Piezoelectric photocatalytic composite membrane driven by low flow rate and preparation method and application thereof

Abstract

The application provides a low-flow-rate-driven piezoelectric photocatalytic composite film and a preparation method and application thereof, and belongs to the technical field of dielectric materials. The preparation method provided by the application comprises the following steps: uniformly mixing g-C3N4 and MoO3 with a solvent to obtain a mixture; sequentially performing drying, grinding and sintering on the mixture to obtain a g-C3N4 / MoO3 composite material; dispersing the g-C3N4 / MoO3 composite material and PVDF-TrFE in an organic solvent, then coating the obtained dispersion on a base material, and then performing drying to obtain the low-flow-rate-driven piezoelectric photocatalytic composite film. The preparation method provided by the application is simple, can promote the formation of high-quality beta-phase PVDF-TrFE, and the obtained piezoelectric photocatalytic composite film has high photocatalytic HER efficiency.

Description

Technical Field

[0001] This invention relates to the field of dielectric materials technology, and in particular to a low-flow-rate driven piezoelectric photocatalytic composite film, its preparation method, and its application. Background Technology

[0002] The increasing depletion of non-renewable energy resources is exacerbating the global energy crisis. The pioneering work of Fujishima and Honda revealed the potential of TiO2 photocatalytic hydrogen production, providing a new approach to sustainable energy generation. This discovery also reveals the potential of semiconductors in photocatalytic water splitting, offering a promising strategy for alleviating energy shortages. Recently, heterojunctions composed of graphitized carbonitrides (g-C3N4) have been used as highly efficient photocatalysts for hydrogen production, but their performance is hampered by poor visible light absorption and high carrier recombination rates. While methods to improve the photocatalytic activity of heterojunctions through surface morphology modulation and defect engineering have shown promise, they are limited by factors such as electric field and limited tuning capabilities. In this context, the internal polarization electric field of piezoelectric materials has attracted attention in recent years. Many studies have focused on elucidating the impact of this built-in field on carrier dynamics and lifetime, and its potential to enhance photocatalytic processes.

[0003] PVDF-TrFE is renowned for its superior mechanical toughness, chemical stability, and significant piezoelectric constant, making it an excellent substrate for photocatalysts. The β-phase of PVDF-TrFE, due to its superior electroactivity compared to the α-phase, is crucial for enhancing piezoelectricity. Therefore, researchers have proposed various techniques for manufacturing PVDF-TrFE, including electrospinning, mechanical stretching, mechanical pressure, and polarization in strong electric fields, to promote the formation of high-quality β-phase PVDF-TrFE. However, these manufacturing processes are highly complex and typically costly, making them difficult to apply to practical industrial production. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a low-flow-rate driven piezoelectric photocatalytic composite film, its preparation method and application. The preparation method provided by this invention is simple and can promote the formation of high-quality β-phase PVDF-TrFE. The resulting piezoelectric photocatalytic composite film has high photocatalytic HER efficiency.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of this invention is a method for preparing a low-flow-rate driven piezoelectric photocatalytic composite film, comprising the following steps:

[0007] Step 1. Mix g-C3N4 and MoO3 with solvent until homogeneous to obtain a mixture;

[0008] Step 2. The mixture is dried, ground, and sintered sequentially to obtain the g-C3N4 / MoO3 composite material;

[0009] Step 3. Disperse the g-C3N4 / MoO3 composite material and PVDF-TrFE in an organic solvent, then coat the resulting dispersion onto the matrix material, and then dry it to obtain the low-flow-rate driven piezoelectric photocatalytic composite film.

[0010] The second technical solution of the present invention is a low-flow-rate driven piezoelectric photocatalytic composite film prepared by the above preparation method.

[0011] The third technical solution of the present invention is the application of the above-mentioned low-flow-rate driven piezoelectric photocatalytic composite membrane in photocatalytic hydrogen production.

[0012] The present invention discloses the following technical effects:

[0013] The preparation method provided by this invention is simple, low-cost, and easy to industrialize.

