Plasmon enhancement mechanism-based high-efficiency photocatalytic water splitting hydrogen production material and preparation method thereof

Abstract

The invention relates to an efficient photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism and a preparation method of the efficient photocatalytic water splitting hydrogen production material. The material is characterized in that a porous TiO2 nanotube array is used as a matrix, the tube diameter is 50-200 nm, and the wall thickness is 10-50 nm; au-Ag bimetallic nano-particles with the particle size of 5-20 nm are loaded on the surface, the molar ratio of Au to Ag is 1: 3-3: 1, and the Au-Ag bimetallic nano-particles are used for exciting the surface plasmon resonance effect; further depositing a two-dimensional MoS2 nanosheet as a co-catalyst on the outer surface, wherein the thickness of the two-dimensional MoS2 nanosheet is 1-5nm; and an ultrathin carbon layer with the thickness of 1-3nm is deposited on the whole surface so as to improve light absorption and stability. The invention further provides a preparation method of the photocatalytic material. The preparation method sequentially comprises the steps of TiO2 anodic oxidation, MoS2 hydrothermal deposition, metal nanoparticle photodeposition, CVD carbon layer coating and the like. The prepared material shows excellent hydrogen yield and stability under the driving of sunlight, and has a wide application prospect of photocatalytic hydrogen production.

Description

Technical Field

[0001] The present invention relates to the field of new energy materials and photocatalytic technology, and specifically to a high-efficiency photocatalytic water decomposition hydrogen production material based on a plasmon enhancement mechanism and a preparation method thereof. Background Art

[0002] As the global energy structure accelerates its transition toward a low-carbon economy, hydrogen, with its high energy density and zero carbon emissions, has become a key area of ​​clean energy development. Solar-driven photocatalytic water splitting is considered one of the most promising green hydrogen production methods. This technology directly utilizes renewable light to excite semiconductor photocatalysts, reducing water molecules to produce clean hydrogen, offering the dual advantages of environmental friendliness and resource sustainability.

[0003] Currently, traditional photocatalytic materials are primarily based on wide-bandgap semiconductors such as TiO2, ZnO, and g-C3N4. These materials exhibit strong absorption and stability in the ultraviolet region. However, their weak absorption of visible light and the easy recombination of photogenerated electron-hole pairs result in low overall photocatalytic efficiency, making them difficult to meet practical application requirements. To improve their utilization in the visible light region, researchers have attempted to introduce noble metals (such as Au and Ag) into semiconductor systems. By stimulating the surface plasmon resonance (LSPR) effect, they enhance the local electromagnetic field and inject high-energy electrons, thereby broadening the absorption band and improving carrier transfer efficiency. Furthermore, the introduction of two-dimensional materials (such as MoS2) as co-catalysts can effectively reduce the overpotential of the hydrogen evolution reaction and promote electron transfer. Constructing multi-level heterojunction structures is also an important strategy for improving photocatalytic performance. They can promote spatial separation of electrons and holes between different components, inhibit recombination, and improve quantum efficiency. To further improve material stability and light absorption efficiency, some studies have attempted to coat the composite materials with carbon layers to enhance conductivity and structural protection.

[0004] Although existing research has made progress in various directions, it still faces the following challenges: First, the uneven distribution or agglomeration of metal particles makes it difficult to fully stimulate the LSPR effect; second, poor coupling at multiphase interfaces leads to blocked carrier transfer paths; third, poor material stability and easy degradation under long-term light exposure; and fourth, most systems have complex architectures and the preparation process is not conducive to scalability. Therefore, it is urgent to develop a photocatalytic composite material with a reasonable structure, synergistic components, a wide response, high stability, and a simple preparation process to improve the efficiency of hydrogen production driven by solar energy and its industrial applicability.

