Photo-driven self-powered fenton system, preparation method and application thereof

Abstract

The application belongs to the technical field of water treatment, and particularly relates to a light-driven self-powered Fenton system, a preparation method and application thereof. The light-driven self-powered Fenton system is a self-powered double-electrode system based on a photoanode Bi2MoO6 / g-C3N4 and a photocathode CuS. The system uses the work function difference between the photoanode and the photocathode as a self-powered driving force to realize the occurrence of a light-assisted self-powered Fenton reaction. The light-driven self-powered Fenton system effectively solves the technical defects of the conventional Fenton system, such as narrow applicable pH, easy precipitation, low H2O2 utilization rate, the electric Fenton system relying on external electricity and having high cost, the conventional light Fenton system needing to add H2O2 and easily causing secondary pollution, and the existing light self-Fenton system having poor light absorption, serious carrier recombination, poor electrode level matching, weak self-powered driving force and being unable to simultaneously realize high-sensitivity detection and efficient degradation.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically to a light-driven self-powered Fenton system, its preparation method, and its application. Background Technology

[0002] Water pollution has become an increasingly serious problem globally, especially organic pollutants, whose widespread presence and stability in the environment make them one of the major threats to water pollution. Hydroquinone (HQ), widely used in the chemical industry, is a common organic pollutant that can easily cause skin diseases, cardiovascular diseases, liver damage, and DNA damage. Its long-term presence in water bodies can cause serious harm to ecosystems and human health. Therefore, the effective removal and monitoring of HQ in water bodies is of great significance. Recent studies have focused on the simultaneous detection and degradation of hydrogen hydrate (HQ). Existing methods combine colorimetry and the Fenton reaction for pollutant detection and removal. For example, Li Jinkai et al. synthesized Fe / Mn-NC nanozymes and Fe3O4@PAA nanoparticles for colorimetric detection and degradation of HQ, with detection limits of 0.21 μM and 0.0923 μM, respectively. Yang Ping et al. constructed a multifunctional HRP integrated MIL-100 (Fe)@TiO2@Fe3O4-Janus micromotor to detect and remove HQ from water, with a detection limit of 1.84 μM. However, these methods have limitations in practical applications. Due to their reliance on added hydrogen peroxide (H2O2), the effectiveness of the Fenton reaction is easily affected by pH, leading to unstable treatment efficiency. Furthermore, colorimetry, which relies on color changes to determine pollutant concentration, has a large error margin and a limited detection range. Therefore, rapid monitoring and removal in real-world environments remains a challenge, requiring further optimization and exploration of more sensitive technologies.

[0003] Photoelectrochemistry (PEC) detection technology has become a research hotspot in the field of pollutant detection due to its advantages such as high sensitivity, low cost, and ease of operation. Self-powered PEC detection has made significant progress in recent years. By utilizing the Fermi level difference between the photoanode and photocathode to drive the rapid transfer of photogenerated electrons, energy self-sufficiency is achieved. This strategy not only inherits the advantages of fast response and low background signal of PEC sensing technology, but also shows great application potential due to its ease of integration into portable devices. However, the low carrier transport efficiency of the photoelectrode material and the limited detection signal constitute the main bottlenecks restricting the improvement of self-powered sensing performance. To solve these problems, a feasible method is to introduce electron acceptors to improve the sensor's sensitivity. For example, electron acceptors such as H2O2 can generate free radicals after activation, which can enhance the detection signal intensity by directly participating in the redox reaction of the target analyte. Although this method can effectively improve detection sensitivity, the additional introduction of electron acceptors increases the complexity and cost of the system.

[0004] The Fenton reaction, as an important component of advanced oxidation processes (AOPs), is based on ferrous ions (Fe2+). 2 The mechanism of catalytic H2O2 decomposition to produce ·OH has shown significant advantages in the mineralization of organic pollutants. However, the traditional Fenton system is prone to hydroxide precipitation, is limited by acidic environments, and has low H2O2 utilization efficiency, which severely restricts its application. To overcome these limitations, researchers have successively developed improved processes such as electro-Fenton (EF) and photo-Fenton. Among them, although the EF technology introduces O2 to generate H2O2 in situ, its high dependence on energy supply significantly increases operating costs. The photo-Fenton system, on the other hand, introduces light radiation to trigger Fe... 3 The photoreduction reaction of Fe2+ effectively promotes Fe2+. 3 ⁺-Fe 2⁺Cycling, simultaneously improving ·OH yield. It is worth noting that the recently developed photo-self-generated Fenton system successfully achieved in-situ H₂O₂ generation through water oxidation reaction (WOR) and oxygen reduction reaction (ORR). This breakthrough significantly reduces the transportation and storage costs of reagents. Based on this, a photo-assisted self-powered Fenton system developed using photo-self-generated Fenton technology exhibits an innovative strategy. This system can absorb sunlight to excite electron-hole pairs, triggering an electron transfer process, promoting in-situ H₂O₂ generation and metal ion cycling, thereby increasing the ·OH yield and promoting the detection and degradation of pollutants. Therefore, the selection of photoanode and photocathode materials is crucial in this system.

[0005] While photo-self-Fenton systems developed in recent years can generate hydrogen peroxide in situ, existing photoanodes generally suffer from weak light absorption, severe carrier recombination, and poor conductivity, resulting in low hydrogen peroxide yield and insufficient Fenton-like activity. Simultaneously, poor energy level matching between the photocathode and photoanode, insufficient self-powered driving force, and low electron transfer efficiency make it difficult to achieve efficient carrier separation and high hydroxyl radical yield. Furthermore, existing technologies cannot simultaneously achieve highly sensitive detection and efficient degradation of pollutants within the same system, exhibiting low integration and insufficient stability, failing to meet the demands for rapid monitoring and deep degradation in practical water treatment. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a light-driven self-powered Fenton system, its preparation method, and its applications. The light-driven self-powered Fenton system of this invention is a self-powered dual-electrode system based on a photoanode of Bi2MoO6 / g-C3N4 and a photocathode of CuS. This system effectively solves the technical defects of existing light-driven self-powered Fenton systems, such as poor light absorption, severe carrier recombination, poor electrode energy level matching, weak self-powered driving force, and the inability to simultaneously achieve high-sensitivity detection and efficient degradation.

[0007] Based on the above technical objectives, the present invention adopts the following technical solution: This invention protects a light-driven self-powered Fenton system, which is a self-powered dual-electrode system based on a photoanode Bi2MoO6 / g-C3N4 and a photocathode CuS. This system uses the difference in work function between the photoanode and the photocathode as the driving force for self-powering, thereby realizing the occurrence of light-assisted self-powered Fenton reactions.

[0008] This invention also protects a method for preparing a light-driven, self-powered Fenton system, comprising the following steps: Bi2MoO6 / g-C3N4 and CuS were prepared separately. Bi2MoO6 / g-C3N4 was loaded onto a carbon cloth substrate to prepare a photoelectric anode Bi2MoO6 / g-C3N4; CuS was loaded onto a carbon cloth substrate to prepare a CuS photocathode. The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were placed in parallel in the photoelectrochemical reaction cell, with the distance between the two electrodes controlled at 1cm~5cm. Phosphate buffer solution was used as the electrolyte to form a two-electrode system. Under room temperature and light conditions, a light-driven Fenton-like reaction can be carried out without the need to introduce oxygen into the electrolyte, driven by a self-powered system.

