Photocathode catalyst and electrode preparation method and application thereof

Abstract

The application discloses a molybdenum monatomic anchored gamma-Fe2O3 photoelectric cathode catalyst, a preparation method of an electrode thereof and application of the catalyst to photoelectrocatalytic degradation of pollutants in water bodies. The molybdenum monatomic anchored gamma-Fe2O3 photoelectric cathode catalyst comprises a gamma-Fe2O3 carrier and molybdenum atoms anchored on the surface of the gamma-Fe2O3 carrier in the form of monatomic atoms, wherein the molybdenum atoms are anchored by replacing part of iron sites in the gamma-Fe2O3 crystal lattice. The preparation method comprises the following steps: mixing and impregnating a molybdenum precursor solution with gamma-Fe2O3, and evaporating dry; and performing twice calcination on the obtained solid to obtain the molybdenum monatomic anchored gamma-Fe2O3 photoelectric cathode catalyst; in the twice calcination, the first time calcination is performed at 250-350 DEG C in an oxygen-containing atmosphere, and the second time calcination is performed at 450-550 DEG C in an inert atmosphere.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a single-atom catalyst suitable for the efficient degradation of antibiotic pollutants, its preparation method, and its application in the field of photoelectrocatalysis. Background Technology

[0002] Tetracycline is persistent and difficult to degrade in the environment, posing a threat to ecosystems and human health. Traditional treatment methods are limited by their inherent limitations. For example, physical adsorption and activated sludge technologies rely primarily on adsorption mechanisms rather than chemical degradation, and therefore cannot completely remove tetracycline. Biodegradation technology, as an environmentally friendly treatment method, also cannot rapidly eliminate tetracycline due to its slow degradation kinetics. Photocatalysis, a solar-driven catalytic reaction process, is considered a promising technology for effectively degrading organic pollutants in wastewater due to its low energy consumption and high efficiency. However, this technology is limited by the low utilization rate of sunlight and the easy recombination of photogenerated electrons and holes in semiconductors.

[0003] Photoelectrocatalysis can effectively utilize light and electrical energy to drive the reaction, making it an ideal method for degrading such pollutants.

[0004] For example, patent specification CN119660898A discloses a photoelectrocatalytic material electrode, its preparation method, and its application in the degradation of tetracycline wastewater. The electrode is prepared by the method, which includes preparing a titanium suboxide-doped cellulose nanofiber hydrogel; after a first pretreatment, a titanium strip after a second pretreatment is attached to the front and back of one end of the titanium suboxide-doped cellulose nanofiber hydrogel to obtain a titanium suboxide-doped cellulose nanofiber hydrogel electrode sheet; the portion of the electrode sheet below the titanium strip is immersed in a MOF dispersion solution and subjected to loading treatment under stirring to obtain a dual three-dimensional structure photoelectrocatalytic material electrode.

[0005] For example, the patent specification with publication number CN115159632A discloses a method for preparing and applying WO3@NiFe-LDHs photoanodes. By loading layered bimetallic hydroxide NiFe-LDHs onto FTO glass, a heterojunction photoanode of WO3@NiFe-LDHs is obtained, realizing photoelectrocatalysis for the stable and efficient removal of tetracycline pollutants under illumination.

[0006] γ-Fe₂O₃ has attracted attention due to its suitable band gap, good biocompatibility, and excellent magnetic properties; however, its rapid recombination of photogenerated carriers limits its catalytic efficiency. Single-atom modification is an effective strategy for optimizing catalyst performance. Currently, there are no reports on anchoring molybdenum (Mo) single atoms on the surface of γ-Fe₂O₃ for photoelectrocatalytic degradation of tetracycline. Therefore, developing a highly active and stable Mo single-atom modified γ-Fe₂O₃ photoelectrocatalyst is of great significance. Summary of the Invention

[0007] To address the aforementioned technical problems and shortcomings in this field, this invention provides a molybdenum single-atom modified γ-Fe2O3 catalyst with excellent photoelectrocatalytic performance, its simple preparation method, and its application in the photoelectrocatalytic degradation of pollutants (especially tetracycline antibiotics) in water. By anchoring molybdenum single atoms on the surface of γ-Fe2O3 to modulate its electronic structure and improve its photoelectrocatalytic performance, the problems of rapid photocharge recombination and low catalytic efficiency of existing γ-Fe2O3 photocathodes can be solved.

