Preparation method of Ti3C2 MXene / CdTiO3 heterojunction photocatalyst

Abstract

The present invention discloses a method for preparing a Ti3C2MXene / CdTiO3 heterojunction photocatalyst. The present invention adopts EDTA complexation and solvent thermal method to prepare Ti3C2MXene / CdTiO3 heterojunction photocatalyst. A soluble cadmium salt and a complexing agent are added to deionized water to obtain an EDTA-Cd solution, which is added to an ethanol solution of tetrabutyl titanate under magnetic stirring. After uniform stirring, the pH of the solution is adjusted with sodium hydroxide, and then Ti3C2MXene is added. A solvent thermal reaction is then carried out to obtain a Ti3C2MXene / CdTiO3 heterojunction photocatalyst with good visible light catalytic performance. The photocatalyst obtained by the method of the present invention can achieve a degradation rate of 76% for rhodamine B in water under visible light. Ti3C2MXene / CdTiO3 makes up for the shortcomings of CdTiO3, such as large band gap, ultraviolet light response, and low photocatalytic activity. In addition, Ti3C2MXene / CdTiO3 has good stability and can still maintain good catalytic activity and stability after five cycles of degradation. The method of the invention is economical, green and has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst. Background Art

[0002] Photocatalysis is an eco-friendly, low-carbon technology with significant application prospects in addressing environmental pollution and energy crises. The industrial application of photocatalysis relies on the development of efficient, economical, and environmentally friendly catalysts. The catalytic activity of semiconductor photocatalysts is closely related to the generation and separation of photogenerated carriers. Given that most unit semiconductors suffer from shortcomings such as rapid recombination rates of photogenerated carriers, low photocatalytic activity, and a narrow photoresponse range, surface-interface regulation techniques can be used to control the band structure, bonding type, and contact area of ​​the interface, accelerating the transfer of photogenerated charge carriers and thereby yielding high-performance catalysts.

[0003] Perovskite cadmium titanate (CdTiO3) is an n-type wide-bandgap semiconductor oxide with excellent dielectric, sensing and optical properties [4–7] and is widely used in gas sensors, electronic components, communication optical fibers, etc. Since CdTiO3 does not have ferroelectricity at room temperature, it has not been studied in depth. In addition, due to the large band gap of pure CdTiO3, it can only be excited by ultraviolet light to drive photocatalytic reactions, and the rapid recombination of electrons and holes in CdTiO3 leads to weak valence band hole oxidation ability, which greatly limits its application in photocatalysis. The use of highly conductive materials and photocatalyst loading is an effective method to achieve rapid transport of photoexcited electrons. Two-dimensional transition metal carbide Ti3C2T X MXenes (T represents surface functional groups such as -O, -OH and -F) have good metallic conductivity, hydrophilicity, high specific area and excellent visible light adsorption performance. They have been used as co-catalysts and combined with photocatalysts such as oxides, sulfides and phosphides to construct heterojunctions. They are widely used in the fields of photocatalytic environmental purification and energy conversion.

[0004] Utilizing the technical strategy of constructing heterojunctions, CdTiO3-based heterostructures can effectively suppress electron-hole pair recombination, thereby improving photocatalytic performance. However, CdTiO3-based heterostructure photocatalysts commonly prepared by physical methods such as ball milling and spin coating suffer from weak van der Waals forces, resulting in a small heterojunction interface and weak interactions. Therefore, developing a novel Ti3C2 MXene / CdTiO3 photocatalyst that improves photocatalytic efficiency and suppresses photogenerated carrier recombination has significant research value and application prospects. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art, namely, the large band gap, ultraviolet light drive, low catalytic efficiency, toxic raw material CdO, and high synthesis temperature of existing CdTiO photocatalysts, and to provide a method for preparing a Ti3C2MXene / CdTiO3 heterojunction photocatalyst. The present invention adopts EDTA complexation and solvothermal methods for preparation. An EDTA-Cd solution is obtained by adding a soluble cadmium salt and a complexing agent, EDTA-2Na, to deionized water. The EDTA-Cd solution is then added to an ethanol solution of tetrabutyl titanate under magnetic stirring. After uniform stirring, the pH of the solution is adjusted with sodium hydroxide, and Ti3C2MXene is added. A solvothermal reaction is then carried out to obtain a Ti3C2MXene / CdTiO3 heterojunction photocatalyst having good visible light catalytic performance. The photocatalyst obtained by the method of this invention achieves a degradation rate of 76% for rhodamine B in water under visible light. Ti3C2MXene / CdTiO3 overcomes the shortcomings of CdTiO3, such as its wide bandgap, UV light response, and low photocatalytic activity. Furthermore, Ti3C2MXene / CdTiO3 exhibits good stability, maintaining good catalytic activity and stability after five cycles of degradation. This method of this invention is economical, environmentally friendly, and has promising prospects for industrial application.

