Nanotube array photoelectrocatalytic electrode and its preparation method and application

Abstract

The present invention discloses a nanotube array photoelectrocatalytic electrode and its preparation method and application, and specifically relates to the field of photoelectrocatalytic materials. The preparation method of the material includes titanium sheet pretreatment, three-step anodization method to prepare highly ordered titanium dioxide nanotube arrays, preparation of precursor solution and preparation of highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode. The electrode can be used in the in-situ green preparation of high-purity H2O2 in the electrochemical reduction reaction of oxygen; it can be used to efficiently generate photogenerated electron-holes and reactive oxygen species in low-conductivity water bodies; it can be used to kill microorganisms and degrade pesticide residues, organic matter and antibiotics during food cleaning or water purification. The present invention uses titanium as a substrate, has high strength, good thermal strength and good corrosion resistance, and can overcome the application limitations of traditional granular catalysts; adopts a three-step anodization method to prepare titanium dioxide nanotube arrays with highly ordered surfaces, greatly increasing the loading area of ​​the substrate material.

Description

Technical Field

[0001] The present invention relates to the field of photoelectrocatalytic materials, and in particular to a nanotube array photoelectrocatalytic electrode, a preparation method thereof, and an application thereof; in particular, to a Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode, and an application thereof. Background Art

[0002] As living standards continue to rise, consumers' demands for higher quality fruits and vegetables continue to rise. Since the early 20th century, the widespread use of modern agricultural technologies (such as fertilizers, pesticides, and plant growth regulators) in the agricultural economy has greatly increased fruit and vegetable production, but has also led to serious pesticide residues in fruits and vegetables, posing a serious threat to consumer health.

[0003] Pesticide residues refer to the undecomposed residues of pesticide precursors, intermediates, and metabolites that remain on the surfaces of fruits and vegetables after they are sprayed with pesticides to increase yield during their growth process. Long-term consumption of agricultural products containing excessive pesticide residues can lead to the accumulation of harmful substances in the body, causing chronic poisoning and ultimately manifesting as illness. Food safety issues have been numerous in recent years, and pesticide residues have been a major concern. As fruits and vegetables are among the most susceptible to pesticide contamination, washing methods have become the last line of defense for ensuring their safety. Common methods for washing fruits and vegetables include washing, blanching, and physical and chemical treatments such as high temperatures. These methods are effective in removing different types of pesticide residues from different types of vegetables, but removal efficiency varies significantly depending on the type of fruit or vegetable and the type of pesticide residue. Generally speaking, traditional washing methods are inefficient and have limitations, including reduced nutritional value, secondary pesticide residues, and poor cleaning effectiveness. More effective vegetable washing methods are needed.

[0004] Fruit and vegetable washers and food purifiers of various brands are currently available on the market. In terms of technical principles, ozone and electrolysis are commonly used purification methods in fruit and vegetable washers. Ozone, as a strong oxidant, has a redox potential of 2.07 eV and is effective in degrading pesticide residues. However, it can react with organic matter in water to form harmful byproducts such as bromate, and high concentrations of ozone can be harmful to the human body. Electrolysis technology primarily removes pollutants from water by breaking down water molecules into ionic, reactive free radicals. Hydroxyl radicals have a redox potential of 2.8 eV, 35% higher than that of ozone. The chemical reactions they participate in are free radical reactions, and they react extremely quickly with organic matter in water, making them less likely to cause secondary pollution. However, current electrolysis technology is limited by the low conductivity of tap water, resulting in a limited amount of reactive free radicals, which in turn affects its effectiveness in cleaning food or purifying water.

[0005] Furthermore, electrode materials are the core of electrolysis technology. Different electrocatalysts can lead to significant differences in the electrochemical reactions at the anode, such as the production of hypochlorous acid or halogenated byproducts during the electrolysis process. Therefore, the rational design of electrocatalysts that can efficiently generate active free radicals remains a challenge and key point in electrolysis technology.

