A rare earth metal oxide coupled ruthenium-based catalyst and its preparation method and application

Abstract

The present invention discloses a rare earth metal oxide-coupled ruthenium-based catalyst, its preparation method, and application. The preparation method uses europium chloride and ruthenium acetylacetonate as metal sources and polyacrylonitrile as a carbon and nitrogen source. A Ru / Eu2O3 hybrid nanofiber material is pre-prepared through an electrospinning process. After pre-oxidation, the material is subjected to carbothermal reduction in a high-temperature inert atmosphere to obtain a Ru / Eu2O3-loaded nitrogen-doped porous carbon nanofiber composite. The catalyst has a regular morphology, with Ru and Eu2O3 uniformly sized and loaded in the porous carbon nanomaterial. The synergistic effect between Ru clusters and Eu2O3 not only helps stabilize the Ru nanoclusters but also optimizes Ru's binding strength with H and OH by adjusting Ru's electronic structure, thereby promoting the adsorption and desorption of reaction intermediates and ultimately enhancing HOR catalytic activity.

Description

Technical Field

[0001] The invention belongs to the application field of alkaline hydrogen oxidation reaction and relates to a rare earth metal oxide coupled ruthenium-based catalyst and a preparation method and application thereof. Background Art

[0002] At present, anion exchange membrane fuel cells (AEMFC) with high energy conversion efficiency are considered to be the next generation of hydrogen economy devices. Similarly, due to its high theoretical energy density, AEMFC can solve the endurance anxiety problem at one time. However, even if platinum is used at the anode electrode, the reaction kinetics are significantly slowed down, which seriously affects the application of AEMFC. More importantly, the high hydrogen oxidation reaction (HOR) kinetics under alkaline electrolytes are two to three orders of magnitude slower than the reaction in acidic media. Therefore, the discovery and design of high-performance, low-cost HOR catalysts with HOR activity in alkaline electrolytes is a prerequisite for the successful commercialization of AEMFC technology. Among them, studies have proposed that adsorbed hydrogen (H ad ) and adsorbed hydroxyl groups (OH ad ) play an important role in the alkaline HOR mechanism, and hydrogen binding energy (HBE) and hydroxyl binding energy (OHBE) are regarded as characteristic descriptors for analyzing HOR activity.

[0003] Currently, ruthenium-based materials are considered state-of-the-art electrocatalysts for HOR under alkaline conditions, offering performance comparable to that of Pt while being more cost-effective. However, the high OH and H bond strengths of Ru not only limit the HOR performance but also occupy its active sites, thereby reducing the availability of H and OH adsorption sites. Therefore, effective modulation strategies to achieve high-performance HOR by modifying the electronic structure of Ru are highly desirable to achieve moderate HBE and OHBE. Since the electronic structure of 3d / 4d transition metals can be modulated by other d / p / f metals or nonmetallic dopants, electronic modulation is an important strategy to tune the HOR activity of Ru, generating spin-orbit coupling to activate the activity and stability of the metal active sites. For example, Li et al. reported Ru-doped 3d-TMs (V, Fe, Co, and Ni) as electrocatalysts. By introducing a series of 3d transition metals, the CBM values ​​were rationally tuned via dd-orbital coupling, resulting in enhanced alkaline HOR performance. Furthermore, Wu et al. reported unconventional dp hybridization to modify the electronic structure of Ru, which can enhance interfacial water adsorption and optimize the hydrogen adsorption free energy during alkaline HOR. Compared with d / p orbitals, electrons in f orbitals are usually difficult to form covalent bonds directly, but since 4f states have sufficient electron transfer flexibility, they are more likely to donate electrons and provide more electrons to solidify covalent bonds. For 4f energy levels, rare metal (RE) elements typically benefit from the unique valence 4f n-15 d 1 6s 2 or 4fn 6s 2 The electron configuration and the screening effect of 5s and 5p electrons. Considering the strong spin-orbit coupling effect and the relative Fermi energy (E f ) suitable 4f band position, introduce rare earth elements with 4f valence orbitals, and optimize the electron distribution of TM electrocatalytic active centers. At the same time, the construction of RE-O-TM skeleton induced by RE may be conducive to the conservation of TM-O covalency. At the same time, the higher RE-4f state provides the electrons required for its catalytic process. For example, europium (Eu) has a unique 4f 7 6s 2 Valence electron configuration. Eu 3+ (4f 6 ) and Eu 2+ (4f 7 ) can provide a large number of mobile electron transfer sites for various reactions. However, the detailed mechanism of 4f-induced HOR performance and the detailed influence of dpf interactions on HOR activity due to complex valence-orbital coupling remain unclear and warrant further clarification. In-depth research in this area will have the potential to significantly improve the mass activity and cycling stability of HOR catalysts, and is also a worthwhile strategy for increasing the power density of HOR catalysts in applications as anode materials for anion exchange membrane fuel cells. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a rare earth metal oxide-coupled ruthenium-based catalyst, its preparation method, and application. The invention relates to a preparation technique for Ru / Eu2O3 loaded on nitrogen-doped carbon nanofibers to enhance hydrogen oxidation performance, thereby enabling the catalyst to be used as a highly efficient electrocatalyst for fuel cell anodes. The method is simple, versatile, and low-cost, and the resulting nitrogen-doped porous carbon nanofiber composite material exhibits excellent activity and stability as a hydrogen oxidation electrocatalyst material, and exhibits good power density as the anode of anion exchange membrane fuel cells.

