A transition metal polyatomic catalyst supported on carbon nitride and a preparation method and application thereof
Transition metal polyatomic catalysts were prepared on carbon nitride using pre-locked-nano confined polymerization technology, which solved the problems of high loading and uncontrollable configuration and achieved high efficiency photocatalytic performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FUDAN UNIVERSITY
- Filing Date
- 2026-01-13
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies make it difficult to achieve high-loading multi-atom catalysts on carbon nitride substrates, and the multi-atom configuration is uncontrollable, resulting in insufficient catalytic activity.
By employing a pre-locked-nano confined polymerization technique, the coordination between dicyandiamide nanoribbons and transition metal salts is achieved through hydrothermal treatment, thereby inhibiting the migration and aggregation of metal sites and enabling the self-assembly of multi-atom active centers to prepare a transition metal multi-atom catalyst supported on carbon nitride.
A high-loading (over 30 wt%) transition metal polyatomic catalyst was achieved, with precise configuration and optimized light absorption performance, significantly improving catalytic activity, especially its application potential in the field of photocatalysis.
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Figure CN122164466A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polyatomic catalyst synthesis technology, specifically relating to a transition metal polyatomic catalyst supported on carbon nitride, its preparation method, and its application. Background Technology
[0002] With the development of clean energy conversion technologies, carbon nitride-based catalysts have attracted widespread attention due to their visible light response characteristics and chemical stability. The layered structure and nitrogen-rich nature of carbon nitride allow for the anchoring of metal sites through a π-π conjugated system, improving the catalyst's band structure and charge separation efficiency, while simultaneously modulating the electronic structure of the metal sites. However, metal sites anchored on carbon nitride substrates typically exist in single-atom form, with metal loading generally below 3 wt%, and single metal active sites are insufficient to meet the requirements of complex catalytic reactions. Therefore, developing atomically dispersed multi-atom catalysts supported on carbon nitride with high loading is crucial.
[0003] However, the synthesis of multi-atom sites faces two major technical challenges: First, the contradiction between increasing metal loading and atomic dispersion. Although existing methods (such as co-calcination and template methods) can achieve atomic-level dispersion, the loading is mostly below 5 wt%, and metals tend to agglomerate to form low-activity nanoparticles under high loading. Second, the difficulty of precisely controlling the multi-atom configuration. Existing multi-atom catalysts are mainly diatomic catalysts with an interatomic distance of 0.45-0.6 nm. The relatively large interatomic distance is not conducive to coupling reactions, while linear and trigonal triatomic catalysts are difficult to synthesize in a controllable manner. Summary of the Invention
[0004] To address the aforementioned problems in the prior art, the main objective of this invention is to provide a method for preparing a transition metal polyatomic catalyst supported on carbon nitride. This method proposes a pre-locked-nano confined polymerization technique. First, metal atoms are pre-locked through the coordination of metal salts with hydrothermally treated dicyandiamide nanoribbons, suppressing metal site migration and aggregation during high-temperature polymerization. Then, polymerization kinetics are controlled within the nano-confined space to achieve self-assembly of polyatomic active centers, solving the problems of low loading and uncontrollable polyatomic configuration in traditional single-atom catalysts.
[0005] Another object of the present invention is to provide a transition metal polyatom catalyst supported on carbon nitride, which is prepared by the method of preparing the transition metal polyatom catalyst supported on carbon nitride, and has a high loading capacity and can be used for a variety of photocatalytic reactions.