[0005] Based on the above problems, the present invention proposes a high-efficiency photocatalytic water decomposition and hydrogen production material based on the plasmon enhancement mechanism. By constructing a porous TiO2 nanotube array as a supporting skeleton, loading Au-Ag alloy nanoparticles to trigger the LSPR effect, depositing MoS2 nanosheets to construct a heterojunction to promote electron transfer, and at the same time coating an ultra-thin carbon layer on the surface to enhance light absorption and stability, the overall design has a significant synergistic effect, effectively solving the technical bottlenecks of traditional catalysts in terms of light response range, electron recombination rate and long-term stability. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-efficiency photocatalytic water decomposition hydrogen production material and a preparation method based on a plasmon enhancement mechanism to solve the problems raised by the above background technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a highly efficient photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism, characterized in that the material comprises:

[0008] The porous TiO2 nanotube array is used as the matrix, wherein the nanotube has a diameter of 50 to 200 nm, a wall thickness of 10 to 50 nm, a tube length of 1 to 10 μm, an anatase crystal structure and a specific surface area of ​​100 to 300 m 2 / g;

[0009] Au-Ag bimetallic nanoparticles are uniformly loaded on the inner and outer wall surfaces of the TiO2 nanotubes, wherein the nanoparticles have a particle size of 5 to 20 nm and a molar ratio of Au to Ag of 1:3 to 3:1, forming a localized surface plasmon resonance enhancement system;

[0010] Two-dimensional MoS2 nanosheets deposited on the outer wall of the TiO2 nanotubes act as co-catalysts, with a MoS2 thickness of 1 to 5 nm and a lateral size of 10 to 50 nm, used to construct heterojunctions to promote photogenerated electron transfer;

[0011] The ultra-thin carbon layer covering the surface of the composite material has a thickness of 1 to 3 nm and a coverage of 80% to 95%, and is used to enhance light absorption capacity, interface stability and oxidation resistance.

[0012] As a preferred technical solution of the present invention, the Au-Ag bimetallic nanoparticles are deposited on the surface of the TiO2 nanotubes by optical deposition, and the ultraviolet light wavelength used in the deposition process is 300-400nm and the light intensity is 50-100mW / cm 2 , the sedimentation time is 30 to 60 minutes, and the solution pH value is 3 to 5.

[0013] As a preferred technical solution of the present invention, the TiO2 nanotube array is prepared by an anodic oxidation method, using an ethylene glycol electrolyte containing 0.3-0.7wt% NH4F and 0.1-0.5wt% water, applying a voltage of 40-60V at 20-30°C for 2-4 hours, and annealing at 400-600°C for 1-3 hours to form an anatase structure. The resulting nanotube porosity is 30%-50%.

[0014] As a preferred technical solution of the present invention, the MoS2 nanosheets are deposited by a hydrothermal method, using a molar ratio of Na2MoO4 to thiourea of ​​1:2 to 1:4, a reaction temperature of 160-200°C, a reaction time of 6-12 hours, and a stirring speed of 100-300rpm.

[0015] As a preferred technical solution of the present invention, the carbon layer is formed by chemical vapor deposition (CVD), the carbon source is glucose or acetylene, the deposition temperature is 350-450°C, and the time is 20-40 minutes. The formed carbon layer is graphite carbon or amorphous carbon, and has a certain plasmon coupling enhancement effect.

[0016] The present invention also provides a method for preparing a high-efficiency photocatalytic water decomposition hydrogen production material based on a plasmon enhancement mechanism, comprising the following steps:

[0017] (a) A porous TiO2 nanotube array was formed on a titanium foil substrate by anodization and then heat treated to obtain anatase crystal form.

[0018] (b) The TiO2 nanotube array was immersed in a mixed precursor solution containing HAuCl4 and AgNO3, and a photodeposition reaction was carried out under ultraviolet light to form Au-Ag bimetallic nanoparticles;

[0019] (c) placing the obtained composite material in a reaction solution containing Na2MoO4 and thiourea to perform a hydrothermal reaction to grow MoS2 nanosheets;

[0020] (d) Glucose or acetylene gas is introduced by CVD method and pyrolyzed under inert atmosphere to form an ultrathin carbon layer of 1 to 3 nm.

[0021] As a preferred technical solution of the present invention, the electrolyte in step (a) is an ethylene glycol system containing 0.4wt% NH4F and 0.3wt% water, the anodic oxidation temperature is controlled at 25±2°C, and the electrolysis time is 3 hours.

[0022] As a preferred technical solution of the present invention, in step (b), the total concentration of the bimetallic precursor is 0.01-0.05 mol / L, the molar ratio of Au to Ag is controlled to be 2:1, and uniform deposition of nanoparticles is achieved through uniform stirring and controlled light reaction.

[0023] As a preferred technical solution of the present invention, the carbon layer formed in step (d) uniformly covers the surface of the material, effectively improving its interface contact performance and resistance to light corrosion, and the optical absorption rate of the carbon layer is increased by 10% to 25% in the 400-800nm ​​band.

