Oxygen-enriched three-phase photocatalyst based on super-hydrophobic carbon nitride grid, preparation method and application

Abstract

The invention provides an oxygen-enriched three-phase photocatalyst based on a super-hydrophobic carbon nitride grid and a preparation method and application thereof.The method comprises the steps that porous carbon fiber felt is subjected to multi-stage ultrasonic cleaning to prepare a porous carbon fiber felt substrate, and the carbon nitride grid is prepared through a pyrolysis method; a nitrogen vacancy modified carbon nitride grid is prepared by argon oxygen plasma etching, the gradient grafting donor-acceptor composite material is prepared by combining gas-phase contact modification with liquid-phase photoinduced assembly and gradient thermocompression bonding, a gas-liquid-solid three-phase interface oxygen mass transfer channel is cooperatively constructed, and oxygen-enriched photocatalysis is realized. The gradient grafting donor-acceptor composite material is prepared by combining gas-phase contact modification with liquid-phase photoinduced assembly and a gradient thermocompression bonding process, a firm chemical bonding interface is constructed on the surface of a carbon nitride grid, and the bonding strength of a modification layer and a substrate material is remarkably enhanced; the problem that in the prior art, a modification layer is prone to falling off due to the fact that only physical adsorption or weak chemical action is relied on is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst materials, and in particular relates to an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid, a preparation method and an application thereof. Background Art

[0002] hydrogen peroxide Widely recognized for its versatility and environmental friendliness, hydrogen peroxide plays a key role as an oxidant in diverse industrial processes such as chemical synthesis, water treatment, and energy storage. However, the large-scale production of hydrogen peroxide still relies mainly on the traditional anthraquinone oxidation process, which is accompanied by high energy consumption ( ), multi-stage separation requirements, and inherent safety risks—this catalytic process. Therefore, there is an urgent need to develop an environmentally friendly and reliable strategy for hydrogen peroxide synthesis.

[0003] Recent advances in photocatalyst design, especially the development of efficient materials and optimized reaction systems, have significantly improved So far, a variety of photocatalysts for hydrogen peroxide production have been reported, such as titanium dioxide, zinc oxide, transition metal sulfides, , carbon materials, metal-organic frameworks, covalent organic frameworks, and graphitic carbon nitride (CN). In particular, artificial low-cost CN has become a promising candidate for metal-free photocatalysis due to its superior properties. In addition, the tunable band gap structure (2.7-2.8 eV) is closely related to the The redox potential of the conversion matches that of the CN, and the conjugated system can effectively suppress side reactions and induce selective photocatalysis. Reduction to hydrogen peroxide makes CN a promising photocatalyst for the synthesis of hydrogen peroxide. However, the practical application of natural CN faces two key challenges: (i) insufficient separation efficiency of photogenerated carriers, and (ii) limited exposure of active sites, which affects optimal oxygen adsorption and activation. These inherent limitations have stimulated extensive research on advanced catalyst engineering strategies, including precise structural design, loading of cocatalysts, construction of heterojunctions, doping, and defect engineering. Oxygen / nitrogen groups (e.g., 、 、 )’s CN surface functionalization can precisely tune its surface electronic structure, thereby improving the charge transfer efficiency and activity.

[0004] Most research efforts have focused on the production of , which involves a two-step single-electron ORR pathway ( (-0.33 V relative to standard hydrogen electrode); (1.44 V relative to standard hydrogen electrode)) or a one-step two-electron ORR pathway ( (0.69 V relative to standard hydrogen electrode). In the case of two-electron ORR, oxygen is synthesized Although photocatalysis via ORR is achieved in traditional two-phase (solid-liquid) systems, Significant progress has been made in the production of catalytic products, but inevitable challenges still exist in heterogeneous catalytic systems involving gaseous reactants, such as ORR, RR, NRR. First, the slow surface reaction kinetics is an important factor limiting its performance. In traditional two-phase systems, the oxygen concentration at the interface is limited by the low solubility of oxygen in water (1.3mM) and the slow diffusion rate ( ), which limits the overall catalytic efficiency. In addition, competing side reactions (such as Generate) will reduce selectivity, coupled with the unresolved interfacial charge transfer mechanism.

[0005] Therefore, establishing a three-phase (liquid-solid-gas) system can significantly improve the oxygen mass transfer efficiency by optimizing oxygen utilization.

[0006] As is known to all, the three-phase system has significant advantages: (1) continuous reactant delivery keeps the oxygen concentration at the catalytic interface , which is 6.7 times higher than that of saturated aqueous solution; (2) the mass transfer coefficient is increased by four orders of magnitude ( Compared with the traditional two-phase system); (3) the interfacial double layer promotes the proton-coupled electron transfer kinetics. Currently, the preparation strategy mainly involves fixing the photocatalyst on a hydrophobic porous substrate (e.g., carbon fiber paper, melamine foam, polystyrene microspheres) to establish a stable three-phase boundary. For example, the functionalized carbon nitride / melamine sponge composite material in the prior art is optimized by The COF-coated carbon fiber system achieves simultaneous In addition, the Janus membrane designed in the prior art has asymmetric wettability and can utilize the atmospheric air without ventilation. Together, these studies have improved Oxygen reduction reaction (ORR) efficiency is specifically manifested in: (i) establishing oxygen diffusion channels ( Increased ); (ii) inhibiting hydrogen peroxide decomposition through a confinement effect; and (iii) promoting charge separation through ROS-mediated hole scavenging. However, existing support deposition methods have inherent limitations: (1) reduced accessibility of active sites due to substrate coverage; (2) interfacial delamination leading to long-term stability issues; and (3) limited control over the surface hydrophobicity gradient.

