Preparation method and application of Fe2O3 / g-C3N4 composite photocatalytic material

Abstract

The invention discloses a preparation method and application of a Fe2O3 / g-C3N4 composite photocatalytic material, and relates to the technical field of photocatalytic material preparation. The Fe2O3 / g-C3N4 composite photocatalytic material with Fe2O3 uniformly dispersed on the surface of g-C3N4 and strong interface bonding is prepared by a method of performing in-situ crystallization on Fe (OH) 3 colloid on g-C3N4 powder and then performing high-temperature calcination. The preparation method comprises the following steps: calcining urea to obtain g-C3N4 powder; the preparation method comprises the following steps: dropwise adding a FeCl3 solution into boiling water to obtain a Fe (OH) 3 colloidal solution; the g-C3N4 powder is poured into the Fe (OH) 3 colloidal solution, Fe (OH) 3 is adsorbed on the surface of the g-C3N4 powder and crystallized, precipitates are washed, dried and calcined, and the Fe2O3 / g-C3N4 composite photocatalytic material is obtained. The Fe2O3 / g-C3N4 composite photocatalytic material prepared by the preparation method disclosed by the invention can be well adapted to photo-Fenton degradation of different dyes.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic material preparation technology, specifically relating to a method for preparing Fe2O3 / g-C3N4 composite photocatalytic material and its application. Background Technology

[0002] With the acceleration of global industrialization, organic pollutants emitted by industries such as dyeing and printing, and pharmaceuticals pose a serious threat to the water environment. Developing efficient and green pollution control technologies has become a research hotspot in the environmental field. Photocatalysis technology, with its advantages of being solar-powered and producing no secondary pollution, shows broad application prospects in the degradation of organic pollutants. The development of high-performance photocatalytic materials is the core of the industrialization of this technology.

[0003] Graphitic carbon nitride (g-C3N4), as a non-metallic polymer semiconductor, possesses a moderate bandgap (approximately 2.7 eV), excellent chemical and thermal stability, and is abundant in raw materials and inexpensive to prepare, making it an ideal carrier material for photocatalysis. However, g-C3N4 suffers from drawbacks such as rapid recombination of photogenerated carriers, small specific surface area, and a narrow visible light absorption range, resulting in relatively low photocatalytic activity. Ferric oxide (Fe2O3), as a narrow bandgap semiconductor (bandgap of 1.9 to 2.2 eV), can effectively absorb the most abundant visible light region of the solar spectrum and also exhibits Fenton catalytic activity. It can be combined with g-C3N4 to form heterojunctions to synergistically enhance performance. The combination of Fe2O3 and g-C3N4 provides structural complementarity, enabling efficient separation of photogenerated carriers while retaining strong redox capabilities.

[0004] However, the microscopic binding state of g-C3N4 and Fe2O3 affects the photoresponsive activity of the product. g-C3N4 has a stacked lamellar structure, making it difficult for Fe2O3 particles to be uniformly interwoven within it. Secondly, the aggregation of Fe2O3 particles reduces the activity of the product. Simultaneously, side reactions during the preparation process can lead to impurity formation. Furthermore, the dense packing of g-C3N4 itself makes it difficult for Fe2O3 to be uniformly and tightly dispersed on the g-C3N4 lamellars. Therefore, developing a Fe2O3 / g-C3N4 photo-Fenton catalyst that achieves high purity, uniform microscopic particle distribution, and macroscopic overall consistency is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing Fe2O3 / g-C3N4 composite photocatalytic materials and their applications, so as to solve the problems mentioned in the background art.

[0006] To address the problems of uneven Fe2O3 particle dispersion, large particle size, low yield, and poor catalytic degradation performance in existing Fe2O3 / g-C3N4 composite photocatalytic material preparation processes, this invention utilizes a method of in-situ crystallization of Fe(OH)3 colloid on g-C3N4 powder followed by high-temperature calcination to prepare a Fe2O3 / g-C3N4 composite photocatalytic material with uniformly dispersed Fe2O3 and strong interfacial bonding on the g-C3N4 surface. This achieves uniform loading and strong interfacial bonding of Fe2O3 on the g-C3N4 surface, significantly improving product purity and photocatalytic activity, while simplifying the preparation process, reducing production costs, and promoting its large-scale application in water environment treatment.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] Step 1: Preparation of g-C3N4. After drying urea, seal it in a crucible and calcine it. Take out the calcined product and grind it to obtain g-C3N4 powder.