[0005] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0006] A method for preparing a rare earth metal oxide-coupled ruthenium-based catalyst comprises the following steps:

[0007] S1. Preparation of Ru 3+ / Eu 3+ / polyacrylonitrile composite nanofibers

[0008] EuCl3·6H2O, Ru(C5H7O2)3 and polyacrylonitrile were added to N,N-dimethylformamide and stirred at room temperature for 12 hours. The solution was then transferred to a syringe and an electrospinning machine was used to collect the spun fibers using aluminum foil as a collector. Ru was collected.3+ / Eu 3+ / polyacrylonitrile composite nanofibers;

[0009] S2. Preparation of Ru 3+ / Eu2O3 nanofibers

[0010] Ru 3+ / Eu 3+ / polyacrylonitrile composite nanofibers were placed in a muffle furnace for pre-oxidation to obtain Ru 3+ / Eu2O3 nanofibers;

[0011] S3. Will Ru 3+ / Eu2O3 nanofibers were carbon-thermally treated under an inert atmosphere to obtain nitrogen-doped porous Ru / Eu2O3@N-CNFs.

[0012] Preferably, the mass of EuCl3·6H2O is 25-200 mg, the mass of Ru(C5H7O2)3 is 10-80 mg, the mass of polyacrylonitrile is 0.5-4 g, and the volume of N,N-dimethylformamide is 5-40 mL.

[0013] Preferably, the pre-oxidation is carried out by heating the temperature to 100-300° C. at a heating rate of 1-4° C. / min and keeping the temperature for 1-4 hours.

[0014] Preferably, the electrospinning machine uses aluminum foil as a collector to collect the spun fibers, and the parameter setting is: the flow rate is 0.04-0.12 mm min -1 , the applied voltage is 10 to 25 kV, and the distance from the nozzle tip to the receiving plate is 8 to 20 cm.

[0015] Preferably, the inert atmosphere in step S3 is a nitrogen atmosphere.

[0016] Preferably, in step S3, the carbon heat treatment is performed by heating the temperature to 500-1000° C. at a heating rate of 1-15° C. / min and keeping the temperature for 1-5 hours.

[0017] A rare earth metal oxide coupled ruthenium-based catalyst Ru / Eu2O3@N-CNFs catalyst prepared by any of the preparation methods described above.

[0018] The rare earth metal oxide coupled ruthenium-based catalyst Ru / Eu2O3@N-CNFs catalyst mainly presents an interwoven long nanofiber structure, in which Ru nanoclusters and Eu2O3 are uniformly embedded in the nanofibers, among which the Ru clusters serve as central active sites, and the surrounding Eu2O3 has a regulatory effect on the local electrons of the active center.

[0019] The application of the rare earth metal oxide coupled ruthenium-based catalyst prepared by the above preparation method in alkaline hydrogen oxidation reaction.

[0020] The reaction principle of the present invention is:

