TiO2 composite photo-anode material based on ZIF-8 and MXene synergistic modification, preparation method and application of TiO2 composite photo-anode material
By constructing a composite structure of ZIF-8 and MXene synergistically modified on the surface of TiO2 nanowire arrays, the problems of poor visible light response and carrier recombination of TiO2 photoanode materials were solved, achieving efficient photoelectric conversion performance and improved material stability.
Patent Information
- Application Number
- CN202511242135.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-02
- Publication Date
- 2025-10-17
AI Technical Summary
Existing TiO2 photoanode materials have poor visible light response, severe carrier recombination, low charge transfer efficiency and insufficient structural stability, which limits their photoelectric conversion performance.
By in situ growing a ZIF-8 porous shell layer on the surface of the TiO2 nanowire array and spin-coating and depositing a MXene two-dimensional conductive sheet layer, a composite structure synergistically modified with ZIF-8 and MXene is formed, combined with annealing treatment to enhance interface bonding and electron transfer efficiency.
The separation efficiency and migration rate of photogenerated carriers are significantly improved, the photocurrent density is increased by more than 2 times, the interface charge transfer impedance is reduced, the carrier concentration is increased, and the absorption edge is red-shifted to the visible light region, showing excellent photostability.
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Figure CN120797067A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of photoelectrochemical water splitting and new energy materials, and particularly relates to a TiO2 composite photoanode material based on ZIF-8 and MXene synergistic modification and a preparation method thereof. BACKGROUND
[0002] Photoelectrochemical (PEC) water splitting is a green energy conversion technology for realizing clean hydrogen production by using solar energy, and the core lies in developing a composite photoanode material with high efficient carrier separation capacity and good light stability. TiO2 is widely used in PEC systems due to its advantages of low cost, strong chemical stability and non-toxicity. However, TiO2 has a large band gap, mainly responds to ultraviolet light, and has low light utilization rate; at the same time, the photo-generated electrons and holes are prone to recombination, which limits the charge separation efficiency and photoelectric conversion performance.
[0003] To overcome the above limitations, researchers try to improve the performance of TiO2 by element doping, noble metal deposition and heterostructure construction. Among them, MOF materials, especially ZIF-8, are used to regulate the interface behavior of TiO2 due to its regular porous structure and hole trapping ability; and the new two-dimensional material MXene (such as Nb2CT x ) has outstanding performance in enhancing electron transport due to its high conductivity and surface adjustable functional groups. However, existing researches mostly focus on single loading of ZIF-8 or MXene, and there is still a lack of systematic exploration of the synergistic enhancement of TiO2 performance under the synergistic action of the two.
[0004] In addition, the controllable preparation of ZIF-8 and MXene double-layer structure based on TiO2 nanowire array still faces problems such as interface mismatch, poor stability and complex process. Therefore, it is urgent to develop a new type of TiO2 composite photoanode material with reasonable structure, stable interface coupling and high efficient carrier separation. SUMMARY
[0005] The purpose of the present application is to provide a TiO2 composite photoanode material based on ZIF-8 and MXene synergistic modification and a preparation method thereof, to solve the technical problems of poor visible light response ability, serious carrier recombination, low charge transfer efficiency and insufficient structural stability of the existing TiO2 photoanode material, realize the spatial separation and regulation of electrons and holes, and improve the photoelectric conversion efficiency and material stability.
[0006] The technical scheme of the present application is as follows:
[0007] A TiO2 composite photoanode material based on the synergistic modification of ZIF-8 and MXene comprises an FTO conductive substrate and a composite structural layer arranged on the substrate; the composite structural layer comprises, from bottom to top, a TiO2 nanowire array grown on the FTO by a hydrothermal method, a porous ZIF-8 grown in situ on the TiO2 surface, and a MXene two-dimensional conductive sheet deposited by spin coating on the outer surface of the ZIF-8; the structural layer is annealed to enhance the bonding between the interfaces and the electron migration efficiency.
[0008] The composite photoanode material is used to construct a working electrode in a photoelectrochemical water splitting system, which can achieve effective spatial separation and directional transmission of photogenerated electrons and holes, thereby improving charge separation efficiency and photoelectric conversion performance.
