Method for assisting substrate to grow titanium dioxide nano array through electric field and application

Abstract

The invention discloses a method for assisting a substrate to grow a titanium dioxide nano array through an electric field and application. The method comprises the following steps: 1) cleaning a substrate: cleaning the substrate with a cleaning solution, and drying for later use; 2) growing a titanium dioxide nano array on the substrate: fixing the substrate on a platinum sheet electrode clamp in a reaction container, and fixing a titanium source on another platinum sheet electrode clamp; adding a reaction solution formed by mixing hydrogen peroxide, nitric acid and melamine into the reaction container, connecting an electrode clamp with a direct-current power supply, connecting a positive electrode with a titanium source, and connecting a negative electrode with a substrate; applying constant voltage of 20-60V to the two electrode clamps, and reacting for 2-6 hours; and 3) cleaning and collecting the sample: taking out the substrate from the electrode clamp, ultrasonically cleaning and drying. According to the scheme, the preparation process is simple and rapid, and the titanium dioxide nanometre grown on the substrate has various morphologies and is expected to be applied to the fields of adsorption, photocatalysis, gas sensing and the like.

Description

Technical Field

[0001] The present invention relates to a method for growing titanium dioxide nanoarrays on a substrate under the assistance of an electric field, which can be applied to the fields of photocatalysis, sewage treatment, gas sensors, gas purification, etc., and belongs to the fields of energy environment and new materials. Background Art

[0002] Titanium dioxide (TiO2) is an important inorganic functional material. Due to its excellent photocatalytic properties, chemical stability, high refractive index, and non-toxicity, it is widely used in photocatalytic degradation of pollutants, solar cells, coatings, cosmetics, and antibacterial materials. The preparation method of TiO2 directly affects its crystal form, morphology, specific surface area, and photocatalytic activity. Therefore, the development of efficient and controllable TiO2 synthesis technologies is of great significance.

[0003] At present, the preparation methods of TiO2 mainly include sol-gel method, hydrothermal / solvothermal method, vapor deposition method, precipitation method, anodization method, etc.

[0004] Sol-gel method: TiO2 nanoparticles are obtained by hydrolyzing and polycondensing titanium alkoxides (such as tetrabutyl titanate) to form a sol, which is then dried and calcined. This method can control the product crystal form and particle size, but is easily affected by hydrolysis conditions, and the calcination process may cause particle agglomeration.

[0005] Hydrothermal / solvothermal method: Under high temperature and high pressure conditions, water or organic solvents are used to promote the directional growth of TiO2 crystals, and highly crystalline nanostructures (such as nanotubes and nanosheets) can be prepared, but the equipment requirements are relatively high.

[0006] Vapor deposition (CVD / PVD): TiO2 thin films are deposited through vapor phase reactions. This method is suitable for optical coatings, but it is expensive and difficult to prepare powder materials on a large scale.

[0007] Precipitation method: Using titanium salt (such as TiCl4) as a precursor, the TiO2 precursor is precipitated by adjusting the pH value, and then the product is obtained by calcination. The process is simple but easy to introduce impurities.

[0008] Anodic oxidation method: Utilize the selective corrosion of titanium metal in fluorine-containing electrolyte under the action of DC voltage to grow TiO2 nanotube arrays on titanium metal substrate. The process is simple but the nanostructure is limited.

[0009] In recent years, green synthesis methods (such as bio-templated methods and microwave-assisted methods) and doping modifications (such as N and C doping) have become research hotspots to improve the photoresponse range and catalytic efficiency of TiO2. In the future, low-cost, highly active, and scalable TiO2 preparation technologies will remain an important development direction in this field. In addition, TiO2 thin films are more attractive for photocatalytic applications. Compared with powders, thin films are easy to recycle and have excellent cyclic stability. The choice of different substrates can also affect the performance of the film, which places higher demands on the universality of the preparation method. Existing technologies use the chemical reaction between titanium metal and hydrogen peroxide to obtain nanostructured TiO2 array films such as nano (ZL200510060751.3), nanoflowers (ZL200610049498.6), and nanowires (ZL200910096796.4) in an open system at 60-80°C.

