Preparation and application of UIO66-NH2 (at) GE-TiO2 composite photo-anode based on interface amido bond modification

Abstract

The invention discloses a UIO66-NH2 (at) GE-TiO2 composite photo-anode based on interface amido bond modification as well as a preparation method and application of the UIO66-NH2 (at) GE-TiO2 composite photo-anode. The preparation method comprises the following steps: firstly, enabling a titanium source precursor and carboxyl functionalized graphene to grow a GE-TiO2 photo-anode on a conductive substrate through a hydrothermal method; secondly, growing a UIO66-NH2 layer on the surface of the GE-TiO2 in situ through a secondary hydrothermal method to form a primary composite structure; and finally, carrying out condensation reaction on amino in UIO66-NH2 and carboxyl on the surface of graphene in GE-TiO2 by utilizing a condensation reagent (EDCI / HOBt) to form covalent amido bond bridging, thereby obtaining the final composite photo-anode. Strong coupling between UIO66-NH2 and GE-TiO2 is achieved by constructing a covalent amido bond interface, the amido bond serves as an efficient directional carrier transmission channel, interface charge recombination is remarkably inhibited, and therefore the photoelectrochemical water decomposition performance of the photo-anode is greatly improved. The material has a wide application prospect in the field of green hydrogen production.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical water splitting technology, specifically to a UIO66-NH2@GE-TiO2 composite photoanode based on interfacial amide bond modification, its preparation method, and its application. Background Technology

[0002] With rapid global economic development and continuous population growth, humanity's dependence on traditional fossil fuels is deepening, leading to increasingly severe energy crises and environmental problems. Fossil fuels are non-renewable resources, and long-term over-exploitation has brought them to the risk of depletion. Simultaneously, the combustion of fossil fuels releases large amounts of greenhouse gases and pollutants such as carbon dioxide and sulfides, exacerbating global warming, acid rain, and other environmental degradation phenomena. Against this backdrop, developing efficient, clean, and sustainable renewable energy alternatives has become a key path to achieving global energy transition and carbon neutrality goals.

[0003] Solar energy, as a clean energy source with unlimited reserves and wide distribution, has enormous potential for development and utilization. However, the inherent limitations of solar energy, such as its natural fluctuations and intermittency, restrict its direct and efficient utilization. Hydrogen, as an ideal energy storage medium with high energy density and water as its combustion product, has attracted much attention for its preparation technology. Among these technologies, the production of green hydrogen through photoelectrochemical (PEC) water splitting can directly convert solar energy into chemical energy stored in hydrogen, achieving efficient capture and stable utilization of solar energy, and is considered one of the core technologies of the future energy system.

[0004] In photoelectrochemical water splitting systems, the photoanode is the core component determining the overall system performance. Its main function is to absorb sunlight to generate photogenerated electron-hole pairs and drive the water oxidation reaction on the anode surface. Titanium dioxide (TiO2) is widely used as a basic material in the field of photoelectrocatalysis due to its advantages such as high chemical stability, excellent optical properties, low cost, and environmental friendliness. However, pure TiO2 has an inherent defect of a fast photogenerated electron-hole pair recombination rate, which makes its photoelectric conversion efficiency and water splitting performance difficult to meet the requirements of practical applications, greatly limiting its industrial application in the field of photoelectrochemical water splitting.

[0005] To address the aforementioned shortcomings of TiO2, researchers have conducted extensive modification studies, including elemental doping, semiconductor composites, and surface modification. Among these, constructing composite heterostructures is one of the effective strategies for enhancing the photoelectric performance of TiO2. Graphene, a two-dimensional carbon material with ultra-high electron mobility and a large specific surface area, can be composited with TiO2 to form a GE-TiO2 structure, significantly improving electron transport rates and suppressing electron-hole recombination. Furthermore, metal-organic frameworks (MOFs), due to their high specific surface area, tunable pore structure, and abundant active sites, are widely used to modify photoelectrodes to enhance their light absorption and surface reactivity. UIO66-NH2, as a typical MOF material, exhibits good chemical stability and optical response characteristics; its composite with GE-TiO2 holds promise for further improving the photoelectrochemical performance of photoanodes.

