Modified rh crystal catalyst, its preparation method and application

Abstract

The application discloses a modified Rh crystal catalyst and a preparation method and application thereof. The catalyst comprises a carrier Rh icosahedral twin crystal and Ru monatomic atoms loaded on the Rh icosahedral twin crystal, wherein Rh is zero-valence, and Ru exists in a divalent form; the preparation method comprises the following steps: (1) polyvinylpyrrolidone is dissolved in trioxa tetraethylene glycol solvent, preheating is carried out under stirring at 250-270 DEG C, then rhodium salt is slowly added, and a black Rh icosahedral twin crystal is obtained through reaction; (2) the Rh icosahedral twin crystal powder prepared in the step (1) is dispersed in an aqueous solvent with ruthenium salt, is mixed uniformly, active carbon is added, is dispersed uniformly, high-temperature calcination is carried out under a nitrogen atmosphere, and the catalyst is obtained through cooling. The catalyst takes the icosahedral rhodium crystal as a carrier, loads monatomic ruthenium on the icosahedral twin crystal, and through improvement of the rhodium crystal structure and synergistic effect of the ruthenium, the oxidation electrocatalytic performance and stability of the catalyst to methanol are improved.

Description

Technical Field

[0001] This invention relates to a catalyst, and more particularly to a modified Rh crystal catalyst, its preparation method, and its application. Background Technology

[0002] Direct methanol fuel cells are among the most promising clean energy devices. When the cell operates, the methanol oxidation reaction (MOR) occurs at the anode, and its efficiency directly determines the overall electrochemical conversion efficiency of the device. Currently, platinum-based nanomaterials are widely accepted electrocatalysts for methanol oxidation. However, platinum-based nanomaterials suffer from drawbacks such as limited resources, high cost, and susceptibility to methanol poisoning, which significantly hinder their large-scale commercial application. Therefore, the research and development of non-platinum electrocatalysts with high activity and high stability has broad application prospects and has become a hot research topic.

[0003] Studies have shown that Rh-based nanocrystals exhibit a more preferential MOR kinetic than Pt for the methanol oxidation reaction, making them a promising class of electrocatalysts. To further enhance the catalytic activity of Rh-based nanocrystals, morphological and crystal facet control is an effective approach. Among them, nanocrystals with a five-fold twin structure exhibit higher reactivity than those with low-index crystal faces due to their clearly defined high-index crystal faces and surface tensile strain. However, obtaining Rh nanocrystals with a five-fold twin structure remains a significant challenge due to the excellent thermal stability and readily available low surface energy of metallic Rh. Furthermore, the methanol oxidation reaction readily produces the intermediate product CO, which adsorbs onto the surface of Rh nanocrystals, causing poisoning and deactivation, thus greatly limiting the development of Rh-based electrocatalysts. Summary of the Invention

[0004] Objectives of the Invention: The first objective of this invention is to provide a modified Rh crystal catalyst that improves the electrocatalytic performance and stability of crystalline oxygen reduction; the second objective of this invention is to provide a method for preparing the modified Rh crystal catalyst; and the third objective of this invention is to provide the application of the modified Rh crystal catalyst in fuel cell catalysts.

[0005] Technical solution: The modified Rh crystal catalyst of the present invention includes a support Rh decahedral twin and Ru single atoms supported on the Rh decahedron, wherein Rh is zero-valent and Ru exists in divalent form.

[0006] Preferably, the catalyst contains 2-10% Ru atoms.

[0007] The preparation method of the modified Rh crystal catalyst of the present invention includes the following steps:

[0008] (1) Polyvinylpyrrolidone was dissolved in tetraethylene glycol solvent, stirred and preheated at 250-270°C, and then rhodium salt was slowly added to the reaction to obtain black Rh decahedral twins.

[0009] (2) Disperse the powder obtained in step (1) and ruthenium salt in an aqueous solvent, mix them evenly, add activated carbon, disperse them evenly, calcine them at high temperature under a nitrogen atmosphere, and cool to obtain the final product.