[0024] A high-efficiency photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism is used in solar-driven water splitting hydrogen production. Under AM 1.5G sunlight simulation conditions, the material has a hydrogen yield of 10 to 20 mmol / g·h, and the performance degradation rate does not exceed 5% after 100 hours of continuous operation, demonstrating excellent photocatalytic stability and practical application prospects.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention constructs a TiO2 nanotube array support structure and loads Au-Ag bimetallic nanoparticles on its surface to stimulate the localized surface plasmon resonance (LSPR) effect, significantly enhancing the material's absorption capacity in the 400–800nm ​​visible light band. Simultaneously, the introduction of MoS2 nanosheets forms a heterojunction between the TiO2 and the metal, effectively lowering the interfacial energy barrier and promoting the rapid transfer of photogenerated electrons and hole migration, achieving spatial separation of photogenerated carriers, reducing recombination, and improving quantum efficiency.

[0027] In the constructed quaternary composite structure, MoS2 acts as a highly conductive co-catalyst, which helps to reduce the overpotential of the hydrogen evolution reaction and accelerate the surface reaction kinetics. At the same time, the ultra-thin carbon layer on the surface has good conductivity and interface adhesion, which can construct additional electron migration paths and play a role in interface stabilization and protection, effectively inhibiting the agglomeration of metal particles and structural degradation, thereby enhancing the material's resistance to light corrosion while improving catalytic activity.

[0028] This method utilizes proven processes such as anodic oxidation, hydrothermal synthesis, photodeposition, and chemical vapor deposition. Its mild operating conditions and strong controllability facilitate mass production and make it suitable for industrial production. The resulting material achieves a hydrogen yield of up to 18 mmol / g·h under solar illumination, with performance degradation of less than 5% after 100 hours of continuous operation. This demonstrates excellent catalytic stability and long-term operability, promising broad application prospects and practical application value for photocatalytic hydrogen production. DETAILED DESCRIPTION

[0029] This invention provides a highly efficient photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism and its preparation method. By constructing a TiO2 nanotube array, loading it with Au-Ag bimetallic nanoparticles, introducing a MoS2 co-catalyst, and depositing an ultrathin carbon layer on the surface, the photocatalytic hydrogen production efficiency and material stability are synergistically improved. This is illustrated below with reference to specific examples.

[0030] Example 1: Preparation of photocatalytic material with Au:Ag=2:1 and glucose as carbon source;

[0031] (1) Preparation of TiO2 nanotube arrays: A titanium foil sheet of 10 cm × 2 cm × 0.05 cm was ultrasonically cleaned in deionized water, anhydrous ethanol, and acetone for 10 minutes, and then dried for later use.

[0032] It was used as the anode, and ethylene glycol containing 0.5 wt % NH4F and 0.2 wt % deionized water was used as the electrolyte. A constant voltage of 50 V was set, and anodization was carried out at 25° C. for 3 hours.

[0033] The oxidized titanium foil was rinsed with deionized water and annealed in air at 500 °C for 2 h to obtain anatase-structured TiO2 nanotube arrays (tube diameter of about 100 nm, wall thickness of 25 nm, length of about 5 μm, specific surface area of ​​210 m 2 / g).

[0034] (2) Loading of Au-Ag bimetallic nanoparticles: The above TiO2 array sample was immersed in a mixed ethanol solution of HAuCl4 and AgNO3, with the Au:Ag molar ratio controlled to be 2:1 and the total concentration to be 0.03 mol / L.

[0035] The solution pH was adjusted to 4, and photodeposition was performed under ultraviolet light of 365 nm wavelength for 45 minutes with a light intensity of 80 mW / cm 2 .

[0036] After the reaction, the sample was taken out, rinsed with ethanol and deionized water, and dried to form Au-Ag alloy nanoparticles with a particle size of about 10 nm, which were evenly distributed on the inner and outer wall surfaces of the TiO2 nanotubes.

[0037] (3) Deposition of MoS2 nanosheets:

[0038] The TiO2-Au-Ag composite material was placed in a 50 mL high-pressure reactor, and 25 mL of a mixed aqueous solution of Na2MoO4 and thiourea (molar ratio 1:3, concentrations of 10 mmol / L and 30 mmol / L, respectively) was added.