[0008] The specific technical solution is as follows:

[0009] In a first aspect, the present invention provides a molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst, comprising a γ-Fe2O3 support and molybdenum atoms anchored in single-atom form on the surface of the γ-Fe2O3 support, wherein the molybdenum atoms are anchored by replacing some iron sites in the γ-Fe2O3 lattice.

[0010] In some preferred embodiments, the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst has a molar percentage of molybdenum atoms to γ-Fe2O3 of 25% to 30%, such as 26%, 27%, 28%, 29%, etc., preferably 27% to 28%.

[0011] In a second aspect, the present invention provides a method for preparing the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst described in the first aspect, comprising:

[0012] The molybdenum precursor solution was mixed with γ-Fe2O3 and impregnated and then evaporated to dryness. The resulting solid was calcined twice to obtain the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst.

[0013] In the two calcinations, the first calcination is carried out in an oxygen-containing atmosphere (such as air or oxygen flow) at 250~350℃ (e.g., 300℃), and the second calcination is carried out in an inert atmosphere at 450~550℃ (e.g., 500℃).

[0014] This invention employs a specific two-stage calcination process to anchor molybdenum in single-atom form on the γ-Fe₂O₃ surface. In some preferred embodiments, the first calcination is followed by cooling, and then a second calcination is performed at a higher temperature. In this invention, the inert atmosphere refers to a gaseous atmosphere that does not participate in the reaction, such as rare gases like argon or nitrogen.

[0015] In the preparation method of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst, the first calcination aims to decompose the molybdenum precursor and remove its water of crystallization and volatile components. The second calcination is crucial and can promote the complete transformation of the crystal form into γ-Fe2O3 supported by molybdenum single atoms.

[0016] In some preferred embodiments, the method for preparing the molybdenum single-atom anchored γ-Fe₂O₃ photocathode catalyst includes one or more of ammonium molybdate, phosphomolybdic acid, molybdic silicosinate, sodium molybdate, and molybdate chloride. Further, the ammonium molybdate preferably includes ammonium heptamolybdate ((NH₄)₆Mo₇O₇. 24 Furthermore, the ammonium heptamolybdate may contain water of crystallization.

[0017] In some preferred embodiments, the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst preparation method is wherein the concentration of the molybdenum precursor in the molybdenum precursor solution is 0.1~0.6 mol / L.

[0018] In some preferred embodiments, the method for preparing the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst involves adding the γ-Fe2O3 in powder form.

[0019] The process of mixing and impregnating the molybdenum precursor solution with γ-Fe2O3 and then evaporating it to dryness facilitates the molecular-level dispersion of the molybdenum precursor on the support surface, laying the foundation for the subsequent formation of single-atom structures.

[0020] In some preferred embodiments, the preparation method of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst involves mixing, impregnating, and evaporating at a temperature of 60-90°C, such as 80°C.

[0021] In some preferred embodiments, the preparation method of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst involves mixing, impregnation, and evaporation under stirring conditions. Further, the stirring speed is preferably 300-800 rpm.

[0022] In some preferred embodiments, the preparation method of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst involves a first calcination time of 2 to 5 hours, such as 3 hours.

[0023] In some preferred embodiments, the preparation method of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst involves a second calcination time of 2 to 5 hours, such as 3 hours.

[0024] In some preferred embodiments, the method for preparing the γ-Fe2O3 includes:

[0025] In the presence of a precipitant, ferric salts and ferrous salts undergo a co-precipitation reaction in solution. The solid-liquid separation (e.g., centrifugation, filtration) is performed to collect the precipitate, which is then washed, dried, and subjected to two calcinations to obtain γ-Fe2O3.