[0006] Another object of the present invention is to provide the application of the transition metal polyatomic catalyst supported on the carbon nitride in photocatalytic reactions.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] In a first aspect, this invention provides a method for preparing a transition metal polyatomic catalyst supported on carbon nitride. The method employs a pre-locked-nano confined polymerization technique, firstly subjecting a dicyandiamide precursor to hydrothermal treatment to obtain hydrothermally treated dicyandiamide nanoribbons, then pre-locking metal atoms through coordination between a transition metal salt and the hydrothermally treated dicyandiamide nanoribbons to suppress metal site migration and aggregation during high-temperature polymerization, and finally performing self-assembly of polyatomic active centers within the nano-confined space. Specifically, the method includes the following steps:
[0009] (1) Synthesis of hydrothermal treated dicyandiamide nanoribbons: Dicyandiamide was added to deionized water and ultrasonically treated for 10-30 min to form a homogeneous solution; the homogeneous solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 160-220 °C for 2-6 h; the solution after reaction was immediately immersed in liquid nitrogen for rapid cooling and freeze-drying to obtain hydrothermal treated dicyandiamide nanoribbons solid;
[0010] (2) Synthesis of transition metal-hydrothermal treated dicyandiamide nanoribbons: The hydrothermal treated dicyandiamide nanoribbon solid was added to deionized water, ultrasonically treated for 10-30 min to form a uniform suspension, a transition metal salt solution was added, stirred for 10-30 min, and then immersed in liquid nitrogen for rapid cooling and freeze drying to obtain the transition metal-hydrothermal treated dicyandiamide nanoribbon solid.
[0011] (3) Synthesis of transition metal polyatomic catalyst: The transition metal-hydrothermal treated dicyandiamide nanoribbon solid was heated to 500-600 ℃ and held for 2-6 h at a heating rate of 1-5 ℃ / min under argon protection to obtain a transition metal polyatomic catalyst supported on carbon nitride.
[0012] Preferably, in step (1), the hydrothermally treated dicyandiamide nanoribbons are rich in urea bonds (having carbonyl C=O and amino NH groups). x One-dimensional fibrous nanostructures (functional groups).
[0013] Preferably, in step (1), the mass-to-volume ratio of dicyandiamide to deionized water is 0.5-1:12.5-25 g / mL.
[0014] Preferably, in step (2), the transition metal is selected from one or more of iron, cobalt, and nickel.
[0015] Preferably, in step (2), the transition metal salt is selected from one or more of ferric chloride, ferric sulfate, ferric nitrate, cobalt chloride, cobalt sulfate, cobalt nitrate, nickel chloride, nickel sulfate, and nickel nitrate.
[0016] Preferably, in step (2), the concentration of the transition metal salt solution is 1.5-20 mmol / L.
[0017] In the preparation method of the transition metal polyatom catalyst supported on carbon nitride of the present invention, firstly, the dicyandiamide precursor is subjected to hydrothermal treatment to obtain hydrothermally treated dicyandiamide nanoribbons, which are rich in urea bonds (having carbonyl C=O and amino NH groups). x One-dimensional fibrous nanostructures (functional groups) are formed; subsequently, transition metal ions undergo a biuret-like reaction with hydrothermally treated dicyandiamide nanoribbons, and the transition metal ions are coordinated and stabilized with urea bonds in the one-dimensional fibrous nanostructure; finally, during calcination, the one-dimensional fibrous nanostructure restricts the migration rate of transition metal sites, and multi-atom transition metal sites are formed instead of aggregating to form clusters or nanoparticles.
[0018] In a second aspect, the present invention provides a transition metal polyatom catalyst supported on carbon nitride, which is prepared by a method for preparing the transition metal polyatom catalyst supported on carbon nitride.
[0019] Preferably, the transition metal polyatomic catalyst supported on the carbon nitride has a high loading amount, wherein the transition metal loading amount is 25-40 wt%, more preferably 30-35 wt%, and the transition metal sites are uniformly dispersed in the support in atomic form, rather than forming nanoparticles or clusters.
[0020] Preferably, the transition metal polyatomic catalyst supported on the carbon nitride has a low transition metal-nitrogen coordination number (MN). x (x < 3), the coordination configuration of multiple transition metal atoms is linear diatomic or triangular triatomic, and the interatomic spacing of the metal atoms is 2-3 Å.