[0010] In step (1), tetraethylene glycol is used as the solvent, polyvinylpyrrolidone is used as the morphology directing agent, and rhodium acetylacetonate (C) is used as the solvent. 15 H 21 O6Rh) is a metal precursor salt. Rh decahedral twins are synthesized based on a solvothermal method. The mixture is first preheated at 250-270℃ to allow polyvinylpyrrolidone (PVP) to dissolve more fully in tetraethylene glycol, and then reacted at this temperature to obtain Rh decahedral twins.

[0011] Preferably, in step (1), the reaction time is 3 to 24 hours; the rhodium salt is rhodium acetylacetonate, and the mass ratio of polyvinylpyrrolidone to rhodium acetylacetonate is (20 to 100):1.

[0012] Preferably, in step (2), the high-temperature calcination temperature is 200-500℃, the heating rate is 1-5℃ / min, and the calcination time is 1-4 hours.

[0013] Preferably, the ruthenium salt is K4[Ru(CN)6], and the mass ratio of the Rh decahedral twin to K4[Ru(CN)6] is 5:1 to 4.

[0014] In step (2), ruthenium salt K4[Ru(CN)6] is used as an example, and [Ru(CN)6] is adsorbed using an electrostatic adsorption method. 4- The resulting [Ru(CN)6] is loaded onto an Rh decahedron. 4- @Rh is ultrasonically loaded onto activated carbon, calcined at high temperature in an inert atmosphere, and then cooled to obtain the final product Ru SAs@Rh Dhs. Activated carbon serves as the dispersion medium, dispersing [Ru(CN)6]. 4- @Rh loaded on activated carbon facilitates calcination and maintains good dispersion of crystal particles. Pure metals tend to agglomerate after calcination and have poor conductivity.

[0015] The application of the modified Rh crystal catalyst described in this invention in fuel cell catalysts.

[0016] Mechanism of Invention: Traditional single-atom alloys often lack regular morphology and crystal faces, resulting in low activity of the metal support itself and limited regulation of single-atom sites. The modified Rh crystal catalyst Ru SAs@Rh Dhs of this invention has a well-defined and regular five-fold twin structure with ten high-index (211) twin interfaces, inherently possessing high intrinsic activity. Furthermore, the twin surface has strong tensile stress, which enhances the adsorption of oxygen-containing intermediates and promotes MOR kinetics. The uniformly dispersed Ru single atoms on the Rh decahedron have excellent water-splitting ability. The OH- produced by decomposition can not only act as reactants to drive MOR kinetics but also help promote the conversion of CO to CO2 on the Rh decahedron. Moreover, Ru exists in single-atom form, which can minimize the obscuring of the surface atoms of the Rh decahedral twins, greatly reducing the mass-specific activity loss.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The catalyst uses decahedral rhodium crystal as a support and loads single-atom ruthenium on the decahedron. Through the improvement of the rhodium crystal structure and the synergistic effect with ruthenium, its electrocatalytic performance and stability for methanol oxidation are improved; (2) The preparation method is simple and easy to industrialize; (3) When applied to methanol fuel cells, it exhibits beneficial activity and excellent electrochemical durability. It can promote the CO generated during the methanol oxidation reaction and extend the service life of the catalyst. It is a fuel cell catalyst with great potential and broad application prospects in the future energy industry. Attached Figure Description

[0018] Figure 1 HAADF-STEM (1a) and HRTEM (1b) images of Ru SAs@Rh Dhs prepared for Example 1;

[0019] Figure 2 HRTEM magnified image of Ru SAs@Rh Dhs prepared in Example 1;

[0020] Figure 3 Mapping diagram of Ru SAs@Rh Dhs prepared in Example 1;

[0021] Figure 4 XRD pattern of Ru SAs@Rh Dhs prepared in Example 1;

[0022] Figure 5 XPS spectra of Ru SAs@Rh Dhs prepared in Example 1;

[0023] Figure 6 A comparison of the electrocatalytic activities of Ru SAs@Rh Dhs prepared in Example 1, Ru Dhs prepared in Comparative Example 1, and commercial 20% Pt / C for methanol oxidation.

[0024] Figure 7 Accelerated durability test results for Ru SAs@Rh Dhs prepared in Example 1;

[0025] Figure 8 The carbon monoxide adsorption-desorption curves of Ru SAs@Rh Dhs prepared in Example 1 are shown. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the embodiments.

