.

[0024] This invention provides a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, which is prepared by the method described in the above technical solution.

[0025] This invention provides an application of the nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst prepared by the preparation method described above in the CO poisoning resistance of the anode of a proton exchange membrane fuel cell.

[0026] This invention provides a method for preparing a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, comprising the following steps: (1) dispersing Zn(NO3)2·6H2O, Rh precursor, and Pr precursor in methanol to obtain a homogeneous solution A; the molar ratio of Rh element to Pr element is (10~11):(7~8); (2) dissolving 2-methylimidazole in methanol to obtain a homogeneous solution B; (3) mixing the homogeneous solution A and homogeneous solution B and reacting under pressure, centrifuging the reaction product to obtain a first composite solid; (4) washing the first composite solid, drying it, and then heat-treating it to obtain a second composite solid; (5) acid washing, filtration, drying, and grinding the second composite solid to obtain a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst suitable for CO poisoning resistance of proton exchange membrane fuel cell anodes. Experimental results show that the RhPr / NC dual single-atom catalyst prepared by the method of this invention exhibits excellent HOR activity and long-term CO poisoning resistance stability under acidic conditions. Compared to traditional commercial Rh / C catalysts, this invention exhibits a more than one-order-of-magnitude improvement in mass activity and a significantly enhanced structural stability. The method described in this invention is simple, produces no organic solvent pollution, and is suitable for large-scale production, providing a new technical approach for the development of high-performance electrocatalysts for fuel cell anodes. Attached Figure Description

[0027] Figure 1 The X-ray diffraction (XRD) pattern of the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes provided in Example 1 of the present invention;

[0028] Figure 2 This is a high-angle annular dark-field scanning transmission electron microscope image of a rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes, provided in Example 1 of the present invention.

[0029] Figure 3 Linear sweep voltammetric curves of the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes provided in Example 1 of the present invention in 0.1 M perchloric acid solution;

[0030] Figure 4 The potentiostatic stability test curve of the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes provided in Example 1 of the present invention in a 0.1 M perchloric acid solution containing 1000 ppm CO / H2 mixed gas. Detailed Implementation

[0031] This invention provides a method for preparing a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, comprising the following steps:

[0032] (1) Disperse Zn(NO3)2·6H2O, Rh precursor and Pr precursor in methanol to obtain homogeneous solution A; the molar ratio of Rh element to Pr element is (10~11):(7~8);

[0033] (2) Dissolve 2-methylimidazole in methanol to obtain homogeneous solution B;

[0034] (3) The homogeneous solution A and homogeneous solution B are mixed and reacted under pressure. The reaction product is centrifuged to obtain the first composite solid.

[0035] (4) The first composite solid is washed, dried and then heat-treated to obtain the second composite solid;

[0036] (5) The second composite solid is acid washed, filtered, dried and ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support confined to resist CO poisoning of proton exchange membrane fuel cell anode.

[0037] This invention synthesizes a nitrogen-doped carbon-supported Rh-Pr dual single-atom catalyst by co-assembling Rh and Pr precursors in the presence of a metal-organic framework template, followed by high-temperature pyrolysis and acid washing under an inert atmosphere. This method effectively prevents the aggregation or metallization of Rh and Pr atoms through spatial confinement, ensuring that both are uniformly dispersed in the carbon framework in single-atom form.

[0038] This invention disperses Zn(NO3)2·6H2O, Rh precursors, and Pr precursors in methanol to obtain a homogeneous solution A. In this invention, the Rh precursor is Rh(acac)3; the Pr precursor is PrCl3·7H2O. The molar ratio of Rh to Pr in this invention is (10~11):(7~8); by adjusting the ratio of Rh to Pr, the metal mass fraction in the catalyst can reach up to 1 wt%, while still maintaining a single-atom-level dispersion.