[0026] In some preferred embodiments, the precipitant in the method for preparing γ-Fe2O3 includes one or more of sodium hydroxide, potassium hydroxide, and ammonia.

[0027] In some preferred embodiments, in the method for preparing γ-Fe2O3, the trivalent iron salt includes one or more of ferric chloride, ferric nitrate, and ferric sulfate.

[0028] In some preferred embodiments, in the method for preparing γ-Fe2O3, the divalent ferrous salt includes one or more of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0029] In some preferred embodiments, in the preparation method of γ-Fe2O3, the molar ratio of ferric iron in the ferric salt to ferrous iron in the ferrous salt is 1:(1.5~2.5), for example 1:2, etc.

[0030] In some preferred embodiments, in the method for preparing γ-Fe2O3, the coprecipitation reaction is carried out at a solution pH of 8 to 12 (e.g., 9, 10, 11, etc.), preferably 9 to 10.

[0031] In some preferred embodiments, the coprecipitation reaction in the preparation method of γ-Fe2O3 takes 1 to 4 hours, which allows the precipitate to be fully generated and aged.

[0032] In some preferred embodiments, the drying process for preparing γ-Fe2O3 is carried out under normal pressure or vacuum conditions.

[0033] In some preferred embodiments, the drying temperature in the preparation method of γ-Fe2O3 is 60~120℃, for example 80℃.

[0034] In some preferred embodiments, the drying time in the preparation method of γ-Fe2O3 is 6 to 24 hours, for example 12 hours.

[0035] In the preparation method of γ-Fe2O3, a specific two-stage calcination is used to convert and purify the γ-Fe2O3 phase. The main purpose of the first calcination is to remove bound water and some impurities and to initially form a crystalline phase. The second calcination is crucial, as it can promote the complete transformation of the crystal form into the pure γ-Fe2O3 phase and prevent it from transforming into the more stable α-Fe2O3.

[0036] Thirdly, the present invention provides a photoelectrocatalytic cathode comprising a conductive substrate and a molybdenum single-atom anchored γ-Fe2O3 photoelectrocatheter catalyst as described in the first aspect, supported on the conductive substrate.

[0037] The molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst can be loaded onto the conductive substrate using a conductive binder containing a perfluorosulfonic acid polymer solution.

[0038] In some preferred embodiments, the method for preparing the photoelectrocatalytic cathode includes the following steps:

[0039] S1, Preparation of catalytic slurry:

[0040] Molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst powder was used as the active material, mixed with conductive binder and dispersing solvent, and then physically dispersed to form a uniform and stable catalytic slurry.

[0041] Specifically, step S1 includes:

[0042] Weighing and mixing: Weigh the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst powder, conductive binder, and dispersing solvent according to a ratio of 2 mg:(40~60) μL:(0.8~1.2) mL. Preliminarily mix the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst powder with part or all of the dispersing solvent to obtain a mixture.

[0043] Dispersion treatment: The above mixture is subjected to ultrasonic treatment with an ultrasonic power of 100~500 W and a treatment time of 10~60 minutes until the powder is fully dispersed and a primary suspension is formed.

[0044] Adding binder and homogenization: Add conductive binder to the primary suspension and continue to homogenize by ultrasonication or high-speed mechanical stirring (e.g., 1000~5000 rpm, stirring for 10~30 minutes) to finally obtain a catalytic slurry with uniform texture and no obvious particle agglomeration.

[0045] Optionally, in step S1:

[0046] The conductive adhesive is one or more of the following: perfluorosulfonic acid polymer solution (such as Nafion solution, concentration can be 0.5~10wt%), polytetrafluoroethylene (PTFE) emulsion, polyvinyl alcohol solution, and polyvinylidene fluoride solution, preferably a 5wt% Nafion solution.

[0047] The dispersing solvent is water, alcohol (such as ethanol, isopropanol), or a mixture thereof, preferably a mixture of water and ethanol with a volume ratio of 60:35.

[0048] The mass concentration of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst powder in the catalytic slurry can be 0.5~5 mg / mL, preferably 2~3 mg / mL.