[0009] Preferably, in the photoanode Bi2MoO6 / g-C3N4, the mass ratio of Bi2MoO6 to g-C3N4 is 1:2~3. If this mass ratio is lower than 1:2, the relative amount of g-C3N4 is too small, and it cannot fully form a tight type II heterojunction interface with Bi2MoO6. This results in insufficient interfacial contact area, poorer photogenerated carrier separation, and accelerated electron-hole recombination rate. Simultaneously, it is difficult to provide sufficient active sites for water oxidation, leading to a decrease in in-situ H2O2 generation. Furthermore, Bi2MoO6 is prone to aggregation, hindering the molybdenum ion valence cycle and reducing Fenton-like reaction activity, ultimately resulting in reduced hydroquinone degradation efficiency and weakened photoelectric detection response signal. If this mass ratio is higher than 1:3, the amount of g-C3N4 is too large, easily leading to stacking and aggregation, covering and blocking active sites, and reducing the effective contact area of ​​the heterojunction interface. At the same time, the proportion of Bi2MoO6 active component is insufficient, limiting the amount of Mo2MoO6 that can participate in the valence cycle. 6+ / Mo 5+ The limited number of active sites makes it difficult to efficiently activate H2O2 to generate hydroxyl radicals. Furthermore, the increased overall conductivity of the electrode and the increased interfacial electron transport resistance lead to a decrease in the energy level matching and electron driving efficiency of the self-powered system, resulting in a significant deterioration in hydroquinone degradation performance and detection sensitivity. Only by controlling the mass ratio within the range of 1:2 to 3 can a heterojunction structure with excellent matching be formed, balancing light absorption capacity, carrier separation efficiency, in-situ H2O2 generation efficiency, and Fenton-like catalytic activity, enabling the system to simultaneously possess excellent hydroquinone detection and degradation performance.

[0010] Preferably, the mass ratio of Bi2MoO6 / g-C3N4 to CuS is 1:0.8~1.5. When the CuS ratio is below 0.8, the amount of CuS used in the photocathode is insufficient, resulting in an imbalance in the work function matching between the photocathode and the photoanode. This weakens the built-in electric field strength of the system and reduces the self-powered driving force. At the same time, the number of active sites on the cathode is small, the oxygen reduction reaction efficiency decreases, the in-situ generation of H2O2 decreases, the photogenerated electron receiving and transmission capabilities weaken, and the carrier separation effect deteriorates. Ultimately, this leads to a decrease in the yield of Fenton-like reaction ·OH, and a simultaneous decrease in the degradation efficiency of hydroquinone and the photoelectric detection sensitivity. When the CuS ratio exceeds 1.5, excessive CuS content can easily lead to agglomeration and accumulation, covering active sites on the electrode surface and increasing interfacial charge transport resistance. Excessive CuS disrupts the energy level matching between the two electrodes, damaging the self-powered electron transfer balance. Furthermore, too much CuS blocks incident light, weakens the photoanode's light energy absorption and utilization rate, and inhibits the synergistic effect of WOR and ORR, resulting in decreased H2O2 generation and activation efficiency, significantly reducing the overall performance of the system in detecting and degrading hydroquinone. Only by controlling the mass ratio of Bi2MoO6 / g-C3N4 to CuS within the range of 1:0.8~1.5, ensuring proper work function matching and energy level alignment between the two electrodes, and sufficient self-powered driving force, can efficient in-situ H2O2 generation and Fenton-like catalytic reaction be achieved synergistically, guaranteeing the system possesses both excellent detection sensitivity and pollutant degradation capabilities.

[0011] Preferably, the loading of both the photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS on the carbon cloth is 0.5 mg / cm³. 2 ~2.0mg / cm 2 .

[0012] Preferably, the concentration of the phosphate buffer is 0.1 mol / L to 0.5 mol / L, and the pH is 6.0 to 8.0.

[0013] Preferably, the illumination conditions are as follows: a 300W xenon lamp is used as the light source, the light wavelength is 400nm~760nm, and the light intensity is 50mW / cm². 2 ~150mW / cm 2 .

[0014] This invention also protects the application of light-driven self-powered Fenton systems in the detection and degradation of hydroquinone in water.

[0015] Preferably, the detection limit for hydroquinone is 17.4 pM.

[0016] Preferably, a light-driven self-powered Fenton system is used as the detection platform. The chronoamperometry (it curve method) is adopted to record the photocurrent response values ​​of hydroquinone solutions of different concentrations under 0V bias and visible light irradiation conditions. Based on the linear relationship between photocurrent density and the logarithm of hydroquinone concentration, the quantitative detection of unknown hydroquinone concentration is realized.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention designs a light-driven, self-powered Fenton-like system, which is a self-powered dual-electrode system based on a photoanode of Bi2MoO6 / g-C3N4 and a photocathode of CuS, for efficient detection and removal of HQ. This system utilizes the work function difference between the photoanode and photocathode as the self-powered driving force to achieve a light-assisted, self-powered Fenton-like reaction. Specifically, the photoanode Bi2MoO6 / g-C3N4 promotes carrier separation and transfer by constructing a type II heterojunction, thereby driving the WOR and ORR to generate H2O2, while simultaneously reducing Mo. 6+ The photocathode undergoes an ORR (Organic Reduction) process by accepting electrons, and the generated H₂O₂ shuttles to the photoanode. The H₂O₂ accumulated at the photoanode reacts with Mo… 5+ Further, a Fenton-like reaction occurs, promoting the generation of ·OH through the Mo valence state cycle. These ·OH have extremely strong oxidizing power and can efficiently detect and remove HQ.

[0018] 2. The self-powered dual-electrode system designed in this invention exhibits a linear detection range of 60 pM to 100 μM for HQ, with a detection limit of 17.4 pM, demonstrating a low detection limit and a wide detection range, meeting the needs of practical HQ detection. Furthermore, under illumination, this system can completely degrade 10 ppm of HQ within 30 minutes. Finally, by fabricating a kite-shaped sensor, it was successfully applied to the detection of HQ content in a campus pond, thus achieving the goal of efficient detection and removal of HQ in real-world environments.

[0019] 3. The present invention uses Bi2MoO6 / g-C3N4 as the photoanode because: graphitic carbon nitride (g-C3N4) has the advantages of non-metallic properties, good chemical stability, and tunable band gap. Moreover, it can generate H2O2 in situ through WOR and ORR under photoexcitation. However, due to the defects of low light absorption efficiency, high recombination rate of photogenerated carriers and poor conductivity, g-C3N4 is limited in practical applications. In order to overcome these limitations, the present invention uses band-matched metal-based semiconductor coupled with g-C3N4 to construct a heterostructure to improve light energy utilization, accelerate carrier migration, and trigger Fenton-like reactions. Considering that Bi2MoO6 has a unique layered structure and suitable conduction band / valence band positions, and that molybdenum-based materials are relatively stable and can maintain high catalytic activity over a wide pH range, this invention uses g-C3N4 and Bi2MoO6 to construct a heterojunction to improve light absorption capacity and separation efficiency of photogenerated carriers, thereby improving the degradation efficiency and detection performance of the target analyte.

[0020] This invention uses CuS as the photocathode because, in a self-powered two-electrode system, the photocathode material must possess a sufficient Fermi level difference and efficient electron accepting capacity with the photoanode to ensure effective electron transfer. The sulfur atoms in the p-type semiconductor CuS, due to their unfilled 3p orbitals, enhance the capture and transport of photogenerated electrons, promoting carrier separation and transport. Simultaneously, CuS's narrow bandgap (1.2 eV ~ 2.4 eV) allows it to absorb a wider range of the solar spectrum, thereby increasing the generation of photogenerated electron-hole pairs. These characteristics endow CuS with excellent photoelectric properties; therefore, CuS is selected as the photocathode material in a light-assisted self-powered Fenton system. Attached Figure Description

[0021] The Bi2MoO6 / g-C3N4 in the accompanying drawings of this invention are all samples from Example 1.

[0022] Figure 1 This is a schematic diagram of the synthesis of Bi2MoO6 / g-C3N4 according to the present invention.

[0023] Figure 2 Figures a through c in the image correspond to the SEM images of Bi2MoO6, g-C3N4, and Bi2MoO6 / g-C3N4, respectively; figures d through f correspond to the HR-TEM images of Bi2MoO6, g-C3N4, and Bi2MoO6 / g-C3N4, respectively; and figure g is the EDS image of Bi2MoO6 / g-C3N4.

