Nonmetal plasmon heterojunction material, preparation method and application thereof, and method for preparing p-aminophenol through reduction of p-nitrophenol

Abstract

The invention relates to the technical field of photocatalysts, in particular to a nonmetal plasmon heterojunction material, a preparation method and application thereof and a method for preparing p-aminophenol through reduction of p-nitrophenol. The nonmetal plasmon heterojunction material provided by the invention comprises a C3N4 nanosheet and a WO3-x nanoplate (x is 0.1 to 0.3) positioned on the surface of the C3N4 nanosheet. The WO3-x local surface plasmon characteristic can effectively expand the spectral response range of the non-metal plasmon heterojunction material in a visible region to a near-infrared region, and the light absorption efficiency of the non-metal plasmon heterojunction material is remarkably enhanced. The nonmetal plasmon heterojunction material provided by the invention can realize efficient reduction of p-nitrophenol based on the synergistic effect of an interface heterojunction, a built-in electric field and oxygen vacancies, is high in selectivity, has excellent photocatalytic activity for reduction of p-nitrophenol, and is excellent in photocatalytic activity stability.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, specifically to a non-metallic plasmonic heterojunction material, its preparation method and application, and a method for preparing p-aminophenol by reducing p-nitrophenol. Background Technology

[0002] p-Nitrophenol, a typical aromatic nitro compound, exhibits significant biotoxicity, high environmental persistence, and bioaccumulation. On one hand, after being absorbed by organisms, p-nitrophenol has specific toxic effects on the liver and kidneys. On the other hand, the nitro group and phenolic hydroxyl group in the p-nitrophenol molecule contribute to its high chemical stability, making it difficult to decompose effectively under natural conditions, thus resulting in long-term persistence in aquatic and soil environments. Current methods for treating p-nitrophenol mainly include physical adsorption separation technology, chemical oxidation processes, and biodegradation. Adsorption separation technology mainly utilizes the high specific surface area of ​​porous materials such as activated carbon, biochar, or synthetic resins to enrich and transfer p-nitrophenol in the aqueous phase through mechanisms such as van der Waals forces and π-π interactions. While this method can rapidly reduce the concentration of pollutants in water, it does not achieve mineralization degradation. Chemical oxidation processes mineralize p-nitrophenol into carbon dioxide, water, and inorganic ions through electrochemistry and Fenton reactions. This method can fundamentally eliminate its toxicity, but it is relatively complex to operate and not suitable for large-scale application. Biodegradation is an environmentally friendly alternative, but it relies on specific functional microorganisms.

[0003] Reducing p-nitrophenol to the less toxic p-aminophenol, with the conversion product readily degraded by microorganisms in the environment, is a promising strategy for p-nitrophenol removal. For example, photocatalytic reduction of p-nitrophenol utilizes solar energy as a driving force, reducing p-nitrophenol to p-aminophenol at room temperature and pressure, offering advantages such as being green, environmentally friendly, sustainable, and highly efficient. However, the reduction of p-nitrophenol using a single semiconductor catalysis typically requires the additional introduction of NaBH4 as a hole sacrificial agent to suppress electron-hole recombination. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a non-metallic plasmonic heterojunction material, its preparation method and application, and a method for reducing p-nitrophenol to p-aminophenol. The non-metallic plasmonic heterojunction material provided by this invention can be used alone to catalyze the reduction reaction of p-nitrophenol without the need for introducing a hole sacrificial agent, and exhibits high photocatalytic activity.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a nonmetallic plasmonic heterostructure material, comprising C3N4 nanosheets and WO3 nanosheets located on the surface of the C3N4 nanosheets. 3-xNanoplate; the WO 3-x In the nanoplate, x is 0.1~0.3.

[0006] Preferably, in the non-metallic plasmonic heterostructure material, WO3 3-x The mass fraction ranges from 4.4% to 50.9%.

[0007] Preferably, the thickness of the C3N4 nanosheets is 1~5 nm; The WO 3-x The thickness of the nanoplate is 10~40nm.

[0008] This invention also provides a method for preparing the non-metallic plasmonic heterojunction material described in the above technical solution, comprising the following steps: A water-soluble tungstate source, an inorganic strong acid, C3N4 nanosheets, an organic acid, and water are mixed and subjected to acidification hydrolysis and in-situ growth to obtain a precursor, wherein the precursor includes C3N4 nanosheets and WO3 nanoplates grown in situ on the C3N4 nanosheets. The precursor was subjected to thermal reduction treatment in a hydrogen-containing atmosphere to obtain the non-metallic plasmonic heterojunction material.

[0009] Preferably, the molar ratio of the water-soluble tungstate source to the mass of the C3N4 nanosheets is 0.5~1.5 mmol: 0.1~1.6 g; The inorganic strong acid includes one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrobromic acid; The molar ratio of the water-soluble tungstate source to the inorganic strong acid is 0.01~0.03:0.5~4; The organic acid includes one or more of oxalic acid, malonic acid, succinic acid, citric acid, and ethylenediaminetetraacetic acid; The molar ratio of the water-soluble tungstate source to the organic acid is 1:0.5~2.

[0010] Preferably, the acidification hydrolysis and in-situ growth are carried out at a temperature of 70~100℃ for a time of 0.5~3h.

[0011] Preferably, the hydrogen-containing atmosphere comprises a mixture of hydrogen and a protective gas or hydrogen gas, wherein the volume ratio of hydrogen to protective gas in the mixture is 5~10:90~95; and the flow rate of the hydrogen-containing atmosphere is 10~100 mL / min. The thermal reduction treatment is performed at a temperature of 200~500℃ for 1~5 hours.

[0012] This invention also provides the application of the non-metallic plasmonic heterojunction material described in the above technical solution or the non-metallic plasmonic heterojunction material prepared by the above technical solution as a photocatalyst.

[0013] Preferably, the application includes the photocatalytic reduction of p-nitrophenol to prepare p-aminophenol.

[0014] This invention also provides a method for preparing p-aminophenol by reduction of p-nitrophenol, comprising the following steps: mixing a p-nitrophenol solution and a catalyst, and carrying out a reduction reaction under light irradiation to obtain p-aminophenol; wherein the catalyst is the non-metallic plasmon heterojunction material described in the above technical solution or the non-metallic plasmon heterojunction material prepared by the preparation method described in the above technical solution; and the wavelength of the light irradiation is ≥420nm.

[0015] The nonmetallic plasmonic heterojunction material (WO) provided by this invention 3-x C3N4 nanosheets, as an organic semiconductor, possess advantages such as easy availability, good stability, high visible light response, and ease of modification. Their unique electronic structure and suitable band positions enable them to interact with WO3 nanosheets. 3-x Nanoplates construct heterogeneous structures. This invention forms WO3 by introducing abundant oxygen vacancies on the WO3 surface. 3-x This endows it with localized surface plasmon properties, which can effectively extend the spectral response range of non-metallic plasmon heterojunction materials in the visible to near-infrared region and significantly enhance their light absorption efficiency.