[0014] The low-flow-rate driven piezoelectric photocatalytic composite membrane provided by this invention exhibits enhanced piezoelectric properties and can be used in photocatalytic hydrogen production reactions (HER). This invention achieves a higher content of piezoelectric β-phase in the PVDF-TrFE composite membrane by adding g-C3N4 / MoO3, which induces CH2 bond deflection. Under low-flow-rate water driving, the hydrogen production rate of the piezoelectric photocatalytic composite membrane of this invention is increased by 1.87 times. Pressure-current tests also show that, under the same pressure conditions, this piezoelectric photocatalytic composite membrane has a higher current response than PVDF-TrFE. This invention provides a new approach for preparing high-performance piezoelectric materials. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The images show the structure and microstructure of MoCNP-50 and PVDF-TrFE in the effect verification example. (a) is the SEM of PVDF-TrFE, (b) is the SEM of MoCNP-50, (c) is the EDS spectrum of MoCNP-50, (d) is the distribution of C in MoCNP-50, (e) is the distribution of F in MoCNP-50, (f) is the distribution of Mo in MoCNP-50, (g) is the distribution of N in MoCNP-50, and (h) is the distribution of O in MoCNP-50.

[0017] Figure 2 The powder XRD patterns of MoCN-50, PVDF-TrFE, and MoCNP-50 in the efficacy verification example are shown.

[0018] Figure 3 The following are FT-IR spectra of MoCNP-50 in the effect verification example, where (a) is the transmission spectrum of MoCNP-50 and PVDF-TrFE, and (b) is the absorption spectrum and β phase content of MoCNP-50 and PVDF-TrFE.

[0019] Figure 4 The XPS images of MoCNP-50 in the effect verification example are shown, where (a) is the C1s spectrum of MoCNP-50 and (b) is the Mo 3d spectrum of MoCNP-50.

[0020] Figure 5 The diagram shows the structure of MoCNP-50 and PVDF-TrFE.

[0021] Figure 6 The graph shows a comparison of the photocatalytic hydrogen production performance of different materials in the effect verification example. (a) shows the change of hydrogen production by different materials over time, and (b) shows the hydrogen production rate of different materials.

[0022] Figure 7 The PFM analysis results of MoCNP-50 and PVDF-TrFE in the efficacy verification example are shown. (a) is the piezoelectric hysteresis curve of the PVDF-TrFE sample, (b) is the butterfly curve of the PVDF-TrFE sample, (c) is the piezoelectric hysteresis curve of the MoCNP-50 sample, and (d) is the butterfly curve of the MoCNP-50 sample.

[0023] Figure 8 To verify the effect, the piezocurrent of the same MoCNP membrane at different flow rates and the piezocurrent of different MoCNP membranes at the same flow rate are shown in the example. (a) represents the piezocurrent of the same MoCNP membrane under different flow rates, (b) represents the piezocurrent of different MoCNP membranes at the same flow rate, and (c) represents the piezocurrent of PVDF-TrF and MoCNPE. 33 value. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] Compared to the complex and costly manufacturing processes of existing piezoelectric membrane preparation methods (including electrospinning, mechanical stretching, mechanical pressure, and polarization in a strong electric field), the self-polarization of PVDF-TrFE membranes provides a simple and environmentally friendly alternative. By incorporating fillers into PVDF-TrFE, self-polarization is induced, thereby increasing the content of the β phase in the membrane.

[0030] Specifically, this invention provides a method for preparing a low-flow-rate driven piezoelectric photocatalytic composite film, comprising the following steps:

[0031] Step 1. Mix g-C3N4 and MoO3 with ethanol until homogeneous to obtain a mixture;

[0032] Step 2. The mixture is dried, ground, and sintered sequentially to obtain the g-C3N4 / MoO3 composite material (denoted as MoCN);

[0033] Step 3. Disperse the g-C3N4 / MoO3 composite material and PVDF-TrFE in an organic solvent, then coat the resulting dispersion onto the matrix material, and then dry it to obtain the low-flow-rate driven piezoelectric photocatalytic composite film (denoted as MoCNP).

