A thermoplasmon@COF composite photocatalyst, its preparation method and application

Abstract

The present invention provides a thermoplasmon@COF composite photocatalyst, a preparation method thereof and applications, belonging to the technical field of photocatalytic hydrogen production. The thermoplasmon@COF composite photocatalyst of the present invention is composed of a thermoplasmon nanostructured material and a covalent organic framework COF, and has the ability to efficiently drive photocatalytic hydrogen production. The internal mechanism of this photocatalyst is plasmon-driven enhanced absorption, near-field-driven exciton separation, hot electron injection, and local thermal effects. Among them, the local thermal effect plays a dominant role in catalytic hydrogen production, enabling this photocatalyst to exhibit excellent activity and stability at room temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic hydrogen production, and particularly to a thermoplasmon@COF composite photocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Photocatalytic hydrogen production is a clean energy technology that uses semiconductor materials to absorb solar energy and decompose water into hydrogen and oxygen, and has the advantages of energy conservation, environmental protection, and renewable energy. However, currently commonly used traditional wide-bandgap semiconductor photocatalysts, such as TiO2, etc., usually can only utilize ultraviolet light or near-ultraviolet light (only accounting for about 5% of the solar radiation energy) due to their energy band limitations, resulting in low photocatalytic efficiency. Therefore, developing efficient photocatalysts that can be driven by visible light or near-infrared light is an important goal in this field.

[0003] Plasmonic photocatalysis is a method that uses the localized surface plasmon resonance (LSPR) effect of plasmonic nanoparticles (PNPs) to enhance traditional semiconductor photocatalysis. LSPR refers to when PNPs strongly interact with incident light, the surface electrons generate strong collective oscillations, and high-energy hot electrons and local thermal effects are generated through non-radiative decay. Compared with traditional semiconductor photocatalysts, the advantage of plasmonic photocatalysis is that it can effectively utilize the visible and near-infrared light energy of sunlight, and use mechanisms such as LSPR-mediated enhanced light absorption and scattering, electromagnetic near-field enhancement, hot electron injection, and local thermal effects to significantly improve the photocatalytic efficiency and selectivity. In the field of photocatalytic water splitting for hydrogen production, forming plasmonic composite photocatalysts by combining PNPs with semiconductor materials, such as Au / TiO2, Ag / CdS, etc., has become an effective strategy to improve the photocatalytic hydrogen production efficiency.

[0004] However, the existing plasmonic photocatalysts still face the following challenges:

[0005] On the one hand, the existing plasmonic photocatalysts usually need to use noble metals such as Au, Ag, Pd, etc. or rare earth materials, which increases the material cost and environmental impact, and limits their feasibility in large-scale production applications.

[0006] On the other hand, the existing plasmonic photocatalysts usually aim at the hot electron injection mechanism to improve the photocatalytic performance, but are limited by the low injection efficiency and low lifetime of hot electrons, resulting in limited performance improvement.

[0007] To address these issues, current research directions include developing new bimetallic or non-noble metal plasmonic materials such as Cu, Al, Fe, etc., optimizing the morphology, size, and distribution of NPs, designing suitable semiconductor substrates and interfacial structures, and exploring new hot electron transport and capture mechanisms, etc. However, there are still few that can meet practical requirements.

[0008] In addition to the hot electron injection mechanism, the plasmonic local heating effect is another important mechanism that can enhance photocatalytic performance. The non-radiative decay of LSPR can generate a large amount of heat localized on the surface of NPs and transfer it to the surrounding medium and reactants. This can significantly increase the activity and reaction rate of the reactants, thereby enhancing the photocatalytic reaction. Taking advantage of the plasmonic local heating effect, it is theoretically possible to achieve efficient hydrogen production by water splitting at room temperature. Compared with noble metal plasmonic materials, thermoplasmonic materials are characterized by having a larger imaginary part of their complex dielectric constant, resulting in faster decay of LSPR into heat, and thus having a wider absorption bandwidth and photothermal conversion efficiency. Common thermoplasmonic materials include transition metal nitrides such as TiN, ZrN, and non-noble metal materials such as Al, Cu, etc. They can more effectively convert incident light into heat energy and accelerate the charge transfer between the semiconductor substrate and water molecules, thereby promoting the dissociation of water molecules and the generation of hydrogen.

