Preparation method and application of high-loading copper monatomic catalyst
A high-load copper single-atom catalyst was prepared by using copper nitrate trihydrate and guanine as raw materials in a simple two-step method. This method solved the problems of dispersion and stability of single-atom catalysts under high loading, and achieved high catalytic activity and stability, which is suitable for the selective oxidation of benzene to phenol.
Patent Information
- Application Number
- CN202411916290.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2044-12-24
AI Technical Summary
Existing technologies struggle to maintain the dispersion and stability of single-atom catalysts under high loading, and the preparation methods are complex, making it difficult to balance catalyst activity and stability, thus limiting their large-scale development in practical applications.
A high-load copper single-atom catalyst was prepared by using copper nitrate trihydrate and guanine, a small biomolecule, as raw materials through a simple two-step method, including freeze-drying and high-temperature carbonization. The self-assembly ability and high nitrogen content of guanine are utilized to form stable nitrogen coordination sites, preventing metal atom aggregation and improving the stability and activity of the catalyst.
A copper single-atom catalyst with high loading capacity and excellent catalytic activity and stability was successfully prepared for the selective oxidation of benzene to phenol. It exhibited high conversion rate and cycle stability, and the cost was reduced through a green and environmentally friendly synthesis process.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of single-atom catalyst preparation, and particularly relates to a preparation method of a high-loading copper single-atom catalyst and application thereof. BACKGROUND
[0002] The concept of single-atom catalysts (SACs) was proposed in 2011, i.e. all active sites are dispersed in the form of atoms on the support, so as to realize a catalyst system with theoretically 100% atom utilization rate (Acc. Chem. Res. 2013, 46, 8, 1740-1748). Unlike the catalysts based on nanoparticles, the isolated single atoms of the single-atom catalysts are usually anchored together with the heteroatoms of the support. The strong interaction between the catalyst and the support can ensure the uniform dispersion of the metal atoms, and therefore the selection of the support material is crucial for realizing the excellent catalytic activity and stability of SACs. So far, metal atoms have been effectively anchored on various supports such as metals, metal oxides, zeolites and even nanocarbon materials (especially nitrogen-doped carbon-based materials) (Adv. Funct. Mater. 2021, 31, 2008318). The two-dimensional (2D) nitrogen-doped carbon nanosheet provides a large number of reaction sites for SACs due to its extremely high specific surface area, and effectively shortens the distance between the active sites and the reaction molecules, thereby accelerating the catalytic process. In addition, the doping of nitrogen elements not only can change the chemical and electronic structure of the carbon nanosheet, enhance its electronic transmission performance, and promote efficient electron transfer in the catalytic process, but also introduce additional active centers such as edge defects and nitrogen active sites, which significantly affect the path and efficiency of the catalytic reaction.
[0003] In view of the unique electronic structure, extreme atom utilization rate and enhanced intrinsic catalytic activity of SACs, it exhibits great application potential in various catalytic fields, covering key processes such as oxidation, reduction, pollutant degradation, CO2 electrochemical conversion and hydrogen energy generation (Nat Commun, 2019, 10, 4290). However, contrary to the zero-valent characteristics of bulk metals, a single metal atom often presents a positive charge state due to the transfer of electrons from the central metal site to the substrate, thereby depriving them of the metal characteristics required for effective adsorption and activation of specific catalytic reactions. At the same time, the inherent adsorption-energy balance mechanism of SACs can also pose challenges to the reaction kinetics and thermodynamics, especially for complex reactions involving multiple intermediates.
[0004] To address the above problems, recent research has focused on the development of high-density SACs, which exhibit unique geometrical and electronic structures, aiming to optimize the efficiency of large-scale industrial applications by improving the mass-specific activity. High-density SACs not only facilitate inter-site electron transfer, spin coupling, or charge redistribution, thereby fine-tuning the local environment of active sites, but also can stimulate the synergistic effect of adjacent metal centers, allowing reaction intermediates to be simultaneously adsorbed on multiple sites, breaking the constraints of traditional adsorption-energy balance mechanisms (ACS Catal. 2023, 13, 1316−1325).
