Energy storage type organic-inorganic hybrid semiconductor composite film and preparation and photoanode applications thereof

Abstract

The present application belongs to the field of photoelectrochemical cathodic protection, and particularly relates to an energy storage type organic-inorganic hybrid semiconductor composite film (WO3@TpBpy-COF@Bi2S3) and preparation and photoanode application thereof. A functional organic semiconductor (covalent organic framework material COF) is used as an intermediate phase, inorganic semiconductors are connected through surface modification, covalent bonding and coordination complex to form a stable multi-phase heterogeneous organic-inorganic hybrid semiconductor composite film. The composite film is used as a photoanode, under simulated sunlight irradiation, the protected metal can be fully cathodically polarized, and after the light is turned off, the cathodic protection can be continuously provided, and the stability is good.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrochemical cathodic protection. Specifically, this invention relates to an energy storage type organic-inorganic hybrid semiconductor composite film (WO3@TpBpy-COF@Bi2S3), its preparation, and its photoanode application. Background Technology

[0002] Metal corrosion has a serious impact on the environment and economy. Photoelectrochemical cathodic protection technology is a green metal corrosion protection technology that does not require an external power source and does not sacrifice the anode material, meeting the concepts of green chemistry and sustainable development. This technology transfers photogenerated electrons generated by a semiconductor photoanode under sunlight to the metal surface, causing a negative shift in the potential of the protected metal, thereby inhibiting metal corrosion. It has great application potential in the field of metal corrosion protection. However, semiconductor materials can only generate photogenerated electrons under light conditions. When the light stops, the cathodic protection of the metal also stops, thus limiting its application in the absence of light.

[0003] Therefore, inventing and constructing energy storage semiconductor photoanodes is of great significance for developing green metal corrosion protection technologies. On the one hand, energy storage semiconductor photoanodes can be photoexcited under light conditions to exhibit photocathode protection effects; on the other hand, by storing photogenerated electrons generated under illumination and then releasing and utilizing them in the dark, they can continue to exert cathodic protection effects. However, currently proposed energy storage photoanodes all suffer from problems such as structural instability and short dark-state protection time. Therefore, the invention of novel, long-lasting, and stable energy storage semiconductor photoanodes remains very urgent.

[0004] Covalent organic frameworks (COFs), constructed from organic units through strong covalent bonds, are porous crystalline materials possessing excellent chemical and thermal stability, visible light absorption, high photoconductivity, negative potential, and tunable structure, making them promising candidates for photoelectrochemical continuous cathodic protection. However, related studies have shown that the interaction between inorganic and organic components is often very weak. The weak coupling between composite material components leads to poor interfacial charge transfer efficiency, insufficient surface constraint, and poor structural stability. Therefore, it is urgent to develop long-lasting, stable covalently bonded organic-inorganic hybrid photoanodes by appropriately modifying the surface of inorganic substrates with appropriate functionalization. Summary of the Invention

[0005] The purpose of this invention is to provide an energy storage type organic-inorganic hybrid semiconductor composite film (WO3@TpBpy-COF@Bi2S3), its preparation, and its photoanode application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing an energy storage organic-inorganic hybrid semiconductor composite film involves using a functional organic semiconductor (covalent organic framework material COFs) as an intermediate phase, and connecting inorganic semiconductors through surface modification, covalent bonding, and coordination complexation to form a stable multiphase heterogeneous organic-inorganic hybrid semiconductor composite film.

[0008] A nanoflower array inorganic WO3 film was grown on a conductive Ti substrate. Then, the WO3 film underwent surface modification by aminoation and COF monomer aldehyde grouping to obtain a functionalized WO3 surface. Subsequently, a thin layer of a covalent organic framework TpBpy-COF material was grown in situ on the functionalized WO3 surface via covalent bonding. Finally, the N atoms distributed within the bipyridine units of the covalent organic framework TpBpy-COF thin layer were used to coordinate and complex Bi atoms. 3+ Re-adsorb S 2- Anchoring of inorganic semiconductor Bi2S3 material in TpBpy-COF was achieved, resulting in a multiphase heterogeneous organic-inorganic hybrid semiconductor composite film WO3@TpBpy-COF@Bi2S3 with a flower-like array three-layer core-shell structure connecting WO3 and Bi2S3 at both ends using TpBpy-COF as the intermediate medium.

[0009] Specifically

[0010] 1) Preparation of WO3 nanoflower array film: WCl6 was added to anhydrous ethanol and mixed to form a clear yellow solution. The etched Ti sheet was used as the substrate for film growth. The clear yellow solution was then transferred to a Teflon-lined autoclave containing the etched Ti sheet and reacted at 140-180℃ for 22-26 hours. After the reaction, the Ti sheet was removed, rinsed, dried, and calcined to grow a WO3 nanoflower array film on the Ti substrate.

[0011] 2) WO3 film surface functionalization: First, the Ti substrate with the WO3 nanoflower array film obtained in step 1 was immersed in an ethanol solution for 20-30 minutes. Then, 100-300 μL of 3-aminopropyltriethoxysilane was added dropwise with stirring. The mixture was stirred at room temperature for 10-12 hours. The substrate was then removed, washed, and dried to grow an amino-functionalized WO3-NH2 film on the Ti substrate surface. The substrate was then placed in a 1,4-dioxane solution. 0.3-0.5 mM of 1,3,5-trialdehyde phloroglucinol (Tp) and 1-1.5 mM of glacial acetic acid were added to the system. The mixture was stirred at room temperature for 2-4 hours, washed, and dried to grow a Tp monomer-aldehyde-functionalized WO3-CHO film on the Ti substrate.