[0009] In view of this, the present invention will utilize the advantages of thermoplasmonic materials to achieve a plasmonic photothermal catalyst that can achieve efficient photocatalytic hydrogen production at room temperature and has cheap raw materials to address the challenges faced by current plasmonic photocatalysts. Summary of the Invention

[0010] The purpose of the present invention is to provide a thermoplasmon@COF composite photocatalyst and its preparation method and application to solve the above technical problems existing in the existing plasmonic photocatalysts.

[0011] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0012] The present invention provides a preparation method of a thermoplasmon@COF composite photocatalyst, comprising the following steps:

[0013] 1) Mix thermoplasmonic nanostructured materials in a solvent to obtain a thermoplasmonic colloidal solution;

[0014] 2) Mix the COF synthesis precursor in the thermoplasmonic colloidal solution for a solvothermal reaction to obtain a thermoplasmon@COF composite;

[0015] 3) Wash and dry the thermoplasmon@COF composite successively to obtain a thermoplasmon@COF core-shell structured composite photocatalyst.

[0016] Furthermore, the mass-volume ratio of the plasmonic nanostructured material to the solvent is 0.3 - 3 mg: 1 - 3 mL.

[0017] Furthermore, the solvent comprises one or more of ethanol, ethylene glycol, methanol, acetone, and dimethyl sulfoxide.

[0018] Furthermore, the plasmonic nanostructured material is one or more of transition metal nitrides, non-noble metal materials, heavily doped semiconductor materials, and MXene materials;

[0019] The transition metal nitride comprises TiN powder or ZrN powder, the non-noble metal material comprises nano-copper or nano-aluminum, the heavily doped semiconductor material comprises Cu2S, and the MXene material comprises Ti3C2.

[0020] Furthermore, the COF synthesis precursor is an aromatic structure compound with topological symmetry, and the mass ratio of the plasmonic nanostructured material to the COFs is 1% - 30%.

[0021] Furthermore, the solvothermal reaction is carried out under catalysis, and the catalyst comprises acetic acid, p-toluenesulfonic acid, potassium hydroxide, sodium hydroxide, or quaternary ammonium salt;

[0022] The temperature of the solvothermal reaction is 60 - 150 °C, and the reaction time is 12 - 72 h.

[0023] The present invention provides a plasmonic@COF core-shell structure composite photocatalyst.

[0024] The present invention also provides an application of the plasmonic@COF core-shell structure composite photocatalyst in the water splitting hydrogen production reaction. After mixing the plasmonic@COF core-shell structure composite photocatalyst and water, hydrogen gas generated is collected under the irradiation of a simulated solar light source.

[0025] Advantages of the present invention:

[0026] The present invention uses plasmonic materials such as TiN or Ti3C2 with abundant elemental reserves and low cost, instead of common noble metals or rare earth elements. Taking TiN as an example, it has strong plasmon resonance characteristics in the visible and near-infrared light ranges, can effectively convert incident light into local thermal effects, thereby reducing the reaction energy barrier and improving the catalytic performance. In addition, TiN also has advantages such as high conductivity, high hardness, high corrosion resistance, and high thermal stability, which are particularly suitable for subsequent large-scale applications.

[0027] The present invention provides a novel structure and combination method for developing new high-performance photocatalytic materials, that is, a thermoplasmonic nanostructure is combined with a covalent organic framework (COF) to form a thermoplasmonic photocatalyst. This structure and combination method can effectively utilize the mechanism of thermoplasmonic enhanced photocatalytic performance and the structural and performance advantages of COF materials. The COF material is porous and has low thermal conductivity, which can enrich reaction substrates and provide reaction sites; moreover, its low thermal conductivity can prevent the heat mediated by thermoplasmonic nanoparticles from diffusing around, better localize the heat on the catalyst surface, and thus further improve the catalytic performance.

[0028] The present invention provides a novel explanation and control method for revealing the thermoplasmonic photocatalytic mechanism, that is, plasmon-driven enhanced absorption, near-field-driven exciton separation, hot electron injection, and local thermal effect. This mechanism can not only clearly explain the roles and influences of thermoplasmonics in each step of the photocatalytic reaction process, but also realize the regulation of the resonance characteristics of thermoplasmonics and the local surface temperature by adjusting factors such as temperature, light intensity, and wavelength, thereby achieving the regulation of the photocatalytic reaction rate and selectivity.