[0005] The current methods for preparing single-atom catalysts mainly have the following disadvantages: metal atoms are prone to agglomeration to form nanoparticles at high loadings, making it difficult to maintain high dispersion of single atoms; the binding force between the metal and the support is insufficient, which easily leads to single atom migration and deactivation; some preparation methods have complex conditions and high requirements for the surface chemistry and structure of the support; it is difficult to balance the stability and activity of the catalyst while achieving high loadings, which limits the large-scale development of single-atom catalysts in practical applications (Prog. Chem. 2020, 32(1): 23-32). Therefore, it is of great practical significance to develop a simple and efficient synthesis method. SUMMARY
[0006] The purpose of the present application is to provide a preparation method of high-loading copper single-atom catalyst and its application. In order to explore a better preparation method of high-loading single-atom catalyst, the present application uses copper nitrate trihydrate and biological small molecule guanine as raw materials to successfully prepare a high-loading copper single-atom catalyst through a simple two-step method.
[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:
[0008] A preparation method of high-loading copper single-atom catalyst, comprising the following steps:
[0009] (1) Disperse copper nitrate trihydrate and biological small molecule guanine in deionized water, stir in an oil bath to obtain a precursor solution, and freeze-dry to obtain a precursor;
[0010] (2) Grind the precursor obtained in step (1) into powder, heat to a specific temperature under a protective atmosphere, and then react after holding, and then naturally cool to room temperature, and grind to obtain a copper single-atom catalyst.
[0011] Further, in step (1), the mass ratio of biological small molecule guanine to copper nitrate trihydrate is 3: (0.21-1.63).
[0012] Further, in step (1), the volume of deionized water is 50 mL.
[0013] Further, the temperature of the oil bath in step (1) is 100 o C, the stirring time is 12 h, and the stirring speed is 500 rpm.
[0014] Further, the protective atmosphere in step (2) is N2.
[0015] Further, the heating rate in step (2) is 1 o C / min, the specific temperature is 700 o C, and the holding time is 2 h.
[0016] A high-loading copper monatomic catalyst prepared by the above preparation method.
[0017] Application of the above high-loading copper monatomic catalyst in selective oxidation of benzene to phenol.
[0018] The conditions are as follows: the heating rate is 1 o C / min; the high-temperature carbonization temperature is 700 o C; and the carbonization time is 2 h.
[0019] Compared with the prior art, the present application has the beneficial effects that:
[0020] The present patent innovatively uses a biological small molecule guanine and copper nitrate trihydrate as precursors, and successfully prepares a high-loading copper monatomic catalyst through only two steps of self-assembly and high-temperature carbonization by a simple chemical synthesis strategy from bottom to top. The synthesis process is simple in operation, low in manufacturing cost, and strong in sustainability. The obtained catalyst has a curled two-dimensional morphology, high nitrogen content (~ 30 at%) and metal loading (the copper content can be as high as 33.2 wt%). In addition, in the reaction of selective oxidation of benzene to phenol, the series of catalysts exhibit excellent catalytic activity and stability, and the mechanism of H2O2 decomposition and benzene oxidation to phenol is revealed through experiments and theoretical calculations.
[0021] Guanine as a precursor exhibits significant advantages in the preparation of high-loading monatomic catalysts. Its high nitrogen content can form stable nitrogen coordination sites (such as M-N xThe guanine molecule has a strong self-assembly ability and forms an ordered structure through hydrogen bonding. After pyrolysis, it provides an ideal platform for the uniform distribution of metal single atoms. The amino and carbonyl groups in the molecule have good coordination properties and can form stable complexes with metal precursors, further improving the metal loading and dispersion. In addition, the tunability of the guanine structure and function allows flexible regulation of material performance by optimizing pyrolysis conditions to meet different catalytic needs. As a green and environmentally friendly biomolecule raw material, the guanine preparation process is environmentally friendly, providing an efficient, economical and sustainable way to develop high-performance single-atom catalysts, and has important application potential. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 Synthesis scheme of copper single-atom catalyst.
[0023] Figure 2 Scanning electron microscope (SEM) of Cu 30 G in Example 5.