[0024] Figure 3In the figure, a is the FT-IR spectrum of Bi2MoO6 / g-C3N4, Bi2MoO6 and g-C3N4, b is the XRD spectrum of Bi2MoO6 / g-C3N4, Bi2MoO6 and g-C3N4, c is the UPS spectrum of Bi2MoO6 and g-C3N4, and d is the high-resolution narrow spectrum of N 1s, Bi 4f and Mo 3d of Bi2MoO6 / g-C3N4, Bi2MoO6 and g-C3N4 under dark and light conditions.

[0025] Figure 4 Figures show the construction and characterization of the Bi2MoO6 / g-C3N4 heterojunction. Figure a shows the MS spectrum of Bi2MoO6; figure b shows the MS spectrum of g-C3N4; figure c shows the Tauc plots of the UV-Vis diffuse reflectance of Bi2MoO6 and g-C3N4; figure d shows the band structure of Bi2MoO6 and g-C3N4; figure e shows the PL spectra of Bi2MoO6 / g-C3N4, Bi2MoO6, and g-C3N4; figure f shows the EIS spectra of Bi2MoO6 / g-C3N4, Bi2MoO6, and g-C3N4 under darkness and illumination; and figure g shows the C40 at different rates for Bi2MoO6 / g-C3N4, Bi2MoO6, and g-C3N4 under darkness and illumination. dl picture.

[0026] Figure 5 The figures show the characterization of CuS photocathodes, where a is the XRD pattern of CuS, b is the MS pattern of CuS, c is the Tauc pattern of the UV-Vis diffuse reflectance of CuS, and d is the UPS spectrum of Bi2MoO6 / g-C3N4 and CuS.

[0027] Figure 6 These are characterization figures of the self-powered dual-electrode system constructed in this invention. Figure a shows the mechanism of H2O2 generation by the self-powered dual electrode; Figure b shows the H2O2 generation of the dual electrode, Bi2MoO6 / g-C3N4, Bi2MoO6, g-C3N4, and CuS under visible light (>400nm) irradiation; Figure c shows Bi2MoO6 / g-C3N4 in PBS=7 at a scan rate of 10mVs. −1 The RRDE polarization curves at 1600 rpm are shown in Figure d, which shows the selectivity (upper part) and corresponding average electron transfer number (lower part) of H2O2. Figure e shows the effect of adding various sacrificial agents on the formation of H2O2 from Bi2MoO6 / g-C3N4. Figure f shows the DMPO-∙O2 formation of Bi2MoO6 / g-C3N4, g-C3N4, Bi2MoO6, and CuS. - Figure g shows the ESR spectrum of DMPO-∙OH.

[0028] Figure 7 In the figure, a shows the HQ degradation process under different photoelectrodes within 40 minutes; b shows the kinetic fitting curves of HQ degradation under different photoelectrodes; c shows the comparison of HQ degradation rate of the self-powered dual-electrode system with other literature; d shows the effect of 10 minutes of light irradiation on HQ degradation of the self-powered dual-electrode system after adding various sacrificial agents; e shows the degradation mechanism of HQ by the self-powered dual-electrode system; and f shows the stability of HQ degradation by the self-powered dual-electrode system.

[0029] Figure 8 In the figure, a is the OCP test diagram of the self-powered dual photoelectrode system, b is the photocurrent response diagram during the molecular loading imprinting process, and c is the EIS diagram during the molecular loading imprinting process.

[0030] Figure 9 In the figure, Figure a shows the performance of the self-powered dual photoelectrode system assembled with different photoanode materials, Figure b shows the photocurrent density and fitted linear curve of the self-powered dual photoelectrode system in HQ solutions of different concentrations, and Figure c shows the comparison of LOD and linear range of the HQ detection method.

[0031] Figure 10 Figure a shows the stability, selectivity, and reproducibility of the self-powered dual photoelectrode system, and Figure b shows the structure of the self-powered kite device.

[0032] Figure 11 This is a practical application diagram of a self-powered kite device. The diagram includes the IT curve and ultraviolet absorption graph from laboratory tests, as well as images of laboratory field tests and outdoor tests on the right. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0034] This invention proposes a light-driven, self-powered Fenton-like system, employing Bi₂MoO₆ / g-C₃N₄ as the photoanode and CuS as the photocathode. A dual-electrode self-powered system is constructed by utilizing the difference in their work functions and applied to the degradation and monitoring of hazardous waste (HQ). Furthermore, the in-situ generation mechanism of H₂O₂ is investigated, and the potential mechanism of activating H₂O₂ through metal ion valence state cycling to achieve efficient HQ degradation and monitoring is explored. This innovative light-driven, self-powered Fenton-like system achieves a "two birds with one stone" effect, demonstrating its broad application prospects in environmental remediation and pollution control. Finally, a kite-shaped self-powered device is designed, which maintains excellent performance in HQ removal and monitoring in a real-world environment, proving its practical application potential.

[0035] The light-driven self-powered Fenton system of this invention also solves the problems of traditional Fenton systems, such as narrow applicable pH, easy precipitation, low H2O2 utilization, dependence on external power and high cost of electric Fenton, and the need for external H2O2 in conventional light Fenton, which can easily cause secondary pollution.

[0036] The technical solution of the present invention is studied through the following examples. In the examples of the present invention, Bi2MoO6 / g-C3N4 and CuS are prepared according to the following steps: Preparation of Bi2MoO6 / g-C3N4: Synthesis and ultrasonic exfoliation of S1 and g-C3N4: 10g of urea was placed in an alumina crucible, which was then placed in a muffle furnace and heated to 550℃ at 15℃ / min and maintained for 4h. The resulting powder was lumpy g-C3N4. The lumpy g-C3N4 was then dispersed in isopropanol at a ratio of 3mg / mL and subjected to ultrasonic treatment for 10 hours to obtain layered g-C3N4.

[0037] Preparation of S2, Bi2MoO6 / g-C3N4: 1) Synthesis of Bi2MoO6: Weigh 0.06 mmol of MoO3 and 0.14 mmol of Bi(NO3)3 and dissolve them in 3 mL of deionized water. Then, stir magnetically for 30 min, add 9 mL of ethylene glycol and stir for half an hour. Transfer the resulting solution to an autoclave and heat at 160 °C for 12 h. After cooling to room temperature, transfer the suspension to a centrifuge tube and wash with ethanol and deionized water as solvents, respectively. Finally, dry overnight in a vacuum drying oven to obtain Bi2MoO6.

[0038] 2) Synthesis of Bi2MoO6 / g-C3N4: 40 mg of Bi2MoO6 and 100 mg of g-C3N4 were dissolved together in 12 mL of ethylene glycol and magnetically stirred for 1 h. The solution was then placed in an autoclave and heated at 160 °C for 12 h. After cooling to room temperature, the suspension was transferred to centrifuge tubes and washed with ethanol and deionized water, respectively. Finally, it was dried overnight in a vacuum drying oven to obtain Bi2MoO6 / g-C3N4.

[0039] Preparation of CuS: 0.38 g of thiourea and 2 mmol of Cu(NO3)2·3H2O were dissolved in 10 mL of deionized water and stirred continuously for 1 h. The resulting solution was then transferred to an autoclave and maintained at 160 °C for 12 h. After the reaction, the solution was allowed to cool naturally to room temperature. The product suspension was then transferred to centrifuge tubes and washed twice by centrifugation at 8000 rpm using ethanol and deionized water as washing solvents. Finally, the washed sample was dried overnight in a vacuum drying oven to complete the sample preparation.

[0040] Example 1 The preparation method of the optically driven self-powered Fenton system includes the following steps: The carbon cloth was ultrasonically treated in ethanol and acetone for 10 min each, then ultrasonically treated in concentrated sulfuric acid / deionized water (1:1 volume ratio) for 1 h, washed until neutral, and dried to obtain the treated carbon cloth. Bi₂MoO₆ / g-C₃N₄ powder and CuS powder were prepared into uniform dispersions, and then drop-coated onto the treated carbon cloth, with the loading amount controlled at 1.0 mg / cm³. 2 The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were prepared by drying at room temperature.

[0041] Assembly of a light-driven, self-powered Fenton system: The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were placed in parallel opposite each other in a photoelectrochemical cell with an electrode spacing of 2 cm; a two-electrode system was constructed using 0.1 mol / L, pH 7.0 phosphate buffer (PBS) as the electrolyte.

