Method for enhancing photocatalytic oxygen evolution reaction efficiency of nanorod array material through magnetic field

Abstract

The invention belongs to the technical field of photocatalytic water dissociation, and relates to a method for enhancing the photocatalytic oxygen evolution reaction efficiency of a nanorod array material through a magnetic field. According to the invention, ZnO nanorod arrays are placed at three relative positions of a cubic parallel uniform magnetic field with adjustable magnetic field intensity for photocatalytic OER. The constructed magnetic field regulation and control device is mainly composed of two parallel coils which are connected in series. The electromagnetic effect is generated through the coil, and rapid adjustment of the magnetic field is facilitated. And magnetic induction lines between the parallel coils connected in series are uniformly distributed in parallel, so that the direction of a magnetic field can be regulated and controlled. Due to the existence of the magnetic fields which are uniformly distributed in parallel among the parallel coils which are connected in series, photon-generated carriers moving in catalyst particles move in opposite directions under the action of Lorentz force. And photo-generated electrons (e-) and photo-generated holes (h +) are separated, so that the photocatalytic reaction efficiency is improved. Therefore, the magnetic field regulation and control device can meet the regulation and control of catalytic reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic water dissociation. More specifically, the present invention relates to a method for enhancing the efficiency of photocatalytic oxygen evolution reaction (OER) of a semiconductor nanorod array catalyst, wherein the semiconductor nanorod array catalyst is suitable for use as a catalyst for OER in a photocatalytic water dissociation reaction. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The separation and transfer efficiency of photogenerated carriers are important factors affecting the surface OER activity. In addition to constructing an internal electric field, introducing an external field is also a flexible and controllable strategy to effectively promote the separation and transfer of photogenerated carriers and improve the photocatalytic OER activity without changing the original properties of the catalyst.

[0004] The magnetic field is a type of clean, efficient and contactless external field. When the magnetic field is introduced into the photocatalytic process, the Lorentz force induced by the magnetic field separates electrons and holes in opposite directions, suppresses a large number of photogenerated carrier recombination, and allows more active carriers to transfer to the surface to participate in the photocatalytic reaction. Based on the Lorentz force formula F = qvBsinθ, the effect of the Lorentz force is affected by the direction and intensity of the magnetic field. Gao et al. studied the photocatalytic degradation efficiency of methyl orange by the synergistic effect of TiO2 magnetic field. Under the action of the magnetic field Lorentz force, the photocatalytic degradation efficiency can be increased by 26%. However, due to the three-dimensional structure of the particle catalyst, the photogenerated carriers are transferred unrestrictedly along the three-dimensional direction. This randomly oriented carrier transfer masks the effect of the magnetic field direction. Secondly, the particle catalyst in the solution is randomly dispersed. This random orientation of the particle catalyst further masks the effect of the magnetic field direction. Therefore, the magnetic field direction, this magnetic field vector effect, cannot work effectively for most particle photocatalysts. This makes it difficult to fully exert the enhancement effect caused by the magnetic field and it is difficult to efficiently improve the photocatalytic performance of semiconductors. Summary of the invention

[0005] In view of the lack of research on the above-mentioned magnetic field vector effect, which is difficult to work effectively, the present invention provides a method for enhancing the photocatalytic OER activity of Fe-ZnO nanorod arrays by vector magnetic field. The present invention uses a hydrothermal method to synthesize ZnO nanorod arrays and single-atom Fe-doped ZnO nanorod arrays. In order to perform magnetic field vector regulation, the present invention places the ZnO nanorod array in three relative positions of a cubic parallel uniform magnetic field with adjustable magnetic field strength (the angle between the radial direction of the ZnO nanorod and the direction of the magnetic field: 0°, 45°, 90°) for photocatalytic OER. The constructed magnetic field regulation device is mainly composed of two parallel coils connected in series. The electromagnetic effect is generated by the coil, which is conducive to the rapid adjustment of the magnetic field size. Secondly, the magnetic flux lines between the parallel coils in series are parallel and evenly distributed, which is conducive to the regulation of the direction of the magnetic field. Due to the existence of a parallel and evenly distributed magnetic field between the parallel coils in series, the photogenerated carriers moving inside the catalyst particles move in opposite directions under the action of the Lorentz force. Photogenerated electrons (e - ) and photogenerated holes (h + ) separation, the efficiency of the photocatalytic reaction is improved. Therefore, the magnetic field control device can meet the requirements of catalytic reaction control.

[0006] The object of the present invention is to increase the efficiency of OER.

[0007] Another object of the present invention is to effectively improve the effect of the vector magnetic field by synthesizing ZnO nanorod arrays and doping Fe atoms.

