A heteronuclear bimetallic fuel cell oxygen reduction catalyst, its preparation method and application

Abstract

This application relates to a heteronuclear bimetallic fuel cell oxygen reduction catalyst, its preparation method, and its application, belonging to the field of catalyst technology. The preparation method of the heteronuclear bimetallic fuel cell oxygen reduction catalyst of this application includes the following steps: S1, dissolving zinc, iron, and other metal sources in an organic solvent, stirring and sonicating to obtain a red mixed solution; S2, dissolving 2-methylimidazole in an organic solvent, stirring until completely dissolved to obtain a transparent mixed solution; S3, slowly adding the transparent mixed solution to the red mixed solution to carry out the reaction, centrifuging and collecting the yellow solid after the reaction is complete, drying and grinding to obtain a precursor powder, and then subjecting the precursor powder to pyrolysis treatment to obtain the heteronuclear bimetallic fuel cell oxygen reduction catalyst. This application selects doping of s- and p-regions with Li, Na, Al, etc., and precisely constructs bimetallic atomic sites to prepare Fe-based bimetallic-nitrogen-carbon catalysts with high intrinsic activity and high stability.

Description

Technical Field

[0001] This application relates to the field of catalyst technology, and in particular to an oxygen reduction catalyst for heteronuclear bimetallic fuel cells, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are considered the most promising renewable energy conversion devices due to their advantages such as low operating temperature, fast start-up, high energy conversion efficiency, and cleanliness. However, their cathode oxygen reduction reaction (ORR) is slow and requires a large amount of platinum-based catalyst. The scarcity and poor durability of this catalyst have seriously hindered the commercial development of PEMFCs. Therefore, non-precious metal ORR catalysts with low cost, high activity, and high stability have been widely explored and applied.

[0003] While atomically dispersed Fe-NC catalysts have made some progress in terms of activity, several challenges remain in practical applications. The well-defined symmetrical electron distribution of the Fe-N4 / C sites hinders the adsorption and activation of O2 at these sites, thus affecting the intrinsic activity of the catalyst in the ORR process. Furthermore, the significant dissolution of metal ions in Fe-NC catalysts leads to a decrease in active site density, causing a sharp decline in catalytic activity. Compared to traditional atomically dispersed Fe-NC catalysts, Fe-based bimetallic-nitrogen-carbon catalysts offer unique advantages. First, they can optimize the adsorption and desorption rates of oxygen-containing intermediates at active sites by modulating the electronic and coordination structures of the Fe-N4 / C sites, further enhancing electrocatalytic activity. Second, the introduction of a second metal atom modulates the Fe-N bond strength, resulting in better thermodynamic stability for the Fe-based bimetallic-nitrogen-carbon catalyst. In the periodic table, metal atoms in different regions (s-block, p-block, d-block, f-block) have different valence electron structures, which will have varying effects on the electron distribution and geometry of the Fe atoms at the active center, thus affecting the ORR activity. For Fe-based bimetallic-nitrogen-carbon catalysts where the second metal is a transition metal, numerous studies have reported that the two metals mutually modulate the charge state of the metal atoms, thereby enhancing ORR activity. For ORR catalysts with main group s-block and p-block metals coupled with Fe atoms, the s / p-block metal atoms (such as Li, Na, Mg, Al, etc.) cannot provide lone pairs of electrons, thus having a smaller impact on the charge state of Fe atoms. This allows for more precise modulation of the d-orbital state of the Fe atom active center, resulting in a more favorable electron distribution and improved catalytic activity. Simultaneously, the stronger orbital interaction between the s / p-block metal atoms and Fe atoms enhances the Fe-N bond strength at the active center, thereby inhibiting metal ion dissolution and improving stability. Currently, the main method for constructing heteronuclear bimetallic catalysts involves dispersing the two metal sources on carbon materials (such as graphene, carbon nanotubes, etc.) or precursors (such as melamine, chitosan, etc.) followed by post-processing. However, in current synthetic methods, due to the random dispersion and combination of the two metals, bimetallic-nitrogen-carbon catalysts may exhibit multiple bimetallic, or even monometallic and polymetallic, configurations. This hinders the acquisition of high-abundance heteronuclear metal atom pairs with defined relative positions and impedes the exploration of the correlation between metal configuration and catalytic activity. Summary of the Invention