[0042] Example 2 The preparation method of the optically driven self-powered Fenton system includes the following steps: The carbon cloth was ultrasonically treated in ethanol and acetone for 10 min each, then ultrasonically treated in concentrated sulfuric acid / deionized water (1:1 volume ratio) for 1 h, washed until neutral, and dried to obtain the treated carbon cloth. Bi₂MoO₆ / g-C₃N₄ powder and CuS powder were prepared into uniform dispersions and then drop-coated onto the treated carbon cloth, with a Bi₂MoO₆ / g-C₃N₄ powder loading of 1.0 mg / cm³. 2The CuS powder loading was 0.8 mg / cm³. 2 The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were prepared by drying at room temperature.

[0043] Assembly of a light-driven, self-powered Fenton system: The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were placed in parallel opposite each other in a photoelectrochemical cell with an electrode spacing of 1 cm; a two-electrode system was constructed using 0.3 mol / L phosphate buffered saline (PBS) as the electrolyte.

[0044] Example 3 The preparation method of the optically driven self-powered Fenton system includes the following steps: The carbon cloth was ultrasonically treated in ethanol and acetone for 10 min each, then ultrasonically treated in concentrated sulfuric acid / deionized water (1:1 volume ratio) for 1 h, washed until neutral, and dried to obtain the treated carbon cloth. Bi₂MoO₆ / g-C₃N₄ powder and CuS powder were prepared into uniform dispersions and then drop-coated onto the treated carbon cloth, with a Bi₂MoO₆ / g-C₃N₄ powder loading of 1.0 mg / cm³. 2 The CuS powder loading was 1.5 mg / cm³. 2 The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were prepared by drying at room temperature.

[0045] Assembly of a light-driven, self-powered Fenton system: The photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS were placed in parallel opposite each other in a photoelectrochemical cell with an electrode spacing of 5 cm; a two-electrode system was constructed using 0.5 mol / L phosphate buffered saline (PBS) as the electrolyte.

[0046] Detection method: Hydroquinone (HQ) degradation performance test method: Prepare a 10 ppm HQ solution, and add 50 mL to the reactor; immerse the light-driven self-powered Fenton system in the solution and stir in the dark for 30 min to reach adsorption-desorption equilibrium; turn on a 300W xenon lamp (λ > 400 nm) for irradiation, with the light source 5 cm above the liquid surface; take 3 mL of solution at regular intervals and filter it through a 0.22 μm filter membrane; measure the absorbance at 292 nm using a UV-Vis spectrophotometer, and calculate the HQ concentration according to the standard curve; Degradation rate calculation formula: Degradation rate = (C0 − C t ) / C0×100%, where: C0 is the initial concentration, C t Let t be the concentration at time t.

[0047] Hydroquinone photoelectrochemical detection method (it curve method): A two-electrode system was used, with Bi2MoO6 / g-C3N4 as the working electrode and CuS as the counter electrode; the electrolyte was 0.2 mol / L PBS (pH 7.0) solution; chronoamperometry (it) was used, with a bias voltage of 0V (self-powered mode); 300W xenon lamp irradiation was performed, with cycles of 20s of illumination followed by 20s of darkness; different concentrations of HQ were added successively, and the steady-state photocurrent density was recorded; a standard curve was plotted with lgC (HQ concentration) as the abscissa and photocurrent density as the ordinate to obtain the linear range and detection limit.

[0048] In-situ H2O2 generation test method (iodometric method): Take 2 mL of reaction solution under light irradiation at regular intervals, add 2 mL of 0.4 mol / L KI solution and 1 mL of 0.1 mol / L potassium hydrogen phthalate solution, react in the dark for 10 min, measure the absorbance at 352 nm, plot a standard curve using H2O2 standard solution, and calculate the H2O2 concentration.

[0049] Active free radical scavenging test method: 5mM scavenging agents were added respectively; tert-butanol (TBA) scavenged ·OH, and p-benzoquinone (pBQ) scavenged ·O2. - Methanol (MeOH) captures h + Argon (Ar) is used to remove dissolved oxygen, and HQ degradation or H2O2 generation tests are performed under the same conditions; the inhibition rate is compared to determine the main active species.

[0050] Stability testing method: Use the same set of electrodes to cycle through HQ degradation or photocurrent detection. After each test, rinse the electrodes with deionized water. Repeat the cycle 5 to 6 times and record the degradation rate or photocurrent retention rate. A retention rate > 80% is considered to indicate good stability.

[0051] Selectivity (interference immunity) test method: Add the interfering agent Ca to PBS separately. 2+ Cl - Ascorbic acid, glyphosate, bisphenol A, catechol, and resorcinol were used as interfering substances; the concentration of interfering substances was 10 to 100 times that of HQ. The photocurrent response was tested under 0V self-powered mode, and only HQ produced a significant signal change, which was judged to be good selectivity.

[0052] Photoelectrochemical performance testing methods: Electrochemical impedance spectroscopy (EIS): frequency 0.1Hz~100kHz, amplitude 5mV, tested at open circuit potential. Double layer capacitance (C dl ): CV tests were performed over the non-Radida potential range at scan rates of 20 mV / s to 100 mV / s. The current difference was plotted against the scan rate, and the slope was C. dlMott-Schottky (MS): Frequency 1000Hz, used to test semiconductor type and flat band potential. Rotating Ring-Disk Electrode (RRDE): Rotation speed 1600rpm, disk voltage -1.0V (vsRHE) ~ 0V (vsRHE), ring voltage 0.79V, used to calculate H2O2 selectivity and electron transfer number.

[0053] Actual water sample testing method (kite device): Collect pond / river water samples, let them stand and filter them through a Janus membrane; add a quantitative amount of HQ, and test using a kite-type self-powered device; at the same time, use ultraviolet spectrophotometry as a control; calculate the measured values, recovery rate and accuracy.

[0054] Results and Discussion: Figure 1 The process of preparing the photoanode Bi2MoO6 / g-C3N4 is shown. First, hollow spheres of Bi2MoO6 are hydrothermally synthesized using MoO3 and Bi(NO3)3 as raw materials. Then, bulk g-C3N4 prepared by urea pyrolysis is ultrasonically treated to exfoliate it into a nanosheet structure. Finally, the synthesized Bi2MoO6 is loaded onto the g-C3N4 nanosheets to construct a Bi2MoO6 / g-C3N4 heterostructure as the photoanode.

[0055] The morphology of Bi2MoO6, g-C3N4, and Bi2MoO6 / g-C3N4 was analyzed using scanning electron microscopy (SEM). Figure 2 As shown in Figure a, Bi₂MoO₆ exhibits a hollow nanosphere structure composed of coarse nanosheets, providing multiple reflections of incident light within the Bi₂MoO₆ structure, thus significantly enhancing its light absorption capacity; while g-C₃N₄ exhibits an irregular nanosheet structure and is prone to aggregation, such as... Figure 2 As shown in Figure b, after g-C3N4 is combined with Bi2MoO6, nanospheres of Bi2MoO6 are observed to adhere to the surface of g-C3N4, thereby increasing the effective surface area of ​​Bi2MoO6 / g-C3N4, as shown in Figure b. Figure 2 As shown in Figure c.

[0056] The microstructures of Bi₂MoO₆, g-C₃N₄, and Bi₂MoO₆ / g-C₃N₄ were further analyzed using transmission electron microscopy (TEM). Figure 2 As shown in Figure d, the lattice spacing of the Bi2MoO6 hollow spheres is 0.32 nm, which matches the (140) crystal plane in the orthorhombic Bi2MoO6 material (JCPDS-84-0787). Figure 2Figure e further shows that g-C3N4 has an irregular layered structure with curled edges. High-resolution transmission electron microscopy (HR-TEM) revealed a clear heterojunction interface between Bi2MoO6 and g-C3N4, as shown in the figure. Figure 2 As shown in Figure f, a lattice spacing of 0.43 nm corresponds to the (112) crystal plane of the Bi2MoO6 material. Figure 2 The g-plot in the figure shows the energy-dispersive X-ray spectroscopy (EDS) spectrum of Bi2MoO6 / g-C3N4, revealing a uniform distribution of Bi, Mo, C, N, and O elements throughout the structure. These results collectively demonstrate the successful synthesis of Bi2MoO6 / g-C3N4.