[0027] Example 1

[0028] (1) The modified Rh crystal catalyst of the present invention is prepared by the following steps: Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO). n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0029] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 2 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0030] Example 2

[0031] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0032] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0033] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 2 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 2 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0034] Example 3

[0035] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0036] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0037] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 2 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 1 hour, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0038] Example 4

[0039] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0040] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0041] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 2 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 350°C for heat treatment, held at this temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0042] Example 5

[0043] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0044] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0045] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 2 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 400℃ for heat treatment, held at this temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0046] Example 6

[0047] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0048] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0049] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and simultaneously weigh 2 mg of K4[Ru(CN)6], disperse them together in 20 mL of water, stir for 1 h, then add 40 mg of activated carbon and ultrasonically disperse for 3 h. Under a nitrogen atmosphere, at 4 °C for min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0050] Example 7

[0051] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0052] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0053] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 2 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 6 °C for 1 min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0054] Example 8

[0055] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0056] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0057] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 4 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0058] Example 9

[0059] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0060] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0061] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 6 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1The temperature is raised to 300℃ for heat treatment, held at that temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0062] Example 10

[0063] The modified Rh crystal catalyst of the present invention is prepared by means of the following steps:

[0064] (1) Preparation of Rh decahedral twins: Weigh 1g of polyvinylpyrrolidone (C6H9NO) n Add to 5 mL of tetraethylene triethylene glycol (C8H) 15 Dissolve the compound in O5 solvent by thorough sonication. Then preheat at 260°C for 20 minutes, followed by the addition of 10 mg of rhodium acetylacetone (C). 15 H 21 O6Rh), 2 mL tetraethylene glycol (C8H) 15 After stirring at 1600 rpm for 3 hours, the sample was taken out, cooled, centrifuged and dried to obtain Rh decahedral twins with a diameter of 7 nm.

[0065] (2) Preparation of Ru SAs@Rh Dhs: Weigh 10 mg of the above-mentioned Rh decahedral twin crystals and 8 mg of K4[Ru(CN)6] and disperse them together in 20 mL of water. After stirring for 1 h, add 40 mg of activated carbon and sonicate for 3 h. Under a nitrogen atmosphere, at 2 °C for 1 min -1 The temperature is raised to 300℃ for heat treatment, held at that temperature for 3 hours, and then cooled to room temperature to obtain RuSAs@Rh Dhs.

[0066] Comparative Example 1

[0067] Based on Example 1, step (2) does not include K4[Ru(CN)6], and the other conditions remain unchanged.

[0068] Structural characterization

[0069] The Ru SAs@RhDhs prepared in Example 1 were physically characterized using HAADF-STEM, HRTEM, mapping, XRD, and XPS. The results are as follows: Figures 1-3 As shown.

[0070] Depend on Figure 1 Large-area HADDDF-STEM Figure 1 a) and HRTEM Figure 1 b) It can be seen that the catalyst prepared in Example 1 is a decahedral twin uniformly dispersed on a carbon sheet, and the size of a single twin is 7 nm.

[0071] Depend on Figure 2 Further magnified HRTEM image ( Figure 2 a and Figure 2 b) It can be seen that the Ru SAs@Rh Dhs prepared in Example 1 has a fivefold twin structure, wherein the lattice spacing at the twin boundary is 0.23 nm, corresponding to the (111) crystal plane of Rh.

[0072] Depend on Figure 3 Mapping data shows that the Ru SAs@Rh Dhs prepared in Example 1 has two metal components, Rh and Ru.

[0073] Depend on Figure 4 The XRD pattern shows that the diffraction peaks of Ru SAs@Rh Dhs prepared in Example 1 are in perfect agreement with the standard card of Rh (JCPDS card, 65-6174), proving that Rh is a crystalline structure and Ru exists in a single-atom form.

[0074] Depend on Figure 5 XPS spectra show that Rh in the Ru SAs@Rh Dhs prepared in Example 1 exists mainly in the zero-valent form, while Ru exists mainly in the divalent form.

[0075] The Ru content in the Ru SAs@Rh Dhs prepared in Examples 1 and 8–10 was tested using an inductively coupled plasma atomic emission spectrometer. The molar fractions of Ru atoms were 2.4%, 4.7%, 7.2%, and 9.7%, respectively.