[0006] Chinese patent CN202210194625.0 provides a method for preparing a vacuum carbon-doped titanium dioxide nanotube array structure and its application. Although it provides a method for preparing a titanium dioxide nanotube array photoanode structure by secondary electrochemical anodization, it is used as an anode material. Ethylene glycol is formed on the surface of the titanium dioxide nanotubes through vacuum annealing to form a carbon shell, which may affect the absorption of the titanium dioxide nanotube array in the ultraviolet band to a certain extent.

[0007] Chinese patent CN201910801449.0 provides a method for preparing a photoelectrode. Although it provides a preparation process for a titanium dioxide nanoribbon array doped with graphite phase carbon nitride, it uses the titanium dioxide nanoribbon array as a cathode for depositing graphite phase carbon nitride, mainly solving the problems of severe surface charge recombination and low visible light utilization of titanium dioxide by doping. Summary of the Invention

[0008] To this end, the present invention provides a nanotube array photoelectrocatalytic electrode and a preparation method and application thereof to solve the problem of incomplete removal of existing electrolytic pesticides.

[0009] Chinese patents CN202210194625.0 and CN201910801449.0 only provide methods for preparing and modifying titanium dioxide nanotubes. The present invention increases the specific surface area of ​​the base material after preparing titanium dioxide nanotubes, and then loads Pt / WO3 catalyst. The performance of the electrode is mainly reflected by the loaded catalyst, not titanium dioxide. For example, WO3 is a catalyst that responds to visible light.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] According to a first aspect of the present invention, a method for preparing a nanotube array photoelectrocatalytic electrode is provided, characterized by comprising:

[0012] Step 1: Pretreatment of titanium sheet

[0013] The surface of the titanium sheet is polished until the surface is flat and smooth, the polished titanium sheet is ultrasonically degreased with acetone, ethanol and deionized water respectively, and the degreased titanium sheet is dried in an inert gas flow to obtain a pretreated titanium sheet;

[0014] Step 2: Preparation of highly ordered titanium dioxide nanotube arrays by three-step anodization method

[0015] a) using a pretreated titanium sheet as an anode, graphite as a cathode, and a mixed solution containing NH4F and ethylene glycol as an electrolyte, and performing an anodic oxidation treatment under the action of a DC power supply to obtain a sample titanium sheet;

[0016] b) placing the sample titanium sheet in a hydrochloric acid aqueous solution and performing ultrasonic cleaning to remove the TiO2 film generated by oxidation, thereby obtaining a preliminary titanium sheet;

[0017] c) After the preliminary titanium sheet is cleaned and air-dried, the first electrolytic oxidation is performed again according to the experimental conditions in step a), and then the electrolyte is rapidly heated and the second electrolytic oxidation is performed again to obtain a highly ordered TiO2 nanotube array, and the TiO2 nanotube array is rinsed with ethanol and dried under an inert gas flow to obtain a dry TiO2 nanotube array electrode;

[0018] Step 3: Preparation of precursor solution

[0019] Adding the chloroplatinic acid solution to the ammonium metatungstate solution and stirring at room temperature to obtain a precursor solution;

[0020] Step 4: Preparation of highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode

[0021] Under heating, the precursor solution is evenly sprayed on the TiO2 nanotube array electrode to fix the elements. After coating, the electrode is cooled to room temperature and then placed in a tube furnace for annealing to obtain a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode.

[0022] As an example, a Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode with high catalytic activity is prepared as follows:

[0023] (1) A titanium sheet (thickness 0.5 mm, purity 99.6%) was polished using 1000#, 2000#, 3000#, and 5000# sandpaper until the surface was flat and smooth. The titanium sheet was then ultrasonicated in acetone, ethanol, and deionized water for 10 min each. The cleaned titanium sheet was dried in a nitrogen gas stream.