[0057] like Figure 3 As shown in Figure a, Fourier transform infrared spectroscopy (FT-IR) was used to determine the chemical structure and interactions of Bi₂MoO₆ / g-C₃N₄. In the spectrum of Bi₂MoO₆, 726 cm⁻¹... -1 The peak at 3100 cm⁻¹ is attributed to the asymmetric and symmetric stretching vibrations of Mo-O-Mo. In the g-C₃N₄ spectrum, the peak at 3100 cm⁻¹ is... -1 Up to 3500cm -1 The peaks within the range are attributed to the stretching vibrations of the -NH and -NH2 groups, 1200 cm⁻¹. -1 Up to 1700cm -1 The strong peaks observed within the range are attributed to vibrations of the C=N double bonds and CN single bonds, features consistent with the unique heterocyclic structure in g-C3N4; furthermore, at 818 cm⁻¹... -1 The sharp peak at the position matches the vibrational mode of the triazine ring, further confirming the structural characteristics of g-C3N4. After combining g-C3N4 with Bi2MoO6, the characteristic peaks of Bi2MoO6 / g-C3N4 are basically consistent with those of the pure g-C3N4 sample, indicating that the structure of g-C3N4 was well preserved during the composite process. The peak at 726 cm⁻¹... -1 The presence of the Bi2MoO6 characteristic peak at the point proves that the two have successfully recombinated.

[0058] like Figure 3Figure b shows the crystal structure and composition of the Bi2MoO6 / g-C3N4 photoanode analyzed by X-ray diffraction (XRD). The XRD pattern of pure Bi2MoO6 shows strong diffraction peaks at 2θ angles of 28.1°, 36.6°, 46.7°, and 58.5°, corresponding to the (131), (208), (202), and (331) crystal planes of the orthorhombic phase Bi2MoO6 (PDF#21-0102), respectively. The XRD pattern of g-C3N4 shows two significant peaks: the peak at 13.2° is generally associated with the (100) crystal plane, reflecting the structural features within the plane of the s-triazine ring unit, while the peak at 27.4° corresponds to the (002) crystal plane. After g-C3N4 was combined with Bi2MoO6, the XRD pattern showed diffraction peaks on the (002) crystal plane, characteristic of g-C3N4, indicating successful combination of Bi2MoO6 and g-C3N4. Furthermore, compared to Bi2MoO6 and g-C3N4 alone, the (002) crystal plane of g-C3N4 in Bi2MoO6 / g-C3N4 shifted towards lower angles, while the characteristic peaks of Bi2MoO6 shifted towards higher angles, indicating a strong, tight interface between the two composite components, which is beneficial for interfacial electron transport.

[0059] To clarify the electron migration behavior at the interface of the Bi2MoO6 and g-C3N4 heterojunction, the work functions of Bi2MoO6 and g-C3N4 were measured by ultraviolet photoelectron spectroscopy (UPS), which were 6.83 eV and 6.40 eV, respectively. Figure 3 As shown in Figure c, when Bi2MoO6 and g-C3N4 form a heterojunction, the difference in their work functions causes electrons to spontaneously transfer from g-C3N4 to Bi2MoO6 until their Fermi levels reach equilibrium. This process significantly enhances the effective separation of charge carriers and optimizes the photoelectric properties of the Bi2MoO6 / g-C3N4 composite material.

[0060] X-ray photoelectron spectroscopy (XPS) was used to further analyze the electron flow at the interface of the Bi2MoO6 and g-C3N4 heterojunction. Figure 3 As shown in Figure d, the three characteristic peaks in the high-resolution N 1s spectrum at 400.8 eV, 399.3 eV, and 398.5 eV are attributed to the sp² hybrid nitrogen atom in the triazine ring, the graphitic nitrogen (N-C3), and the amino nitrogen (NH4+) in g-C3N4, respectively. xAfter introducing Bi₂MoO₆, the binding energy of the N 1s peak shifted to higher binding energies, indicating a decrease in the electron density in g-C₃N₄ and a transfer of electrons from g-C₃N₄ to Bi₂MoO₆. Analysis of the high-resolution Bi₄f spectrum of Bi₂MoO₆ revealed binding energies at 159.21 eV and 164.47 eV, respectively, belonging to Bi₄f. 7 / 2 and Bi 4f 5 / 2 Characteristic peaks. In the high-resolution Mo 3d spectrum, Mo 3d... 3 / 2 and Mo 3d 5 / 2 The peak values ​​of the orbitals correspond to 232.52 eV and 232.29 eV, respectively, with each orbital decomposing into two peaks at 232.55 eV and 232.40 eV, corresponding to Mo. 6+ 235.00 eV and 231.95 eV correspond to Mo 5+ Upon recombination with g-C3N4, the binding energies of both Bi 4f and Mo 3d shift to lower binding energies, indicating electron migration from g-C3N4 to Bi2MoO6. Simultaneously, through the analysis of Mo... 6+ with Mo 5+ Comparison of peak area ratios further confirms that the Bi2MoO6 / g-C3N4 heterostructure drives the migration of electrons from g-C3N4 to Bi2MoO6, promoting the growth of Mo. 6+ Xiang Mo 5+ The reduction transformation. Notably, under illumination, the main peak in the N 1s spectrum shifts further to higher binding energies, while the binding energies of Bi 4f and Mo 3d shift to lower binding energies, indicating that illumination can further enhance electron migration at the Bi2MoO6 / g-C3N4 interface and accelerate carrier separation.

[0061] To further verify the carrier transfer direction in the photoanode Bi2MoO6 / g-C3N4, the absorption capacity and band structure of Bi2MoO6 and g-C3N4 were determined by Mott-Schottky (MS) measurement and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). Figure 4 As shown in Figures a and b, the slopes of both Bi₂MoO₆ and g-C₃N₄ are positive, indicating that both are n-type semiconductors with flat band potentials (E). f The values ​​are -0.39 eV and -1.00 eV, respectively. For example... Figure 4As shown in Figure c, the band gaps (Eg) of Bi₂MoO₆ and g-C₃N₄, calculated using the Tauc equation, are 2.53 eV and 2.97 eV, respectively. Therefore, the conduction band position (Eg) of Bi₂MoO₆ is calculated. CB ) and price band position (E VB The values ​​are -0.49 eV and 2.04 eV, respectively, for g-C3N4. CB and E VB The voltage levels are -1.10 eV and 1.87 eV, respectively. Based on the band positions of Bi2MoO6 and g-C3N4, and the transfer directions of photogenerated carriers before and after illumination, it is determined that Bi2MoO6 / g-C3N4 forms a type II heterojunction. Figure 4 As shown in Figure d, since the work function of Bi2MoO6 is greater than that of g-C3N4, after Bi2MoO6 and g-C3N4 come into close contact, the difference in work function makes it easier for electrons from g-C3N4 to flow to Bi2MoO6. The transfer direction of this photogenerated carrier conforms to the type II heterostructure. The resulting type II heterojunction structure is beneficial to improving the separation efficiency of photogenerated carriers in Bi2MoO6 / g-C3N4, slowing down the recombination of photogenerated carriers, and at the same time, it can generate more Mo under illumination. 5+ This promotes the valence state cycle at the Mo site.