[0021] Using europium chloride and ruthenium acetylacetonate as metal sources and polyacrylonitrile as a carbon and nitrogen source, a Ru / Eu2O3 hybrid nanofiber material is pre-prepared via electrospinning. After pre-oxidation, it is then carbothermally reduced in a high-temperature inert atmosphere to yield a Ru / Eu2O3-loaded nitrogen-doped porous carbon nanofiber composite. This material exhibits a regular and uniform morphology, with Ru nanoclusters and Eu2O3 uniformly embedded within the carbon nanofibers. Furthermore, the carbon nanofibers are rich in nitrogen. Due to the compositional and structural advantages between the carbon nanofibers and the active Ru / Eu2O3, the resulting material exhibits high hydrogen oxidation activity and resistance to CO poisoning under alkaline conditions. The catalyst of the present invention has a porous carbon nanofiber structure, which gives the catalyst material a large specific surface area and increases the exposure rate of active sites. At the same time, the microporous structure of the carbon-based material can effectively promote the effective adsorption of reaction intermediates and catalyst active sites, which is beneficial to the occurrence of the reaction. By confining and evenly distributing rare earth metal oxide Eu2O3 and ruthenium clusters in the carbon nanofibers, the metal active sites in the catalytic process can be stabilized and prevented from falling off or agglomerating, thereby ensuring catalytic stability. By rationally modifying the Ru-based catalyst with rare earth metal oxide, Eu2O3 plays an important role in regulating the electronic structure and optimizing the adsorption / desorption energy of reaction intermediates, optimizing the HBE and OHBE in the reaction process, and significantly improving the overall HOR activity of the catalyst.

[0022] Beneficial effects:

[0023] Compared with the prior art, the rare earth metal oxide-coupled ruthenium-based catalyst of the present invention and its preparation method and application have the following advantages:

[0024] 1) A simple electrospinning-carbothermal method was used to prepare Ru / Eu2O3 nanofiber electrocatalysts with excellent electrochemical activity, high stability, and good resistance to CO poisoning;

[0025] 2) The polyacrylonitrile used is cheap and readily available, and the ruthenium-based metal is used instead of the traditional platinum-based metal. This method is simple and easy to implement, low in cost, simple to operate, and can be produced on a large scale;

[0026] 3) The rare earth metal oxide-coupled ruthenium-based catalyst Ru / Eu2O3@N-CNFs of the present invention has a regular morphology, and Ru and Eu2O3 are uniformly loaded in the porous carbon nanomaterial. The synergistic effect between Ru clusters and Eu2O3 not only helps stabilize the Ru nanoclusters, but also optimizes its binding strength with H and OH by adjusting Ru's electronic structure, thereby promoting the adsorption and desorption of reaction intermediates, ultimately achieving an improvement in HOR catalytic activity. As a result, the prepared material has the characteristics of large specific area, abundant active sites, high intrinsic activity, excellent stability, and good anti-poisoning properties. Compared with conventional Ru-based materials, the prepared Ru / Eu2O3 porous carbon nanofiber composite material has more excellent structural characteristics and component advantages. It is a highly promising hydrogen oxidation electrocatalyst material, showing good power density in anion exchange membrane fuel cells, and is expected to have broad application prospects in the future energy industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an SEM image of a rare earth metal oxide-coupled ruthenium-based catalyst prepared in Example 1;

[0028] Figure 2 TEM spectrum of a rare earth metal oxide-coupled ruthenium-based catalyst prepared in Example 1;

[0029] Figure 3 The XRD pattern of a rare earth metal oxide-coupled ruthenium-based catalyst prepared in Example 1;

[0030] Figure 4 The Tafel curve of a rare earth metal oxide coupled ruthenium-based catalyst prepared in Example 1;

[0031] Figure 5 Comparison of LSV curves of the materials obtained in Example 1 and Comparative Examples 1-2 of the present invention;

[0032] Figure 6 The following is a comparison of the CO toxicity resistance test curves of the materials obtained in Example 1 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing a rare earth metal oxide-coupled ruthenium-based catalyst comprises the following steps:

[0036] 1) Preparation of Ru 3+ / Eu 3+ Polyacrylonitrile / polyacrylonitrile composite nanofiber materials: Dissolve 1g polyacrylonitrile (PAN), 50mg EuCl3·6H2O, and 20mg (C5H7O2)3Ru in 12mL of DMF, stir for 12h, and transfer to a 10mL syringe. Use an electrospinning machine and aluminum foil as a collector to collect the spun fibers. Parameter settings: flow rate 0.06mm min -1 , the applied voltage was 20 kV, and the distance from the nozzle tip to the receiving plate was 15 cm.

[0037] 2) Preparation of Ru / Eu2O3 loaded nitrogen-doped porous carbon nanofiber material: The Ru prepared in step 1) 3+ / Eu 3+ / polyacrylonitrile composite nanofibers were placed in a muffle furnace and pre-oxidized at 150°C for 2 hours at a heating rate of 2°C / min. Then they were placed in a tubular furnace and carbon-thermally treated at 800°C in a N2 atmosphere at a heating rate of 5°C / min. The temperature was maintained for 3 hours and then cooled to room temperature to obtain the final product, Ru / Eu2O3@N-CNFs.