[0016] The nonmetallic plasmonic heterojunction material provided by this invention contains WO3 3-x Nanoplatelets and C3N4 nanosheets form a heterostructure. Based on their matched band structure and Fermi level balance, in WO 3-x A built-in electric field is formed at the interface between the nanoplate and the C3N4 nanosheet, which can effectively drive the separation and directional migration of photogenerated electron-hole pairs, thereby significantly suppressing their recombination probability and improving carrier separation efficiency; WO 3-x The formation of a heterostructure with C3N4 significantly improves the separation and migration efficiency of photogenerated carriers. The synergistic effect of the built-in electric field and the heterostructure promotes more efficient migration of electrons and holes to the material surface, enabling them to participate in redox reactions. For example, it can achieve highly efficient and selective reduction of p-nitrophenol when used for the reduction of p-nitrophenol. In non-metallic plasmonic heterostructure materials, WO3... 3-x Abundant oxygen vacancies on the surface and in the bulk endow the catalyst with plasmon properties, significantly enhancing the light absorption capacity of nonmetallic plasmon heterojunction materials; WO 3-xThe interface between the nanoplate and C3N4 nanosheet possesses abundant oxygen vacancies, which can serve as reaction sites and accelerate the redox reaction kinetics. The non-metallic plasmonic heterojunction material provided by this invention, based on the synergistic effect of the interfacial heterojunction, built-in electric field, and oxygen vacancies, can achieve highly efficient reduction of p-nitrophenol without the addition of a hole sacrificial agent, exhibiting high selectivity for p-aminophenol and excellent photocatalytic activity for the reduction of p-nitrophenol to p-aminophenol. Furthermore, the non-metallic plasmonic heterojunction material demonstrates excellent photocatalytic stability.

[0017] WO4 loaded on C3N4 nanosheets 3-x Compared to quantum dot materials, this invention loads WO3 onto C3N4 nanosheets. 3-x Nanoplate, C3N4 and WO 3-x The surface contact forms a two-dimensional / two-dimensional heterostructure with a large contact area and tight interface, resulting in more exposed active sites and a short charge separation path, which is conducive to the effective separation of charge carriers. Non-metallic plasmonic heterojunction materials have high photocatalytic activity and excellent stability.

[0018] Furthermore, this invention controls the amount of WO3 in nonmetallic plasmonic heterostructure materials. 3-x The content of WO3 can be regulated. 3-x The loading ratio and surface oxygen vacancy concentration in non-metallic plasmonic heterojunction materials can optimize the band structure and surface reactivity of the materials, thereby further improving the photocatalytic reduction performance of the materials for p-nitrophenol under visible light irradiation.

[0019] As shown in the test results of the examples, C3N4 nanosheets achieved a 47% removal efficiency of p-nitrophenol within 2 hours, indicating that C3N4 has certain photocatalytic activity; WO3 nanoplatelets showed no significant photocatalytic activity. However, the non-metallic plasmonic heterojunction material provided by this invention achieved a 94% removal rate of p-nitrophenol within 2 hours under visible light irradiation, demonstrating significantly higher photocatalytic activity than C3N4, WO3, WO3 / C3N4, and WO3 nanosheets. 3-x The non-metallic plasmonic heterojunction material provided by this invention does not show a significant decrease in photocatalytic activity after four cycles, indicating that the non-metallic plasmonic heterojunction material provided by this invention has excellent stability.

[0020] This invention uses water-soluble tungstate source, inorganic strong acid, C3N4 nanosheets, and organic acid as raw materials. Through acidification and hydrolysis in an aqueous phase, WO3 nanoplatelets are obtained and grown in situ on the surface of C3N4 nanosheets, constructing a heterostructure. This heterostructure significantly promotes the separation and migration of photogenerated carriers. 3-xA built-in electric field is formed at the interface between the nanoplate and the C3N4 nanosheet, which can effectively promote the separation of photogenerated electron-hole pairs; the synergistic effect of the two promotes the migration of electrons and holes to the material surface to participate in redox reactions. This invention achieves controllable reduction of WO3 by introducing oxygen vacancies into the surface and bulk phase through thermal reduction treatment in a hydrogen-containing atmosphere. 3-x The abundant oxygen vacancies at the C3N4 interface can serve as reaction sites, accelerating the reaction kinetics of p-nitrophenol reduction. The oxygen-vacancy-rich nonmetallic plasmon heterostructure material prepared in this invention exhibits excellent photocatalytic activity for the reduction and removal of p-nitrophenol under the synergistic effect of the heterostructure, built-in electric field, and oxygen vacancies. Furthermore, the preparation method provided by this invention is simple to operate, uses widely available raw materials, has low production costs, is environmentally friendly, and is suitable for industrial production. Attached Figure Description

[0021] Figure 1 SEM images (a), TEM images (b), and HRTEM images (c) of WO3 / C3N4 (denoted as WO / CN) prepared in Example 3, and WO3 / C3N4 prepared in Example 3. 3-x SEM (d), TEM (e), and HRTEM (f) images of / C3N4 (denoted as rWO / CN), where the inset in c is the HRTEM image of the single-component WO3 (denoted as WO) prepared in Comparative Example 1, and the inset in f is the WO prepared in Comparative Example 1. 3-x HRTEM image (denoted as rWO); Figure 2 C3N4 prepared in Example 1, WO3 prepared in Comparative Example 1, and WO3 / C3N4 and WO3 prepared in Example 3. 3-x / C3N4 and WO prepared in Comparative Example 1 3-x XRD pattern (a), FTIR pattern (b), high-resolution N1s energy spectrum (c), and W4f energy spectrum (d); Figure 3 C3N4 prepared in Example 1, WO3 prepared in Comparative Example 1, and WO3 / C3N4 and WO3 prepared in Example 3. 3-x / C3N4 and WO prepared in Comparative Example 1 3-x Electron paramagnetic resonance spectrum (a), absorption spectrum (b), and powder optical pattern (c); X-ray photoelectron spectroscopy valence band spectrum of C3N4 (d); X-ray photoelectron spectroscopy valence band spectrum of WO3 (e); and band structure diagrams of C3N4 and WO3 (f). Figure 4 Thermogravimetric analysis results for CN, WO, 2WO / CN, 1WO / CN, 0.5WO / CN, 0.2WO / CN, and 0.125WO / CN are shown in the figure. Figure 5C3N4 prepared in Example 1, WO prepared in Comparative Example 1, and WO3 / C3N4 (2WO / CN, 1WO / CN, 0.5WO / CN, 0.2WO / CN, and 0.125WO / CN) and WO prepared in the examples. 3-x / C3N4 (0.2 rWO / CN-1h, 0.2 rWO / CN-2h, 0.2 rWO / CN-3h and 0.2 rWO / CN-5h) and WO prepared in Comparative Example 1 3-x The results of the photocatalytic activity test for the conversion of p-nitrophenol are shown in the figure. Figure a shows the photocatalytic activity test results for the reduction of p-nitrophenol using CN, WO, and WO3 / C3N4 with different WO3 contents; Figure b shows the photocatalytic activity test results for the conversion of p-nitrophenol using 0.2 rWO / CN catalyzed by different H2-N2 thermal reduction treatment times; Figure c shows the UV-Vis absorption spectrum of the reduction of p-nitrophenol catalyzed by 0.2 rWO / CN-3h; and Figure d shows the photocatalytic activity test results for C3N4, WO3, 0.2 WO / CN, 0.2 rWO / CN-3h, and WO3 / C3N4. 3-x Activity tests for catalytic conversion of p-nitrophenol; e represents C3N4, WO3, 0.2 WO / CN, 0.2 rWO / CN-3h, and WO 3-x The rate constant for the catalytic conversion of p-nitrophenol; f is the WO3 value. 3-x Cyclic stability test of C3N4; activity test of adding different scavenging agents during the conversion of p-nitrophenol with 0.2 rWO / CN-3h; h and i are C3N4, WO3, 0.2 rWO / CN-3h and WO3, respectively. 3-x Under light, ·OH and ·O2 are produced. ‒ Free radical testing; Figure 6 For the product analysis of the p-nitrophenol conversion reaction, UPLC-MS / MS images of p-nitrophenol are shown in a and b under negative ion mode; and UPLC-MS / MS images of p-aminophenol are shown in c and d under positive ion mode. Detailed Implementation

[0022] This invention provides a nonmetallic plasmonic heterostructure material, comprising C3N4 nanosheets and WO3 nanosheets located on the surface of the C3N4 nanosheets. 3-x Nanoplate; the WO 3-x In the nanoplate, x is 0.1~0.3.