[0029] The present invention provides a novel method for decomposing water into clean energy hydrogen using solar energy, that is, using a thermoplasmonic@COF composite photocatalyst to carry out water splitting hydrogen production reaction under visible light and infrared light. This method can not only effectively utilize the light sources in a relatively wide wavelength range of solar energy, but also exhibit excellent activity and stability at room temperature. This method uses inexpensive and abundant materials, and the preparation process is simple and controllable, suitable for large-scale production and application. This method provides a novel solution for solving energy crises and environmental problems. Brief Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the structure and preparation process of the thermoplasmonic photocatalyst of TiN@COF composite in Example 1 of the present invention;

[0031] Figure 2 It is the transmission electron microscope (TEM) and scanning electron microscope (SEM) images of the thermoplasmonic photocatalyst of TiN@COF composite in Example 1 of the present invention;

[0032] Figure 3 It is the X-ray diffraction (XRD) and 77K nitrogen adsorption analysis results of the thermoplasmonic photocatalyst of TiN@COF composite in Example 1 of the present invention;

[0033] Figure 4Fourier infrared spectrum (a), ultraviolet-visible spectrum (b), photoluminescence spectrum (c), luminescence lifetime (d), photocurrent (e) and impedance spectrum (f) curves of the TiN@COF composite plasmonic photocatalyst of Example 1 of the present invention;

[0034] Figure 5 Photothermal conversion performance curve (a and b), water decomposition hydrogen production rate curve (c) and relationship diagram between input optical power density and hydrogen production rate (d) of the TiN@COF composite plasmonic photocatalyst of Example 1 of the present invention. Detailed implementation mode

[0035] The present invention provides a preparation method of a plasmon@COF composite photocatalyst, comprising the following steps:

[0036] 1) Mix the plasmonic nanostructured material in a solvent to obtain a plasmonic colloidal solution;

[0037] 2) Mix the COF synthesis precursor in the TiN colloidal solution for a solvothermal reaction to obtain a plasmon@COF composite;

[0038] 3) Wash and dry the plasmon@COF composite in sequence to obtain a plasmon@COF core-shell structured composite photocatalyst.

[0039] In the present invention, the mass-volume ratio of the plasmonic nanostructured material to the solvent is 0.3-3 mg: 1-3 mL, preferably 0.5-2.5 mg: 1.5-2.5 mL, and more preferably 1-2 mg: 2 mL.

[0040] In the present invention, the solvent comprises one or more of ethanol, ethylene glycol, methanol, acetone and dimethyl sulfoxide, preferably one or more of ethanol, ethylene glycol and methanol, and more preferably ethanol.

[0041] In the present invention, the plasmonic nanostructured material has unique dielectric properties, the real part of its dielectric is negative in the visible-near infrared range, and at the same time it has a larger imaginary part value of the dielectric compared with noble metal plasmonic materials.

[0042] In the present invention, the plasmonic nanostructured material is one or more of transition metal nitrides, non-noble metal materials, heavily doped semiconductor materials and MXene materials.

[0043] In the present invention, the transition metal nitride is preferably TiN powder or ZrN powder, the non-noble metal material is preferably nano copper or nano aluminum, the heavily doped semiconductor material is preferably Cu2S, and the MXene material is preferably Ti3C2.

[0044] In the present invention, different plasmonic nanostructured materials are selected to achieve thermoplasmonic resonance absorption and photocatalytic activity in different wavelength ranges.

[0045] In the present invention, based on the advantages of the thermoplasmon@COF core-shell structured composite catalyst, the COF material is porous and has low thermal conductivity, which can enrich the reaction substrates and increase the reaction sites; moreover, its low thermal conductivity can hinder the diffusion of heat mediated by the thermoplasmonic nanoparticles to the surroundings, better localize the heat on the catalyst surface, and thus further improve the catalytic performance.

[0046] In the present invention, the COF synthesis precursor is an aromatic structure compound with topological symmetry, preferably 1,3,5-benzenetricarbaldehyde, phloroglucinol, and benzidine diamine.

[0047] In the present invention, the mass ratio of the plasmonic nanostructured material to the COFs is 1% to 30%, preferably 2% to 25%, further preferably 5% to 20%, and more preferably 10% to 15%.

[0048] In the present invention, the solvothermal reaction is carried out under the catalysis of a catalyst, and the catalyst includes acetic acid, p-toluenesulfonic acid, potassium hydroxide, sodium hydroxide, or quaternary ammonium salt, preferably acetic acid.

