Palladium-based metal alkene material regulated and controlled by double rare earth sites as well as preparation method and application of palladium-based metal alkene material

Abstract

The invention discloses a palladium-based metal alkene material regulated and controlled by double rare earth sites as well as a preparation method and application of the palladium-based metal alkene material. The preparation method mainly comprises the following steps: S1, preparing a potassium chloropalladite solution and a rare earth chloride solution; and S2, completely dissolving the potassium chloropalladite solution and the rare earth chloride solution in a KOH solution of DMF and EG, then adding EDTA, finally filling the obtained mixed solution into a stainless steel high-pressure reaction kettle with a Teflon lining, and then carrying out a hydrothermal reaction. And after cooling to room temperature, centrifugally washing, drying and collecting to obtain the double-rare earth site regulation and control palladium-based metal alkene material. The raw materials selected by the method are cheap and easy to obtain, and the prepared material shows relatively high power density when being used as the positive electrode of the anion exchange membrane fuel cell. The method is simple and feasible in process, low in cost, simple to operate and capable of realizing large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of anion exchange membrane fuel cells, and particularly relates to a palladium-based metallene material with dual rare earth site regulation, a preparation method thereof, and an application thereof. Background Art

[0002] With the gradual depletion of fossil energy, as well as the emergence of problems such as global carbon emission over-standard, global warming, and environmental deterioration. There is an urgent need for a new sustainable energy system. Hydrogen energy is an ideal choice for large-scale and long-term energy storage because of its high energy density, clean products, rich sources, green and low-carbon, wide applications, and being conducive to long-term storage and long-distance transportation. Fuel cells are important terminals for hydrogen energy conversion. As a type of hydrogen-oxygen fuel cell, anion exchange membrane fuel cells (AEMFCs) use hydrogen and oxygen as raw materials and directly convert chemical energy into electrical energy through electrochemical reactions, breaking through the limitation of the Carnot cycle, greatly improving the energy utilization efficiency, and having high economic efficiency. At the same time, it has attracted wide attention due to its environmental friendliness, low battery noise, low operating temperature, fast electrode reaction rate, especially the relatively fast oxygen reduction reaction kinetics in an alkaline environment. As an important half-reaction in AEMFCs, the slow kinetics of the cathode oxygen reduction reaction seriously affects the performance of AEMFCs and restricts its development. Therefore, it is urgent to use a platinum-based catalyst with higher activity. However, the natural reserves of platinum are very limited. Therefore, seeking efficient and stable non-platinum oxygen reduction electrocatalysts for application in the field of anion exchange membrane fuel cells has great theoretical and practical significance.

[0003] In recent years, a two-dimensional ultrathin metal nanosheet material with a high specific surface area, abundant defect sites, and excellent electrical conductivity has been defined as metallene because of its similar morphology and properties to graphene. The thickness of the two-dimensional metallene material is usually subatomic layers. The metallene material can also expose a large number of unsaturated metal sites, and as a result of its easy chemical modification, it provides opportunities for electrochemical catalyst engineering. Compared with platinum with a relatively low content in nature, palladium (Pd) has a relatively large content in nature. Therefore, Pd-based catalysts have significant price advantages. In addition, Pd-based catalysts exhibit good anti-toxicity, and their catalytic activity and selectivity are close to those of Pt-based catalysts. Therefore, they are regarded as potential substitutes for Pt. Although the preparation of pure palladium metallene has extremely excellent oxygen reduction electrocatalytic performance, its cost is very expensive. Doping heteroelements can not only reduce the amount of palladium used, but also greatly improve the performance of the catalytic material. Rare earth elements have characteristics such as unfilled 4f orbitals and lanthanide contraction. When used as active components of catalysts, they exhibit unique properties. Therefore, the palladium-based metallene material with dual rare earth site regulation is a feasible strategy. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the object of the present invention is to provide a palladium-based metalene material with dual rare-earth site regulation, its preparation method and application. The method of the present invention is simple, general and low-cost. Moreover, the prepared palladium-based metalene material with dual rare-earth site regulation, especially the PdLaCe metalene material, exhibits excellent catalytic activity and stability as an oxygen reduction electrocatalytic material, and shows good power density as the positive electrode of an anion exchange membrane fuel cell.