[0009] Step 2: Preparation of Fe(OH)3 colloidal solution. Dissolve FeCl3·6H2O in deionized water to prepare FeCl3 solution. Add the prepared FeCl3 solution dropwise to boiling deionized water. Stop heating when the water turns reddish-brown and allow it to cool naturally to room temperature to obtain Fe(OH)3 colloidal solution.

[0010] Step 3: Preparation of Fe2O3 / g-C3N4 composite photocatalytic material. g-C3N4 powder was moistened with deionized water or ethanol to obtain moist g-C3N4 powder. The moistened g-C3N4 powder was poured into a Fe(OH)3 colloidal solution and stirred immediately. The solution was then treated with ultrasound and stirring, and centrifuged to obtain a precipitate. The precipitate was washed with deionized water and then placed in a vacuum drying oven at 80℃ for 12 hours. The dried solid was sealed in a crucible and calcined. After calcination, it was ground to obtain the Fe2O3 / g-C3N4 composite photocatalytic material.

[0011] Preferably, in step 2, the concentration of the Fe(OH)3 colloidal solution is 0.02 to 0.04 mol / L.

[0012] Preferably, the mass ratio of FeCl3·6H2O used in step 2 to g-C3N4 powder used in step 3 is 1:4.

[0013] Preferably, the ultrasonic and stirring process in step 3 takes 10 to 30 minutes.

[0014] As a preferred embodiment, the calcination process conditions in step 3 are: an initial temperature of 20°C, a heating rate of 2°C / min, heating to 550°C and holding for 4 hours, and then cooling down to 20°C at a cooling rate of 2°C / min.

[0015] The present invention has the following beneficial effects:

[0016] (1) The preparation method of this patent is simple and easy to operate, low in cost, and the raw materials are readily available, and it can achieve large-scale production;

[0017] (2) The present invention achieves highly uniform dispersion and strong interfacial bonding of Fe2O3 nanoparticles on the g-C3N4 substrate by allowing Fe(OH)3 colloid to crystallize in situ on the surface of g-C3N4 powder and then calcining it at high temperature. This effectively inhibits the aggregation of Fe2O3, exposes more active sites on the surface of the catalytic material, and greatly improves the catalytic activity and stability.

[0018] (3) The Fe2O3 and g-C3N4 interface forms an efficient atomic-level electron transport channel, which accelerates the migration of photogenerated electrons from Fe2O3 to g-C3N4, effectively suppresses electron-hole pair recombination, improves charge separation and transport efficiency, and realizes efficient degradation of dyes in water. Attached Figure Description

[0019] Figure 1 This is a TEM image of the Fe2O3 / g-C3N4 composite photocatalytic material of the present invention.

[0020] Figure 2 The ADF-EDS diagrams of the Fe2O3 / g-C3N4 composite photocatalyst material of the present invention are as follows: (a) high-angle annular dark field image; (b) EDS distribution diagram of N element; (c) EDS distribution diagram of Fe element; (d) EDS distribution diagram of C element; (e) EDS distribution diagram of O element.

[0021] Figure 3 The image shows the XRD pattern of the Fe2O3 / g-C3N4 composite photocatalytic material of the present invention.

[0022] Figure 4 XPS spectra of the Fe2O3 / g-C3N4 composite photocatalytic material of the present invention: (a) Fe 2p spectrum; (b) O 1s spectrum.

[0023] Figure 5 The graph shows the degradation effect of the Fe2O3 / g-C3N4 composite photocatalytic material of the present invention on different dyes. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments listed herein are merely illustrative and not intended to limit the scope of the invention. Any obvious modifications or alterations made to this invention do not depart from the spirit and scope of the invention.