[0062] The carrier separation efficiency of Bi2MoO6 / g-C3N4 was verified by photoluminescence (PL) spectroscopy. Figure 4 As shown in Figure e, Bi₂MoO₆ exhibits a significant emission peak at 645 nm. After recombination with g-C₃N₄, the emission peak decreases substantially, indicating that the formation of the type II heterostructure significantly suppresses the recombination of photogenerated carriers and effectively promotes charge transfer. To further verify the photogenerated carrier separation capability of Bi₂MoO₆ / g-C₃N₄, the charge transfer kinetics of Bi₂MoO₆ / g-C₃N₄ were characterized by electrochemical impedance spectroscopy (EIS). Figure 4 In the f-plot, Bi2MoO6 / g-C3N4 exhibits the lowest interfacial charge transfer resistance (Rf). ct This indicates that the charge transport resistance in this system is minimal. Under illumination, R ct Further reduction in the value reveals efficient separation and enhanced transport of photoinduced electron-hole pairs. This phenomenon is attributed to the fact that the construction of the heterojunction optimizes the interfacial charge dynamics, significantly reducing the carrier recombination rate.

[0063] The double-layer capacitance (C0) is obtained by calculating the cyclic current-voltage (CV) curve within the non-Radial region. dlThis study aims to estimate the electrochemically active specific surface area (ECSA) of the Bi2MoO6 / g-C3N4 anode material and assess the number of electrochemically active sites on the Bi2MoO6 / g-C3N4 surface. Figure 4 As shown in the g-plot, Bi2MoO6 / g-C3N4 exhibits the highest C content. dl The high C value is due to the redistribution of electronic state density caused by spontaneous electron migration at the interface, resulting in abundant surface active sites. Under photoexcitation conditions, the C of Bi2MoO6 / g-C3N4... dl The value further increases, indicating that illumination can not only promote charge transfer, but also promote the valence state cycle of Mo sites by enhancing the separation of charge carriers, thereby indirectly improving the effective utilization efficiency of surface active sites.

[0064] To construct a self-powered dual-electrode system that matches the Bi2MoO6 / g-C3N4 heterojunction of the photoanode, p-type semiconductor CuS was selected as the photocathode. Figure 5 As shown in Figure a, XRD analysis revealed that the diffraction pattern of the synthesized CuS sample was consistent with the standard data in (JCPDS No. 06-0464), confirming the successful preparation of CuS. Figure 5 As shown in Figure b, the photocathode CuS exhibits a negative slope, proving that CuS is a p-type semiconductor with a high Ep. f The band gap of CuS is 0.96 eV; and the band gap of CuS is calculated to be 1.67 eV using the Tauc equation. Figure 5 The figure in Figure c shows the result; further calculation of E for CuS is required. CB and E VB They are located at -0.61 eV and 1.06 eV, respectively. Meanwhile, Figure 5 The d-plot in the figure shows that the work functions of the photoanode Bi2MoO6 / g-C3N4 and the photocathode CuS are 6.87 eV and 7.99 eV, respectively. The difference in work functions between the two electrodes provides the necessary driving force for electron transfer, promoting the transfer of photogenerated electrons within the dual-photoelectrode system, thus forming a self-powered dual-electrode system that can operate without an external power source.

[0065] Figure 6 Figure a illustrates the working mechanism of H2O2 generation in the self-powered two-electrode system: Due to the type II heterojunction of the photoanode Bi2MoO6 / g-C3N4, photogenerated electrons generated by illumination can rapidly transfer from the CB region of g-C3N4 to the CB region of Bi2MoO6. This is because O2 / ·O2 - The standard redox potential is 0.08 eV, while the E of Bi₂MoO₆ is... CB The voltage is -0.49 eV, therefore the photogenerated electrons accumulated at the CB of Bi2MoO6 trigger the O2→·O2 transition. -→ H2O2 reaction, and simultaneously, since the oxidation potential of H2O to H2O2 is 1.76 eV, the E of g-C3N4 VB The voltage is 1.87 eV, therefore photogenerated holes trigger WOR. Because the valence band position of CuS is higher than that of O2 to ·O2... - CuS has a lower reduction potential, which means that when exposed to light, the photogenerated electrons produced by CuS can also promote the conversion of O2 to ·O2. - And ultimately, H2O2 is generated. Finally, the H2O2 generated by the two electrodes is reacted with the Mo formed in the photoanode due to the heterojunction. 5+ The reduction generates ·OH, which is the main active species for the detection and degradation of HQ, while Mo... 5+ Oxidized by H2O2 to Mo 6+ This enables the valence state cycle of molybdenum.

[0066] The application potential of a self-powered dual-photoelectrode system for generating H2O2 under illumination was evaluated by testing the standard H2O2 concentration. Figure 6 Figure b shows the process of H2O2 generation by different electrodes under visible light irradiation. g-C3N4 and Bi2MoO6 exhibit very low efficiencies in H2O2 generation under light irradiation, with efficiencies of only 433.65 μmol h⁻¹. -1 and 382.75 μmol h -1 The H2O2 formation rate on Bi2MoO6 / g-C3N4 increased significantly, reaching 586.85 μmol h⁻¹. -1 This indicates that Bi2MoO6 / g-C3N4 exhibits higher photocatalytic activity for H2O2 production than both g-C3N4 and Bi2MoO6. In the self-powered dual-photoelectrode system, the H2O2 generation rate on the CuS photocathode alone is 258.67 μmol / h. -1 The H2O2 generation rate of the two electrodes reached 947.08 μmol h⁻¹. -1 This demonstrates that the two-electrode system can further promote the generation of H2O2.

[0067] Electrochemical measurements of the electron transfer process (ORR) on Bi₂MoO₆ / g-C₃N₄ were investigated using a rotating ring-disk electrode (RRDE). Polarization linear sweep voltammetry (LSV) curves of Bi₂MoO₆ / g-C₃N₄ were acquired at 1600 rpm, and the H₂O₂ detection current was acquired at a constant potential of 1.2 V (vs. RHE) using a Pt ring electrode. Figure 6As shown in Figure c, an ORR reaction occurs at the disk electrode, with a negative reduction current detected. Simultaneously, the H2O2 generated on the disk electrode rapidly diffuses to the Pt ring electrode and is oxidized, generating a positive oxidation current. Under illumination, Bi2MoO6 / g-C3N4 exhibits a higher ring current density, indicating that Bi2MoO6 / g-C3N4 has better catalytic activity for ORR under illumination. The hydrogen peroxide yield (H2O2%) and electron transfer number (n) were calculated based on the measured disk current, ring current, and collection efficiency, as shown below. Figure 6 As shown in Figure d, the average H2O2 selectivity of Bi2MoO6 / g-C3N4 is 74.65%, with an electron transfer number of approximately 2.7, indicating that 2e- ... − The process is dominant.

[0068] like Figure 6 As shown in Figure e, a series of capture experiments were conducted to identify the active species involved in the H2O2 generation process, thereby exploring the reaction mechanism of H2O2 generation from Bi2MoO6 / g-C3N4 and CuS. Argon (Ar) was used to remove dissolved O2 from the reaction solution, while p-benzoquinone (p-BQ) was mainly used to remove ·O2. - Methanol (MeOH) was used to shield photogenerated holes in the material, and tert-butanol (TBA) was used to remove ·OH from the reaction solution. Introducing Ar inhibited the formation of H2O2 on Bi2MoO6 / g-C3N4, and the amount of H2O2 generated increased by 34.9% when O2 was introduced into the system. This phenomenon indicates that dissolved oxygen can promote H2O2 formation through ORR. After adding MeOH, the formation of H2O2 on Bi2MoO6 / g-C3N4 was significantly inhibited, with a 21.8% reduction compared to the control experiment, indicating that besides ORR, WOR is also a major pathway for H2O2 formation. The addition of p-BQ significantly reduced the corresponding H2O2 formation rate, revealing that ·O2... - It plays an indispensable role in the synthesis of H2O2, thus confirming the indirect two-step two-electron reduction reaction. The addition of TBA has no significant effect on the formation of H2O2 in the Bi2MoO6 / g-C3N4 heterojunction, indicating that ·OH contributes little to the formation of H2O2.

