Oxygen-enriched three-phase photocatalysts based on superhydrophobic carbon nitride meshes, preparation methods and applications

Abstract

This invention proposes an oxygen-enriched three-phase photocatalyst based on a superhydrophobic carbon nitride mesh, its preparation method, and its application. The method involves preparing a porous carbon fiber felt substrate through multi-stage ultrasonic cleaning, obtaining a carbon nitride mesh via pyrolysis, and then preparing a nitrogen-vacancy-modified carbon nitride mesh using argon-oxygen plasma etching. A gradient-grafted donor-acceptor composite material is prepared through gas-phase contact modification combined with liquid-phase photolithography and gradient thermopressing bonding, synergistically constructing an oxygen mass transfer channel at the gas-liquid-solid three-phase interface to achieve oxygen-enriched photocatalysis. This invention prepares the gradient-grafted donor-acceptor composite material through gas-phase contact modification combined with liquid-phase photolithography and gradient thermopressing bonding processes, constructing a robust chemical bonding interface on the carbon nitride mesh surface. This significantly enhances the bonding strength between the modified layer and the substrate material, overcoming the problem of easy detachment of the modified layer caused by relying solely on physical adsorption or weak chemical interactions in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of catalyst materials technology, and specifically relates to an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, its preparation method, and its application. Background Technology

[0002] hydrogen peroxide Hydrogen peroxide is widely recognized for its versatility and environmental friendliness, playing a crucial role as an oxidant in diverse industrial processes such as chemical synthesis, water treatment, and energy storage. However, large-scale production of hydrogen peroxide still primarily relies on traditional anthraquinone oxidation processes, which are characterized by high energy consumption. The catalytic process presents challenges due to its multi-stage separation requirements and inherent safety risks. Therefore, there is an urgent need to develop an environmentally friendly and reliable strategy for hydrogen peroxide synthesis.

[0003] Recent advances in photocatalyst design, particularly the development of high-efficiency materials and optimized reaction systems, have significantly improved... Production efficiency and selectivity. To date, various photocatalysts for hydrogen peroxide production have been reported, such as titanium dioxide, zinc oxide, transition metal sulfides, etc. Carbon materials, metal-organic frameworks, covalent organic frameworks, and graphitic carbon nitride (CN) are among the promising candidates for metal-free photocatalysis, particularly due to their superior properties. Furthermore, tunable bandgap structures (2.7–2.8 eV) and... The matching of redox potentials during conversion, along with the conjugated system of CN, can effectively suppress side reactions and induce selective photocatalysis. The reduction of CN to hydrogen peroxide makes CN a promising photocatalyst for hydrogen peroxide synthesis. However, the practical application of natural CN faces two key challenges: (i) insufficient photogenerated carrier separation efficiency, and (ii) limited exposure of active sites, affecting optimal oxygen adsorption and activation. These inherent limitations have spurred extensive research into advanced catalyst engineering strategies, including precise structural design, supported cocatalysts, heterojunction construction, doping, and defect engineering. Oxygen / nitrogen-containing groups (e.g., , , Functionalization of the CN surface can precisely tune its surface electronic structure, thereby improving charge transfer efficiency and activity.

[0004] Most research focuses on the production of oxygen via the two-electron oxygen reduction reaction (ORR) pathway. This approach involves a two-step single-electron ORR pathway ( (Relative to the standard hydrogen electrode -0.33V); (relative to the standard hydrogen electrode 1.44V) or a one-step two-electron ORR path ( (Relative to the standard hydrogen electrode 0.69V). Under the two-electron ORR condition, oxygen is synthesized... It plays a crucial role. Although photocatalysis is achieved via ORR in traditional two-phase (solid-liquid) systems... Significant progress has been made in production, but unavoidable challenges remain in heterogeneous catalytic systems involving gaseous reactants, such as ORR. RR, NRR. First, the slow surface reaction kinetics are a significant factor limiting its performance. In traditional two-phase systems, the oxygen concentration at the interface is affected by the low solubility of oxygen in water (1.3 mM) and the slow diffusion rate ( The limitations imposed by this factor restrict the overall catalytic efficiency. Furthermore, competing side reactions (such as...) (Generation) will decrease The selectivity of the interface charge transfer mechanism is further complicated by the unresolved issue.

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

[0006] As is well known, three-phase systems have significant advantages: (1) continuous reactant delivery maintains the oxygen concentration at the catalytic interface at a certain level. (1) The mass transfer coefficient was increased by 6.7 times compared to saturated aqueous solution; (2) The mass transfer coefficient was increased by four orders of magnitude. Compared with traditional two-phase systems); (3) the interfacial double layer promotes proton-coupled electron transfer dynamics. 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 carbonitride / melamine sponge composite material in the prior art has been optimized The hydrogen peroxide yield of the COF-coated carbon fiber system is 10 times higher than that of the two-phase material. Furthermore, the COF-coated carbon fiber system achieves simultaneous... It is enriched and stabilized with hydrogen peroxide. Furthermore, the Janus membranes designed in the prior art exhibit asymmetric wettability, enabling the utilization of atmospheric hydrogen peroxide even without aeration. These studies collectively improved The efficiency of the oxygen reduction reaction (ORR) is specifically reflected in: (i) the establishment of oxygen diffusion channels ( Increased (ii) inhibiting hydrogen peroxide decomposition through the confinement effect; (iii) promoting charge separation through ROS-mediated hole removal. However, existing carrier deposition methods have inherent limitations: (1) reduced accessibility of active sites due to matrix coverage; (2) long-term stability problems caused by interfacial delamination; and (3) limited control over surface hydrophobicity gradients.