[0049] In the present invention, the temperature of the solvothermal reaction is 60 to 150 °C, preferably 80 to 100 °C, and further preferably 85 °C; the reaction time is 12 to 72 h, preferably 48 to 70 h, and further preferably 50 to 60 h.

[0050] The present invention provides a thermoplasmon@COF composite photocatalyst.

[0051] The present invention also provides an application of the thermoplasmon@COF composite photocatalyst in the water splitting hydrogen production reaction. After mixing the thermoplasmon@COF composite photocatalyst and water, the generated hydrogen is collected under the irradiation of a simulated solar light source.

[0052] In the present invention, the light source includes visible light or infrared light, preferably visible light.

[0053] In the present invention, the mass-volume ratio of the thermoplasmon@COF core-shell structured composite photocatalyst to water is 1 to 10 mg: 10 to 50 mL, preferably 5 mg: 20 mL.

[0054] In the present invention, the thermoplasmon@COF core-shell structured composite photocatalyst and water are mixed at room temperature.

[0055] The technical solutions provided by the present invention are described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present invention.

[0056] Example 1

[0057] Weigh 2.4 mg of TiN powder and 1 mL of ethanol and place them in a reactor. Continuously ultrasonically disperse for 2 h to prepare a TiN colloidal solution. Subsequently, add 12.95 mg of mesotriformylphloroglucinol, 17.05 mg of benzidine diamine, catalytically metered acetic acid, and 2 mL of ethanol solvent to the reactor, and ultrasonically disperse again for 0.5 h to uniformly disperse the TFP-BD precursor powder. Finally, place the reactor in a water-cooling device, evacuate to 5 mbr. After 1 h, take out the reactor, restore to room temperature, and then place it in an oil bath. Heat at 80 °C for three days to obtain the TiN@COF composite photocatalyst.

[0058] Example 2

[0059] Weigh 0.5 mg of TiN powder and 1 mL of ethanol and place them in a reactor. Continuously ultrasonically disperse for 1 h to prepare a TiN colloidal solution. Subsequently, add 11.53 mg of mesotriformylphloroglucinol, 16.08 mg of benzidine diamine, catalytically metered acetic acid, and 2 mL of ethanol solvent to the reactor, and ultrasonically disperse again for 0.5 h to uniformly disperse the TFP-BD precursor powder. Finally, place the reactor in a water-cooling device, evacuate to 10 mbr. After 1 h, take out the reactor, restore to room temperature, and then place it in an oil bath. Heat at 85 °C for three days to obtain the TiN@COF composite photocatalyst.

[0060] Example 3

[0061] Weigh 3 mg of TiN powder and 1 mL of ethanol and place them in a reactor. Continuously ultrasonically disperse for 2 h to prepare a TiN colloidal solution. Subsequently, add 14 mg of mesotriformylphloroglucinol, 17.5 mg of benzidine diamine, catalytically metered acetic acid, and 2 mL of ethanol solvent to the reactor, and ultrasonically disperse again for 1 h to uniformly disperse the TFP-BD precursor powder. Finally, place the reactor in a water-cooling device, evacuate to 5 mbr. After 1 h, take out the reactor, restore to room temperature, and then place it in an oil bath. Heat at 90 °C for three days to obtain the TiN@COF composite photocatalyst.

[0062] Figure 1 It is a schematic diagram of the structure and preparation process of the TiN@COF composite photothermal catalyst prepared in the examples. The microstructure of the TiN@COF composite photocatalyst obtained in Example 1 was characterized, and the results are as Figure 2 shown. The figure shows the transmission electron microscope (TEM), scanning electron microscope (SEM), and elemental distribution images of the composite photothermal catalyst, clearly indicating that TiN particles are uniformly distributed in the COF multi-level structure ( Figure 2 a - b), and the COF layer is relatively uniformly coated around the TiN particles, forming a composite thermoplasmonic photocatalyst with a stable core-shell structure ( Figure 2 c - d);

[0063] Figure 3 X-ray diffraction (XRD) and 77K nitrogen adsorption analysis results of the TiN@COF composite photothermal catalyst prepared in the examples. It can be seen from the figure that the COF in the composite photocatalyst maintains good crystallinity ( Figure 3 a), and maintains a stable and good porous structure ( Figure 3 b), and its pore size is mainly distributed in 1-2 nm ( Figure 3 c);

[0064] Figure 4 are the Fourier transform infrared spectroscopy (a), ultraviolet-visible spectroscopy (b), photoluminescence spectroscopy (c), luminescence lifetime (d), photocurrent (e) and impedance spectroscopy (f) curves of the TiN@COF composite photothermal catalyst prepared in the examples. It can be seen from the figure that compared with the intrinsic COFs, the composite photothermal catalyst broadens and enhances the light absorption performance ( Figure 4 b), promotes the separation of photoexcited excitons ( Figure 4 c), prolongs the lifetime of photoelectrons ( Figure 4 d), enhances the photocurrent ( Figure 4 e), and simultaneously improves the exciton migration ( Figure 4 f).