[0005] To solve the problems of the prior art, the technical solution adopted by the present invention is as follows:

[0006] A preparation method of a palladium-based metalene material with dual rare-earth site regulation, comprising the following steps:

[0007] S1. Prepare a potassium chloropalladite solution and a rare-earth chloride solution, wherein the rare-earth chloride is a mixture of any two of cerium chloride, lanthanum chloride, praseodymium chloride, neodymium chloride or europium chloride;

[0008] S2. Drop the potassium chloropalladite solution and the rare-earth chloride solution into a KOH solution containing DMF and EG. After complete dissolution, transfer the yellow mixed solution into a stainless-steel autoclave with a Teflon liner for hydrothermal reaction. After the reaction is completed, cool to room temperature, centrifuge, wash and dry to obtain a palladium-based metalene material with dual rare-earth site regulation.

[0009] As an improvement, the rare-earth chloride is cerium chloride and lanthanum chloride.

[0010] Further improvement is that the potassium chloropalladite solution, cerium chloride solution and lanthanum chloride solution are respectively prepared by adding potassium chloropalladite, cerium chloride and lanthanum chloride solids into N,N-dimethylformamide (DMF) and ultrasonically treating to obtain a 0.05 - 0.2 M potassium chloropalladite solution, a 0.05 - 0.2 M cerium chloride solution and a 0.05 - 0.2 M lanthanum chloride solution.

[0011] Further improvement is that in step S2, the volumes of the potassium chloropalladite solution and the lanthanum chloride solution are 0.1 - 0.4 ml; the mass of KOH in the KOH solution containing DMF and EG is 1 - 2 g, and the volumes of the DMF and EG solutions are 6 - 13 ml.

[0012] As an improvement, in step S2, the temperature of the hydrothermal reaction is 150 - 300 °C, and the reaction time is 8 - 12 h.

[0013] Further improvement is that in step S2, the temperature of the hydrothermal reaction is 180 - 220 °C.

[0014] As an improvement, in step S2, the reagent for centrifugal washing is ethanol, and it is washed 2 - 3 times and dried at room temperature.

[0015] The dual-rare-earth-site-regulated palladium-based metalene material prepared by the preparation method described in any one of the above, which is a two-dimensional sheet-like structure ternary alloy component composed of different rare-earth metals and metal Pd, is in the shape of a curved ultra-thin sheet, has a large specific surface area and excellent electrical conductivity, and has rich defect, void and dislocation structures in the two-dimensional sheet structure.

[0016] Application of the above dual-rare-earth-site-regulated palladium-based metalene material as a catalyst for the alkaline oxygen reduction reaction.

[0017] As an improvement, the alkaline oxygen reduction reaction is specifically used as the positive electrode of an anion exchange membrane fuel cell.

[0018] In the present invention, potassium chloropalladate, cerium chloride, and lanthanum chloride are used as metal sources. In this process, KOH can promote the in-situ generation of dimethylamine (DMA) through the decomposition of DMF, and the generated DMA can promote the growth of the two-dimensional nanosheet structure through metal crystal plane control. The introduction of DETA can weaken the reduction rate of the metal by chelating metal ions, which is beneficial to the formation of the two-dimensional nanosheet structure. The morphology of this material is in the shape of a curved ultra-thin sheet, which can expose more ORR active sites. In addition, the incorporation of lanthanide rare-earth metals La and Ce improves the d-band center of Pd, making it close to the Fermi level, enhancing the intrinsic catalytic activity of metal Pd, thereby promoting oxygen activation and optimizing the oxygen adsorption energy. The obtained material has excellent stability under alkaline conditions. The two-dimensional ultra-thin metalene material is a PdLaCe metalene material composed of three different metals Pd, La, and Ce.