[0024] (2) Using the pretreated titanium sheet as the anode and graphite as the cathode, an aqueous solution containing 0.4% to 0.6% (mass fraction) NH4F and 90% to 95% (volume fraction) ethylene glycol as the electrolyte, electrolyze for 30 to 60 minutes at a DC voltage of 20 to 30 V, and maintain the electrolyte temperature at 20°C;

[0025] (3) The sample was placed in a 1 M HCl aqueous solution and ultrasonicated for 1 to 1.5 h to remove the TiO2 film formed by oxidation on the electrode surface;

[0026] (4) After the titanium sheet is cleaned and air-dried, the electrode is electrolytically oxidized in the electrolyte described in (2) under a 30 V DC voltage for 30 to 40 minutes, and the electrolyte temperature is rapidly raised from 20° C. to 30° C., and then the oxidation treatment is performed again for 30 to 40 minutes;

[0027] (5) adding ammonium metatungstate with a concentration of 10 to 30 wt.% to a beaker containing 90 mL of deionized water, and heating and stirring on a thermostat until the ammonium metatungstate is completely dissolved;

[0028] (6) Add 10 mL of 10-15 mmol / L chloroplatinic acid solution to the ammonium metatungstate solution and stir at room temperature for 2 hours to fully mix the precursor solution;

[0029] (7) placing the TiO2 nanotube array electrode dried in (4) on a temperature-controlled heating plate, adjusting the temperature to 150-200°C, and then spraying the precursor solution evenly on the TiO2 nanotube array electrode to fix the elements. After coating, the electrode is cooled to room temperature;

[0030] (8) The dried electrode was placed in a tube furnace (air atmosphere) and annealed at 500-600°C for 3-4 hours to obtain a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode.

[0031] Furthermore, in step 2, the mass fraction of NH4F in a) is 0.4% to 0.6%, the volume concentration of ethylene glycol is 90% to 95%, the constant voltage used by the DC power supply is 20 to 30 V, the anodizing treatment time is 30 to 60 min, and the electrolyte temperature is maintained at 20°C.

[0032] Furthermore, in step 2, the concentration of the hydrochloric acid aqueous solution in b) is 1 mol / L, and the ultrasonic cleaning time is 1 to 1.5 hours.

[0033] Furthermore, in step 2, the first electrolytic oxidation time in c) is 30 to 40 minutes, and the rapid heating of the electrolyte is to rapidly raise the electrolyte temperature from 20° C. to 30° C., and the second oxidation treatment time is 30 to 40 minutes.

[0034] Furthermore, in the step 3, the concentration of ammonium metatungstate is 10-30 wt.%; and the concentration of chloroplatinic acid solution is 10-15 mmol / L.

[0035] Furthermore, in step 4, the heating is performed on a heating plate with controllable temperature.

[0036] Furthermore, the temperature of the heating plate is controlled at 150-200°C.

[0037] Furthermore, in step 4, the annealing temperature is 500-600° C., and the annealing time is 3-4 hours.

[0038] According to the second aspect of the present invention, a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode is provided, characterized in that it is prepared by the above method.

[0039] According to a third aspect of the present invention, a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode is provided, which is used as a cathode in any of the following applications:

[0040] a) Application in the in-situ green preparation of high-purity H2O2 in the electrochemical reduction reaction of oxygen;

[0041] b) Application in the efficient generation of photogenerated electrons-holes and reactive oxygen species in low-conductivity water;

[0042] c) Application in the food purification and cleaning process to kill microorganisms, degrade pesticide residues, and remove antibiotics.

[0043] As an example, a Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode can generate superoxide radicals O2 during the electrochemical reduction reaction of oxygen by irradiation with ultraviolet (UV mercury lamp, UV-LED) and visible light. - , hydroxyl free radical OH, H2O2, etc.

[0044] As an example, a Pt / WO3-coated TiO2 nanotube array photoelectrocatalytic electrode produces a large number of photogenerated electrons-holes and reactive oxygen species during the oxygen reduction process, which can kill microorganisms, degrade pesticide residues (organophosphorus, organochlorine, pyrethroids, carbamates, etc.) during the food purification and cleaning process, and remove antibiotics.

[0045] principle:

[0046] The Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode can be used as a cathode. Pt as an auxiliary catalyst can greatly improve the catalytic activity of WO3 and can use air and water to produce a two-electron reduction reaction on the electrode surface: O2+2e - +2H + →H2O2, and then in situ green preparation of high-purity H2O2 for application.

