A parallel interface engineered viologen-based defective carbon nitride composite material, a preparation method and application thereof

Abstract

This invention discloses a parallel-interface engineered viologen-based defective carbon nitride composite material, its preparation method, and its applications, belonging to the field of energy catalysis and photochemical materials technology. The material comprises: a defective graphitic carbon nitride support; single-atom platinum catalytic sites supported on the support; and a selenium-containing viologen compound anchored by covalent bonds in a configuration parallel to the support surface. Through a bilateral covalent bonding strategy, viologen molecules are stably anchored in a parallel configuration to the single-atom platinum-modified defective carbon nitride surface, constructing a highly efficient and stable "electron bridge" structure, significantly enhancing interfacial bonding and photogenerated electron transport efficiency. This composite material exhibits excellent photocatalytic hydrogen evolution activity and efficient coupling ability with benzylamine oxidation under visible light, and its activity retention rate reaches over 92% after 144 hours of cycling. It provides a new paradigm for solving the problem of poor interfacial stability in photocatalysts and has significant application prospects in the field of solar fuel synthesis.

Description

Technical Field

[0001] This invention belongs to the field of energy catalysis and photochemical materials technology, and relates to a parallel interface engineered viologen-based defective carbon nitride composite material, its preparation method and application, specifically a parallel interface engineered single-atom platinum / defective carbon nitride and selenium-containing viologen composite photocatalyst, its preparation method and its application in photocatalytic hydrogen evolution and organic amine oxidation reactions. Background Technology

[0002] Against the backdrop of global energy structure transformation and the grand goal of "dual carbon" (carbon diversification and carbon emission reduction), developing clean and sustainable energy conversion technologies has become a core issue for the global scientific community. Solar energy, as an inexhaustible and widely distributed ultimate energy source, is crucial for achieving future sustainable development through its efficient utilization. Among these technologies, photocatalytic water splitting for hydrogen production, which directly converts solar energy into storable, high-energy-density hydrogen chemical energy, is considered one of the most promising pathways to achieving a "green hydrogen economy." However, the efficiency of the photocatalytic process has long been constrained by the rapid recombination of photogenerated electron-hole pairs and the slow interfacial reaction kinetics. Therefore, designing and constructing novel photocatalysts that can efficiently separate charges, accelerate surface reactions, and are themselves stable is fundamental to driving this technology towards practical application.

[0003] Among numerous semiconductor photocatalysts, graphitic carbon nitride (g-C3N4) has become a research hotspot in non-metallic photocatalytic materials due to its unique graphene-like two-dimensional layered structure, suitable visible light response band gap (approximately 2.7 eV), excellent chemical and thermal stability, and environmentally friendly properties stemming from Earth-rich elements (C and N). However, intrinsic bulk g-C3N4 suffers from inherent defects such as small specific surface area, limited visible light absorption range, low carrier mobility, and high recombination rate of photogenerated electron-hole pairs, resulting in its actual photocatalytic activity falling far short of application requirements.

[0004] To address the above problems, researchers have developed a series of modification strategies, mainly including: (1) Morphology control and defect engineering: By controlling the precursor thermal polymerization process or post-processing methods, ultrathin nanosheets and porous structures are prepared to increase the specific surface area and shorten the charge migration path; at the same time, nitrogen or carbon defects are introduced into the g-C3N4 framework to adjust its electronic structure, broaden the light absorption range, and create new active sites. (2) Noble metal loading: Platinum (Pt), gold (Au) and other noble metal nanoparticles are loaded on the surface of g-C3N4, and their Schottky junction effect and surface plasmon resonance effect are used to promote the capture and separation of photogenerated electrons, and serve as highly efficient hydrogen evolution active sites. In recent years, the emerging single-atom catalysis technology has further maximized the utilization efficiency of noble metals. For example, anchoring Pt in single-atom form on g-C3N4 not only achieves atomic-level dispersion and cost reduction, but its unique electronic structure and coordination environment also exhibit superior catalytic performance compared to nanoparticles. (3) Constructing heterojunctions or introducing electron mediators: By combining g-C3N4 with other semiconductors to form heterojunctions (such as Type-II and Type-Z), or by combining it with organic molecules with excellent electron accepting / transfer capabilities (such as viologen and its derivatives), a built-in electric field or additional electron transfer channel can be constructed, thereby achieving effective separation of photogenerated electrons and holes in space.