[0007] In the prior art, such as the "Oil-water separation material with photocatalytic self-purification ability, preparation method and application thereof" disclosed in publication number CN117225364A, which achieves oil-water separation and partial photocatalytic functions by coating carbon nitride on carbon fibers and performing surface hydrophobic modification, it still has the following limitations: 1. The surface of the material is modified by vapor phase heat treatment using organic substances such as benzyl alcohol. The modified layer and the substrate mainly rely on physical adsorption or chemical action. It is easy to fall off under long-term use or fluid erosion, resulting in a decrease in hydrophobic performance and affecting its cycle life.

[0008] 2. While this material possesses photocatalytic capabilities, its structure is not optimized for the mass transfer of gaseous reactants (such as oxygen). In traditional two-phase (solid-liquid) systems, oxygen has low solubility and slow diffusion rates, severely limiting its efficiency in oxygen-requiring photocatalytic reactions (such as the photocatalytic synthesis of hydrogen peroxide).

[0009] 3. Although the material has hydrophobic properties, it does not construct a stable gas-liquid-solid three-phase interface, and cannot achieve efficient supply of gaseous oxygen and coordinated interfacial reaction, resulting in limited performance in oxygen-rich catalytic reactions.

[0010] 4. This material does not introduce defect structures such as nitrogen vacancies to enhance the efficiency of photogenerated carrier separation, nor does it construct a gradient electron transport channel. As a result, its photocatalytic activity, especially the selectivity and efficiency of the oxygen reduction reaction (ORR), still needs to be improved.

[0011] In addition, although the existing technology has certain photocatalytic self-cleaning capabilities, its surface modification layer has poor stability and lacks optimized design of oxygen mass transfer and three-phase interface system, especially poor performance in oxygen-rich photocatalytic reactions. Summary of the Invention

[0012] In view of the above situation, the main purpose of the present invention is to propose an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, a preparation method and an application to solve the above technical problems.

[0013] The present invention proposes an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid. The oxygen-rich three-phase photocatalyst consists of a porous carbon fiber felt substrate, a carbon nitride grid, a nitrogen vacancy-modified carbon nitride grid, and a gradient grafted donor-acceptor composite material. The porous carbon fiber felt substrate is prepared by multi-stage ultrasonic cleaning; The carbon nitride grid is prepared by pyrolysis; The nitrogen vacancy modified carbon nitride grid is prepared by argon oxygen plasma etching; The gradient grafted donor-acceptor composite material is prepared by gas phase contact modification combined with liquid phase photoassembly and gradient hot pressing bonding; The porous carbon fiber felt substrate, carbon nitride grid, nitrogen vacancy-modified carbon nitride grid and gradient grafted donor-acceptor composite material synergistically construct an oxygen mass transfer channel at the gas-liquid-solid three-phase interface, realize oxygen-rich photocatalysis, and obtain an oxygen-rich three-phase photocatalyst.

[0014] The present invention proposes a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, which is used to prepare the above-mentioned oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid. The method comprises the following steps: Step 1, immersing the porous carbon fiber felt in acetone solution, ethanol solution and deionized water in sequence, performing ultrasonic cleaning using an ultrasonic cleaning apparatus, and drying in a drying oven after cleaning to obtain a porous carbon fiber felt substrate; Step 2: Mix melamine and urea according to a mass ratio, place the mixture upstream of a tube furnace, place a porous carbon fiber felt substrate in the center of the tube furnace, introduce argon gas to increase the temperature, and then pyrolyze the mixture to obtain a carbon nitride grid material; Step 3: placing the carbon nitride mesh material in a low-temperature plasma reactor and introducing a mixed gas of argon and oxygen to form nitrogen vacancy defects to obtain a nitrogen vacancy-modified carbon nitride mesh material; Step 4: placing the nitrogen vacancy-modified carbon nitride grid material and benzyl alcohol in a closed reactor, and vertically suspending the material above the bottom liquid surface for treatment to obtain a donor-grafted carbon nitride grid material; Step 5: placing the donor-grafted carbon nitride grid material in a closed reactor, adding an ethanol solution containing an aromatic alcohol, and irradiating it with an LED light to obtain a receptor preassembled composite material; The receptor pre-assembled composite material is transferred to a high-pressure reactor, and the gradient temperature is controlled and pulse pressure cycle treatment is performed to obtain a receptor covalently bonded material; The acceptor covalently bonded material is transferred to an ultrasonic cleaning machine and injected with anhydrous ethanol for ultrasonic cleaning. After ultrasonic cleaning, the acceptor is vacuum dried in a vacuum drying oven to obtain a gradient grafted donor-acceptor composite material; Step 6. Place the gradient grafted donor-acceptor composite material in a pulse reactor, alternately introduce high-purity oxygen and nitrogen for circulation treatment, optimize the surface oxygen adsorption configuration and interface mass transfer channel through the pulse gas activation strategy, obtain the treated material, transfer the treated material to a gas-liquid-solid three-phase reaction system, utilize the superhydrophobic properties of the material to maintain a stable gas film, and collaboratively construct the gas-liquid-solid three-phase interface oxygen mass transfer channel to achieve photocatalytic reaction in an oxygen-rich environment and obtain an oxygen-rich three-phase photocatalyst.

[0015] The present invention also proposes an application of an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, which is prepared using the above-mentioned preparation method of an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid. The oxygen-rich three-phase photocatalyst is used to produce hydrogen peroxide.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention prepares a gradient grafted donor-acceptor composite material through gas-phase contact modification combined with liquid-phase photoassembly and gradient hot-pressing bonding technology, constructs a strong chemical bonding interface on the surface of the carbon nitride grid, significantly enhances the bonding strength between the modified layer and the substrate material, and overcomes the problem of easy shedding of the modified layer caused by relying solely on physical adsorption or chemical action in the prior art, thereby ensuring the structural stability and long-term cycle life of the photocatalytic material under long-term use or harsh fluid environments.

