Transition metal-based triatomic oxygen reduction catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oxygen reduction catalysts, in particular to a transition metal-based triatomic oxygen reduction catalyst and a preparation method and application thereof. The invention relates to a preparation method of a transition metal-based triatomic oxygen reduction catalyst. The preparation method comprises the following steps: dispersing carbon nanotubes in a solvent to obtain a dispersion liquid; adding transition metal acetate, urea and 4, 4 '-dihydroxy [1, 1'-biphenyl]-3, 3 ', 5, 5'-tetracarboxaldehyde into the dispersion liquid, performing ultrasonic treatment to obtain mixed liquid, and then performing heating reaction in an inert atmosphere; and after the reaction is finished, naturally cooling to room temperature, filtering, washing and drying to obtain the transition metal-based triatomic oxygen reduction catalyst. The catalyst designed by the invention not only has an efficient catalytic active site, but also remarkably improves the material transmission efficiency and enhances the utilization rate of a catalytic active center by optimizing the structure of a composite material, so that the synergistic enhancement of the electro-catalytic performance is realized.

Description

Technical Field

[0001] This invention relates to the field of oxygen reduction catalyst technology, and in particular to a transition metal-based triatomic oxygen reduction catalyst, its preparation method, and its application. Background Technology

[0002] The oxygen reduction reaction (ORR) is the core reaction in fuel cells and zinc-air batteries. Its basic process involves the transfer of protons (H+) to fuel cells. + ) and electrons (e - The coupling transfer of oxygen gradually reduces molecular oxygen to water. Currently, platinum group metal catalysts (such as Pt / C) exhibit excellent catalytic performance in ORR reactions, but their high cost and resource scarcity make them unsuitable for large-scale applications. Therefore, there is an urgent need to design and synthesize non-precious metal ORR catalysts that are highly active, highly stable, low-cost, and abundant in resources.

[0003] With the continuous advancement of in-situ characterization techniques and computational chemistry, ORR catalyst research has gradually shifted from traditional nanoparticles to more refined metal clusters, ultimately achieving the design and application of atomically dispersed catalysts. Single-atom catalysts (SACs), with their atomically dispersed active sites, high conductivity, and tunable coordination environments, have become a hot topic in non-noble metal ORR catalyst research. In particular, typical active sites represented by the M-N4 structure, combined with strategies such as heteroatom doping, defect engineering, and axial coordination modulation, have effectively optimized the adsorption energy of intermediate products and exhibited catalytic activity close to that of commercial Pt / C catalysts in alkaline media. However, SACs are still limited by the linear scaling relationship of adsorption energy, and cannot independently optimize the adsorption energy of intermediate products, which to some extent limits further improvements in catalytic efficiency and reaction kinetics. Diatom catalysts (DACs), as an extension of SACs, have become a focus of non-noble metal ORR catalyst research due to their ability to regulate the linear scaling relationship of adsorption energy. DACs, through the synergistic effect of adjacent metal centers, regulate the charge distribution of adsorbed intermediate products, thereby optimizing the kinetic performance of the catalytic reaction and significantly improving catalytic activity. However, the catalytic performance of DACs has not yet fully met expectations, mainly due to the fixed spatial location of the bimetallic sites. This limitation restricts the range of adsorption energy adjustment, making it difficult to achieve completely independent optimization of the adsorption energies of each intermediate. Therefore, further research is needed to address issues such as the optimization of catalytic efficiency and reaction kinetics in DACs, in order to drive the field towards greater efficiency and stability.