[0007] In the prior art, such as the "An oil-water separation material with photocatalytic self-purification ability and its preparation method and application" disclosed in CN117225364A, oil-water separation and partial photocatalytic function are achieved by coating carbon fibers with carbon nitride and modifying the surface with hydrophobicity. However, the following limitations still exist:

[0008] 1. This material is surface-modified by organic substances such as benzyl alcohol through gas-phase heat treatment. The relationship between the modified layer and the substrate mainly relies on physical adsorption or chemical action. Under long-term use or fluid erosion, it is prone to peeling off, resulting in a decrease in hydrophobic properties and affecting its cycle life.

[0009] 2. Although this material possesses photocatalytic capabilities, its structure has not been optimized for mass transfer of gaseous reactants (such as oxygen). In traditional two-phase (solid-liquid) systems, oxygen has low solubility and slow diffusion rate, which severely limits its efficiency in aerobic photocatalytic reactions (such as photocatalytic synthesis of hydrogen peroxide).

[0010] 3. Although the material has hydrophobic properties, it does not form a stable gas-liquid-solid three-phase interface, which prevents the efficient supply of gaseous oxygen and synergistic interfacial reactions, thus limiting its performance in oxygen-enriched catalytic reactions.

[0011] 4. The material does not introduce defect structures such as nitrogen vacancies to enhance the separation efficiency of photogenerated carriers, nor does it construct gradient electron transport channels, resulting in its photocatalytic activity, especially the selectivity and efficiency for the oxygen reduction reaction (ORR), still needing to be improved.

[0012] In addition, although the existing technology has a certain photocatalytic self-cleaning ability, its surface modification layer has poor stability and lacks optimized design for oxygen mass transfer and three-phase interface system, especially in oxygen-enriched photocatalytic reactions. Summary of the Invention

[0013] In view of the above, the main objective of this invention is to propose an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, its preparation method, and its application, so as to solve the above-mentioned technical problems.

[0014] This invention proposes an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride mesh. The oxygen-rich three-phase photocatalyst is composed of a porous carbon fiber felt substrate, a carbon nitride mesh, a nitrogen vacancy-modified carbon nitride mesh, and a gradient grafted donor-acceptor composite material.

[0015] The porous carbon fiber felt substrate was prepared by multi-stage ultrasonic cleaning.

[0016] The carbon nitride mesh was prepared by pyrolysis.

[0017] The nitrogen-vacancy-modified carbon nitride mesh was prepared by argon-oxygen plasma etching.

[0018] The gradient grafted donor-acceptor composite material was prepared by gas-phase contact modification combined with liquid-phase photopolymerization and gradient thermo-pressing bonding.

[0019] The porous carbon fiber felt substrate, carbon nitride mesh, nitrogen vacancy modified carbon nitride mesh, and gradient grafted donor-acceptor composite material synergistically construct an oxygen mass transfer channel at the gas-liquid-solid three-phase interface to achieve oxygen-enriched photocatalysis and obtain an oxygen-enriched three-phase photocatalyst.

[0020] This invention proposes a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride mesh, used to prepare the aforementioned oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride mesh. The method includes the following steps:

[0021] Step 1: Immerse the porous carbon fiber felt in acetone solution, ethanol solution and deionized water in sequence, and perform ultrasonic cleaning using an ultrasonic cleaner. After cleaning, place it in a drying oven to dry and obtain the porous carbon fiber felt substrate.

[0022] Step 2: Mix melamine and urea in a mass ratio, place the mixture in the upper part of a tube furnace, place the porous carbon fiber felt substrate in the center of the tube furnace, then introduce argon gas to raise the temperature, and then perform pyrolysis to obtain carbon nitride mesh material.

[0023] Step 3: Place the carbon nitride mesh material in a low-temperature plasma reactor and treat it with a mixture of argon and oxygen to form nitrogen vacancy defects, thereby obtaining nitrogen vacancy modified carbon nitride mesh material.

[0024] Step 4: Place the nitrogen vacancy-modified carbon nitride mesh material and benzyl alcohol together in a closed reactor and suspend them vertically above the bottom liquid surface for processing to obtain donor-grafted carbon nitride mesh material.

[0025] Step 5: Place the donor-grafted carbon nitride mesh material in a closed reactor, add an ethanol solution containing aromatic alcohol, and irradiate it with an LED lamp to obtain the acceptor pre-assembled composite material.

[0026] The receptor pre-assembled composite material was transferred to a high-pressure reactor, and the gradient temperature was controlled and pulsed pressure cyclic treatment was performed to obtain the receptor covalently bonded material.

[0027] The acceptor covalently bonded material was transferred to an ultrasonic cleaner and injected with anhydrous ethanol for ultrasonic cleaning. After ultrasonic cleaning, it was vacuum dried in a vacuum drying oven to obtain a gradient graft donor-acceptor composite material.