[0005] Viologen compounds (1,1'-disubstituted-4,4'-bipyridinium salts), as classic electron acceptors, have been widely used in electrochromism, supramolecular chemistry, and energy storage due to their reversible redox properties and stable free radical cation states. In photocatalytic systems, viologens act as electron mediators, bridging the photocatalyst and reactants (such as H+). +Viologen accelerates interfacial electron transfer through rapid redox cycles, thereby improving reaction efficiency. However, the traditional binding of viologen to g-C3N4 mainly relies on physical adsorption or electrostatic interactions. This non-covalent bonding method is prone to viologen molecule detachment in photocatalytic reactions, especially during long-term cycling, leading to interfacial structural deactivation and severely limiting the catalyst's cycling stability and application potential. To balance the electron transport efficiency and interfacial stability of viologen, researchers have attempted to use covalent bonding strategies to form chemical connections such as amide bonds between viologen and g-C3N4 through terminal functional groups. However, existing methods are mostly "single-point anchoring," where viologen molecules are grafted onto the substrate surface in an upright configuration. Although this configuration enhances stability, the electron coupling strength is limited because electrons must rely on a long-distance "through-space" path for transfer, and the transport efficiency remains a bottleneck. Meanwhile, the optimization of the viologen molecule structure itself is ongoing. For example, replacing the nitrogen atom or its side chain in the bipyridine ring with chalcogenides (such as selenium) has led to the development of novel derivatives such as selenium-containing viologen. Due to the larger atomic radius, more easily polarized properties, and narrower HOMO-LUMO band gap of selenium atoms, selenium violet generally exhibits stronger visible light absorption, a more positive reduction potential, and a more stable free ground state than conventional violet, thus demonstrating superior electronic mediation ability in photocatalysis.

[0006] Despite advancements in defect engineering, single-atom loading, and selenoporin modification, a significant challenge remains: how to integrate the high efficiency of single-atom metals, defect bandgap modulation, the excellent electronic mediation capabilities of selenoporin, and the interfacial coupling and structural stability resulting from stable covalent bonding in a cohesive design. In existing systems, these functional units are typically introduced relatively independently, with interfacial bonding relying heavily on electrostatic or weak interactions. This limited interfacial coupling makes it difficult to form stable and efficient electron transport interface structures, thus restricting the effective separation and transport efficiency of photogenerated carriers. In particular, how to stably anchor selenoporin molecules to the g-C3N4 surface via stable covalent bonds, constructing a directional electron transport channel with both strong interfacial coupling and high stability, thereby enabling rapid directional migration of photogenerated electrons between the semiconductor host and catalytically active sites—achieving ultrafast electron transfer from the semiconductor host to the catalytically active reaction site—is a key scientific and technological challenge in overcoming the bottleneck of photocatalytic efficiency. Summary of the Invention

[0007] In existing technologies, selenium viologen (SeV) is used as an electron mediator in conjunction with carbon nitride (g). When combined with C3N4-based photocatalytic materials, there are technical problems such as weak interfacial bonding, difficulty in interfacial structure control, low electron transport efficiency, insufficient photocatalytic hydrogen evolution performance, and poor cycle stability. The present invention aims to provide a parallel interface engineered viologen-based defective carbon nitride composite material, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a vizimine-based defective carbon nitride composite material engineered with parallel interfaces, comprising: Defective graphitic carbon nitride support; Single-atom platinum catalytic sites supported on the defective graphitic carbon nitride support; And a selenium-containing viologen compound anchored by covalent bonds to the surface of the single-atom platinum-modified defective graphitic carbon nitride support; wherein the selenium-containing viologen compound is fixed on the support in a configuration parallel to the support surface.