[0023] In this invention, the thickness of the C3N4 nanosheets can be 1-5 nm, or 2-5 nm, specifically 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm; the length and width of the C3N4 nanosheets can independently be 3-10 μm, or 3-5 μm, specifically 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. In this invention, the C3N4 nanosheets provide good support for the loading of WO3 nanoplatelets. As an organic semiconductor, C3N4 nanosheets have advantages such as easy availability, good stability, high visible light response, and ease of modification. Their unique electronic structure and suitable band structure enable them to interact with WO3 nanoplatelets. 3-x Nanoplates construct heterogeneous structures.

[0024] In this invention, the WO 3-x The thickness of the nanoplate can be 10~40nm, or 20~40nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, or 40nm; the WO 3-x The length and width of the nanoplate can be independently 70~200nm, or 100~150nm, specifically 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, and 200nm. The non-metallic plasmonic heterostructure material provided by this invention contains WO₂. 3-x Nanoplates have small size characteristics, which are beneficial to WO 3-x The dispersion and anchoring of WO4 on the C3N4 surface enhances the catalytic activity and stability of the material. In this invention, the WO4... 3-x In the nanoplate, x is 0.1~0.3, and can also be 0.1~0.2, specifically 0.1, 0.15, 0.2, 0.25, or 0.3. This invention forms WO3 by introducing abundant oxygen vacancies onto the WO3 surface. 3-x This endows it with local surface plasmon properties, WO 3-x The exhibited plasmon properties can effectively extend the spectral response range of the material in the visible to near-infrared region and significantly enhance its light absorption efficiency.

[0025] In this invention, WO3 in the non-metallic plasmonic heterostructure material 3-x The mass content can be 4.4%~50.9%, or 10%~40%, specifically 4.4%, 5%, 10%, 14.4%, 15%, 20%, 25%, 27.8%, 30%, 35%, 40%, 44.5%, 50%, or 50.9%. The non-metallic plasmonic heterostructure material WO3 provided by this invention... 3-xThe loading amount and surface oxygen vacancy concentration are systematically adjustable, enabling optimization of the photocatalytic activity of nonmetallic plasmonic heterojunction materials. This invention achieves this by controlling the WO3 loading... 3-x The loading ratio and surface oxygen vacancy concentration in the composite system can optimize the band structure and surface reactivity of the material, ultimately enabling the material to exhibit excellent p-nitrophenol reduction performance under visible light irradiation.

[0026] The nonmetallic plasmonic heterojunction material provided by this invention contains WO3 3-x The band structure matching and Fermi level balancing effect between nanoplates and C3N4 nanosheets in WO 3-x A built-in electric field is formed at the interface between the nanoplate and the C3N4 nanosheet, which can effectively drive the separation and directional migration of photogenerated electron-hole pairs, thereby significantly suppressing their recombination probability and improving carrier separation efficiency; WO 3-x The heterostructure formed with C3N4 significantly improves the separation and migration efficiency of photogenerated carriers. The synergistic effect of the built-in electric field and the heterostructure promotes the more efficient migration of electrons and holes to the material surface, enabling them to participate in redox reactions and achieving highly efficient and selective reduction of p-nitrophenol. In non-metallic plasmonic heterostructure materials, WO3... 3-x Abundant oxygen vacancies on the surface and in the bulk endow the catalyst with plasmon properties, significantly enhancing the light absorption capacity of nonmetallic plasmon heterojunction materials; WO 3-x The interface between the nanoplate and C3N4 nanosheet has abundant oxygen vacancies, which can serve as reaction sites to accelerate the reaction kinetics of p-nitrophenol reduction. The non-metallic plasmon heterojunction material provided by this invention, based on the synergistic effect of the interfacial heterojunction, built-in electric field, and oxygen vacancies, can achieve highly efficient and selective reduction of p-nitrophenol, exhibiting excellent photocatalytic activity for p-nitrophenol reduction with superior stability.

[0027] This invention also provides a method for preparing the non-metallic plasmonic heterojunction material described in the above technical solution, comprising the following steps: A water-soluble tungstate source, an inorganic strong acid, C3N4 nanosheets, an organic acid, and water are mixed and subjected to acidification hydrolysis and in-situ growth. WO3 nanoplates are grown in-situ on the surface of the C3N4 nanosheets to obtain a precursor. The precursor includes C3N4 nanosheets and WO3 nanoplates grown in-situ on the C3N4 nanosheets. The precursor was subjected to thermal reduction treatment in a hydrogen-containing atmosphere to obtain the non-metallic plasmonic heterojunction material.

[0028] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0029] This invention mixes a water-soluble tungstate source, an inorganic strong acid, C3N4 nanosheets, an organic acid, and water, and performs acidification hydrolysis and in-situ growth. WO3 nanoplates are grown in-situ on the surface of the C3N4 nanosheets to obtain a precursor. The precursor includes C3N4 nanosheets and WO3 nanoplates grown in-situ on the C3N4 nanosheets.

[0030] In this invention, the mixing may include: dissolving a water-soluble tungstate source in water to obtain a tungstate source solution; mixing the tungstate source solution with an inorganic strong acid solution; adding a C3N4 nanosheet aqueous dispersion under stirring; heating; and then adding an organic acid and mixing. In this invention, the concentration of the tungstate source solution may be 0.01~0.05 mol / L, or 0.02~0.04 mol / L, or even 0.02~0.03 mol / L. In this invention, the concentration of the inorganic strong acid solution may be 0.5~4 mol / L, or 1~3 mol / L, or even 2 mol / L. In this invention, the concentration of the C3N4 nanosheet aqueous dispersion may be 1~16 g / L, or 2~14 g / L, specifically 1 g / L, 2 g / L, 4 g / L, 6 g / L, 8 g / L, 10 g / L, 142 g / L, 14 g / L, or 16 g / L. In this invention, the temperature after heating can be 70~100℃, or 80~90℃, specifically 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃.

[0031] In this invention, the mass ratio of the water-soluble tungstate source to the C3N4 nanosheets can be 0.5~1.5 mmol:0.1~1.6 g, 1 mmol:0.2~1.5 g, or 0.5 mmol:0.1 g, 0.5 mmol:0.2 g, 0.5 mmol:0.4 g, 0.5 mmol:0.6 g, 0.5 mmol:0.8 g, 0.5 mmol:1 g, 0.5 mmol:1.2 g, or 0.5 mmol:0.5 g. The dosages are 1.4g, 0.5mmol:1.6g, 1mmol:0.1g, 1mmol:0.6g, 1mmol:0.8g, 1mmol:1g, 1mmol:1.2g, 1mmol:1.4g, 1.5mmol:0.1g, 1.5mmol:0.2g, 1.5mmol:0.4g, 1.5mmol:0.8g, 1.5mmol:1g, 1.5mmol:1.4g, or 1.5mmol:1.6g. This invention regulates the loading ratio of WO3 and subsequent oxygen vacancy concentration by controlling the ratio of water-soluble tungstate source and C3N4 nanosheets.