[0019] Beneficial effects:

[0020] Compared with the prior art, the present invention provides a dual-rare-earth-site-regulated palladium-based metalene material, its preparation method and application. The doping of rare-earth metals can adjust the orbit, charge, spin, coordination number and lattice matching degree of freedom of the catalytic material, thereby improving the intrinsic activity of the palladium-based metalene material. Due to the synergistic effect between these elements, the surface electronic structure of palladium can be adjusted. In addition, the regulation of dual-rare-earth sites greatly improves the activity and durability of the catalyst, and significantly enhances the lifespan and applicability of the material. It provides a new strategy for designing new metalene catalytic materials to promote the oxygen reduction reaction and as the positive electrode material of anion exchange membrane fuel cells. Different from the palladium alloy metalene doped with transition metals, the formed structure is a PdLaCe alloy structure rich in Pd on the outer layer. The advantages are as follows:

[0021] 1) Through a simple and easy-to-operate one-step hydrothermal method, a dual-rare-earth-site-regulated palladium-based metalene material can be obtained;

[0022] 2) The present invention preferably uses lanthanum and cerium chlorides for regulation. The prepared Pd metallene material with dual rare-earth site regulation is a highly curved, sub-nanometer-thick nanosheet, which has more active sites, a higher half-wave potential, and very good stability. Compared with conventional Pd-based metal materials, the prepared PdLaCe metallene material not only has structural advantages, but also greatly reduces the content of Pd. It is a very promising oxygen reduction electrocatalyst material, showing good power density and stability in anion exchange membrane fuel cells, and is expected to have broad application prospects in the future hydrogen energy industry. Description of the Drawings

[0023] Figure 1 SEM pattern of the Pd metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1;

[0024] Figure 2 TEM pattern of the Pd metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1;

[0025] Figure 3 HR-TEM pattern of the Pd metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1;

[0026] Figure 4 XRD pattern of the Pd metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1;

[0027] Figure 5 LSV curve of the Pd metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1;

[0028] Figure 6 Tafel curve of the Pd metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1;

[0029] Figure 7 Polarization and corresponding power density curves of the Pd-based metallene material with lanthanum-cerium dual rare-earth site regulation prepared in Example 1. Detailed Description of the Invention

[0030] 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 do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0031] Example 1

[0032] A preparation method of a Pd-based metallene material with lanthanum-cerium dual rare-earth site regulation, comprising the following steps:

[0033] 1) Preparation of potassium chloropalladate solution, cerium chloride solution and lanthanum chloride solution: Weigh 163.2 mg of K2PdCl4, 186.29 mg of CeCl3, and 185.68 mg of LaCl3, and disperse them separately in 5 ml of DMF. Ultrasonic them in ice water until completely dissolved to obtain 0.1 M potassium chloropalladate solution, 0.1 M cerium chloride solution and 0.1 M lanthanum chloride solution.

[0034] 2) Preparation of KOH solution dissolved in DMF and EG: Weigh 2.0 g of KOH, disperse it in 11.4 ml of DMF and 8 ml of EG, and ultrasonic for 30 min until completely dissolved.

[0035] 3) Preparation of PdLaCe metalene material: Pipette 0.6 ml of the K2PdCl4 solution, 0.2 ml of the CeCl3 solution and 0.2 ml of the LaCl3 solution prepared in step 1), and drop them into the KOH solution dissolved in DMF and EG prepared in step 2). Then add 10 ml of DETA, mix evenly and pour it into a 50 ml stainless steel autoclave with a Teflon lining. React at 200 °C for 10 h. After natural cooling to room temperature, centrifuge and wash with absolute ethanol 2 - 3 times, and dry at room temperature to obtain the PdLaCe metalene material.