[0017] 2. The present invention optimizes the oxygen adsorption configuration on the material surface through a pulse gas activation strategy, and utilizes the super-hydrophobic properties of the prepared material (contact angle up to 172°) to maintain a stable gas film, successfully constructing an efficient gas-liquid-solid three-phase interface oxygen mass transfer channel; this makes gaseous oxygen ( ) can be directly and rapidly transported to the photocatalytic active sites, fundamentally overcoming the technical bottlenecks of low dissolved oxygen concentration and slow diffusion rate in traditional two-phase (solid-liquid) systems, and providing a guarantee for efficient oxygen-rich photocatalytic reactions.

[0018] 3. The present invention introduces nitrogen vacancy defects through argon-oxygen plasma etching, effectively capturing electrons and suppressing electron-hole recombination; at the same time, a directional electron transfer (DA) channel is constructed through gradient grafting, which synergistically optimizes the separation and migration efficiency of carriers; the above synergistic effect not only significantly improves the photocatalytic activity, but also more accurately regulates the oxygen reduction reaction pathway, making the two-electron ORR pathway selectivity as high as more than 70%, effectively suppressing the occurrence of side reactions, and solving the problem of insufficient photocatalytic ORR selectivity and efficiency of existing materials.

[0019] 4. The photoinduced water vapor repair technology adopted in the present invention can effectively inhibit the annihilation of nitrogen vacancy defects during the reaction process. Combined with the enhanced interface strength of gradient hot pressing bonding, it realizes the synergistic optimization of defect stability, mass transfer dynamics and electron transport direction, so that the activity retention rate of the catalyst still exceeds 95% after continuous cycling, and it has excellent long-term operation stability, which solves the contradiction that existing materials are difficult to strike a balance between high-efficiency catalysis and long-term stability.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is the synthetic route of CNDA / CF.

[0022] Figure 2 is the cross-sectional SEM image of CNDA / CF fiber, where a is the cross-sectional SEM image of CNDA / CF fiber, and b is the EDS element mapping of nitrogen.

[0023] Figure 3 Schematic diagram of photocatalytic hydrogen peroxide generation in two-phase and three-phase systems.

[0024] Figure 4 is the contact angle of water on CNDA / CF.

[0025] Figure 5 are the structural characterization diagrams of CN / CF and CNDA / CF, where a is the XRD spectrum, b is the infrared spectrum, c is the XPS fine spectrum, and d is the NMR spectrum.

[0026] Figure 6 These are the characterization diagrams of CN / CF and CNDA / CF, where a is the XPS valence band spectrum of CN / CF and CNDA / CF, and b is the UV-visible absorption spectrum of CN and CNDA powders.

[0027] Figure 7 These are the carrier dynamics characterization diagrams of CN / CF and CNDA / CF, where a is the fluorescence emission spectrum and b is the fluorescence lifetime diagram.

[0028] Figure 8 This is a diagram of a three-phase system photocatalytic hydrogen peroxide production device.

[0029] Figure 9 The photocatalytic hydrogen peroxide production performance diagrams of CN-two-phase, CNDA / CF-two-phase, and CNDA / CF-three-phase are compared and evaluated in pure water according to area and mass. Among them, a is the hydrogen peroxide performance diagram, and b is the CNDA / CF photocatalytic synthesis of hydrogen peroxide cycle experimental diagram.

[0030] Figure 10 Finite element simulation diagrams of the oxygen and hydrogen peroxide concentration distribution at the two-phase and three-phase interfaces, where (a, b) are the diffusion simulations of O2 at the water / catalyst two-phase and O2 / catalyst / water three-phase interfaces, with water as the liquid phase; (c, d) are the diffusion simulations of H2O2 at the two-phase and three-phase interfaces; (e, f) are the oxygen concentration distributions at the (e) two-phase interface and (f) three-phase interface simulated at different oxygen consumption rates.

[0031] Figure 11The obtained CNDA / CF mechanism analysis diagram for hydrogen peroxide production, where a is the performance diagram of CNDA / CF for hydrogen peroxide production under different atmospheres, b is the polarization curve diagram of RRDE, c is the transferred electron number diagram, and d is the selectivity diagram.

[0032] Figure 12 Figure 2 is a characterization diagram of the mechanism analysis of hydrogen peroxide production by CNDA / CF, where a is the performance diagram of hydrogen peroxide production by CNDA / CF under different sacrificial agent conditions, and b is the EPR spectrum of CNDA / CF in the presence of DMPO.

[0033] Figure 13 is the infrared spectrum of CNDA / CF, where a is the in-situ infrared spectrum Figure 1 , b is the in situ infrared spectrum Figure 2 .

[0034] Figure 2 4 is a performance comparison chart of hydrogen peroxide yield of CNDA / CF in Example 4 and CNBA / CF in Comparative Example 1. DETAILED DESCRIPTION

[0035] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0036] These and other aspects of the embodiments of the present invention will become clear with reference to the following description and accompanying drawings. In these descriptions and accompanying drawings, some specific implementations of the embodiments of the present invention are specifically disclosed to illustrate some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0037] Example 1 An oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, the oxygen-rich three-phase photocatalyst comprises a porous carbon fiber felt substrate, a carbon nitride grid, a nitrogen vacancy-modified carbon nitride grid, and a gradient grafted donor-acceptor composite material; The porous carbon fiber felt substrate is prepared by multi-stage ultrasonic cleaning; The carbon nitride grid is prepared by pyrolysis; The nitrogen vacancy modified carbon nitride grid is prepared by argon oxygen plasma etching; The gradient grafted donor-acceptor composite material is prepared by gas phase contact modification combined with liquid phase photoassembly and gradient hot pressing bonding; The porous carbon fiber felt substrate, carbon nitride grid, nitrogen vacancy-modified carbon nitride grid and gradient grafted donor-acceptor composite material synergistically construct an oxygen mass transfer channel at the gas-liquid-solid three-phase interface, realize oxygen-rich photocatalysis, and obtain an oxygen-rich three-phase photocatalyst.