[0047] During the electrochemical reduction of oxygen, the Pt / WO3-coated TiO2 nanotube array photoelectrocatalytic electrode can efficiently generate photogenerated electrons-holes and reactive oxygen species in low-conductivity water bodies under irradiation with ultraviolet (200-400nm, such as UV mercury lamp, UV-LED) and visible light (400-700nm):

[0048] WO3+hν(400~700nm)→hVB++eCB - ;

[0049] H2O2+hν(UV)→2OH

[0050] h VB + +H2O→OH+H +

[0051] h VB + +OH - →OH

[0052] e CB - +O2→O2 -

[0053] O2 - +H + +e CB - →H2O2

[0054] The Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode produces a large number of photogenerated electrons-holes and reactive oxygen species (superoxide radicals O2 - , hydroxyl radicals OH, H2O2, etc.), can kill microorganisms in the process of food purification and cleaning, degrade pesticide residues (organophosphorus, organochlorine, pyrethroids, carbamates, etc.), and remove antibiotics.

[0055] The present invention has the following advantages:

[0056] (1) The present invention uses titanium as the substrate, which has high strength, good thermal strength and good corrosion resistance, and can overcome the application limitations of traditional granular catalysts; a three-step anodization method is used to prepare a highly ordered titanium dioxide nanotube array on the surface, greatly increasing the loading area of ​​the substrate material.

[0057] (2) The photocatalytic activity of pure WO3 is low, and it is difficult to reduce oxygen under single-electron conditions. The present invention, by doping a small amount of Pt as an auxiliary catalyst, can provide an electron pool for the reaction, thereby promoting the electron pathway for the electrochemical reduction of oxygen.

[0058] (3) The present invention uses the Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode as a cathode, which can generate hydrogen peroxide as an intermediate medium and further generate a large number of hydroxyl radicals under ultraviolet excitation. In addition, WO3 as a photocatalyst can effectively absorb visible light and generate photogenerated electrons-holes, which has a significant synergistic effect on the generation of reactive oxygen species.

[0059] (4) The present invention uses the Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode in the field of electrolytic purification of fruits and vegetables, which can cleverly solve the problem of limited generation of active oxygen species at the anode due to low conductivity in traditional electrolysis of tap water technology, and greatly improve the removal effect of microorganisms, pesticide residues, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0061] The structures, proportions, sizes, etc. illustrated in this specification are intended only to complement the contents disclosed herein and to facilitate understanding and reading by persons familiar with the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall still fall within the scope of the technical contents disclosed herein.

[0062] Figure 1 This is a flow chart for preparing a photoelectrocatalytic electrode with a Pt / WO3 coating and TiO2 nanotube array having high catalytic activity provided in Example 1 of the present invention.

[0063] Figure 2 This is the anodized TiO2 nanotube array provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0064] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0065] Example 1

[0066] like Figure 1 As shown in the electrode preparation flow chart, this embodiment provides a method for preparing a photoelectrocatalytic electrode with a high catalytic activity, a Pt / WO3 coated TiO2 nanotube array:

[0067] A titanium sheet (0.5 mm thick, 99.6% purity) was polished using 1000#, 2000#, 3000#, and 5000# sandpaper until the surface was flat and smooth. The titanium sheet was then ultrasonicated in acetone, ethanol, and deionized water for 10 min each, and then dried in a nitrogen gas stream.

[0068] The titanium sheet obtained by pretreatment was used as the anode and graphite as the cathode. The electrolyte contained 0.5% (mass fraction) NH4F and 5% (volume fraction) H2O in ethylene glycol. The sample was electrolyzed at 30V DC for 40 minutes, and the electrolyte temperature was maintained at 20°C. The sample was placed in a 1M HCl aqueous solution and ultrasonicated for 1.5 hours to remove the TiO2 film formed by oxidation on the electrode surface. After the titanium sheet was washed and air-dried, it was electrolytically oxidized in 0.5% NH4F and 5% water in ethylene glycol solution at 30V DC for 30 minutes. After the electrolyte temperature was rapidly raised from 20°C to 30°C, the oxidation treatment was carried out again for 30 minutes.

[0069] The TiO2 nanotube array after anodization is shown in Figure 2. Figure 2 shown.

[0070] Add 20 wt.% ammonium metatungstate to a beaker containing 90 mL of deionized water, and heat and stir on a thermostat until the ammonium metatungstate is completely dissolved. Add 10 mL of 10 mmol / L chloroplatinic acid solution to the ammonium metatungstate solution and stir at room temperature for 2 hours to fully mix the precursor solution.