[0010] The present invention, with the assistance of an electric field, utilizes the anodic dissolution of titanium metal in the reaction solution at room temperature to provide the titanium ions required for TiO2 growth. At the same time, it directly utilizes the heat generated during the electrochemical reaction to successfully grow TiO2 nanowire arrays on carbon cloth, titanium sheets and titanium wire mesh. In addition, it can also react under water bath heating conditions to obtain TiO2 nanoflowers and nanosheet arrays with diverse morphologies. The present invention has a short preparation time, low production cost, and value for industrial production applications. Summary of the Invention

[0011] The purpose of the present invention is to address the shortcomings of the existing technology and provide a method and application of electric field-assisted substrate growth of titanium dioxide nanoarrays, which has a short reaction time, convenient operation, and broad application prospects. It can grow titanium dioxide nanoarrays with various morphologies on the surfaces of various substrates, including nanowires, nanoflowers and nanosheets.

[0012] The specific steps are as follows:

[0013] A method for growing titanium dioxide nanoarrays on a substrate with electric field assistance, comprising the following steps:

[0014] 1) Substrate cleaning: clean the substrate with a cleaning solution and dry it for later use;

[0015] 2) Growing a titanium dioxide nanoarray on a substrate: The substrate is fixed to a platinum electrode holder in a reaction vessel, and a titanium source is fixed to another platinum electrode holder; a reaction solution mixed with hydrogen peroxide, nitric acid, and melamine is added to the reaction vessel, and the electrode holder is connected to a DC power supply, with the positive electrode connected to the titanium source and the negative electrode connected to the substrate; a constant voltage of 20-60V is applied to the two electrode holders, and the reaction is carried out for 2-6 hours;

[0016] 3) Sample cleaning and collection: The substrate is removed from the electrode holder and ultrasonically cleaned and dried.

[0017] Furthermore, in step 1), the substrate is carbon cloth, and the cleaning process of the cleaning liquid is: alternately cleaning in ethanol and deionized water.

[0018] Furthermore, in step 1), the substrate is a titanium sheet or a titanium wire mesh, and the cleaning process of the cleaning solution is: preparing a mixture of hydrofluoric acid, nitric acid and deionized water, the mass percentage concentration of hydrofluoric acid is 50-55%, the mass percentage concentration of nitric acid is 65-68%, and the volume ratio of hydrofluoric acid: nitric acid: deionized water is 1:3:6.

[0019] Furthermore, in step 2), the amount of the reaction solution added is 60-100 ml, and the ratio of hydrogen peroxide: nitric acid: melamine: water in the reaction solution is (60-180) mmol: 60 mmol: 1 mmol: 100 ml.

[0020] Furthermore, the morphology of the titanium dioxide nanoarray is one of nanowires, nanoflowers and nanosheets.

[0021] A substrate with titanium dioxide nanoarrays grown on its surface is prepared by any one of the methods described above.

[0022] An application of the substrate is as a photocatalyst material for photocatalytic degradation of organic wastewater.

[0023] Beneficial effects:

[0024] The present invention grows titanium dioxide nanoarrays on the surfaces of various substrates by regulating the voltage, reaction time, and reaction temperature under the assistance of an electric field, combined with a specially prepared reaction solution. Nitric acid is used in the reaction solution to enhance the oxidizing property of the solution, and a titanium source is dissolved in the reaction solution. Melamine is used as a morphology controller to guide the formation of the titanium dioxide nanoarrays. This invention has simple operation, short reaction time, no need for complex equipment, and low production cost.