[0032] In this invention, the inorganic strong acid may include one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrobromic acid. In this invention, the molar ratio of the water-soluble tungstate source to the inorganic strong acid may be 0.01~0.03:0.5~4, or 0.02:0.5~4, or further 0.02:1~3, specifically 0.01:0.5, 0.01:1, 0.01:1.5, 0.01:2, 0.01:2.5, 0.01:3, 0.01:3.5, 0.01:4, 0.02:0.5, 0.02:1, 0.02:1.5, 0.02:2.5, 0.02:3.5, 0.03:0.5, 0.03:1, 0.03:2, 0.03:2.5, 0.03:3.5, or 0.03:4.

[0033] In this invention, the organic acid may include one or more of oxalic acid, malonic acid, succinic acid, citric acid, and ethylenediaminetetraacetic acid. In this invention, the molar ratio of the water-soluble tungstate source to the organic acid may be 1:0.5~2, or 1:1~1.5, specifically 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, or 1:2.

[0034] In this invention, the temperature for acidification hydrolysis and in-situ growth can be 70-100℃, or 80-90℃, specifically 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, or 100℃; the time for acidification hydrolysis and in-situ growth can be 0.5-3h, or 1-2h, specifically 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h. This invention uses water-soluble tungstate source, inorganic strong acid, C3N4 nanosheets, and organic acid as raw materials. Acidification hydrolysis occurs in an aqueous phase to obtain WO3 nanoplates, which are then in-situ grown on the surface of C3N4 nanosheets to construct a heterostructure. This heterostructure significantly promotes the separation and migration of photogenerated carriers; WO3... 3-x A built-in electric field is formed at the interface between the nanoplate and the C3N4 nanosheet, which can effectively promote the separation of photogenerated electron-hole pairs; the synergistic effect of the two promotes the migration of electrons and holes to the material surface to participate in redox reactions.

[0035] After completing the acidification hydrolysis and in-situ growth, the present invention may further include: cooling the reaction system obtained from the acidification hydrolysis and in-situ growth to room temperature, performing solid-liquid separation, washing and drying the obtained solid component to obtain the precursor. The present invention does not have specific limitations on the solid-liquid separation; any solid-liquid separation method well-known to those skilled in the art can be used, such as filtration, vacuum filtration, or centrifugation. In the present invention, the centrifugation speed can be 7000~10000 rpm, or 8000~9000 rpm; the centrifugation time can be 8~15 min, or 8~10 min. In the present invention, the washing may include water washing and low-grade alcohol washing, and the number of water washing and low-grade alcohol washing can be independently 2~4 times, or 2~3 times; the low-grade alcohol may include ethanol. In this invention, the drying temperature is 40~70℃, and can also be 50~60℃; the drying time can be 10~36h, and can also be 12~30h, and can further be 12~20h; the drying can include vacuum drying, and the vacuum drying pressure can be -0.07~-0.1MPa, and can also be -0.08~-0.09MPa.

[0036] In this invention, the preparation method of the C3N4 nanosheets may include the following steps: mixing dicyandiamide and ammonium chloride, and carrying out a thermal polymerization reaction to obtain C3N4 nanosheets.

[0037] In this invention, the mass ratio of dicyandiamide to ammonium chloride can be 1:3 to 10, or 1:4 to 8, or even 1:5 to 6.

[0038] In this invention, the temperature of the thermal polymerization reaction can be 500~650℃, or 550~600℃; the heating rate from room temperature to the temperature of the thermal polymerization reaction can be 1~10℃ / min, or 2~8℃ / min, or even 3~5℃ / min; the time of the thermal polymerization reaction can be 3~5h, or 3.5~4.5h, or even 4h.

[0039] After obtaining the precursor, the present invention performs thermal reduction treatment on the precursor in a hydrogen-containing atmosphere to obtain the non-metallic plasmonic heterojunction material.

[0040] In this invention, the hydrogen-containing atmosphere may include a mixture of hydrogen and a carrier gas; the carrier gas may include one or more of nitrogen, argon, and helium, specifically nitrogen; the volume ratio of hydrogen to carrier gas in the mixture may be 5~10:90~95, or 6~9:91~94, or even 7~8:92~93; the flow rate of the hydrogen-containing atmosphere may be 10~100 mL / min, or 20~80 mL / min, specifically 10 mL / min, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, or 100 mL / min.

[0041] In this invention, the temperature of the thermal reduction treatment can be 200~500℃, or 300~400℃, specifically 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, or 500℃; the time of the thermal reduction treatment can be 1~5 hours, or 2~4 hours, and further, 3 hours. This invention achieves controllable reduction of WO3 by introducing oxygen vacancies into the surface and bulk phase through thermal reduction treatment in a hydrogen-containing atmosphere. 3-x The abundant oxygen vacancies at the C3N4 interface can serve as reaction sites, accelerating the reaction kinetics of p-nitrophenol reduction.

[0042] The oxygen-vacancy-rich nonmetallic plasmon heterostructure material prepared by this invention exhibits excellent photocatalytic activity for the reduction and removal of p-nitrophenol under the synergistic effect of the heterostructure, built-in electric field, and oxygen vacancies. Furthermore, the preparation method provided by this invention is simple and easy to operate, uses widely available raw materials, has low production costs, is environmentally friendly, and is suitable for industrial production.

[0043] After completing the thermal reduction treatment, the present invention may further include cooling to room temperature to obtain a non-metallic plasmonic heterojunction material.

[0044] The present invention also provides the application of the non-metallic plasmonic heterojunction material described in the above technical solution or the non-metallic plasmonic heterojunction material prepared by the preparation method described in the above technical solution in the photocatalytic reduction of p-nitrophenol.

[0045] WO3 and WO 3-xThe limited catalytic efficiency exhibited in the reduction of p-nitrophenol is mainly attributed to its significant photogenerated carrier recombination behavior, which severely restricts the number of effective electrons available for surface reduction. This invention, however, constructs a heterostructure and, driven by a built-in electric field, effectively separates photogenerated electron-hole pairs through directional charge migration, thereby achieving highly efficient and selective reduction of nitrophenol. Organic semiconductor C3N4 possesses advantages such as readily available materials, good stability, visible light responsiveness, and ease of modification, and is widely used in photocatalysis. Its unique electronic structure and suitable band positions allow it to form heterostructures with most semiconductors. WO3 not only exhibits good chemical stability, good visible light responsiveness, and strong photo-oxidation ability, but also forms WO3 by introducing abundant oxygen vacancies on its surface. 3-x This can endow it with localized surface plasmon properties. Therefore, by constructing a WO3 / C3N4 heterostructure and introducing abundant oxygen vacancies on its surface, the nonmetallic plasmon heterojunction material facilitates the highly selective conversion of p-nitrophenol to p-aminophenol.

