Carbon-based high-entropy monatomic catalyst and preparation method thereof

Abstract

The present application relates to the technical field of catalyst, and particularly relates to a carbon-based high-entropy single-atom catalyst and a preparation method thereof.A preparation method of a carbon-based high-entropy single-atom catalyst comprises the following steps: S1: dissolving or dispersing monodisperse SiO2 particles, silicate-based twin monomers and multicomponent metal carboxylate in a solvent; S2: adding methane sulfonic acid as a catalyst, uniformly dispersing, packaging, freezing, vacuumizing, dissolving and then placing in a vacuum oven for reaction, and carrying out twin polymerization limited construction of SiO2@polymer / metal carboxylate / SiO2 core-shell complex on the reactants in step S1; and S3: high-temperature thermal conversion and NaOH solution etching to remove SiO2, so as to obtain the carbon-based high-entropy single-atom catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a carbon-based high-entropy single-atom catalyst and its preparation method. Background Technology

[0002] The oxygen reduction reaction (ORR), a core electrode reaction in fuel cells and zinc-air batteries, suffers from slow kinetics due to the linear relationship between its catalytic efficiency and the adsorption energy of intermediate products. Therefore, it is necessary to design highly active and stable ORR catalysts to overcome the linear scaling relationship and achieve independent optimization and dynamic matching of adsorption energy to enhance reaction activity. Compared to carbon-based single-atom metal catalysts and carbon-based dual / multi-metal atom synergistic systems, carbon-based high-entropy single-atom catalysts (HE-SAC) offer significant advantages in both wide-range adsorption energy decoupling and high stability, potentially overcoming the limitations of the linear scaling relationship of adsorption energy and showing better application prospects. However, the controllable synthesis of carbon-based HE-SAC still faces challenges such as multi-metal dispersion and thermal stability imbalance, misaligned coordination microenvironment, and low mass transfer rate. Summary of the Invention The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a carbon-based high-entropy single-atom catalyst and its preparation method.

[0003] The first objective of this invention is to provide a method for preparing a carbon-based high-entropy single-atom catalyst, comprising the following steps: S1: Monodisperse SiO2 particles are co-dissolved or dispersed in a solvent with silicate-based twin monomers and polymetallic carboxylates; S2: Add methanesulfonic acid as a catalyst, disperse evenly, encapsulate, freeze, vacuum, dissolve and then place in a vacuum oven to react. The reactants in step S1 undergo twinning polymerization to confine and construct SiO2@polymer / metal carboxylate / SiO2 core-shell complex. S3: High-temperature thermal conversion and NaOH solution etching to remove SiO2, yielding a carbon-based high-entropy single-atom catalyst.

[0004] Furthermore, the particle size of the monodisperse SiO2 particles is 5 nm to 100 nm.

[0005] Furthermore, the silicate-based twinning monomer is a mixed twinning monomer in which the molar ratio of pyrrole and thiophene methoxysilicate is 1:3 to 3:1.

[0006] Furthermore, the spatial aggregation degrees of freedom for twin monomers are f = 2 ~ 4.

[0007] Furthermore, the polymetallic carboxylate M(RCOO)2, where M = at least five metal elements selected from Fe, Co, Ni, Cu, Mn, Zn, Sn, and Cr, has the following molar proportions of each metal element in the total metal: Fe and Co account for 10% to 30%; Ni and Cu account for 8% to 20%; and Mn, Zn, Sn, and Cr account for 5% to 15%.

[0008] Furthermore, the chain length of the polymetallic carboxylates ranges from C4 to C8.

[0009] Furthermore, in step S2, the acid catalysis temperature is 60 ℃~120 ℃, and the reaction time is 24 h~72 h.

[0010] Furthermore, in step S3, the temperature of the high-temperature thermal conversion is 800 ℃~1200 ℃.

[0011] Furthermore, in step S3, the etching temperature of the NaOH solution is 40 ℃~80 ℃.

[0012] A second objective of this invention is to provide a carbon-based high-entropy single-atom catalyst prepared by the method described above.

[0013] This invention utilizes an organic-inorganic dual continuous phase interface confinement system to suppress metal migration and aggregation by employing the spatial confinement effect of the prepared nano / sub-nanometer scale carbon-based high-entropy single-atom catalyst. Combined with the principle of maximizing configurational entropy, it achieves high-density uniform dispersion of multi-metal atoms, ensuring the long-term stability of high-density active sites.

[0014] This invention expands the adsorption energy decoupling range by directionally designing silicate-based twin monomers with N and S heteroatoms and controlling their mixing ratio.