[0009] The defective graphitic carbon nitride support is graphitic carbon nitride g-C3N4 that has undergone defect engineering treatment, and the defects include at least one of nitrogen vacancies, carbon vacancies or cyano defects.

[0010] Preferably, the defect is a carbon vacancy.

[0011] The selenium-containing viologen compound is either monocarboxylated selenium-containing viologen or dicarboxylated selenium-containing viologen.

[0012] The monocarboxyl selenoid viologen has the structure shown in formula (I). , where R is any one of methyl, phenyl, or benzyl; The structural formula of the dicarboxylated selenium violet is: .

[0013] The carboxyl group (-COOH) is an excellent anchoring group, capable of forming stable covalent bonds (such as amide bonds) with amino groups or defect sites on the surface of defective carbon nitrides. This is a prerequisite for achieving a "parallel configuration." The dicarboxyl group provides a bilateral anchoring basis, making it the most ideal structure for achieving a parallel configuration.

[0014] Preferably, the structural formula of monocarboxyl selenoid viologen is as follows: ; More preferably, the selenium-containing viologen compound is a dicarboxylated selenium-containing viologen.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned parallel interface engineered viologen-based defective carbon nitride composite material, comprising the following steps: (1) Preparation of defective graphitic carbon nitride support (g-C3N4); (2) Disperse the defective graphitic carbon nitride support (g-C3N4), add a platinum source, irradiate the reaction with a xenon lamp, heat to remove moisture, and obtain a defective graphitic carbon nitride support (g-C3N4) with single-atom platinum deposition. (3) Under argon protection, the selenium-containing viologen compound was stirred and reacted with a defective graphitic carbon nitride support (g-C3N4) deposited by single-atom platinum, washed and vacuum dried to obtain a viologen-based defective carbon nitride composite material with parallel interface engineering.

[0016] Step (1) specifically involves calcining the urea solution at 500 ℃~600 ℃ in air for 2 h~6 h, and then naturally cooling it to room temperature.

[0017] Preferably, the calcination temperature is 550℃ and the calcination time is 4h.

[0018] Preferably, the heating rate of calcination is 5~10 °C / min, more preferably 5 °C / min.

[0019] In step (2), the mass ratio of defective graphitic carbon nitride support (g-C3N4) to platinum source is (20~50):1, the xenon lamp irradiation time is 1 h~3 h, and the platinum source is H2PtCl6·6H2O or potassium chloroplatinate.

[0020] Preferably, the mass ratio of the defective graphitic carbon nitride support (g-C3N4) to the platinum source is (33~50):1, and the platinum source is H2PtCl6·6H2O.

[0021] In step (3), the mass ratio of the selenium-containing violen compound to the defective graphitic carbon nitride support (g-C3N4) deposited by single-atom platinum is 1:(10~100), and the reaction is carried out at room temperature for 6 h~24 h.

[0022] Preferably, the mass ratio of the selenium-containing violet compound to the defective graphitic carbon nitride support (g-C3N4) deposited by single-atom platinum is 1:(20~50).

[0023] Thirdly, the present invention provides the application of the above-mentioned parallel interface engineered vizigon-based defective carbon nitride composite material in photocatalytic hydrogen production.

[0024] Fourthly, the present invention provides a photocatalytic reaction system comprising the above-mentioned parallel interface engineered vigonyne-based defective carbon nitride composite material, wherein the parallel interface engineered vigonyne-based defective carbon nitride composite material is dispersed in the reaction medium in powder form for photocatalytic hydrogen evolution reaction or organic oxidation reaction driven by visible light.