[0046] This invention also provides a method for preparing p-aminophenol by reduction of p-nitrophenol, comprising the following steps: mixing a p-nitrophenol solution and a catalyst, and carrying out a reduction reaction under light irradiation to obtain p-aminophenol; wherein the catalyst is the non-metallic plasmon heterojunction material described in the above technical solution or the non-metallic plasmon heterojunction material prepared by the preparation method described in the above technical solution; and the wavelength of the light irradiation is ≥420nm.

[0047] In this invention, the concentration of the p-nitrophenol solution can be 10-30 ppm, or 15-25 ppm, specifically 20 ppm. In this invention, the volume ratio of the p-nitrophenol solution to the mass ratio of the catalyst can be 1L:0.4g-0.6g, specifically 1L:0.4g, 1L:0.45, 1L:0.5, 1L:0.55, or 1L:0.6g.

[0048] In this invention, the mixing may include ultrasonic mixing, wherein the ultrasonic mixing temperature can be room temperature (18~35℃); the ultrasonic mixing power can be 100~500W, or 100~200W, specifically 100W, 150W, 200W, 250W, 300W, 350W, 400W, 450W, or 500W; the ultrasonic mixing time can be 3~30min, or 3~10min, specifically 3min, 5min, 10min, 15min, 20min, 25min, or 30min. This invention, through ultrasonic mixing, enables the catalyst and p-nitrophenol to be thoroughly and uniformly mixed, effectively preventing catalyst aggregation, maximizing the contact between the catalyst and reactant molecules, and improving catalytic activity.

[0049] In this invention, the wavelength of the illumination is ≥420nm, and can be 420~780nm; in a specific embodiment of this invention, the light source used for the illumination is a 300W xenon lamp equipped with a 420nm cutoff filter; the optical power density of the illumination can be 150~300mW·cm. -2 It can also be 200~250mW·cm -2 Specifically, it can be 150mW·cm -2 180mW·cm -2 200mW·cm -2 220mW·cm -2 250mW·cm -2 280mW·cm -2 Or 300mW·cm -2 .

[0050] In this invention, the temperature of the reduction reaction is room temperature, and the time of the reduction reaction can be 1~3h, or 1.5~2.5h, specifically 2h; the reduction reaction is carried out under stirring conditions, and the stirring speed can be 500~1000r / min, or 600~900r / min, specifically 700~800r / min.

[0051] To further illustrate the present invention, the following detailed descriptions, in conjunction with embodiments, illustrate the non-metallic plasmonic heterojunction materials provided by the present invention, their preparation methods and applications, and the method for preparing p-aminophenol by reduction of p-nitrophenol. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0052] All water used in the experiments was 18.2 MΩ ultrapure water. All raw materials and reagents were of analytical grade. The scanning electron microscope (SEM) was a Quanta 250 FEG FEI. The transmission electron microscope (TEM) was a Tecnai G2 20 (accelerating voltage 200 kV). The X-ray diffractometer was a Bruker D8 Advance. The Fourier transform infrared spectrometer was a Thermo Scientific Nicolet IS5. The high-resolution X-ray photoelectron spectroscopy instrument was an Escalab 250 Xi (Thermo Fisher Scientific). The electron paramagnetic spectroscopy instrument was a Brucker EMXnano spectrometer. The ultraviolet-visible-near-infrared spectrometer was a Hitachi U-4100.

[0053] Example 1 (1) Preparation of C3N4 nanosheets (denoted as CN) Dicyandiamide and ammonium chloride were mixed evenly at a mass ratio of 1:5, spread evenly in a covered crucible, transferred to a muffle furnace, heated to 550℃ at a rate of 3℃ / min, and held at that temperature for 4 hours for thermal polymerization. After cooling to room temperature, C3N4 nanosheets were obtained.

[0054] (2) Preparation of WO3 / C3N4 (denoted as WO / CN) by in-situ growth of WO3 nanoplates on the surface of C3N4 nanosheets Sodium tungstate was dissolved in deionized water to obtain a sodium tungstate solution with a concentration of 5.5 g / L. A 2 mol / L hydrochloric acid solution was added dropwise under stirring, followed by C3N4 nanosheets. Oxalic acid was added at 90 °C, and the reaction proceeded for 1 h. After cooling to room temperature, the mixture was centrifuged at 8000 rpm for 8 min. The resulting solid fraction was washed twice with deionized water and twice with ethanol, and then dried in a vacuum drying oven at 50 °C and -0.07~0.1 MPa for 12 h to obtain WO3 / C3N4 (denoted as 0.2 WO / CN). The ratio of sodium tungstate to hydrochloric acid was 2.75 g:1 mol, the mass ratio of sodium tungstate to C3N4 was 2.75:10, and the mass ratio of sodium tungstate to oxalic acid was 11:3.

[0055] (3) Preparation of WO3 by thermal reduction treatment of H2-N2 mixed gas 3-x / C3N4 (denoted as rWO / CN) WO3 / C3N4 (0.2 WO / CN) was placed in a H2-N2 mixture (H2 volume fraction 5%) at a flow rate of 100 mL / min, heated to 400℃ at a rate of 5℃ / min, and then subjected to thermal reduction treatment for 1 h to obtain WO3. 3-x / C3N4 (denoted as 0.2rWO / CN-1h).

[0056] Examples 2-20 WO was prepared according to the method in Example 1. 3-x / C3N4 differs from Example 1 only in the mass ratio of sodium tungstate to C3N4 in step (3) and the heat reduction treatment time in step (4), as shown in Table 1.

[0057] Table 1. WO in Examples 1-20 3-x Partial preparation conditions of / C3N4

[0058] Comparative Example 1 (1) Preparation of WO3 nanoplates (denoted as WO) WO3 nanoplates were prepared by hydrolysis of sodium tungstate as a precursor in the presence of hydrochloric acid and oxalic acid. The specific steps are as follows: Sodium tungstate was dissolved in deionized water to obtain a sodium tungstate solution with a concentration of 5.5 g / L. A 2 mol / L hydrochloric acid solution was added dropwise under stirring. After adding oxalic acid at 90 °C, the reaction was carried out for 1 h. The solution was cooled to room temperature and centrifuged at 8000 rpm for 8 min. The resulting solid fraction was washed twice with deionized water and twice with ethanol. It was then dried in a vacuum drying oven at 50 °C and -0.07~0.1 MPa for 12 h to obtain WO3 nanoplates (10~40 nm thick, yellow-green powder, see below). Figure 3 (c) In this case, the ratio of sodium tungstate to hydrochloric acid is 2.75 g: 1 mol, and the mass ratio of sodium tungstate to oxalic acid is 11:3.

[0059] (2) Preparation of WO3 by thermal reduction treatment of H2-N2 mixed gas 3-x (denoted as rWO) The WO3 nanoplates were subjected to thermal reduction treatment according to step (3) in Example 1 to obtain WO3 nanoplatelets. 3-x The heat reduction treatment time is 3 hours.

[0060] Comparative Example 2 5g of urea was heated to 550℃ at a rate of 3℃ / min and then thermally polymerized for 3h to obtain bulk C3N4. 0.1g of bulk C3N4 was dispersed in 50mL of ethanol and ultrasonically exfoliated for 8h to obtain C3N4 nanosheets.

[0061] 0.2 g of WCl6 was dissolved in 40 mL of ethanol, and then the mixture was hydrothermally reacted at 180 °C for 12 h. After natural cooling, the mixture was centrifuged, washed, and vacuum dried to constant weight to obtain WO3. 3-x QDs.