[0025] In addition, compared with titanium dioxide nanowires prepared by prior art, the titanium dioxide nanowire film prepared by this method has better photocatalytic degradation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a field emission scanning electron micrograph of titanium dioxide nanoparticles prepared in Example 1;

[0027] Figure 2 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 2;

[0028] Figure 3 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 3;

[0029] Figure 4 This is the X-ray diffraction pattern of the titanium dioxide nanowires prepared in Example 3;

[0030] Figure 5 This is a field emission scanning electron micrograph of the titanium dioxide nanowires prepared in Example 3 after heat treatment;

[0031] Figure 6 This is the X-ray diffraction pattern of the titanium dioxide nanowires prepared in Example 3 after heat treatment;

[0032] Figure 7 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 4;

[0033] Figure 8 Field emission scanning electron micrograph of the thickness of the titanium dioxide nanowire film prepared in Example 4;

[0034] Figure 9 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 5;

[0035] Figure 10 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 6;

[0036] Figure 11 Field emission scanning electron micrograph of the thickness of the titanium dioxide nanowire film prepared in Example 6;

[0037] Figure 12 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 7;

[0038] Figure 13 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 8;

[0039] Figure 14 Field emission scanning electron micrograph of the thickness of the titanium dioxide nanowire film prepared in Example 8;

[0040] Figure 15 This is a field emission scanning electron micrograph of titanium dioxide nano-branches prepared in Example 9;

[0041] Figure 16 Field emission scanning electron micrograph of the thickness of the titanium dioxide nanobranched film prepared in Example 9;

[0042] Figure 17 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 10;

[0043] Figure 18 This is a field emission scanning electron micrograph of titanium dioxide nanowires prepared in Example 11;

[0044] Figure 19 This is a field emission scanning electron micrograph of the titanium dioxide nanosheets prepared in Example 12;

[0045] Figure 20 This is a field emission scanning electron micrograph of the titanium dioxide nanosheets prepared in Example 13;

[0046] Figure 21 This is a field emission scanning electron micrograph of the titanium dioxide nanoflowers prepared in Example 14;

[0047] Figure 22 This is a comparison chart of the catalytic degradation curves of ofloxacin by titanium dioxide nanowires in Example 6 and the prior art. DETAILED DESCRIPTION

[0048] The following examples further illustrate the technology of growing TiO2 nanoarrays under electric field assistance of the present invention, but the present invention is not limited to the following examples.

[0049] Example 1

[0050] 1) Substrate cleaning: Mix 50-55% by mass hydrofluoric acid, 65-68% by mass nitric acid and deionized water in a volume ratio of 1:3:6 to obtain an acid cleaning solution. Clean the titanium sheet with the acid cleaning solution and then dry it for later use.

[0051] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a 2cm*2cm size and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 1h.

[0052] 3) Sample cleaning and collection: The titanium sheet was removed from the electrode holder and placed in deionized water for 10 minutes for ultrasonication, and then placed in an oven at 60°C for drying.

[0053] Figure 1 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that particles are deposited on the surface of the titanium sheet.

[0054] Example 2

[0055] 1) Substrate cleaning:

[0056] Same as Example 1.

[0057] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is a mixture of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 2h.

[0058] 3) Sample cleaning and collection:

[0059] Same as Example 1.

[0060] Figure 2 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet.

[0061] Example 3

[0062] 1) Substrate cleaning:

[0063] Same as Example 1.

[0064] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0065] 3) Sample cleaning and collection:

[0066] Same as Example 1.

[0067] 4) Heat treatment: Place the dried titanium sheet in a muffle furnace and heat treat at 450°C for 1 hour.

[0068] Figure 3 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet.

[0069] Figure 4 This is the X-ray diffraction pattern of the product obtained in step 2), from which it can be seen that the obtained product is H2Ti3O7.

[0070] Figure 5This is a field emission scanning electron micrograph of the product obtained in step 4), from which it can be seen that the morphology of the nanowires on the surface of the titanium sheet does not change significantly after heat treatment.

[0071] Figure 6 This is the X-ray diffraction pattern of the product obtained in step 4), from which it can be seen that the obtained product is TiO2.