[0004] In recent years, trimetallic atom catalysts (TACs) have emerged as a novel approach to address this problem by further modulating the linear scaling relationship of adsorption energy through the synergistic effect between the three metal atoms. Through the synergistic interaction between adjacent metal centers, the charge distribution of adsorbed intermediates can be adjusted, thereby optimizing the kinetic performance of the catalytic reaction and significantly enhancing catalytic activity. TACs have shown great potential in decoupling adsorption energy, improving long-term stability, and optimizing reaction kinetics. However, the preparation of TACs still faces challenges. Existing methods mainly focus on pyrolytic synthesis, a process often accompanied by problems such as the contradiction between metal dispersibility and thermal stability, excessive energy consumption, and environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by proposing a transition metal-based triatomic oxygen reduction catalyst, its preparation method, and its applications. A solvothermal method is used to prepare the transition metal-based triatomic oxygen reduction catalyst, resulting in an ORR non-noble metal catalyst that combines broad-range adsorption energy decoupling, high active site density, and long-lasting stability.

[0006] The first objective of this invention is to provide a method for preparing a transition metal-based triatomic oxygen reduction catalyst, comprising the following steps: Carbon nanotubes are dispersed in a solvent to obtain a dispersion; A mixture was obtained by adding a transition metal acetate, urea, and 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxylic aldehyde to the dispersion and then sonicating it. The mixture was then heated under an inert atmosphere. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, washed, and dried to obtain the transition metal-based triatomic oxygen reduction catalyst.

[0007] Furthermore, the solvent is a mixed solution of dimethylformamide and 1,4-dioxane in a volume ratio of 1-2:1.

[0008] Furthermore, the mass-to-volume ratio of carbon nanotubes to solvent is 10~30 mg: 5 ml.

[0009] Furthermore, the molar ratio of carbon nanotubes to transition metal acetate, urea, and 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxylic aldehyde is 10~30 mg: 0.03 mmol: 0.06 mmol: 0.03 mmol.

[0010] Furthermore, the transition metal acetate is any one of cobalt acetate, ferrous acetate, or nickel acetate.

[0011] Furthermore, the reaction temperature for the heating reaction is 100~160 ℃, and the reaction time is 24~72 h.

[0012] Furthermore, the mixture is rapidly frozen in a liquid nitrogen bath, then degassed, and slowly thawed to room temperature; this freeze-degass-thaw cycle is repeated three times to create an inert atmosphere.

[0013] Further, it was washed in sequence with deionized water, dimethylformamide, and ethanol.

[0014] A second objective of this invention is to provide a transition metal-based triatomic oxygen reduction catalyst prepared using the above-described preparation method.

[0015] A third objective of this invention is to provide an application of the transition metal-based triatomic oxygen reduction catalyst described above in oxygen reduction reactions, oxygen evolution reactions, hydrogen evolution reactions, hydroxide reactions, or carbon dioxide reduction reactions.

[0016] This invention presents a novel solvothermal method for preparing transition metal-based triatomic oxygen reduction catalysts. The method involves uniformly dispersing carbon nanotubes (CNTs) in a reactant solution system. Aromatic aldehydes and urea derivatives, under the guidance of metal ions, undergo Schiff base condensation polymerization and π-π interactions between the conjugated aromatic aldehyde units and the large aromatic system of CNTs, leading to in-situ assembly on the CNT surface and the construction of a CNT-supported COF heterostructure. This improves the conductivity and accessibility of the catalytic sites in the composite catalyst, fully activating the activity of the trimetallic catalytic sites.

[0017] This invention achieves the construction of highly efficient active centers with clear structures and well-defined sites through the synergistic effect of covalent and coordinate bonds. By precisely designing the structure of the composite material, the mass transport pathway is optimized, significantly enhancing diffusion and mass transfer efficiency, and ultimately achieving a synergistic improvement in electrocatalytic performance. It should be emphasized that the reaction nature of triatomic N6O3M3 and diatomic N4O2M2 is different, and the specific types of chemical bonds, bond lengths, and bond angles in the synthesized active centers are also different.

[0018] In summary, the catalyst designed in this invention not only possesses highly efficient catalytic active sites, but also significantly improves mass transport efficiency and enhances the utilization rate of catalytic active centers by optimizing the structure of the composite material, thereby achieving synergistic enhancement of electrocatalytic performance.