[0024] Figure 3 Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) of Cu 30 G in Example 5.
[0025] Figure 4 X-ray photoelectron spectroscopy (XPS) of the catalysts obtained in Examples 1-5.
[0026] Figure 5 X-ray absorption near-edge structure spectroscopy (XANES) of the catalysts obtained in Examples 1-5.
[0027] Figure 6 Catalytic activity of the catalysts obtained in Examples 1-5 for selective oxidation of benzene to phenol.
[0028] Figure 7 Cyclic stability test of Cu 30 G in Example 5 for selective oxidation of benzene to phenol.
[0029] Figure 8 Reaction mechanism diagram of copper single-atom catalyst for H2O2 decomposition and benzene oxidation to phenol. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all embodiments.
[0031] Example 1 Cu5G
[0032] (1) Weigh 0.21 g of copper nitrate trihydrate and 5 g of guanine and disperse them in a beaker containing 50 mL of deionized water. Heat the mixture at 100°C. o The precursor was obtained by stirring at 500 rpm for 12 h in an oil bath and then freeze-drying.
[0033] (2) After grinding the precursor, transfer it to an alumina crucible and heat it in a N2 atmosphere at 1 o Heating to 700°C at a heating rate of C / min o C, keep warm for 2 hours, and after the process is complete, allow it to cool naturally to room temperature. Grind the mixture to obtain a copper single-atom catalyst, named Cu5G.
[0034] Example 2 Cu 10 G
[0035] (1) Weigh 0.42 g of copper nitrate trihydrate and 5 g of guanine and disperse them in a beaker containing 50 mL of deionized water. Heat the mixture at 100°C. o The precursor was obtained by stirring in an oil bath for 12 hours and then freeze-drying.
[0036] (2) After grinding the precursor, transfer it to an alumina crucible and heat it in a N2 atmosphere at 1 o Heating to 700°C at a heating rate of C / min o C, heat for 2 hours, then allow to cool naturally to room temperature. Grind to obtain the copper single-atom catalyst, named Cu. 10 G.
[0037] Example 3 Cu 15 G
[0038] (1) Weigh 0.67 g of copper nitrate trihydrate and 5 g of guanine and disperse them in a beaker containing 50 mL of deionized water. Heat the mixture at 100°C. o The precursor was obtained by stirring in an oil bath for 12 hours and then freeze-drying.
[0039] (2) After grinding the precursor, transfer it to an alumina crucible and heat it in a N2 atmosphere at 1 o Heating to 700°C at a heating rate of C / min o C, heat for 2 hours, then allow to cool naturally to room temperature. Grind to obtain the copper single-atom catalyst, labeled Cu. 15 G.
[0040] Example 4 Cu 20 G
[0041] (1) Weigh 0.95 g of copper nitrate trihydrate and 5 g of guanine and disperse them in a beaker containing 50 mL of deionized water. Heat the mixture at 100°C. oC oil bath under stirring for 12 h, and then the precursor was obtained after freeze-drying;
[0042] (2) The precursor was ground and then transferred to a corundum crucible, and heated to 700 o C at a heating rate of 1 o C / min under N2 atmosphere, and kept for 2 h. After the reaction was completed, it was naturally cooled to room temperature, and then ground to obtain the copper monatomic catalyst, named Cu 20 G.
[0043] Example 5 Cu 30 G
[0044] (1) 1.63 g of copper nitrate trihydrate and 5 g of guanine were weighed and dispersed in a beaker containing 50 mL of deionized water, and stirred under a 100 o C oil bath for 12 h, and then the precursor was obtained after freeze-drying;
[0045] (2) The precursor was ground and then transferred to a corundum crucible, and heated to 700 o C at a heating rate of 1 o C / min under N2 atmosphere, and kept for 2 h. After the reaction was completed, it was naturally cooled to room temperature, and then ground to obtain the copper monatomic catalyst, named Cu 30 G.
[0046] Figure 1 Schematic diagram for synthesis of copper monatomic catalyst.
[0047] Figure 2 SEM image of Cu 30 G, which shows that Cu 30 G has a layered nanosheet morphology at a microscale.