[0012] 3) Preparation of covalently bonded WO3@TpBpy-COF: 1,3,5-trimethylbenzene was added to 1,4-dioxane at a mass ratio of 1:1 and mixed. After mixing, 1,3,5-trialdehyde phloroglucinol with a final concentration of 0.7-1.0 mM and 5,5'-diamino-2,2'-bipyridine with a final concentration of 1.5-2.0 mM were added and mixed to obtain a mixed solution. The mixed solution was poured into a reaction vessel containing a Ti sheet with aldehyde-modified WO3-CHO synthesized in step 2, so that the titanium sheet was submerged. The reaction was carried out at 100-120℃ for 60-72 hours. After the reaction, the film was removed, washed and dried to obtain a covalently bonded WO3@TpBpy-COF composite film grown on a Ti substrate.

[0013] 4) Synthesis of WO3@TpBpy-COF@Bi2S3: The Ti sheet with WO3@TpBpy-COF grown in step 3 was immersed in an ethylene glycol solution containing 0.1-0.3M Bi(NO3)3·5H2O, stirred, and left to stand for 20-24 hours. After sealing, it was kept at a constant temperature of 60-80℃ for 10-12 hours. After cooling, it was cleaned and dried. After drying, the Ti sheet was immersed in a methanol solution containing 0.2-0.4M Na2S·9H2O for 2-3 hours, then cleaned and dried to form a multiphase heterogeneous organic-inorganic hybrid semiconductor composite film WO3@TpBpy-COF@Bi2S3 on the surface of the Ti sheet.

[0014] The Ti substrate for etching is prepared by placing a clean Ti wafer in concentrated hydrochloric acid (12M concentration) heated to 80-95℃ for 40-60 minutes, rinsing it with deionized water, and drying it in an oven at 60-80℃. The substrate is then placed in a reaction vessel with the substrate at a 45° angle to the vessel wall and the growth surface facing down.

[0015] In step 1), after the reaction, the Ti wafer with the WO3 film is rinsed with anhydrous ethanol and deionized water and dried in air at 60–80°C. Then, the sample is heated at 440–450°C (heating rate = 5°C / min). -1 The nanoflower array WO3 film grown on the Ti substrate was obtained by calcining in air for 1.7 to 2.2 hours.

[0016] In step 2), the Ti sheet with the WO3 film of nanoflower array grown on the surface is taken out, washed alternately with ethanol and distilled water, and dried in air at 60-80°C.

[0017] After the reaction in step 3), the titanium sheet is washed alternately with acetone and distilled water, and then dried in air at 60°C.

[0018] Step 4) is maintained at a constant temperature of 60-80℃ for 10-12 hours. After cooling, the Ti sheet is washed with ethylene glycol and deionized water and completely dried in air at 60-80℃. After drying, the Ti sheet is immersed in a methanol solution containing 0.2-0.4M Na2S·9H2O for 2-3 hours, then washed with methanol and deionized water and completely dried at 60-80℃.

[0019] An energy storage type organic-inorganic hybrid semiconductor composite film prepared by the method described herein, wherein the multiphase heterogeneous organic-inorganic hybrid semiconductor composite film WO3@TpBpy-COF@Bi2S3 with a three-layer core-shell structure of nanoflower array is prepared by the method described herein.

[0020] An application of the aforementioned energy storage organic-inorganic hybrid semiconductor composite film as a photoanode, wherein the composite film is used in the preparation of energy storage organic-inorganic hybrid semiconductor photoanodes as long-lasting photocathode protection and corrosion prevention to inhibit metal corrosion.

[0021] The present invention provides a WO3@TpBpy-COF@Bi2S3 hybrid composite film with a flower-like array three-layer core-shell structure, using TpBpy-COF as the intermediate medium and connecting WO3 and Bi2S3 at both ends. This achieves controllable hybrid composite of organic and inorganic semiconductors, rather than simple mixing, to obtain a WO3@TpBpy-COF@Bi2S3 hybrid photoanode.

[0022] The hybrid composite photoanode includes a photoelectric conversion layer, an electron storage layer, and a conductive layer. The WO3@TpBpy-COF@Bi2S3 composite material serves as the semiconductor photoelectric conversion and electron storage layer, and the Ti substrate serves as the conductive layer. A portion of the Ti conductive surface is scraped off from the prepared material surface, and insulating adhesive is applied at the junction to form an energy storage hybrid composite photoanode.