[0038] Example 2 This embodiment provides a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, comprising the following steps: Step 1: 0.5 g / piece of 2 cm × 2 cm × 0.5 cm porous carbon fiber felt was immersed in 80 mL of acetone solution, 80 mL of ethanol solution, and 80 mL of deionized water in sequence, and ultrasonically cleaned using a 35 kHz ultrasonic cleaning apparatus. After cleaning, the porous carbon fiber felt was dried in a 60° C. oven for 3 h to obtain a porous carbon fiber felt substrate, which was recorded as A1. Step 2: 3.0 g of melamine and 6.0 g of urea were mixed in a mass ratio of 1:2, and the mixture was placed upstream of a tube furnace. The porous carbon fiber felt substrate in A1 was placed in the center of the tube furnace, and then argon gas was introduced at a flow rate of 40 sccm and the temperature was increased to 540°C at a heating rate of 5°C / min. After heating, the mixture was pyrolyzed for 3 hours to obtain a carbon nitride grid material, which was recorded as B1. Step 3: The carbon nitride grid material in B1 was placed in a low-temperature plasma reactor at 90W and 40kPa, and a mixture of argon and oxygen with a volume ratio of 3:1 was introduced for 20 minutes to form nitrogen vacancy defects, thereby obtaining a nitrogen vacancy-modified carbon nitride grid material, which was recorded as C1. Step 4: The nitrogen vacancy-modified carbon nitride grid material in C1 and 4.0 mL of benzyl alcohol were placed in a closed reactor at 0.5 MPa, vertically suspended 5 cm above the bottom liquid surface, and the temperature at the bottom of the closed reactor was controlled at 300°C and the temperature at the top of the closed reactor was controlled at 275°C for 1.5 h to obtain a donor-grafted carbon nitride grid material, which was recorded as D1. Step 5: Place the donor-grafted carbon nitride grid material in D1 in a 0.5 MPa closed reactor, add 200 mL of a 0.2 M ethanol solution containing p-nitrobenzyl alcohol, and irradiate the material with an LED light at a light intensity of 90 mW / cm² and a wavelength of 530 nm for 25 minutes to obtain a receptor preassembled composite material; The receptor preassembled composite material was transferred to a high-pressure reactor, the top gradient temperature of the high-pressure reactor was controlled at 275°C, and the bottom gradient temperature of the high-pressure reactor was controlled at 300°C. The high-pressure pulse was subjected to a 0.3 MPa low-pressure pulse and a 0.7 MPa high-pressure pulse cycle for 8 times, with each cycle lasting 1.5 hours, to obtain a receptor covalently bonded material. The acceptor covalently bonded material was transferred to a 35kHz ultrasonic cleaning machine and injected with 200mL of anhydrous ethanol for ultrasonic cleaning for 30min. After ultrasonic cleaning, it was vacuum dried in a vacuum drying oven at 60°C for 2h to obtain a gradient grafted donor-acceptor composite material, which was recorded as E1. Step 6. Place the gradient grafted donor-acceptor composite material in E1 in a 0.7MPa pulse reactor, alternately introduce high-purity oxygen ≥99.99% and nitrogen with a purity ≥99.99% for 8 cycles, with a single alternating introduction time of 4s. Optimize the surface oxygen adsorption configuration and interface mass transfer channel through a pulse gas activation strategy to obtain a treated material, and transfer the treated material to a gas-liquid-solid three-phase reaction system. Utilize the superhydrophobic properties of the material to maintain a stable gas film, and collaboratively construct a gas-liquid-solid three-phase interface oxygen mass transfer channel to achieve a photocatalytic reaction in an oxygen-rich environment, thereby obtaining an oxygen-rich three-phase photocatalyst, recorded as F1.

[0039] Example 3 This embodiment provides a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, comprising the following steps: Step 1: 1.2 g / sheet of 2 cm × 2 cm × 0.5 cm porous carbon fiber felt was immersed in 100 mL of acetone solution, 100 mL of ethanol solution, and 100 mL of deionized water, respectively, and ultrasonically cleaned using a 37.5 kHz ultrasonic cleaning machine. After cleaning, the porous carbon fiber felt substrate was dried in a 65° C. oven for 3.5 h to obtain a porous carbon fiber felt substrate, which was designated as A2. Step 2: 3.5 g of melamine and 7 g of urea were mixed in a mass ratio of 1:2, and the mixture was placed upstream of a tube furnace. The porous carbon fiber felt substrate in A2 was placed in the center of the tube furnace, and then argon gas was introduced at a flow rate of 45 sccm and the temperature was raised to 545°C at a heating rate of 7°C / min. After heating, the mixture was pyrolyzed for 3.25 hours to obtain a carbon nitride grid material, which was recorded as B2. Step 3: The carbon nitride mesh material in B2 was placed in a low-temperature plasma reactor at 95W and a pressure of 45kPa, and a mixed gas of argon and oxygen with a volume ratio of 3.5:1 was introduced for 25 minutes to form nitrogen vacancy defects, thereby obtaining a nitrogen vacancy-modified carbon nitride mesh material, which was recorded as C2. Step 4: The nitrogen vacancy-modified carbon nitride grid material in C2 and 4.5 mL of benzyl alcohol were placed in a closed reactor at 0.55 MPa, vertically suspended 7 cm above the bottom liquid level, and the temperature at the bottom of the closed reactor was controlled at 303°C and the temperature at the top of the closed reactor was controlled at 278°C for 1.7 h to obtain a donor-grafted carbon nitride grid material, which was recorded as D2. Step 5: Place the donor-grafted carbon nitride grid material in D2 in a 0.55 MPa sealed reactor, add 225 mL of a 0.25 M ethanol solution containing p-cyanobenzyl alcohol, and irradiate with an LED light with a light intensity of 95 mW / cm² and a wavelength of 535 nm for 28 minutes to obtain a receptor preassembled composite material; The receptor preassembled composite material was transferred to a high-pressure reactor, the top gradient temperature of the high-pressure reactor was controlled at 278°C, and the bottom gradient temperature of the high-pressure reactor was controlled at 303°C. The high-pressure reactor was subjected to a 0.35 MPa low-pressure pulse and a 0.75 MPa high-pressure pulse cycle for 9 times, with each cycle lasting 1.7 hours, to obtain a receptor covalently bonded material. The acceptor covalently bonded material was transferred to a 38 kHz ultrasonic cleaning machine and injected with 225 mL of anhydrous ethanol for ultrasonic cleaning for 33 min. After ultrasonic cleaning, it was vacuum dried in a vacuum drying oven at 65°C for 2.25 h to obtain a gradient grafted donor-acceptor composite material, which was recorded as E2. Step 6. Place the gradient grafted donor-acceptor composite material in E2 in a 0.75MPa pulse reactor, alternately introduce high-purity oxygen ≥99.99% and nitrogen with a purity ≥99.99% for 9 cycles, with a single alternating introduction time of 4.5s. Optimize the surface oxygen adsorption configuration and interface mass transfer channel through a pulse gas activation strategy to obtain the treated material, and transfer the treated material to a gas-liquid-solid three-phase reaction system. Utilize the superhydrophobic properties of the material to maintain a stable gas film, and collaboratively construct a gas-liquid-solid three-phase interface oxygen mass transfer channel to achieve a photocatalytic reaction in an oxygen-rich environment, thereby obtaining an oxygen-rich three-phase photocatalyst, recorded as F2.