[0004] In view of this, this application provides a heteronuclear bimetallic fuel cell oxygen reduction catalyst, its preparation method, and its application. It involves selectively doping the s- and p-regions with Li, Na, Al, etc., and precisely constructing bimetallic atomic sites to prepare a Fe-based bimetallic-nitrogen-carbon catalyst with high intrinsic activity and high stability. The entire synthesis uses a metal-organic framework (MOF) as a support, simultaneously introducing iron and metal sources, and achieving precise doping through the strong adsorption between ions and the MOF. The synthesis method of this application is simple and can be operated in a proportionally quantified manner, providing a stronger basis for preparing high-efficiency heteronuclear bimetallic fuel cell oxygen reduction catalysts with precise bimetallic atomic sites, and effectively overcoming the shortcomings of the existing technologies.

[0005] The first aspect of this application provides a method for preparing an oxygen reduction catalyst for a heteronuclear bimetallic fuel cell, comprising the following steps:

[0006] S1. Dissolve zinc source, iron source and other metal sources in an organic solvent, stir and sonicate to obtain a red mixed solution;

[0007] S2. Dissolve 2-methylimidazole in an organic solvent and stir until completely dissolved to obtain a transparent mixed solution;

[0008] S3. The transparent mixture is slowly added to the red mixture to carry out the reaction. After the reaction is complete, the yellow solid is centrifuged and collected. After drying and grinding, the precursor powder is obtained. The precursor powder is then subjected to pyrolysis to obtain the heteronuclear bimetallic fuel cell oxygen reduction catalyst.

[0009] Specifically, it includes the following steps:

[0010] S1. Dissolve zinc nitrate hexahydrate, anhydrous ferric chloride and metal source in an organic solvent, stir and sonicate to obtain a red mixed solution;

[0011] S2. Dissolve 2-methylimidazole in an organic solvent and stir until completely dissolved to obtain a transparent mixed solution;

[0012] S3. The transparent mixture is slowly added to the red mixture to carry out the reaction. After the reaction is complete, the yellow solid is centrifuged and collected. After drying and grinding, the precursor powder is obtained. The precursor powder is then subjected to pyrolysis to obtain the heteronuclear bimetallic fuel cell oxygen reduction catalyst.

[0013] This application achieves more precise control over the electronic and geometric structure of iron-based catalysts by precisely doping with s / p-block main group metals, thereby balancing catalytic activity and stability and promoting the widespread application of Fe-based bimetallic-nitrogen-carbon catalysts in practice.

[0014] Preferably, in step S1, the other metal source is selected from one of Li source, Na source, and Al source, wherein the Li source is lithium bis(oxalato)borate, the Na source is sodium difluorophosphate, and the Al source is aluminum trifluoromethanesulfonate; or

[0015] The iron source is selected from one of anhydrous ferric chloride, ferric nitrate, and ferric sulfate; or

[0016] The zinc source is selected from one of zinc nitrate hexahydrate, zinc chloride, and zinc sulfate.

[0017] Preferably, in step S3, the specific conditions for pyrolysis are: pyrolysis temperature of 1000℃ and pyrolysis time of 1h.

[0018] Preferably, the ratio of zinc nitrate hexahydrate, anhydrous ferric chloride, metal source and 2-methylimidazole is (0.1-1g):(0.01-0.1g):(0.01-0.1g):(1.0-5.0g).

[0019] Preferably, in steps S1 and S2, the organic solvent is methanol.

[0020] The second aspect of this application also provides a heteronuclear bimetallic fuel cell oxygen reduction catalyst, which is prepared by the above-described method.

[0021] The third aspect of this application also provides the application of the aforementioned heteronuclear bimetallic fuel cell oxygen reduction catalyst in the battery cathode material.

[0022] A fourth aspect of this application also provides a working electrode comprising the above-described heteronuclear bimetallic fuel cell oxygen reduction catalyst.

[0023] The fifth aspect of this application also provides a method for preparing the above-mentioned working electrode, comprising the following steps:

[0024] Weigh 10 mg of the heteronuclear bimetallic fuel cell oxygen reduction catalyst material and add 1 mL of isopropanol. Sonicate the mixture until homogeneous, and then drop it onto the disk electrode to obtain the working electrode.