[0006] However, the interfacial bonding of existing composite photoanode materials is mostly physical adsorption, resulting in weak interfacial interactions and high resistance to interfacial charge transfer. The electron-hole recombination problem remains unresolved. Furthermore, weak interfacial bonding affects the long-term stability of the material, limiting its practical application lifespan. Therefore, how to construct stable and efficient interfacial charge transfer channels through chemical modification to further improve the photoelectric conversion efficiency and stability of composite photoanodes has become a pressing technical challenge in the field of photoelectrochemical water splitting.

[0007] To address this, this invention proposes an innovative strategy—constructing an amide-bridged composite structure of UIO66-NH2 and TiO2—which effectively enhances interfacial electron transport efficiency, thereby significantly improving photoelectrochemical water splitting performance. The introduction of graphene further enhances the electron conduction rate, while the amide bonds act as stable electron transfer channels, suppressing electron-hole recombination and significantly improving photocurrent density and stability. Experimental results show that this novel composite photoanode material exhibits excellent photoelectrochemical activity under standard AM1.5G illumination conditions, providing a new solution for green hydrogen production. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a UIO66-NH2@GE-TiO2 composite photoanode based on interfacial amide bond modification, its preparation method, and its applications. This invention bridges UIO66-NH2 and GE-TiO2 through covalent chemical bonds (amide bonds), constructing a directional and efficient interfacial carrier transport channel, significantly suppressing the recombination of photogenerated electron-hole pairs, thereby greatly improving the photoelectrochemical water splitting performance of the material.

[0009] The composite photoanode was developed by in-situ growing UIO66-NH2 on the surface of graphene-reinforced titanium dioxide (GE-TiO2) photoanode via a hydrothermal method. Furthermore, a condensation reagent was used to induce a covalent condensation reaction between the amino groups in UIO66-NH2 and the carboxyl groups on the carboxyl-functionalized graphene surface, forming a stable amide bond bridging structure. This amide bond acts as a highly efficient interfacial carrier transfer channel, significantly suppressing the recombination of photogenerated electron-hole pairs, improving charge separation efficiency and migration rate, thereby greatly enhancing the photoelectrochemical (PEC) water splitting performance of the material.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a UIO66-NH2@GE-TiO2 (hereinafter, TiO2 is abbreviated as TO) composite photoanode based on interfacial amide bond modification includes the following steps: (1) Preparation of GE-TO photoanode: Titanium source, carboxyl-functionalized graphene and acidic aqueous solution are mixed to obtain precursor solution; conductive substrate is placed in the precursor solution for hydrothermal reaction to grow GE-TO composite structure on conductive substrate; after the reaction is completed, conductive substrate is washed, dried and then annealed to obtain GE-TO photoanode.

[0011] In this step, TO is directly grown on the surface of a conductive substrate in the presence of carboxyl-functionalized graphene using a hydrothermal method, forming a GE-TO composite structure. The introduction of carboxyl-functionalized graphene not only enhances the electron conductivity of the composite structure, but the carboxyl groups on its surface also provide reaction sites for the subsequent formation of amide bonds. The preferred titanium source is tetrabutyl titanate, a commonly used titanium source with advantages such as easily controllable hydrolysis rate and high product purity. The mass ratio of the titanium source to the carboxyl-functionalized graphene is 1:280~1:290. This ratio range ensures uniform dispersion of graphene and effective composite with TO. If the graphene ratio is too high, TO growth will be insufficient; if the ratio is too low, the electron transport enhancement effect of graphene cannot be fully utilized. The acidic aqueous solution is obtained by adjusting the pH of ultrapure water to 1.2~1.3 with concentrated hydrochloric acid. The acidic environment can regulate the hydrolysis rate of the titanium source, which is beneficial for the formation of a regular TO nanostructure.

[0012] The hydrothermal reaction is carried out at a temperature of 150-160℃ for 18-22 hours. Under these conditions, the TO crystals can grow fully, forming a well-formed and densely distributed nanostructure. The annealing treatment is carried out in an inert atmosphere (preferably nitrogen atmosphere), with the temperature raised to 350-450℃ and held for 2-3 hours at a heating rate of 5℃ / min. Annealing removes organic impurities from the precursor solution, improves the crystallinity and conductivity of the GE-TO composite structure, and the inert atmosphere prevents the graphene from being ablated. The conductive substrate is preferably FTO conductive glass, which has good conductivity and light transmittance, making it suitable as a substrate material for the photoanode. During the hydrothermal reaction, the conductive surface of the FTO conductive glass is placed in the reaction vessel at a 45° angle. This placement method is conducive to the uniform growth of the TO nanostructure and improves the light absorption efficiency.