[0021] Preferably, the transition metal polyatomic catalyst supported on the carbon nitride has optimized light absorption performance, with an absorption range from the visible light region to the near-infrared region.
[0022] A third aspect of the invention provides the application of the transition metal polyatomic catalyst supported on the carbon nitride in photocatalytic reactions.
[0023] Preferably, the photocatalytic reaction includes photocatalytic water splitting, photocatalytic carbon dioxide reduction, photocatalytic urea synthesis, and photocatalytic pollutant degradation.
[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0025] I. This invention utilizes the "pre-locked-nano confined polymerization" technology to regulate precursor coordination and confined polymerization kinetics, fully leveraging the triangular cavities in the carbon nitride structure to achieve breakthrough ultra-high loading (above 30 wt%) and precise configuration control of transition metal polyatomic catalysts. This solves the problems of low loading (<3 wt%) and uncontrollable polyatomic configuration of traditional single-atom catalysts, providing a universally applicable method for the synthesis of transition metal polyatomic catalysts such as iron, cobalt, and nickel.
[0026] II. The transition metal polyatomic catalyst supported on carbon nitride of the present invention was confirmed by synchrotron radiation and aberration-corrected transmission electron microscopy to have a triangular configuration with an interatomic spacing of 0.2-0.3 nm and a low coordination environment (MN). x (x < 3) can enhance the synergistic effect between metal atoms and significantly improve catalytic activity. Compared with traditional carbon nitride materials, this catalyst expands the light absorption range to a wider range through the regulation of the electronic structure of metal atoms, showing application potential in multiple photocatalytic fields and providing high-performance materials that can be prepared on a large scale for photocatalysis, electrocatalysis and energy catalysis.
[0027] Third, taking the triangular triferroic atom catalyst synthesized in this invention as an example, carbon dioxide and ammonia water are used as carbon source and nitrogen source, respectively. The catalyst achieves highly efficient catalysis of the conversion of carbon dioxide and ammonia water into urea under simulated sunlight, with a yield of 457 µmolg⁻¹ h⁻¹, which is significantly better than the traditional single / dual atom catalytic system and has broad application prospects. Attached Figure Description
[0028] Figure 1 This is a scanning electron microscope image of the hydrothermal precursor nanoribbons in Example 1.
[0029] Figure 2 The image shows the Fourier transform infrared spectrum of the hydrothermal precursor nanoribbons in Example 1.
[0030] Figure 3 This is an X-ray diffraction image of the cobalt polyatomic catalyst in Example 1.
[0031] Figure 4 The result is the fitting result of the Fourier transform extended X-ray absorption fine structure of the cobalt polyatomic catalyst in Example 1.
[0032] Figure 5 The UV-Vis diffuse reflectance curves are those of the cobalt polyatomic catalyst and conventional carbon nitride in Example 1.
[0033] Figure 6 This is an X-ray diffraction image of the nickel polyatomic catalyst in Example 2.
[0034] Figure 7The result is the fitting result of the Fourier transform extended X-ray absorption fine structure of the nickel polyatomic catalyst in Example 2.
[0035] Figure 8 The UV-Vis diffuse reflectance curves are those of the nickel polyatomic catalyst and conventional carbon nitride in Example 2.
[0036] Figure 9 This is an X-ray diffraction image of the iron polyatomic catalyst in Example 3.
[0037] Figure 10 The result is the fitting result of the Fourier transform extended X-ray absorption fine structure of the iron polyatomic catalyst in Example 3.
[0038] Figure 11 The UV-Vis diffuse reflectance curves are those of the iron polyatomic catalyst and conventional carbon nitride in Example 3.
[0039] Figure 12 The image shows the UV-Vis absorption spectrum of the urea product after the photocatalytic coupling reaction of carbon dioxide and ammonia water using the iron polyatomic catalyst in Example 3. Detailed Implementation
[0040] To more fully understand and demonstrate the technical solutions, objectives, and advantages of the present invention, the technical effects produced by the present invention will be further described in detail and completely below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. It should be noted that other embodiments obtained by those skilled in the art without departing from the concept of the present invention are all within the protection scope of the present invention.
