Zinc oxide nanotube array film photocatalyst and preparation method and use thereof

Abstract

This invention discloses a zinc oxide nanotube array thin-film photocatalyst, its preparation method, and its applications. The zinc oxide nanotube array photocatalyst uses a zinc target as raw material, argon as a protective gas, and oxygen as the working gas. Zinc oxide seed crystals are prepared using laser pulse deposition, and then further growth of the zinc oxide seed crystals is promoted by a hydrothermal method to obtain the zinc oxide nanotube photocatalyst. The final prepared zinc oxide photocatalyst has a three-dimensional tubular structure. This method solves the problem of requiring a template in the traditional preparation of zinc oxide arrays. The zinc oxide nanotube photocatalyst prepared by the method of this invention exhibits excellent photocatalytic performance.

Description

Technical Field

[0001] This invention relates to a zinc oxide nanotube array thin film photocatalyst, its preparation method and application, and relates to the field of semiconductor thin film materials technology, specifically to the field of semiconductor photocatalyst materials technology. Background Technology

[0002] With technological advancements and rapid economic development, we also face major global challenges such as energy shortages and environmental pollution. How to maximize output while minimizing resource consumption, how to protect the environment to the greatest extent possible while developing resources, and how to utilize existing resources to develop new ones—these are questions we must carefully consider. We should rationally develop and utilize existing resources, and find new ways to acquire new resources and protect the environment.

[0003] Photocatalysis, centered on semiconductor materials, offers a novel approach to energy utilization and pollution control. Photocatalysis can utilize solar energy to split water and produce hydrogen, alleviating or partially solving the energy crisis. It can also degrade organic pollutants and reduce heavy metal ions, protecting soil and water resources and effectively improving our environment. Since Fujishima and Honda discovered the photoelectrochemical phenomenon of TiO2 splitting water to produce hydrogen in 1972, the photocatalytic performance of semiconductor materials has been extensively studied and applied. Research on TiO2 and ZnO has become one of the most active research areas in catalysis technology internationally. Because ZnO has a higher separation efficiency of photogenerated electrons and holes than TiO2, it is expected to have superior photocatalytic performance. ZnO possesses excellent characteristics such as high catalytic activity, stable chemical properties, low preparation cost, and non-toxicity, making it a research hotspot in the field of photocatalysis. Currently, zinc oxide catalysts are still some distance from large-scale industrial application, and as a photocatalyst, the photocatalytic activity of zinc oxide is directly related to factors such as morphology and crystal structure. Therefore, developing novel supported zinc oxide photocatalysts is essential.

[0004] However, the following problems exist in the preparation process of supported zinc oxide photocatalysts:

[0005] 1. Zinc oxide powder dispersed in solution and directly coated onto the substrate for loading has poor stability and will cause zinc oxide to fall off during use, resulting in extremely poor loading effect.

[0006] 2. Loading zinc oxide onto a substrate through coating to form a dense thin film reduces the specific surface area of ​​the zinc oxide catalyst, leading to a sharp decline in catalytic performance.

[0007] 3. Traditional methods for preparing array catalysts require the use of alumina as a template, upon which zinc oxide is deposited. The zinc oxide nanotubes formed can easily be destroyed during the etching of the template.