[0034] In a preferred embodiment of the present invention, the preparation method of the g-C3N4 is as follows: melamine is pyrolyzed at 620-660℃ (more preferably, 650℃) for 2 hours to obtain the g-C3N4; the heating rate during pyrolysis is 5-6℃ / min (more preferably, 5℃ / min).

[0035] In a preferred embodiment of the present invention, the method for preparing MoO3 is as follows: (NH4)2MoO4 and citric acid are dissolved in 2-mercaptoethanol (2-ME), and then the resulting solution is reacted at 480-520°C for 10-12 h (more preferably, at 500°C for 12 h). After the reaction is completed, the solution is naturally cooled to room temperature, and the product is collected as MoO3.

[0036] In a preferred embodiment of the present invention, in step 1, the mass-to-volume ratio of g-C3N4 and MoO3 to the solvent is 0.05–0.50 g: 0.50–0.95 g: 50–70 mL (more preferably, 0.40–0.50 g: 0.50–0.602 g: 50–70 mL); the solvent is ethanol. The present invention does not have special requirements regarding the method of uniform mixing; any technique commonly used by those skilled in the art can be selected, such as ultrasonic treatment, where the power of the ultrasonic treatment is 35–40 kHz and the time is 2.5–3 hours.

[0037] In a preferred embodiment of the present invention, in step 2, the drying temperature is 60-80℃ (more preferably, 60℃) and the time is 12-14h (more preferably, 12h); the sintering temperature is 280-300℃ (more preferably, 300℃) and the time is 3.5-4h (more preferably, 4h).

[0038] In this invention, if the sintering temperature is too high, it will cause g-C3N4 to decompose; if the sintering temperature is too low, it will result in poor bonding between g-C3N4 and MoO3. Both excessively high and low sintering temperatures negatively impact the performance of the resulting MoCNP.

[0039] In a preferred embodiment of the present invention, in step 3, the organic solvent is dimethyl sulfoxide (DMSO); the mass-to-volume ratio of the g-C3N4 / MoO3 composite material and PVDF-TrFE to the organic solvent is 45-55 mg: 240-260 mg: 2 mL (more preferably, 50 mg: 250 mg: 2 mL); the coating method is spin coating, and the spin coating speed is 500 rpm; the drying parameters are set as follows: drying at 15-25°C for 3-4 hours. The present invention does not have special requirements for the method of dispersing the g-C3N4 / MoO3 composite material and PVDF-TrFE in the organic solvent; any technique commonly used by those skilled in the art can be used, such as stirring, with a stirring time of 12 hours to ensure uniform dispersion. The present invention does not impose special limitations on the selection of the matrix material; any matrix material commonly used by those skilled in the art can be used, such as a glass slide.

[0040] This invention promotes the self-polarization process through drying. If the temperature is higher than the parameter range in this invention, it will affect the self-polarization process and reduce the formation ratio of the piezoelectric β phase in PVDF itself.

[0041] The principle of this invention is as follows: This invention incorporates synthesized g-C3N4 / MoO3 heterojunctions (MoCN) into PVDF-TrFE, followed by drying to promote a self-polarization process. This self-polarization phenomenon mainly originates from the strong electrostatic interaction between the positively charged -CH2 groups on the PVDF-TrFE polymer chain and the negatively charged MoO3. The resulting g-C3N4 / MoO3PVDF-TrFE membrane (i.e., the low-flow-rate driven piezoelectric photocatalytic composite membrane, MoCNP) exhibits excellent hydrogen production capabilities. This invention elucidates the mechanism by which adding fillers increases the β-phase content in PVDF-TrFE, and promotes the development of low-cost, high-performance PVDF-TrFE membrane material manufacturing technology through a simple method.

[0042] The present invention also provides a low-flow-rate driven piezoelectric photocatalytic composite membrane prepared by the preparation method described above.

[0043] The present invention also provides an application of the low-flow-rate driven piezoelectric photocatalytic composite membrane described above in photocatalytic hydrogen production.

[0044] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0045] Unless otherwise specified, all raw materials and reagents used in the examples can be obtained through commercial channels.