[0006] It should be noted that Ti3C2 MXene is a carbon-based nanomaterial used to replace expensive metals. Due to its unique properties, such as a layered structure, high metallic conductivity, large specific surface area, and abundant surface functional groups, Ti3C2 MXene is considered a promising photocatalytic co-catalyst. Generally, the primary function of Ti3C2 MXene in composite photocatalysts is considered to be a photogenerated electron acceptor, promoting the separation of photogenerated charges through a Schottky barrier.

[0007] The present invention uses a solvothermal method to synthesize a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst using soluble cadmium salt, EDTA-2Na, tetrabutyl titanate, and Ti3AlC2 as raw materials. The synthesized Ti3C2 MXene / CdTiO3 heterojunction photocatalyst exhibits good photocatalytic performance under visible light irradiation.

[0008] In order to achieve the above technical effects, the following technical solutions are adopted:

[0009] A method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst comprises the following steps:

[0010] Step S1: Ti3AlC2 is subjected to hydrofluoric acid ultrasonic etching to remove the Al layer, and black layered Ti3C2 MXene is obtained by filtration, washing, and drying;

[0011] Step S2: Accurately weighing a soluble cadmium salt, grinding it, and then dissolving it in deionized water; adding EDTA-2Na·4H2O to the soluble cadmium salt solution, and stirring the mixed solution at room temperature to obtain a clear and transparent EDTA-Cd solution;

[0012] Step S3: Tetrabutyl titanate is added to a solution of anhydrous ethanol and glacial acetic acid, and the clear and transparent EDTA-Cd solution obtained in step S2 is added dropwise under stirring, and NaOH is added to adjust the pH of the solution. The Ti3C2MXene obtained in step S1 is added thereto under stirring, and stirred until the mixture is uniform, and then a solvent thermal reaction is carried out. After the reaction is completed, the mixture is naturally cooled to room temperature and then filtered and washed. The obtained product is treated with HCl solution, washed until neutral, and dried to obtain a Ti3C2MXene / CdTiO3 heterojunction photocatalyst with high photocatalytic performance.

[0013] Furthermore, the concentration of hydrofluoric acid in step S1 is 40%, and the ultrasonic etching treatment time is 24 hours.

[0014] Furthermore, the grinding time in step S2 is 15 minutes; and the molar ratio of the soluble cadmium salt to the complexing agent EDTA-2Na·4H2O is 1:1.

[0015] Furthermore, the soluble cadmium salt in step S2 is one of cadmium nitrate, cadmium chloride and cadmium acetate.

[0016] Furthermore, the washing condition in step S3 is to wash the mixture alternately with deionized water and anhydrous ethanol for several times until the pH value is 7. The drying temperature in step S3 is 80° C. and the drying time is 12 hours.

[0017] Furthermore, in step S3, the molar ratio of EDTA-Cd, tetrabutyl titanate, and Ti3C2 MXene is 10:9:1, the solvothermal reaction temperature is 180° C., and the solvothermal reaction time is 12 h.

[0018] Furthermore, the stirring time in step S3 is 15 min; the concentration of the NaOH solution is 1.0 mol·L -1 .

[0019] Furthermore, the specific method of treating the HCl solution in step S3 is: filtering and washing the filter cake of the obtained product with 1 mol·L -1 Soak in HCl solution for 30 minutes, dry at 80°C, and dry for 12 hours.

[0020] Furthermore, the washing condition in step S3 is to wash the mixture alternately with deionized water and anhydrous ethanol for several times until the pH value is 7. The drying temperature in step S3 is 80° C. and the drying time is 12 hours.

[0021] Furthermore, the CdTiO3 in the Ti3C2 MXene / CdTiO3 heterojunction photocatalyst is a uniformly sized nanoparticle with a particle size of 30 to 35 nm, making it a nanocomposite material with a stable structure and excellent dispersion properties. The Ti3C2 MXene / CdTiO3 heterojunction has a visible light response range of 400 to 800 nm, demonstrating excellent visible light photocatalytic performance in dye degradation.

[0022] The Ti3C2 MXene / CdTiO3 heterojunction photocatalyst obtained by the above preparation method is applied to the visible light catalytic degradation of dyes in water.