[0008] Yet another object of the present invention is to provide a method for treating ZnO nanorod arrays to enhance their photocatalytic water dissociation efficiency.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides the application of a vector magnetic field in regulating the OER efficiency of a semiconductor nanorod array photocatalyst.

[0011] The inventors have found that the photocatalytic efficiency of semiconductor nanorod arrays can be improved by subjecting semiconductor nanorod array photocatalysts to a vector magnetic field. Therefore, one aspect of the present invention provides a method for improving the catalytic activity of semiconductor nanorod arrays by subjecting semiconductor nanorod array photocatalysts to a vector magnetic field (>0mT, 90°C). In a preferred embodiment of this aspect, the photocatalytic activity of semiconductor nanorod array photocatalysts can be enhanced by exposing them to a vector magnetic field having a magnetic field strength greater than 0mT.

[0012] In some embodiments, the semiconductor nanorod array photocatalyst is selected from at least one of ZnO, TiO2, MoS2, CuS, In2S3, CuInS2, and single-atom Fe-doped ZnO.

[0013] In some embodiments, the angle between the radial direction of the nanorods of the semiconductor nanorod array photocatalyst and the direction of the magnetic field is 0°-90°, preferably 0°, 45° or 90°.

[0014] In some embodiments, the magnetic field strength is greater than 0 mT, preferably 0 mT-20 mT.

[0015] In some embodiments, the modulation is enhancement.

[0016] The second aspect of the present invention provides a method for preparing a ZnO nanorod array, which is synthesized by a hydrothermal method, comprising:

[0017] Dissolve zinc nitrate in anhydrous ethanol, and stir and dissolve at 60°C-65°C for 1.0h-1.5h to form a ZnO nanorod seed solution;

[0018] Dissolve Zn(NO3)2 and ethylenediamine in water to form a ZnO nanorod growth solution;

[0019] The ZnO nanorod seed solution is dropped onto the surface of the FTO electrode, incubated, and rinsed with anhydrous ethanol. After repeating the above steps for several times, the FTO electrode is treated at 350°C-400°C for 20min-30min, cooled to room temperature, and then placed in the ZnO nanorod growth solution, treated at 95°C-96°C for 120min-130min. After the reaction is completed, it is washed to obtain the product.

[0020] The third aspect of the present invention provides a method for preparing a single-atom Fe-doped ZnO nanorod array, which is synthesized by a hydrothermal method, comprising:

[0021] Dissolve zinc nitrate in anhydrous ethanol, and stir and dissolve at 60°C-65°C for 1.0h-1.5h to form a ZnO nanorod seed solution;

[0022] Dissolve Zn(NO3)2 and ethylenediamine in water to form a ZnO nanorod growth solution, then add Fe(NO3)3 to the ZnO nanorod growth solution to make the molar ratio of Zn:Fe in the solution be 10:1, and form a single-atom Fe-doped ZnO nanorod growth solution;

[0023] The ZnO nanorod seed solution is dropped onto the surface of the FTO electrode, incubated, and rinsed with anhydrous ethanol; after repeating the above steps for multiple times, the FTO electrode is treated at 350°C-400°C for 20min-30min, cooled to room temperature, and then the FTO electrode is placed in a single-atom Fe-doped ZnO nanorod growth solution and treated at 95°C-96°C for 120min-130min. After the reaction is completed, it is washed to obtain the obtained product.

[0024] A fourth aspect of the present invention provides a magnetic field control device, comprising: at least two coils arranged in parallel;

[0025] The parallel-arranged coils are arranged at intervals and connected in series via conducting wires.

[0026] In some embodiments, the spacing between adjacent parallel coils is 39 mm-40 mm.

[0027] In some embodiments, the input current between the series parallel coils ranges from 0.0A to 5.0A;

[0028] In some embodiments, the magnetic field generated by the series parallel coils ranges from 0.0 mT to 28.0 mT.

[0029] Beneficial effects of the present invention

[0030] (1) Compared with the existing methods of using magnetic fields to enhance the photocatalytic performance of semiconductors, the present invention makes up for the problem that the vector effect of the magnetic field cannot be fully utilized. The present invention uses a hydrothermal method to synthesize ZnO nanorod arrays and single-atom Fe-doped ZnO nanorod arrays. In order to perform magnetic field vector control, the present invention places the ZnO nanorod array in three relative positions of a cubic parallel uniform magnetic field with adjustable magnetic field strength (the angle between the radial direction of the ZnO nanorod and the direction of the magnetic field: 0°, 45°, 90°) to perform photocatalytic OER. The constructed magnetic field control device is mainly composed of two parallel coils connected in series. The electromagnetic effect generated by the coil is conducive to the rapid adjustment of the magnetic field size. Secondly, the magnetic flux lines between the parallel coils in series are parallel and evenly distributed, which is conducive to the regulation of the magnetic field direction. Due to the existence of a parallel and evenly distributed magnetic field between the parallel coils in series, the photogenerated carriers moving inside the catalyst particles move in opposite directions under the action of the Lorentz force. Photogenerated electrons (e - ) and photogenerated holes (h + ) separation, the efficiency of the photocatalytic reaction is improved. Therefore, the magnetic field control device can meet the requirements of catalytic reaction control.