[0048] Figure 3 AC HAADF-STEM image of Cu 30 G, which shows that the metal Cu is dispersed on the support in the form of monatomic.
[0049] The C, N, O, Cu element contents of the copper monatomic catalysts synthesized in Examples 1-5 are shown in Table 1. As can be seen from Table 1, the catalyst obtained by the present preparation method has a high nitrogen content (~30 at%) and a high metal loading (the copper content can be as high as 33.2 wt%).
[0050] Table 1 C, N, O, Cu element contents of Examples 1-5
[0051]
[0052] Figure 4XPS spectra of copper monatomic catalysts synthesized in Examples 1-5, as can be seen from the figure, all samples are composed of Cu, C, N, O elements, and the characteristic peak of Cu increases with the increase of loading.
[0053] Figure 5 X-ray absorption near-edge structure spectra of copper monatomic catalysts synthesized in Examples 1-5, the results show that the absorption edge energy of all samples is between Cu foil and CuO, indicating that the oxidation state of Cu atom center is between 0 and +2. At the same time, it can also be observed that with the increase of Cu content, the pre-edge absorption energy of the sample moves to lower energy, indicating that the average valence of Cu center decreases with the increase of Cu content.
[0054] Application examples
[0055] The catalysts obtained in Examples 1-5 were used for the reaction of selective oxidation of benzene to phenol, and the specific conditions were as follows: 0.3 mL of benzene, 5 mL of H2O2, 6 mL of acetonitrile and 5 mg of catalyst were mixed in a 48 mL thick-walled pressure bottle, and the reaction was carried out at 60 o C oil bath for 1 h. The concentrations of reactants and products were analyzed by GC-MS (GCMS-QP2010 SE) with tetradecane as an internal standard, and the results are shown in Table 1. Figure 6 The benzene conversion rate of catalyst Cu 30 G can be as high as 78.7%.
[0056] Figure 7 The cyclic stability test of Cu 30 G catalyzing the selective oxidation of benzene to phenol in Example 5, the results show that the conversion rate and selectivity of Cu 30 G do not change much in 6 catalytic cycle tests.
[0057] Figure 8 The reaction mechanism diagram of copper monatomic catalyst catalyzing H2O2 decomposition and benzene oxidation to phenol. The reaction first starts from the adsorption of H2O2 on the Cu-N x active site, which is conducive to its activation to generate O-Cu-Nx intermediate (step I). Then, C6H6 molecules are adsorbed on the Cu-O site (step II), and a Cu-N x -C6H5OH intermediate is generated by hydrogen transfer reaction (step III). Finally, the catalytic cycle is completed by desorption of C6H5OH molecules and regeneration of Cu-N x sites (step IV).
[0058] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.
Claims
1. A method for preparing a high loading copper monoatomic catalyst, characterized by: The method comprises the following steps: (1) dispersing copper nitrate trihydrate and biological small molecule guanine in deionized water, stirring in an oil bath to obtain a precursor solution, and freeze-drying to obtain a precursor; (2) grinding the precursor obtained in step (1) into powder, heating to a specific temperature under a protective atmosphere, and then naturally cooling to room temperature, and grinding to obtain a copper monatomic catalyst; In step (1), the mass ratio of the biological small molecule guanine to copper nitrate trihydrate is 5:(0.21-1.63); The rate of the temperature increase in step (2) is 1 o C / min, the specific temperature is 700 o C, and the holding time is 2 h.
2. The method of preparing a high loading copper monoxide catalyst according to claim 1, characterized by: In step (1), the volume of the deionized water is 50 mL.
3. The method of making a high loading copper monatomic catalyst of claim 1, wherein: The temperature of the oil bath in step (1) is 100 o C, the stirring time is 12 h, and the stirring speed is 500 rpm.
4. The method of making a high loading copper monoxide catalyst of claim 1, wherein: In step (2), the protective atmosphere is N2.
5. A high-loading copper monatomic catalyst prepared by the method of any one of claims 1-4.
6. Application of the high-loading copper monatomic catalyst of claim 5 in selective oxidation of benzene to phenol.