[0039] The reaction was carried out at 180°C for 8 hours. After the reaction was completed, the mixture was cooled to room temperature, washed repeatedly with deionized water and dried to obtain a composite structure with MoS2 nanosheets deposited with a thickness of about 3 nm.

[0040] (4) Deposition of ultrathin carbon layer: The dried composite sample was placed in a quartz boat in a CVD reactor. Under argon protection, glucose vapor was introduced as a carbon source. The sample was kept at 400°C for 30 minutes and then cooled naturally to form a graphite-like carbon layer with a thickness of 2 nm and a coverage of 90%.

[0041] Example 2: Preparation of photocatalytic material with Au:Ag=1:1 and glucose as carbon source;

[0042] This embodiment differs from Example 1 only in the molar ratio of the metal nanoparticles, and the remaining steps and conditions are basically the same:

[0043] (1) Preparation of TiO2 nanotubes: Same as Example 1.

[0044] (2) Au-Ag loading: HAuCl4 and AgNO3 were prepared into an ethanol solution with a total concentration of 0.03 mol / L in a 1:1 molar ratio, and the pH was adjusted to 4. The photodeposition conditions remained unchanged (ultraviolet light 365 nm, 80 mW / cm 2 , light irradiation for 45 minutes) to obtain Au-Ag alloy nanoparticles with a particle size of about 12 nm.

[0045] (3) MoS2 deposition: same as Example 1.

[0046] (4) Carbon layer deposition: Same as in Example 1, a carbon layer with a thickness of about 2 nm is formed.

[0047] Example 3: Preparation of photocatalytic material with Au:Ag=3:1 and acetylene as carbon source

[0048] This embodiment differs from the previous two embodiments in terms of metal ratio and carbon source type.

[0049] (1) Preparation of TiO2 nanotubes: Same as Example 1.

[0050] (2) Au-Ag loading: A mixed precursor solution with a molar ratio of Au:Ag of 3:1 and a concentration of 0.03 mol / L was used, the pH was adjusted to 4, and photodeposition was performed under a 365 nm UV light source for 40 min to form alloy particles with a higher proportion of Au and a size controlled at about 10 nm.

[0051] (3) MoS2 deposition: Same as the previous two cases, Na2MoO4 and thiourea solution with a molar ratio of 1:3 was used and reacted at 180℃ for 8 hours.

[0052] (4) Carbon layer deposition: The composite material was placed in a CVD quartz tube, argon was introduced for 20 minutes to replace the air, and then acetylene gas (flow rate 50 sccm) was introduced. The tube was kept at 350°C for 25 minutes to form an amorphous carbon layer with a thickness of 1.5 nm.

[0053] Comparative Example 1: TiO2 nanotube sample without composite modification;

[0054] Only TiO2 nanotube arrays were prepared without subsequent Au-Ag deposition, MoS2 introduction, and carbon coating:

[0055] (1) Preparation process: The titanium foil anodization conditions are the same as those in Example 1 to obtain a pure anatase TiO2 nanotube array.

[0056] (2) No metal particle loading, co-catalyst deposition or carbon layer coating was performed, and the product was directly used for subsequent photocatalytic performance testing.

[0057]

[0058] Effect analysis: Examples 1-3 are significantly better than Comparative Example 1 in terms of hydrogen production rate, quantum efficiency and stability, verifying the effectiveness of the plasmon enhancement mechanism and heterojunction synergistic effect.

[0059] Example 3 performed best, indicating that appropriately increasing the Au ratio and using acetylene as a carbon source are helpful in forming a denser conductive carbon layer and enhancing the LSPR effect.

[0060] In the comparative example, when TiO2 is used alone, the hydrogen production efficiency is extremely low, indicating that the composite structure is the key to achieving high performance.

[0061] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Highly efficient photocatalytic water splitting hydrogen production material based on plasmon enhancement mechanism, characterized by: The materials include: The porous TiO2 nanotube array is used as the matrix, wherein the nanotube has a diameter of 50 to 200 nm, a wall thickness of 10 to 50 nm, a tube length of 1 to 10 μm, an anatase crystal structure and a specific surface area of ​​100 to 300 m 2 / g; Au-Ag bimetallic nanoparticles are uniformly loaded on the inner and outer wall surfaces of the TiO2 nanotubes, wherein the nanoparticles have a particle size of 5 to 20 nm and a molar ratio of Au to Ag of 1:3 to 3:1, forming a localized surface plasmon resonance enhancement system; Two-dimensional MoS2 nanosheets deposited on the outer wall of the TiO2 nanotubes act as co-catalysts, with a MoS2 thickness of 1 to 5 nm and a lateral size of 10 to 50 nm, used to construct heterojunctions to promote photogenerated electron transfer; The ultra-thin carbon layer covering the surface of the composite material has a thickness of 1 to 3 nm and a coverage of 80% to 95%, and is used to enhance light absorption capacity, interface stability and oxidation resistance.