[0039] In this invention, the mass-to-volume ratio of Zn(NO3)2·6H2O, Rh(acac)3, PrCl3·6H2O, and methanol is (0.59~0.60) g:(53~54) mg:(34.5~35.5) mg:(7~8) mL, preferably (0.592~0.598) g:(53.2~53.6) mg:(34.8~35.3) mg:(7.2~7.8) mL. In a specific embodiment, the mass-to-volume ratio of Zn(NO3)2·6H2O, Rh(acac)3, PrCl3·6H2O, and methanol is 0.594 g:53.3 mg:35 mg:7.5 mL.

[0040] In this invention, 2-methylimidazole is dissolved in methanol to obtain a homogeneous solution B. In this invention, the mass-to-volume ratio of 2-methylimidazole to methanol is (0.65~0.68) g:15 mL, preferably (0.655~0.68) g:15 mL; in specific embodiments, the mass-to-volume ratio of 2-methylimidazole to methanol is 0.656 g:15 mL or 0.68 g:15 mL.

[0041] There is no restriction on the order in which homogeneous solution A and homogeneous solution B are prepared in this invention.

[0042] In this invention, homogeneous solution A and homogeneous solution B are mixed and reacted under pressure. The reaction product is then centrifuged to obtain a first composite solid.

[0043] In this invention, homogeneous solution A and homogeneous solution B are mixed under vigorous stirring; the mixing time is 4 to 6 minutes, specifically 4 minutes, 5 minutes or 6 minutes.

[0044] The mixed materials are transferred to an autoclave for heating. The temperature of the pressurized reaction is 115~125℃, specifically 115℃, 120℃ or 125℃; the time is 3.5~4.5h, specifically 3.5h, 4h or 4.5h.

[0045] This invention involves washing and drying the first composite solid, followed by heat treatment to obtain a second composite solid. The first composite solid is washed with methanol, preferably at least three times, specifically three, four, five, or six times. It is then dried overnight. The dried composite solid is then placed in a tube furnace for heat treatment at a temperature of 900–1000°C, specifically 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, or 1000°C; for a time of 55–65 min, specifically 55 min, 60 min, or 65 min. The heat treatment atmosphere is a mixture of H2 and Ar, specifically a mixture of 5 vol% H2 and 95 vol% Ar. The heating rate is 4–6°C / min, specifically 4°C / min, 5°C / min, or 6°C / min.

[0046] After obtaining the second composite solid, the present invention performs acid washing, filtration, drying and grinding on the second composite solid to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support confined for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0047] The preferred acid used for pickling in this invention is perchloric acid; the concentration of perchloric acid is 0.09~0.11 mol / L, specifically 0.09 mol / L, 0.10 mol / L, or 0.11 mol / L; the pickling time is 11~13 h, specifically 11 h, 12 h, or 13 h. In a specific embodiment, the concentration of perchloric acid is 0.1 mol / L, and the pickling time is 12 h.

[0048] This invention introduces Rh(acac)3 and Pr(acac)3 into the ZIF-8 framework, followed by inert atmosphere pyrolysis and subsequent acid washing, to form a stable RhPr double single-atom structure in situ on the nitrogen-doped carbon framework, thereby achieving atomic-scale electronic and interface synergistic control.

[0049] The separation method after acid washing in this invention is vacuum filtration, and the filter cake is washed with ultrapure water. After vacuum filtration, the product is dried and ground to obtain a rhodium-praseodymium dual single-atom catalyst. Under acidic conditions, the RhPr / NC catalyst, which exhibits excellent hydrogen oxidation (HOR) and CO electro-oxidation (COOR) activities due to the synergistic catalysis of Rh and Pr dual single atoms, has an onset oxidation potential as low as 0 V vs. RHE.

[0050] Compared with existing single-metal Rh or commercial noble metal catalysts, this invention introduces the rare earth element Pr as a synergistic regulatory center for the first time, utilizing its variable valence characteristic (Pr 3+ / Pr 4+ By leveraging the strong hydrophilicity of the Rh active center, the electronic structure and interfacial polarity can be dually controlled, thereby significantly reducing CO adsorption intensity and promoting *OH formation. This strategy effectively enhances the reaction kinetics and anti-poisoning performance of the catalyst in small molecule oxidation reactions (such as formic acid oxidation).