[0025] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a parallel-interface engineered viologen-based defective carbon nitride composite material. The selenium-containing viologen compound is covalently anchored and fixed on a single-atom platinum-modified defective carbon nitride in a configuration parallel to the support surface. By integrating three functional components (light-absorbing unit g-C3N4, electron mediator viologen, and active center Pt) through a specific interfacial structure (covalent anchoring to form a stable interfacial structure and constructing a parallel interfacial configuration), the problems of weak interfacial bonding, tortuous electron transport paths, and low efficiency in existing technologies are effectively solved. Compared to physical adsorption or electrostatic interaction, covalent anchoring provides stronger binding force and a more stable interface, which is the basis for achieving long cycle life. The parallel configuration maximizes the reduction of the distance between viologen molecules and the support surface and enhances the electronic coupling between the viologen conjugated system and the support surface, thereby forming a highly efficient interfacial electron transport channel. This allows photogenerated electrons to be rapidly and unimpededly transferred from carbon nitride to viologen, and then to the single-atom platinum catalytic active center, thus achieving a highly efficient photogenerated electron transport and catalytic reaction process, and significantly improving the photocatalytic hydrogen evolution performance and the cycling stability of the material.

[0026] Furthermore, the defective graphitic carbon nitride support is a defective g-C3N4 containing carbon vacancies. These carbon defects originate from the partial absence of carbon elements, and the defect structure can effectively regulate the electronic structure and band structure of g-C3N4. The introduction of defects can adjust the conduction and valence band positions of g-C3N4 and broaden its visible light absorption range, thereby improving solar energy utilization efficiency. Defect sites can act as shallow potential traps for photogenerated electrons, temporarily trapping electrons and inhibiting their recombination with holes, thus extending the lifetime of photogenerated carriers. Simultaneously, carbon defects can also serve as active centers for catalytic reactions and coordination anchoring sites for single-atom platinum and viologen molecules, thereby enhancing interfacial bonding strength and improving material structural stability. This provides a stable interfacial structural basis and an ideal coordination environment for the subsequent stable anchoring of single-atom platinum and covalent bonding of viologen molecules.

[0027] Furthermore, the composite photocatalyst (DCSeV-Pt-CN), with its unique "electron bridge" parallel interface structure, ensures interfacial stability through bivalent bonds and establishes a highly efficient and directional electron transport channel. This structure can synergistically collect and rapidly transport photogenerated electrons; therefore, the catalyst exhibits excellent photocatalytic hydrogen evolution activity under visible light (with a maximum rate of 3231.9 μmol·h⁻¹). -1 ·g -1 And its highly efficient coupling ability with benzylamine oxidation (benzylamine oxidation rate reaches 1390.6 μmol·h⁻¹) -1 ·g -1 ).

[0028] The preparation method provided by this invention features a simple process, readily available raw materials, and mild conditions (except for the first calcination step), exhibiting good repeatability and potential for large-scale production. Defects can be introduced through simple calcination conditions, making the method simple, low-cost, and easily scalable. Using xenon lamp irradiation for photodeposition, photogenerated electrons can selectively reduce platinum ions and anchor them at carbon defect sites, thereby obtaining highly dispersed, uniformly sized single-atom platinum, significantly improving the atomic utilization of the noble metal and enhancing catalytic activity. The mild conditions facilitate a thorough and directional condensation reaction between viologen molecules and the functional groups on the support surface through their carboxyl groups, achieving stable covalent anchoring of viologen molecules on the support surface and forming a tightly coupled interfacial structure.

[0029] Furthermore, an innovative two-sided covalent bonding strategy was adopted to covalently anchor dicarboxylated selenoporogen (DCSeV), which possesses excellent redox activity and visible light response, onto a single-atom platinum-modified defective carbon nitride (Pt-CN) surface in a parallel configuration. This method fundamentally solves the technical problems of interfacial instability, long electron transport paths, and low efficiency caused by traditional electrostatic adsorption or single-point covalent bonding.