[0008] A search revealed that current methods for preparing zinc oxide nanotubes, such as the one disclosed in patent CN107988586A, involve the following steps: placing a porous polycarbonate membrane in the reaction chamber of an atomic layer deposition (ALD) apparatus; then introducing diethylzinc carried by an inert gas and water as gaseous precursors into the reaction chamber; chemically adsorbing and reacting zinc oxide onto the porous polycarbonate membrane substrate; grinding to remove the zinc oxide from the surface of the polycarbonate membrane substrate; and finally dissolving and removing the polycarbonate membrane substrate using dichloromethane solvent to obtain zinc oxide nanotubes. This method requires the use of toxic dichloromethane as a cleaning agent, which is environmentally unfriendly, and the resulting nanotubes are not loaded, hindering recycling. Patent CN101348931 employs a three-electrode system for square-wave pulse electrodeposition, using a conductive glass coated with a ZnO film as the working electrode and a zinc chloride and potassium chloride solution as the electrolyte to perform square-wave pulse electrodeposition of ZnO, thus obtaining a zinc oxide nanorod array. This technology is limited to depositing zinc oxide on a conductive substrate. In CN108640147A, a seed layer is deposited on the surface and inside the pores of a flexible porous membrane using atomic layer deposition. Then, the porous membrane is polished and etched using a plasma cleaner to obtain zinc oxide nanotubes. This method requires grinding away a large amount of zinc oxide and etching the porous membrane, which easily leads to material waste, and the nanotube structure may be damaged during the polishing process. In CN101456579A, a seed layer is first prepared by spin coating and annealing or by directly sputtering a zinc oxide seed layer on the substrate using magnetron sputtering. Then, a zinc oxide nanowire array is prepared by low-temperature hydrothermal reaction of zinc salt and alkaline solution. Finally, the substrate with zinc oxide nanowires is placed in ethylenediamine alkaline solution for hydrothermal etching to obtain a zinc oxide nanotube array. This method has many steps, and the final alkaline etching step is not easy to control, resulting in an unstable morphology and structure of the nanotubes. In particular, seed crystals deposited at low temperatures on PET substrates by magnetron sputtering have poor crystallinity and orientation. Then, nanotubes are grown by self-assembly through hydrothermal reaction, resulting in a loose structure that is easy to detach.

[0009] This invention utilizes pulsed laser deposition to deposit zinc oxide seed crystals on a substrate under heating conditions. The seed crystals are of high quality, have strong adhesion to the substrate, and offer a wide range of substrate options. The resulting nanotube array structure, formed by hydrothermal reaction and self-growing, is stable and well-supported. Furthermore, the tubular structure facilitates the transport of photogenerated electrons and holes, further ensuring the photocatalytic performance of the catalyst. Summary of the Invention

[0010] One of the objectives of this invention is to address the problems of difficult catalyst recovery, high cost of zinc oxide powder loading, and structural control in the current field of zinc oxide nanoparticle photocatalysis. This invention proposes a preparation strategy that induces the regular and orderly deposition of zinc oxide in the hydrothermal reaction by constructing a zinc oxide seed layer on the substrate surface, thereby controlling the formation of a three-dimensional zinc oxide nanotube array film loaded on an FTO substrate.

[0011] The second objective of this invention is to provide applications for the aforementioned zinc oxide nanotube array thin film catalyst, which can be used in fields such as photocatalytic water splitting for hydrogen production under ultraviolet or visible light.

[0012] According to the present invention, preferably, the zinc oxide nanotube array thin film photocatalyst is a nanomaterial with a microstructure of a tightly packed three-dimensional nanotube array.

[0013] According to the present invention, the average diameter of the zinc oxide nanotube array film can be 10-1000 nm, preferably 100-600 nm.

[0014] According to the present invention, the thin-film catalyst has a molecular weight of 0.15-1.9 mmol / L. -2 h -1 The hydrogen production rate is preferably 1.05-1.9 mmol m -2 h -1 .

[0015] According to the present invention, the catalyst exhibits high photocatalytic performance, reaching 1.9 mmol m -2 h -1 It is 12.7 times that of zinc oxide seed crystals under the same conditions.

[0016] The present invention further provides a method for preparing the above-mentioned zinc oxide nanotube array thin film photocatalyst, the method comprising laser pulse deposition and hydrothermal method.

[0017] Specifically, the preparation method includes the following steps:

[0018] (1) Repeatedly clean and dry the FTO substrate to which the zinc oxide array film is to be deposited;

[0019] (2) The sample stage carrying the cleaned substrate and the zinc target to be sputtered are loaded into the cavity of the laser pulse deposition equipment, and the sputtering spacing is adjusted to be the distance between the sample stage and the target.