[0071] The dried TiO2 nanotube array electrode was placed on a temperature-controllable heating plate and the temperature was adjusted to 180°C. The precursor solution was then evenly sprayed on the TiO2 nanotube array electrode to fix the elements. After coating, the electrode was cooled to room temperature. The dried electrode was placed in a tubular furnace (air atmosphere) and annealed at 600°C for 4 hours to obtain a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode.

[0072] Example 2

[0073] This embodiment provides a method for preparing a photoelectrocatalytic electrode with a Pt / WO3 coating and a TiO2 nanotube array having high catalytic activity:

[0074] A titanium sheet (0.5 mm thick, 99.6% purity) was polished using 1000#, 2000#, 3000#, and 5000# sandpaper until the surface was flat and smooth. The titanium sheet was then ultrasonicated in acetone, ethanol, and deionized water for 10 min each, and then dried in a nitrogen gas stream.

[0075] The titanium sheet obtained by pretreatment was used as the anode and graphite as the cathode. An aqueous solution containing 0.6% (mass fraction) NH4F and 90% (volume fraction) ethylene glycol was used as the electrolyte. Electrolysis was carried out at 30V DC for 40 minutes, and the electrolyte temperature was maintained at 20°C. The sample was placed in a 1M HCl aqueous solution and ultrasonicated for 1 hour to remove the TiO2 film formed by oxidation on the electrode surface. After the titanium sheet was washed and air-dried, it was electrolytically oxidized in a 0.6% NH4F and 90% ethylene glycol solution at 30V DC for 30 minutes. After the electrolyte temperature was rapidly raised from 20°C to 30°C, oxidation treatment was carried out again for 30 minutes.

[0076] Add 30 wt.% ammonium metatungstate to a beaker containing 90 mL of deionized water, and heat and stir on a thermostat until the ammonium metatungstate is completely dissolved. Add 10 mL of 15 mmol / L chloroplatinic acid solution to the ammonium metatungstate solution and stir at room temperature for 2 hours to fully mix the precursor solution.

[0077] The dried TiO2 nanotube array electrode was placed on a temperature-controllable heating plate and the temperature was adjusted to 200°C. The precursor solution was then evenly sprayed on the TiO2 nanotube array electrode to fix the elements. After coating, the electrode was cooled to room temperature. The dried electrode was placed in a tubular furnace (air atmosphere) and annealed at 550°C for 3.5 hours to obtain a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode.

[0078] Example 3

[0079] This embodiment provides a method for preparing a photoelectrocatalytic electrode with a Pt / WO3 coating and a TiO2 nanotube array having high catalytic activity:

[0080] A titanium sheet (0.5 mm thick, 99.6% purity) was polished using 1000#, 2000#, 3000#, and 5000# sandpaper until the surface was flat and smooth. The titanium sheet was then ultrasonicated in acetone, ethanol, and deionized water for 10 min each, and then dried in a nitrogen gas stream.

[0081] The titanium sheet obtained by pretreatment was used as the anode and graphite as the cathode. An aqueous solution containing 0.5% (mass fraction) NH4F and 94% (volume fraction) ethylene glycol was used as the electrolyte. Electrolysis was carried out at 30V DC for 40 minutes, and the electrolyte temperature was maintained at 20°C. The sample was placed in a 1M HCl aqueous solution and ultrasonicated for 1 hour to remove the TiO2 film formed by oxidation on the electrode surface. After the titanium sheet was washed and air-dried, it was electrolytically oxidized in a 0.5% NH4F and 94% aqueous ethylene glycol solution at 30V DC for 30 minutes. After the electrolyte temperature was rapidly raised from 20°C to 30°C, oxidation treatment was carried out again for 30 minutes.