[0028] Step 6: Place the gradient grafted donor-acceptor composite material in a pulse reactor and alternately introduce high-purity oxygen and nitrogen for cyclic treatment. Optimize the surface oxygen adsorption configuration and interfacial mass transfer channels through a pulsed gas activation strategy to 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 synergistically construct oxygen mass transfer channels at the gas-liquid-solid three-phase interface to achieve photocatalytic reaction under oxygen-rich conditions, thus obtaining an oxygen-rich three-phase photocatalyst.

[0029] The present invention also proposes an application of an oxygen-enriched three-phase photocatalyst based on a superhydrophobic carbon nitride grid, which is prepared by the above-mentioned preparation method of an oxygen-enriched three-phase photocatalyst based on a superhydrophobic carbon nitride grid. The oxygen-enriched three-phase photocatalyst is used to produce hydrogen peroxide.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention prepares gradient grafted donor-acceptor composite materials by combining gas-phase contact modification with liquid-phase photopolymerization and gradient thermo-pressing bonding processes. A strong chemical bonding interface is constructed on the surface of carbon nitride mesh, which significantly enhances the bonding strength between the modification layer and the substrate material. This overcomes the problem of easy detachment of the modification layer caused by relying solely on physical adsorption or chemical action in the prior art, thereby ensuring the structural stability and long cycle life of the photocatalytic material under long-term use or harsh fluid environments.

[0032] 2. This invention optimizes the oxygen adsorption configuration on the material surface through a pulsed gas activation strategy and utilizes the superhydrophobic properties of the prepared material (contact angle up to 172°) to maintain a stable gas film, successfully constructing a highly efficient gas-liquid-solid three-phase interface oxygen mass transfer channel; this enables gaseous oxygen ( It can be directly and quickly delivered to the photocatalytic active site, fundamentally overcoming the technical bottleneck of low dissolved oxygen concentration and slow diffusion rate in traditional two-phase (solid-liquid) systems, and providing a guarantee for efficient oxygen-enriched photocatalytic reactions.

[0033] 3. This invention introduces nitrogen vacancy defects through argon-oxygen plasma etching, effectively capturing electrons and suppressing electron-hole recombination. Simultaneously, it constructs directional electron transport (DA) channels through gradient grafting, synergistically optimizing carrier separation and migration efficiency. The above synergistic effect not only significantly improves photocatalytic activity but also precisely controls the oxygen reduction reaction pathway, achieving a two-electron ORR pathway selectivity of over 70%, effectively suppressing side reactions and solving the problem of insufficient photocatalytic ORR selectivity and efficiency of existing materials.

[0034] 4. The photo-induced water vapor repair technology used in this invention can effectively suppress the annihilation of nitrogen vacancy defects during the reaction process. Combined with the enhanced interface strength of gradient thermo-pressing bonding, it achieves synergistic optimization of defect stability, mass transfer kinetics and electron transport direction, so that the catalyst retains more than 95% of its activity after continuous cycling and has excellent long-term operational stability, thus solving the contradiction between high efficiency catalysis and long-term stability in existing materials.

[0035] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by means of embodiments of the invention. Attached Figure Description

[0036] Figure 1 This is the synthesis roadmap for CNDA / CF.

[0037] Figure 2 These are cross-sectional SEM images of CNDA / CF fibers, where a is a cross-sectional SEM image of CNDA / CF fibers and b is an EDS elemental mapping of nitrogen.

[0038] Figure 3 This is a schematic diagram of the photocatalytic generation of hydrogen peroxide in a two-phase system and a three-phase system.

[0039] Figure 4 It is the contact angle of water on CNDA / CF.

[0040] Figure 5 These are 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 nuclear magnetic resonance spectrum.

[0041] Figure 6 These are 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-Vis absorption spectrum of CN and CNDA powders.

[0042] Figure 7 These are the carrier dynamics characterization diagrams for CN / CF and CNDA / CF, where a is the fluorescence emission spectrum and b is the fluorescence lifetime spectrum.

[0043] Figure 8 This is a diagram of a three-phase system photocatalytic hydrogen peroxide production device.

[0044] Figure 9 The graphs compare and evaluate the photocatalytic hydrogen peroxide production performance of CN-biphase, CNDA / CF-biphase, and CNDA / CF-triphase in pure water based on area and mass, respectively. Among them, a is the hydrogen peroxide performance graph, and b is the experimental graph of CNDA / CF photocatalytic hydrogen peroxide synthesis cycle.

[0045] Figure 10 The figures show the finite element simulations of oxygen and hydrogen peroxide concentration distributions at two-phase and three-phase interfaces. (a, b) represent 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) represent the diffusion simulations of H2O2 at the two-phase and three-phase interfaces; and (e, f) represent the oxygen concentration distributions at the (e) two-phase interface and (f) three-phase interface simulated at different oxygen consumption rates.

[0046] Figure 11 The diagram shows 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 atmospheres, b is the polarization curve of RRDE, c is the number of transferred electrons diagram, and d is the selectivity diagram.

[0047] Figure 12 The diagram shows the mechanism characterization of hydrogen peroxide production by CNDA / CF. In the diagram, a is the performance of CNDA / CF in hydrogen peroxide production under different sacrificial agent conditions, and b is the EPR spectrum of CNDA / CF in the presence of DMPO.

[0048] Figure 13 The image shows 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 .