[0023] The beneficial effects of the present invention are:

[0024] 1) The Ti3C2 MXene / CdTiO3 heterojunction photocatalyst of the present invention has the characteristics of stable structure and good dispersibility, which is conducive to the transmission of electrons and has good performance in the visible light catalytic degradation of dyes in water.

[0025] 2) The preparation method of the present invention is simple and low-cost. The prepared Ti3C2 MXene / CdTiO3 heterojunction photocatalyst has good photocatalytic degradation performance of dyes under visible light irradiation, and can degrade 10 mg·L -1 The degradation rate of rhodamine B was 76%.

[0026] 3) The Ti3C2 MXene / CdTiO3 heterojunction photocatalyst of the present invention has high stability and can still maintain a good catalytic effect after five cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order 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 use in the embodiments or the description of the prior art. The drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1 is the XRD spectrum of the Ti3C2 MXene / CdTiO3 heterojunction photocatalyst prepared in the example;

[0029] Figure 2 FT-IR image of Ti3C2 MXene prepared in the example;

[0030] Figure 3 FT-IR image of Ti3C2 MXene / CdTiO3 prepared in the example;

[0031] Figure 4 XPS survey graphs of CdTiO3, Ti3C2 MXene and Ti3C2 MXene / CdTiO3 prepared in the examples;

[0032] Figure 5 The XPS high-resolution spectra of Cd 3d of CdTiO3 and Ti3C2 MXene / CdTiO3 prepared in the examples;

[0033] Figure 6 XPS high-resolution spectra of Ti 2p of CdTiO3, Ti3C2 MXene and Ti3C2 MXene / CdTiO3 prepared in the examples;

[0034] Figure 7 The XPS high-resolution spectra of O1s of CdTiO3 and Ti3C2 MXene / CdTiO3 prepared in the examples;

[0035] Figure 8 The XPS high-resolution spectra of C 1s of CdTiO3, Ti3C2 MXene and Ti3C2 MXene / CdTiO3 prepared in the examples are shown;

[0036] Figure 9 This is the SEM image of the Ti3C2 MXene / CdTiO3 heterojunction photocatalyst prepared in the example;

[0037] Figure 10 UV-vis DRS graph of Ti3C2 MXene / CdTiO3 prepared in the example;

[0038] Figure 11 Graph showing the energy band calculation results of Ti3C2 MXene / CdTiO3 prepared in the examples;

[0039] Figure 12 This is the transient photocurrent response curve of Ti3C2 MXene / CdTiO3 prepared in the example;

[0040] Figure 13 This is the electrochemical impedance spectroscopy of Ti3C2 MXene / CdTiO3 prepared in the example;

[0041] Figure 14 This is the degradation curve of RhB dye by Ti3C2 MXene / CdTiO3 prepared in the example under visible light irradiation;

[0042] Figure 15 This is the degradation curve of RhB dye by Ti3C2 MXene / CdTiO3 prepared in the example under ultraviolet light irradiation;

[0043] Figure 16 This is a bar graph showing the photocatalytic cycle stability of Ti3C2 MXene / CdTiO3 prepared in the examples under visible light irradiation;

[0044] Figure 17 DMPO-·O2 of Ti3C2 MXene / CdTiO3 and CdTiO3 prepared in the examples - EPR spectrum of

[0045] Figure 18 EPR spectra of DMPO-·OH of Ti3C2 MXene / CdTiO3 and CdTiO3 prepared in the examples;

[0046] Figure 19 is a Mott-Schottky curve diagram of CdTiO3 prepared in the embodiment;

[0047] Figure 20 Schematic diagram of the photocatalytic degradation mechanism of RhB under visible light by Ti3C2 MXene / CdTiO3 prepared in the example. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0049] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations and / or combinations thereof.

[0051] Example 1:

[0052] This embodiment provides a method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst with good visible light catalytic performance, comprising the following steps:

[0053] Preparation of Ti3C2 MXene: Use traditional hydrofluoric acid etching Ti3AlC2 to prepare Ti3C2 MXene:

[0054] 1g of Ti3AlC2 powder was added to a plastic beaker, which was then placed in a larger beaker filled with cold water. 20mL of 40% hydrofluoric acid solution was slowly added dropwise to the beaker for etching. The sample was ultrasonically shaken for 1 hour and stirred continuously at room temperature using a magnetic stirrer. The reaction was allowed to proceed for 24 hours. After the reaction was complete, a bluish-black solution was obtained. The suspension was washed with deionized water and centrifuged several times at 6000 rad / min. The pH of the washing solution was checked with pH paper until the pH was ≥6. A layer of oily black liquid floated in the supernatant, representing the minimal amount of monolayer and few-layer Ti3C2 obtained. The resulting precipitate in the lower layer was multilayer Ti3C2. The reaction solution was filtered to obtain a black solid. The sample was dried in a vacuum oven at 60°C for 12 hours. The dried powder was ground in an agate mortar for 15 minutes to obtain a black layered Ti3C2 MXene with the Al layer removed by acid etching.