[0076] Performance Characterization

[0077] The mass-to-specific activity and area-to-specific activity of the Ru SAs@Rh Dhs prepared in Example 1, the Rh Dhs prepared in Comparative Example 1, and the commercial 20% Pt / C catalyst for methanol oxidation were tested.

[0078] The electrocatalytic methanol oxidation test method includes the following steps:

[0079] (1) Preparation of electrocatalytic electrode: Weigh 5 mg of the catalyst solid powder prepared in Example 1, Comparative Example 1 and commercial Pt / C respectively, add 670 μL of water, 300 μL of anhydrous ethanol and 30 μL of 5 wt% Nafion solution, and sonicate for 1 h to make it completely and evenly dispersed. Take 10 μL of the above solution and add it dropwise to the polished glassy carbon electrode surface, and let it air dry for later use;

[0080] (2) Electrocatalytic test: The electrocatalytic performance of the methanol oxidation reaction in this invention was mainly tested by cyclic voltammetry (CV). The electrolytes were 1M KOH solution and 1M KOH + 1M CH3OH solution. The voltage scan range was 0.7–1.27 V, and the scan rate was 50 mV·s. -1After multiple cycles until the test curve stabilizes, it can be used as the CV curve for methanol catalytic oxidation. The peak current density and onset potential are used to evaluate the electrocatalytic activity of the catalyst. The test results are as follows: Figures 6-8 As shown.

[0081] like Figure 6 The mass activity of Ru SAs@Rh Dhs was found to be 780.0 mA mg. -1 The mass activity of Rh Dhs was 225.2 mA mg. -1 The mass specific activity of 20% Pt / C is 361.4 mA mg. -1 The activity of Ru SAs@Rh Dhs is 3.46 times that of Rh Dhs and 2.16 times that of the commercial 20% Pt / C catalyst, which shows that Ru SAs@Rh Dhs exhibits superior activity.

[0082] like Figure 7 As shown, after 1000 cycles of accelerated durability stability testing, the methanol oxidation activity of Ru SAs@Rh Dhs remained almost unchanged, indicating that it has excellent electrochemical durability.

[0083] Depend on Figure 8 According to the CO dissolution voltammetry, Ru SAs@Rh Dhs also has excellent anti-poisoning properties, which can promote the conversion of intermediate product CO during the methanol oxidation reaction and extend the catalyst life.

Claims

1. A modified Rh crystal catalyst, characterized in that, The catalyst comprises a support Rh decahedral twin and Ru single atoms supported on the Rh decahedron, wherein Rh is zero-valent and Ru exists in divalent form, and the molar fraction of Ru atoms in the catalyst is 2-10%.

2. A method for preparing the modified Rh crystal catalyst according to claim 1, characterized in that, Includes the following steps: (1) Dissolve polyvinylpyrrolidone in tetraethylene glycol solvent at 250~270°C. o The mixture was preheated under temperature C by stirring, and then rhodium salt was slowly added. The reaction yielded black Rh decahedral twins. (2) Disperse the Rh decahedral twin powder obtained in step (1) with ruthenium salt in an aqueous solvent, mix evenly, add activated carbon, disperse evenly, calcine at high temperature under nitrogen atmosphere, and cool to obtain the final product Ru SAs@Rh Dhs.

3. The method for preparing the modified Rh crystal catalyst according to claim 2, characterized in that, In step (2), the ruthenium salt is K4[Ru(CN)6].

4. The preparation method according to claim 3, characterized in that, The mass ratio of the Rh decahedral twin to K4[Ru(CN)6] is 5:1~4.

5. The method for preparing the modified Rh crystal catalyst according to claim 2, characterized in that, In step (2), the high-temperature calcination temperature is 200~500℃ and the calcination time is 1~4 hours.

6. The method for preparing the modified Rh crystal catalyst according to claim 2, characterized in that, In step (1), the reaction time is 3 to 24 hours.

7. The method for preparing the modified Rh crystal catalyst according to claim 2, characterized in that, In step (1), the rhodium salt is rhodium acetylacetonate.

8. The method for preparing the modified Rh crystal catalyst according to claim 7, characterized in that, In step (1), the mass ratio of polyvinylpyrrolidone to rhodium acetylacetonate is (20-100):

1.

9. The application of the modified Rh crystal catalyst according to claim 1 in a fuel cell catalyst.

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