[0030] The application provided by this invention is that the viologen-based defective carbon nitride composite material engineered by the present invention, used as a catalyst for photocatalytic hydrogen production, exhibits ultra-long cycle stability and reaction durability. Thanks to the stable bivalent bond interface structure formed between viologen molecules and the support, its catalytic hydrogen evolution activity can still maintain more than 92% of its initial value after a continuous photocatalytic reaction of up to 144 hours (6 cycles). This stability is significantly better than the control system based on electrostatic adsorption or single-point covalent bonding, effectively solving the problem of catalyst deactivation caused by unstable interfacial bonding in existing photocatalytic systems. Therefore, the parallel interface engineered composite material constructed by this invention not only has excellent photocatalytic hydrogen production performance but also good long-term operational stability, and can be applied to solar-driven hydrogen energy conversion and related photocatalytic energy conversion fields, showing good application prospects in solar hydrogen production and clean energy conversion technologies. Attached Figure Description

[0031] Figure 1 The displayed image shows the proton nuclear magnetic resonance spectrum of compound 2 prepared in Example 1 of this invention. 1 H NMR spectrum; Figure 2 The carbon nuclear magnetic resonance spectrum of compound 2 prepared in Example 1 of this invention is shown. 13 C NMR spectrum; Figure 3 The image shown is the proton nuclear magnetic resonance spectrum of compound 4 prepared in Example 2 of this invention. 1 H NMR spectrum; Figure 4The carbon nuclear magnetic resonance spectrum of compound 4 prepared in Example 2 of this invention is shown. 13 C NMR spectrum; Figure 5 The image shown is a scanning electron microscope image of the defective carbon nitride composite material of the present invention; Figure 6 The image shows a comparison of the elemental analysis results of defect-free carbon nitride and carbon-containing defective carbon nitride in this invention. Figure 7 The image shown is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the composite material (Pt-CN) loaded with single-atom Pt of the present invention. Figure 8 The image shows the X-ray absorption fine structure (XAFS) pattern of Pt-CN; Figure 9 The image shown is an infrared spectrum of the DCSeV-Pt-CN composite material provided by this invention. Figure 10 The image shows the photocurrent time response curves (it) of four viologens (DCSeV, BCSeV, DCV, BnSeV) provided in Embodiments 1-2 and Comparative Examples 1-2 of this invention. Figure 11 The images show the electrochemical impedance spectroscopy (EIS) spectra of four viologens (DCSeV, BCSeV, DCV, BnSeV) provided in Examples 1-2 and Comparative Examples 1-2 of this invention. Figure 12 The images show the photocurrent time response curves (it) of all viologen-based defective carbon nitride composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) provided in Examples 3-4 and Comparative Examples 3-4 of this invention, as well as the reference sample Pt-CN. Figure 13 The electrochemical impedance spectroscopy of viologen-based defective carbon nitride composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) provided in Examples 3-4 and Comparative Examples 3-4 of the present invention, as well as the reference sample Pt-CN, is shown. Figure 14 The image shows the electron paramagnetic resonance (EPR) spectra of the DCSeV-Pt-CN composite material provided in Example 3 of the present invention under different illumination times. Figure 15 The cumulative hydrogen production of viologen-based defective carbon nitride composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) provided in Examples 3-4 and Comparative Examples 3-4 of the present invention is shown in 48 hours. Figure 16 The results shown are the cyclic hydrogen production stability test results of the viologen-based defective carbon nitride composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) provided in Examples 3-4 and Comparative Examples 3-4 of this invention.

[0032] Figure 17 The image shows the X-ray diffraction (XRD) patterns of the viologen-based defective carbon nitride composite material DCSeV-Pt-CN provided in Example 3 of this invention before and after photocatalytic cycling.

[0033] Figure 18 The graph shows the hydrogen production rate data of the viologen-based defective carbon nitride composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) provided in Examples 3-4 and Comparative Examples 3-4 of this invention.