[0020] (3) Evacuate the vacuum, close the sample stage baffle, open the heating stage, introduce argon inert gas as the sputtering working atmosphere, oxygen as the reaction gas in the growth chamber of the laser pulse deposition system, turn on the laser, and pre-sputter the zinc target.

[0021] (4) Open the sample stage baffle, and continue sputtering the zinc target under the substrate heating condition to start the seed deposition of the zinc oxide thin film and prepare the seed crystal of the catalyst;

[0022] (5) Prepare a mixed solution of zinc nitrate and hexamethylenetetramine, stir it thoroughly, and then add it to a hydrothermal reactor;

[0023] (6) Place the FTO substrate loaded with zinc oxide seeds face down in a hydrothermal reactor to carry out the hydrothermal reaction;

[0024] (7) The zinc oxide array film obtained in the initial hydrothermal reaction was repeatedly washed with water and anhydrous ethanol;

[0025] (8) The cleaned membrane is calcined to obtain the thin-film catalyst for photocatalytic water splitting to produce hydrogen.

[0026] According to the present invention, in step (1), the substrate is an FTO sheet, preferably a high-purity FTO glass sheet.

[0027] According to the present invention, in step (2), the zinc metal target used is preferably a high-purity zinc target, and the distance between the sample stage and the target is 50-120 mm, for example 80 mm.

[0028] According to the present invention, in step (3), the argon gas used is preferably high-purity argon gas, the oxygen gas used is preferably high-purity oxygen gas, and the laser frequency of the pre-sputtered zinc target is 20Hz and the number of pulses is 1000.

[0029] According to the present invention, in step (4), during the thin film growth and deposition process, the laser frequency is 1-20Hz and the number of pulses is 100-5000. As an exemplary example, the laser frequency is 5Hz and the number of pulses is 3000.

[0030] According to the present invention, in step (5), the concentration of zinc nitrate and hexamethylenetetramine in the mixed solution is 0.05-1 mol / L, preferably 0.15 mol / L.

[0031] According to the present invention, in step (6), the hydrothermal reaction temperature is 80-200℃, preferably 100-150℃.

[0032] According to the present invention, in step (8), the calcination temperature is 350-450℃, preferably 400℃.

[0033] The present invention also provides the use of the photocatalyst material described above for photocatalysis, for example, for photocatalytic water splitting to produce hydrogen.

[0034] The zinc oxide nanoarray catalyst prepared by this invention has the following advantages compared with existing photocatalyst materials:

[0035] (1) The preparation method of the present invention is simple, the raw materials are inexpensive and readily available, and it is easy to produce on a large scale;

[0036] (2) Compared with traditional array preparation methods, this invention does not require the use of array templates, and the templates do not need to be etched away after the preparation process is completed, which reduces the generation of harmful waste liquids and is more environmentally friendly.

[0037] (3) Compared with other zinc oxide thin film catalysts, the tubular zinc oxide catalyst of the present invention has a higher specific surface area and a stronger photogenerated electron transport capability.

[0038] (4) Compared with other powdered zinc oxide catalyst materials, the tubular zinc oxide catalyst array film of the present invention is loaded on FTO glass, which makes it easy to recycle and reuse. Attached Figure Description

[0039] Figure 1 This is a SEM image of the seed layer of the ZnO nanotube array film S3 in Example 3;

[0040] Figure 2 This is a SEM image of the ZnO nanotube array film S3 in Example 3;

[0041] Figure 3 This is the XRD pattern of the ZnO nanotube array film S3 in Example 3;

[0042] Figure 4 The graphs show the relationship between hydrogen production and time for the photocatalytic water splitting of ZnO nanotube array films S1-S6 in Examples 1-6 and ZnO seed film S0 in the comparative example. Detailed Implementation

[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by this invention.