[0072] Example 4

[0073] 1) Substrate cleaning:

[0074] Same as Example 1.

[0075] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 40V to the two electrode clamps at room temperature, and react for 3h.

[0076] 3) Sample cleaning and collection:

[0077] Same as Example 1.

[0078] Figure 7 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet.

[0079] Figure 8 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that the thickness of the nanowire film on the surface of the titanium sheet is about 1 μm.

[0080] Example 5

[0081] 1) Substrate cleaning:

[0082] Same as Example 1.

[0083] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a 2cm*2cm size and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 60V to the two electrode clamps at room temperature, and react for 1h.

[0084] 3) Sample cleaning and collection:

[0085] Same as Example 1.

[0086] Figure 9 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet.

[0087] Example 6

[0088] 1) Substrate cleaning:

[0089] Same as Example 1.

[0090] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 60ml of reaction solution (each 100ml of solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0091] 3) Sample cleaning and collection:

[0092] Same as Example 1.

[0093] Figure 10 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet.

[0094] Figure 11 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that a dense nanowire film with a thickness of about 1 μm grows on the surface of the titanium sheet.

[0095] Example 7

[0096] 1) Substrate cleaning:

[0097] Same as Example 1.

[0098] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 100ml of reaction solution (each 100ml solution is a mixture of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0099] 3) Sample cleaning and collection:

[0100] Same as Example 1.

[0101] Figure 12 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet, and the nanowires are relatively thick.

[0102] Example 8

[0103] 1) Substrate cleaning:

[0104] Same as Example 1.

[0105] 2) Growing titanium dioxide nanoarrays on a substrate: Cut the cleaned and dried titanium sheet into a size of 2cm*2cm and fix it on a platinum electrode clamp, and fix the 2cm*2cm titanium sheet on another platinum electrode clamp; add 80ml of a 3-fold diluted reaction solution (each 100ml of the solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid and 60mg of melamine) to the reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0106] 3) Sample cleaning and collection:

[0107] Same as Example 1.

[0108] Figure 13 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium sheet.

[0109] Figure 14 From the field emission scanning electron micrograph of the product obtained in step 2), it can be seen that the thickness of the nanowire film on the surface of the titanium sheet is about 1 μm.

[0110] Example 9

[0111] 1) Substrate cleaning:

[0112] Same as Example 1.

[0113] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 80ml of a 1.5-fold diluted reaction solution (each 100ml of the solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0114] 3) Sample cleaning and collection:

[0115] Same as Example 1.

[0116] Figure 15 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that a dense nano-branched structure grows on the surface of the titanium sheet.

[0117] Figure 16 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that a dense nano-branched structure film with a thickness of about 1 μm grows on the surface of the titanium sheet.

[0118] Example 10

[0119] 1) Substrate cleaning: Mix 50-55% by mass hydrofluoric acid, 65-68% by mass nitric acid and deionized water in a volume ratio of 1:3:6 to obtain an acid cleaning solution. Clean the titanium wire mesh with the acid cleaning solution and then dry it for later use.

[0120] 2) Growing titanium dioxide nanoarrays on a substrate: Cut the cleaned and dried titanium wire mesh into a size of 2cm*2cm and fix it to a platinum electrode clamp, and fix a titanium sheet of 2cm*2cm on another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is composed of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid and 60mg of melamine) to the reaction vessel, connect the electrode clamp to a DC power supply, with the positive electrode connected to the titanium sheet and the negative electrode connected to the titanium wire mesh; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0121] 3) Sample cleaning and collection: The titanium mesh was removed from the electrode holder and placed in deionized water for 10 minutes for ultrasonication, and then placed in an oven for drying at 60°C.

[0122] Figure 17 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanowires grow on the surface of the titanium mesh.

[0123] Example 11

[0124] 1) Substrate cleaning: The carbon cloth was washed alternately in ethanol and deionized water three times, and then dried in an oven at 60°C for later use.