[0062] 0.1g WO 3-x QDs and 9.9 g of C3N4 nanosheets were added to a mixed solution of ethanol and water at a volume ratio of 9:1, stirred for 12 h, centrifuged, and the resulting solid component was vacuum dried at 70 °C for 8 h to obtain WO4. 3-x QDs / C3N4 catalyst. This catalyst exhibits a 53% removal efficiency for p-nitrophenol under visible light irradiation (see...). Figure 5 (c)

[0063] Test Example 1 Catalyst structural characterization, wherein the catalysts are C3N4 nanosheets (denoted as CN) and WO3 nanoplates (denoted as WO) prepared in Example 1, WO3 / C3N4 (denoted as WO / CN) prepared in Example 3, and WO3 prepared in Example 3. 3-x / C3N4 (denoted as rWO / CN).

[0064] 1. WO3 / C3N4 and WO 3-x / C3N4 Scanning Electron Microscopy (SEM) Characterization Add 0.5 mg of catalyst (WO3 / C3N4 or WO) 3-x (C3N4) was dispersed in 0.5 mL of deionized water and sonicated for 10 min to obtain a uniform dispersion of catalyst.

[0065] 20 µL of catalyst dispersion was dropped onto the surface of a silicon wafer and allowed to air dry. The surface morphology was characterized by scanning electron microscopy. Figure 1 In Figure a, the image is a SEM image of WO3 / C3N4, which shows that WO3 nanoplatelets are grown relatively uniformly on the surface of C3N4 nanosheets. Figure 1 d is WO 3-x The SEM image of / C3N4 shows that WO3 obtained after H2-N2 thermal reduction treatment... 3-x The morphology of / C3N4 is similar to that of WO3 / C3N4.

[0066] 2. WO3 / C3N4 and WO 3-x Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) characterization of / C3N4 The catalyst dispersion was dropwise added onto a copper grid supported by a carbon film and allowed to air dry. Its microstructure was characterized by transmission electron microscopy. Figure 1 In the image, b is the TEM image of WO3 / C3N4, and e is the TEM image of WO3 / C3N4. 3-x The TEM image of / C3N4 clearly shows WO3 and WO 3-x The nanoplates are tightly bonded together with the C3N4 nanosheets. Figure 1 In the image c, the HRTEM image of WO3 / C3N4 is shown. Combined with the HRTEM image of the WO3 nanoplate in the upper left corner of image c, the complete lattice fringes of the WO3 nanoplate can be seen. Figure 1 The middle f and its illustration are respectively WO 3-x / C3N4 and WO 3-x The HRTEM image of the nanoplatelet shows that after H2-N2 thermal reduction treatment, WO 3-x The disruption of the lattice fringes of the nanoplate indicates the successful introduction of a large number of oxygen vacancies.

[0067] 3. X-ray diffraction (XRD) patterns of CN, WO, WO / CN, rWO / CN, and rWO The catalyst powder was uniformly pressed into a glass groove substrate, and then characterized by powder X-ray diffraction. Figure 2 As shown in Figure a. In the WO3 nanoplate sample, samples were observed located at 13... o and 27 oTypical C3N4 diffraction peaks were observed. After being combined with WO3 nanoplates, in addition to the C3N4 diffraction peaks, characteristic diffraction peaks of WO3·H2O (PDF: 43-0679) were also observed in the WO3 / C3N4 mixture. rWO obtained by thermal reduction treatment of WO3 nanoplates in H2-N2 is WO3. 2.9 (PDF: 18-1417) illustrates that the H2-N2 thermal reduction treatment introduces abundant oxygen vacancies on the WO3 surface. Similarly, after WO3 / C3N4 is reduced in H2-N2, rWO becomes WO3. 2.9 The diffraction peaks of C3N4 did not change significantly, indicating that H2-N2 reduction mainly alters the crystal structure of WO3.

[0068] 4. Fourier transform infrared (FTIR) spectra of CN, WO, WO / CN, rWO / CN, and rWO The catalyst was thoroughly ground and mixed with pre-dried KBr powder (mass ratio 1:200), and then pressed into tablets for Fourier transform infrared spectroscopy testing. Figure 2 As shown in Figure b, vibrational peaks corresponding to the triazine ring and amino group appear in CN, while the main vibrational peaks in WO are stretching vibrations of WO and OH, further confirming the crystal structure of WO3·H2O. Vibrational peaks of both WO3 and C3N4 appear simultaneously in WO / CN, indicating that WO3 has successfully grown on the C3N4 surface. After reduction of the single-component WO, no OH vibrational peak is observed, indicating that the transformation from WO3·H2O to WO... 2.9 The transformation was successful. After H2-N2 thermal reduction treatment, the vibrational peak of CN in rWO / CN did not change significantly. The intensity of the WO bond corresponding to the WO vibrational peak decreased significantly, and the vibrational peak of OH disappeared, further indicating that the H2-N2 thermal reduction treatment mainly caused WO to lose lattice water and generate oxygen vacancies, thus changing the structure of WO.

[0069] 5. High-resolution X-ray photoelectron spectroscopy of CN, WO, WO / CN, rWO / CN, and rWO The catalyst powder was ground uniformly, and its high-resolution X-ray photoelectron spectroscopy was tested. Figure 2 The high-resolution N1s spectrum of CN shows that the signals with binding energies of 398.6 eV, 399.4 eV, 400.8 eV, and 404.2 eV in CN correspond to the NH3 molecules at the edges of the CN=C, N-(C)3, and triazine structures in the CN framework, respectively. x and π-π The satellite peaks. After recombination with WO and rWO, the corresponding peaks shift towards higher binding energies, indicating a decrease in the electron cloud density of CN after recombination. Furthermore, new peaks corresponding to WN bonds were observed in WO / CN and rWO / CN, suggesting that in addition to van der Waals forces, new chemical bonds are formed between WO and CN. Figure 2 In the high-resolution W4f spectra of the composite material, compared with single-component WO and rWO, W 6+ The peak shifts to lower binding energies, indicating that WO and rWO gain electrons while CN loses electrons in this heterostructure. It is noteworthy that the W corresponding to rWO / CN and rWO... 5+ The signal intensity of H2-N2 is significantly higher than that of WO / CN and WO, indicating that H2-N2 introduces abundant oxygen vacancies at the catalyst surface and interface, thereby reducing some of the W content. 6+ Restore to W 5+ .

[0070] 6. Electron paramagnetic resonance spectra of CN, WO, WO / CN, rWO / CN, and rWO Electron paramagnetic spectroscopy characterization of the catalyst powder was performed at room temperature. Catalyst powder with a 1.5 cm depth was poured into a capillary tube (inner diameter: 0.9–1.1 mm) sealed at one end and placed in a sample chamber for testing. When unpaired electrons exist on the catalyst surface or in the crystal lattice, they will appear in its electron paramagnetic spectrum. g = 2.003 signal peak. For example... Figure 3 As shown in Figure a, CN, WO, and WO / CN exhibit weak electron paramagnetic resonance signals without H2-N2 thermal reduction treatment. After H2-N2 thermal reduction treatment, the signals of rWO / CN and rWO are significantly enhanced, indicating the introduction of abundant oxygen vacancies on the catalyst surface. These oxygen vacancy defect sites can serve as active sites for the reaction, facilitating the adsorption of reactant molecules and the catalytic reaction.