[0013] (2) In-situ growth of UIO66-NH2 layer: Zirconium salt and amino-containing organic ligands are dissolved in an organic solvent, and an acid regulator is added to obtain a growth solution; the GE-TO photoanode obtained in step (1) is placed in the growth solution for hydrothermal reaction, so that UIO66-NH2 crystals are grown in-situ on the surface of the GE-TO photoanode to obtain a preliminary composite photoanode.

[0014] This step employs an in-situ hydrothermal method to directly grow UIO66-NH2 crystals on the surface of the GE-TO photoanode, ensuring a tight interfacial contact between UIO66-NH2 and GE-TO. The zirconium salt is preferably zirconium tetrachloride, which, as a zirconium source, exhibits high reactivity and high product purity. The amino-containing organic ligand is selected from one of 2-aminoterephthalic acid, 2,5-diaminoterephthalic acid, 2,6-diaminoterephthalic acid, dimethyl 2-aminoterephthalate, terephthalamide, terephthalic acid monoamide, N-substituted terephthalamide, or 2-aminoethyl terephthalate, preferably 2-aminoterephthalic acid, whose amino group can undergo a condensation reaction with the subsequent carboxyl group to form an amide bond, while the phthalic acid structure can form a stable coordination bond with the zirconium ion. The mass ratio of the zirconium salt to the amino-containing organic ligand is 1.2:1 to 1.5:1. This ratio range ensures that the organic ligand is fully coordinated to form a structurally stable UIO66-NH2 crystal.

[0015] The organic solvent is N,N-dimethylformamide (DMF). DMF has good solubility for zirconium salts and amino-containing organic ligands, providing a stable reaction environment for the growth of UIO66-NH2. The acid regulator is acetic acid, which can adjust the pH value of the reaction system and promote the regular growth of UIO66-NH2 crystals. The hydrothermal reaction is carried out at a temperature of 100~150℃ for 10~14h. Under these conditions, in-situ growth of UIO66-NH2 crystals can be achieved, resulting in regular crystal morphology and uniform dispersion. The GE-TO photoanode is placed in the reaction vessel at a 45° angle, which is beneficial for the uniform coverage of UIO66-NH2 crystals on its surface.

[0016] (3) Interfacial amide bond bridging: Dissolve the condensation reagent in a solvent to obtain an activation solution; immerse the preliminary composite photoanode obtained in step (2) into the activation solution to carry out a condensation reaction, so that the amino group in UIO66-NH2 and the carboxyl group on the surface of the carboxyl functionalized graphene form a covalent amide bond to obtain the UIO66-NH2@GE-TO composite photoanode.

[0017] This step constructs a covalent amide bond between UIO66-NH2 and GE-TO through a condensation reaction, enhancing interfacial bonding stability and simultaneously forming a highly efficient charge transfer channel. The condensation reagent includes a carbodiimide condensation reagent and hydroxybenzotriazole (HOBt), wherein the carbodiimide condensation reagent is selected from 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), N,N'-dicyclohexylcarbodiimide (DCC), or N,N'-diisopropylcarbodiimide (DIC), preferably EDCI. EDCI, as a water-soluble condensation reagent, can efficiently activate the carboxyl group, promoting the condensation reaction between the amino and carboxyl groups. HOBt can suppress side reactions and improve the efficiency of amide bond formation. The molar ratio of the carbodiimide condensation reagent to HOBt is 1:1 to 1:1.5, a range that ensures sufficient activation of the carboxyl group and improves the efficiency of the condensation reaction.