[0023] The photoelectrochemical cathodic protection effect of the prepared WO3@TpBpy-COF@Bi2S3 energy storage organic-inorganic hybrid photoanode was tested. Specifically, the changes in photoinduced open-circuit potential and photogenerated current density were used for characterization. These were measured by recording the changes in photogenerated current density and open-circuit potential over time under on / off lighting conditions. Furthermore, by integrating the photoinduced current density curve, the charge of photogenerated electrons provided by the photoanode to the metal electrode under illumination and the charge of continuous discharge from the photoanode to the metal electrode in the dark state after the illumination was cut off were obtained. The storage and slow-release photogenerated electron performance of the WO3@TpBpy-COF@Bi2S3 photoanode was investigated. Specifically, the measuring device consisted of two reaction cells: a corrosion cell and a photoelectrochemical cell. The photoelectrochemical cell contained 0.25 mol L... -1 Na2S and 0.35 mol L -1The corrosion tank contained a Na2SO3 solution and a 3.5 wt% NaCl solution, with the two reaction tanks connected by a salt bridge. The photoanode was placed in the photoelectrochemical tank, and the protected metal electrode 316L SS was placed in the corrosion tank. The light source used in this study was a 300-W xenon lamp (PLS-SXE300, Beijing Bofei Lighting Co., Ltd., China). Simulated sunlight was obtained by adding an AM1.5 filter to the light source. The illumination intensity was 100 mW / cm². 2 These tests were conducted under intermittent simulated sunlight. A quartz window, approximately 30 mm in diameter, is located at the center of the front of the photovoltaic cell, through which incident light illuminates the photoanode surface.

[0024] The basic principle of this invention:

[0025] In this invention, functional TpBpy-COF is used as an intermediate "bridge" to covalently connect WO3 and Bi2S3 to form a stable three-phase heterogeneous WO3@TpBpy-COF@Bi2S3 composite photoanode. First, the surface of the nano-spiky clusters of energy-storing WO3 is functionalized using a silane coupling agent and Tp monomer to achieve the bonding growth of TpBpy-COF on the WO3 surface. Second, the abundant N atoms distributed in the bipyridine units of TpBpy-COF coordinate to complex Bi2S3. 3+ and further adsorb S 2- This invention achieves the anchoring of Bi2S3 material in COF. TpBpy-COF, with its excellent photoelectric properties, and Bi2S3 together serve as the photoelectric conversion functional components of the composite photoanode, charging and storing energy for WO3. Therefore, the WO3@TpBpy-COF@Bi2S3 composite hybrid photoanode of this invention can provide efficient and continuous photoelectrochemical cathodic protection for metals, and also exhibits good stability.

[0026] Advantages of this invention:

[0027] This invention covalently combines organic semiconductor TpBpy-COF and inorganic semiconductor WO3, and anchors Bi2S3 through ionic complexation to construct a three-layer core-shell structure WO3@TpBpy-COF@Bi2S3 nanoflower array hybrid photoanode for photoelectrochemical cathodic protection. By surface functionalizing WO3, in-situ covalent recombination of TpBpy-COF with excellent visible light response on the WO3 surface was achieved. The obtained interfacially covalently bonded composite photoanode exhibits effective photoelectrochemical cathodic protection. More importantly, the covalently bonded WO3@TpBpy-COF@Bi2S3 photoanode shows significantly greater application stability than non-covalently bonded photoanodes. As an innovative attempt to construct a COF bridge to covalently connect the semiconductors at both ends for photoelectrochemical cathodic protection, this invention demonstrates the superiority of covalent bonds in multiphase heterogeneous composite photoanodes for photogenerated charge separation and transfer, and for improving the stability of photoanode photoelectrochemical cathodic protection applications. The three-phase heterogeneous composite material is designed and prepared with a tight bond, exhibiting excellent thermal and chemical stability, as well as improved interfacial charge transfer efficiency, significantly enhancing photoelectrochemical performance. Given the established good performance, the preparation method of this invention can be extended not only to the field of photoelectrochemical cathodic protection, but also to other semiconductor composite functional material applications, providing new ideas for improving the performance and stability of multi-component composite functional materials. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the preparation and synthesis of the organic-inorganic hybrid photoanode according to an embodiment of the present invention.

[0029] Figure 2 Scanning electron microscope images of the photoanode materials provided in the embodiments of the present invention: (A) WO3, (B) WO3@TpBpy-COF and (C) WO3@TpBpy-COF@Bi2S3 photoanode.

[0030] Figure 3 EDS spectrum and mapping diagram of WO3@TpBpy-COF@Bi2S3 photoanode provided in the embodiments of the present invention.

[0031] Figure 4 This is an analysis diagram of covalent bonding between an organic-inorganic hybrid photoanode and an embodiment of the present invention.

[0032] Figure 5 A diagram of a photoelectrochemical cathodic protection testing device for photoelectric materials provided in an embodiment of the present invention.

[0033] Figure 6 The variations in photoinduced open-circuit potential (A, B) and photoinduced current density (C, D) of a 316L SS electrode coupled to a photoanode under intermittent simulated sunlight irradiation provided in this embodiment of the invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and examples, but this description does not limit the invention in any way.

[0035] This invention uses functional organic semiconductors (covalent organic framework materials, COFs) as an intermediate bridge to covalently connect inorganic semiconductors (energy storage WO3 and Bi2S3) to form a stable multiphase heterogeneous organic-inorganic hybrid composite film. Specifically, firstly, a nanoflower array WO3 film is grown on a conductive Ti substrate. Then, the WO3 is successively modified by surface amylation and Tp monomer aldehyde modification. Subsequently, a covalent organic framework TpBpy-COF material is covalently bonded and grown in situ on the functionalized WO3 surface. Finally, the abundant N atoms distributed in the bipyridine units of TpBpy-COF coordinate and complex Bi2S3. 3+ and further adsorb S 2- This study achieved the anchoring of Bi2S3 materials in COF, resulting in an energy storage WO3@TpBpy-COF@Bi2S3 hybrid composite film material with excellent photoelectrochemical performance. Using the composite film as a photoanode, it can fully cathodically polarize the protected metal under simulated sunlight irradiation, and also provides continuous cathodic protection even when the light is off, exhibiting good stability.