[0031] (2) The operation method of the present application is simple, universal, and easy to scale up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 is a schematic top view of the magnetic field control device of the present invention;

[0034] Figure 2 is a side view schematic diagram of the magnetic field control device of the present invention;

[0035] Figure 3 It is a physical device diagram of the magnetic field control device of the present invention;

[0036] Figure 4 This is an experimental diagram of the electromagnetic response of the magnetic field control device of the present invention;

[0037] Figure 5 It is a characterization diagram of the ZnO nanorod array of the present invention. A is a SEM image diagram of the ZnO nanorod array. B is a SEM image diagram of the ZnO nanorod array doped with single-atom Fe. C is an XRD test diagram of the ZnO nanorod array and the ZnO nanorod array doped with single-atom Fe. D is an ICP test diagram of the ZnO nanorod array doped with single-atom Fe. E is a TEM element distribution diagram of the ZnO nanorod array doped with single-atom Fe. F is a high-magnification TEM test diagram of the ZnO nanorod array doped with single-atom Fe. G is a photocatalytic oxygen evolution activity diagram of ZnO nanorods, ZnO nanorod arrays and ZnO nanorod arrays doped with single-atom Fe in different magnetic field directions under a 20mT magnetic field. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0039] As introduced in the background technology, due to the randomly oriented carrier transfer caused by the unrestricted transfer of photogenerated carriers along the three-dimensional direction of the particle catalyst and the random orientation of the particle catalyst masking the effect of the magnetic field vector effect, it is difficult for the present invention to achieve effective regulation of the photocatalytic OER on the surface of the catalyst particles under the vector magnetic field, and it is even more impossible to analyze the microscopic mechanism of magnetic field regulation and guide the synthesis of catalysts with excellent magnetic field response.

[0040] In view of this, the first aspect of the present invention is to construct a method for enhancing the efficiency of photocatalytic oxygen evolution reaction of nanorod array materials through a magnetic field.

[0041] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0042] Example 1

[0043] The hydrothermal synthesis method of ZnO nanorod array comprises:

[0044] (1) Dissolve 5 mM zinc nitrate [Zn(CH3COO)2] in anhydrous ethanol and stir at 60°C for 1.0 h to form a ZnO nanorod seed solution.

[0045] (2) Dissolve 25 mM Zn(NO3)2 and 25 mM ethylenediamine (C2H4(NH2)2) in deionized water to form a ZnO nanorod growth solution.

[0046] (3) The growth substrate of the array is FTO electrode (length × width × thickness: 7 cm × 7 mm × 3 mm). Before using the FTO electrode, it was ultrasonically cleaned three times with acetone (10 min), anhydrous ethanol (10 min) and deionized water (10 min), and then dried with N2.

[0047] (4) 20 μL of seed solution was added to the surface of the FTO electrode and incubated for 25 seconds, and then rinsed with a large amount of anhydrous ethanol. After repeating the above steps four times, the FTO electrode was transferred to a tube furnace and treated at 350°C for 20 minutes.

[0048] (5) After cooling to room temperature, the FTO electrode was placed in a glass sealed reactor and 50 mL of ZnO nanorod growth solution was added. The reaction was carried out in a 95°C forced air drying oven for 120 min. After the reaction was completed, the ZnO nanorod array was obtained by washing with deionized water.

[0049] Hydrothermal synthesis of single-atom Fe-doped ZnO nanorod arrays

[0050] In order to achieve the doping of single-atom Fe in ZnO nanorods, the present invention adds 2.5mM Fe(NO3)3 (Zn:Fe=10:1) into the ZnO nanorod growth solution to form a single-atom Fe-doped ZnO nanorod growth solution. The other operation steps are the same as the hydrothermal synthesis method of ZnO nanorod arrays.

[0051] Example 2

[0052] A magnetic field control device comprises: at least two coils arranged in parallel;

[0053] The parallel-arranged coils are arranged at intervals and connected in series via conducting wires.

[0054] Construction of parallel coils: In order to make the direction and magnitude of the current between the coils consistent, the two parallel coils are first connected in series.

[0055] The specific method of connecting parallel coils in series is as follows: after the coil is wound with copper wire, it is extended to the next coil for winding. This ensures the stable series connection of the two coils. After the copper wire is wound, it is wrapped with insulating tape to ensure electrical safety.