[0049] Figure 14 This is a comparison chart of hydrogen peroxide yield performance between CNDA / CF in Example 4 and CNBA / CF in Comparative Example 1. Detailed Implementation

[0050] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0051] These and other aspects of the embodiments of the present invention will become clear from the following description and accompanying drawings. In these descriptions and drawings, some specific embodiments of the present invention are specifically disclosed to illustrate some ways of implementing the principles of the embodiments of the present invention; however, it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0052] Example 1

[0053] An oxygen-enriched three-phase photocatalyst based on a superhydrophobic carbon nitride mesh, wherein the oxygen-enriched three-phase photocatalyst is composed of a porous carbon fiber felt substrate, a carbon nitride mesh, a nitrogen vacancy-modified carbon nitride mesh, and a gradient grafted donor-acceptor composite material.

[0054] The porous carbon fiber felt substrate was prepared by multi-stage ultrasonic cleaning.

[0055] The carbon nitride mesh was prepared by pyrolysis.

[0056] The nitrogen-vacancy-modified carbon nitride mesh was prepared by argon-oxygen plasma etching.

[0057] The gradient grafted donor-acceptor composite material was prepared by gas-phase contact modification combined with liquid-phase photopolymerization and gradient thermo-pressing bonding.

[0058] The porous carbon fiber felt substrate, carbon nitride mesh, nitrogen vacancy modified carbon nitride mesh, and gradient grafted donor-acceptor composite material synergistically construct an oxygen mass transfer channel at the gas-liquid-solid three-phase interface to achieve oxygen-enriched photocatalysis and obtain an oxygen-enriched three-phase photocatalyst.

[0059] Example 2

[0060] This embodiment provides a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, comprising the following steps:

[0061] Step 1: Immerse 0.5g / piece of 2cm×2cm×0.5cm porous carbon fiber felt in 80mL acetone solution, 80mL ethanol solution and 80mL deionized water in sequence, and perform ultrasonic cleaning using a 35kHz ultrasonic cleaner. After cleaning, place it in a 60℃ drying oven for 3h to obtain a porous carbon fiber felt substrate, denoted as A1.

[0062] Step 2: Mix 3.0g of melamine and 6.0g of urea at a mass ratio of 1:2. Place the mixture upstream of a tube furnace and place the porous carbon fiber felt substrate from A1 in the center of the tube furnace. Then, introduce argon gas at a flow rate of 40 sccm and heat the mixture to 540℃ at a heating rate of 5℃ / min. After heating, perform pyrolysis for 3 hours to obtain carbon nitride mesh material, denoted as B1.

[0063] Step 3: Place the carbon nitride mesh material in B1 in a low-temperature plasma reactor with a pressure of 40 kPa and a volume ratio of 3:1 of argon and oxygen into the reactor and treat it for 20 min to form nitrogen vacancy defects, thereby obtaining nitrogen vacancy modified carbon nitride mesh material, denoted as C1.

[0064] Step 4: Place the nitrogen vacancy-modified carbon nitride mesh material in C1 together with 4.0 mL of benzyl alcohol in a closed reactor at 0.5 MPa, and suspend it vertically 5 cm above the bottom liquid surface. Control the bottom temperature of the closed reactor at 300℃ and the top temperature of the closed reactor at 275℃ for 1.5 h to obtain the donor-grafted carbon nitride mesh material, denoted as D1.

[0065] Step 5: Place the donor-grafted carbon nitride mesh material in D1 into a 0.5MPa closed reactor, add 200mL of 0.2M ethanol solution containing p-nitrobenzyl alcohol, and irradiate it for 25min with an LED lamp with a light intensity of 90mW / cm² and a wavelength of 530nm to obtain the acceptor pre-assembled composite material.

[0066] The pre-assembled receptor composite material was transferred to a high-pressure reactor. The top gradient temperature of the high-pressure reactor was controlled at 275℃, and the bottom gradient temperature was controlled at 300℃. The material was subjected to 8 cycles of low-pressure pulse at 0.3MPa and high-pressure pulse at 0.7MPa, with each cycle lasting 1.5 hours, to obtain the receptor covalently bonded material.

[0067] The acceptor covalently bonded material was transferred to a 35kHz ultrasonic cleaner and injected with 200mL of anhydrous ethanol for ultrasonic cleaning for 30min. After ultrasonic cleaning, it was vacuum dried at 60℃ for 2h in a vacuum drying oven to obtain a gradient grafted donor-acceptor composite material, denoted as E1.

[0068] Step 6: Place the gradient grafted donor-acceptor composite material in E1 into a 0.7MPa pulse reactor, and alternately introduce high-purity oxygen (≥99.99%) and nitrogen (≥99.99%) for 8 cycles, with each cycle lasting 4 seconds. Optimize the surface oxygen adsorption configuration and interfacial mass transfer channels using a pulsed gas activation strategy to 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 synergistically construct oxygen mass transfer channels at the gas-liquid-solid three-phase interface to achieve photocatalytic reaction under oxygen-rich conditions, obtaining an oxygen-rich three-phase photocatalyst, denoted as F1.

[0069] Example 3

[0070] This embodiment provides a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, comprising the following steps:

[0071] Step 1: Immerse 1.2g / piece of 2cm×2cm×0.5cm porous carbon fiber felt in 100mL acetone solution, 100mL ethanol solution and 100mL deionized water in sequence, and perform ultrasonic cleaning using a 37.5kHz ultrasonic cleaner. After cleaning, place it in a 65℃ drying oven for 3.5h to obtain a porous carbon fiber felt substrate, denoted as A2.