[0036] Example 1

[0037] Fabrication of an energy storage type organic-inorganic hybrid semiconductor WO3@TpBpy-COF@Bi2S3 photoanode.

[0038] 1) Place a clean titanium sheet (1×2cm) 2 The substrate was etched in concentrated hydrochloric acid (12M) heated to 90℃ for 60 min, rinsed with deionized water and dried in an oven at 80℃ to obtain an etched Ti substrate for use as a substrate for photoanodine synthesis.

[0039] 2) Add 1.0 g WCl6 to 50 ml of anhydrous ethanol, stir to form a clear yellow solution, then transfer the solution to a 100 mL reactor containing an etched Ti substrate (the Ti substrate obtained in step 1 is placed at a 45° angle to the inner wall of the reactor). React at 180 °C for 22 hours. After the reactor cools, remove the Ti substrate with the WO3 film, rinse with deionized water, air-dry at 80 °C, and then calcine in air at 550 °C for 2 hours at a heating rate of 10 °C / min to obtain a photoanode with WO3 grown in situ on the Ti substrate.

[0040] 3) The WO3 photoelectrode obtained in step 2 was immersed in 50 mL of ethanol solution for 30 minutes. Then, 100 μL of 3-aminopropyltriethoxysilane was slowly added dropwise under vigorous stirring, and the mixture was stirred continuously at room temperature for 10 hours. The WO3 photoelectrode was then removed, washed alternately with ethanol and distilled water, and dried in air at 60 °C to obtain an amino-functionalized WO3-NH2 photoelectrode. The prepared WO3-NH2 photoelectrode was placed in 30 mL of 1,4-dioxane solution, and then 2.7 mg of 1,3,5-trialdehyde phloroglucinol and 0.3 mL of 3 mol / L ethanol solution were added, respectively. -1 Glacial acetic acid was added to the solution, stirred at room temperature for 2 hours, washed and dried to obtain the WO3-CHO photoelectrode.

[0041] 4) Add 15 mL of 1,3,5-trimethylbenzene to 15 mL of 1,4-dioxane and sonicate for 20 minutes. Then, add 5.3 mg of 1,3,5-trialdehyde phloroglucinol and 6.4 mg of 5,5'-diamino-2,2'-bipyridine to the mixture and sonicate for another 20 minutes. Afterward, pour the mixture into a 50 mL reactor containing a WO3-CHO photoelectrode (tilted, composite side down) and react at 120°C for 72 hours. After the reaction, remove the photoelectrode, wash it alternately with acetone and distilled water, and dry it to obtain the WO3@TpBpy-COF photoelectrode.

[0042] 5) Immerse the WO3@TpBpy-COF photoelectrode in an ethylene glycol solution containing 0.17M Bi(NO3)3·5H2O, stir for 20 minutes, let stand for 24 hours, seal, and maintain at a constant temperature of 70℃ for 12 hours. After cooling, clean the photoelectrode with ethylene glycol and deionized water, and dry completely in air at 80℃. Then, apply the Bi complexed... 3+ The WO3@TpBpy-COF photoelectrode was immersed in a 0.23M Na2S·9H2O methanol solution for 3 hours, then washed with methanol and deionized water and completely dried at 80°C to obtain the WO3@TpBpy-COF@Bi2S3 photoelectrode (see [link to documentation]). Figure 1-3 ).

[0043] Figure 1A schematic diagram of the synthesis of the WO3@TpBpy-COF@Bi2S3 composite photoelectrode is presented. Through surface modification, the WO3 synthesized via a solvothermal method was further functionalized with aldehyde groups to facilitate in-situ growth of the COF material: 3-aminopropyltriethoxysilane (APTES), a typical aminosilane coupling agent, was added to an ethanol solution containing the WO3 electrode to synthesize surface-amino-modified WO3-NH2. Then, WO3-NH2 was reacted with one of the monomers Tp used in the synthesis of TpBpy-COF, utilizing the Schiff base reaction between -CHO and -NH2 on the WO3 surface to obtain Tp-aldehyde-functionalized WO3-CHO. Subsequently, WO3-CHO was used as a special Tp monomer to synthesize covalently bonded in-situ grown WO3@TpBpy-COF material with Bpy. Finally, the abundant N atoms in the WO3@TpBpy-COF material framework were used to coordinate and complex Bi. 3+ and further adsorb S 2- This allows for the anchoring of Bi2S3 material in COF, resulting in a WO3@TpBpy-COF@Bi2S3 photoelectrode.