[0041] Example 1
[0042] This embodiment proposes a method for synthesizing a cobalt polyatom catalyst supported on carbon nitride, the specific steps of which are as follows:
[0043] (1) Synthesis of hydrothermal dicyandiamide nanoribbons: 0.50 g of dicyandiamide was added to 12.5 mL of deionized water and ultrasonically treated for 30 min to form a homogeneous solution. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 200 °C for 4 h. The solution after reaction was immediately immersed in liquid nitrogen for rapid cooling and then freeze-dried to remove moisture, resulting in a white solid hydrothermal dicyandiamide nanoribbon.
[0044] (2) Synthesis of cobalt-hydrothermal-treated dicyandiamide nanoribbons: Hydrothermal-treated dicyandiamide nanoribbons were added to 20 mL of deionized water and sonicated for 30 min to form a uniform suspension. 20 mmol / L cobalt chloride solution was added and stirred for 30 min. After rapid liquid nitrogen cooling and freeze drying, cobalt-hydrothermal-treated dicyandiamide nanoribbons solid was obtained.
[0045] (3) Synthesis of cobalt polyatomic catalyst: Under argon protection, the temperature was increased to 550 °C at a heating rate of 1 °C / min and held for 4 h.
[0046] Figure 1 and 2 The images shown are scanning electron microscope (SEM) images and Fourier transform infrared (FTIR) images of the hydrothermally treated dicyandiamide nanoribbons white solid synthesized in step (1) above. The characterization of the cobalt polyatomic catalyst supported on carbon nitride synthesized in this embodiment is as follows: Figure 3-5 As shown, from Figure 3 The X-ray diffraction pattern shows that no diffraction peaks associated with elemental cobalt or cobalt oxides were observed, proving that no cobalt sites aggregated during the synthesis of the cobalt polyatomic catalyst. Figure 4 The fitting results of the Fourier transform extended X-ray absorption fine structure show that the coordination numbers of Co-Co and Co-N are 2.02 and 1.05, respectively, proving the existence of linear coordination diatomic structures. Figure 5 The UV-Vis diffuse reflectance curves show that, compared to carbon nitride, the absorption edge of cobalt polyatoms is extended to a higher wavenumber, resulting in a wider absorption range.
[0047] Example 2
[0048] This embodiment proposes a method for synthesizing a nickel polyatom catalyst supported on carbon nitride, the specific steps of which are as follows:
[0049] (1) Synthesis of hydrothermal dicyandiamide nanoribbons: 0.50 g of dicyandiamide was added to 12.5 mL of deionized water and ultrasonically treated for 30 min to form a homogeneous solution. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 200 °C for 4 h. The solution after reaction was immediately immersed in liquid nitrogen for rapid cooling and then freeze-dried to remove moisture, resulting in a white solid hydrothermal dicyandiamide nanoribbon.
[0050] (2) Synthesis of nickel-hydrothermal-treated dicyandiamide nanoribbons: Hydrothermal-treated dicyandiamide nanoribbons were added to 20 mL of deionized water and sonicated for 30 min to form a uniform suspension. 20 mmol / L nickel chloride solution was added and stirred for 30 min. After rapid liquid nitrogen cooling and freeze drying, nickel-hydrothermal-treated dicyandiamide nanoribbon solid product was obtained.
[0051] (3) Synthesis of nickel polyatomic catalyst: Under argon protection, the temperature was raised to 550 °C at a rate of 1 °C / min and held for 4 h.
