A copper-doped TiO2 electro-Fenton cathode incorporating an amorphous / crystalline heterojunction, its preparation method, and its application.

Abstract

This invention discloses a copper-doped TiO2 electro-Fenton cathode with an amorphous / crystalline heterojunction, its preparation method, and its application. The amorphous / crystalline heterojunction is formed by in-situ growth of titanium dioxide nanosheets on the substrate electrode surface via hydrothermal method, followed by doping and annealing. The amorphous interface formed by this invention exhibits stronger interfacial stress, increases the number and stability of unsaturated copper sites, and enhances the catalytic activity of the electrode through the construction of the amorphous / crystalline heterojunction, thereby enabling the electro-Fenton reaction at the cathode to proceed continuously and efficiently over a wide pH range.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a copper-doped TiO2 electric Fenton cathode with an amorphous / crystalline heterojunction, its preparation method, and its application. Background Technology

[0002] With the development of chemical, agricultural, and pharmaceutical industries in recent years, emerging organic pollutants in water bodies have become a major concern in the environmental field. Currently, the electro-Fenton process is considered one of the most effective methods for degrading organic pollutants in water. Its most significant feature is the in-situ reduction of oxygen at the cathode to generate hydrogen peroxide, which further reacts to generate hydroxyl radicals (·OH), which degrade organic matter. For the continuous generation of ·OH, the hydrogen peroxide activation sites in the system need to be in an effective state. However, regardless of whether it is a homogeneous or heterogeneous reaction, the exposed hydrogen peroxide activation sites (such as Fe...)... 2+ It is highly susceptible to OH under neutral conditions. - The presence of oxidizing agents leads to a lack of oxidizing sites, hindering the continuous generation of ·OH. While continuously adding acid to the system can inhibit the formation of (hydro)oxide precipitates, this not only corrodes equipment but also requires pH adjustment of the treated wastewater before discharge, potentially generating hazardous iron sludge and significantly increasing wastewater treatment costs. Therefore, constructing a cathode electro-Fenton catalyst with a wide pH range, especially improving the catalytic activity of the hydrogen peroxide activation sites, is of significant environmental importance.

[0003] The construction of amorphous / crystalline heterojunctions holds promise for modulating the electronic properties of peroxide catalytic sites, with the aim of weakening OH-. - Adsorption. In particular, the interface between amorphous materials and heterojunctions possesses abundant defects and dangling bonds, enabling simultaneous surface- and volume-confined electrocatalysis. This promises to increase the number of coordination-unsaturated catalytic sites and optimize the catalytic process. Furthermore, structurally flexible amorphous electrocatalysts can self-regulate and withstand structural disturbances during electrocatalysis, typically exhibiting better corrosion resistance. However, while amorphous materials offer high performance, pure amorphous materials suffer from poor stability. To achieve a balance between stability and activity, amorphous / crystalline heterojunctions must be constructed. Titanium dioxide is commonly used to construct amorphous / crystalline heterojunctions and can also be used to generate hydrogen peroxide, serving as an excellent substrate for electro-Fenton oxygen reduction to hydrogen peroxide. Existing titanium dioxide amorphous / crystalline heterojunctions suffer from uneven loading on the substrate electrode, resulting in fewer coordination-unsaturated catalytic sites and thus weakening their catalytic performance.

[0004] Therefore, constructing amorphous / crystalline titanium dioxide heterostructures to increase and improve the activity of unsaturated metal activation sites is expected to synthesize highly efficient electro-Fenton cathodes suitable for a wide pH range, but there are few reports on this. Summary of the Invention

[0005] To overcome the shortcomings of the existing technologies, this invention provides a copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction and its preparation method, aiming to solve the problem of narrow pH applicability of traditional catalysts and achieve low-cost and high-efficiency pollutant degradation. This invention also provides a green and efficient synthesis method for the copper-doped TiO2 Fenton cathode with the amorphous / crystalline heterojunction, and provides its application in the degradation of organic pollutants.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] The present invention first provides a copper-doped TiO2 electric Fenton cathode with an amorphous / crystalline heterojunction, characterized in that: the electric Fenton cathode includes a base electrode and a copper-doped TiO2 amorphous / crystalline heterojunction loaded on the base electrode.

[0008] Furthermore, the substrate electrode is one of hydrophilic graphite plate, activated carbon fiber, carbon felt, and graphite felt electrode.

[0009] Furthermore, the copper-doped TiO2 amorphous / crystalline heterojunction is grown in situ on the surface of the substrate electrode.