[0009] The TiO2 nanowire arrays were obtained by hydrothermal synthesis at 180°C for 6 hours and annealed at 500°C for 1 hour in an air atmosphere to improve crystallinity and stability.
[0010] The ZIF-8 porous shell is formed by immersing the TiO2 sample in a mixed solution of 0.05M 2-methylimidazole and 0.01M Zn(NO3)2·6H2O in methanol, reacting at room temperature for 30 minutes, and then drying at 70°C and annealing at 150°C for 30 minutes to enhance its structural stability and interfacial bonding ability.
[0011] Preferably, the MXene material is Nb2CT prepared by etching Nb2AlC precursor with LiF and HCl. x The film was deposited by three rounds of spin coating at 500 rpm for 10 seconds and 1000 rpm for 20 seconds, and then annealed in an argon atmosphere at 200°C for 30 minutes to improve its conductivity and adhesion.
[0012] Preferably, the TiO2 nanowire array has a diameter of 25 nm, a height of 5 μm, is densely arranged, and has a surface roughness suitable for uniform growth of ZIF-8.
[0013] The ZIF-8 porous shell is preferably 20 to 50 nm thick, with uniform pores, continuously covering the TiO2 surface without blocking its electron channels. The MXene flakes are evenly dispersed, free of agglomeration, and uniformly loaded over the ZIF-8 surface.
[0014] The present invention also provides a method for preparing the composite photoanode material, comprising the following steps:
[0015] (1) The FTO substrate was ultrasonically cleaned with acetone, ethanol, and deionized water in sequence;
[0016] (2) FTO was placed in a mixture of hydrochloric acid, deionized water, and butyl titanate and hydrothermally reacted at 180 °C for 6 h to form TiO2 NWAs;
[0017] (3) air annealing at 500°C for 1 hour;
[0018] (4) Immerse the TiO2 sample in the ZIF-8 precursor solution, react at room temperature for 30 minutes, wash, dry, and anneal;
[0019] (5) The MXene dispersion is spin-coated on the ZIF-8 surface, and the composite photoanode is obtained after annealing.
[0020] Preferably, the ZIF-8 precursor solution contains 2-methylimidazole and Zn 2+ The concentration ratio is 5:1, and the solvent is methanol.
[0021] Preferably, the MXene sheets are ultrasonically treated for 30 minutes before spin coating to achieve uniform dispersion.
[0022] The present invention also provides a use of the composite photoanode material and the material prepared by the above-described preparation method. The composite photoanode material is used in a photoelectrochemical water splitting system and exhibits high photocurrent density, low charge transfer resistance, and good stability. Compared with the prior art, the present invention has the following advantages:
[0023] The TiO2-ZIF-8-MXene composite photoanode material constructed by this invention features a ZIF-8 structure that provides hole capture and induces oxygen vacancies on the TiO2 surface, enhancing hole reactivity. MXene provides a fast electron transport channel and forms Ti–C / Nb–C bonds to enhance interfacial electronic coupling. TiO2 nanowires, as a base skeleton, provide stable light absorption and transmission pathways. These three materials synergistically form a "hole-electron spatial separation network," significantly improving the separation efficiency and migration rate of photogenerated carriers.
[0024] In the PEC performance test, the photocurrent density of the composite photoanode at 1.23V vs. RHE was more than 2 times higher than that of bare TiO2, the interfacial charge transfer impedance was significantly reduced, the carrier concentration was increased, and the absorption edge was red-shifted to the visible light region, showing excellent photostability and long-term durability, and is suitable for promotion and application in high-efficiency solar water splitting systems. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Schematic diagram of the structure of the TiO2-ZIF-8-MXene composite photoanode material of the present invention.
[0026] Figure 2A preparation process of the TiO2-ZIF-8-MXene composite photo-anode material.
[0027] Figure 3 A SEM diagram of the TiO2-ZIF-8-MXene composite photo-anode material.
[0028] Figure 4 A J-V curve comparison diagram.
[0029] Figure 5 A EIS curve comparison diagram.