[0038] The rare earth metal doped ruthenium-based catalyst Ru / Eu2O3@N-CNFs prepared in Example 1 was physically characterized by SEM, TEM, XRD and other methods. Figure 1 ), it can be seen that the material is composed of interwoven nanofibers with a diameter of 200 to 500 nm. TEM spectrum ( Figure 2 ) shows that Ru nanoclusters and Eu2O3 are embedded in the carbon nanofibers, and the structure is consistent with the results of SEM. Figure 3 It can be seen from the XRD spectrum that the diffraction peak of the material is completely consistent with the standard card of Eu2O3 (JCPDS card, 32-0380), which proves the successful preparation of Eu2O3. The lack of obvious Ru-related diffraction peaks is due to the extremely small amount of ruthenium doping. At the same time, the (002) crystal plane corresponds to the diffraction peak of graphitized carbon.

[0039] It can be seen from the figure that the Tafel curve ( Figure 4 ) shows that the Tafel slope of the material indicates that it has a faster reaction kinetic rate, which is better than most alkaline hydrogen oxidation electrocatalyst materials.

[0040] The above results all indicate that this material has good application prospects as an alkaline hydrogen oxidation electrocatalyst material.

[0041] Example 2

[0042] Except that the amount of EuCl3·6H2O in step 1 is changed to 100 mg, the rest is the same as in Example 1.

[0043] Example 3

[0044] Except that the amount of (C5H7O2)3Ru in step 1 is changed to 50 mg, the rest is the same as in Example 1.

[0045] Example 4

[0046] Except that the amount of polyacrylonitrile (PAN) in step 1 is changed to 0.5 g, the rest is the same as in Example 1.

[0047] Example 5

[0048] Except that the amount of DMF in step 1 was changed to 5 mL, the rest was the same as in Example 1.

[0049] Example 6

[0050] Except that the amount of DMF in step 1 was changed to 15 mL, the rest was the same as in Example 1.

[0051] Example 7

[0052] Except that the flow rate in step 1 was changed to 0.08 mm / min -1 Other than that, the same as in Example 1.

[0053] Example 8

[0054] Except that the applied voltage in step 1 is changed to 18 kV, the rest is the same as in Example 1.

[0055] Example 9

[0056] Except that the distance from the nozzle tip to the receiving plate in step 1 is changed to 10 cm, the rest is the same as in Example 1.

[0057] Example 10

[0058] Except that the heating rate of the pre-oxidation in step 2 is changed to 3° C. / min, the rest is the same as in Example 1.

[0059] Example 11

[0060] Except that the pre-oxidation temperature in step 2 is changed to 200° C., the rest is the same as in Example 1.

[0061] Example 12

[0062] Except that the pre-oxidation time in step 2 is changed to 3 h, the rest is the same as in Example 1.

[0063] Example 13

[0064] Except that the heating rate of the carbon heat treatment in step 2 is changed to 10° C. / min, the rest is the same as in Example 1.

[0065] Example 14

[0066] Except that the carbon heat treatment speed in step 2 is changed to 900° C., the rest is the same as in Example 1.

[0067] Example 15

[0068] Except that the duration of the carbon heat treatment in step 2 is changed to 4 hours, the rest is the same as in Example 1.

[0069] Comparative Example 1

[0070] The only difference from Example 1 is that only a single metal salt (C5H7O2)3Ru is used, and the other implementation conditions remain unchanged.

[0071] Comparative Example 2

[0072] The only difference from Example 1 is that only a single metal salt EuCl3·6H2O is used, and the other implementation conditions remain unchanged.

[0073] The materials from Example 1 and Comparative Examples 1-2 were tested for alkaline hydrogen oxidation reaction. Electrochemical measurements were performed using a CHI660E workstation in a 0.1 M KOH solution using a three-electrode system, with a graphite rod and a mercury / mercuric oxide electrode serving as the counter and reference electrodes, respectively. A catalyst ink was prepared by mixing 5 mg of the catalyst with 100 μl of Nafion (5 wt.%), followed by the addition of 300 μl of deionized water and 600 μl of ethanol. After ultrasonic treatment for 30 minutes, 10 μl of the catalyst ink was evenly dripped onto a 0.196 cm 2 The working electrode was a glassy carbon electrode dried at room temperature. The scan rate was 5 mV s in a H2 saturated electrolyte. -1 , the scanning rate is 0.02~1.02V or 0.1~0.5V (vs.RHE), the scanning rate is 1600rpm, and the LSV curve is obtained on RDE. The LSV test results are as follows Figure 5 As shown in Figure 2, the kinetic current density of Ru / Eu2O3@N-CNFs at an overpotential of 50 mV is 318.1 mA cm -2 , showing its superior current density. The electrocatalytic materials prepared by single metal Ru and Eu2O3 showed poorer hydrogen oxidation performance than the Ru / Eu2O3 composite material. The overall performance comparison showed the order of Ru / Eu2O3>Ru>Eu2O3.