[0055] Prepare EDTA-Cd solution:

[0056] Accurately weigh 1.3326 g of Cd(Ac)2·2H2O, grind it for 15 minutes, and dissolve it in 20 mL of deionized water; add 2.2610 g of EDTA-2Na·4H2O to the Cd(Ac)2 solution, and place the mixed solution at room temperature (25°C) with magnetic stirring for 15 minutes to obtain a clear and transparent EDTA-Cd solution.

[0057] Preparation of Ti3C2 MXene / CdTiO3:

[0058] 1.5 mL of tetrabutyl titanate was added dropwise to a mixed solution of 5 mL of anhydrous ethanol and 0.5 mL of glacial acetic acid, and magnetically stirred for 15 min. The prepared EDTA-Cd solution was slowly added dropwise to the ethanol solution of tetrabutyl titanate, and magnetically stirred for 15 min. 10 mL of 1.0 mol·L -1 NaOH solution; then a certain amount (0.0457 g, 0.0914 g, 0.1371 g) of homemade Ti3C2 MXene was added to the above solution and stirred for 15 min. The solution was then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel reactor and placed in an oven at 180 °C for 12 h. The reaction system was naturally cooled to room temperature, and the product was filtered and washed. It was then treated with 1 mol·L -1After being treated with HCl solution for 30 minutes, the mixture was washed to neutrality and dried at 80°C for 12 hours. The products were recorded as Ti3C2 MXene / CdTiO3-5%, Ti3C2 MXene / CdTiO3-10%, and Ti3C2 MXene / CdTiO3-15% according to the mass of added Ti3C2 MXene from low to high.

[0059] Example 2:

[0060] This embodiment provides a method for preparing a CdTiO3 photocatalyst, comprising the following steps:

[0061] 1.5 mL of tetrabutyl titanate (TBT) was added dropwise to a mixed solution of 5 mL of anhydrous ethanol and 0.5 mL of glacial acetic acid, and magnetically stirred for 15 min. The EDTA-Cd solution prepared in the example was slowly added dropwise to the above solution, and magnetically stirred for 15 min. 10 mL of 1.0 mol·L -1 The NaOH solution was then transferred to a 50 mL polytetrafluoroethylene-lined stainless steel reactor and placed in an oven at 180 ° C for 12 h. The reaction system was naturally cooled to room temperature, and the product was filtered and washed. -1 After being treated with HCl solution for 30 min, washed until neutral, and dried at 80 °C for 12 h, CdTiO3 was obtained.

[0062] Example 3:

[0063] Material characterization:

[0064] XRD analysis of Ti3C2 MXene / CdTiO3

[0065] The crystal structure and phase purity of the synthesized samples were analyzed by X-ray diffraction (XRD). The obtained composite sample Ti3C2MXene / CdTiO3-5%~15% was characterized by XRD. Figure 1The spectrum shown. The strong diffraction peak of Ti3C2 MXene at 2θ = 38.7° disappears, indicating that the aluminum atoms in the MAX phase are completely removed. The diffraction angles 2θ = 8.8°, 18.3°, 27.5°, and 60.7° correspond to the (002), (004), (006), and (110) crystal planes in Ti3C2 MXene (JCPS PDF#52-0975), respectively. Compared with Ti3AlC2, the diffraction peak intensity is reduced and shifted to lower angles. This may be due to the increase in the interlayer spacing of the two-dimensional material Ti3C2 and the presence of functional groups (such as -F, -O, and -OH) on the surface of Ti3C2 MXene. This result indicates that Ti3AlC2 is completely converted into Ti3C2. The characteristic diffraction peaks of Ti3C2 MXene and CdTiO3 appear in the XRD spectrum of Ti3C2 MXene / CdTiO3, indicating that the Ti3C2 MXene / CdTiO3 composite material has been successfully synthesized. The CdTiO3 crystal planes in the obtained Ti3C2 MXene / CdTiO3 composite material are consistent with the (101), (104), (015), (021), (024), (116) and (027) crystal planes of perovskite CdTiO3 and do not shift, indicating that the composite of Ti3C2 MXene and CdTiO3 does not change the crystal structure of CdTiO3.