[0046] Example 1

[0047] Step 1. Preparation of g-C3N4: Melamine is placed in an alumina crucible and then heated to 650°C in a muffle furnace at a heating rate of 5°C / min and held for 2 hours.

[0048] Step 2. Preparation of MoO3: First, add 1g of (NH4)2MoO4 and 3g of citric acid to 10ml of 2-ME and stir the mixture thoroughly for 4 hours to ensure homogeneity. Then, allow the solution to stand for 48 hours to achieve complete dissolution. Next, place the solution in a muffle furnace and heat to 500℃ at a heating rate of 5℃ / min, holding for 12 hours. After the heating process, allow the sample to cool naturally to room temperature.

[0049] Step 3. Preparation of MoCN: First, 0.50 g of g-C3N4 prepared in Step 1 and 0.50 g of MoO3 prepared in Step 2 were added to 50 mL of ethanol and sonicated for 3 hours. Then, the mixture was dried at 60 °C for 12 hours. Finally, the powders were mixed and thoroughly ground for 0.5 hours, and then sintered at 300 °C for 4 hours. After cooling, the product was obtained and named MoCN. According to the synthetic route, g-C3N4 / MoO3 composites with different MoO3 weight percentages of 5 wt% (prepared from 0.05 g g-C3N4 and 0.95 g MoO3) and 50 wt% (prepared from 0.50 g g-C3N4 and 0.50 g MoO3) were synthesized. The obtained MoCN composites were named MoCN-5 and MoCN-50, respectively.

[0050] Step 4. Preparation of MoCNP: 50 mg of MoCN was added to 2 ml of DMSO and sonicated for 30 minutes. Then, 250 mg of PVDF-TrFE powder was added and stirred for 12 hours to ensure dispersion. The mixture was then spin-coated onto a 2.5 cm × 2.5 cm glass slide at 500 rpm. Finally, the coated product was dried at room temperature (15–25 °C) for 4 hours to obtain a g-C3N4 / MoO3 / PVDF-TrFE membrane, denoted as MoCNP. Depending on the type of MoCN used, the resulting membranes were named MoCNP-5 and MoCNP-50, respectively.

[0051] Effect verification example

[0052] The structure and microstructure of MoCNP-50 and PVDF-TrFE were observed by SEM, such as... Figure 1 As shown, the pore distribution within MoCNP-50 is relatively uniform, and the pore size is small. Meanwhile, as... Figure 1As shown in (cf), EDS analysis revealed the distribution of various elements of g-C3N4 and MoO3 in MoCNP, confirming the successful synthesis of g-C3N4 / MoO3 / PVDF-TrFE composite material with g-C3N4 and MoO3.

[0053] Powder XRD patterns of MoCN-50, PVDF-TrFE, and MoCNP-50 are shown below. Figure 2 As shown, the XRD pattern confirmed the formation of the photocatalyst. The XRD peaks of the g-C3N4 sample matched well with those of g-C3N4 (JCPDS 871526), ​​with two well-defined peaks at 27.6° and 13.8°, corresponding to the (002) and (100) diffraction planes. Comparing PVDF-TrFE and MoCN-50, it was found that after introducing MoCN-50 into PVDF-TrFE, the 20.1° peak corresponding to the β phase of PVDF-TrFE became sharper, while the peak corresponding to the α phase was weaker than that of PVDF-TrFE. This indicates that part of the α phase of PVDF-TrFE was transformed into the β phase.

[0054] To elucidate the mechanism of β-phase enhancement, FT-IR tests were performed on MoCNP-50 (in the figure, MoCNP represents MoCNP-50). Figure 3 In (a), 2800-3600cm -1 The absorption band in this region corresponds to the NH group of the unreacted amine, 1240-1650 cm⁻¹ -1 The absorption bands in this region represent CN and C=N bonds, 950 cm⁻¹ -1 and 1014cm -1 The peak at that location belongs to MoO3. All of this indicates that MoCN-50 was successfully loaded onto PVDF-TrFE. Figure 3 Figure (b) shows the α phase at 760 cm⁻¹ -1 The peak disappeared, and the α phase was at 810 cm⁻¹. -1 The peak weakened with the addition of MoCN-50. Meanwhile, the β phase content increased from 55.1% to 81.8%, demonstrating the effect of MoCN-50 addition on the phase composition of PVDF-TrFE.