[0051] This invention provides a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, which is prepared by the method described in the above technical solution.

[0052] The Rh-Pr dual single-atom catalyst based on nitrogen-doped carbon confined structure provided by this invention can effectively overcome the CO poisoning problem of traditional noble metal catalysts while maintaining high activity and high stability, providing a new solution for developing efficient and durable PEMFC anode electrocatalytic materials.

[0053] This invention provides an application of the nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst prepared by the preparation method described above in the CO poisoning resistance of the anode of a proton exchange membrane fuel cell.

[0054] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a nitrogen-doped carbon-supported confined rhodium-praseodymium dual single-atom catalyst, its catalyst, and its applications, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] Homogeneous solution A was prepared by dissolving Zn(NO3)2·6H2O (0.594 g), Rh(acac)3 (53.3 mg), and PrCl3·7H2O (35 mg) in 7.5 mL of methanol at room temperature. Simultaneously, homogeneous solution B was prepared by dissolving 2-methylimidazole (0.656 g) in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a mixture of 5% H2 and Ar gas at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. Subsequently, the filter cake was etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species. Then, it was filtered and washed with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h. Finally, it was ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0057] The present invention performs X-ray analysis on the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes, as described in Example 1. Figure 1 As shown, no characteristic peaks of rhodium, praseodymium, or their metals and oxides were detected in the obtained catalyst, indicating that rhodium and praseodymium were highly dispersed in single-atom form on the nitrogen-doped carbon support, proving the formation of a stable Rh and Pr double single-atom structure.

[0058] The rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes, as described in Example 1, was characterized by spherical aberration electron microscopy. The results are as follows: Figure 2 As shown, no aggregation of Rh and Pr was observed in the obtained catalyst, demonstrating its single-atom dispersion characteristics.

[0059] The present invention presents linear sweep voltammetry (LSV) curves of the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes, as described in Example 1. Figure 3As shown, the catalyst exhibits excellent hydrogenation activity, with an onset potential as low as 0 V vs. RHE and reaching the limiting current density at 0.1 V vs. RHE.

[0060] The present invention tested the potential stability of the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes in Example 1 under conditions containing 1000 ppm CO / H2 mixed gas. The results showed that RhPr / NC had the highest current retention rate and the smallest decay, demonstrating excellent long-term stability and CO poisoning resistance.

[0061] Example 2

[0062] Homogeneous solution A was prepared by dissolving Zn(NO3)2·6H2O (0.594 g), Rh(acac)3 (55 mg), and PrCl3·7H2O (35 mg) in 7.5 mL of methanol at room temperature. Simultaneously, homogeneous solution B was prepared by dissolving 2-methylimidazole (0.656 g) in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a mixture of 5% H2 and Ar gas at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. Subsequently, the filter cake was etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species. Then, it was filtered and washed with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h. Finally, it was ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0063] The present invention analyzed the rhodium-praseodymium double single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes in Example 2 using X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability tests. The results were similar to those in Example 1.

[0064] Example 3

[0065] Zn(NO3)2·6H2O (0.594 g), Rh(acac)3 (53.3 mg), and PrCl3·7H2O (37 mg) were dissolved in 7.5 mL of methanol at room temperature to prepare homogeneous solution A. Simultaneously, 2-methylimidazole (0.656 g) was dissolved in 15 mL of methanol to prepare homogeneous solution B. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a 5% H2 and Ar gas mixture at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. Subsequently, the filter cake was etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species. Then, it was filtered and washed with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h. Finally, it was ground to obtain a rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support suitable for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0066] The present invention analyzed the rhodium-praseodymium double single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes in Example 3 using X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability tests. The results were similar to those in Example 1.