[0036] The PdLaCe metalene material prepared in the above examples was physically characterized by means of SEM, HR-TEM, XRD, etc. From the SEM ( Figure 1 ) and TEM ( Figure 2 ), it can be seen the morphology of the curved two-dimensional ultrathin nanosheets of the material, indicating that the two-dimensional ultrathin sheet structure constructed by the hydrothermal reaction of the material is successfully formed. The HR-TEM pattern ( Figure 3 ) shows the lattice spacing and clear lattice fringes of the PdLaCe metalene material. The lattice fringe spacing of PdLaCe metalene is measured to be 0.225 nm, which corresponds to the Pd(111) crystal plane of the face-centered cubic structure. From the Figure 4 XRD pattern, it can be seen that it matches well with the phase card of metallic palladium (JCPDS card, no. 46 - 1043) with a weak negative shift, proving the successful preparation of the PdLaCe metalene material. Figure 5 This is the LSV graph obtained by testing the oxygen reduction performance of the material. It can be seen from the graph that the initial reduction potential and the half-wave potential are 1.01 V and 0.903 V respectively. The Tafel curve ( Figure 6 ) shows that the value of the Tafel slope of this material is lower than that of most alkaline oxygen reduction electrocatalyst materials.

[0037] Disperse the PdLaCe metalene material of the present invention in a water / isopropanol mixture and FAA-3 ionomer, sonicate for about 60 minutes to prepare the cathode ink, and spray it onto an anion exchange membrane (the model of the anion exchange membrane (AEM) can be selected as FuMA-Tech, FAA-3-50) as a membrane electrode for testing. At 40 °C, assemble and test it in a fuel cell test station. Specifically, under a hydrogen and air supply with a relative humidity of 80%, a constant flow rate of 100 sccm and 200 sccm, and no back pressure. By pulling the current of the test instrument, the corresponding polarization curve and the corresponding power density curve can be obtained.

[0038] The material of this example was used as the positive electrode material of an anion exchange membrane fuel cell for experiments, and the obtained polarization curve and the corresponding power density curve are as Figure 7 shown.

[0039] From the above test results, it can be seen that the material of the present invention has good application prospects as an alkaline oxygen reduction electrocatalyst material.

[0040] Example 2

[0041] A preparation method of a lanthanum-cerium dual rare earth site-regulated palladium-based metalene material, comprising the following steps:

[0042] Except for the change in step 1), the rest is the same as in Example 1.

[0043] Among them, in step 1), prepare potassium chloropalladite solution, cerium chloride solution and lanthanum chloride solution: weigh 163.2 mg of K2PdCl4, 186.29 mg of CeCl3, and 185.68 mg of LaCl3, disperse them in 2.5 ml of DMF respectively, and sonicate in ice water until completely dissolved to obtain a 0.2 M potassium chloropalladite solution, a 0.2 M cerium chloride solution and a 0.2 M lanthanum chloride solution.

[0044] Example 3

[0045] A preparation method of a lanthanum-cerium dual rare earth site-regulated palladium-based metalene material, comprising the following steps:

[0046] Except for the change in step 1), the rest is the same as in Example 1.

[0047] Among them, in step 1), prepare potassium chloropalladite solution, cerium chloride solution and lanthanum chloride solution: weigh 163.2 mg of K2PdCl4, 186.29 mg of CeCl3, and 185.68 mg of LaCl3, disperse them in 10 ml of DMF respectively, and sonicate in ice water until completely dissolved to obtain a 0.05 M potassium chloropalladite solution, a 0.05 M cerium chloride solution and a 0.05 M lanthanum chloride solution.

[0048] Example 4

[0049] A preparation method of a palladium-based metalene material regulated by lanthanum-cerium dual rare-earth sites, comprising the following steps:

[0050] Except for the change in step 2), the rest is the same as in Example 1.

[0051] Among them, in step 2), prepare a KOH solution dissolved in DMF and EG: Weigh 2.0 g of KOH, disperse it in 5.7 ml of DMF and 4 ml of EG, and ultrasonicate for 30 min until completely dissolved.

[0052] Example 5

[0053] A preparation method of a palladium-based metalene material regulated by lanthanum-cerium dual rare-earth sites, comprising the following steps:

[0054] Except for the change in step 2), the rest is the same as in Example 1.