[0025] In one embodiment, a method for preparing a Fe2O3 / g-C3N4 composite photocatalytic material includes the following steps:

[0026] Preparation of g-C3N4: Weigh 30g of urea and dry it in a vacuum drying oven at 80℃ for 12 hours. Transfer the dried urea to a 300mL crucible and seal it. Then place the crucible in a muffle furnace for calcination. The specific calcination conditions are as follows: start at an initial temperature of 20℃, heat to 550℃ at a heating rate of 2℃ / min, hold at that temperature for 4 hours, and then cool to 20℃ at a cooling rate of 2℃ / min. After calcination, grind the product to obtain g-C3N4 powder.

[0027] Preparation of Fe(OH)3 colloidal solution: Weigh 0.5 g of FeCl3·6H2O and dissolve it in 0.5 mL of deionized water to prepare a FeCl3 solution. Add 100 mL of deionized water to a 300 mL beaker and heat to boiling, maintaining a gentle boil. Slowly add the prepared FeCl3 solution dropwise to the boiling water, keeping the system at a gentle boil. Once the solution turns reddish-brown, stop heating and allow it to cool naturally to room temperature to obtain the Fe(OH)3 colloidal solution.

[0028] Preparation of Fe2O3 / g-C3N4 composite photocatalytic material: Take 0.2g of g-C3N4 powder prepared in the above steps, add 1mL of deionized water, and grind evenly with an agate mortar to obtain moist g-C3N4 powder. Pour the moist g-C3N4 powder into the Fe(OH)3 colloidal solution obtained in the "Preparation of Fe(OH)3 Colloidal Solution" step, stir immediately for 30s to initially disperse the material, and then continue to treat under the combined conditions of ultrasound and stirring for 20 minutes. Centrifuge to obtain the precipitate. The obtained precipitate is washed with deionized water, and then placed in a vacuum drying oven at 80℃ for 12 hours to obtain the precursor solid. Transfer the precursor solid to a 50mL crucible and seal it, and then place it in a muffle furnace for calcination. The specific calcination process conditions are: starting at an initial temperature of 20℃, heating at a heating rate of 2℃ / min to 550℃ and holding for 4h, and then cooling to 20℃ at a cooling rate of 2℃ / min. After calcination, the product was ground to obtain Fe2O3 / g-C3N4 composite photocatalytic material.

[0029] The Fe2O3 / g-C3N4 composite photocatalytic material prepared in this invention was characterized by TEM, EDS, XRD, and XPS.

[0030] Figure 1 This is a TEM image of the Fe2O3 / g-C3N4 composite photocatalyst material of the present invention. It can be seen that the Fe2O3 / g-C3N4 composite photocatalyst material exhibits a layered structure, which has a large specific surface area.

[0031] Figure 2 Images (a), (b), (c), (d), and (e) are, respectively, high-angle annular dark-field images, N element EDS distribution maps, Fe element EDS distribution maps, C element EDS distribution maps, and O element EDS distribution maps of the Fe2O3 / g-C3N4 composite photocatalyst material prepared in this invention. Figure 2 (b) and Figure 2 The distribution characteristics in (d) show that C and N elements exhibit a highly uniform distribution within the material's spatial range, indicating that the framework structure of g-C3N4 remained intact during the composite process, without significant structural collapse or phase separation. Figure 2 (c) and Figure 2 The distribution characteristics of (e) show that Fe and O elements are uniformly distributed, indicating that Fe2O3 is atomically dispersed and stably loaded on the surface of g-C3N4 support without obvious agglomeration. This significantly increases the density of active sites on the material surface and constructs an efficient electron transport channel between the two phases of Fe2O3 and g-C3N4.

[0032] Figure 3 The image shows the XRD pattern of the Fe2O3 / g-C3N4 composite photocatalyst material of this invention. The 2θ peaks at 13.0° and 27.8° correspond to two typical characteristic peaks of g-C3N4, representing the (100) and (002) crystal planes, respectively. This indicates that the catalytic material prepared in this invention maintains the basic crystal structure of g-C3N4 well. The (100) crystal plane represents the in-plane repeating unit of the carbon nitride heptaazine ring, and the (002) crystal plane represents the interlayer stacking of carbon nitride. The two peaks at 31.3° and 35.5° in the figure represent the (220) and (311) crystal planes of γ-Fe2O3, respectively.