[0065] Application Example

[0066] Add 5 mg of the plasmon@COF core-shell structured composite photocatalyst prepared in Example 1 to 20 mL of water, mix at room temperature, and collect the generated hydrogen under the irradiation of a simulated solar xenon lamp. The result diagram is as shown in Figure 5 shown. It can be seen from the figure that the introduction of the plasmonic TiN nanomaterial significantly improves the photothermal conversion performance of the COFs ( Figure 5 a-b), and increases the hydrogen evolution rate of the intrinsic COFs by 7 times (Figure c). And Figure 5 the exponential dependence of the hydrogen production amount on the incident light power density in d conforms to the Arrhenius empirical formula (the relationship between the chemical reaction rate constant and temperature), indicating that the local thermal effect mediated by the TiN plasmon and the COF-coated core-shell structure dominates the catalytic hydrogen production reaction.

[0067] As can be seen from the above examples, the present invention provides a plasmon@COF composite photocatalyst and its preparation method and application. The test results show that the plasmonic TiN nanoparticles extend the absorption spectrum of the COFs, improve the exciton separation efficiency, and endow the catalyst with significant photothermal conversion performance. In addition, the relatively low thermal conductivity of the COFs material inhibits the dissipation of the local thermal field of the TiN to the reaction solution, causing a large amount of heat to accumulate on the catalyst surface. Photocatalytic hydrogen production shows that the TiN@COFs has good photocatalytic hydrogen evolution performance, and the hydrogen production rate is 37.0 mmol·g -1· hour -1 The introduction of TiN increased the hydrogen production rate of the intrinsic COFs by 7 times, and it was experimentally demonstrated that the plasmon-mediated local thermal effect dominated the enhancement of the catalytic hydrogen production performance of COFs.

[0068] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a thermoplasmon@COF composite photocatalyst, characterized in that It includes the following steps: 1) Mix the plasmonic nanostructured material in a solvent to obtain a plasmonic colloidal solution; 2) Mix the COF synthesis precursor in the plasmonic colloidal solution for solvothermal reaction to obtain a plasmon@COF composite; 3) Wash and dry the plasmon@COF composite successively to obtain a plasmon@COF composite photocatalyst; The plasmonic nanostructured material is one or more of transition metal nitrides, non-noble metal materials, heavily doped semiconductor materials, and MXene materials; The transition metal nitride includes TiN powder or ZrN powder, the non-noble metal material includes nano-copper or nano-aluminum, the heavily doped semiconductor material includes Cu2S, and the MXene material includes Ti3C2; The COF synthesis precursor is an aromatic structure compound with topological symmetry, and the mass ratio of the plasmonic nanostructured material to COF is 1% - 30%; 2. The preparation method according to claim 1, wherein The mass-volume ratio of the plasmonic nanostructured material to the solvent is 0.3 - 3 mg: 1 - 3 mL; 3. The preparation method according to claim 1 or 2, characterized in that, The solvent includes one or more of ethanol, ethylene glycol, methanol, acetone, and dimethyl sulfoxide; 4. The preparation method according to claim 3, characterized in that, The solvothermal reaction is carried out under the catalysis of a catalyst, and the catalyst includes acetic acid, p-toluenesulfonic acid, potassium hydroxide, sodium hydroxide, or quaternary ammonium salt; The temperature of the solvothermal reaction is 60 - 150 °C, and the reaction time is 12 - 72 h.

5. The plasmon@COF composite photocatalyst obtained by the preparation method according to any one of claims 1 - 4.

6. Use of the plasmon@COF composite photocatalyst according to claim 5 in a water splitting hydrogen production reaction, characterized in that Mix the plasmon@COF core-shell structured composite photocatalyst and water, and collect the generated hydrogen under the irradiation of a simulated solar light source.

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