[0019] This invention provides a simple and efficient synthesis method that can avoid the problems of metal dispersion and thermal stability during pyrolysis, while overcoming the environmental pollution and high energy consumption problems of existing preparation methods. It has strong innovation and practical application potential. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation method in Example 1; Figure 2Transmission electron microscopy (TEM) image of the sample prepared in Example 1; Figure 3 Transmission electron microscopy (TEM) image of the sample prepared in Example 2; Figure 4 The graph shows the performance data of the samples prepared in Examples 1 and 2. Detailed Implementation

[0021] 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.

[0022] The preparation method of the present invention (see) Figure 1 Commercially available multi-walled carbon nanotubes are uniformly dispersed in the reactant solution system. Under suitable conditions, they are released through the reaction via transition metal ions (shown as Co in the figure). 2+ The template-guided action of COFs drives the orderly progress of Schiff base condensation reactions. During this process, π-π interactions are formed between the conjugated aromatic aldehyde units and the large aromatic system of CNTs, promoting the in-situ assembly of COFs on the surface of CNTs and constructing CNTs-supported COFs heterostructures.

[0023] Example 1 Preparation of cobalt metal triatomic oxygen reduction catalyst.

[0024] (1) Carbon nanotubes were dispersed in a specific solvent in a 10 mL heat-resistant glass tube to obtain dispersion A; (2) Urea and 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxyaldehyde were added to the dispersion A obtained in step (1), followed by ultrasonic dissolution. The resulting solution was rapidly frozen in a liquid nitrogen bath, then degassed, and slowly thawed to room temperature. This freeze-degasting-thawing cycle was repeated three times. A heat-resistant glass tube was heated at a specific temperature for a specific time. (3) After the reaction solution obtained in step (2) is naturally cooled to room temperature, the precipitate is collected by filtration, washed with deionized water, dimethylformamide and ethanol in sequence, and dried under vacuum at 80°C overnight.

[0025] The specific solvent in step (1) is a mixed solution of dimethylformamide and 1,4-dioxane in a volume ratio of 1:1.

[0026] In steps (1) and (2), the mass of carbon nanotubes, the molar amount of transition metal salt, the molar amount of urea, the molar amount of 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxyaldehyde, and the volume ratio of a specific solvent are 20 mg: 0.03 mmol: 0.06 mmol: 0.03 mmol: 5 ml.

[0027] The transition metal acetate is cobalt acetate.

[0028] The reaction temperature in step (2) is 120 °C and the reaction time is 72 h.

[0029] Example 2 Preparation of nickel metal triatomic oxygen reduction catalyst.

[0030] (1) Carbon nanotubes were dispersed in a specific solvent in a 10 mL heat-resistant glass tube to obtain dispersion A; (2) Urea and 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxyaldehyde were added to the dispersion A obtained in step (1), followed by ultrasonic dissolution. The resulting solution was rapidly frozen in a liquid nitrogen bath, then degassed, and slowly thawed to room temperature. This freeze-degasting-thawing cycle was repeated three times. A heat-resistant glass tube was heated at a specific temperature for a specific time. (3) After the reaction solution obtained in step (2) is naturally cooled to room temperature, the precipitate is collected by filtration, washed with deionized water, dimethylformamide and ethanol in sequence, and dried under vacuum at 80°C overnight.

[0031] The specific solvent in step (1) is a mixed solution of dimethylformamide and 1,4-dioxane in a volume ratio of 1:1.

[0032] In steps (1) and (2), the mass of carbon nanotubes, the molar amount of transition metal salt, the molar amount of urea, the molar amount of 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxyaldehyde, and the volume ratio of a specific solvent are 20 mg: 0.03 mmol: 0.06 mmol: 0.03 mmol: 5 ml.

[0033] The transition metal acetate is nickel acetate.

[0034] The reaction temperature in step (2) is 120 °C and the reaction time is 72 h.