[0010] As a general technical concept, the present invention also provides a method for preparing the copper-doped TiO2 electric Fenton cathode with the aforementioned amorphous / crystalline heterojunction, comprising the following steps:

[0011] S1. Mix tetrabutyl titanate, water and hydrochloric acid and stir until homogeneous. Then add ammonium fluorotitanate and copper salt to the solution to obtain the precursor solution.

[0012] S2. Place the base electrode in the precursor solution and perform a constant temperature hydrothermal reaction and a vacuum annealing reaction in sequence. After the reaction is completed, remove and wash the electrode to obtain a copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction.

[0013] Furthermore, in step S1, the volume ratio of tetrabutyl titanate, water, and hydrochloric acid is 1:35:25, the mass concentration of hydrochloric acid is 37%, and the ratio of the total volume of tetrabutyl titanate, water, and hydrochloric acid to ammonium fluorotitanate and copper salt is 60ml:0.5g:0.1g.

[0014] Furthermore, in step S1, the copper salt is one of copper chloride, copper nitrate, copper sulfate, and copper acetylacetonate.

[0015] Furthermore, in step S2: the temperature of the constant temperature hydrothermal reaction is 150-180℃ and the reaction time is 16-20h; the temperature of the vacuum annealing reaction is 220-250℃ and the annealing time is 2-5h.

[0016] The principle of this invention is as follows: Introducing an amorphous / crystalline heterojunction copper-doped TiO2 electro-Fenton cathode can simultaneously achieve the generation and activation of hydrogen peroxide. During the reaction, hydrogen peroxide is generated from the two-electron reduction process of oxygen at the cathode, eliminating the need to add additional hydrogen peroxide to the system. The hydrogen peroxide is generated from titanium dioxide and then migrates to the abundant unsaturated copper sites on the surface and in the bulk phase, where it decomposes to produce hydroxyl radicals. The cathode provides electrons during this process, ensuring the continuous conduction of the electro-Fenton reaction. In the amorphous / crystalline heterojunction electro-Fenton cathode, the unsaturated copper sites on the surface and in the bulk phase interact strongly with the substrate amorphous / crystalline titanium dioxide heterojunction, enhancing catalyst stability. Simultaneously, the coordination effect enhances the covalent nature of the copper sites, strengthening their resistance to interference from hydroxide ions in the system, thus enabling the cathode electro-Fenton reaction to proceed continuously and efficiently over a wide pH range.

[0017] As a general technical concept, this invention also provides an application of the copper-doped TiO2 Fenton cathode with introduced amorphous / crystalline heterojunction in degrading organic pollutants such as antibiotics in water under acidic to neutral conditions. The specific method is as follows: the copper-doped TiO2 Fenton cathode with introduced amorphous / crystalline heterojunction is connected to the anode to form a circuit, and a supporting electrolyte of 40-50 mmol / L is added. The organic matter is mineralized and degraded under constant current conditions in an acidic to neutral system (pH = 3.0-7.0).

[0018] Furthermore, the anode material is one of a ruthenium-iridium coated electrode on a titanium substrate, a boron-doped diamond electrode, and a platinum electrode; the supporting electrolyte is one of sodium sulfate and potassium sulfate; and the current control range is 20-50 mA.

[0019] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0020] (1) This invention achieves the generation and activation of hydrogen peroxide by loading copper-doped TiO2 amorphous / crystalline heterojunction on the surface of substrate electrodes such as graphite felt, and avoids the need to add additional catalyst in the solution system, thus avoiding subsequent catalyst recovery and easily realizing the degradation of organic pollutants.

[0021] (2) This invention provides a method for preparing a copper-doped TiO2 electro-Fenton cathode with an amorphous / crystalline heterojunction. A substrate electrode, such as graphite felt, which has good inherent stability, is used as the carrier. Titanium dioxide is loaded onto the cathode surface in the form of nanosheets, resulting in a stable structure. The amorphous interface formed by direct copper doping has stronger interfacial stress, increasing the number of unsaturated copper sites and improving stability. Although amorphous materials have high performance, pure amorphous materials have poor stability. To achieve a balance between stability and activity, an amorphous / crystalline heterojunction is constructed, which has stronger catalytic activity, allowing the electro-Fenton reaction at the cathode to proceed continuously and efficiently over a wide pH range.