[0025] Compared with the prior art, this application has the following advantages:

[0026] This application selects Li, Na, Al, etc., doped into the s- and p-regions to prepare Fe-based bimetallic-nitrogen-carbon catalysts with high intrinsic activity and high stability by precisely constructing bimetallic atomic sites. The entire synthesis uses a metal-organic framework (MOF) as a support, simultaneously introducing iron and metal sources, and achieving precise doping through the strong adsorption between ions and the MOF. The synthesis method presented in this application is simple and can be operated in a proportionally quantifiable manner, providing a stronger basis for preparing highly efficient heteronuclear bimetallic fuel cell oxygen reduction catalysts with precise bimetallic atomic sites. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a SEM image of the Fe / Li-NC catalyst of Example 1 of this application;

[0029] Figure 2 This is a SEM image of the Fe / Al-NC catalyst of Example 3 of this application;

[0030] Figure 3 The CV comparison charts show the Fe / Li-NC catalyst, Fe / Na-NC catalyst, Fe / Al-NC catalyst of Examples 1-3 of this application and the Fe-NC catalyst of Comparative Example 1.

[0031] Figure 4 The SCV comparison diagrams are of the Fe / Li-NC catalyst, Fe / Na-NC catalyst, Fe / Al-NC catalyst of Examples 1-3 of this application and the Fe-NC catalyst of Comparative Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.

[0034] In the following examples and comparative examples, unless otherwise specified, all raw materials can be prepared by commercial purchase or conventional methods.

[0035] Example 1

[0036] 0.5 g of zinc nitrate hexahydrate, 0.08 g of anhydrous ferric chloride, and 0.04 g of lithium bis(oxalato)borate (LiBOB) were dissolved in 50 ml of methanol and stirred with sonication to obtain a red mixed solution. 1.5 g of 2-methylimidazole was weighed and dissolved in 50 ml of methanol, stirred until completely dissolved to obtain a transparent mixed solution. The transparent solution was then slowly added to the red mixed solution for reaction. After centrifugation, the yellow solid was collected and dried in a forced-air drying oven. The dried sample was then ground to obtain Fe / Li-NC precursor powder. The Fe / Li-NC precursor powder was pyrolyzed in a tube furnace at 1000 °C for 1 h to obtain the final Fe / Li-NC catalyst for testing.

[0037] Example 2

[0038] Except for the following steps, which are different from those in Example 1, the other preparation and testing methods are exactly the same as in Example 1.

[0039] 0.5 g of zinc nitrate hexahydrate, 0.08 g of anhydrous ferric chloride, and 0.05 g of sodium difluorophosphate (NaDFP) were dissolved in 50 ml of methanol and stirred with sonication to obtain a red mixed solution. 1.5 g of 2-methylimidazole was weighed and dissolved in 50 ml of methanol, stirred until completely dissolved to obtain a transparent mixed solution. The transparent solution was then slowly added to the red mixed solution for reaction. After centrifugation, the yellow solid was collected and dried in a forced-air drying oven. The dried sample was then ground to obtain Fe / Na-NC precursor powder. The Fe / Na-NC precursor powder was pyrolyzed in a tube furnace at 1000 °C for 1 h to obtain the final Fe / Na-NC catalyst for testing.

[0040] Example 3

[0041] Except for the following steps, which are different from those in Example 1, the other preparation and testing methods are exactly the same as in Example 1.

[0042] 0.5 g of zinc nitrate hexahydrate, 0.08 g of anhydrous ferric chloride, and 0.09 g of aluminum trifluoromethanesulfonate (Al(TfO)3) were dissolved in 50 ml of methanol and stirred with sonication to obtain a red mixed solution. 1.5 g of 2-methylimidazole was weighed and dissolved in 50 ml of methanol, stirred until completely dissolved to obtain a transparent mixed solution. The transparent solution was then slowly added to the red mixed solution for reaction. After centrifugation, the yellow solid was collected and dried in a forced-air drying oven. The dried sample was then ground to obtain Fe / Al-NC precursor powder. The Fe / Al-NC precursor powder was pyrolyzed in a tube furnace at 1000 °C for 1 h to obtain the final Fe / Al-NC catalyst for testing.

[0043] Comparative Example 1

[0044] The preparation method provided in this comparative example can be referred to in Example 1, except that no other metal source is introduced to obtain the final Fe-NC catalyst for testing.