[0040] Example 4 This embodiment provides a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, comprising the following steps: Step 1: 1.5 g / sheet of 2 cm × 2 cm × 0.5 cm porous carbon fiber felt was immersed in 120 mL of acetone solution, 120 mL of ethanol solution, and 120 mL of deionized water, respectively, and ultrasonically cleaned using a 45 kHz ultrasonic cleaning apparatus. After cleaning, the porous carbon fiber felt was dried in an 80° C. oven for 5 h to obtain a porous carbon fiber felt substrate, which was designated as A3. Step 2: 5.0 g of melamine and 10.0 g of urea were mixed in a mass ratio of 1:2, and the mixture was placed upstream of a tube furnace. The porous carbon fiber felt substrate in A3 was placed in the center of the tube furnace, and then argon gas was introduced at a flow rate of 60 sccm and heated to 560°C at a heating rate of 10°C / min. After heating, pyrolysis was performed for 4 hours to obtain a carbon nitride grid material, which was recorded as B3. Step 3: The carbon nitride grid material in B3 was placed in a low-temperature plasma reactor at 110W and a pressure of 60kPa, and a mixture of argon and oxygen with a volume ratio of 3:1 was introduced for 40 minutes to form nitrogen vacancy defects, thereby obtaining a nitrogen vacancy-modified carbon nitride grid material, which was recorded as C3. Step 4: The nitrogen vacancy-modified carbon nitride grid material in C3 and 6.0 mL of benzyl alcohol were placed in a closed reactor at 1.5 MPa, vertically suspended 10 cm above the bottom liquid level, and the temperature at the bottom of the closed reactor was controlled at 310°C and the temperature at the top of the closed reactor was controlled at 285°C for 2.5 hours to obtain a donor-grafted carbon nitride grid material, which was recorded as D3. Step 5: Place the donor-grafted carbon nitride grid material in D3 in a 1.5 MPa closed reactor, add 300 mL of a 0.4 M ethanol solution containing p-nitrobenzyl alcohol, and irradiate the material with an LED light at a light intensity of 110 mW / cm² and a wavelength of 550 nm for 35 minutes to obtain a receptor preassembled composite material; The receptor pre-assembled composite material was transferred to a high-pressure reactor, the top gradient temperature of the high-pressure reactor was controlled at 285°C, and the bottom gradient temperature of the high-pressure reactor was controlled at 310°C. The high-pressure reactor was subjected to 12 cycles of 0.5 MPa low-pressure pulse and 0.9 MPa high-pressure pulse, with each cycle lasting 2.5 hours, to obtain a receptor covalently bonded material. The acceptor covalently bonded material was transferred to a 45kHz ultrasonic cleaning machine and injected with 300mL of anhydrous ethanol for ultrasonic cleaning for 40min. After ultrasonic cleaning, it was vacuum dried in a vacuum drying oven at 80°C for 3h to obtain a gradient grafted donor-acceptor composite material, which was recorded as E3. Step 6. Place the gradient grafted donor-acceptor composite material in E3 in a 0.9MPa pulse reactor, alternately introduce high-purity oxygen ≥99.99% and nitrogen with a purity ≥99.99% for 12 cycles, with a single alternating introduction time of 6s. Optimize the surface oxygen adsorption configuration and interface mass transfer channel through a pulse gas activation strategy to obtain the treated material, and transfer the treated material to a gas-liquid-solid three-phase reaction system. Utilize the superhydrophobic properties of the material to maintain a stable gas film, and collaboratively construct a gas-liquid-solid three-phase interface oxygen mass transfer channel to achieve a photocatalytic reaction in an oxygen-rich environment, thereby obtaining an oxygen-rich three-phase photocatalyst, recorded as F3.

[0041] Comparative Example 1 This embodiment differs from embodiment 4 in that the method includes: S1. Place 0.5 g of urea powder at the bottom of a test tube and place multi-walled carbon nanotubes (single length 5-15 nm) inside the test tube near the tube end (the mass ratio of urea to carbon nanotubes is 1:2); place the test tube in a muffle furnace, heat to 450°C at a heating rate of 2.5°C / min, and maintain at 450°C for 3 hours; then naturally cool to room temperature to obtain a carbon fiber composite material coated with carbon nitride.