[0022] (3) In this invention, titanium dioxide and copper salt are widely available, cheap and easy to obtain. Essentially, the low coordination and high activity sites formed by the amorphous / crystalline composite structure of titanium dioxide enhance the catalytic activity, achieving its efficient electro-Fenton activity. Moreover, the raw materials are non-toxic and harmless, with low potential environmental risks. Attached Figure Description

[0023] Figure 1 This is a SEM image of the copper-doped TiO2 electric Fenton cathode with an amorphous / crystalline heterojunction prepared in Example 1 of the present invention.

[0024] Figure 2 The X-ray diffraction pattern is shown for the copper-doped TiO2 electric Fenton cathode with an amorphous / crystalline heterojunction prepared in Example 1 of this invention.

[0025] Figure 3 The X-ray diffraction pattern of the titanium dioxide cathode prepared for Comparative Example 1.

[0026] Figure 4 This is a SEM image of copper-doped TiO2 crystals obtained at an annealing temperature of 550°C in Example 2 of the present invention.

[0027] Figure 5 The image shows the X-ray diffraction pattern of copper-doped TiO2 crystals obtained at an annealing temperature of 550°C in Example 2 of this invention.

[0028] Figure 6 This is a comparison chart of the effects of each group of electro-Fenton cathodes on the degradation of Rhodamine B in Example 3 of the present invention.

[0029] Figure 7 This is a comparison of the effects of copper-doped TiO2 electro-Fenton cathodes with amorphous / crystalline heterojunctions introduced in Example 4 of the present invention on the degradation of Rhodamine B at different pH values. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] The materials and instruments used in the following examples are all commercially available.

[0032] Comparative Example 1: Preparation of TiO2 Electrode

[0033] The TiO2 electrode in this comparative example was prepared according to the following steps:

[0034] Tetrabutyl titanate, water, and 37% hydrochloric acid were mixed in a volume ratio of 1:35:25 to prepare a 60 mL solution, which was stirred for 15 min. Then, 0.5 g of ammonium fluorotitanate was added, and the mixture was stirred for 10 min to obtain a precursor solution. Graphite felt was immersed in the above precursor solution and then placed in a hydrothermal reactor for a constant temperature hydrothermal reaction at 158 ​​°C for 16 h. After the reaction was completed, the material was removed and washed to remove unreacted impurities, dried for 12 h, and finally annealed at 550 °C under vacuum for 2 h to obtain a TiO2 electrode.

[0035] Example 1: Preparation of a copper-doped TiO2 electro-Fenton cathode with an amorphous / crystalline heterojunction

[0036] This embodiment provides a copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction, which uses graphite felt as the substrate electrode and has a copper-doped TiO2 amorphous / crystalline heterojunction loaded on its surface. The specific preparation method is as follows:

[0037] Tetrabutyl titanate, water, and 37% hydrochloric acid were mixed in a volume ratio of 1:35:25 to prepare a 60 mL solution, which was stirred for 15 min. Then, 0.5 g of ammonium fluorotitanate and 100 mg of copper acetylacetonate were added, and the mixture was stirred for 10 min to obtain a precursor solution. Graphite felt was immersed in the above precursor solution and then placed in a hydrothermal reactor for a constant temperature hydrothermal reaction at 158 ​​°C for 16 h. After the reaction, the solution was removed and washed to remove unreacted impurities, dried for 12 h, and finally annealed at 250 °C under vacuum for 2 h to obtain a copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction.

[0038] Figure 1 This is a SEM image of the copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction prepared in this embodiment. Figure 1 A uniform amorphous layer can be clearly seen on the surface of the titanium dioxide nanosheets, proving that the copper-doped TiO2 amorphous / crystalline heterojunction is uniformly loaded on the carbon fiber.

[0039] Figure 2 and Figure 3 The images show the X-ray diffraction patterns of the copper-doped TiO2 electric Fenton cathode with an amorphous / crystalline heterojunction prepared in this embodiment and the TiO2 electrode prepared in Comparative Example 1, respectively. The comparison shows that, compared to the titanium dioxide electrode, the crystallinity of the copper-doped TiO2 electric Fenton cathode with an amorphous / crystalline heterojunction prepared in this embodiment is reduced, indicating that some crystals have transformed into amorphous material, forming an amorphous / crystalline TiO2 heterojunction.

[0040] Example 2: Effect of annealing temperature on amorphous / crystalline heterojunctions

[0041] In this embodiment, a copper-doped TiO2 Fenton cathode was prepared using the same method as in Example 1, except that the annealing temperature was adjusted from 250°C to 550°C.