[0049] The ultrasonic treatment can be performed under water bath ultrasound or probe ultrasound conditions.

[0050] The catalytic slurry, after preparation, can be stored under sealed conditions or used immediately.

[0051] S2, the catalytic slurry is coated or dripped onto the surface of a conductive substrate and dried to firmly attach the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst to the conductive substrate, forming a catalytic active layer, thus obtaining the photocathode.

[0052] The conductive substrate is preferably carbon cloth, carbon paper, or metal mesh.

[0053] Catalytic slurry volume: conductive substrate area 0.1~0.5 mL: 1 cm² 2 Preferably, the ratio is 0.25 mL: 1 cm 2 .

[0054] Fourthly, the present invention provides the application of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst described in the first aspect or the photocatalytic cathode described in the third aspect for the photocatalytic degradation of pollutants in water. Further, the pollutants include organic pollutants. Even further, the organic pollutants include antibiotics. Still further, the antibiotics include tetracycline.

[0055] In some preferred embodiments, the application described in the fourth aspect involves placing the photocatalytic cathode as the cathode, a platinum sheet electrode as the counter electrode, and a saturated calomel electrode as the reference electrode in tetracycline wastewater containing electrolytes to carry out a photocatalytic reaction, thereby completing the degradation of the tetracycline wastewater.

[0056] Optionally, the photoelectrocatalytic reaction is carried out under light irradiation, the voltage used in the photoelectrocatalytic reaction is -1.5 to -2.5 V, and the reaction time is 0.5 to 2 h; the electrolyte includes sodium sulfate; the pH value of the tetracycline wastewater is 5.0 to 7.0; the concentration of tetracycline in the tetracycline wastewater is 10 to 20 mg / L, and the electrolyte concentration is 0.2 to 0.3 mol / L.

[0057] This invention employs a co-precipitation-calcination method to prepare a γ-Fe₂O₃ support. A molybdenum precursor is loaded onto the support via impregnation, followed by two-step calcination to stably anchor Mo in single-atom form on the γ-Fe₂O₃ lattice surface. Finally, the resulting catalyst is mixed with a conductive binder to form a slurry, which is then coated onto a conductive substrate to obtain a photoelectrocatalytic cathode. The cathode prepared by this invention, especially the sample with a Mo loading of 27%, exhibits excellent degradation performance, achieving complete degradation of a 10 mg / L tetracycline solution within 20 minutes. This invention provides a novel material and technological approach for the efficient treatment of antibiotic-contaminated wastewater, with clearly defined active sites and a simple preparation method.

[0058] Compared with the prior art, the beneficial effects of this invention are as follows:

[0059] The impregnation-double calcination synthesis method provided by this invention uses readily available raw materials, employs mild process conditions, and is simple to operate. By precisely controlling the precursor concentration, loading, and calcination temperature / atmosphere, ultra-high loading of Mo single atoms is achieved and controllably adjustable within the range of 25%-30%, with the optimal loading point of 27% precisely locked. This method avoids complex equipment and demanding processes, and possesses good repeatability and industrial scale-up potential.

[0060] This invention directly addresses the problem of recalcitrant tetracycline antibiotic pollution in the environment, providing a highly efficient and rapid photoelectrocatalytic degradation solution. The cathode material operates efficiently under simulated sunlight and an applied bias voltage, with low energy consumption and no secondary pollution, offering a green technology option with practical application prospects in the water treatment field.

[0061] The inventors discovered that if other forms of Fe2O3 (such as α-Fe2O3) are used as the support, the photoelectrocatalytic performance of the resulting catalyst will be significantly reduced. Furthermore, when the two-calcination method of this invention is not used, other forms of Fe2O3, such as α-Fe2O3, are easily generated, leading to a significant reduction in the photoelectrocatalytic performance of the catalyst, and / or, Mo cannot be anchored in single-atom form by substituting some iron sites in the γ-Fe2O3 lattice, similarly resulting in a significant reduction in the photoelectrocatalytic performance of the catalyst. Attached Figure Description

[0062] Figure 1X-ray diffraction (XRD) patterns of γ-Fe2O3, 9% Mo@γ-Fe2O3, 18% Mo@γ-Fe2O3, 27% Mo@γ-Fe2O3, 36% Mo@γ-Fe2O3 and 45% Mo@γ-Fe2O3.