[0071] 7. UV-Vis-NIR absorption spectra and powder optical images of CN, WO, WO / CN, rWO / CN, and rWO. The catalyst was uniformly and tightly adhered to the surface of a barium sulfate substrate. Using barium sulfate as a reference, an integrating sphere attachment was installed, and the absorption spectrum of the sample was collected using a UV-Vis-NIR spectrometer, taking into account WO3. 3-x Its plasmon properties allow it to absorb even beyond 800 nm, therefore the absorption spectrum acquisition range was set to 300–1300 nm. For example... Figure 3As shown in Figure b, the absorption cutoff edge of CN is approximately 460 nm. Besides its bandgap absorption, WO also exhibits absorption in the wavelength range greater than 800 nm, indicating that WO also possesses a small number of defects, which is consistent with its high-resolution W4f and electron paramagnetic resonance spectroscopy results. After H2-N2 thermal reduction treatment, the absorption of rWO beyond 800 nm is significantly enhanced, combined with… Figure 3 The powder optical images of medium c further demonstrate that H2-N2 thermal reduction treatment can introduce abundant oxygen vacancies on the catalyst surface. Similarly, the same phenomenon can be observed in WO / CN and rWO / CN, indicating that the light-harvesting ability of rWO / CN is significantly enhanced after H2-N2 thermal reduction treatment, which is conducive to the generation of photogenerated carriers and provides a prerequisite for its efficient catalytic conversion of p-nitrophenol.

[0072] 8. X-ray photoelectron spectroscopy valence band spectra and corresponding band structures of CN and WO The band structure of a catalyst directly determines the migration, separation, and recombination dynamics of photogenerated charge carriers (electrons and holes), and is central to understanding its charge transfer dynamics. For example... Figure 3 As shown in d and e, the valence band spectra of X-ray photoelectron spectroscopy for CN and WO were measured, combined with... Figure 3 The absorption edges in the mid-UV-Vis-NIR absorption spectra of CN and WO were used to determine their band structures. Figure 3 (f). From the schematic diagrams of their band structures, it can be seen that CN and WO easily form a type II heterojunction when in contact. After photoexcitation, CN loses conduction band electrons and WO gains electrons, which is consistent with the high-resolution N1s and W4f spectra.

[0073] 9. Thermogravimetric analysis results for CN, WO, 2WO / CN, 1WO / CN, 0.5WO / CN, 0.2WO / CN, and 0.125WO / CN are shown in [the table below]. Figure 4 It can be seen that the mass percentage of WO in 2WO / CN is 50.9%, the mass percentage of WO in 1WO / CN is 44.5%, the mass percentage of WO in 0.5WO / CN is 27.8%, the mass percentage of WO in 0.2WO / CN is 14.4%, and the mass percentage of WO in 0.125WO / CN is 4.4%.

[0074] Test Example 2 The catalyst structure and composition were characterized, wherein the catalysts were C3N4 nanosheets (denoted as CN) and WO3 nanoplates (denoted as WO) prepared in Example 1, WO3 / C3N4 (2WO / CN, 1WO / CN, 0.5WO / CN, 0.2WO / CN and 0.125WO / CN) prepared in Examples 1-4, and WO3 / C3N4 prepared in Examples 1-4. 3-x / C3N4 (0.2 rWO / CN-1h, 0.2 rWO / CN-2h, 0.2 rWO / CN-3h and 0.2 rWO / CN-5h), WO prepared in Comparative Example 2 3-x QDs / C3N4.

[0075] 1. Activity test of catalyst for the reduction of p-nitrophenol under visible light 25 mg of the prepared catalyst and 50 mL of a 20 ppm p-nitrophenol solution were added to a photocatalytic reactor and dispersed by ultrasonication for 3 min at room temperature and 100 W. The reaction was then carried out at room temperature. A 300 W xenon lamp equipped with a 420 nm cutoff filter was used as the light source. Irradiation was performed from the top while stirring, with a light power density of 250 mW·cm⁻¹. -2 Before turning on the light source, the mixture was stirred in the dark for 1 hour to allow p-nitrophenol to reach adsorption equilibrium. Every 0.5 hours, 1.5 mL of the reaction solution was collected in centrifuge tubes. The initial reaction time was marked as -1.0 h, and subsequent adsorption intervals were marked as -0.5 h. Then, the light source was turned on (recorded as 0.0 h). Every 0.5 h, 1.5 mL of the reaction solution was collected and transferred to centrifuge tubes. After the reaction was complete and all samples were collected, the mixture was centrifuged at 8000 rpm for 10 minutes. The supernatant was then filtered again through a 0.22 µm syringe filter to ensure no catalyst residue remained in the test solution. The illumination time was 2 hours. The filtered supernatant was transferred to a quartz cuvette, and the absorbance of the reaction solution at 320 nm was measured using a UV-Vis spectrophotometer. The absorbance was compared with that of the initial solution to calculate the conversion efficiency of p-nitrophenol. The test results are shown below. Figure 5 And Table 2.

[0076] Table 2. Removal efficiency of p-nitrophenol by different catalysts (after 2 hours of illumination)

[0077] like Figure 5 Figure 'a' shows a comparison of the catalytic efficiency of CN, WO, and different WO / CN loadings for the conversion of p-nitrophenol. Figure 5 As shown in Table 2, CN exhibits good catalytic activity for the conversion of p-nitrophenol, while WO shows no significant photocatalytic activity. The catalytic efficiency of the heterostructure WO / CN obtained after CN-WO composite first increases and then decreases with increasing WO loading. The highest photocatalytic activity is observed when the sodium tungstate:C3N4 mass ratio is 2.75:10 (0.2 WO / CN), catalyzing approximately 70% of the p-nitrophenol conversion within 2 hours. Further, 0.2 WO / CN was treated with H2-N2 to introduce oxygen vacancies at a fixed temperature of 400℃. The oxygen vacancy concentration was controlled by varying the thermal reduction treatment time, which was 1 h, 2 h, 3 h, and 5 h. Figure 5As shown in Figure b, the catalytic efficiency of WO / CN is improved to varying degrees after the introduction of oxygen vacancies.

[0078] The catalytic efficiency of rWO / CN was highest when the H2-N2 treatment time was 3 hours, and it could completely remove 20 ppm of p-nitrophenol solution within 2 hours. Figure 5 c represents the absorption spectrum of p-nitrophenol conversion catalyzed by 0.2 rWO / CN-3h. It can be seen that as the irradiation time increases, the absorption of p-nitrophenol at 320nm gradually decreases. After 2h of irradiation, the absorption of p-nitrophenol at 320nm completely disappears, indicating that p-nitrophenol has been completely converted and removed. Figure 5 The conversion efficiencies of CN, WO, 0.2 WO / CN, 0.2 rWO / CN-3h and rWO catalyzed the conversion of p-nitrophenol were compared. It can be seen that, similar to WO, rWO cannot catalyze the conversion of p-nitrophenol, which may be due to severe carrier recombination or insufficient intermediate reaction species to catalyze the reaction of p-nitrophenol. Figure 5 The rate constants for the conversion of p-nitrophenol catalyzed by CN, WO, 0.2 WO / CN, 0.2 rWO / CN-3h, and rWO were calculated. Linear fitting showed that the catalytic reaction follows first-order kinetics. The reaction rate constant of rWO / CN was the largest, at 1.42 h⁻¹. -1 The stability of the 0.2 rWO / CN-3h catalytic conversion of p-nitrophenol was further tested, such as... Figure 5 As shown in Figure f, after four cycles, the photocatalytic activity did not decrease significantly, indicating that rWO / CN has excellent stability.