[0015] This invention regulates the degree of freedom of inorganic segment polymerization of silicate-based twin monomers, constructs a microporous-mesoporous interconnected channel structure, optimizes the directional mass transfer path of reactants and intermediate products, significantly reduces the dynamic interference of local concentration polarization on adsorption energy decoupling, and improves the mass transfer rate.

[0016] This invention simultaneously achieves the optimization of the coordination microenvironment and the construction of porous structures through the synergistic effect of organic phase molecular design and inorganic phase topological structure regulation, completing precise cross-scale control from atomic coordination to mesoscopic channel structure. Through multi-metal synergistic electronic orbital coupling, the organic phase molecule MN... X S Y By precisely controlling the coordination configuration and designing a hierarchical pore system, a novel mechanism for dynamic decoupling of the adsorption energy of carbon-based HS-SACs with a wide range is constructed, breaking through the thermodynamic limitation of the linear scaling relationship in ORR and realizing the wide-range decoupling of the adsorption energy of reaction intermediates and the optimization of the catalytic pathway.

[0017] This invention develops a novel cross-scale synergistic regulation strategy for confined thermal conversion in twin polymerization, overcoming the thermodynamic constraints between the dispersion and thermal stability of multi-metal atoms to achieve high-density uniform loading of high-entropy single atoms; it establishes an organic-inorganic phase synergistic regulation method to optimize the matching between the coordination microenvironment of high-entropy active sites and hierarchical mass transfer channels; and it constructs a synergistic system of "confined encapsulation-coordination regulation-pore design," providing innovative methodological support for the controllable preparation of carbon-based HE-SACs.

[0018] We designed and constructed a novel carbon-based HS-SACs system and developed a non-precious metal ORR catalyst that combines wide-range adsorption energy decoupling, high loading, high stability and rapid mass transfer. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of the present invention; Figure 2 The image shows a transmission electron microscope (TEM) image of the catalyst morphology prepared in Example 1. Figure 3 Spherical aberration corrected HAADF STEM image of the catalyst prepared in Example 1; Figure 4 , Figure 5 The specific surface area and pore size analysis diagrams are for the catalyst prepared in Example 1. Figure 6 LSV curve of the catalyst prepared in Example 1; Figure 7 The LSV curve of the catalyst prepared for Comparative Example 1. Detailed Implementation

[0020] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0021] Example 1: This example demonstrates the preparation of a high-entropy single-atom catalyst, such as... Figure 1 As shown, the specific preparation steps are as follows: (1) Monodisperse SiO2 particles (particle size of 50 nm) were co-dissolved with silicate-based twin monomers (the molar ratio of pyrrole methoxysilicate to thiophene methoxysilicate was 2:1; the spatial polymerization degree of silicate-based twin monomers was f=4, i.e., TEPS:TETS=2:1) ​​and polymetallic carboxylates (Co: 30%, Fe: 30%, Ni: 15%, Cr: 15%, Zn: 10%) in dimethylformamide solvent.

[0022] (2) Add methanesulfonic acid as a catalyst, disperse evenly, encapsulate, freeze, vacuum, dissolve and place in a vacuum oven, react at 100 ℃ for 48 h. The reactants undergo twinning polymerization to obtain SiO2@polymer / metal carboxylate / SiO2 core-shell composite.

[0023] (3) The product obtained in (2) was placed in a tube furnace and treated at 400 °C for 2 h. After the high temperature treatment, the sample was washed and dried in deionized water, and then placed in a prepared 5M NaOH solution. The temperature was controlled at 60 °C and etched for 30 min. The product was then removed, washed with a large amount of deionized water and dried to obtain hierarchical porous hollow carbon spheres supported on HE-SACs.

[0024] The obtained hierarchical porous hollow carbon spheres loaded with HE-SAC were ground in a mortar until a uniform and fine powder was formed. 3 mg of the catalyst powder was weighed and placed in a 3 mL sample vial, along with 475 μL of anhydrous ethanol and 25 μL of Nafion to form a slurry. The slurry was then sonicated for 30 min to ensure uniform dispersion of the catalyst in the solvent. 10 μL of the slurry was pipetted onto the electrode, allowed to stand, and then air-dried. The slurry was then heated at 0.1 mol·L⁻¹. -1 The test was conducted in NaOH electrolyte. The reaction conditions were: 0.1 mol·L⁻¹ - 1 NaOH electrolyte was saturated with O2, and linear sweep voltammetry curves were obtained at room temperature by scanning at 400 / 625 / 900 / 1225 / 1600 rpm and 10 mV / s.