[0033] Figure 4 (a) and (b) are the Fe2p orbital and O1s orbital spectra of the XPS spectra of the Fe2O3 / g-C3N4 composite photocatalyst material prepared in this invention, respectively. Figure 4 The peaks in (a) with binding energies at 710.1 eV and 724.0 eV are attributed to Fe, respectively. 3+ 2p 3 / 2 and 2p 1 / 2The orbits, with corresponding satellite peaks at 718.2 eV and 732.5 eV respectively, clearly confirm that iron in the material is present primarily as Fe. 3+ It exists. In Figure 4 In (b), the peaks with binding energies at 529.0 eV and 531.5 eV correspond to the Fe-O bond in Fe2O3 and the COC bond in the g-C3N4 framework, respectively. Figure 4 (a) and Figure 4 The combined analysis of (b) confirmed that Fe2O3 was successfully generated and loaded onto the g-C3N4 substrate.

[0034] Performance testing of the dye degradation of the Fe2O3 / g-C3N4 composite photocatalytic material prepared in this invention:

[0035] 100 mL of aqueous solutions of Amine Black, Reactive Red, Orange II, and Malachite Green (initial concentration 15 mg / L) were placed in separate 250 mL beakers. 0.075 g of the Fe2O3 / g-C3N4 composite photocatalyst material prepared in the examples and 0.5 mL of a 30% hydrogen peroxide solution were added to each beaker. The mixtures were stirred in the dark for 30 minutes to ensure adsorption-desorption equilibrium was reached. The beakers were then irradiated with a 500 W xenon lamp (filter cut off visible light above 420 nm). Samples were taken every 10 minutes, filtered through a 25 mm diameter, 0.22 μm pore size aqueous filter, and the absorbance at the corresponding dye's maximum absorption wavelength was measured using a UV-Vis spectrophotometer. The dye concentration was calculated using the Lambert-Beer law. Figure 5 After 90 minutes of degradation, the concentrations of amino black decreased to 13%, reactive red to 3%, orange-yellow II to less than 1%, and malachite green to less than 1%. This indicates that the Fe2O3 / g-C3N4 composite photocatalyst material prepared in this invention exhibits strong photo-Fenton catalytic effects on a variety of dyes.

Claims

1. A method for preparing a Fe2O3 / g-C3N4 composite photocatalytic material, characterized in that, Includes the following steps: Step 1, Preparation of g-C3N4: After drying urea, it is sealed in a crucible and calcined. The calcined product is then ground to obtain g-C3N4 powder. Step 2, Preparation of Fe(OH)3 colloidal solution: Dissolve FeCl3·6H2O in deionized water to prepare FeCl3 solution; add FeCl3 solution dropwise to boiling deionized water to obtain Fe(OH)3 colloidal solution; Step 3, Preparation of Fe2O3 / g-C3N4 composite photocatalytic material: After wetting g-C3N4 powder, disperse it in Fe(OH)3 colloidal solution, disperse it by ultrasonication, and centrifuge to obtain precipitate; The precipitate was washed, dried, sealed in a crucible, and calcined. The calcined product was then ground to obtain the Fe2O3 / g-C3N4 composite photocatalytic material.

2. The preparation method of the Fe2O3 / g-C3N4 composite photocatalytic material according to claim 1, characterized in that, In step 2, the concentration of the Fe(OH)3 colloidal solution is between 0.02 and 0.04 mol / L.

3. The preparation method of the Fe2O3 / g-C3N4 composite photocatalytic material according to claim 1, characterized in that, In step 3, the method for wetting the g-C3N4 powder is to wet the g-C3N4 powder with deionized water or anhydrous ethanol.

4. The preparation method of the Fe2O3 / g-C3N4 composite photocatalytic material according to claim 1, characterized in that, In step 3, the mass ratio of g-C3N4 to Fe(OH)3 is 10:1 to 20:

1.

5. The preparation method of the Fe2O3 / g-C3N4 composite photocatalytic material according to claim 1, characterized in that, In step 3, the calcination process conditions are: calcination temperature of 550℃, calcination time of 4h, and heating and cooling rates of 2℃ / min.

6. The application of the Fe2O3 / g-C3N4 composite photocatalyst material prepared by the preparation method of the Fe2O3 / g-C3N4 composite photocatalyst material according to any one of claims 1 to 6 in the photo-Fenton degradation of dye wastewater.

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