[0069] like Figure 6 As shown in Figure f, Bi2MoO6 / g-C3N4 exhibits stronger DMPO-O2 activity under illumination compared to Bi2MoO6 and g-C3N4 alone. - The signal is due to the heterojunction forming promoting interfacial charge transfer, and further confirms that under illumination, Bi2MoO6 / g-C3N4 undergoes indirect two-step 2e transfer. - The ORR process generates H2O2. For example... Figure 6As shown in Figure g, under illumination, Bi2MoO6 / g-C3N4, g-C3N4, and Bi2MoO6 all exhibit peaks with an intensity ratio of 1:2:2:1, which are attributed to the characteristic signal of DMPO-·OH. However, the ·OH signal intensity in the Bi2MoO6 / g-C3N4 heterojunction is significantly higher than that in Bi2MoO6 and g-C3N4, indicating that this heterojunction can promote the efficient decomposition of H2O2 to generate a large amount of ·OH. It is worth noting that although CuS, like Bi2MoO6 / g-C3N4, exhibits a significant DMPO-·O2... - The signal is strong, but the ·OH signal is very weak, indicating that CuS can effectively promote the production of H2O2, but cannot initiate a Fenton-like reaction.

[0070] To evaluate the degradation performance of HQ in a self-powered dual-photoelectrode system, degradation experiments were conducted on different photoelectrodes. For example... Figure 7 As shown in Figure a, after 40 minutes of illumination, the degradation efficiency of HQ by the photocathode CuS was only 17.3%. This is mainly because CuS failed to effectively catalyze the conversion of H2O2 to ·OH, thus limiting the degradation rate of HQ. In contrast, g-C3N4 alone readily recombines with photogenerated carriers, resulting in a HQ degradation efficiency of 24.3%. Due to Mo... 5+ -Mo 6+ The valence state cycle was investigated, and Bi₂MoO₆ alone promoted the Fenton-like reaction and significantly improved the degradation efficiency of HQ to 32.5%. When Bi₂MoO₆ and g-C₃N₄ combined to form a type II heterojunction, it not only effectively induced the separation of photogenerated carriers but also further promoted ·OH, ultimately achieving a 96.4% degradation of HQ within 40 minutes. Furthermore, the self-powered dual-photoelectrode system effectively promoted the separation of photogenerated carriers and the generation of H₂O₂, achieving a 98.4% degradation of HQ within 30 minutes under illumination.

[0071] like Figure 7 Figure b in the diagram illustrates the kinetic degradation process of HQ in the self-powered dual-photoelectrode system, using the Langmuir-Hinshelwood first-order kinetic model. The slope values ​​in this model correspond to the degradation rate constant k for each electrode, reflecting the reactivity of HQ molecules on the electrode surfaces. Experimental results show that the degradation rate constants for CuS, g-C3N4, Bi2MoO6, and Bi2MoO6 / g-C3N4 are 0.0064 min⁻¹. -1 0.0077min -1 0.023min -1 0.044min -1 The degradation rate constant of the self-powered dual photoelectrode system reached 0.14 min. -1The degradation rate was significantly higher than that of other electrodes, thus confirming that this self-powered dual electrode has higher efficiency in HQ degradation. Furthermore, as... Figure 7 As shown in Figure c, compared with other reported catalysts, the self-powered dual photoelectrode system results in shorter HQ degradation time and higher degradation efficiency.

[0072] like Figure 7 As shown in Figure d, the degradation mechanism of HQ in the two-electrode system was investigated using a free radical capture experiment under 10 min of illumination. Compared with the control group, the presence of MeOH decreased the HQ degradation efficiency by 27%, indicating that photogenerated holes can affect HQ degradation. Meanwhile, the introduction of Ar reduced the HQ degradation efficiency by 20%, while the introduction of O2 increased the HQ degradation efficiency by 13%, further demonstrating the positive role of dissolved oxygen in promoting HQ degradation. Most importantly, the presence of TBA significantly reduced the HQ degradation efficiency by 40%, clearly indicating that ∙OH plays a decisive role in the HQ degradation process. In summary, photogenerated holes and dissolved oxygen are key factors affecting H2O2 generation in the two-electrode system, while ∙OH is the main reactive species affecting HQ degradation.

[0073] Based on the changes in reactants during H2O2 generation and HQ degradation, a reaction mechanism for HQ degradation in dual photoelectrodes is proposed. Figure 7 As shown in Figure e, due to the lower work function of Bi2MoO6 / g-C3N4 compared to CuS, photogenerated electrons in Bi2MoO6 / g-C3N4 can spontaneously migrate to the CuS surface via an external circuit under illumination. These electrons reaching the CuS surface promote the generation of H2O2 through ORR. Simultaneously, holes accumulated on g-C3N4 further promote the synthesis of H2O2 via WOR. During this process, the in-situ generated H2O2 accumulates on the Bi2MoO6 / g-C3N4 surface and reacts with Mo in Bi2MoO6. 5+ The reaction produces Mo. 6+ And highly reactive ·OH. At this point, HQ molecules in the solution adsorb onto the photoanode surface and react with the generated ·OH to eventually mineralize and degrade into CO2 and H2O.

[0074] like Figure 7 As shown in Figure f, the self-powered dual-photoelectrode system maintained a high degradation efficiency of 96.6% during the initial four cycles. Although the degradation efficiency declined slightly in subsequent cycles, the entire system still maintained a degradation efficiency of over 83%. This result demonstrates the stability and reusability of the system.

[0075] like Figure 8As shown in Figure a, the operating mechanism of the self-powered system was verified by measuring the open-circuit potential (OCP). Under dark conditions, the OCP of the two-electrode system was -0.21V, indicating that the electron concentration in the photoanode was higher than that in the photocathode, thus promoting electron migration from the photoanode to the photocathode. Under illumination, the OCP gradually increased, indicating that photoexcitation led to the generation of a large number of photogenerated electrons in the photoanode, which subsequently migrated to the photocathode surface. Therefore, the photoanode became positively charged, while the photocathode surface became negatively charged. This transition further confirmed the efficient migration of photogenerated electrons from the photoanode to the photocathode surface, thus verifying the light-assisted self-powered capability. Furthermore, the OCP decreased rapidly upon the addition of HQ, indicating that HQ preferentially adsorbed onto the photoanode surface and underwent an oxidation reaction, promoting the migration of additional electrons to the photocathode, thereby enhancing the photocurrent and achieving the detection objective.

[0076] To achieve highly sensitive detection of HQ, a method combining molecularly imprinted polymers (MIPs) with a photoanode of Bi₂MoO₆ / g-C₃N₄ was employed to enhance its selective recognition capability. For example... Figure 8 As shown in Figure b, MIP films were prepared on the photoanode Bi₂MoO₆ / g-C₃N₄ via electropolymerization of p-phenylene diamine (PPD). The decreased conductivity caused by the dense polymer film formed through electropolymerization led to a sharp drop in the photocurrent of MIP / Bi₂MoO₆ / g-C₃N₄ to 64.8% of its original value. After template elution, the polymer film exposed imprint recognition sites, causing the photocurrent of rMIP / Bi₂MoO₆ / g-C₃N₄ to recover to 90.1% of its initial value, indicating the successful construction of rMIP / Bi₂MoO₆ / g-C₃N₄. Figure 8 As shown in Figure c, EIS analysis revealed that after elution, rMIP / Bi2MoO6 / g-C3N4 exhibited a lower charge transfer resistance compared to the non-imprinted polymer NIP / Bi2MoO6 / g-C3N4 electropolymerized by PPD, further confirming the successful preparation of rMIP / Bi2MoO6 / g-C3N4.