[0025] See appendix Figure 2 The image shown is a transmission electron microscope (TEM) image of the catalyst morphology prepared according to the technical solution of this example. It can be seen that a hierarchical porous hollow carbon sphere structure was successfully formed.

[0026] See appendix Figure 3 The image shows a spherical aberration corrected HAADF STEM image of the catalyst prepared according to the technical solution of this example. It can be clearly seen that the metal elements in the catalyst are uniformly dispersed on the surface of the material and there is no particle agglomeration, indicating that it is a single-atom catalyst.

[0027] Figure 4 , Figure 5 The specific surface area and pore size analysis (BET) diagram of the catalyst prepared in Example 1 shows that the material has a large specific surface area and verifies its hierarchical porous structure. The construction of a microporous-mesoporous interconnected channel structure enables the catalyst to have a high mass transfer rate.

[0028] Figure 6 The LSV curve of the catalyst prepared in Example 1; from Figure 6It can be seen that the half-wave point of this catalyst is about 0.965, which is significantly higher than that of commercial platinum-carbon catalysts.

[0029] Example 2: This example demonstrates the preparation of a high-entropy single-atom catalyst. (1) Monodisperse SiO2 particles (50 nm in diameter) were dissolved in dimethylformamide solvent along with silicate-based twin monomers (pyrrole methoxysilicate: thiophene methoxysilicate = 2:1; the spatial polymerization degree of the silicate-based twin monomers was f = 3, i.e., TRPS:TRTS = 2:1) and polymetallic carboxylates. Other steps were the same as in Example 1.

[0030] Example 3: This example demonstrates the preparation of a high-entropy single-atom catalyst. (1) Monodisperse SiO2 particles (particle size of 50 nm) are dissolved together with silicate-based twin monomers (pyrrole methoxysilicate: thiophene methoxysilicate = 1:1; the spatial polymerization degree of silicate-based twin monomers is f=3, i.e. TRPS:TRTS=1:1) and polymetallic carboxylates in dimethylformamide solvent.

[0031] Everything else is the same as in Example 1.

[0032] Comparative Example 1 (without monodisperse SiO2 particles) (1) The silicate-based twin monomers (the molar ratio of pyrrole methoxysilicate to thiophene methoxysilicate is 2:1; the spatial polymerization degree of silicate-based twin monomers is f=2, i.e., TEPS:TETS=2:1) ​​and polymetallic carboxylates (Co:30%, Fe:30%, Ni:15%, Cr:15%, Zn:10%) are co-dissolved in dimethylformamide solvent.

[0033] Everything else is the same as in Example 1.

[0034] Figure 7 The LSV curve of the catalyst prepared in Comparative Example 1 is shown; Figure 6 Compared with the catalyst prepared in Example 1, it can be seen that the addition of hard template monodisperse SiO2 particles significantly improves the performance of the catalyst.

[0035] For any points not covered above, existing technologies shall apply.

[0036] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon-based high-entropy single-atom oxygen reduction reaction catalyst, characterized in that, Includes the following steps: S1: Monodisperse SiO2 particles are co-dissolved or dispersed in a solvent with silicate-based twin monomers and polymetallic carboxylates; S2: Add methanesulfonic acid as a catalyst, disperse evenly, encapsulate, freeze, vacuum, dissolve and then place in a vacuum oven to react. The reactants in step S1 undergo twinning polymerization to confine and construct SiO2@polymer / metal carboxylate / SiO2 core-shell complex. S3: High-temperature thermal conversion at 400 ℃ for 2 h and etching with NaOH solution to remove SiO2 were used to prepare a carbon-based high-entropy single-atom catalyst. The silicate-based twinning monomer is a mixture of pyrrole methoxysilicate and thiophene methoxysilicate in a molar ratio of 1:3 to 3:

1. The polymetallic carboxylate M(RCOO)2, M = Fe, Co, Ni, Cr, Zn, consists of 5 metal elements, and the molar proportions of each metal element in the total metal are: Fe 10%~30%, Co 10%~30%, Ni 8%~20%, Zn 5%~20%, and Cr 5%~20%. The particle size of monodisperse SiO2 particles ranges from 5 nm to 100 nm.

2. The preparation method according to claim 1, characterized in that, The chain length of polymetallic carboxylates ranges from C4 to C8.

3. The preparation method according to claim 1, characterized in that, In step S2, the acid catalysis temperature is 60 ℃~120 ℃, and the reaction time is 24 h~72 h.

4. The preparation method according to claim 1, characterized in that, In step S3, the etching temperature of the NaOH solution is 40℃~80℃.

5. A carbon-based high-entropy single-atom oxygen reduction catalyst prepared by the preparation method according to any one of claims 1-4.

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