[0063] Figure 2 Figure 1 shows the microstructure characterization of 27% Mo@γ-Fe2O3, where (a) is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of 27% Mo@γ-Fe2O3, (b) is a surface intensity distribution map of the selected area (white dashed box) in (a), and (c) is the corresponding structural model.

[0064] Figure 3 Figures show the results of photoelectrocatalytic (PEC) performance testing. Figure (a) shows the photoelectrocatalytic degradation curve of tetracycline under simulated sunlight, Figure (b) shows the corresponding kinetic linear fitting curve, Figure (c) shows the photoelectrocatalytic degradation performance of tetracycline by 27% Mo@γ-Fe2O3 after five consecutive runs, and Figure (d) shows the effect of different trapping agents on the photoelectrocatalytic degradation of tetracycline by 27% Mo@γ-Fe2O3. In Figures (a) and (b), S0, S1, S2, S3, S4 and S5 represent γ-Fe2O3, 9% Mo@γ-Fe2O3, 18% Mo@γ-Fe2O3, 27% Mo@γ-Fe2O3, 36% Mo@γ-Fe2O3 and 45% Mo@γ-Fe2O3, respectively. Detailed Implementation

[0065] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are standard products that can be purchased through conventional market channels.

[0066] Example 1: Preparation of γ-Fe2O3 support:

[0067] Weigh 2.70 g of FeCl3·6H2O and 5.56 g of FeSO4·7H2O, dissolve them in 100 mL of deionized water, and stir magnetically at room temperature until completely dissolved. While continuing to stir, slowly add 1 mol / L NaOH solution dropwise to the mixture until the pH of the solution stabilizes at 9.0. Continue stirring for 2 hours to obtain a dark brown precipitate.

[0068] The resulting precipitate was separated by centrifugation and washed three times with deionized water until the conductivity of the washing solution was close to that of deionized water. The washed precipitate was then dried in an oven at 80°C for 12 hours to obtain the precursor powder.

[0069] The precursor powder was placed in a muffle furnace and calcined at 300°C at a rate of 5°C / min in air for 3 hours. After natural cooling, the powder was transferred to a tube furnace and calcined at 500°C at a rate of 5°C / min in argon for 3 hours. After natural cooling to room temperature, it was ground to obtain a reddish-brown pure-phase γ-Fe₂O₃ catalyst powder (denoted as S₀).

[0070] Example 2: Preparation of 9% Mo@γ-Fe2O3 catalyst:

[0071] Weigh 0.1 g of (NH4)6Mo7O 24 • 4H2O was dissolved in 30 mL of deionized water to prepare an impregnation solution. 1.00 g of the γ-Fe2O3 powder prepared in Example 1 was added to the above impregnation solution, and the mixture was magnetically stirred (800 rpm) in an 80°C water bath for 3 hours, while continuous heating was continued to allow the water to evaporate completely.

[0072] The solid mixture obtained after evaporation was further dried at 80°C for 12 hours. Subsequently, the dried powder was placed in a muffle furnace and calcined at 300°C for 3 hours under an air atmosphere at a rate of 2°C / min. After cooling, the powder was placed in a tube furnace and calcined at 500°C for 3 hours under an argon atmosphere at a rate of 10°C / min. After cooling, the target catalyst 9% Mo@γ-Fe₂O₃ was obtained, denoted as S1, where 9% refers to the molar percentage of Mo to γ-Fe₂O₃, and the same applies below.

[0073] Example 3: Preparation of 18% Mo@γ-Fe2O3 catalyst:

[0074] Except for (NH4)6Mo7O 24 Except for changing the amount of 4H2O to 0.2 g, the other steps are exactly the same as in Example 2. The catalyst 18% Mo@γ-Fe2O3 was obtained, denoted as S2.