[0044] The present invention will be described in detail through the following embodiments. However, those skilled in the art will understand that the following embodiments are not intended to limit the scope of protection of the present invention. Any improvements and variations made based on the present invention are within the scope of protection of the present invention.

[0045] Unless otherwise stated, all raw materials and reagents used in the examples are commercially available substances.

[0046] Comparative Example 1

[0047] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7 After torsion, open the gate valve to connect the sample inlet and growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁶. -8 The heating temperature was set to 250℃. The oxygen flow meter was turned on, and the gas partial pressure was adjusted to 40%. The argon flow meter was turned on, and the gas partial pressure was adjusted to 60%. The system operating pressure was adjusted to 50 Torr. The substrate baffle was closed, the target rotation speed was set to 60 rpm, the laser energy was adjusted to 150 J, the number of pulses was set to 1000, and the pulse frequency was set to 20 Hz. The laser was turned on, and pre-sputtering of the zinc target was initiated to remove surface adsorbed contaminants. Then, the substrate baffle was turned on, and the number of pulses was set to 3000, and the pulse frequency was set to 5 Hz. The laser was turned on, and the deposition of a zinc oxide seed layer on the substrate began. The entire growth and deposition process was carried out under the set temperature conditions. The sample was named S0 as a comparative example.

[0048] Example 1

[0049] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7 After torsion, open the gate valve to connect the sample inlet and growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁶. -8The heating temperature was set to 250℃. The oxygen flow meter was turned on, and the gas partial pressure was adjusted to 40%. The argon flow meter was turned on, and the gas partial pressure was adjusted to 60%. The system operating pressure was adjusted to 50 Torr. The substrate baffle was closed, the target rotation speed was set to 60 rpm, the laser energy was adjusted to 150 J, the number of pulses was set to 1000, and the pulse frequency was set to 20 Hz. The laser was turned on to begin pre-sputtering the zinc target to remove surface contaminants. Then the substrate baffle was turned on, and the number of pulses was set to 3000, and the pulse frequency was set to 5 Hz. The laser was turned on to begin depositing a zinc oxide seed layer on the substrate. The entire growth and deposition process was carried out under the set temperature conditions. A zinc oxide seed film prepared by laser pulse deposition was placed face down in a mixed solution of 0.15 mol / L zinc nitrate and 0.15 mol / L hexamethylenetetramine with 70 mL added. The film was hydrothermally reacted at 80 °C for 12 hours to grow a self-assembled zinc oxide nanotube array film. The hydrothermally prepared film was repeatedly rinsed with distilled water and ethanol. The dried film was calcined at 400 °C for 2 hours to obtain the zinc oxide nanotube array film, named S1.

[0050] The array of thin films was used as a photocatalyst to conduct tests on photocatalytic water splitting for hydrogen production.

[0051] Example 2

[0052] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7 After torsion, open the gate valve to connect the sample inlet and growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁶. -8The heating temperature was set to 250℃. The oxygen flow meter was turned on, and the gas partial pressure was adjusted to 40%. The argon flow meter was turned on, and the gas partial pressure was adjusted to 60%. The system operating pressure was adjusted to 50 Torr. The substrate baffle was closed, the target rotation speed was set to 60 rpm, the laser energy was adjusted to 150 J, the number of pulses was set to 1000, and the pulse frequency was set to 20 Hz. The laser was turned on to begin pre-sputtering the zinc target to remove surface contaminants. Then the substrate baffle was turned on, and the number of pulses was set to 3000, and the pulse frequency was set to 5 Hz. The laser was turned on to begin depositing a zinc oxide seed layer on the substrate. The entire growth and deposition process was carried out under the set temperature conditions. A zinc oxide seed film prepared by laser pulse deposition was placed face down in a mixed solution of 0.15 mol / L zinc nitrate and 0.15 mol / L hexamethylenetetramine with 70 mL added. The film was hydrothermally reacted at 100 °C for 12 hours to grow a self-assembled zinc oxide nanotube array film. The hydrothermally prepared film was repeatedly rinsed with distilled water and ethanol. The dried film was calcined at 400 °C for 2 hours to obtain the zinc oxide nanotube array film, named S2.