[0082] Add 25wt.% ammonium metatungstate to a beaker containing 90mL of deionized water, and heat and stir on a thermostat until the ammonium metatungstate is completely dissolved; add 10mL of 12mmol / L chloroplatinic acid solution to the ammonium metatungstate solution and stir at room temperature for 2 hours to fully mix the precursor solution;

[0083] The dried TiO2 nanotube array electrode was placed on a temperature-controllable heating plate and the temperature was adjusted to 160°C. The precursor solution was then evenly sprayed on the TiO2 nanotube array electrode to fix the elements. After coating, the electrode was cooled to room temperature. The dried electrode was placed in a tubular furnace (air atmosphere) and annealed at 500°C for 3 hours to obtain a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode.

[0084] Example 4

[0085] This example provides an application of a high catalytic activity Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode. The electrode prepared in Example 1 was used as the cathode and platinum was used as the anode to treat water containing two different microbial concentrations. The high initial concentration (5.7*10 5 CFU / mL and low initial concentration (2.6*10 3 After 2 minutes of treatment, the sterilization rate of the Escherichia coli solution with a concentration of 100 CFU / mL can reach more than 99.98%, and can eventually be completely killed.

[0086] Example 5

[0087] This embodiment provides an application of a high catalytic activity Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode. The electrode prepared in Example 1 was used as the cathode and platinum was used as the anode. 6 After 2 minutes of treatment, the sterilization rate of Staphylococcus aureus solution with a CFU / mL can reach more than 99.97%, and can eventually be completely killed.

[0088] Example 6

[0089] This example provides an application of a highly catalytically active Pt / WO3-coated TiO2 nanotube array photoelectrocatalytic electrode. Using the electrode prepared in Example 1 as the cathode and platinum as the anode, electrolysis of water containing a certain amount of pesticide (trichlorfon) residue in leafy green vegetables was performed. After 5 minutes of treatment, the degradation rate of trichlorfon reached 99.7%.

[0090] Example 7

[0091] This example provides an application of a highly catalytically active Pt / WO3-coated TiO2 nanotube array photoelectrocatalytic electrode. Using the electrode prepared in Example 1 as the cathode and platinum as the anode, electrolysis was performed on leafy green vegetables containing a certain amount of pesticide (DDV) residue. After 5 minutes of treatment, the DDV degradation rate reached 98.9%.

[0092] Comparative Example 1

[0093] A titanium sheet (0.5 mm thick, 99.6% purity) was polished using 1000#, 2000#, 3000#, and 5000# sandpaper until the surface was flat and smooth. The titanium sheet was then ultrasonicated in acetone, ethanol, and deionized water for 10 min each, and then dried in a nitrogen gas stream.

[0094] The titanium sheet obtained by pretreatment was used as the anode, graphite as the cathode, and an ethylene glycol solution containing 0.5% (mass fraction) NH4F and 5% (volume fraction) H2O was used as the electrolyte. The sample was electrolyzed at 30V DC for 40 minutes, and the electrolyte temperature was maintained at 20°C. The sample was placed in a 1M HCl aqueous solution and ultrasonicated for 1.5 hours to remove the TiO2 film generated by oxidation on the electrode surface. After the titanium sheet was washed and air-dried, the electrode was electrolytically oxidized in a 0.5% NH4F and 5% ethylene glycol solution at 30V DC for 30 minutes. After the electrolyte temperature was rapidly increased from 20°C to 30°C, it was oxidized again for 30 minutes to obtain a highly ordered TiO2 nanotube array. The TiO2 nanotube array was rinsed with ethanol and dried under an inert gas N2 flow to obtain a dry TiO2 nanotube array electrode.

[0095] Test Example 1

[0096] The electrode prepared in Comparative Example 1 was used as the cathode and platinum was used as the anode to treat water containing two different microbial concentrations. 5 CFU / mL and low initial concentration (2.6*10 3 CFU / mL) of Escherichia coli solution was treated for 2 minutes, and the sterilization rate was less than 85%.

[0097] Test Example 2

[0098] The electrode prepared in Comparative Example 1 was used as the cathode and platinum was used as the anode. 6 After 2 min of treatment, the sterilization rate of Staphylococcus aureus solution with a CFU / mL was less than 80%.

[0099] Test Example 3

[0100] The electrode prepared in Comparative Example 1 was used as the cathode and platinum as the anode to electrolyze water containing a certain amount of pesticide (trichlorfon) residues in green leafy vegetables. After 5 minutes of treatment, the degradation rate of trichlorfon was 48%.