[0018] The solvent is a mixture of ethanol and deionized water in a mass ratio of 4:1. This mixed solvent has good solubility for the condensation reagent and ensures the stability of the initial composite photoanode. The pH of the activation solution is adjusted to 5-6, which is the optimal condition for the condensation reaction, significantly improving the reaction rate and amide bond formation efficiency. The condensation reaction is carried out at a temperature of 25-40℃ for 24-36 hours under light-protected conditions. Light protection prevents the condensation reagent from decomposing due to light exposure, ensuring the smooth progress of the reaction. Under these temperature and time conditions, amino and carboxyl groups can fully undergo the condensation reaction to form stable amide bonds. After the reaction, the composite photoanode is placed on a heating stage at 40-60℃ to evaporate residual solvent, then rinsed with anhydrous ethanol and dried to remove unreacted condensation reagent and impurities, obtaining a high-purity, stable composite photoanode.

[0019] This invention also provides a UIO66-NH2@GE-TO composite photoanode prepared by the above method based on interfacial amide bond modification. This composite photoanode achieves covalent bonding between UIO66-NH2 and GE-TO through amide bonds, resulting in stable interfacial bonding. Furthermore, the amide bonds act as efficient charge transfer channels, significantly promoting the separation of photogenerated electron-hole pairs, inhibiting their recombination, and improving photoelectrochemical performance. Under AM 1.5G simulated sunlight irradiation, 1.23V vs. RHE bias, and 1M Na2SO4 electrolyte conditions, the composite photoanode exhibits a photocurrent density ≥1.30 mA / cm² and a maximum photoelectric conversion efficiency (ABPE) ≥0.65%.

[0020] This invention further provides the application of the aforementioned UIO66-NH2@GE-TO composite photoanode modified with interfacial amide bonds in photoelectrochemical water splitting reactions. This composite photoanode exhibits excellent photoelectrocatalytic oxygen production performance in photoelectrochemical water splitting reactions, with high photocurrent density and good stability, providing novel material support for the efficient preparation of green hydrogen.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs covalent amide bonds between the amino groups of UIO66-NH2 and the carboxyl groups on the surface of carboxyl-functionalized graphene through an EDCI / HOBt condensation system, forming a stable heterogeneous interface. This significantly enhances the interfacial bonding stability between UIO66-NH2 and GE-TO, avoiding problems such as weak interfacial bonding and easy material detachment caused by physical effects in traditional composite methods, and improving the structural stability and service life of the composite photoanode.

[0022] 2. The constructed amide bonds serve as directional electron / hole transfer channels, effectively promoting the efficient migration of photogenerated holes from GE-TO to the UIO66-NH2 surface to participate in the water oxidation reaction. Simultaneously, they significantly suppress interfacial charge recombination and surface carrier accumulation, improving charge separation efficiency and interfacial reaction kinetics, thereby greatly enhancing the photoelectrochemical performance of the composite photoanode. Experiments show that the composite photoanode achieves a photocurrent density of 1.30 mA / cm² (1.23 V vs. RHE) under standard AM 1.5G illumination, a 57% improvement over GE-TO, with a maximum photoelectric conversion efficiency (ABPE) of 0.65%.

[0023] 3. The preparation method of the present invention adopts hydrothermal method and solution soaking condensation process, which is simple to operate, mild and easy to control, without the need for complicated equipment and harsh reaction conditions, and is suitable for large-scale production.

[0024] 4. The composite photoanode material of the present invention has excellent photoelectrochemical water splitting performance and has broad application prospects in the field of green hydrogen energy production, providing a new technical solution for solving energy crisis and environmental problems. Attached Figure Description