[0067] Example 4

[0068] Homogeneous solution A was prepared by dissolving Zn(NO3)2·6H2O (0.6 g), Rh(acac)3 (53.3 mg), and PrCl3·7H2O (35 mg) in 7.5 mL of methanol at room temperature. Simultaneously, homogeneous solution B was prepared by dissolving 2-methylimidazole (0.656 g) in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a mixture of 5% H2 and Ar gas at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. Subsequently, the filter cake was etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species. Then, it was filtered and washed with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h. Finally, it was ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0069] The present invention analyzed the rhodium-praseodymium double single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes in Example 4 using X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability tests. The results were similar to those in Example 1.

[0070] Example 5

[0071] A homogeneous solution A was prepared by dissolving Zn(NO3)2·6H2O (0.594 g), Rh(acac)3 (53.3 mg), and PrCl3·7H2O (35 mg) in 7.5 mL of methanol at room temperature. Simultaneously, a homogeneous solution B was prepared by dissolving 2-methylimidazole (0.68 g) in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a mixture of 5% H2 and Ar gas at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. Subsequently, the filter cake was etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species. Then, it was filtered and washed with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h. Finally, it was ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0072] The present invention analyzed the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in the anode of a proton exchange membrane fuel cell in Example 5 by X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability test. The results were similar to those in Example 1.

[0073] Example 6

[0074] Homogeneous solution A was prepared by dissolving 0.594 g of Zn(NO3)2·6H2O, 53.3 mg of Rh(acac)3, and 3.8 mL of 25 mmol / L PrCl3 methanol solution in 7.5 mL of methanol at room temperature. Simultaneously, homogeneous solution B was prepared by dissolving 0.656 g of 2-methylimidazole in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a mixture of 5% H2 and Ar gas at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. It was then etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species, followed by filtration and washing of the filter cake with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h, and finally ground to obtain a rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support suitable for CO poisoning resistance in proton exchange membrane fuel cell anodes.

[0075] The present invention analyzed the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in proton exchange membrane fuel cell anodes using X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability test of the nitrogen-doped carbon support catalyst of Example 6, and the results were similar to those of Example 1.

[0076] Example 7

[0077] Homogeneous solution A was prepared by dissolving 0.594 g of Zn(NO3)2·6H2O, 3.8 mL of 35 mmol / L Rh(acac)3 methanol solution, and 35 mg of PrCl3·7H2O in 7.5 mL of methanol at room temperature. Simultaneously, homogeneous solution B was prepared by dissolving 0.656 g of 2-methylimidazole in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a mixture of 5% H2 and Ar gas at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. It was then etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species, followed by filtration and washing of the filter cake with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h, and finally ground to obtain a rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support suitable for CO poisoning resistance in proton exchange membrane fuel cell anodes.

[0078] The present invention analyzed the rhodium-praseodymium double single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in the anode of a proton exchange membrane fuel cell in Example 7 using X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability test. The results were similar to those in Example 1.

[0079] Example 8

[0080] A homogeneous solution A was prepared by dissolving Zn(NO3)2·6H2O (0.594 g), Rh(acac)3 (53.3 mg), and PrCl3·7H2O (35 mg) in 7.5 mL of methanol at room temperature. Simultaneously, a homogeneous solution B was prepared by dissolving 2-methylimidazole (0.64 g) in 15 mL of methanol. The two solutions were vigorously stirred for 5 minutes and then mixed. The mixture was then transferred to a 50 mL Teflon-lined stainless steel autoclave. The autoclave was heated at 120 °C for 4 h. After the reaction was complete, the first composite solid was collected by centrifugation, washed four times with methanol, and vacuum dried overnight at 60 °C. The resulting product was the second composite solid, RhPr@ZIF-8. The second composite solid was placed in a tube furnace and heat-treated at 950 °C for 1 h in a 5% H2 and Ar gas mixture at a heating rate of 5 °C / min. After cooling to room temperature, the resulting material was RhPr / NC. Subsequently, the filter cake was etched with 0.1 M perchloric acid solution for 12 h to remove unstable metal species. Then, it was filtered and washed with 2.5 L of ultrapure water. The filter cake was then dried in a forced-air drying oven for 12 h. Finally, it was ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support for CO poisoning resistance of proton exchange membrane fuel cell anodes.