[0044] Figure 2 SEM images of the photoanode prepared in this invention are provided. Image set A (A1-A3) shows the WO3 photoelectrode at different magnifications. As can be clearly observed from the images, the WO3 grown on the Ti substrate is a highly ordered array of nanoflowers formed by the self-assembly of nanosheets. The array is dense and uniform on the substrate, with the nanoflower clusters having a diameter of approximately 4 μm. High-magnification images show (…). Figure 2 A3), with petal thickness approximately 20-50 nm. The microstructure of the WO3@TpBpy-COF composite photoelectrode obtained after surface modification is shown below. Figure 2 As shown in Figure B (B1-B4), the microstructure of the photoelectrode did not change significantly after TpBpy-COF composite, maintaining the nanoflower array morphology. The macroscopic display of WO3@TpBpy-COF successfully composited the dark red TpBpy-COF component. Therefore, it can be inferred that TpBpy-COF and WO3 composited through a core-shell structure, with TpBpy-COF growing and coating the WO3 sheet-like surface. This inference can also be derived from... Figure 2 As confirmed by the B3 high-magnification micrograph, the sheet-like surface of the WO3@TpBpy-COF composite photoelectrode is smoother and flatter than that of pure WO3, indicating that a TpBpy-COF thin layer was grown in situ on the WO3 surface. The microstructure of the prepared WO3@TpBpy-COF@Bi2S3 is as follows. Figure 2As shown in Figure C (C1-C4), consistent with WO3@TpBpy-COF, it still maintains the nanoflower array. Magnified images reveal a continuous, dense layer of nanoparticles on the sheet-like surface of WO3@TpBpy-COF@Bi2S3, indicating the successful preparation of a dense Bi2S3 functional layer via ion complexation and adsorption. Therefore, as... Figure 2 As shown in (A4 / B4 / C4), the WO3@TpBpy-COF@Bi2S3 composite photoelectrode is preliminarily deduced to be a three-layer core-shell structure with a nanoflower array morphology. It is worth noting that during the fabrication of the composite photoelectrode, the composite components all use WO3 as the core, growing controllably on its surface rather than simply stacking, while still maintaining a high specific surface area nanoflower array morphology. This is attributed to the rational design of the composite material, which lays the structural foundation for its excellent performance.

[0045] Figure 3 EDS and mapping images of the photoanode prepared in this invention are provided. To further verify the above hypothesis that TpBpy-COF and Bi2S3 components are coated as thin layers on the outside of WO3 nanoflowers, EDS and mapping characterization were performed to examine the elemental composition and distribution of the WO3@TpBpy-COF@Bi2S3 composite photoelectrode. Figure 3 As shown, EDS reveals that the photoelectrode of the nanoflower array contains W, O, C, N, Bi, and S elements, corresponding to WO3, TpBpy-COF, and Bi2S3 components, respectively, indicating the successful composite of the multiphase photoelectrode. Elemental mapping shows that each element is uniformly distributed on the nanoflower morphology, proving that the TpBpy-COF and Bi2S3 components are uniformly deposited as dense, continuous thin layers on the WO3 surface. EDS and mapping characterization confirm the successful fabrication of the WO3@TpBpy-COF@Bi2S3 composite photoelectrode.

[0046] Then, infrared spectroscopy curves were measured on the samples obtained in each step of the above embodiments. Figure 4 The infrared spectra of WO3, WO3-NH2, WO3-CHO, and WO3@TpBpy-COF samples are shown. All curves fall within the 3000-3600 cm⁻¹ range. -1 The broad absorption peaks are caused by the OH stretching mode of water molecules in the samples. Furthermore, all samples exhibited characteristic absorption peaks of WO3, with all spectra ranging from 420 to 1000 cm⁻¹ due to the different vibrational modes of the WO bonds. -1 The spectrum contains a broad absorption band within the range, which is correlated with the bending vibration of WO bonds and the stretching vibrations of WOW, WO, and W=O bonds, respectively, verifying the formation of tungsten oxide. Compared with pure WO3, the spectrum of the WO3-NH2 sample is larger at 1633 cm⁻¹. -1A new bond is displayed at the 1637 cm⁻¹, correlated with the NH vibration of the -NH₂ group, indicating successful surface amino modification of WO₃. Compared to WO₃-NH₂, the peak of the -NH₂ group disappears in the spectrum of WO₃-CHO, and the peak at 1637 cm⁻¹ is also observed. -1 and 1453cm -1 The two new peaks at 1574 cm⁻¹ originate from the aldehyde C=O and benzene ring C=C groups in Tp, respectively. -1 The new peak corresponds to C=N, proving that Tp has been successfully attached to the WO3 surface, and WO3-CHO has been successfully synthesized. Compared with WO3-CHO, the WO3@TpBpy-COF sample spectrum shows a higher peak at 1637 cm⁻¹. -1 The point corresponds to the disappearance of the C=O group of the aldehyde group in Tp, 1574 cm -1 The peak corresponding to C=N disappears at 1608 cm⁻¹, while at 1608 cm⁻¹... -1 A C=O peak corresponding to the ketone group appears at 1579 cm⁻¹. -1 The new peak at the point corresponds to the C=C bond, indicating that the WO3@TpBpy-COF sample was successfully synthesized in the embodiment, verifying the covalent connection between inorganic WO3 and organic materials.

[0047] Example 2

[0048] Preparation and application of WO3@TpBpy-COF@Bi2S3 energy storage type organic-inorganic hybrid composite semiconductor photoanode for photoelectrochemical cathodic protection against metal corrosion:

[0049] 1) Place a clean titanium sheet (1×2cm) 2 The substrate was etched in concentrated hydrochloric acid (12M) heated to 80℃ for 40 min, rinsed with deionized water and dried in an oven at 60℃ to obtain an etched Ti substrate for use as a substrate for photoanodine synthesis.

[0050] 2) Add 1.0 g WCl6 to 50 ml of anhydrous ethanol, stir to form a clear yellow solution, then transfer the solution to a 100 mL reactor containing an etched Ti substrate (the Ti substrate obtained in step 1 is placed at a 45° angle to the inner wall of the reactor). React at 160 °C for 24 hours. After the reactor cools, remove the Ti substrate with the WO3 film, rinse with deionized water, air-dry at 80 °C, and then calcine in air at 450 °C for 2 hours at a heating rate of 10 °C / min to obtain a photoanode with WO3 grown in situ on the Ti substrate.