[0025] Figure 1 The UV-Vis diffuse reflectance absorption spectrum (UV-Vis DRS) of the GE-TO photoanode. Figure 2 X-ray diffraction (XRD) pattern of the GE-TO photoanode; Figure 3 SEM image of the GE-TO photoanode; Figure 4 SEM image of the preliminary UIO66-NH2 / GE-TO composite photoanode; Figure 5 SEM image of the interface amide bond modified UIO66-NH2@GE-TO composite photoanode; Figure 6 Fourier transform infrared (FT-IR) spectrum of UIO66-NH2@GE-TO composite photoanode modified with amide bonds at the interface; Figure 7 Linear sweep voltammetry (LSV) curves for different photoanodes at 1.23 V vs. RHE; Figure 8 This is an ABPE diagram of the composite photoanode of the present invention; Figure 9 This is the OCP diagram of the composite photoanode of the present invention; Figure 10 This is the EIS image of the composite photoanode of the present invention; Figure 11This is a diagram showing the LSV curves (without illumination) of the composite photoanode of the present invention. Figure 12 This is a graph showing the relationship between the current density and the scanning rate of the composite photoanode of this invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0027] Example 1: Preparation of UIO66-NH2@GE-TO composite photoanode modified with interfacial amide bonds (1) Preparation of GE-TO photoanode: 30 mL of ultrapure water was adjusted to pH 1.25 with concentrated hydrochloric acid, and 0.81 g of tetrabutyl titanate and 0.09 g of carboxyl-functionalized graphene were added. The mixture was magnetically stirred for 30 min at room temperature and ultrasonically dispersed for 30 min to form a uniform light brown precursor sol. A 2 cm × 2 cm FTO conductive glass substrate (after cleaning) was placed at a 45° angle in a 50 mL polytetrafluoroethylene-lined high-pressure reactor with the conductive side facing down, and the above sol was injected. The reactor was sealed and placed in an oven for hydrothermal reaction at 150 °C for 20 h. The FTO substrate was removed and rinsed three times each with ultrapure water and anhydrous ethanol, and then vacuum dried at 60 °C for 2 h. Subsequently, it was transferred to a tube furnace and heated to 400 °C at a rate of 5 °C / min under a nitrogen atmosphere, held at that temperature for 2 h, naturally cooled to room temperature, rinsed with ultrapure water, and dried in air to obtain the GE-TO photoanode.

[0028] Characterize the sample as follows: Figure 1 As shown, the Tauc plot method was used to draw a tangent line to the linear region of the (αhν)¹ / ²–hν curve, and the extrapolation to the x-axis intercept was approximately 414 nm (based on this, its optical band gap Eg = 1240 / λ ≈ 2.88 eV was calculated). Figure 2 As shown, the XRD diffraction peaks are in high agreement with the anatase TO standard card (JCPDS No. 21-1272), and no other extraneous peaks are observed, indicating that the amount of carboxyl-functionalized graphene is small or highly dispersed. Figure 3 As shown, TO is uniformly grown on the surface of FTO conductive substrate in the form of a vertically oriented one-dimensional nanorod array. The nanorods are about 50–100 nm in diameter, with regular morphology and dense distribution, indicating that hydrothermal conditions effectively regulate the crystal growth orientation, which is beneficial to light absorption and charge carrier transport. The nanorod tips are elliptical, indicating the successful loading of carboxyl-functionalized graphene.

[0029] (2) Preparation of the preliminary UIO66-NH2 / GE-TO composite photoanode: 0.77 g ZrCl4 and 0.06 g 2-aminoterephthalic acid were added to 30 mL N,N-dimethylformamide (DMF) and stirred at room temperature for 30 min to allow it to initially dissolve. Then, 7 mL acetic acid was added and the mixture was sonicated for 30 min to obtain a clear precursor solution. The GE-TO photoanode obtained in step (1) was placed at a 45° angle in a 50 mL polytetrafluoroethylene-lined autoclave, and the above solution was injected. The reaction was carried out at 120°C for 12 h using hydrothermal treatment. After removal, the photoanode was washed three times each with DMF and methanol to remove unreacted substances. It was then dried under vacuum at 60°C to obtain the preliminary UIO66-NH2 / GE-TO composite photoanode.

[0030] like Figure 4 As shown, SEM images reveal that irregular polyhedral UIO66-NH2 particles with a size of approximately 200 nm were successfully loaded onto the surface of TO nanorods. The morphological characteristics are consistent with those of the UIO66 series of metal-organic framework materials, indicating that UIO66-NH2 has been successfully grown in situ on the GE-TO surface.

[0031] (3) Preparation of amide-bridged UIO66-NH2@GE-TO composite photoanode: 0.215 g EDCI and 0.212 g HOBt were dissolved in 20 mL of ethanol / deionized water mixed solvent (mass ratio 4:1), and the pH was adjusted to 5.5 using an acetate-sodium acetate buffer system. The preliminary composite photoanode obtained in step (2) was immersed in this activation solution and reacted at 30℃ in the dark for 36 h. After removal, it was placed on a 50℃ heating stage to evaporate the residual solvent, then rinsed three times with anhydrous ethanol, and dried under vacuum at 60℃ to obtain the UIO66-NH2@GE-TO composite photoanode bridged by covalent amide bonds.