[0034] Figure 19 The graph shows the hydrogen production rate and benzylamine oxidation rate of the viologen-based defective carbon nitride composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) provided in Examples 3-4 and Comparative Examples 3-4 of the present invention. Figure 20 This is a schematic diagram of the molecular structure of the viologen-based defective carbon nitride composite material DCSeV-Pt-CN provided in Example 3 of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0037] The present invention will now be described in further detail with reference to the accompanying drawings: I. Examples of Synthesis of Viologen Compounds Example 1: Synthesis of dicarboxylated selenium viologen (DCSeV) The chemical reaction formula of the dicarboxylated selenium violet DCSeV provided in this embodiment is as follows:

[0038] Compound 6 (234 mg, 1 mmol) and compound 7 (856 mg, 4 mmol) were weighed and dissolved separately in dry, degassed DMF (20 mL). The mixture was heated to 70 °C and stirred for 2 days, and the reaction was cooled to room temperature. The precipitate was separated by vacuum filtration and washed at least three times with DMF (10 mL) and DCM (10 mL), respectively. The precipitate was collected and dried to give a yellow solid, compound 2 (454 mg, yield: 90%), in 90% yield.

[0039] Nuclear magnetic resonance image of compound 2 ( 1 H NMR, DMSO- d 6,400 MHz; 13 C NMR, DMSO- d (6, 100 MHz) See appendix Figure 1-2 As shown, combined with mass spectrometry (MS) detection, the structural formula of compound 2 was determined to be... Compound 2 was named DCSeV.

[0040] Example 2: Synthesis of monocarboxyl selenoid viologen BCSeV The monocarboxyl-containing selenium violet BCSeV provided in this embodiment has the following specific chemical reaction formula:

[0041] Compound 9 (324 mg, 1 mmol) and compound 7 (237 mg, 4 mmol) were dissolved separately in 20 mL of dry, degassed DMF. The mixture was heated to 70°C and stirred for 48 hours. After the reaction was complete, the mixture was cooled to room temperature. The precipitate was separated by vacuum filtration and washed successively with DMF (10 mL × 3) and dichloromethane (10 mL × 3). The precipitate was collected and dried under vacuum at 40°C for 12 hours to give the yellow solid product compound 4 in 88% yield. NMR spectrum of compound 4 ( 1 H NMR, DMSO- d 6,400 MHz; 13 C NMR, DMSO- d (6, 100 MHz) See appendix Figure 3-4 As shown, combined with mass spectrometry (MS) detection, the structural formula of compound 4 was determined to be... Compound 4 was named BCSeV.

[0042] Comparative Example 1: Synthesis of Dicarboxyloviolet DCV The specific preparation process of the dicarboxylic viologen DCV provided in Comparative Example 1 is as follows:

[0043] Compound 5 and compound 7 were added to dried and degassed dimethylformamide (DMF) at a molar ratio of 1:4. The mixture was stirred under heating and allowed to react at approximately 70 °C for a certain period of time to form a precipitate. After the reaction was complete, the mixture was cooled to room temperature, and the precipitate was separated by vacuum filtration. The precipitate was then washed 3–5 times with DMF and dichloromethane (DCM) to remove unreacted substances and impurities. The resulting solid was then dried to give a pale yellow solid product 1. The structural formula of compound 1 was determined to be: .

[0044] Comparative Example 2: Synthesis of Selenium Violet BnSeV According to patent report (ZL 202010252156.4), the preparation of the selenium-containing viologen compound BnSeV has the following structural formula:

[0045] II. Preparation Examples of Violet-based Defective Carbon Nitride Composite Materials Example 3: Preparation of DCSeV-Pt-CN composite material (1) Preparation of defective graphitic carbon nitride g-C3N4 15 g of urea was dissolved in 150 mL of deionized water and stirred for 1 hour until completely dissolved. The solution was then transferred to a covered alumina crucible and placed in a muffle furnace for calcination in air. The heating program was as follows: the temperature was increased to 550 °C at a rate of 5 °C / min and held at 550 °C for 4 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature to obtain a pale yellow solid, which was defective graphitic carbon nitride g-C3N4.