[0101] Test Example 4

[0102] The electrode prepared in Comparative Example 1 was used as the cathode and platinum was used as the anode to electrolyze water containing a certain amount of pesticide (dichlorvos) residues in green leafy vegetables. After 5 minutes of treatment, the degradation rate of dichlorvos was 40%.

[0103] It can be seen that the application of the electrodes of Examples 4-7 of the present invention has better sterilization ability and pesticide removal effect than the application of the electrodes of Comparative Examples 1-4.

[0104] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for preparing a nanotube array photoelectrocatalytic electrode, characterized in that: include: Step 1: Pretreatment of titanium sheet The surface of the titanium sheet is polished until the surface is flat and smooth, the polished titanium sheet is ultrasonically degreased with acetone, ethanol and deionized water respectively, and the degreased titanium sheet is dried in an inert gas flow to obtain a pretreated titanium sheet; Step 2: Preparation of highly ordered titanium dioxide nanotube arrays by three-step anodization method a) using a pretreated titanium sheet as an anode, graphite as a cathode, and a mixed solution containing NH4F and ethylene glycol as an electrolyte, and performing an anodic oxidation treatment under the action of a DC power supply to obtain a sample titanium sheet; b) placing the sample titanium sheet in a hydrochloric acid aqueous solution and performing ultrasonic cleaning to obtain a preliminary titanium sheet; c) After the preliminary titanium sheet is cleaned and air-dried, the first electrolytic oxidation is performed again according to the experimental conditions in step a), and then the electrolyte is rapidly heated and the second electrolytic oxidation is performed again to obtain a highly ordered TiO2 nanotube array, and the TiO2 nanotube array is rinsed with ethanol and dried under an inert gas flow to obtain a dry TiO2 nanotube array electrode; Step 3: Preparation of precursor solution Adding the chloroplatinic acid solution to the ammonium metatungstate solution and stirring at room temperature to obtain a precursor solution; Step 4: Preparation of highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode Under heating, the precursor solution is evenly sprayed on the TiO2 nanotube array electrode. After coating, the electrode is cooled to room temperature and then placed in a tube furnace for annealing to obtain a highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode.

2. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 1, characterized in that: In step 2, the mass fraction of NH4F in a) is 0.4% to 0.6%, the volume concentration of ethylene glycol is 90% to 95%, the constant voltage used by the DC power supply is 20 to 30 V, the anodizing treatment time is 30 to 60 minutes, and the electrolyte temperature is maintained at 20°C.

3. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 1, characterized in that: In step 2, the concentration of the hydrochloric acid aqueous solution in b) is 1 mol / L, and the ultrasonic cleaning time is 1 to 1.5 hours.

4. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 1, characterized in that: In step 2, the first electrolytic oxidation time in c) is 30 to 40 minutes, and the rapid heating of the electrolyte is to rapidly raise the electrolyte temperature from 20° C. to 30° C., and the second oxidation treatment time is 30 to 40 minutes.

5. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 1, characterized in that: In the step 3, the concentration of ammonium metatungstate is 10-30 wt.%; the concentration of chloroplatinic acid solution is 10-15 mmol / L.

6. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 1, characterized in that: In the step 4, the heating is performed on a temperature-controllable heating plate.

7. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 6, characterized in that: The temperature of the heating plate is controlled at 150-200°C.

8. The method for preparing a nanotube array photoelectrocatalytic electrode according to claim 1, characterized in that: In the step 4, the annealing temperature is 500-600° C., and the annealing time is 3-4 hours.

9. A highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode, characterized in that: The invention is prepared by the method according to any one of claims 1 to 8.

10. Use of the highly active Pt / WO3 coated TiO2 nanotube array photoelectrocatalytic electrode according to claim 9 as a cathode in any of the following: a) Application in the in-situ green preparation of high-purity H2O2 in the electrochemical reduction reaction of oxygen; b) Application in the efficient generation of photogenerated electrons-holes and reactive oxygen species in low-conductivity water; c) Application in killing microorganisms, degrading pesticide residues, organic matter and antibiotics during food cleaning or water purification.

Images