[0032] Characterize the sample as follows: Figure 5 As shown, after amide bond bridging, the surface morphology changes to some extent, and the bonding becomes tighter. For example... Figure 6 As shown, a distinct amide I band (C=O stretching vibration) characteristic peak appeared near 1633 cm⁻¹ in the FT-IR spectrum, and amide bonds (N–H bending + C–N stretching) were observed at 1310–1200 cm⁻¹. Combined with the characteristic peak of UIO66-NH2, it is confirmed that a covalent amide bond was successfully formed between the amino group of UIO66-NH2 and the carboxyl group of the carboxyl-functionalized graphene.

[0033] Comparative Example 1: Only TO photoanodes were prepared (same as step (1) in Example 1), without UIO66-NH2 loading and amide bond bridging.

[0034] Comparative Example 2: A preliminary composite photoanode of UIO66-NH2 / GE-TO was prepared (same as step (2) of Example 1), but without the amide bond bridging treatment in step (3).

[0035] Example 2: PEC performance testing of photoanode materials The photoanodes obtained in Example 1, Comparative Example 1, and Comparative Example 2 were used as working electrodes, forming a three-electrode system with a platinum sheet counter electrode and an Ag / AgCl reference electrode. Photoelectrochemical tests were conducted in 1 M Na2SO4 electrolyte using an AM 1.5G simulated solar light source (100 mW / cm²).

[0036] Figure 7 Linear sweep voltammetry (LSV) curves (AM 1.5G, 100 mW / cm²) are shown for different photoanodes at 1.23 V vs. RHE. The photocurrent density of GE-TO modified with UIO66-NH2 was 0.83 mA / cm², while that of the composite photoanode modified with UIO66-NH2 and bridged by amide bonds increased to 1.30 mA / cm², an increase of 57%. This significant improvement is attributed to: (i) UIO66-NH2 acting as a hole transport layer to suppress surface hole accumulation; and (ii) amide bonds acting as directional electron channels to accelerate interfacial charge separation and reduce recombination losses.

[0037] Figure 8 The figures show the Applied Bias Photon-to-Current Efficiency (ABPE) curves for the composite photoanode. The maximum ABPE value of the interface amide-modified UIO66-NH2@GE-TO composite photoanode reaches 0.65%, occurring at approximately 0.65V vs. RHE, indicating that this material can achieve efficient solar-to-hydrogen energy conversion under relatively low applied bias voltage, demonstrating good potential for photoelectrochemical water splitting applications.

[0038] Figure 9 The Open Circuit Potential (OCP) curves for the composite photoanode are shown. The maximum OCP value of the interface amide bond-modified UIO66-NH2@GE-TO composite photoanode reaches 0.207 V vs. RHE, indicating that the material has high electrochemical activity, low corrosion tendency, and good potential for photoelectrochemical water splitting applications.

[0039] Figure 10The image shows the Electrochemical Impedance Spectroscopy (EIS) curves of the composite photoanode. The composite photoanode modified with UIO66-NH2 and bridged by amide bonds exhibits the smallest semicircle, indicating that the charge transfer kinetics at the electrode / electrolyte interface are faster during water oxidation.

[0040] Figure 11 The figures show the linear sweep voltammetry (LSV) curves of the composite photoanode without illumination. The composite photoanode modified with UIO66-NH2 and bridged by amide bonds exhibits a minimum of 2.46 V vs. RHE, indicating that amide bond bridging significantly enhances the OER kinetics of the composite photoanode.

[0041] Figure 12 The curves showing the relationship between the current density and the scan rate of the composite photoanode indicate that the composite photoanode modified with UIO66-NH2 and bridged by amide bonds has a larger active surface area, suggesting that the bridging of amide bonds increases the active sites for the OER reaction of the photoanode.

[0042] In summary, the UIO66-NH2@GE-TO composite photoanode provided by this invention, based on interfacial amide bond modification, constructs covalent amide bonds between the amino groups of UIO66-NH2 and the carboxyl groups on the surface of carboxyl-functionalized graphene through an EDCI / HOBt condensation system, forming a stable heterogeneous interface. This amide bond acts as a directional electron / hole transfer channel, promoting the efficient migration of photogenerated holes from GE-TO to the UIO66-NH2 surface to participate in the water oxidation reaction, while effectively suppressing interfacial charge recombination and surface carrier accumulation, significantly improving charge separation efficiency and interfacial reaction kinetics. Experiments show that this composite photoanode achieves a photocurrent density of 1.30 mA / cm² (1.23 V vs. RHE) under standard AM 1.5G illumination, a 57% improvement over GE-TO, with a maximum ABPE of 0.665%, providing a novel photoanode material with both high activity and stability for efficient photoelectrochemical water splitting.