[0079] WO3 and WO 3-x The limited catalytic efficiency observed in the reduction of p-nitrophenol is mainly attributed to its significant photogenerated carrier recombination behavior, which severely restricts the number of available electrons for surface reduction. The non-metallic plasmonic heterojunction material obtained by growing WO3 nanosheets on the surface of C3N4 nanosheets showed a significantly improved p-nitrophenol removal rate, indicating that the heterostructure can significantly promote the separation and migration of photogenerated carriers, thus facilitating the migration of electrons and holes to the catalyst surface to participate in the redox reaction. The oxygen-vacancy-rich non-metallic plasmonic heterostructure material exhibited the best photocatalytic activity, with a p-nitrophenol removal rate approaching 94% within 2 hours under visible light irradiation. This demonstrates that the synergistic effect of the heterostructure, built-in electric field, and oxygen vacancies is crucial for enhancing the photocatalytic activity of non-metallic plasmonic heterojunction materials.

[0080] To clarify the reaction species in the 0.2 rWO / CN-3h catalytic conversion of p-nitrophenol, different scavenging agents were added to the reaction solution. p-Benzoquinone (pBQ), AgNO3, tert-butanol (tBA), and ethylene glycol (EG) selectively scavenged superoxide radicals (·O2). ‒ ), electron (e ‒ ), hydroxyl radicals (·OH) and holes (h + ).Depend on Figure 5 As can be seen from the results, the addition of different scavengers inhibited the photocatalytic activity to varying degrees. With the addition of scavengers, the removal efficiency of p-nitrophenol gradually decreased, reaching approximately 5%, 17%, 35%, and 53% upon the addition of AgNO3, pBQ, EG, and tBA, respectively. These results indicate that all four active species participated in the photoconversion process of p-nitrophenol. Notably, the inhibitory effect was most significant in the reaction system with added AgNO3, suggesting that photogenerated electrons play a dominant role in the photocatalytic reaction. Subsequently, EPR spectroscopy was used to detect the ability of the above catalysts to generate hydroxyl radicals and superoxide radicals. Under illumination, all five catalysts exhibited the ability to generate ·OH radicals (…). Figure 5 (h). Among them, the hydroxyl radical signals of WO and rWO samples were slightly higher than those of the other three samples, mainly due to their stronger oxidizing power of valence band holes. However, the contribution of hydroxyl radicals to the removal of p-nitrophenol was not significant. Figure 5 (g). Therefore, although WO and rWO have a high ability to generate hydroxyl radicals, their catalytic performance is still not ideal. The ability of the above catalysts to generate superoxide radicals was further evaluated in methanol solution. Figure 5 As shown in Figure i, due to the strong reducing power of its conduction band electrons, CN, WO / CN, and rWO / CN catalysts can all effectively generate superoxide radicals, while no superoxide radical signal is observed in WO and rWO. Under the synergistic effect of photogenerated electrons, hydroxyl radicals, and superoxide radicals, the rWO / CN heterostructure achieves the highest p-nitrophenol removal efficiency.

[0081] 2. Determination of the products of p-nitrophenol reduction Based on the advantages of rWO / CN in catalyzing the conversion of p-nitrophenol, the reaction products were further characterized and determined. The chemical structures of p-nitrophenol and p-aminophenol in the reaction solution (rWO / CN irradiated for 1 h) were determined using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) in positive and negative ion scanning modes, respectively. Figure 6As shown, UPLC-MS / MS spectra of p-nitrophenol in negative ion mode (a and b) and p-aminophenol in positive ion mode (c and d) indicate that the main products in the reaction solution are p-nitrophenol and p-aminophenol, demonstrating that rWO / CN catalyzes the reduction of nitrophenol to p-aminophenol with high selectivity. Based on the research results of this invention, it is shown that WO 3-x / C3N4 exhibits good catalytic activity and selectivity in the reduction of p-nitrophenol to p-aminophenol.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A non-metallic plasmonic heterostructure material, characterized in that, Includes C3N4 nanosheets and WO3 on the surface of the C3N4 nanosheets. 3-x Nanoplate; the WO 3-x In the nanoplate, x is 0.1~0.

3.

2. The non-metallic plasmonic heterostructure material according to claim 1, characterized in that, The nonmetallic plasmonic heterostructure material contains WO 3-x The mass fraction ranges from 4.4% to 50.9%.

3. The non-metallic plasmonic heterostructure material according to claim 1, characterized in that, The thickness of the C3N4 nanosheets is 1~5nm; The WO 3-x The thickness of the nanoplate is 10~40nm.

4. The method for preparing the nonmetallic plasmonic heterojunction material according to any one of claims 1 to 3, characterized in that, Includes the following steps: A water-soluble tungstate source, an inorganic strong acid, C3N4 nanosheets, an organic acid, and water are mixed and subjected to acidification hydrolysis and in-situ growth to obtain a precursor, wherein the precursor includes C3N4 nanosheets and WO3 nanoplates grown in situ on the C3N4 nanosheets. The precursor was subjected to thermal reduction treatment in a hydrogen-containing atmosphere to obtain the non-metallic plasmonic heterojunction material.

5. The preparation method according to claim 4, characterized in that, The molar ratio of the water-soluble tungstate source to the mass of the C3N4 nanosheets is 0.5~1.5 mmol: 0.1~1.6 g; The inorganic strong acid includes one or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrobromic acid; The molar ratio of the water-soluble tungstate source to the inorganic strong acid is 0.01~0.03:0.5~4; The organic acid includes one or more of oxalic acid, malonic acid, succinic acid, citric acid, and ethylenediaminetetraacetic acid; The molar ratio of the water-soluble tungstate source to the organic acid is 1:0.5~2.

6. The preparation method according to claim 4 or 5, characterized in that, The acidification hydrolysis and in-situ growth are carried out at a temperature of 70~100℃ for a time of 0.5~3h.

7. The preparation method according to claim 4, characterized in that, The hydrogen-containing atmosphere includes a mixture of hydrogen and a protective gas or hydrogen gas, wherein the volume ratio of hydrogen to protective gas in the mixture is 5~10:90~95; and the flow rate of the hydrogen-containing atmosphere is 10~100 mL / min. The thermal reduction treatment is performed at a temperature of 200~500℃ for 1~5 hours.

8. The application of the non-metallic plasmonic heterojunction material according to any one of claims 1 to 3 or the non-metallic plasmonic heterojunction material prepared by the preparation method according to any one of claims 4 to 7 as a photocatalyst.

9. The application according to claim 8, characterized in that, The application includes the photocatalytic reduction of p-nitrophenol to prepare p-aminophenol.

10. A method for preparing p-aminophenol by reduction of p-nitrophenol, characterized in that, Includes the following steps: p-Nitrophenol solution and catalyst are mixed and reduced under light irradiation to obtain p-aminophenol; the catalyst is the non-metallic plasmonic heterojunction material according to any one of claims 1 to 3 or the non-metallic plasmonic heterojunction material prepared by the preparation method according to any one of claims 4 to 7; the wavelength of the light irradiation is ≥420nm.

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