[0125] 2) Growing titanium dioxide nanoarrays on a substrate: Cut the cleaned and dried carbon cloth into a size of 2cm*2cm and fix it on a platinum electrode clamp, and fix a titanium sheet of 2cm*2cm on another platinum electrode clamp; add 80ml of reaction solution (each 100ml of solution is a mixture of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid and 60mg of melamine) to the reaction vessel, connect the electrode clamp to a DC power supply, with the positive electrode connected to the titanium sheet and the negative electrode connected to the carbon cloth; apply a constant voltage of 20V to the two electrode clamps at room temperature, and react for 3h.

[0126] 3) Sample cleaning and collection: The carbon cloth was removed from the electrode holder and placed in deionized water for 10 min for ultrasonication, and then placed in an oven at 60°C for drying.

[0127] Figure 18 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that nanowires grow on the surface of the carbon cloth.

[0128] Example 12

[0129] 1) Substrate cleaning: Mix 50-55% by mass hydrofluoric acid, 65-68% by mass nitric acid and deionized water in a volume ratio of 1:3:6 to obtain an acid cleaning solution. Clean the titanium sheet with the acid cleaning solution and then dry it for later use.

[0130] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 3 cm*3 cm and fix it to a platinum sheet electrode clamp, and fix a titanium rod with a diameter of 6 mm and a length of 100 mm to another platinum sheet electrode clamp; add 90 ml of reaction solution (each 100 ml of solution is a mixture of 98 ml of 30% hydrogen peroxide, 2 ml of 65-68% nitric acid, and 60 mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, connect the positive electrode to the titanium rod, and the negative electrode to the titanium sheet; apply a constant voltage of 20 V to the two electrode clamps, place the reaction vessel in a constant temperature water bath at 70°C, and react for 6 hours.

[0131] 3) Sample cleaning and collection: The titanium sheet was removed from the electrode holder and placed in deionized water for ultrasonic treatment for 5-10 minutes, and then placed in an oven at 60°C for drying.

[0132] Figure 19 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanosheets grow on the surface of the titanium sheet.

[0133] Example 13

[0134] 1) Substrate cleaning: Mix 50-55% by mass hydrofluoric acid, 65-68% by mass nitric acid and deionized water in a volume ratio of 1:3:6 to obtain an acid cleaning solution. Clean the titanium sheet with the acid cleaning solution and then dry it for later use.

[0135] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a size of 3 cm*3 cm and fix it to a platinum sheet electrode clamp, and fix a titanium rod with a diameter of 6 mm and a length of 100 mm to another platinum sheet electrode clamp; add 90 ml of reaction solution (each 100 ml of solution is a mixture of 98 ml of 30% hydrogen peroxide, 2 ml of 65-68% nitric acid, and 60 mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, connect the positive electrode to the titanium rod, and the negative electrode to the titanium sheet; apply a constant voltage of 20 V to the two electrode clamps, place the reaction vessel in a constant temperature water bath at 80°C, and react for 6 hours.

[0136] 3) Sample cleaning and collection: The titanium sheet was removed from the electrode holder and placed in deionized water for ultrasonic treatment for 5-10 minutes, and then placed in an oven at 60°C for drying.

[0137] Figure 20 This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that dense nanosheets grow on the surface of the titanium sheet.

[0138] Example 14

[0139] 1) Substrate cleaning: Mix 50-55% by mass hydrofluoric acid, 65-68% by mass nitric acid and deionized water in a volume ratio of 1:3:6 to obtain an acid cleaning solution. Clean the titanium sheet with the acid cleaning solution and then dry it for later use.

[0140] 2) Growing titanium dioxide nanoarrays on a substrate: Cut a cleaned and dried titanium sheet into a 2cm*2cm size and fix it to a platinum electrode clamp, and fix a 2cm*2cm titanium sheet to another platinum electrode clamp; add 90ml of reaction solution (each 100ml of solution is a mixture of 98ml of 30% hydrogen peroxide, 2ml of 65-68% nitric acid, and 60mg of melamine) to a reaction vessel, connect the electrode clamp to a DC power supply, and connect both the positive and negative electrodes to the titanium sheet; apply a constant voltage of 20V to the two electrode clamps, place the reaction vessel in a constant temperature water bath at 90°C, and react for 6h.