[0053] The array of thin films was used as a photocatalyst to conduct tests on photocatalytic water splitting for hydrogen production.

[0054] Example 3

[0055] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7 After torsion, open the gate valve to connect the sample inlet and growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁶. -8The heating temperature was set to 250℃. The oxygen flow meter was turned on, and the gas partial pressure was adjusted to 40%. The argon flow meter was turned on, and the gas partial pressure was adjusted to 60%. The system operating pressure was adjusted to 50 Torr. The substrate baffle was closed, the target rotation speed was set to 60 rpm, the laser energy was adjusted to 150 J, the number of pulses was set to 1000, and the pulse frequency was set to 20 Hz. The laser was turned on to begin pre-sputtering the zinc target to remove surface contaminants. Then the substrate baffle was turned on, and the number of pulses was set to 3000, and the pulse frequency was set to 5 Hz. The laser was turned on to begin depositing a zinc oxide seed layer on the substrate. The entire growth and deposition process was carried out under the set temperature conditions. A zinc oxide seed film prepared by laser pulse deposition was placed face down in a mixed solution of 0.15 mol / L zinc nitrate and 0.15 mol / L hexamethylenetetramine with 70 mL added. The film was hydrothermally reacted at 120 °C for 12 hours to grow a self-assembled zinc oxide nanotube array film. The hydrothermally prepared film was repeatedly rinsed with distilled water and ethanol. The dried film was calcined at 400 °C for 2 hours to obtain the zinc oxide nanotube array film, named S3.

[0056] The array of thin films was used as a photocatalyst to conduct tests on photocatalytic water splitting for hydrogen production.

[0057] Example 4

[0058] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7After Torr, open the gate valve to connect the sample inlet chamber and the growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁸ Torr. Set the heating temperature to 250℃. Turn on the oxygen flow meter and adjust the gas partial pressure to 40%. Turn on the argon flow meter and adjust the gas partial pressure to 60%. Adjust the system working pressure to 50 Torr. Close the substrate baffle, set the target rotation speed to 60 rpm, and adjust the laser energy to 150 J, pulse count to 1000, and pulse frequency to 20 Hz. Turn on the laser and begin pre-sputtering the zinc target to remove surface contaminants. Then open the substrate baffle, set the pulse count to 3000, and pulse frequency to 5 Hz. Turn on the laser and begin depositing a zinc oxide seed layer on the substrate. The entire growth and deposition process is performed under the set temperature conditions. A zinc oxide seed film prepared by laser pulse deposition was placed face down in a mixed solution of 0.15 mol / L zinc nitrate and 0.15 mol / L hexamethylenetetramine with 70 mL added. The film was hydrothermally reacted at 150 °C for 12 hours to grow a self-assembled zinc oxide nanotube array film. The hydrothermally prepared film was repeatedly rinsed with distilled water and ethanol. The dried film was calcined at 400 °C for 2 hours to obtain the zinc oxide nanotube array film, named S4.

[0059] The array of thin films was used as a photocatalyst to conduct tests on photocatalytic water splitting for hydrogen production.