[0072] Step 2: Mix 3.5g of melamine and 7g of urea at a mass ratio of 1:2. Place the mixture upstream of a tube furnace and place the porous carbon fiber felt substrate from A2 in the center of the tube furnace. Then, introduce argon gas at a flow rate of 45sccm and heat the mixture to 545℃ at a heating rate of 7℃ / min. After heating, perform pyrolysis for 3.25h to obtain carbon nitride mesh material, denoted as B2.

[0073] Step 3: Place the carbon nitride mesh material in B2 into a low-temperature plasma reactor with a pressure of 45 kPa and a pressure of 95 W. Introduce a mixture of argon and oxygen with a volume ratio of 3.5:1 for 25 min to form nitrogen vacancy defects and obtain nitrogen vacancy modified carbon nitride mesh material, denoted as C2.

[0074] Step 4: Place the nitrogen vacancy-modified carbon nitride mesh material in C2 together with 4.5 mL of benzyl alcohol in a closed reactor at 0.55 MPa, and suspend it vertically 7 cm above the bottom liquid surface. Control the bottom temperature of the closed reactor at 303℃ and the top temperature of the closed reactor at 278℃ for 1.7 h to obtain the donor-grafted carbon nitride mesh material, denoted as D2.

[0075] Step 5: Place the donor-grafted carbon nitride mesh material in D2 into a 0.55MPa closed reactor, add 225mL of 0.25M ethanol solution containing p-cyanobenzyl alcohol, and irradiate it for 28min with an LED lamp with a light intensity of 95mW / cm² and a wavelength of 535nm to obtain the acceptor pre-assembled composite material.

[0076] The pre-assembled receptor composite material was transferred to a high-pressure reactor. The top gradient temperature of the high-pressure reactor was controlled at 278℃, and the bottom gradient temperature was controlled at 303℃. The material was subjected to 9 cycles of low-pressure pulse at 0.35MPa and high-pressure pulse at 0.75MPa, with each cycle lasting 1.7h, to obtain the receptor covalently bonded material.

[0077] The acceptor covalently bonded material was transferred to a 38kHz ultrasonic cleaner and injected with 225mL of anhydrous ethanol for ultrasonic cleaning for 33min. After ultrasonic cleaning, it was vacuum dried at 65℃ for 2.25h in a vacuum drying oven to obtain a gradient graft donor-acceptor composite material, denoted as E2.

[0078] Step 6: Place the gradient grafted donor-acceptor composite material in E2 into a 0.75MPa pulse reactor, and alternately introduce high-purity oxygen (≥99.99%) and nitrogen (≥99.99%) for 9 cycles, with each cycle lasting 4.5s. Optimize the surface oxygen adsorption configuration and interfacial mass transfer channels using a pulsed gas activation strategy to 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 synergistically construct oxygen mass transfer channels at the gas-liquid-solid three-phase interface to achieve photocatalytic reaction under oxygen-rich conditions, obtaining an oxygen-rich three-phase photocatalyst, denoted as F2.

[0079] Example 4

[0080] This embodiment provides a method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, comprising the following steps:

[0081] Step 1: Immerse 1.5g / piece of 2cm×2cm×0.5cm porous carbon fiber felt in 120mL acetone solution, 120mL ethanol solution and 120mL deionized water in sequence, and perform ultrasonic cleaning using a 45kHz ultrasonic cleaner. After cleaning, place it in an 80℃ drying oven for 5h to obtain a porous carbon fiber felt substrate, denoted as A3.

[0082] Step 2: Mix 5.0g of melamine and 10.0g of urea at a mass ratio of 1:2. Place the mixture at the upstream of a tube furnace and place the porous carbon fiber felt substrate from A3 in the center of the tube furnace. Then, introduce argon gas at a flow rate of 60sccm and heat the mixture to 560℃ at a heating rate of 10℃ / min. After heating, perform pyrolysis for 4 hours to obtain carbon nitride mesh material, denoted as B3.

[0083] Step 3: Place the carbon nitride mesh material in B3 in a low-temperature plasma reactor with a pressure of 60 kPa and a volume ratio of 3:1 of argon and oxygen into the reactor and treat it for 40 min to form nitrogen vacancy defects, thereby obtaining nitrogen vacancy modified carbon nitride mesh material, denoted as C3.

[0084] Step 4: Place the nitrogen vacancy-modified carbon nitride mesh material in C3 together with 6.0 mL of benzyl alcohol in a closed reactor at 1.5 MPa, and suspend it vertically 10 cm above the bottom liquid surface. Control the bottom temperature of the closed reactor at 310℃ and the top temperature of the closed reactor at 285℃ for 2.5 h to obtain the donor-grafted carbon nitride mesh material, denoted as D3.

[0085] Step 5: Place the donor-grafted carbon nitride mesh material in D3 into a 1.5MPa closed reactor, add 300mL of 0.4M ethanol solution containing p-nitrobenzyl alcohol, and irradiate it for 35min with an LED lamp with a light intensity of 110mW / cm² and a wavelength of 550nm to obtain the acceptor pre-assembled composite material.

[0086] The pre-assembled receptor composite material was transferred to a high-pressure reactor. The top gradient temperature of the high-pressure reactor was controlled at 285℃, and the bottom gradient temperature was controlled at 310℃. The material was subjected to 12 cycles of low-pressure pulse at 0.5MPa and high-pressure pulse at 0.9MPa, with each cycle lasting 2.5 hours, to obtain the receptor covalently bonded material.