[0075] Example 4: Preparation of 27% Mo@γ-Fe2O3 catalyst:

[0076] Except for (NH4)6Mo7O 24 Except for changing the amount of 4H2O to 0.3 g, the other steps were exactly the same as in Example 2. The catalyst 27% Mo@γ-Fe2O3 was obtained and denoted as S3.

[0077] Example 5: Preparation of 36% Mo@γ-Fe2O3 catalyst:

[0078] Except for (NH4)6Mo7O 24 Except for changing the amount of 4H2O to 0.4 g, the other steps were exactly the same as in Example 2. The catalyst 36% Mo@γ-Fe2O3 was obtained, denoted as S4.

[0079] Example 6: Preparation of 45% Mo@γ-Fe2O3 catalyst:

[0080] Except for (NH4)6Mo7O 24 Except for changing the amount of 4H2O to 0.5 g, the other steps were exactly the same as in Example 2. The catalyst 45% Mo@γ-Fe2O3 was obtained and denoted as S5.

[0081] Example 7: Preparation of photoelectrocatalytic cathode:

[0082] Take 2 mg of each of the catalyst powders (S0-S5) prepared in Examples 1 and 2-6, and mix them with 350 μL of anhydrous ethanol, 600 μL of deionized water, and 50 μL of 5 wt% Nafion solution, respectively. Place the mixture in an ultrasonic cleaner and sonicate for 30 minutes to form a uniform reddish-brown catalyst slurry.

[0083] Measure 250 μL of the above slurry using a pipette and evenly drop it onto the surface of a 1 cm × 1.4 cm hydrophilic carbon cloth (ensuring an effective coating area of ​​1 cm × 1 cm). Place the coated electrode in a 60°C oven to dry for 3 hours to obtain the photoelectrocatalytic cathode (working electrode) of the corresponding catalyst.

[0084] XRD tests were performed on the catalysts of Examples 1-6, and the results are as follows: Figure 1 As shown. The diffraction peaks of all samples are consistent with the standard card (JCPDS No. 39-1346) of γ-Fe2O3 with cubic spinel structure. The (311) crystal plane diffraction peaks of samples S1-S3 show a slight shift at a higher angle compared to S0, indicating that Mo species have successfully entered the γ-Fe2O3 lattice, causing lattice shrinkage. When the loading exceeds 27%, such as catalysts S4 and S5, weak impurity peaks belonging to the orthorhombic α-MoO3 (JCPDS No. 73-6497) appear in the XRD pattern, indicating that some Mo exists in the form of nanoclusters or particles.

[0085] The S3 sample from Example 4 was analyzed using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), and the results are as follows: Figure 2 As shown, within the uniformly arranged γ-Fe₂O₃ lattice, scattered bright spots with remarkably high contrast can be observed. Figure 2(as shown by the red dashed circle in (a)). Since the intensity of HAADF imaging is approximately proportional to the square of the atomic number (Z), these bright spots were confirmed to be Mo single atoms with higher atomic numbers. Figure 2 (b) and Figure 2 The intensity distribution map and structural model in (c) further confirm that these Mo atoms are loaded on the γ-Fe2O3 lattice support in a single-atom dispersed form, and are anchored by replacing some iron sites in the γ-Fe2O3 lattice.

[0086] Using the prepared S0-S5 cathode as the working electrode, a degradation experiment was conducted on a tetracycline solution with an initial concentration of 10 mg / L under an applied bias voltage of -1.5 V (relative to the reversible hydrogen electrode, vs. RHE) and simulated sunlight irradiation of 1.5 G. The results are as follows: Figure 3 (a) Figure 3 As shown in (b), the degradation rate of S3 is significantly faster than that of S0. Among them, S3 exhibits the best cathode performance, achieving complete removal of tetracycline in just 20 minutes, with a pseudo-first-order kinetic constant k of 0.299 min. -1 Compared to S0 (k=0.254 min) -1 The stability of the S3 cathode was improved by 17.7%. The stability was tested by conducting five consecutive cyclic degradation experiments, and the results are as follows: Figure 3 As shown in (c), its catalytic activity did not decrease significantly after 5 cycles, indicating that the cathode has good stability. Active species capture experiments were performed on sample S3: the results are as follows... Figure 3 As shown in (d). p-Benzoquinone (capture O2) was added to the reaction system respectively. - ), isopropanol (capture ·OH), EDTA-2Na (capture h) + ) and potassium bromate (capture e) - The results showed that the degradation of tetracycline was severely inhibited after the addition of p-benzoquinone and EDTA-2Na, indicating that O2... - and h + It is the main active species in the degradation process.