[0077] To evaluate the performance of this dual-electrode self-powered system, the transient changes in photocurrent before and after the addition of the HQ were measured using the chronoamperometry (it) method. Figure 9 As shown in Figure a, rMIP-Bi2MoO6 exhibits a wavelength of 0.28 μA cm⁻. 2 The photocurrent density of rMIP-g-C3N4 is 0.33 μA cm⁻. 2 After adding 100 μM HQ, the photocurrent increased to 0.67 μA cm⁻. 2and 0.53μA cm⁻ 2 In comparison, the photocurrent density of the rMIP-Bi2MoO6 / g-C3N4 heterojunction is increased to 0.64 μA cm⁻ 2 When 100 μM HQ was added to the system, the photocurrent density of rMIP-Bi2MoO6 / g-C3N4 significantly increased to 3.65 μA cm⁻. 2 The concentration increased by approximately 3.5 times compared to the result without added HQ. This is because the rMIP-Bi2MoO6 / g-C3N4 composite material can effectively generate a large amount of ·OH to oxidize HQ, thus exhibiting excellent performance in HQ detection. Figure 9 As shown in Figure b, we investigated the relationship between different concentrations of the target analyte HQ and the photocurrent response to evaluate the photoelectric detection performance of the dual-electrode self-powered system. With an exponential increase in HQ concentration, the photocurrent density also increased, exhibiting a good linear relationship. The linear regression equation is expressed as j(μA cm⁻¹). 2 )=0.431 lgC HQ (pM)+0.174(R) 2 =0.9992), where j is defined as the photocurrent density after the addition of HQ. This dual-electrode self-powered system exhibits a linear detection range for HQ from 60 pM to 100 μM, with a detection limit as low as 17.4 pM. Compared to currently reported HQ electrochemical / photoelectrochemical sensors, this dual-electrode self-powered system not only possesses a wider linear detection range but also a lower detection limit, see [reference needed]. Figure 9 Figure c in the diagram.

[0078] Figure 10 Figure a in the diagram illustrates the stability, selectivity, and reproducibility of the dual-electrode self-powered system for monitoring HQ. Under room temperature conditions, the relative standard deviations (RSDs) of the photocurrent responses obtained before and after the addition of HQ for monitoring the same dual-electrode self-powered device over seven consecutive days were 0.52% and 0.18%, respectively, indicating that the dual-electrode self-powered system possesses excellent stability. Selectivity and anti-interference capabilities are key indicators for evaluating the sensor's ability to achieve accurate detection in complex environments; therefore, we tested the self-powered device in blank solution and in solutions containing other common interfering substances, such as Ca2+. 2+ Cl -The photocurrent response in solutions containing dopamine (AA), glyphosate (GLY), bisphenol A (BPA), catechol (CC), and resorcinol (RC) was investigated. Results showed a significant enhancement in the photocurrent response in HQ solution. Although CC and RC have some structural similarities to HQ, their impact on the photocurrent response was relatively small, while other interfering substances showed almost no change in solution, demonstrating the high selectivity of this dual-electrode self-powered system for HQ. To evaluate the reproducibility of HQ detection, the consistency of photocurrent response between electrodes prepared in different batches was tested. Results showed that the relative standard deviation (RSD) between electrodes before and after the addition of HQ was only 0.69% and 0.12%, respectively, indicating good reproducibility of the dual-electrode self-powered system.

[0079] Preparation of Janus membrane: A PVDF ultrafiltration membrane was used as the base membrane and ultrasonically cleaned with ethanol and deionized water for 10 min in sequence and then dried. A 1.0% (w / w) chitosan acetic acid solution was uniformly coated on the front side of the base membrane and vacuum dried at 55℃ for 30 min. Then, a 0.5% (w / w) hydrophobic modified silica dispersion was coated on the back side of the base membrane and heat-treated at 65℃ for 1 h to obtain a Janus membrane with hydrophilic adsorption on one side and hydrophobic filtration on the other side.

[0080] To explore the capabilities of a dual-electrode system in practical applications, a kite-shaped self-powered device was designed for real-time detection and Fenton-like degradation of HQ in water samples. Figure 10 As shown in Figure b, the sensor is designed with an area of ​​400 cm². 2 The dual-functional partition structure includes a sensing area and a degradation area. Each area uses a chip layer with carbon cloth as a flexible substrate. The degradation area is coated with Bi2MoO6 / g-C3N4 photoanode material and CuS photocathode material. A Janus thin film, independently developed in the laboratory, is also incorporated as an adsorption layer to filter solid impurities in the river water, reducing background interference. The total sensing area is 2 cm². 2 The photoanode material rMIP-Bi2MoO6 / g-C3N4 with integrated MIP film and the photocathode material CuS are used to enhance the selectivity and photoresponse efficiency for the target analyte HQ. The upper layer of the encapsulation layer uses a transparent PET film coated with conductive ink to ensure optical transparency and electrical signal transmission. The lower layer uses a microporous PVDF (polyvinylidene fluoride) ultrafiltration membrane to encapsulate the catalyst to prevent its loss, and the exposed edges and lines are further sealed by a polystyrene coating to ensure long-term durability.

[0081] like Figure 11As shown in Figures a and b, to verify the sensing and degradation performance of the kite-like device, we collected a 5L water sample from a pond at Northwestern University and conducted tests under laboratory conditions. The experimental results showed that the photocurrent density of the pond water sample was 2.70 μA cm⁻¹. -2 The concentration of HQ in the water sample was calculated to be 562.4 nM using a linear regression equation. Simultaneously, independent verification was performed using ultraviolet spectroscopy, and the HQ concentration was calculated to be 552.1 nM using a standard HQ concentration fitting curve. Measurements were taken every 5 minutes thereafter, and the results from both methods remained consistent, demonstrating the accuracy and reliability of the device's real-time detection. After 30 minutes of illumination, HQ was completely degraded, indicating that the kite-shaped self-powered device possesses highly efficient degradation capabilities.

[0082] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A light-driven, self-powered Fenton-like system, characterized in that, The light-driven self-powered Fenton system is a self-powered dual-electrode system based on a photoanode Bi2MoO6 / g-C3N4 and a photocathode CuS. This system uses the difference in work function between the photoanode and the photocathode as the driving force for self-powering, thereby enabling the occurrence of light-assisted self-powered Fenton reactions.

2. A method for preparing the optically driven self-powered Fenton system as described in claim 1, characterized in that, Includes the following steps: Bi2MoO6 / g-C3N4 and CuS were prepared separately. Bi2MoO6 / g-C3N4 was loaded onto a carbon cloth substrate to prepare a photoelectric anode Bi2MoO6 / g-C3N4; CuS was loaded onto a carbon cloth substrate to prepare a CuS photocathode. The photoanode and photocathode are placed parallel to each other in a photoelectrochemical reaction cell, with phosphate buffer solution as the electrolyte, to form a two-electrode system. A light-driven Fenton-like reaction was carried out under room temperature and light conditions, driven by a self-powered system.

3. The preparation method of the optically driven self-powered Fenton system according to claim 2, characterized in that, In the photoanode Bi2MoO6 / g-C3N4, the mass ratio of Bi2MoO6 to g-C3N4 is 1:2~3.

4. The preparation method of the optically driven self-powered Fenton system according to claim 2, characterized in that, The mass ratio of Bi2MoO6 / g-C3N4 to CuS is 1:0.8~1.

5.

5. The method for preparing the optically driven self-powered Fenton system according to claim 2, characterized in that, The loading amounts of Bi2MoO6 / g-C3N4 and CuS on the carbon cloth substrate were both 0.5 mg / cm³. 2 ~2.0mg / cm 2 .

6. The method for preparing the optically driven self-powered Fenton system according to claim 2, characterized in that, The concentration of phosphate buffer is 0.1 mol / L to 0.5 mol / L, and the pH is 6.0 to 8.

0.

7. The method for preparing the optically driven self-powered Fenton system according to claim 2, characterized in that, The lighting conditions are as follows: a 300W xenon lamp is used as the light source, the light wavelength is 400nm~760nm, and the light intensity is 50mW / cm². 2 ~150mW / cm 2 .

8. The application of the light-driven self-powered Fenton system as described in claim 1 in the detection and degradation of hydroquinone in water.

9. The application according to claim 8, characterized in that, The detection limit for hydroquinone is 17.4 pM.

10. The application according to claim 8, characterized in that, Using a light-driven, self-powered Fenton system as the detection platform, the photocurrent response values ​​of hydroquinone solutions of different concentrations were recorded under 0V bias and visible light irradiation conditions using the chronoamperometry method. Based on the linear relationship between photocurrent density and the logarithm of hydroquinone concentration, the quantitative detection of unknown hydroquinone concentration was achieved.

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