[0066] FT-IR analysis of Ti3C2 MXene / CdTiO3

[0067] The prepared Ti3C2 MXene and Ti3C2 MXene / CdTiO3 were analyzed by FT-IR spectrum. Figure 2 Spectrum of prepared Ti3C2 MXene, 1628 and 3450 cm -1 The peak at 620cm is generated by -OH on the surface of Ti3C2 MXene. -1 A nearby peak is the deformation vibration peak of the Ti-O bond generated between the Ti atoms in Ti3C2 MXene and the -OH on the surface of Ti3C2 MXene. -1 The peak at is the CO bond. Figure 3 As shown, at 1652cm -1 and 2376cm -1 The absorption peaks at 380~1000cm are C=C and Ti-C bonds, indicating that Ti3C2 MXene / CdTiO3 composite materials were successfully synthesized. Ti3C2 MXene / CdTiO3-5%~Ti3C2 MXene / CdTiO3-15% and CdTiO3 -1 The infrared characteristic peak is similar to that of -1 Cd-O peak, 565cm-1 Cd-Ti-O peak, 707cm -1 The Ti-O peak of Ti3C2MXene / CdTiO3 composite material indicates that the addition of Ti3C2MXene does not affect the structure of CdTiO3 during the formation of Ti3C2MXene / CdTiO3 composite material.

[0068] XPS analysis of Ti3C2 MXene / CdTiO3

[0069] The composition and valence of surface elements of the prepared samples were obtained by X-ray photoelectron spectroscopy (XPS). Figure 4 As shown, CdTiO3 is composed of three elements: Cd, Ti, and O. Ti3C2 MXene is composed of two elements: C and Ti. Ti3C2 MXene / CdTiO3 displays four elements: C, Cd, Ti, and O. A C peak (284.31 eV) is detected in the CdTiO3 survey graph. This is due to the formation of C-doped CdTiO3 in the sample due to the use of ethanol as a solvent, resulting in a reduced band gap and a certain degree of visible light responsiveness.

[0070] Figure 5 The high-resolution XPS spectra of Cd 3d of CdTiO3 and Ti3C2 MXene / CdTiO3 are shown, with two obvious Cd 3d near 404eV and 410eV. 2+ Peak. Further analysis Figure 6 and Figure 7 XPS high-resolution spectra of Ti 2p and O 1s, and Ti 2p high-resolution spectra of CdTiO3, Ti3C2 MXene and Ti3C2 MXene / CdTiO3 ( Figure 6 ) can be fitted to obtain two main characteristic peaks, the binding energy peaks at 463eV and 457eV correspond to Ti 2p 1 / 2 and Ti 2p 3 / 2 This indicates that Ti exists in a tetravalent form in all three samples of CdTiO3, Ti3C2 MXene, and Ti3C2 MXene / CdTiO3. The O1s spectra of CdTiO3 and Ti3C2 MXene / CdTiO3 show that the characteristic peak at 529 eV comes from the Cd-O bond in CdTiO3, the characteristic peak at 531 eV comes from the Ti-O bond in CdTiO3, and O exists in a negative divalent form. Figure 8The high-resolution XPS spectra of C1s of Ti3C2MXene, CdTiO3 and Ti3C2 MXene / CdTiO3 given show a major signal peak. The C 1s spectrum shows that 284.27eV, 284.23eV and 284.19eV correspond to CC bonds, 285.92eV, 285.90eV and 285.87eV correspond to CO bonds, 280.79eV and 281.11eV correspond to C-Ti bonds, and 288.13eV is the residual CF bond of Ti3C2 MXene obtained by hydrofluoric acid etching. The XPS high-resolution analysis results of Cd 3s, Ti 2p, O 1s and C1s of Ti3C2 MXene / CdTiO3 composite materials and CdTiO3 and Ti3C2 MXene show that the binding energies of the constituent elements, Cd 3s, Ti 2p, O1s and C1s in the Ti3C2 MXene / CdTiO3 composite materials are consistent with those reported in the literature, indicating that the structures of CdTiO3 and Ti3C2MXene in the Ti3C2 MXene / CdTiO3 composite materials are not destroyed, but the binding energy of each element has a slight shift toward the low binding energy direction relative to the binding energy of the monomer. This may be due to the strong interaction at the interface of CdTiO3 and Ti3C2 MXene, which forms a heterojunction and changes the chemical environment of the elements, resulting in a decrease in binding energy.