[0051] 3) The WO3 photoelectrode obtained in step 2 was immersed in 50 mL of ethanol solution for 30 minutes. Then, 300 μL of 3-aminopropyltriethoxysilane was slowly added dropwise under vigorous stirring, and the mixture was stirred continuously at room temperature for 10 hours. The WO3 photoelectrode was then removed, washed alternately with ethanol and distilled water, and dried in air at 60 °C to obtain an amino-functionalized WO3-NH2 photoelectrode. The prepared WO3-NH2 photoelectrode was placed in 30 mL of 1,4-dioxane solution, and then 1.0 mg of 1,3,5-trialdehyde phloroglucinol and 0.5 mL of 3 mol / L ethanol solution were added, respectively. -1 Glacial acetic acid was added to the solution, stirred at room temperature for 2 hours, washed and dried to obtain the WO3-CHO photoelectrode.

[0052] 4) Add 15 mL of 1,3,5-trimethylbenzene to 15 mL of 1,4-dioxane and sonicate for 20 minutes. Then, add 7 mg of 1,3,5-trialdehyde phloroglucinol and 7 mg of 5,5'-diamino-2,2'-bipyridine to the mixture and sonicate for another 20 minutes. Afterward, pour the mixture into a 50 mL reactor containing a WO3-CHO photoelectrode (tilted, composite side down) and react at 120°C for 72 hours. After the reaction, remove the photoelectrode, wash it alternately with acetone and distilled water, and dry it to obtain the WO3@TpBpy-COF photoelectrode. Prepare an untreated WO3 / TpBpy-COF composite photoelectrode using the same method, replacing the WO3-CHO photoelectrode in this step with the WO3 photoelectrode obtained in step 2), denoted as the WO3 / TpBpy-COF photoelectrode.

[0053] 5) Immerse the WO3@TpBpy-COF photoelectrode in an ethylene glycol solution containing 0.2M Bi(NO3)3·5H2O, stir for 20 minutes, let stand for 24 hours, seal, and maintain at a constant temperature of 60℃ for 10 hours. After cooling, clean the photoelectrode with ethylene glycol and deionized water, and dry completely in air at 80℃. Then, apply the Bi complexed... 3+ The WO3@TpBpy-COF photoelectrode was immersed in a 0.23M Na2S·9H2O methanol solution for 3 hours, then washed with methanol and deionized water and completely dried at 80℃ to obtain the WO3@TpBpy-COF@Bi2S3 photoelectrode.

[0054] Furthermore, the conductive surface of the long conductive edge of the titanium sheet on which the WO3@TpBpy-COF@Bi2S3 composite photoelectric energy storage material is finally grown is scraped out, and insulating adhesive is applied at the junction of the composite photoelectric energy storage material and the conductive surface, so that the exposed test area is 10×10mm. 2 WO3@TpBpy-COF@Bi2S3 energy storage hybrid composite photoanode was prepared.

[0055] The hybrid semiconductor composite photoanode prepared as described above is prepared according to... Figure 5 The apparatus was connected as shown, and the photoinduced mixing potential of the photoanode and 316L SS electrode coupling system prepared in this invention under simulated sunlight irradiation was monitored using a CHI 660E electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. Figure 6 The changes in A and 6B, and the intensity of the photocurrent coupled between the two ( Figure 6 C), and simultaneously, the calculation of the charge released by the 316L SS electrode in the dark after 100 s of photoanode illumination (see...). Figure 6 D):

[0056] Specifically, the measuring device consists of two reaction chambers: a corrosion chamber and a photoelectrochemical chamber. The photoelectrochemical chamber contains 0.25 mol L... -1 Na2S and 0.35 mol L -1 The corrosion tank contained a Na2SO3 solution and a 3.5 wt% NaCl solution, with the two reaction tanks connected by a salt bridge. The photoanode was placed in the photoelectrochemical tank, and the protected metal electrode 316L SS was placed in the corrosion tank. The light source used in this study was a 300-W xenon lamp (PLS-SXE300, Beijing Bofei Lighting Co., Ltd., China). Simulated sunlight was obtained by adding an AM1.5 filter to the light source. The illumination intensity was 100 mW / cm². 2 These tests were conducted under intermittent simulated sunlight. A quartz window, approximately 30 mm in diameter, is located at the center of the front of the photovoltaic cell, through which incident light illuminates the photoanode surface.