[0035] Morphological analysis using transmission electron microscopy (TEM) further fully demonstrates the successful construction of the composite material structure in Example 1. For example... Figure 2 As shown in the TEM images, the composite material clearly retains the chain-like nanosphere morphology of KB, assembled from uniformly sized, approximately 50 nm diameter regular nanospheres. Furthermore, each nanosphere surface is uniformly coated with a continuous and dense confined cobalt metal polymer thin layer, indicating that the cobalt metal polymer can achieve stable and consistent growth on the carbon support surface. This morphological feature further supports the effective construction of the composite structure and its potential structural synergistic effects.

[0036] Morphological analysis using transmission electron microscopy (TEM) further validated the structural characteristics of the composite material in Example 2. For example... Figure 3 As shown, the results indicate that the composite material still exhibits a KB chain-like nanosphere architecture, consisting of uniformly distributed nanospheres with a diameter of approximately 50 nm. Its outer layer is uniformly covered with a continuous confined nickel polymer film, demonstrating that the metal polymer can achieve stable coating and controlled construction on a carbon-based framework.

[0037] The electrocatalytic ORR performance of the materials prepared in Examples 1 and 2 was systematically evaluated using a rotating disk electrode (RDE) in an O2-saturated 0.1 M KOH solution, with commercial 20% Pt / C as a reference. As shown in Figure 4a, the cyclic voltammetry (CV) results under O2 and N2 atmospheres showed that Co-CP@KB had the most positive cathode peak potential (0.938 V), reflecting the high intrinsic activity due to the three atomic sites.

[0038] At a rotational speed of 400–1600 rpm and a scan rate of 10 mV / s -1 Linear sweep voltammetry (LSV) tests were conducted under the specified conditions. As shown in Figures 4b–d, the half-wave potential of Co-CP@KB at 1600 rpm was 0.953 V, significantly higher than that of Pt / C (0.845 V) and superior to that of Ni-CP@KB (0.921 V). Furthermore, the onset potential of Co-CP@KB reached 1.029 V, significantly better than that of Pt / C (0.998 V), further demonstrating its superior ORR kinetic performance.

[0039] For any points not covered above, existing technologies shall apply.

[0040] 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 the preparation of a transition metal-based triatomic oxygen reduction catalyst, characterized in that, Includes the following steps: Carbon nanotubes are dispersed in a solvent to obtain a dispersion; A mixture was obtained by adding a transition metal acetate, urea, and 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxylic aldehyde to the dispersion and then sonicating it. The mixture was then heated under an inert atmosphere. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered, washed, and dried to obtain the transition metal-based triatomic oxygen reduction catalyst.

2. The production method according to claim 1, wherein The solvent is a mixed solution of dimethylformamide and 1,4-dioxane in a volume ratio of 1-2:

1.

3. The production method according to claim 1, characterized by, The mass-to-volume ratio of carbon nanotubes to solvent is 10~30 mg: 5 ml.

4. The preparation method according to claim 1, characterized in that, The molar ratio of carbon nanotubes to transition metal acetate, urea, and 4,4′-dihydroxy[1,1′-biphenyl]-3,3′,5,5′-tetracarboxylic aldehyde was 10~30 mg: 0.03 mmol: 0.06 mmol: 0.03 mmol.

5. The preparation method according to claim 1, characterized in that, The transition metal acetate is any one of cobalt acetate, ferrous acetate, or nickel acetate.

6. The preparation method according to claim 1, characterized in that, The reaction temperature for the heating reaction is 100~160 ℃, and the reaction time is 24~72 h.

7. The preparation method according to claim 1, characterized in that, The mixture is rapidly frozen in a liquid nitrogen bath, then degassed and slowly thawed to room temperature; this freeze-degass-thaw cycle is repeated three times to create an inert atmosphere.

8. The preparation method according to claim 1, characterized in that, Wash with deionized water, dimethylformamide and ethanol in sequence.

9. A transition metal-based triatomic oxygen reduction catalyst prepared by the preparation method according to any one of claims 1-8.

10. The application of a transition metal-based triatomic oxygen reduction catalyst as described in claim 9 in oxygen reduction reactions, oxygen evolution reactions, hydrogen evolution reactions, hydrogen oxidation reactions, or carbon dioxide reduction reactions.

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