[0071] FESEM analysis of Ti3C2 MXene / CdTiO3

[0072] Figure 9 The scanning electron micrographs of Ti3C2 MXene and Ti3C2 MXene / CdTiO3 samples are given. Figure 9 It can be clearly seen in the figure that accordion-shaped Ti3C2 MXene was obtained by hydrofluoric acid etching, and a Ti3C2 MXene / CdTiO3 composite material was successfully obtained through compounding. At the same time, CdTiO3 and Ti3C2 MXene are both attached at the interface, indicating the formation of a heterojunction, which is conducive to the transmission of photogenerated carriers between CdTiO3 and Ti3C2 MXene. However, as the Ti3C2 MXene loading gradually increases, due to its much larger particle size than CdTiO3, it may cover the surface active sites of CdTiO3, thereby reducing CdTiO3's light absorption and response to light, resulting in a decrease in the photocatalytic effect.

[0073] The particle size of CdTiO3 after loading Ti3C2 MXene was calculated by the Scherrer formula. It was found that the particle size of CdTiO3 at a loading of 5% was 31.06nm, the particle size of CdTiO3 at a loading of 10% was 30.92nm, and the particle size of CdTiO3 at a loading of 15% was 30.88nm, which is smaller than the CdTiO3 prepared before adding Ti3C2 MXene (particle size of 32nm). Moreover, with the increase of the loading amount, the particle size of the obtained CdTiO3 decreased. This may be because Ti3C2MXene affects the polymerization of CdTiO3 in the solution, thereby reducing its size.

[0074] UV-vis DRS analysis of Ti3C2 MXene / CdTiO3

[0075] Figure 10 The UV-vis DRS spectra of Ti3C2 MXene / CdTiO3 are shown. The figure shows that Ti3C2 MXene / CdTiO3 with different Ti3C2 MXene loadings all have a certain visible light response ability, and the visible light response ability increases with the increase of Ti3C2 MXene loading.

[0076] Figure 11 The band gap calculation results based on the Tauc relationship are shown. The band gap values ​​of Ti3C2 MXene / CdTiO3-5% to 15% are 2.91eV, 2.88eV, and 2.79eV, respectively. Compared with CdTiO3 monomer (E g =3.08eV) have been reduced, and the light response ability of CdTiO3 photocatalytic materials has been successfully broadened from the ultraviolet region to the visible region through Ti3C2 MXene composite, achieving the expected idea. At the same time, with the increase of Ti3C2 MXene loading, the band gap of CdTiO3 decreases.

[0077] Analysis of electrochemical performance of Ti3C2 MXene / CdTiO3

[0078] The generation and transfer efficiency of photogenerated carriers are important factors affecting photocatalytic activity. The carrier generation and transfer performance of Ti3C2 MXene / CdTiO3 were evaluated using transient photocurrent response and electrochemical impedance spectroscopy. Figure 12The current-time curves of Ti3C2MXene / CdTiO3 composites under intermittent illumination (on / off cycle of 20 seconds) are presented. The intensity of the current signal directly reflects the rate of charge carrier generation and separation in Ti3C2MXene / CdTiO3. In the absence of illumination, the current response signals of Ti3C2MXene / CdTiO3-5%, Ti3C2MXene / CdTiO3-10%, Ti3C2MXene / CdTiO3-15%, and CdTiO3 are very small. When illuminated, the current signal increases instantaneously. The current signal intensity of the catalysts is Ti3C2MXene / CdTiO3-10% > Ti3C2MXene / CdTiO3-5% > Ti3C2MXene / CdTiO3-15% > CdTiO3. All Ti3C2 MXene / CdTiO3 composites exhibited higher photocurrent signals than CdTiO3 monomers, demonstrating that the constructed heterojunction effectively utilizes photogenerated carriers and exhibits improved photocatalytic activity. With intermittent illumination (20-second intervals), the photocurrent of the Ti3C2 MXene / CdTiO3-10% composite was strong and stable, indicating that the prepared samples possessed good stability during photocatalytic degradation.

[0079] Electrochemical impedance spectroscopy (EIS) was used to further analyze the separation and transport efficiency of interface carriers in Ti3C2 MXene / CdTiO3. Figure 13 As shown in the figure, the Nyquist semicircle diameter of the Ti3C2 MXene / CdTiO3 composite is smaller than that of CdTiO3 alone, with the Ti3C2 MXene / CdTiO3-10% composite having the smallest Nyquist semicircle diameter. This indicates that the carriers in the Ti3C2 MXene / CdTiO3-10% composite have a smaller charge transfer resistance and a faster transfer rate. These results demonstrate that by combining Ti3C2 MXene with CdTiO3 and controlling their loading, the separation and transfer of charge carriers in the Ti3C2 MXene / CdTiO3 composite can be significantly improved, which is beneficial for enhancing the performance of photocatalytic degradation of pollutants.