[0055] The composition of the MoCNP-50 composite material was further characterized using XPS. Figure 4As shown in (a) (where MOCNP represents MoCNP-50), the C1s spectrum of MoCNP-50 can be decomposed into four peaks at 284.8 eV (CC bond), 286.3 eV (CH2 bond), 288.7 eV (CF bond), and 290.9 eV (CF2 bond). Meanwhile, the Mo 3d spectrum (Figure (b)) clearly shows peaks at 231.4 eV and 234.5 eV, attributable to Mo. 5+ And the peaks at 232.8 eV and 235.8 eV, corresponding to Mo 6+ Simultaneously, spectroscopic examination revealed the shift of the CH2 bond to lower binding energies, while the CF and CF2 bonds, as well as the Mo bond, shifted to higher binding energies. This phenomenon indicates a directional charge transfer between MoO3 and the CH2 bond, suggesting a strong electrostatic interaction. Due to this electrostatic interaction, the CH2 bond undergoes rotation, as... Figure 5 As shown, this leads to an increase in the β phase content in PVDF-TrFE.

[0056] like Figure 6 As shown in (a) and (b), under the same conditions, the MoCNP-50 piezoelectric film exhibits a strength of 552.4 μmol h⁻¹. -1 The HER rate was significantly higher than that of the MoCN-50 powder catalyst, which was 302.16 μmol h⁻¹. -1 The performance of the MoCNP-50 membrane under static, unstirred conditions was further investigated. With all other parameters held constant, the HER rate decreased significantly to 231.63 μmol h⁻¹. -1 The significant decrease in the HER rate provides strong evidence for the piezoelectric field generated by water flow in MoCNP. The mechanical stress of the water flow is converted into electrical energy through the piezoelectric effect, generating a potential difference that promotes the effective separation of photogenerated electron-hole pairs, thereby improving the efficiency of photocatalytic HER.

[0057] Furthermore, we tested the hydrogen production capacity of the MoCNP-5 piezoelectric membrane and its corresponding powdered catalyst (MoCN-5). The study found that although the MoCNP-5 piezoelectric membrane and powdered catalyst exhibited relatively high hydrogen production capacity under static conditions, their hydrogen production rates and enhancement ratios were significantly lower than those of the MoCNP-50 piezoelectric membrane under the same water flow drive. This indicates that a higher MoO3 concentration is beneficial for the piezoelectric membrane to achieve a higher hydrogen production rate under water flow drive. That is, MoO3 can enhance the β-phase content of PVDF-TrFE.

[0058] PFM was used to characterize the piezoelectric properties of the MoCNP-50 and PVDF-TrFE samples, and the results are as follows: Figure 7As shown. PFM analysis produced characteristic butterfly curves, indicating the piezoelectric response of the material. These characteristics are consistent with the phenomenon of charge generation when mechanical stress is applied, which is characteristic of piezoelectric materials. Comparative analysis of PFM data shows that MoCNP-50 ( Figure 7 (c) and (d)) with PVDF-TrFE ( Figure 7 Compared to (a) and (b)), the MoCNP-50 exhibits a more pronounced piezoelectric response. The piezoelectric response amplitude of MoCNP-50 is significantly higher, as can be seen from the larger butterfly curve. This enhanced piezoelectric signal clearly demonstrates the improved ability of MoCNP to convert mechanical stimulation into electrical energy, illustrating its superior piezoelectric performance compared to PVDF-TrFE. This enhanced piezoelectric response is due to its higher β-phase content.