[0087] The acceptor covalently bonded material was transferred to a 45kHz ultrasonic cleaner and injected with 300mL of anhydrous ethanol for ultrasonic cleaning for 40min. After ultrasonic cleaning, it was vacuum dried at 80℃ for 3h in a vacuum drying oven to obtain a gradient grafted donor-acceptor composite material, denoted as E3.

[0088] Step 6: Place the gradient grafted donor-acceptor composite material in E3 into a 0.9MPa pulse reactor, and alternately introduce high-purity oxygen (≥99.99%) and nitrogen (≥99.99%) for 12 cycles, with each alternating introduction time being 6s. Optimize the surface oxygen adsorption configuration and interfacial mass transfer channels through a pulsed gas activation strategy to 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 synergistically construct oxygen mass transfer channels at the gas-liquid-solid three-phase interface to achieve photocatalytic reaction under oxygen-rich conditions, obtaining an oxygen-rich three-phase photocatalyst, denoted as F3.

[0089] Comparative Example 1

[0090] The difference between this embodiment and embodiment 4 is that the method includes:

[0091] S1. Place 0.5g of urea powder at the bottom of a test tube, and place multi-walled carbon nanotubes (5-15nm long per tube) inside the test tube near the opening (the mass ratio of urea to carbon nanotubes is 1:2). Place the test tube in a muffle furnace and heat it to 450℃ at a heating rate of 2.5℃ / min, and keep it at 450℃ for 3 hours. Then cool it naturally to room temperature to obtain a carbon fiber composite material coated with carbon nitride.

[0092] S2. Place 0.5g of phenylethanol at the bottom of another test tube, and place the composite material prepared in step S1 inside the test tube near the opening (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, heat to 350℃ at a heating rate of 7.5℃ / min, and maintain at 350℃ for 1.5h; then cool naturally to room temperature to obtain the phenylethanol-modified hydrophobic composite material CNBA / CF.

[0093] Application Example 1

[0094] This embodiment provides an application of an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride mesh. The oxygen-rich three-phase photocatalyst prepared using the aforementioned method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride mesh is applied to the production of hydrogen peroxide. The method includes:

[0095] The oxygen-enriched 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 was added to the aqueous side for irradiation, and a stable hydrophobic film was observed to form on the surface of the three-phase photocatalyst. Oxygen was continuously supplied from the other side, which greatly improved the mass transfer efficiency of oxygen in the reaction medium, thereby facilitating the activation of the oxygen catalyst interface and increasing the photocatalytic yield of hydrogen peroxide.

[0096] To verify the effectiveness of the present invention, the oxygen-rich triphase 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 mesh (CN / CF), a donor-grafted carbon nitride mesh material (CND / CF), and a gradient-grafted donor-acceptor composite material (CNDA / CF). Figure 1 The synthesis process of gradient grafted donor-acceptor composite materials is illustrated schematically.

[0097] The carbon fiber surface is uniformly coated with a ~74.71nm catalytic layer. Figure 2 (a) Nitrogen signal is uniformly distributed ( Figure 2 (b) demonstrates that plasma etching did not destroy the integrity of the carbon nitride framework, and nitrogen vacancies were uniformly generated. The orderly generation of nitrogen vacancies is a key prerequisite for selective catalysis. After gradient assembly, the interface showed no cracks, proving that the gradient temperature process ensured the interlayer bonding strength. This structural integrity is directly related to the improvement of mass transfer efficiency. In the three-phase system (right) ( Figure 3 ), pulse pre-activation layer promotes In GDL diffusion, the mass transfer coefficient is improved. times ( This design breaks through the dissolved oxygen limitation of the two-phase system (left), providing a physical basis for efficient photocatalysis.

[0098] The superhydrophobic interface achieves Cassie-Baxter states, attributed to gradient assembly regulating the spatial distribution of surface functional groups, with a contact angle of 172°. Figure 4 The superhydrophobic properties create decisive conditions for the maintenance of the gas film. The peak shift at 27.9° (002) confirms the enhancement of π-π stacking ( Figure 5 In (a), photo-induced water vapor repair maintains the stability of the vacancy structure, and the full width at half maximum (FWHM) decreases by 0.15°. This crystal order is closely related to electron transport performance. Place Vibration peaks prove that benzyl alcohol was grafted ( Figure 5 (b) The enhanced respiratory pattern peaks reflect the increased orderliness of heptaazine units due to gradient assembly, proving that the ordered arrangement at the molecular level directly guides the evolution of band structure.

[0099] The area of ​​the CON peak at 287.2 eV increases ( Figure 5 The pulse pre-activation induces the directional alignment of phenoxy groups, increasing the carbon-nitrogen single and double bond strengths from 0.146 to 0.525. This change in chemical state provides microscopic evidence for selective adsorption. A new peak at 30 ppm for benzene ring C confirms gradient assembly. Figure 5 d; at 65ppm A chemical shift of 2.3 ppm demonstrates that donor-acceptor electron coupling is evident in photoelectric properties.