[0080] Analysis of photocatalytic performance of Ti3C2 MXene / CdTiO3

[0081] Figure 14 and Figure 15 It shows that 100mg Ti3C2 MXene / CdTiO3 degrades to 10mg·L under visible light and ultraviolet light irradiation respectively. -1Degradation of RhB dye. The results show that compared with visible light, the degradation efficiency of the sample under ultraviolet light is higher. After 180 minutes of irradiation, the degradation rates of Ti3C2 MXene / CdTiO3-5%~15% are 75%, 85%, and 63%, respectively, which are higher than that of CdTiO3 monomer (nearly 70%). This shows that the photocatalytic effect of CdTiO3 can be improved by Ti3C2 MXene composite. At the same time, Figure 14 It can be seen that Ti3C2 MXene / CdTiO3 also has a good photocatalytic degradation rate under visible light irradiation (Ti3C2 MXene / CdTiO3-10% is 76%). Since visible light accounts for ~45% of the solar spectrum energy, it effectively improves light utilization and reduces energy consumption.

[0082] The stability of the catalyst was investigated by recycling experiments on Ti3C2 MXene / CdTiO3-10% photocatalytic degradation of RhB. Five photocatalytic recycling experiments were conducted using Ti3C2 MXene / CdTiO3-10%. Figure 16 As shown in Figure 3, the Ti3C2MXene / CdTiO3-10% sample exhibited excellent photocatalytic activity and stability after the fifth repeated catalytic degradation of RhB, with a degradation rate exceeding 80% after 180 minutes of illumination.

[0083] Analysis of the photocatalytic mechanism of Ti3C2 MXene / CdTiO3

[0084] Figure 17 and Figure 18 Shows the O2 generation of Ti3C2 MXene / CdTiO3-10% and CdTiO3 in the dark and after illumination - and ·OH EPR spectra. ·O2 was not observed in the dark - The characteristic peaks of DMPO-·O2 and ·OH indicate that no active free radicals are generated in the absence of light. After 10 minutes of visible light irradiation, DMPO-·O2 - and the response signals of DMPO-·OH. Figure 17 There are 4 strong peaks and 2 weak peaks in the image, indicating that there is O2 - Generation. Figure 18 The typical DMPO-·OH has four peaks, and the ratio of peak area is 1:2:2:1. Figure 17 and Figure 18 Among them, Ti3C2 MXene / CdTiO3 exhibits O2 -The characteristic peaks of ·O and ·OH are significantly stronger than those of CdTiO3, indicating that Ti3C2 MXene / CdTiO3 can produce more ·O2 after being irradiated with light compared with CdTiO3. - and ·OH, the rate of photocatalytic degradation of pollutants per unit time is faster and has a higher degradation rate, showing stronger photocatalytic activity.

[0085] The valence band and conduction band positions of CdTiO3 were verified by testing the Mott-Schottky curve. Figure 19 The slope of the MS curve is positive, indicating that CdTiO3 is a typical n-type semiconductor. Its flat band potential (E FB ) is -0.51 V, and further according to the E g is 3.08eV and E VB =E CB +E g , the E of CdTiO3 relative to the standard hydrogen electrode can be calculated CB =-0.44V, and the valence band potential is 2.64eV. Based on the above results, the Ti3C2 MXene / CdTiO3 heterojunction photocatalytic mechanism is proposed, such as Figure 20 shown.

[0086] Under illumination, the metallic properties of Ti3C2MXene favor the capture of photogenerated electrons at the interface between the n-type semiconductor CdTiO3 and Ti3C2MXene. Under illumination, the photon absorption ability of CdTiO3 is stimulated, generating photogenerated electron-hole pairs. Because Ti3C2MXene has a lower Fermi level, photogenerated electrons from CdTiO3 transfer to Ti3C2MXene until their Fermi levels are equal. The formation of the Ti3C2MXene / CdTiO3 heterojunction creates a band gap at the interface, leading to an effective upward band bending of CdTiO3 and forming a Schottky barrier. Because electrons captured by Ti3C2MXene cannot flow back into the conduction band of CdTiO3, recombination of photogenerated electrons and holes in CdTiO3 is effectively suppressed, improving carrier utilization. Electrochemical impedance spectroscopy and IT response curves confirm this finding.

[0087] According to the active species capture experiment and EPR test results, the main active species in the Ti3C2 MXene / CdTiO3 photocatalytic degradation of RhB is O2 - and ·OH, CdTiO3 conduction band electrons and Ti3C2 MXene surface electrons capture O2 to generate ·O2 -At the same time, the holes in the valence band of CdTiO3 oxidize water to produce OH and O2. The generated active free radicals react with RhB adsorbed on the catalyst surface to undergo photocatalytic oxidation. The specific reaction process is shown in Equations (1) to (5).