[0030] Figure 6 A MS curve comparison diagram. DETAILED DESCRIPTION
[0031] The application will be described in detail below with reference to the drawings and examples.
[0032] As shown in the drawings, Figure 1 the application provides a TiO2 composite photo-anode material based on ZIF-8 and MXene synergistic modification, which comprises, from bottom to top, an FTO conductive glass substrate, a TiO2 nanowire array layer, an in-situ grown ZIF-8 porous shell layer, and a spin-coated MXene two-dimensional sheet layer.
[0033] The TiO2 nanowire array is synthesized by a hydrothermal method at 180℃ and annealed at 500℃; the ZIF-8 shell layer is formed by immersing the TiO2 sample in a mixed methanol solution containing 0.05M 2-methylimidazole and 0.01M Zn(NO3)2·6H2O, and reacting at room temperature for 30 minutes; the MXene sheet layer is obtained by etching the Nb2AlC precursor with LiF and HCl, and is deposited on the surface of the ZIF-8 by a "low-speed-high-speed spin coating" method, and is vacuum annealed at 200℃ for 30 minutes to enhance the interface bonding force.
[0034] As shown in the drawings, Figure 2 the preparation method of the TiO2-ZIF-8-MXene three-component composite photo-anode is as follows:
[0035] (1) The FTO conductive glass substrate is sequentially ultrasonically cleaned with acetone, ethanol and deionized water for 15 minutes each, and is dried and reserved.
[0036] (2) The cleaned FTO substrate is placed in a mixed solution containing 15mL hydrochloric acid, 15mL deionized water and 0.5mL butyl titanate, and is sealed in a high-pressure reaction kettle, and is hydrothermally reacted at 180℃ for 6 hours.
[0037] (3) After the reaction, the sample was taken out, washed with deionized water and ethanol, dried, and then annealed at 500 DEG C for 1 hour in an air atmosphere to form a vertically arranged TiO2 nanowire array (TiO2 NWAs).
[0038] (4) Preparation of ZIF-8 precursor solution: 2-methylimidazole and Zn(NO3)2·6H2O were weighed and prepared into 0.05M and 0.01M methanol solutions.
[0039] (5) The TiO2 NWAs sample was completely immersed in the ZIF-8 precursor mixed solution, and the in-situ growth of ZIF-8 crystals was carried out by keeping it at room temperature for 30 minutes.
[0040] (6) After the reaction, the sample was taken out, washed with deionized water and ethanol, dried, and then annealed at 500 DEG C for 1 hour in an air atmosphere to form a vertically arranged TiO2 nanowire array (TiO2 NWAs).
[0041] (7) The MXene supernatant was prepared by reacting Nb2AlC powder with LiF and HCl, and then dispersed in ethanol and ultrasonicated for 30 minutes to obtain a uniform MXene dispersion.
[0042] (8) The MXene layers were deposited on the surface of the TiO2-ZIF-8 composite structure by spin coating, and the spin coating parameters were 500 rpm for 10 seconds and 1000 rpm for 20 seconds, repeated 3 times, to obtain a uniform MXene coating layer.
[0043] (9) After spin coating, the sample was placed in a vacuum drying oven and annealed at 200 DEG C for 30 minutes in a vacuum environment to enhance the interface bonding between MXene and ZIF-8 and improve the overall structural stability.
[0044] (10) After cooling, the final TiO2-ZIF-8-MXene three-component composite photoanode material was obtained as shown in Figure 1 , which was used for subsequent photoelectrochemical tests and material characterization.
[0045] In addition, the TiO2-MXene composite photoanode material and the TiO2-ZIF-8 composite photoanode material were prepared by the following methods, respectively, and their performance was compared with that of the TiO2-ZIF-8-MXene three-component composite photoanode of the application.
[0046] The preparation method of the TiO2-MXene composite photoanode is as follows:
[0047] (1) The FTO conductive glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 15 minutes, and then dried and reserved.
[0048] (2) The cleaned FTO substrate was placed in a mixed solution containing 15 mL of hydrochloric acid, 15 mL of deionized water and 0.5 mL of butyl titanate, and was sealed in a high-pressure reaction kettle for hydrothermal reaction at 180°C for 6 hours.