[0100] The price band peak rose from 2.16 eV (CN) to 2.23 eV (CNDA). Figure 6 (a) Gradient assembly enhances hole migration capability, matches ORR oxidation potential, and precise bandgap positioning provides thermodynamic assurance for charge separation. UV-Vis absorption broadens from 471 nm in CN to 514 nm in CNDA, with a significant red shift at the absorption edge. Figure 6 (b) The broadened light absorption of CNDA is attributed to n→π* due to the introduction of benzyloxy and benzene rings. The fluorescence intensity of CNDA is significantly reduced ( Figure 7 (a) Nitrogen vacancies as electron trapping suppression Recombination, a blue shift in the spectral peak, and a decrease in fluorescence intensity confirm the electron trapping effect of nitrogen vacancies. Carrier recombination suppression is further verified over time. The average carrier lifetime decreased from 4.55 ns to 2.76 ns. Figure 7 (b) The gradient DA channel accelerates carrier migration, and the lifetime is reduced to 2.76 ns, which directly reflects the electronic acceleration effect of the gradient DA channel. This kinetic optimization plays a core role in three-phase catalysis.

[0101] In a three-phase system, a stable gas film is maintained at the superhydrophobic interface. Figure 8The pulsed pre-activation layer (gray) is directly exposed to the gaseous reactants; the stable gas film maintained by the superhydrophobic interface (yellow arrow) is the physical manifestation of three-phase synergy. The device design maximizes the gas-solid contact efficiency of the pulsed pre-activation layer. Three-phase CNDA yield. ( Figure 9 (a) represents a 3-fold improvement over the two-phase system; the 3-fold improvement in the three-phase system quantifies the enhanced mass transfer effect, and the performance leap requires in-depth analysis in conjunction with the synthesis methodology; the activity retention rate after 6 cycles is >95% ( Figure 9 (b) Photo-induced water vapor repair inhibits nitrogen vacancy annihilation; 95% activity retention is attributed to the vacancy stabilization mechanism of photorepair, demonstrating the dual advantages of interface design revealed by kinetic analysis.

[0102] Rapid oxygen supply to the photocatalytic surface in a three-phase interface was investigated, and oxygen diffusion and concentration at the catalytic interface were monitored using finite element simulation. A 500μm×500μm×1000μm interface geometric model with a catalytic layer thickness of 1μm was employed. Figure 10 (ad in the text). Clearly, due to the slow diffusion of O2 in water, there is an O2 depletion layer with a very low O2 concentration near the two-phase catalytic interface (…). Figure 10 (a) However, due to the rapid gas diffusion pathway, this situation is overcome at the O2 / catalyst / H2O three-phase interface ( Figure 10 (b) Regarding the generation of H2O2, it is clear that the accumulation of H2O2 at the interface between the two phases is relatively low ( Figure 10 (c) but there is more H2O2 at the three-phase interface. Due to the rich O2 content at the three-phase catalytic interface, H2O2 exhibits a clear gradient distribution at the interface ( Figure 10 (d) Considering the dynamic consumption and supply of O2 during the photogeneration of H2O2, the O2 concentration at the interface under different consumption rates was simulated. The results show that the O2 concentration at the interface between the two phases decreases in a dependent manner with the change of O2 consumption rate (d). Figure 10 (e). 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 10 f in the middle. Yield under atmosphere ( Figure 11 (a) in the text proves that the pulse pre-activated layer preferentially adsorbs gaseous oxygen; The yield difference under different atmospheres demonstrates the crucial role of gaseous oxygen, while stability becomes the ultimate test for industrial applications.

[0103] CNDA at an initial potential of -0.2V ( Figure 11(b) The disk current density is 2.1 times higher than that of CN, and pulse pre-activation optimizes the oxygen adsorption configuration; the -0.2V onset potential and the 2.1-fold increase in current density demonstrate the advantages of pulse pre-activation, indicating that the electron transfer pathway needs quantitative characterization. Average n=2.08 (0 to -0.2V) Figure 11 (c) The gradient DA channel ensures that the two-electron ORR path dominates. Side reactions <10%; n=2.08 confirms the dominance of the two-electron pathway, and the gradient DA channel suppresses side reactions, a conclusion reinforced by selectivity data. CNDA selectivity >70% (CN only 28%) Figure 11 In d), nitrogen vacancies promote end-group adsorption mode and inhibit [the adsorption of nitrogen vacancies]. Bond breaking; 70% selectivity is due to the promotion of end-group adsorption mode by nitrogen vacancies, and scavenger experiments provide corroborating evidence for the reaction pathway.

[0104] Add pBQ ( The scavenger produces almost no hydrogen peroxide. Figure 12 (a) confirms nitrogen vacancy-mediated This is the first step reaction; confirming nitrogen vacancy-mediated [reaction]. The first-step reaction was generated, and the superoxide reactive intermediate was directly observed using spin trapping technology. Figure 12 (b) In situ infrared testing results show that: Peak intensity increases with increasing illumination time. Figure 13 a in Figure 13 (b) The peak intensity also increases with increasing illumination time, indicating that as the reaction proceeds, It is continuously generated and accumulated on the surface.

[0105] Using a self-designed photocatalytic hydrogen peroxide production device, such as the CNBA / CF modified with only benzyl alcohol in Comparative Example 1, the hydrogen peroxide yield after 1 hour was [missing information]. In Example 4, the yield of hydrogen peroxide produced by CNDA / CF after 1 hour was... The hydrogen peroxide production performance of CNBA / CF modified with benzyl alcohol alone is much lower than that of CNDA / CF after modification. Figure 14 Furthermore, the material exhibits poor stability; experiments revealed that the hydrophobicity of the material surface changed within a short period. Therefore, the CNDA / CF modified using this technique helps form a stable hydrophobic film. 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.