[0059] Furthermore, we measured the piezocurrent on the same photocatalytic membrane at different flow rates, and measured the piezocurrent on different photocatalytic membranes at the same flow rate. Figure 8 Our findings reveal that the prepared MoCNP photocatalytic membrane is highly sensitive to flow rate; the piezocurrent increases positively with increasing flow rate. Furthermore, a comparison of the piezocurrent magnitudes of MoCNP and PVDF-TrFE membranes at the same flow rate indicates that the reaction of the PVDF-TrFE photocatalytic membrane is less pronounced. Simultaneously, we tested the Di of both membranes. 33 The coefficient directly proves that MoCNP has a better piezoelectric response than PVDF-TrFE. Piezoelectric stress test results confirm that the piezoelectric-sensitive β phase in PVDF-TrFE is the key factor affecting piezoelectric performance, which determines that the PVDF-TrFE film enhanced with MoCN has higher HER activity.

[0060] The above results demonstrate that high photocatalytic HER efficiency was achieved by introducing MoCN into PVDF-TrFE. The study found that the strongly electronegative MoO3 has a profound impact on the structure of the PVDF-TrFE chain. Through electrostatic interactions, it induces CH2 bond rotation, thereby increasing the proportion of the β phase in the PVDF-TrFE chain. Therefore, MoCNP exhibits significantly better photocatalytic HER efficiency under pressure than unpressurized MoCNP. Subsequent studies using PFM and pressure-current measurements revealed that under the influence of low-velocity water flow, MoCNP generates a stronger built-in electric field, more effectively promoting charge carrier separation. This invention provides a new approach for the simple fabrication of materials with superior piezoelectric properties, and has significant implications for the development of advanced energy conversion technologies.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a low-flow-rate driven piezoelectric photocatalytic composite membrane in photocatalytic hydrogen production, characterized in that, The method for preparing the low-flow-rate driven piezoelectric photocatalytic composite film includes the following steps: Step 1. Mix g-C3N4 and MoO3 with solvent until homogeneous to obtain a mixture; Step 2. The mixture is dried, ground, and sintered sequentially to obtain the g-C3N4 / MoO3 composite material; Step 3. Disperse the g-C3N4 / MoO3 composite material and PVDF-TrFE in an organic solvent, then coat the resulting dispersion onto the matrix material, and then dry it to obtain the low-flow-rate driven piezoelectric photocatalytic composite film; The mass-to-volume ratio of g-C3N4 and MoO3 to the solvent is 0.40–0.50 g: 0.50–0.602 g: 50–70 mL; The mass-to-volume ratio of the g-C3N4 / MoO3 composite material and PVDF-TrFE to the organic solvent is 45-55 mg: 240-260 mg: 2 mL.

2. The application of the low-flow-rate driven piezoelectric photocatalytic composite membrane according to claim 1 in photocatalytic hydrogen production, characterized in that, The preparation method of g-C3N4 is as follows: melamine is pyrolyzed at 620-660℃ for 2 hours to obtain g-C3N4; the heating rate during pyrolysis is 5-6℃ / min.

3. The application of the low-flow-rate driven piezoelectric photocatalytic composite membrane according to claim 1 in photocatalytic hydrogen production, characterized in that, The method for preparing MoO3 is as follows: (NH4)2MoO4 and citric acid are dissolved in 2-mercaptoethanol, and then the resulting solution is reacted at 480-520℃ for 10-12 hours. After the reaction is completed, the solution is naturally cooled to room temperature, and the product is collected as MoO3.

4. The application of the low-flow-rate driven piezoelectric photocatalytic composite membrane according to claim 1 in photocatalytic hydrogen production, characterized in that, In step 1, the solvent is ethanol.

5. The application of the low-flow-rate driven piezoelectric photocatalytic composite membrane according to claim 1 in photocatalytic hydrogen production, characterized in that, In step 2, the drying temperature is 60-80℃ and the time is 12-14h; the sintering temperature is 280-300℃ and the time is 3.5-4h.

6. The application of the low-flow-rate driven piezoelectric photocatalytic composite membrane according to claim 1 in photocatalytic hydrogen production, characterized in that, In step 3, the organic solvent is dimethyl sulfoxide; the drying parameters are set as follows: drying at 15-25°C for 3-4 hours.

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