[0046] See Figure 5 The image shown is a scanning electron microscope image of the defective graphitic carbon nitride composite material of the present invention. It can be seen that the material has a porous and wrinkled morphology formed by stacking two-dimensional sheets. The sheets are interwoven and connected to each other, forming an open and irregular three-dimensional network structure.

[0047] See Figure 6 A comparison of elemental analysis results between defect-free carbon nitride and carbon-defective carbon nitride was conducted. The C / N mass ratio calculated using the mass fractions of carbon (C) and nitrogen (N) showed that the C-CN ratio (0.544) for defective carbon nitride was significantly lower than the C / N ratio (0.560) for bulk-CN (defect-free carbon nitride). This decrease in the C / N ratio directly confirms that the present invention successfully introduced carbon defects into carbon nitride. The generation of carbon defects is usually accompanied by a relative increase in nitrogen content and the formation of carbon vacancies. This not only modulates the electronic structure of the material and enhances light absorption but also provides more active sites and improves charge separation efficiency, thus laying the foundation for subsequent loading of single-atom Pt and construction of an efficient "electron bridge" interface.

[0048] (2) Preparation of defective graphitic carbon nitride g-C3N4 (Pt-CN) deposited by single-atom platinum deposition 150 mg of defective graphitic carbon nitride g-C3N4 prepared in step (1) was uniformly dispersed in 40 mL of deionized water and stirred for 30 min. 4 mg of H2PtCl6·6H2O (platinum source) was added to the dispersion, and stirring was continued for 10 min to ensure homogeneity. The mixture was then placed under a 300 W xenon lamp (equipped with a λ>400 nm filter, light intensity 100 mW·cm). -2 Irradiation for 2 h was carried out for photodeposition reaction; after the reaction was completed, the reaction solution was heated at 90℃ to remove water, and carbon-deficient g-C3N4 with single-atom platinum deposition was obtained, named Pt-CN.

[0049] See appendix Figure 7The image is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of defective graphitic carbon nitride g-C3N4 (Pt-CN) deposited by single-atom platinum in this invention. A large number of bright and isolated white bright spots can be clearly observed. These are single-atom signals of Pt with high atomic numbers. Pt atoms are uniformly dispersed throughout the field of view. No larger bright spots or particles formed by agglomeration are observed, which directly proves that Pt is in an atomic-level dispersion state on the support.

[0050] See Figure 8 The X-ray absorption fine structure (XAFS) spectrum analysis of the Pt-CN prepared in this embodiment confirms that Pt is anchored on the carbon nitride support in the form of single atoms through Pt-N bonds, ruling out the formation of Pt nanoparticles or oxide clusters.

[0051] (3) Preparation of DCSeV-Pt-CN composite material Carboxyl activation: 100 mg of DCSeV prepared in Example 1 was dispersed in 5 mL of degassed anhydrous thionyl chloride (SOCl2), heated to 70 °C and stirred for 48 h under anhydrous and oxygen-free conditions; after the reaction was completed, the mixture was cooled to room temperature and the solvent was removed under reduced pressure to obtain an activated yellow powder.

[0052] Take 3 mg of the activated yellow powder and 100 mg of Pt-CN prepared in step (2), add them to 20 mL of degassed anhydrous DMF, and stir overnight (12 hours) at room temperature under argon atmosphere protection. After the reaction is completed, centrifuge to collect the precipitate, and wash it with DMF (10 mL × 3) and dichloromethane DCM (10 mL × 3) in sequence. Dry the product under vacuum at 40 °C for 12 hours to obtain DCSeV-Pt-CN composite material.