[0049] (3) After the reaction was completed, the sample was taken out, washed thoroughly with deionized water and ethanol, and then annealed at 500°C in an air atmosphere for 1 hour to form a vertically arranged TiO2 nanowire array (TiO2 NWAs).
[0050] (4) The MXene supernatant prepared by etching (using Nb2AlC as a precursor and using LiF and HCl for selective etching and multiple centrifugal stripping) was weighed, diluted with ethanol and ultrasonically dispersed for 30 minutes.
[0051] (5) The MXene was uniformly loaded on the surface of the TiO2 NWAs by spin coating, and the spin coating parameters were set as 500 rpm for 10 seconds, 1000 rpm for 20 seconds, repeated 3 times to ensure uniform coverage.
[0052] (6) After spin coating, the sample was placed in a vacuum drying oven and annealed at 200°C for 30 minutes in a vacuum environment to enhance the interfacial bonding force between the MXene and the TiO2, and finally a TiO2-MXene composite photoanode was obtained.
[0053] The preparation method of the TiO2-ZIF-8 composite photoanode is as follows:
[0054] (1) The FTO conductive glass substrate was ultrasonically cleaned with acetone, ethanol and deionized water for 15 minutes each, and then dried and reserved.
[0055] (2) The cleaned FTO substrate was placed in a mixed solution containing 15 mL of hydrochloric acid, 15 mL of deionized water and 0.5 mL of butyl titanate, and was sealed in a high-pressure reaction kettle for hydrothermal reaction at 180°C for 6 hours.
[0056] (3) After the reaction was completed, the sample was taken out, washed thoroughly with deionized water and ethanol, and then annealed at 500°C in an air atmosphere for 1 hour to form a vertically arranged TiO2 nanowire array (TiO2 NWAs).
[0057] (4) A ZIF-8 precursor solution was prepared: 2-methylimidazole and Zn(NO3)2·6H2O were weighed and prepared into 0.05M and 0.01M methanol solutions.
[0058] (5) The TiO2 NWAs sample was completely immersed in the ZIF-8 precursor mixed solution, and in-situ growth of ZIF-8 crystals was carried out by keeping it at room temperature for 30 minutes.
[0059] (6) After the reaction is completed, the sample is removed, rinsed several times with methanol to remove unreacted residues, then dried at 70°C for 30 minutes, and the sample is placed in a drying oven and annealed at 150°C for 30 minutes to enhance the interfacial bonding force, to obtain a TiO2-ZIF-8 composite photoanode.
[0060] Comparative test
[0061] The composite photoanode materials of TiO2-MXene, TiO2-ZIF-8 and TiO2-ZIF-8-MXene prepared by the above method are used for photoelectrochemical performance test, including scanning electron microscopy (SEM) as shown in Figure 3 , linear sweep voltammetry (J-V) curves as shown in Figure 4 , electrochemical impedance spectroscopy (EIS) as shown in Figure 5 , Mott-Schottky analysis (MS) as shown in Figure 6 , stability test and XPS analysis, etc. The test conditions are uniformly AM 1.5G solar simulator irradiation, 0.5M Na2SO4 electrolyte solution, Ag / AgCl reference electrode and Pt counter electrode system.
[0062] As shown in the J-V curve in Figure 4 , at a potential of 1.23V vs. RHE, the photoelectric current density of the three photoanodes is in the order of TiO2-ZIF-8-MXene > TiO2-MXene > TiO2-ZIF-8, where the photoelectric current density of the TiO2-ZIF-8-MXene sample is more than twice that of bare TiO2, significantly higher than that of single-component modified structure, indicating that the synergistic structure significantly enhances the photoelectric conversion capability.
[0063] As shown in Figure 5 , the EIS test results show that the interfacial charge transfer resistance of Example Three is the smallest, and the radius in the Nyquist diagram is the smallest, indicating that the composite structure has higher electron migration efficiency.