[0055] Among them, in step 2), prepare a KOH solution dissolved in DMF and EG: Weigh 2.0 g of KOH, disperse it in 11.4 ml of DMF and 4 ml of EG, and ultrasonicate for 30 min until completely dissolved.

[0056] Example 6

[0057] A preparation method of a palladium-based metalene material regulated by lanthanum-cerium dual rare-earth sites, comprising the following steps:

[0058] Except for the change in step 2), the rest is the same as in Example 1.

[0059] Among them, in step 2), prepare a KOH solution dissolved in DMF and EG: Weigh 2.0 g of KOH, disperse it in 5.7 ml of DMF and 8 ml of EG, and ultrasonicate for 30 min until completely dissolved.

[0060] Example 7

[0061] A preparation method of a palladium-based metalene material regulated by lanthanum-cerium dual rare-earth sites, comprising the following steps:

[0062] Except for the change in step 2), the rest is the same as in Example 1.

[0063] Among them, in step 2), prepare a KOH solution dissolved in DMF and EG: Weigh 4.0 g of KOH, disperse it in 5.7 ml of DMF and 4 ml of EG, and ultrasonicate for 30 min until completely dissolved.

[0064] Example 8

[0065] A preparation method of a palladium-based metalene material regulated by lanthanum-cerium dual rare-earth sites, comprising the following steps:

[0066] Except for the change in step 3), the rest is the same as in Example 1.

[0067] Among them, in step 3) for preparing the PdLaCe metalene material: Pipette 0.6 ml of the K2PdCl4 solution, 0.2 ml of the CeCl3 solution, and 0.2 ml of the LaCl3 solution prepared in step 1, and drop them into the KOH solution dissolved in DMF and EG prepared in step 2. Then add 5 ml of DETA, mix evenly and pour it into a 50-ml stainless steel autoclave with a Teflon liner. React at 200 °C for 10 h. After naturally cooling to room temperature, centrifuge and wash with absolute ethanol 2-3 times, and dry at room temperature to obtain the PdLaCe metalene material.

[0068] Example 9

[0069] A preparation method of a palladium-based metalene material with lanthanum and cerium dual rare-earth site regulation, comprising the following steps:

[0070] Except for the change in step 3), the rest is the same as in Example 1.

[0071] Among them, in step 3) for preparing the PdLaCe metalene material: Pipette 0.6 ml of the K2PdCl4 solution, 0.2 ml of the CeCl3 solution, and 0.2 ml of the LaCl3 solution prepared in step 1, and drop them into the KOH solution dissolved in DMF and EG prepared in step 2. Then add 10 ml of DETA, mix evenly and pour it into a 50-ml stainless steel autoclave with a Teflon liner. React at 200 °C for 8 h. After naturally cooling to room temperature, centrifuge and wash with absolute ethanol 2-3 times, and dry at room temperature to obtain the PdLaCe metalene material.

[0072] Example 10

[0073] A preparation method of a palladium-based metalene material with lanthanum and cerium dual rare-earth site regulation, comprising the following steps:

[0074] Except for the change in step 3), the rest is the same as in Example 1.

[0075] Among them, in step 3) for preparing the PdLaCe metalene material: Pipette 0.6 ml of the K2PdCl4 solution, 0.2 ml of the CeCl3 solution, and 0.2 ml of the LaCl3 solution prepared in step 1, and drop them into the KOH solution dissolved in DMF and EG prepared in step 2. Then add 10 ml of DETA, mix evenly and pour it into a 50-ml stainless steel autoclave with a Teflon liner. React at 200 °C for 12 h. After naturally cooling to room temperature, centrifuge and wash with absolute ethanol 2-3 times, and dry at room temperature to obtain the PdLaCe metalene material.