[0087] In summary, this invention successfully prepared a series of Mo-modified γ-Fe₂O₃ photocatalytic cathodes via a simple impregnation-two-step calcination method. Among them, the 27% Mo@γ-Fe₂O₃ cathode (S3) exhibited the best photoelectrochemical performance and tetracycline degradation activity. Its superior performance is attributed to the effective modulation of the electronic structure of the support by the Mo single atom, thereby significantly promoting the separation and transport of photogenerated charges. This invention provides a feasible technical solution for designing efficient and stable single-atom catalysts for environmental pollution control.

[0088] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. Use of a molybdenum monatomic-anchored γ-Fe2O3 photoelectrocatalyst for the photoelectrocatalytic degradation of pollutants in aqueous bodies, characterized in that, The molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst comprises a γ-Fe2O3 support and molybdenum atoms anchored in single-atom form on the surface of the γ-Fe2O3 support, wherein the molybdenum atoms are anchored by substituting some iron sites in the γ-Fe2O3 lattice; the contaminants include organic contaminants; the organic contaminants include antibiotics. The preparation method of the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst includes: The molybdenum precursor solution was mixed with γ-Fe2O3 and impregnated and then evaporated to dryness. The resulting solid was calcined twice to obtain the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst. In the two calcinations, the first calcination is carried out in an oxygen-containing atmosphere at 250~350℃, and the second calcination is carried out in an inert atmosphere at 450~550℃.

2. The application according to claim 1, characterized in that, The molar percentage of molybdenum atoms to γ-Fe2O3 in the molybdenum single-atom anchored γ-Fe2O3 photocathode catalyst is 25% to 30%.

3. The application according to claim 1, characterized in that, The molybdenum precursor includes one or more of ammonium molybdate, phosphomolybdic acid, silicomolybdic acid, sodium molybdate, and molybdate chloride. The concentration of the molybdenum precursor in the molybdenum precursor solution is 0.1~0.6 mol / L; The γ-Fe2O3 was added in powder form; The temperature for mixing, impregnation, and evaporation is 60~90℃; The mixing, impregnation, and evaporation are carried out under stirring conditions, with the stirring speed being 300~800 rpm.

4. The application according to claim 1, characterized in that, The first calcination should last for 2 to 5 hours. The second calcination takes 2 to 5 hours.

5. The application according to claim 1 or 4, characterized in that, The preparation method of the γ-Fe2O3 includes: In the presence of a precipitant, ferric salts and ferrous salts undergo a co-precipitation reaction in solution. The precipitate is separated into solid and liquid phases, washed, dried, and calcined twice to obtain γ-Fe2O3.

6. The application according to claim 5, characterized in that, In the preparation method of γ-Fe2O3: The precipitant includes one or more of sodium hydroxide, potassium hydroxide, and ammonia water; The trivalent ferric salt includes one or more of ferric chloride, ferric nitrate, and ferric sulfate; The divalent ferrous salt includes one or more of ferrous sulfate, ferrous chloride, and ferrous nitrate. The molar ratio of ferric iron in the ferric salt to ferrous iron in the ferrous salt is 1:(1.5~2.5); The coprecipitation reaction was carried out at a solution pH of 8-12; The coprecipitation reaction takes 1 to 4 hours; The drying is carried out under normal pressure or vacuum conditions; The drying temperature is 60~120℃; The drying time is 6 to 24 hours.

7. The application according to claim 1, characterized in that, The antibiotics include tetracycline.

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