Claims

1. A method for preparing a UIO66-NH2@GE-TiO2 composite photoanode based on interfacial amide bond modification, characterized in that, Includes the following steps: (1) Preparation of GE-TiO2 photoanode: Titanium source, carboxyl-functionalized graphene and acidic aqueous solution are mixed to obtain precursor solution; A conductive substrate was placed in a reactor containing a precursor solution for hydrothermal reaction to grow a GE-TiO2 composite structure on the substrate. After the reaction was completed, the substrate was removed, washed, dried, and then annealed to obtain a GE-TiO2 photoanode. (2) In-situ growth of UIO66-NH2 layer: Zirconium salt and amino-containing organic ligands are dissolved in an organic solvent, and an acid regulator is added to obtain a growth solution; the GE-TiO2 photoanode obtained in step (1) is placed in the growth solution for hydrothermal reaction, so that UIO66-NH2 crystals are grown in situ on the surface of the GE-TiO2 photoanode to obtain a preliminary composite photoanode; (3) Interfacial amide bond bridging: Dissolve the condensation reagent in the solvent to obtain an activation solution; immerse the preliminary composite photoanode obtained in step (2) into the activation solution to carry out a condensation reaction, so that the amino group in UIO66-NH2 and the carboxyl group on the surface of the carboxyl functionalized graphene in GE-TiO2 form a covalent amide bond, and obtain the UIO66-NH2@GE-TiO2 composite photoanode.

2. The preparation method according to claim 1, characterized in that, In step (1), the titanium source is tetrabutyl titanate; the mass ratio of the titanium source to carboxyl-functionalized graphene is 1:280~1:290; the acidic aqueous solution is obtained by adjusting the pH of ultrapure water to 1.2~1.3 with concentrated hydrochloric acid.

3. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the hydrothermal reaction is 150~160℃ and the time is 18~22h; the annealing treatment is carried out in an inert atmosphere, the temperature is raised to 350~450℃ and held for 2~3h, and the heating rate is 5℃ / min.

4. The preparation method according to claim 1, characterized in that, In step (2), the zirconium salt is zirconium tetrachloride; the amino-containing organic ligand is selected from one of 2-aminoterephthalic acid, 2,5-diaminoterephthalic acid, 2,6-diaminoterephthalic acid, dimethyl 2-aminoterephthalate, terephthalamide, terephthalic acid monoamide, N-substituted terephthalamide, and 2-aminoethyl terephthalate; the mass ratio of the zirconium salt to the amino-containing organic ligand is 1.2:1 to 1.5:

1.

5. The preparation method according to claim 1, characterized in that, In step (2), the organic solvent is N,N-dimethylformamide, and the acid regulator is acetic acid; the temperature of the secondary hydrothermal reaction is 100~150℃, and the time is 10~14h.

6. The preparation method according to claim 1, characterized in that, In step (3), the condensing agent includes a carbodiimide condensing agent and hydroxybenzotriazole; the carbodiimide condensing agent is selected from 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N,N'-dicyclohexylcarbodiimide or N,N'-diisopropylcarbodiimide; the molar ratio of the carbodiimide condensing agent to hydroxybenzotriazole is 1:1 to 1:1.

5.

7. The preparation method according to claim 4, characterized in that, In step (3), the solvent is a mixture of ethanol and deionized water in a mass ratio of 4:1, the pH of the activation solution is adjusted to 5-6, the temperature of the condensation reaction is 25-40℃, the time is 24-36h, and the reaction is carried out under light-protected conditions.

8. A UIO66-NH2@GE-TiO2 composite photoanode based on interfacial amide bond modification, prepared by the method according to any one of claims 1 to 7.

9. The application of the UIO66-NH2@GE-TiO2 composite photoanode modified with interfacial amide bonds as described in claim 8 in photoelectrochemical water splitting reaction.

Images