[0088] The reaction process of photocatalytic degradation of Rhodamine B by Ti3C2 MXene / CdTiO3 material includes:

[0089] Ti3C2 MXene / CdTiO3+hv→e - +h + (1)

[0090] h + +2H2O→O2+4H + (2)

[0091] e - +O2 → ·O2 - (3)

[0092] h + +H2O→·OH (4)

[0093] RhB+·OH+·O2 - →Degradated product (5)

[0094] In summary, the present invention discloses a method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst. The preparation method utilizes an EDTA complexation and solvothermal method. A soluble cadmium salt and a complexing agent, EDTA-2Na, are added to deionized water to obtain a clear, transparent solution. This solution is then added to an ethanol solution of tetrabutyl titanate under magnetic stirring. After uniform stirring, NaOH is added to adjust the pH of the solution. Ti3C2 MXene is then added, magnetically stirred, and a solvothermal reaction is performed to obtain a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst with excellent visible light photocatalytic performance. The photocatalyst obtained by this method achieves a visible light degradation efficiency of 76% for rhodamine B in water. Ti3C2 MXene / CdTiO3 overcomes the shortcomings of CdTiO3's large bandgap and UV response. Furthermore, Ti3C2 MXene / CdTiO3 exhibits excellent stability, maintaining good catalytic activity and stability after five cycles of degradation, suggesting promising industrial applications.

[0095] At this point, those skilled in the art will recognize that, although the embodiments of the present invention have been shown and described in detail herein, many other variations or modifications consistent with the principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. A method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst, characterized in that: The preparation method comprises the following steps: Step S1: Ti3AlC2 is subjected to hydrofluoric acid ultrasonic etching to remove the Al layer, and black layered Ti3C2 MXene is obtained by filtration, washing, and drying; Step S2: Accurately weighing a soluble cadmium salt, grinding it, and then dissolving it in deionized water; adding EDTA-2Na·4H2O to the soluble cadmium salt solution, and stirring the mixed solution at room temperature to obtain a clear and transparent EDTA-Cd solution; Step S3: Tetrabutyl titanate and glacial acetic acid are added to anhydrous ethanol, and the clear and transparent EDTA-Cd solution obtained in step S2 is added and stirred under stirring, and NaOH is added to adjust the pH of the solution. The Ti3C2 MXene obtained in step S1 is added thereto under stirring, and stirred until the mixture is uniform, and then a solvent thermal reaction is carried out. After the reaction is completed, the mixture is naturally cooled to room temperature and then filtered and washed. The obtained product is treated with HCl solution, washed until neutral, and dried to obtain a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst with high photocatalytic performance.

2. A method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The concentration of hydrofluoric acid in step S1 is 40%, and the ultrasonic etching treatment time is 24 hours.

3. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The grinding time in step S2 is 15 minutes; the molar ratio of the soluble cadmium salt to the complexing agent EDTA-2Na·4H2O is 1:

1.

4. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The soluble cadmium salt in step S2 is one of cadmium nitrate, cadmium chloride and cadmium acetate.

5. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The washing conditions in step S3 are: washing with deionized water and anhydrous ethanol alternately for several times until the pH is 7; the drying temperature in step S3 is 80° C., and the drying time is 12 hours.

6. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: In step S3, the molar ratio of EDTA-Cd, tetrabutyl titanate, and Ti3C2 MXene is 10:9:1, the solvothermal reaction temperature is 180° C., and the solvothermal reaction time is 12 h.

7. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The specific method of treating the HCl solution in step S3 is: filtration, washing the filter cake of the obtained product with 1 mol·L -1 Soak in HCl solution for 30 minutes, dry at 80℃ and dry for 12 hours.

8. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The stirring time in step S3 is 15 min; the concentration of the NaOH solution is 1.0 mol·L -1 .

9. The method for preparing a Ti3C2 MXene / CdTiO3 heterojunction photocatalyst as claimed in claim 1, characterized in that: The CdTiO3 in the Ti3C2 MXene / CdTiO3 heterojunction photocatalyst is nanoparticles of uniform size, and the particle size of the CdTiO3 is 30 to 35 nm. The visible light response range of the Ti3C2 MXene / CdTiO3 heterojunction is 400 to 800 nm.

10. A method for applying the Ti3C2MXene / CdTiO3 heterojunction photocatalyst prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The Ti3C2 MXene / CdTiO3 heterojunction photocatalyst is applied to visible light catalytic degradation of dyes in water.

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