2. The high-efficiency photocatalytic water splitting hydrogen production material based on the plasmon enhancement mechanism according to claim 1, characterized in that: The Au-Ag bimetallic nanoparticles are deposited on the surface of the TiO2 nanotubes by photodeposition. The ultraviolet light wavelength used in the deposition process is 300-400nm and the light intensity is 50-100mW / cm 2 , the sedimentation time is 30 to 60 minutes, and the solution pH value is 3 to 5.

3. The high-efficiency photocatalytic water splitting hydrogen production material based on plasmon enhancement mechanism according to claim 1, characterized in that: The TiO2 nanotube array is prepared by an anodic oxidation method, using an ethylene glycol electrolyte containing 0.3-0.7 wt% NH4F and 0.1-0.5 wt% water, applying a voltage of 40-60 V at 20-30°C for 2-4 hours, and annealing at 400-600°C for 1-3 hours to form an anatase structure. The resulting nanotubes have a porosity of 30%-50%.

4. The high-efficiency photocatalytic water splitting hydrogen production material based on plasmon enhancement mechanism according to claim 1, characterized in that: The MoS2 nanosheets are deposited by a hydrothermal method, using a molar ratio of Na2MoO4 to thiourea of ​​1:2 to 1:4, a reaction temperature of 160-200°C, a reaction time of 6-12 hours, and a stirring speed of 100-300 rpm.

5. The high-efficiency photocatalytic water splitting hydrogen production material based on plasmon enhancement mechanism according to claim 1, characterized in that: The carbon layer is formed by chemical vapor deposition (CVD), the carbon source is glucose or acetylene, the deposition temperature is 350-450°C, and the time is 20-40 minutes. The formed carbon layer is graphite carbon or amorphous carbon, and has a certain plasmon coupling enhancement effect.

6. A method for preparing a high-efficiency photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism according to any one of claims 1 to 5, characterized in that: The following steps are involved: (a) A porous TiO2 nanotube array was formed on a titanium foil substrate by anodization and then heat treated to obtain anatase crystal form; (b) The TiO2 nanotube array was immersed in a mixed precursor solution containing HAuCl4 and AgNO3, and a photodeposition reaction was carried out under ultraviolet light to form Au-Ag bimetallic nanoparticles; (c) placing the obtained composite material in a reaction solution containing Na2MoO4 and thiourea to perform a hydrothermal reaction to grow MoS2 nanosheets; (d) Glucose or acetylene gas is introduced by CVD method and pyrolyzed under inert atmosphere to form an ultrathin carbon layer of 1 to 3 nm.

7. The method for preparing a high-efficiency photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism according to claim 6, characterized in that: In the step (a), the electrolyte is an ethylene glycol system containing 0.4 wt % NH 4 F and 0.3 wt % water, the anodic oxidation temperature is controlled at 25±2° C., and the electrolysis time is 3 hours.

8. The method for preparing a high-efficiency photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism according to claim 6, characterized in that: In the step (b), the total concentration of the bimetallic precursor is 0.01-0.05 mol / L, the molar ratio of Au to Ag is controlled to be 2:1, and uniform deposition of nanoparticles is achieved through uniform stirring and controlled light reaction.

9. The method for preparing a high-efficiency photocatalytic water splitting hydrogen production material based on a plasmon enhancement mechanism according to claim 6, characterized in that: The carbon layer formed in step (d) uniformly covers the surface of the material, effectively improving its interface contact performance and light corrosion resistance, and the optical absorption rate of the carbon layer is increased by 10% to 25% in the 400-800nm ​​band.

10. An application of the photocatalytic material according to any one of claims 1 to 5 in solar-driven water decomposition to produce hydrogen, characterized in that: Under AM 1.5G sunlight simulation conditions, the material has a hydrogen production rate of 10 to 20 mmol / g·h, and the performance decay rate does not exceed 5% after 100 hours of continuous operation, demonstrating excellent photocatalytic stability and practical application prospects.

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