[0076] In summary, the rare earth metal Ce selected in the present invention can well promote the adsorption and activation of molecular oxygen by promoting the generation of highly localized surface electrons during the catalytic process. The rare earth metal La has the ability to resist corrosion and enhance the structural stability. The incorporation of La and Ce into Pd can optimize the electronic structure, regulate the reactivity and durability of the surface Pd sites, thereby promoting oxygen activation, optimizing the oxygen adsorption energy, and exposing more active sites for ORR. DMF plays an important role in the synthesis of two-dimensional nanomaterials. At high temperatures, DMF promotes the in-situ generation of DMA under the action of strong base, and the generated DMA can promote the anisotropic growth of the two-dimensional nanosheet structure through metal surface control. The dual-site regulation of rare earth metals Ce and La reduces the amount of Pd used. At the same time, the addition of Ce and La atoms improves the d-band center of Pd, making it closer to the Fermi level. This change is beneficial to the activation of ORR intermediates. In addition, the PdLaCe metalene material has a unique two-dimensional structure that can inhibit its dissolution and aggregation, showing excellent catalytic stability.

[0077] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A preparation method of a palladium-based metallene material with dual rare-earth site regulation, characterized in that, It includes the following steps: S1. Prepare potassium chloropalladite solution and rare earth chloride solution, wherein the rare earth chloride is a mixture of any two of cerium chloride, lanthanum chloride, praseodymium chloride, neodymium chloride or europium chloride; S2. Drop the potassium chloropalladite solution and rare earth chloride solution into the KOH solution in DMF and EG. After complete dissolution, put the yellow mixed solution into a stainless steel autoclave with a Teflon liner for hydrothermal reaction. After the reaction is completed, cool it to room temperature, centrifuge, wash and dry to obtain a palladium-based metalene material with dual rare earth site regulation.

2. The preparation method of the PdLaCe metalene material according to claim 1, characterized in that, The rare earth chloride is cerium chloride and lanthanum chloride.

3. The preparation method of the PdLaCe metallene material according to claim 2, characterized in that, The potassium chloropalladite solution, cerium chloride solution and lanthanum chloride solution are respectively prepared by adding potassium chloropalladite, cerium chloride and lanthanum chloride solids into N,N-dimethylformamide (DMF) and ultrasonically treating to obtain a 0.05 - 0.2 M potassium chloropalladite solution, a 0.05 - 0.2 M cerium chloride solution and a 0.05 - 0.2 M lanthanum chloride solution.

4. The preparation method of the palladium-based metalene material with dual rare-earth site regulation according to claim 3, characterized in that, In step S2, the volumes of the potassium chloropalladite solution and lanthanum chloride solution are 0.1 - 0.4 ml; the mass of KOH in the KOH solution containing DMF and EG is 1 - 2 g, and the volumes of the DMF and EG solutions are 6 - 13 ml.

5. The preparation method of the palladium-based metalene material with dual rare-earth site regulation according to claim 1, characterized in that, In step S2, the temperature of the hydrothermal reaction is 150 - 300 °C, and the reaction time is 8 - 12 h.

6. The preparation method of the palladium-based metalene material with dual rare earth site regulation according to claim 5, characterized in that, In step S2, the temperature of the hydrothermal reaction is 180 - 220 °C.

7. The preparation method of the palladium-based metalene material with dual rare-earth site regulation according to claim 1, characterized in that, In step S2, the reagent for centrifugal washing is ethanol, and it is washed 2 - 3 times and dried at room temperature.

8. The dual-rare-earth-site-regulated palladium-based metalene material prepared by the preparation method according to any one of claims 1-7, characterized in that: The two-dimensional sheet-like structure ternary alloy component composed of different rare earth metals and metal Pd is in a curved ultra-thin sheet shape, has a large specific surface area and excellent conductivity, and has rich defects, voids and dislocation structures in the two-dimensional sheet structure.

9. Application of the palladium-based metalene material with dual rare earth site regulation according to claim 8 as a catalyst for the alkaline oxygen reduction reaction.

10. The application according to claim 9, wherein The application of the alkaline oxygen reduction reaction is specifically on the positive electrode of an anion exchange membrane fuel cell.

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