[0057] Figure 6Figure A shows the OCP changes of the 316L stainless steel electrode coupled with the composite photoelectrode. It is clearly observed from the figure that when the light is turned on, the OCP of all coupled electrodes rapidly decreases to more negative values. This is due to the potential reduction caused by the transfer of photoelectrons excited by light from the semiconductor photoelectrode to the 316L stainless steel electrode. The photoelectric potentials corresponding to the WO3, WO3@TpBpy-COF, WO3 / TpBpy-COF, WO3@TpBpy-COF@Bi2S3, and WO3 / TpBpy-COF@Bi2S3 photoelectrodes stabilize at -490, -670, -669, -925, and -893 mV, respectively. Based on this result, the triphase covalently bonded WO3@TpBpy-COF@Bi2S3 photoelectrode exhibits enhanced photocathodic protection capability under simulated sunlight irradiation compared to single-phase WO3, biphase WO3@TpBpy-COF, and non-covalently bonded composite materials, and demonstrates the highest photocathodic protection performance for 316L stainless steel. After the light is turned off, the slow recovery of the OCP potential is attributed to the energy storage function of the WO3 component, with the continuous release of electrons in the dark state protecting the coupled metal. It is worth noting that, based on the above results, both WO3@TpBpy-COF and WO3 / TpBpy-COF are superior to pure WO3 photoelectrodes, indicating that the composite covalent organic framework TpBpy-COF is beneficial to improving the photoelectrochemical cathodic protection performance of the photoelectrode. When composited with the relatively negatively potential Bi2S3 material, the OCP decreases significantly, and WO3@TpBpy-COF@Bi2S3 outperforms WO3 / TpBpy-COF@Bi2S3, indicating that multiphase heterocomposite composites via covalent bonding help improve the performance of composite materials.

[0058] To further investigate the effect of the covalently bonded TpBpy-COF component on the photoelectrochemical cathodic protection performance of the composite photoelectrode, the OCP changes of WO3@TpBpy-COF@Bi2S3 and WO3 / TpBpy-COF@Bi2S3 photoelectrodes coupled with 316L stainless steel under long-term illumination were measured. The results are as follows: Figure 6As shown in Figure B, the composite photoelectrode exhibits a consistent trend in the initial application phase. After equilibrium is established, the OCP values ​​remain at -927 and -895 mV, respectively. However, with continued extended illumination time, the WO3 / TpBpy-COF@Bi2S3 coupling system shows unstable OCP changes. Conversely, the covalently bonded WO3@TpBpy-COF@Bi2S3 composite photoelectrode coupling system exhibits superior chemical stability under illumination, with a constant OCP value over a long period, demonstrating good continuous cathodic protection stability. After light is turned off, the WO3 / TpBpy-COF@Bi2S3 recovers its potential more rapidly, while the WO3@TpBpy-COF@Bi2S3 composite photoelectrode recovers its potential more slowly. These test results indicate that introducing the covalently bonded TpBpy-COF component into the composite photoelectrode not only improves photocathode protection performance but also enhances the application stability of the photoelectrode system.

[0059] Figure 6 Figure C shows the change in photoinduced current density between the prepared composite photoelectrode and the 316L stainless steel metal electrode coupling system. As shown in the figure, when the light is switched on, all photoelectrodes immediately show a positive photocurrent, indicating good photoelectric conversion of the photoelectrodes and photoelectrons flowing to the coupling metal. After stabilization, the current decreases slightly, which is due to photoelectron loss caused by the recombination of photogenerated carriers. After stabilization, the photoinduced current densities corresponding to the WO3, WO3@TpBpy-COF, WO3@TpBpy-COF@Bi2S3, and WO3 / TpBpy-COF@Bi2S3 photoelectrodes are 17.8, 24.1, 40.6, and 36.8 μA / cm, respectively. -2 WO3@TpBpy-COF@Bi2S3 produces the highest photocurrent under illumination, and... Figure 6 The OCP test results shown in Figure A are consistent, indicating that when the WO3@TpBpy-COF@Bi2S3 composite photoelectrode is coupled with 316L stainless steel, it provides 40.6 μAcm under illumination. -2 The current was used to polarize the cathode to -925mV. Simultaneously, it was observed that when the light source was cut off, the current in all photoelectrodes did not disappear rapidly, indicating that electrons continued to flow into the metal even after the light was turned off. The rate of current decrease, from fastest to slowest, was: WO3 > WO3@TpBpy-COF > WO3 / TpBpy-COF@Bi2S3 > WO3@TpBpy-COF@Bi2S3. This is related to the amount of electrons stored in the composite photoelectrode.

[0060] The energy storage performance of the photoelectrode is crucial for continuous cathodic protection in the dark state. Therefore, the discharge behavior of the WO3@TpBpy-COF@Bi2S3 composite photoelectrode was further analyzed, and the results are as follows: Figure 6As shown in Figure D, after 100 seconds of illumination, the light source was turned off, allowing it to continue discharging until the current reached zero. The discharge duration was 155 minutes. Integrating the portion of the curve after the light was turned off, it was found that the WO3@TpBpy-COF@Bi2S3 composite photoelectrode stored 8.32 × 10⁻⁶ cells / day under 100 seconds of illumination alone. -2 The presence of C electrons indicates that the photoelectrode has excellent electron storage performance, which is beneficial for continuous photoelectrochemical cathodic protection in the absence of light.

[0061] In summary, this invention successfully prepared an organic-inorganic hybrid energy storage type WO3@TpBpy-COF@Bi2S3 semiconductor composite photoanode, which can provide continuous photoelectrochemical cathodic protection for coupled metals for metal corrosion protection.