[0042] S2. Place 0.5 g of phenylethanol at the bottom of another test tube and place the composite material prepared in step S1 inside the test tube near the tube mouth (the mass ratio of phenylethanol to CN / CF composite material is 1:1). Place the test tube in a tubular muffle furnace under an argon atmosphere and heat to 350°C at a heating rate of 7.5°C / min. Hold at 350°C for 1.5 hours; then cool naturally to room temperature to obtain the phenylethanol-hydrophobically modified CNBA / CF composite material.

[0043] Application Example 1 This embodiment provides an application of an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid. The oxygen-rich three-phase photocatalyst is prepared using the above-mentioned method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid. The oxygen-rich three-phase photocatalyst is applied to produce hydrogen peroxide. The method includes: The oxygen-rich three-phase photocatalyst was placed in a self-designed photocatalytic reactor. Oxygen was continuously introduced into one side of the material to maintain an oxygen-saturated atmosphere, while liquid deionized water flowed into the other side. Visible light irradiation was added to the aqueous phase side. A stable hydrophobic film was seen to form on the surface of the three-phase photocatalyst, and oxygen was continuously supplied from the other side. This greatly improved the mass transfer efficiency of oxygen in the reaction medium, which in turn was beneficial to the activation of the catalyst interface of oxygen and increased the photocatalytic yield of hydrogen peroxide.

[0044] In order to verify the effectiveness of the present invention, an oxygen-rich three-phase photocatalyst (denoted as F3) prepared by the complete process of Example 4 is composed of a porous carbon fiber felt substrate (CF), a carbon nitride grid (CN / CF), a donor-grafted carbon nitride grid material (CND / CF) and a gradient grafted donor-acceptor composite material (CNDA / CF). Figure 3 The synthesis process of the gradient grafted donor-acceptor composite is schematically demonstrated.

[0045] The carbon fiber surface is uniformly coated with a 74.71 nm catalytic layer ( Figure 4 a in the figure), the nitrogen signal is evenly distributed ( Figure 5b), proving that plasma etching did not destroy the integrity of the carbon nitride skeleton, and that nitrogen vacancies were uniformly generated. The orderly generation of nitrogen vacancies is the key prerequisite for selective catalysis. After gradient assembly, there were no cracks at the interface, proving that the gradient temperature process ensured the interlayer bonding strength. This structural integrity is directly related to the improvement of mass transfer efficiency. Three-phase system (right) ( Figure 5 ), the pulse pre-activation layer promotes Diffusion in GDL, mass transfer coefficient increased times ( ), breaking through the dissolved oxygen limitation of the two-phase system (left). This design breaks through the traditional dissolved oxygen limitation and provides a physical basis for efficient photocatalysis.

[0046] The superhydrophobic interface achieves the Cassie-Baxter state, which is attributed to the gradient assembly regulating the spatial distribution of surface functional groups, with a contact angle of 172° ( Figure 5 ), the superhydrophobic property creates the decisive conditions for the maintenance of the air film. The (002) peak shift at 27.9° confirms the enhancement of π-π stacking ( Figure 5 In (a), photoinduced water vapor repair maintains the stability of the vacancy structure, and the half-peak width decreases by 0.15°. This crystal order is closely related to the electron transport performance. Department The vibration peaks prove that benzyl alcohol is grafted ( Figure 6 b); The enhanced breathing mode peak reflects that the gradient assembly improves the order of the heptazine unit, proving that the ordered arrangement at the molecular level directly guides the band structure evolution.

[0047] The CON peak area at 287.2 eV increases ( Figure 6 (c) Pulse pre-activation promotes directional alignment of phenoxy groups, and the ratio of carbon-nitrogen single bonds to carbon-nitrogen double bonds increases from 0.146 to 0.525. This chemical state change is the microscopic evidence of selective adsorption. The new peak of benzene ring C at 30 ppm confirms the gradient assembly ( Figure 7 d in; at 65ppm The chemical shift shift of 2.3 ppm demonstrates donor-acceptor electronic coupling, which is evident in the optoelectronic properties.

[0048] The valence band top increases from 2.16eV (CN) to 2.23eV (CNDA) ( Figure 7 (a) Gradient assembly improves hole migration ability, matches the ORR oxidation potential, and precise control of the energy band position provides thermodynamic guarantee for charge separation. The UV-visible absorption broadens from 471nm of CN to 514nm of CNDA, and the absorption edge is significantly red-shifted ( Figure 8 In b), the broadened light absorption of CNDA is attributed to the introduction of benzyloxy and benzene rings. The fluorescence intensity of CNDA is significantly reduced ( Figure 9Nitrogen vacancies as electron traps suppress The peak blue shift and fluorescence intensity decrease confirm the electron trapping effect of nitrogen vacancies, and the carrier recombination suppression is further verified by the time dimension. The average lifetime of the carriers is reduced from 4.55 ns to 2.76 ns Figure 9 The gradient D-A channel accelerates carrier migration, and the lifetime is reduced to 2.76 ns, which intuitively reflects the electron acceleration effect of the gradient D-A channel. This kinetic optimization plays a key role in three-phase catalysis.

[0049] The superhydrophobic interface in the three-phase system maintains a stable gas film Figure 10 The pulse pre-activation layer (gray) is directly exposed to the gas phase reactant; the stable gas film maintained by the superhydrophobic interface (yellow arrow) is a physical manifestation of three-phase synergy, and the device design enables the pulse pre-activation layer to achieve maximum gas-solid contact efficiency. The three-phase CNDA yield Figure 10 a) is 3 times higher than that of the two-phase system; the 3 times higher three-phase system improvement rate quantifies the mass transfer enhancement effect, and the performance leap needs to be further analyzed in combination with the synthesis methodology; the activity retention rate is >95% after 6 cycles Figure 10 b) Light-induced water vapor repair suppresses nitrogen vacancy annihilation); the 95% activity retention rate is due to the vacancy stabilization mechanism of light repair, which proves that the kinetic analysis reveals the dual advantages of the interface design.