[0060] Example 5

[0061] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7 After torsion, open the gate valve to connect the sample inlet and growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁶. -8The heating temperature was set to 250℃. The oxygen flow meter was turned on, and the gas partial pressure was adjusted to 40%. The argon flow meter was turned on, and the gas partial pressure was adjusted to 60%. The system operating pressure was adjusted to 50 Torr. The substrate baffle was closed, the target rotation speed was set to 60 rpm, the laser energy was adjusted to 150 J, the number of pulses was set to 1000, and the pulse frequency was set to 20 Hz. The laser was turned on to begin pre-sputtering the zinc target to remove surface contaminants. Then the substrate baffle was turned on, and the number of pulses was set to 3000, and the pulse frequency was set to 5 Hz. The laser was turned on to begin depositing a zinc oxide seed layer on the substrate. The entire growth and deposition process was carried out under the set temperature conditions. A zinc oxide seed film prepared by laser pulse deposition was placed face down in a mixed solution of 0.15 mol / L zinc nitrate and 0.15 mol / L hexamethylenetetramine with 70 mL added. The film was hydrothermally reacted at 120 °C for 16 hours to grow a self-assembled zinc oxide nanotube array film. The hydrothermally prepared film was repeatedly rinsed with distilled water and ethanol. The dried film was calcined at 400 °C for 2 hours to obtain the zinc oxide nanotube array film, named S5.

[0062] The array of thin films was used as a photocatalyst to conduct tests on photocatalytic water splitting for hydrogen production.

[0063] Example 6

[0064] The FTO glass slide was repeatedly cleaned three times with deionized water, ethanol, and acetone, then purged and dried with nitrogen to prepare it as a substrate. The substrate was fixed onto the sample stage with silver paste and cured using an infrared lamp. Argon gas was introduced into the sample chamber of the pulsed laser deposition system until the pressure reached atmospheric pressure. The sample stage was then placed on the sample feed rod inside the sample chamber, and a vacuum was drawn to 1.0*10⁻⁶. -7 After torsion, open the gate valve to connect the sample inlet and growth chamber. Slowly place the sample stage into the growth chamber using the sample delivery rod, approximately 80 mm from the target. Close the gate valve and continue evacuating to 1.0 × 10⁻⁶. -8The heating temperature was set to 250℃. The oxygen flow meter was turned on, and the gas partial pressure was adjusted to 40%. The argon flow meter was turned on, and the gas partial pressure was adjusted to 60%. The system operating pressure was adjusted to 50 Torr. The substrate baffle was closed, the target rotation speed was set to 60 rpm, the laser energy was adjusted to 150 J, the number of pulses was set to 1000, and the pulse frequency was set to 20 Hz. The laser was turned on to begin pre-sputtering the zinc target to remove surface contaminants. Then the substrate baffle was turned on, and the number of pulses was set to 3000, and the pulse frequency was set to 5 Hz. The laser was turned on to begin depositing a zinc oxide seed layer on the substrate. The entire growth and deposition process was carried out under the set temperature conditions. A zinc oxide seed film prepared by laser pulse deposition was placed face down in a mixed solution of 0.15 mol / L zinc nitrate and 0.15 mol / L hexamethylenetetramine with 70 mL added. The film was hydrothermally reacted at 120 °C for 8 hours to grow a self-assembled zinc oxide nanotube array film. The hydrothermally prepared film was repeatedly rinsed with distilled water and ethanol. The dried film was calcined at 400 °C for 2 hours to obtain the zinc oxide nanotube array film, named S6.

[0065] The array of thin films was used as a photocatalyst to conduct tests on photocatalytic water splitting for hydrogen production.

[0066] in, Figure 1 This is a SEM image of the seed layer of the ZnO thin film S3 in Example 3; Figure 2 This is a SEM image of the ZnO nanotube array film S3 in Example 3; Figure 3 This is the XRD pattern of the ZnO nanotube array film S3 in Example 3; Figure 4 The graphs show the relationship between hydrogen production and time for the photocatalytic water splitting of ZnO nanotube array films S1-S6 in Examples 1-6 and ZnO seed film S0 in the comparative example.