[0064] As shown in Figure 6 , Mott-Schottky test shows that the flat band potential is negatively shifted, and the carrier concentration is significantly improved, which is more conducive to the extraction and transport of photo-generated electrons.
[0065] The application significantly improves the separation efficiency of photo-generated carriers and the interface charge transport performance by introducing ZIF-8 and MXene on the surface of TiO2 nanowire array to construct a multi-layer heterostructure. ZIF-8 realizes directional extraction of holes and induces the formation of oxygen vacancies, and MXene provides an efficient electron migration channel, and the two cooperatively construct an electron-hole separation network. The composite photoanode improves the photocurrent density to more than twice that of the original TiO2 at 1.23 V vs. RHE, and EIS and Mott-Schottky tests show that the interface impedance is reduced and the carrier concentration is improved, and it shows excellent stability in continuous light test, and has good application prospect.
[0066] It should be noted that the description of these embodiments is used to help understand the application, but does not constitute a limitation on the application. Furthermore, the technical features involved in the above-described various embodiments of the application can be combined with each other as long as they do not conflict with each other. In addition, only part of the embodiments, not all the embodiments, based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative labor belong to the protection scope of the application.
Claims
1. A TiO2 composite photoanode material based on ZIF-8 and MXene synergistic modification, characterized in that: It includes an FTO conductive glass substrate, a TiO2 nanowire array layer, an in-situ grown ZIF-8 porous shell layer, and a spin-coated MXene two-dimensional sheet layer, which are arranged in sequence from bottom to top. The TiO2 nanowire array was synthesized by a hydrothermal method at 180°C and annealed at 500°C; The ZIF-8 porous shell is formed by immersing the TiO2 sample in a methanol mixture solution containing 0.05M 2-methylimidazole and 0.01M Zn(NO3)2·6H2O at room temperature for 30 minutes; The MXene sheets were obtained by etching the Nb2AlC precursor with LiF and HCl, and deposited on the ZIF-8 surface by a "low-speed-high-speed spin coating" method. The interfacial bonding strength was enhanced by vacuum annealing at 200°C for 30 minutes.
2. The composite photoanode material according to claim 1, characterized in that: The TiO2 nanowire array has a vertically aligned structure, a diameter of 25 nm, and a height of 5 μm.
3. The composite photoanode material according to claim 1, characterized in that: The MXene is Nb2CT x , T x Indicates that the surface contains –OH, –F or –O functional groups.
4. The composite photoanode material according to claim 1, wherein: The MXene spin coating process was performed by combining spin coating at 500 rpm for 10 seconds and spin coating at 1000 rpm for 20 seconds, which was repeated three times.
5. The composite photoanode material according to claim 1, characterized in that: The ZIF-8 porous shell has a thickness of 10 to 15 nm, is in a continuous covering state, and maintains unobstructed electron channels.
6. The composite photoanode material according to any one of claims 1 to 5, characterized in that: The annealing temperature of the composite photoanode material is 200° C., the annealing time is 30 minutes, and the process is carried out under an argon atmosphere.
7. A method for preparing the composite photoanode material according to claim 1, characterized in that: The steps include: (1) The FTO substrate was ultrasonically cleaned with acetone, ethanol, and deionized water in sequence; (2) FTO was placed in a mixture of hydrochloric acid, deionized water, and butyl titanate and hydrothermally reacted at 180 °C for 6 h to form TiO2 NWAs; (3) air annealing at 500°C for 1 hour; (4) Immerse the TiO2 sample in the ZIF-8 precursor solution, react at room temperature for 30 minutes, wash, dry, and anneal; (5) The MXene dispersion is spin-coated on the ZIF-8 surface, and the composite photoanode is obtained after annealing.
8. The preparation method according to claim 7, characterized in that: The reaction of 2-methylimidazole and Zn in ZIF-8 precursor solution 2+ The concentration ratio is 5:1, and the solvent is methanol.
9. The preparation method according to claim 7, characterized in that: The MXene sheets were ultrasonically treated for 30 minutes before spin coating.
10. Use of the composite photoanode material according to any one of claims 1 to 9, characterized in that: The composite photoanode material is used in a photoelectrochemical water decomposition system.