[0050] The rapid oxygen supply of the photocatalytic surface in the three-phase interface, the oxygen diffusion and concentration on the catalytic interface were monitored by finite element simulation. A 500 μm × 500 μm × 1000 μm interface geometry model with a catalytic layer thickness of 1 μm was used Figure 10 a-d). Obviously, due to the slow diffusion of O2 in water, there is an O2 depletion layer with very low O2 concentration near the two-phase catalytic interface Figure 10 a). But due to the rapid gas diffusion pathway, this situation is overcome at the O2 / catalyst / H2O three-phase interface Figure 10 b). For the production of H2O2, it is obvious that the accumulation of H2O2 on the two-phase interface is relatively low Figure 10 c), but more H2O2 on the three-phase interface, due to the rich O2 content on the three-phase catalytic interface, H2O2 shows a clear gradient distribution on the interface Figure 11 d). Considering the dynamic consumption and supply of O2 in the photo-generation process of H2O2, the O2 concentration on the interface under different consumption rates was simulated. The results show that the O2 concentration at the two-phase interface decreases in a dependent manner Figure 11 e). While at the three-phase interface, due to the sufficient oxygen supply in the gas phase, the oxygen concentration remains at a higher level, ensuring that enough oxygen can be provided for the rapid production of hydrogen peroxide​Figure 11 f in ). Yield under atmosphere ( Figure 11 (a) in the figure proves that the pulse pre-activation layer preferentially adsorbs gaseous oxygen; The poor yield under atmosphere proves the key role of gaseous oxygen, and stability becomes the ultimate test for industrial application.

[0051] CNDA has a starting potential of -0.2 V ( Figure 12 (b) The disk current density is 2.1 times higher than that of CN, indicating that pulse pre-activation optimizes the oxygen adsorption configuration; the -0.2V onset potential and 2.1-fold increase in current density demonstrate the advantages of pulse pre-activation, indicating that the electron transfer pathway needs to be quantitatively characterized. Average n = 2.08 (0 to -0.2V) ( Figure 12 In (c), the gradient DA channel ensures that the two-electron ORR path is dominant. Side reactions <10%; n = 2.08 confirms that the two-electron pathway is dominant and that the gradient DA channel inhibits side reactions, a conclusion reinforced by selectivity data. CNDA selectivity >70% (CN only 28%) ( Figure 13 d), nitrogen vacancies promote the end-group adsorption mode, inhibiting bond cleavage; 70% selectivity is attributed to the promotion of the end-group adsorption mode by nitrogen vacancies, and scavenger experiments provide circumstantial evidence for the reaction pathway.

[0052] Add pBQ ( Scavenger) almost no hydrogen peroxide generation ( Figure 13 (a) confirms that the nitrogen vacancy-mediated As the first step reaction; confirming that nitrogen vacancy mediated The first step reaction was generated and the superoxide reactive intermediate was directly observed by spin trapping technology ( Figure 14 b). In-situ infrared test results show that: The peak intensity increases with the increase of illumination time ( ​ a in ​ b); The peak intensity also increases with the increase of illumination time, indicating that as the reaction proceeds, Continuously generated and accumulated on the surface.

[0053] Using the independently designed photocatalytic hydrogen peroxide production device, the yield of hydrogen peroxide produced by CNBA / CF modified with only benzyl alcohol in Comparative Example 1 after 1 hour was , while the yield of hydrogen peroxide produced by CNDA / CF in Example 4 after 1 hour was The performance of CNBA / CF modified with benzyl alcohol to produce hydrogen peroxide is much lower than that of CNDA / CF modified with benzyl alcohol ( ​The material's stability is also poor, with experiments showing that the hydrophobicity of the surface changes within a short period of time. Therefore, the modified CNDA / CF using this technology helps form a stable hydrophobic membrane. The DA modification creates an effective electron transport channel, making it more suitable for constructing a gas-liquid-solid three-phase photocatalytic reaction system, improving oxygen mass transfer efficiency and enhancing ORR selectivity.

[0054] In summary, the present invention effectively enhances oxygen diffusion and activation capabilities, significantly improves hydrogen peroxide generation efficiency, and greatly enhances catalytic stability by constructing gas-liquid-solid interface mass transfer channels, regulating nitrogen vacancy structures and gradient electron transport networks. This breaks through the technical bottleneck of the coordinated optimization of mass transfer and activity in traditional photocatalytic systems, providing an efficient solution for green synthesis and pollution control.

[0055] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0056] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, characterized in that: The method comprises the following steps: Step 1, immersing the porous carbon fiber felt in acetone solution, ethanol solution and deionized water in sequence, performing ultrasonic cleaning using an ultrasonic cleaning apparatus, and drying in a drying oven after cleaning to obtain a porous carbon fiber felt substrate; Step 2: Mix melamine and urea according to a mass ratio, place the mixture upstream of a tube furnace, place a porous carbon fiber felt substrate in the center of the tube furnace, introduce argon gas to increase the temperature, and then pyrolyze the mixture to obtain a carbon nitride grid material; Step 3: placing the carbon nitride mesh material in a low-temperature plasma reactor and introducing a mixed gas of argon and oxygen to form nitrogen vacancy defects to obtain a nitrogen vacancy-modified carbon nitride mesh material; Step 4: placing the nitrogen vacancy-modified carbon nitride grid material and benzyl alcohol in a closed reactor, and vertically suspending the material above the bottom liquid surface for treatment to obtain a donor-grafted carbon nitride grid material; Step 5: placing the donor-grafted carbon nitride grid material in a closed reactor, adding an ethanol solution containing an aromatic alcohol, and irradiating it with an LED light to obtain a receptor preassembled composite material; The receptor pre-assembled composite material is transferred to a high-pressure reactor, and the gradient temperature is controlled and low-pressure pulse and high-pressure pulse cycle treatment is performed to obtain a receptor covalently bonded material; The acceptor covalently bonded material is transferred to an ultrasonic cleaning machine and injected with anhydrous ethanol for ultrasonic cleaning. After ultrasonic cleaning, the acceptor is vacuum dried in a vacuum drying oven to obtain a gradient grafted donor-acceptor composite material; Step 6. Place the gradient grafted donor-acceptor composite material in a pulse reactor, alternately introduce oxygen and nitrogen for circulation treatment, optimize the surface oxygen adsorption configuration and interface mass transfer channel through the pulse gas activation strategy, obtain the treated material, transfer the treated material to a gas-liquid-solid three-phase reaction system, utilize the superhydrophobic properties of the material to maintain a stable gas film, and collaboratively construct the gas-liquid-solid three-phase interface oxygen mass transfer channel to achieve photocatalytic reaction in an oxygen-rich environment and obtain an oxygen-rich three-phase photocatalyst.

2. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 1, wherein: In step 1, in the process of obtaining the porous carbon fiber felt substrate, the size of the porous carbon fiber felt is 2 cm × 2 cm × 0.5 cm, the mass of the porous carbon fiber felt is 0.5-1.5 g / piece, the volume of the acetone solution is 80-120 mL, the volume of the ethanol solution is 80-120 mL, the volume of the deionized water is 80-120 mL, the frequency of the ultrasonic cleaning machine is 35-45 kHz, the temperature of the drying oven is 60-80 ° C, and the drying time is 3-5 h.

3. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 1, wherein: In step 2, in the process of obtaining the carbon nitride grid material, the mass of melamine is 3.0-5.0 g, the mass of urea is 6.0-10.0 g, the mixing mass ratio of melamine to urea is 1:2, the argon flow rate is 40-60 sccm, the pyrolysis heating rate is 5-10°C / min, the pyrolysis temperature is 540-560°C, and the pyrolysis time is 3-4h.

4. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 1, wherein: In step 3, in the process of obtaining the nitrogen vacancy modified carbon nitride grid material, the power of the low-temperature plasma reactor is 90-110 W, the gas pressure of the low-temperature plasma reactor is 40-60 kPa, the flow rate of the mixed gas of argon and oxygen is 40-60 sccm, the volume ratio of the mixed gas of argon and oxygen introduced is 3:1 to 5:1, and the treatment time of the mixed gas of argon and oxygen introduced is 20-40 min.

5. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 1, wherein: In step 4, in the process of obtaining the donor-grafted carbon nitride grid material, the volume of benzyl alcohol is 4.0-6.0 mL, vertically suspended 5-10 cm above the bottom liquid surface, the bottom temperature of the closed reactor is 300-310° C., the top temperature of the closed reactor is 275-285° C., the pressure of the closed reactor is 0.5-1.5 MPa, and the treatment time vertically suspended above the bottom liquid surface is 1.5-2.5 h.

6. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 1, wherein: In step 5, during the process of obtaining the receptor preassembled composite material, the pressure of the closed reactor is 0.5-1.5 MPa, the concentration of the ethanol solution containing the aromatic alcohol is 0.2-0.4 M, the volume of the ethanol solution containing the aromatic alcohol is 200-300 mL, the concentration of the ethanol solution containing the aromatic alcohol is 0.2-0.4 M, the light intensity of the LED lamp is 90-110 mW / cm², the LED lamp irradiation time is 25-35 minutes, and the wavelength of the LED lamp is 530-550 nm; In the process of obtaining the receptor covalently bonded material, the top gradient temperature of the high-pressure reactor is controlled at 275-285°C, the bottom gradient temperature of the high-pressure reactor is controlled at 300-310°C, the low-pressure pulse pressure is 0.3-0.5 MPa, the high-pressure pulse pressure is 0.7-0.9 MPa, the number of cycle treatments is 8-12 times, and the duration of each cycle treatment is 1.5-2.5 hours; In the process of obtaining the gradient grafted donor-acceptor composite material, the frequency of the ultrasonic cleaning machine is 35-45kHz, the volume of the injected anhydrous ethanol is 200-300mL, the ultrasonic treatment time is 30-40min, the vacuum drying oven temperature is 60-80℃, and the vacuum drying time is 2-3h.

7. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 6, characterized in that: The aromatic alcohol is one of p-nitrobenzyl alcohol, p-cyanobenzyl alcohol and p-trifluoromethylbenzyl alcohol.

8. The method for preparing an oxygen-rich three-phase photocatalyst based on a super-hydrophobic carbon nitride grid according to claim 1, wherein: In step 6, in the process of obtaining the oxygen-rich three-phase photocatalyst, the pressure of the pulse reactor is 0.7-0.9 MPa, the purity of the alternately introduced oxygen is ≥99.99%, the purity of the nitrogen is ≥99.99%, the single alternating introduction time is 4-6 s, and the number of cycles is 8-12 times.

9. An oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, characterized in that: The method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid according to any one of claims 1 to 8 is used, wherein the oxygen-rich three-phase photocatalyst is composed of a porous carbon fiber felt substrate, a carbon nitride grid, a nitrogen vacancy-modified carbon nitride grid, and a gradient grafted donor-acceptor composite material; The porous carbon fiber felt substrate is prepared by multi-stage ultrasonic cleaning; The carbon nitride grid is prepared by pyrolysis; The nitrogen vacancy modified carbon nitride grid is prepared by argon oxygen plasma etching; The gradient grafted donor-acceptor composite material is prepared by gas phase contact modification combined with liquid phase photoassembly and gradient hot pressing bonding; The porous carbon fiber felt substrate, carbon nitride grid, nitrogen vacancy-modified carbon nitride grid and gradient grafted donor-acceptor composite material synergistically construct an oxygen mass transfer channel at the gas-liquid-solid three-phase interface, realize oxygen-rich photocatalysis, and obtain an oxygen-rich three-phase photocatalyst.

10. An application of an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, using the oxygen-rich three-phase photocatalyst according to claim 9, characterized in that: The oxygen-rich three-phase photocatalyst is used to produce hydrogen peroxide.

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