[0067] From the above figures, we can see that: Figure 1 This demonstrates that zinc oxide seed crystals (S0) were successfully deposited using the laser pulse method. The seed layer has a dense structure, strong adhesion, and high quality. Figure 2 This demonstrates that after the hydrothermal reaction in Example 3, a zinc oxide array film S3 was successfully self-assembled. This film catalyst is composed of tightly packed, uniformly oriented three-dimensional tubular zinc oxide. Figure 3 The results indicate that the S3 zinc oxide sample has a hexagonal phase structure, and the XRD pattern shows that there are no other peaks except for the FTO backside peak on the substrate, indicating that the synthesized S3 nanotube array has high purity and no other impurities. Figure 4 This demonstrates that the photocatalytic performance of the S1-S6 nanotube array samples in each embodiment is significantly higher than that of the comparative thin film S0, with S3 exhibiting the best performance and a hydrogen production rate of 1.9 mmol / L. -2 h -1 .

[0068] The zinc oxide catalysts prepared in the comparative examples and Examples 1-6 were used to test the performance of photocatalytic water splitting for hydrogen production.

[0069] The zinc oxide array film was placed face up in the photocatalytic reactor, an aqueous solution containing 10% methanol sacrificial agent was added, nitrogen gas was introduced for 30 minutes to purge the air, and a 300W xenon lamp was turned on to irradiate the photocatalytic reactor. Samples were taken at regular intervals, and the hydrogen production was tested by gas chromatography.

[0070] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The use of a zinc oxide nanotube array thin film photocatalyst, characterized in that, The zinc oxide nanotube array thin-film photocatalyst is used for photocatalytic hydrogen production. The thin-film photocatalyst is composed of tightly packed, uniformly oriented three-dimensional tubular zinc oxide, with a single tube diameter of 10-1000 nm, a tube wall thickness of 1-200 nm, and a film thickness of 0.5-5 μm. The preparation method of the zinc oxide nanotube array thin-film photocatalyst includes the following steps: (1) Clean and dry the FTO substrate; (2) The sample stage carrying the cleaned FTO substrate and the zinc target to be sputtered are loaded into the growth chamber of the laser pulse deposition system, and the distance between the sample stage and the target gun is adjusted. (3) Evacuate the vacuum, close the sample stage baffle, open the heating stage, introduce argon inert gas into the growth chamber as the sputtering working atmosphere, oxygen as the reaction gas of the laser pulse deposition system, turn on the laser, pre-sputter the zinc target, after pre-sputtering, open the sample stage baffle, continue sputtering the zinc target under the substrate heating condition, start the seed deposition of the zinc oxide thin film, and prepare the seed of the catalyst; (4) Prepare a mixed solution of zinc nitrate and hexamethylenetetramine, stir it thoroughly, and add it to a hydrothermal reactor. Place the FTO substrate loaded with zinc oxide seeds face down in the hydrothermal reactor and carry out the hydrothermal reaction. (5) The zinc oxide array film obtained by the hydrothermal reaction was repeatedly washed with water and anhydrous ethanol; (6) The cleaned membrane is calcined to obtain the thin-film catalyst for photocatalytic water splitting to produce hydrogen; In step (3), the growth chamber pressure is 50 Torr, the oxygen partial pressure is 20%-80%, the argon partial pressure is 80%-20%, the laser energy is 100-300 mJ, the sputtering frequency is 1-20 Hz, the sample stage is kept rotating uniformly during the deposition process to ensure uniform deposition of zinc oxide seeds, and the deposition temperature is 200℃-500℃. In step (4), the concentrations of the zinc nitrate solution and the hexamethylenetetramine solution are 0.05-1 mol / L, the hydrothermal reaction temperature is 80-200℃, and the reaction time is 2-48 h; In step (6), the calcination temperature is 350-450℃ and the calcination time is 0.5-4h.

2. The use of the zinc oxide nanotube array thin film photocatalyst according to claim 1, characterized in that, In step (1), the FTO substrate is an FTO glass sheet.

3. The use of the zinc oxide nanotube array thin film photocatalyst according to claim 1, characterized in that, In step (2), the distance between the sample stage and the target is 50-120 mm.

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