[0056] Reservation of space between parallel coils: In order to make the device suitable for single-molecule super-resolution fluorescence microscopy, a certain amount of space is reserved between the parallel coils.

[0057] With reference to the diameter of the objective lens and the size of the stage, the reserved spacing between the parallel coils is 39 mm.

[0058] Input of coil current: In order to form a parallel magnetic field between series parallel coils, a stable current is input into the coil to form an inductive magnetic field.

[0059] The input current between the series parallel coils ranges from 0.0 A to 5.0 A. The magnetic field generated by the series parallel coils ranges from 0.0 mT to 28.0 mT.

[0060] The performance of the magnetic field control device was tested, and the electromagnetic response experimental results were as follows: Figure 4 shown.

[0061] Example 3

[0062] Magnetic field regulation to enhance the photocatalytic oxygen evolution activity of ZnO nanorod arrays and single atom Fe-doped ZnO nanorod arrays.

[0063] The photocatalytic oxygen evolution activity of ZnO nanorod array and single-atom Fe-doped ZnO nanorod array was evaluated by placing the sample prepared in Example 1 in a quartz reactor containing 3.0 mL of deionized water, and without adding any additives, the photocatalytic oxygen evolution activity of ZnO nanorod array or single-atom Fe-doped ZnO nanorod array under a magnetic field was evaluated. Nitrogen was used as a carrier and deionized water was used as an oxygen source, and the reaction products were measured offline using a GC-7920 micro gas chromatograph.

[0064] The magnetic field is regulated by a constructed magnetic field regulation device. The magnetic field strength range is 0mT, 5mT, 10mT, 15mT, 20mT. The magnetic field direction is 0o, 45o, 90o.

[0065] The test results are as follows Figure 5 shown.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Application of vector magnetic field in regulating the OER efficiency of semiconductor nanorod array photocatalysts.

2. The use according to claim 1, characterized in that The semiconductor nanorod array photocatalyst is selected from ZnO, TiO2, MoS2, CuS, In2S3, CuInS2, and single-atom Fe-doped ZnO nanorod array.

3. The use according to claim 1, characterized in that The angle between the radial direction of the nanorods of the semiconductor nanorod array photocatalyst and the direction of the magnetic field is 0°-90°, preferably 0°, 45° or 90°.

4. The use according to claim 1, characterized in that The magnetic field strength is greater than 0 mT, preferably 0 mT-20 mT.

5. The use according to claim 1, characterized in that The regulation is enhancement.

6. A method for preparing a ZnO nanorod array, characterized in that: The hydrothermal method is used for synthesis, including: Dissolve zinc nitrate in anhydrous ethanol, and stir and dissolve at 60°C-65°C for 1.0h-1.5h to form a ZnO nanorod seed solution; Dissolve Zn(NO3)2 and ethylenediamine in water to form a ZnO nanorod growth solution; The ZnO nanorod seed solution is dropped onto the surface of the FTO electrode, incubated, and rinsed with anhydrous ethanol. After repeating the above steps for several times, the FTO electrode is treated at 350°C-400°C for 20min-30min, cooled to room temperature, and then placed in the ZnO nanorod growth solution, treated at 95°C-96°C for 120min-130min. After the reaction is completed, it is washed to obtain the product.

7. A method for preparing a single-atom Fe-doped ZnO nanorod array, characterized in that: The hydrothermal method is used for synthesis, including: Dissolve zinc nitrate in anhydrous ethanol, and stir and dissolve at 60°C-65°C for 1.0h-1.5h to form a ZnO nanorod seed solution; Dissolve Zn(NO3)2 and ethylenediamine in water to form a ZnO nanorod growth solution, then add Fe(NO3)3 to the ZnO nanorod growth solution to make the molar ratio of Zn:Fe in the solution be 10:1, and form a single-atom Fe-doped ZnO nanorod growth solution; The ZnO nanorod seed solution is dropped onto the surface of the FTO electrode, incubated, and rinsed with anhydrous ethanol; after repeating the above steps for multiple times, the FTO electrode is treated at 350°C-400°C for 20min-30min, cooled to room temperature, and then the FTO electrode is placed in a single-atom Fe-doped ZnO nanorod growth solution and treated at 95°C-96°C for 120min-130min. After the reaction is completed, it is washed to obtain the obtained product.

8. A magnetic field control device, characterized in that: include: at least two coils arranged in parallel; The parallel-arranged coils are arranged at intervals and connected in series via conducting wires.

9. The magnetic field control device according to claim 8, characterized in that: The distance between adjacent parallel coils is 39mm-40mm.

10. The magnetic field control device according to claim 8, characterized in that: The input current range between series parallel coils is 0.0A-5.0A; Alternatively, the magnetic field generated by the series parallel coils ranges from 0.0 mT to 28.0 mT.

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