[0042] Figure 4 and Figure 5 The images shown are SEM images and X-ray diffraction patterns of copper-doped TiO2 obtained at an annealing temperature of 550℃ in this embodiment. It can be seen that crystallization and agglomeration occur after annealing at 550℃, the amorphous heterojunction is removed, and the crystallinity is greatly increased, forming copper-doped titanium dioxide, which leads to a decrease in its performance.

[0043] Example 3: Application of copper-doped TiO2 electro-Fenton cathode with amorphous / crystalline heterojunction in the degradation of Rhodamine B under neutral conditions.

[0044] A reactor was set up, and the copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction prepared in Example 1, the TiO2 electrode prepared in Comparative Example 1, and the copper-doped crystalline TiO2 cathode prepared in Example 2 were connected to a ruthenium-iridium coated anode on a titanium substrate to form a circuit within the reactor. Inside the reactor, 20 mg of Rhodamine B was dissolved in 1000 mL of water (without pH adjustment, the system pH was 7.0), and sodium sulfate was added to bring the concentration to 50 mmol / L. The Rhodamine B solution was degraded under a current of 25 mA.

[0045] The degradation results of the system are as follows Figure 6 As shown, the copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction achieves 100% Rhodamine B degradation after 50 minutes of reaction. In contrast, the titanium dioxide-loaded graphite felt of Comparative Example 1 achieves less than 10% Rhodamine B degradation after 50 minutes. The copper-doped crystalline TiO2 cathode of Example 2 achieves only about 50% Rhodamine B degradation after 50 minutes of reaction.

[0046] Example 4: Application of copper-doped TiO2 electro-Fenton cathode with amorphous / crystalline heterojunction in degrading Rhodamine B under different pH conditions.

[0047] A reactor was set up, and the copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction prepared in Example 1 was connected to a ruthenium-iridium coated anode on a titanium substrate to form a circuit within the reactor. Inside the reactor, 20 mg of Rhodamine B was dissolved in 1000 mL of water (the pH of the solution was adjusted to 3.0 with hydrochloric acid), and sodium sulfate was added to bring the concentration to 50 mmol / L. The Rhodamine B solution was degraded under a current of 25 mA.

[0048] The degradation results of the system are as follows Figure 7As shown, it can be seen that the copper-doped TiO2 electro-Fenton cathode with the introduction of amorphous / crystalline heterojunction can achieve 100% Rhodamine B degradation after 50 min under pH conditions of 3.0 and 7.0.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A copper-doped TiO2 Fenton cathode incorporating an amorphous / crystalline heterojunction, characterized in that: The electric Fenton cathode includes a substrate electrode and a copper-doped TiO2 amorphous / crystalline heterojunction grown in situ on the substrate electrode; the method for preparing the electric Fenton cathode includes the following steps: S1. Mix tetrabutyl titanate, water and hydrochloric acid and stir until homogeneous, then add ammonium fluorotitanate and copper salt to obtain a precursor solution; S2. The substrate electrode is placed in the precursor solution and subjected to a constant-temperature hydrothermal reaction and a vacuum annealing reaction in sequence. After the reaction is completed, it is removed and washed to obtain a copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction. The temperature of the constant-temperature hydrothermal reaction is 150-180℃ and the reaction time is 16-20h. The temperature of the vacuum annealing reaction is 220-250℃ and the annealing time is 2-5h.

2. The copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction as described in claim 1, characterized in that: The substrate electrode is one of hydrophilic graphite plate, activated carbon fiber, carbon felt, and graphite felt electrode.

3. The copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction as described in claim 1, characterized in that: In step S1, the volume ratio of tetrabutyl titanate, water and hydrochloric acid is 1:35:25, the mass concentration of hydrochloric acid is 37%, and the ratio of the total volume of tetrabutyl titanate, water and hydrochloric acid to ammonium fluorotitanate and copper salt is 60mL:0.5g:0.1g.

4. The copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction as described in claim 1, characterized in that: In step S1, the copper salt is one of copper chloride, copper nitrate, copper sulfate, and copper acetylacetonate.

5. The application of a copper-doped TiO2 Fenton cathode with an amorphous / crystalline heterojunction as described in any one of claims 1 to 2, characterized in that: Used for electro-Fenton degradation of organic pollutants in water under pH conditions of 3.0-7.

0.

6. The application according to claim 5, characterized in that: The copper-doped TiO2 electro-Fenton cathode and anode, which are introduced into an amorphous / crystalline heterojunction, form a circuit, and an additional 40-50 mmol / L supporting electrolyte is added to mineralize and degrade organic pollutants in water under constant current conditions.

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