[0052] The characterization of the nickel polyatom catalyst supported on carbon nitride synthesized in this embodiment is as follows: Figure 6-8 As shown, from Figure 6The X-ray diffraction pattern shows that no diffraction peaks associated with elemental nickel or nickel oxides were observed, proving that no nickel site aggregation occurred during the synthesis of the nickel polyatomic catalyst. Figure 7 The fitting results of the Fourier transform extended X-ray absorption fine structure show that the coordination numbers of Ni-Ni and Ni-N are 1.97 and 1.29, respectively, proving the existence of linear coordination configuration diatoms. Figure 8 The UV-Vis diffuse reflectance curves show that, compared to carbon nitride, the absorption edge of cobalt polyatoms is extended to a higher wavenumber, resulting in a wider absorption range.
[0053] Example 3
[0054] This embodiment proposes a method for synthesizing an iron polyatomic catalyst supported on carbon nitride, the specific steps of which are as follows:
[0055] (1) Synthesis of hydrothermal dicyandiamide nanoribbons: 0.50 g of dicyandiamide was added to 12.5 mL of deionized water and ultrasonically treated for 30 min to form a homogeneous solution. The solution was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 200 °C for 4 h. The solution after reaction was immediately immersed in liquid nitrogen for rapid cooling and then freeze-dried to remove moisture, resulting in a white solid hydrothermal dicyandiamide nanoribbon.
[0056] (2) Synthesis of iron-hydrothermal-treated dicyandiamide nanoribbons: The hydrothermally-treated dicyandiamide nanoribbons were added to 20 mL of deionized water and sonicated for 30 min to form a uniform suspension. Then, 20 mmol / L ferric chloride solution was added and stirred for 30 min. After rapid liquid nitrogen cooling and freeze drying, iron-hydrothermal-treated dicyandiamide nanoribbons solids were obtained.
[0057] (3) Synthesis of iron polyatomic catalyst: Under argon protection, the temperature was increased to 550 °C at a heating rate of 1 °C / min and held for 4 h.
[0058] The characterization of the iron polyatomic catalyst supported on carbon nitride synthesized in this embodiment is as follows: Figure 9-11 As shown, from Figure 9 The X-ray diffraction pattern shows that no diffraction peaks associated with elemental iron or iron oxides were observed, proving that no iron site aggregation occurred during the synthesis of the iron polyatomic catalyst. Figure 10 The fitting results of the Fourier transform extended X-ray absorption fine structure show that the coordination numbers of Fe-Fe and Fe-N are 2.07 and 1.75, respectively, proving the existence of triatomic trigonal coordination configurations. Figure 11 The UV-Vis diffuse reflectance curves show that, compared to carbon nitride, the absorption edge of iron polyatoms is extended to a higher wavenumber, resulting in a wider absorption range.
[0059] Example 4
[0060] This embodiment uses the iron polyatom catalyst supported on carbon nitride synthesized in Example 3 to perform photocatalytic coupling of carbon dioxide and ammonia to prepare urea. The specific steps are as follows:
[0061] 4 mg of the iron polyatomic catalyst supported on carbon nitride synthesized in Example 3 was dispersed in 20 mL of deionized water containing 2 M concentrated ammonia under continuous stirring at 500 rpm. After continuously purging CO2 gas for 1 h to replace the air in the reactor under stirring conditions, the reaction was carried out under full-spectrum irradiation with a 300 W xenon lamp at 25 °C for 2 h to obtain urea product.
[0062] The detection method for urea products is as follows: Take 1 mL of reaction solution, add 1 mL of diacetyl-oxime-thiourea solution, then add 2 mL of mixed ferric acid solution, heat in a boiling water bath for 10 minutes, cool in water for 2 minutes, use pure water as a reference, and measure the absorbance value of each tube at 520 nm using a cuvette. Prepare a standard curve using the concentration control absorbance value, determine the urea content, and obtain the ultraviolet-visible absorption spectrum as shown below. Figure 12 As shown.