[0074] CO stripping voltammetry was performed in 0.1 M KOH solution. Before the test, pure N2 was introduced into the electrolyte to remove air from the electrolyte. Then, the electrode was kept at 0.1 V vs. RHE under bubbling CO gas for 15 min. The electrolyte was then purged with N2 for 30 min to completely remove CO from the solution, leaving only a layer of CO on the surface of the working electrode. -1 Under the condition of 0V to 1.0V (vs.RHE), the stripping voltammetry of CO was recorded to obtain the anti-CO toxicity test curve. The test results are as follows: Figure 6 As shown in the figure, Ru / Eu2O3@N-CNFs exhibits a CO oxidation peak at a lower potential, indicating that CO adsorbed on the catalyst surface is more easily oxidized and desorbed, further enhancing the catalyst's CO tolerance, thus demonstrating the unique anti-CO poisoning advantage of Ru / Eu2O3@N-CNFs.

[0075] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a rare earth metal oxide coupled ruthenium-based catalyst, characterized in that: The following steps are involved: S1. Preparation of Ru 3+ / Eu 3+ / polyacrylonitrile composite nanofibers EuCl3·6H2O, Ru(C5H7O2)3 and polyacrylonitrile were added to N,N-dimethylformamide and stirred at room temperature for 12 h. The solution was then transferred to a syringe and the spun fibers were collected using an electrospinning machine and aluminum foil as a collector. Ru 3+ / Eu 3+ / polyacrylonitrile composite nanofibers; S2. Preparation of Ru 3+ / Eu2O3 nanofibers; Will Ru 3+ / Eu 3+ / polyacrylonitrile composite nanofibers were placed in a muffle furnace for pre-oxidation to obtain Ru 3+ / Eu2O3 nanofibers; S3. Will Ru 3+ / Eu2O3 nanofibers were carbon-thermally treated under an inert atmosphere to obtain nitrogen-doped porous Ru / Eu2O3@N-CNFs.

2. The method for preparing a rare earth metal oxide coupled ruthenium-based catalyst according to claim 1, characterized in that: The mass of EuCl3·6H2O is 25-200 mg, the mass of Ru(C5H7O2)3 is 10-80 mg, the mass of polyacrylonitrile is 0.5-4 g, and the volume of N,N-dimethylformamide is 5-40 mL.

3. The method for preparing a rare earth metal oxide coupled ruthenium-based catalyst according to claim 1, characterized in that: The pre-oxidation is carried out by heating the temperature to 100-300°C at a heating rate of 1-4°C / min and keeping the temperature for 1-4 hours.

4. The method for preparing a rare earth metal oxide coupled ruthenium-based catalyst according to claim 1, characterized in that: The electrospinning machine uses aluminum foil as a collector to collect the spun fibers. The parameter setting is: flow rate is 0.04~0.12 mm / min -1 , the applied voltage is 10~25 kV, and the distance from the nozzle tip to the receiving plate is 8~20 cm.

5. The method for preparing a rare earth metal oxide coupled ruthenium-based catalyst according to claim 1, characterized in that: The inert atmosphere in step S3 is a nitrogen atmosphere.

6. The method for preparing a rare earth metal oxide coupled ruthenium-based catalyst according to claim 1, characterized in that: In step S3, the carbon heat treatment is performed by heating the temperature to 500-1000°C at a heating rate of 1-15°C / min and keeping the temperature for 1-5 hours.

7. A rare earth metal oxide-coupled ruthenium-based catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The rare earth metal oxide coupled ruthenium-based catalyst according to claim 7, characterized in that The rare earth metal oxide-coupled ruthenium-based catalyst consists of Ru and Eu2O3, as well as a three-dimensional fiber skeleton structure composed of nanofibers. The average diameter of the nanofibers is 400±100 nm. Ru nanoclusters and Eu2O3 are uniformly embedded in the nanofibers. The three-dimensional fiber skeleton structure increases the number of exposed active sites. By doping with nitrogen heteroatoms, the charge distribution of the carbon fiber matrix is ​​controlled, thereby improving the catalytic activity of the carbon fiber. The porous nanofibers have a large specific surface area, high conductivity and excellent structural stability.

9. Use of a rare earth metal oxide coupled ruthenium-based catalyst prepared by the preparation method of claim 1 in an alkaline hydrogen oxidation reaction.

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