Claims

1. A method for preparing an energy storage type organic-inorganic hybrid semiconductor composite film, characterized by comprising: The inorganic WO3 thin film of nanoflower array is grown on a conductive Ti substrate, then the WO3 thin film is modified by surface amination and COF monomer aldehyde modification in sequence to obtain a functionalized WO3 surface, then a thin layer of covalent organic framework TpBpy-COF material is in-situ grown on the functionalized WO3 surface by covalent bonding, and finally the N atoms distributed in the bipyridine unit of the covalent organic framework TpBpy-COF thin layer are used to coordinate and complex Bi 3+ , and then S 2- is adsorbed again, so as to realize the anchoring of the inorganic semiconductor Bi2S3 material in the COF, and obtain a hetero-organic-inorganic hybrid semiconductor composite film WO3@TpBpy-COF@Bi2S 3； ​ Specifically: 1) Preparation of nanoflower array WO3 film: WCl6 is added to anhydrous ethanol to form a clear yellow solution, and an etched Ti substrate is used as the substrate for film growth. Then, the clear yellow solution is transferred to a Teflon-lined autoclave containing the etched Ti substrate, and reacted at 140-180°C for 22-26 hours. After the reaction, the Ti substrate is taken out, washed, dried, and calcined to grow a nanoflower array WO3 film on the Ti substrate; 2) Surface functionalization of WO3 film: First, the Ti substrate with a nanoflower array WO3 film grown in step 1 is immersed in an ethanol solution for 20-30 minutes. Then, 100-300 μL of 3-aminopropyltriethoxysilane is added dropwise under stirring, and the stirring is continued at room temperature for 10-12 hours. Subsequently, the Ti substrate is taken out and washed and dried to grow an amino-functionalized WO3-NH2 film on the surface of the Ti substrate. Then, the Ti substrate is placed in a 1,4-dioxane solution, and 0.3-0.5 mM of 1,3,5-triformylphloroglucinol and 1-1.5 mM of glacial acetic acid are added to the system. After stirring at room temperature for 2-4 hours, the Ti substrate is washed and dried to grow a Tp monomer aldehyde-functionalized WO3-CHO film on the Ti substrate; 3) Preparation of covalently bonded WO3@TpBpy-COF: 1,3,5-trimethylbenzene is added to 1,4-dioxane in a 1:1 mass ratio and mixed uniformly. Then, 0.7-1.0 mM of 1,3,5-triformylphloroglucinol and 1.5-2.0 mM of 5,5'-diamino-2,2'-bipyridine are added to obtain a mixed solution. The mixed solution is poured into a reaction kettle containing the Tp monomer aldehyde-functionalized WO3-CHO film synthesized in step 2) to immerse the Ti substrate. The reaction is carried out at 100-120°C for 60-72 hours. After the reaction, the Ti substrate is taken out, washed, and dried to obtain a covalently bonded WO3@TpBpy-COF composite film grown on the Ti substrate; 4) Synthesis of WO3@TpBpy-COF@Bi2S3: The Ti substrate with WO3@TpBpy-COF grown in step 3) is immersed in an ethylene glycol solution containing 0.1-0.3 M Bi(NO3)3·5H2O, stirred, and placed for 20-24 hours. After sealing, it is kept at a constant temperature of 60-80°C for 10-12 hours. After cooling, it is washed and dried. After drying treatment, the Ti substrate is immersed in a methanol solution containing 0.2-0.4 M Na2S·9H2O for 2-3 hours, then washed and dried to form a heterogeneous organic-inorganic hybrid semiconductor composite film WO3@TpBpy-COF@Bi2S3 on the surface of the Ti substrate.

2. The method of claim 1, wherein the method is characterized by: The etched Ti substrate is a clean titanium sheet etched in 12M concentrated hydrochloric acid heated to 80-95°C for 40-60 minutes, washed with deionized water, and dried in an oven at 60-80°C. Then, it is placed in the reaction kettle with the Ti substrate at a 45° angle to the kettle wall, with the growth surface facing down.

3. The method of claim 1, wherein the method is characterized by: After the reaction in the step 1), the Ti substrate on which the WO3 film has been grown is rinsed with anhydrous ethanol and deionized water and dried in air at 60-80°C, and then the Ti substrate is calcined in air at 440-450°C at a heating rate of 5°C min −1 for 1.7-2.2 hours to obtain a nanoflower array WO3 film grown on the Ti substrate.

4. The method of claim 1, wherein the method is characterized by: The step 2) takes out the Ti substrate of the surface growth nanoflower array WO3 film, alternately washes it with ethanol and distilled water, and places it in 60-80℃ air for drying.

5. The method of claim 1, wherein the method is characterized by: The step 3) after the reaction, alternately washes the Ti substrate with acetone and distilled water, and places it in 60℃ air for drying after washing.

6. The method of claim 1, wherein the method is characterized by: The step 4) keeps it at a constant temperature of 60-80℃ for 10-12 hours, washes the Ti substrate with ethylene glycol and deionized water after cooling, and completely dries it in 60-80℃ air; after the drying treatment, the Ti substrate is immersed in a methanol solution containing 0.2-0.4 M Na2S·9H2O for 2-3 hours, and then washed with methanol and deionized water and completely dried at 60-80℃.

7. The energy storage type organic-inorganic hybrid semiconductor composite film prepared by the method of claim 1, characterized by: The obtained hetero-organic-inorganic hybrid semiconductor composite film WO3@TpBpy-COF@Bi2S3 with a nanoflower array three-layer core-shell structure is prepared by the method according to claim 1.

8. The use of the light anode of the energy storage type organic-inorganic hybrid semiconductor composite film prepared by the preparation method of claim 1, characterized in that: The composite film is used for preparing an energy storage type organic-inorganic hybrid composite semiconductor photoanode, and the application of the photoanode in long-acting photoelectrocathodic protection corrosion prevention.

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