[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a transition metal polyatomic catalyst supported on carbon nitride, characterized in that, A pre-locked-nano confined polymerization technique is employed. First, a dicyandiamide precursor is hydrothermally treated to obtain hydrothermally treated dicyandiamide nanoribbons. Then, metal atoms are pre-locked through coordination between a transition metal salt and the hydrothermally treated dicyandiamide nanoribbons, inhibiting metal site migration and aggregation during high-temperature polymerization. Finally, multi-atom active centers self-assemble within the nano-confined space. The process includes the following steps: (1) Synthesis of hydrothermal treated dicyandiamide nanoribbons: Dicyandiamide was added to deionized water and ultrasonically treated for 10-30 min to form a homogeneous solution; the homogeneous solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 160-220 °C for 2-6 h; the solution after reaction was immediately immersed in liquid nitrogen for rapid cooling and freeze-drying to obtain hydrothermal treated dicyandiamide nanoribbons solid; (2) Synthesis of transition metal-hydrothermal treated dicyandiamide nanoribbons: The hydrothermal treated dicyandiamide nanoribbon solid was added to deionized water, ultrasonically treated for 10-30 min to form a uniform suspension, a transition metal salt solution was added, stirred for 10-30 min, and then immersed in liquid nitrogen for rapid cooling and freeze drying to obtain the transition metal-hydrothermal treated dicyandiamide nanoribbon solid. (3) Synthesis of transition metal polyatomic catalyst: The transition metal-hydrothermal treated dicyandiamide nanoribbon solid was heated to 500-600 ℃ and held for 2-6 h at a heating rate of 1-5 ℃ / min under argon protection to obtain a transition metal polyatomic catalyst supported on carbon nitride.
2. The method for preparing the transition metal polyatom catalyst supported on carbon nitride according to claim 1, characterized in that, In step (1), the hydrothermally treated dicyandiamide nanoribbons are one-dimensional fibrous nanostructures rich in urea bonds; And / or the mass-to-volume ratio of the dicyandiamide to deionized water is 0.5-1:12.5-25 g / mL.
3. The method for preparing the transition metal polyatom catalyst supported on carbon nitride according to claim 1, characterized in that, In step (2), the transition metal is selected from one or more of iron, cobalt, and nickel; The transition metal salt is selected from one or more of ferric chloride, ferric sulfate, ferric nitrate, cobalt chloride, cobalt sulfate, cobalt nitrate, nickel chloride, nickel sulfate, and nickel nitrate.
4. The method for preparing the transition metal polyatom catalyst supported on carbon nitride according to claim 1, characterized in that, In step (2), the concentration of the transition metal salt solution is 1.5-20 mmol / L.
5. A transition metal polyatom catalyst supported on carbon nitride, characterized in that, The catalyst was prepared by the method described in any one of claims 1 to 4 for the preparation of a transition metal polyatomic catalyst supported on carbon nitride.
6. The transition metal polyatom catalyst supported on carbon nitride according to claim 5, characterized in that, The transition metal polyatomic catalyst has a transition metal loading of 25-40 wt%, and the transition metal is uniformly dispersed in the support in atomic form.
7. The transition metal polyatom catalyst supported on carbon nitride according to claim 5, characterized in that, The transition metal-nitrogen coordination number in the transition metal polyatomic catalyst satisfies MN. x And x < 3, the coordination configuration of multiple transition metal atoms is linear diatomic or triangular triatomic, and the interatomic spacing is 2-3 Å.
8. The transition metal polyatom catalyst supported on carbon nitride according to claim 5, characterized in that, The light absorption range of the transition metal polyatomic catalyst is from the visible light region to the near-infrared region.
9. The application of the transition metal polyatomic catalyst supported on carbon nitride as described in any one of claims 5-8 in photocatalytic reactions.
10. The application according to claim 9, characterized in that, The photocatalytic reactions include photocatalytic water splitting, photocatalytic carbon dioxide reduction, photocatalytic urea synthesis, and photocatalytic pollutant degradation.