[0045] Test case

[0046] Weigh 10 mg of each of the electrocatalyst materials in Examples 1-3 and Comparative Example 1, add 1 mL of isopropanol and sonicate until homogeneous. After homogeneity, drop the mixture onto a disc electrode for oxygen reduction electrochemical performance testing. Figure 1 As can be seen, the Fe / Li-NC catalyst prepared by introducing a second lithium metal source did not change the original octahedral structure of ZIF-8, and the size was not uniform, with no obvious metal nanoparticles generated.

[0047] Figure 2 As can be seen, the Fe / Al-NC catalyst prepared by introducing a second aluminum source did not change the original octahedral structure of ZIF-8. The size was relatively uniform and no obvious metal nanoparticles were generated.

[0048] Figure 3 As can be seen, the heteronuclear bimetallic catalysts prepared by introducing a second different metal source also have different electrochemical activities. By comparing the electrochemical active areas, it can be seen that the Fe / Li-NC catalyst has the best oxygen reduction activity, followed by the Fe / Na-NC catalyst, then the Fe / Al-NC catalyst, and finally the Fe-NC catalyst.

[0049] Figure 4 As can be seen, the heteronuclear bimetallic catalysts prepared by introducing a second, different metal source also exhibit different oxygen reduction properties. In acidic electrolyte tests, the half-wave potential (E) of the Fe / Li-NC catalyst is significantly higher. 1 / 2The voltage can reach 0.82V, while the E values ​​of Fe / Al-NC catalyst, Fe / Na-NC catalyst, and Fe-NC catalyst are lower. 1 / 2 The values ​​are 0.80V, 0.79V, and 0.78V, respectively.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing an oxygen reduction catalyst for a heteronuclear bimetallic fuel cell, characterized in that, Includes the following steps: S1. Dissolve zinc source, iron source and other metal sources in an organic solvent, stir and sonicate to obtain a red mixed solution; S2. Dissolve 2-methylimidazole in an organic solvent and stir until completely dissolved to obtain a transparent mixed solution; S3. Slowly add the transparent mixture to the red mixture to carry out the reaction. After the reaction is complete, centrifuge and collect the yellow solid. Dry and grind the solid to obtain the precursor powder. Perform pyrolysis on the precursor powder to obtain Fe / Li-NC catalyst, Fe / Na-NC catalyst or Fe / Al-NC catalyst. In step S1, the other metal source is selected from one of Li source, Na source, and Al source.

2. The method for preparing the heteronuclear bimetallic fuel cell oxygen reduction catalyst according to claim 1, characterized in that, The Li source is lithium bis(oxalato)borate, the Na source is sodium difluorophosphate, and the Al source is aluminum trifluoromethanesulfonate; the iron source is selected from one of anhydrous ferric chloride, ferric nitrate, and ferric sulfate; and the zinc source is selected from one of zinc nitrate hexahydrate, zinc chloride, and zinc sulfate.

3. The method for preparing the heteronuclear bimetallic fuel cell oxygen reduction catalyst according to claim 1, characterized in that, In step S3, the specific conditions for pyrolysis are: pyrolysis temperature of 1000℃ and pyrolysis time of 1h.

4. The method for preparing the heteronuclear bimetallic fuel cell oxygen reduction catalyst according to claim 2, characterized in that, The ratio of zinc nitrate hexahydrate, anhydrous ferric chloride, metal source and 2-methylimidazole is (0.1-1g):(0.01-0.1g):(0.01-0.1g):(1.0-5.0g).

5. The method for preparing the heteronuclear bimetallic fuel cell oxygen reduction catalyst according to claim 1, characterized in that, In steps S1 and S2, the organic solvent is methanol.

6. A heteronuclear bimetallic fuel cell oxygen reduction catalyst, characterized in that, The heteronuclear bimetallic fuel cell oxygen reduction catalyst prepared by the method according to any one of claims 1-5.

7. The application of the heteronuclear bimetallic fuel cell oxygen reduction catalyst according to claim 6 in the battery cathode material.

8. A working electrode, characterized in that, It includes the heteronuclear bimetallic fuel cell oxygen reduction catalyst as described in claim 6.

9. A method for preparing the working electrode according to claim 8, characterized in that, Includes the following steps: Weigh 10 mg of the heteronuclear bimetallic fuel cell oxygen reduction catalyst material and add 1 mL of isopropanol. Sonicate the mixture until homogeneous, and then drop it onto the disk electrode to obtain the working electrode.

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