[0106] In summary, this invention effectively enhances oxygen diffusion and activation capabilities and significantly improves hydrogen peroxide generation efficiency by constructing gas-liquid-solid interface mass transfer channels, regulating nitrogen vacancy structures and gradient electron transport networks. Furthermore, it greatly enhances catalytic stability by leveraging superhydrophobic interface properties, breaking through the technical bottleneck of synergistic optimization of mass transfer and activity in traditional photocatalytic systems, and providing an efficient solution for green synthesis and pollution control.

[0107] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions 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 one or more embodiments or examples.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should 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 includes the following steps: Step 1: Immerse the porous carbon fiber felt in acetone solution, ethanol solution and deionized water in sequence, and perform ultrasonic cleaning using an ultrasonic cleaner. After cleaning, place it in a drying oven to dry and obtain the porous carbon fiber felt substrate. Step 2: Mix melamine and urea at a set mass ratio, place the mixture in the upper part of a tube furnace, place the porous carbon fiber felt substrate in the center of the tube furnace, and then introduce argon gas to raise the temperature. After raising the temperature, pyrolysis is carried out to obtain carbon nitride mesh material. Step 3: Place the carbon nitride mesh material in a low-temperature plasma reactor and treat it with a mixture of argon and oxygen to form nitrogen vacancy defects, thereby obtaining nitrogen vacancy modified carbon nitride mesh material. Step 4: Place the nitrogen vacancy-modified carbon nitride mesh material and benzyl alcohol together in a closed reactor and suspend them vertically above the bottom liquid surface for processing to obtain donor-grafted carbon nitride mesh material. The process of vertically suspending the material above the bottom liquid surface includes: vertically suspending the nitrogen-vacancy-modified carbon nitride mesh material 5-10cm above the bottom liquid surface, controlling the bottom temperature of the closed reactor to 300-310℃ and the top temperature of the closed reactor to 275-285℃. Step 5: Place the donor-grafted carbon nitride mesh material in a closed reactor, add an ethanol solution containing aromatic alcohol, and irradiate it with an LED lamp to obtain the acceptor pre-assembled composite material. The pre-assembled receptor composite material was transferred to a high-pressure reactor, and the gradient temperature was controlled and subjected to low-pressure pulse and high-pressure pulse cyclic treatment to obtain the receptor covalently bonded material. The process of controlling the gradient temperature and performing low-pressure pulse and high-pressure pulse cycling includes: controlling the top temperature of the high-pressure reactor at 275-285℃, controlling the bottom temperature of the high-pressure reactor at 300-310℃, applying low-pressure pulses of 0.3-0.5MPa, and applying high-pressure pulses of 0.7-0.9MPa. The acceptor covalently bonded material was transferred to an ultrasonic cleaner and injected with anhydrous ethanol for ultrasonic cleaning. After ultrasonic cleaning, it was vacuum dried in a vacuum drying oven to obtain a gradient graft donor-acceptor composite material. Step 6: Place the gradient grafted donor-acceptor composite material in a pulse reactor and alternately introduce oxygen and nitrogen for cyclic treatment. Optimize the surface oxygen adsorption configuration and interfacial mass transfer channels through a pulsed gas activation strategy to 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 synergistically construct oxygen mass transfer channels at the gas-liquid-solid three-phase interface to achieve photocatalytic reaction under oxygen-rich conditions, thus obtaining an oxygen-rich three-phase photocatalyst.

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

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

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

5. The method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid according to claim 1, characterized in that, In step 4, during the process of obtaining the donor-grafted carbon nitride mesh material, the volume of benzyl alcohol is 4.0-6.0 mL, the pressure of the closed reactor is 0.5-1.5 MPa, and the treatment time is 1.5-2.5 h with the material vertically suspended above the bottom liquid surface.

6. The method for preparing an oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid according to claim 1, characterized in that, In step 5, during the process of obtaining the receptor pre-assembled composite material, the pressure of the closed reactor is 0.5-1.5 MPa, the concentration of the ethanol solution containing aromatic alcohol is 0.2-0.4 M, the volume of the ethanol solution containing aromatic alcohol is 200-300 mL, the light intensity of the LED lamp is 90-110 mW / cm², the irradiation time of the LED lamp is 25-35 min, and the wavelength of the LED lamp is 530-550 nm. In the process of obtaining the acceptor covalently bonded material, the number of cycles is 8-12, and the duration of each cycle is 1.5-2.5 hours; In the process of obtaining gradient graft donor-acceptor composite materials, the ultrasonic cleaning frequency is 35-45kHz, the volume of injected anhydrous ethanol is 200-300mL, the ultrasonic treatment time is 30-40min, the temperature of the vacuum drying oven 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 superhydrophobic 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 superhydrophobic carbon nitride grid according to claim 1, characterized in that, In step 6, during the process of obtaining the oxygen-enriched 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.

9. An oxygen-rich three-phase photocatalyst based on a superhydrophobic carbon nitride grid, characterized in that, The oxygen-enriched three-phase photocatalyst was prepared using the method described in any one of claims 1 to 8 for preparing an oxygen-enriched three-phase photocatalyst based on a superhydrophobic carbon nitride grid.

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

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