[0081] The present invention analyzed the rhodium-praseodymium dual single-atom catalyst confined to a nitrogen-doped carbon support for CO poisoning resistance in the anode of a proton exchange membrane fuel cell in Example 8 by X-ray diffraction, spherical aberration electron microscopy, linear scanning voltammetry, and constant potential stability test. The results were similar to those in Example 1.

[0082] As can be seen from the above embodiments, the present invention provides a method for preparing a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, comprising the following steps: (1) dispersing Zn(NO3)2·6H2O, Rh precursor and Pr precursor in methanol to obtain homogeneous solution A; the molar ratio of Rh element to Pr element is (10~11):(7~8); (2) dissolving 2-methylimidazole in methanol to obtain homogeneous solution B; (3) mixing the homogeneous solution A and homogeneous solution B and reacting under pressure, centrifuging the reaction product to obtain a first composite solid; (4) washing the first composite solid, drying and heat-treating to obtain a second composite solid; (5) acid washing, filtration, drying and grinding the second composite solid to obtain a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst suitable for CO poisoning resistance of proton exchange membrane fuel cell anodes. Experimental results show that the RhPr / NC dual single-atom catalyst prepared by the method of this invention exhibits excellent hydrogen oxidative stress (HOR) activity and long-term resistance to CO poisoning under acidic conditions. Compared with traditional commercial Rh / C catalysts, its mass activity is increased by more than an order of magnitude, and its structural stability is significantly enhanced. The method of this invention is simple, produces no organic solvent pollution, and is suitable for large-scale production, providing a new technical approach for the development of high-performance electrocatalysts for fuel cell anodes.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, comprising the following steps: (1) Disperse Zn(NO3)2·6H2O, Rh precursor and Pr precursor in methanol to obtain homogeneous solution A; the molar ratio of Rh element to Pr element is (10~11):(7~8); (2) Dissolve 2-methylimidazole in methanol to obtain homogeneous solution B; (3) The homogeneous solution A and homogeneous solution B are mixed and reacted under pressure. The reaction product is centrifuged to obtain the first composite solid. (4) The first composite solid is washed, dried and then heat-treated to obtain the second composite solid; (5) The second composite solid is acid washed, filtered, dried and ground to obtain a rhodium-praseodymium dual single-atom catalyst with nitrogen-doped carbon support confined to resist CO poisoning of proton exchange membrane fuel cell anode.

2. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 900~1000℃, and the time is 55~65min; The heat treatment atmosphere is a mixture of H2 and Ar.

3. The preparation method according to claim 1, characterized in that, The pressurized reaction is carried out in an autoclave; The temperature of the pressurized reaction is 115~125℃, and the time is 3.5~4.5h.

4. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of 2-methylimidazole to methanol is (0.65~0.66) g:15 mL.

5. The preparation method according to claim 1, characterized in that, The precursor of Rh is Rh(acac)3; The precursor of Pr is PrCl3·7H2O.

6. The preparation method according to claim 5, characterized in that, The mass-to-volume ratio of Zn(NO3)2·6H2O, Rh(acac)3, PrCl3·6H2O and methanol in step (1) is (0.59~0.60) g: (53~54) mg: (34.5~35.5) mg: (7~8) mL.

7. The preparation method according to claim 1, characterized in that, The acid used for pickling is perchloric acid; the concentration of perchloric acid is 0.09~0.111 mol / L; and the pickling time is 11~13 h.

8. The preparation method according to claim 1, characterized in that, The filter cake is washed with ultrapure water during the filtration process described in step (5); The drying temperature is 55~65℃, and the drying time is 11~13h.

9. A nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst, prepared by the method described in any one of claims 1 to 8.

10. The application of a nitrogen-doped carbon-supported rhodium-praseodymium dual single-atom catalyst prepared by the preparation method according to any one of claims 1 to 8 in CO poisoning resistance of the anode of a proton exchange membrane fuel cell.

Images