[0141] 3) Sample cleaning and collection: The titanium sheet was removed from the electrode holder and placed in deionized water for ultrasonic treatment for 5-10 minutes, and then placed in an oven at 60°C for drying.

[0142] Figure 21This is a field emission scanning electron micrograph of the product obtained in step 2), from which it can be seen that nanoflowers grow on the surface of the titanium sheet.

[0143] Photocatalytic performance test:

[0144] The titanium sheet prepared in Example 6 was used to prepare a simulated pharmaceutical wastewater solution of ofloxacin with a concentration of 20 ppm. After dark adsorption equilibrium, the degradation reaction was initiated under ultraviolet light irradiation and stirring. Samples were taken every 1 h, and the residual concentration of the solution was measured by liquid chromatography to test the photocatalytic performance of the titanium sheet.

[0145] Figure 22 The graphs for the photocatalytic degradation of ofloxacin by titanium dioxide nanowires prepared according to patent number CN200910096796.4 (gray curve) are shown. It can be seen that the nano-titanium dioxide prepared by the present invention has significant photocatalytic degradation performance for organic wastewater, outperforming the titanium dioxide film prepared according to the patent.

Claims

1. A method for growing titanium dioxide nanoarrays on an electric field-assisted substrate, characterized in that: Here are the steps: 1) Substrate cleaning: clean the substrate with a cleaning solution and dry it for later use; 2) Growing a titanium dioxide nanoarray on a substrate: The substrate is fixed to a platinum electrode holder in a reaction vessel, and a titanium source is fixed to another platinum electrode holder; a reaction solution mixed with hydrogen peroxide, nitric acid, and melamine is added to the reaction vessel, and the electrode holder is connected to a DC power supply, with the positive electrode connected to the titanium source and the negative electrode connected to the substrate; a constant voltage of 20-60V is applied to the two electrode holders, and the reaction is carried out for 2-6 hours; 3) Sample cleaning and collection: The substrate is removed from the electrode holder and ultrasonically cleaned and dried.

2. The method for growing titanium dioxide nanoarrays on an electric field assisted substrate according to claim 1, characterized in that: The substrate is carbon cloth, and the cleaning process of the cleaning solution is: cleaning in ethanol and deionized water alternately.

3. The method for growing titanium dioxide nanoarrays on an electric field assisted substrate according to claim 1, characterized in that: In step 1), the substrate is a titanium sheet or a titanium wire mesh, and the cleaning process of the cleaning solution is as follows: preparing a mixture of hydrofluoric acid, nitric acid and deionized water, wherein the mass percentage concentration of hydrofluoric acid is 50-55%, the mass percentage concentration of nitric acid is 65-68%, and the volume ratio of hydrofluoric acid: nitric acid: deionized water is 1:3:

6.

4. The method for growing titanium dioxide nanoarrays on an electric field assisted substrate according to claim 1, characterized in that: In step 2), the amount of the reaction solution added is 60-100 ml, and the ratio of hydrogen peroxide: nitric acid: melamine: water in the reaction solution is (60-180) mmol: 60 mmol: 1 mmol: 100 ml.

5. The method for growing titanium dioxide nanoarrays on an electric field assisted substrate according to claim 1, wherein: The morphology of the titanium dioxide nanoarray is one of nanowires, nanoflowers and nanosheets.

6. A substrate having a titanium dioxide nanoarray grown on its surface, characterized in that: The substrate is prepared by the method according to any one of claims 1 to 5.

7. Use of the substrate according to claim 6, characterized in that: Used as a photocatalyst material for photocatalytic degradation of organic wastewater.

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