[0053] See appendix Figure 9 The infrared spectrum of DCSeV-Pt-CN confirms that a successful amidation condensation reaction occurred between the carboxyl group at the end of the DCSeV molecule and the amino group on the surface of the Pt-CN support, forming a stable diamide covalent bond. This result verifies at the molecular structure level that DCSeV is firmly grafted onto the Pt-CN surface through bilateral covalent anchoring, thereby constructing the core parallel interface and "electron bridge" structure of this study.

[0054] Example 4: Preparation of BCSeV-Pt-CN composite material Based on Examples 1-4, this embodiment provides a vizimon-based defective carbon nitride composite material BCSeV-Pt-CN with parallel interface engineering. The specific preparation steps are as follows: (1) Preparation of defective graphitic carbon nitride g-C3N4 15 g of urea was dissolved in 150 mL of deionized water and stirred for 1 hour until completely dissolved. The solution was then transferred to a covered alumina crucible and placed in a muffle furnace for calcination in air. The heating program was as follows: the temperature was increased to 550 °C at a rate of 5 °C / min and held at 550 °C for 4 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature to obtain a pale yellow solid, which was defective graphitic carbon nitride g-C3N4.

[0055] (2) Preparation of defective graphitic carbon nitride g-C3N4 (Pt-CN) deposited by single-atom platinum deposition 150 mg of carbon-deficient g-C3N4 prepared in step (1) was uniformly dispersed in 40 mL of deionized water and stirred for 30 min. 4 mg of H2PtCl6·6H2O (platinum source) was added to the dispersion, and stirring was continued for 10 min to ensure homogeneity. The mixture was then placed under a 300 W xenon lamp (equipped with a λ>400 nm filter, light intensity 100 mW·cm). -2 Irradiation for 2 h was carried out for photodeposition reaction; after the reaction was completed, the reaction solution was heated at 90℃ to remove water, and single-atom platinum-deposited defective graphitic carbon nitride g-C3N4 was obtained, named Pt-CN.

[0056] (3) Preparation of BCSeV-Pt-CN composite material Carboxyl activation: 100 mg of monocarboxyl selenoid violet BCSeV prepared in Example 2 was dissolved in 5 mL of degassed anhydrous SOCl2. The mixture was heated to 70 °C and stirred overnight for 48 h in an anhydrous and oxygen-free environment. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed under reduced pressure to obtain an activated yellow powder.

[0057] 2.74 mg of activated yellow powder and 100 mg of Pt-CN prepared in Example 3 were added to 20 mL of degassed anhydrous DMF and stirred overnight (12 h) at room temperature under argon atmosphere. After the reaction was completed, the product was collected by centrifugation and washed successively with DMF (10 mL × 3) and DCM (10 mL × 3). The product was dried under vacuum at 40 °C for 12 h to obtain the composite material BCSeV-Pt-CN of compound 4 and Pt-CN.

[0058] Comparative Example 3: Preparation of DCV-Pt-CN Composite Material Comparative Example 3, based on Comparative Example 1, provides a viologen-based defective carbon nitride composite material, the specific preparation process of which is as follows: (1) Preparation of defective graphitic carbon nitride g-C3N4 15 g of urea was dissolved in 150 mL of deionized water and stirred for 1 hour until completely dissolved. The solution was then transferred to a covered alumina crucible and placed in a muffle furnace for calcination in air. The heating program was as follows: the temperature was increased to 550 °C at a rate of 5 °C / min and held at 550 °C for 4 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature to obtain a pale yellow solid, which was defective graphitic carbon nitride g-C3N4.

[0059] (2) Preparation of defective graphitic carbon nitride g-C3N4 (Pt-CN) deposited by single-atom platinum deposition 150 mg of carbon-deficient g-C3N4 prepared in step (1) was uniformly dispersed in 40 mL of deionized water and stirred for 30 min. 4 mg of H2PtCl6·6H2O (platinum source) was added to the dispersion, and stirring was continued for 10 min to ensure homogeneity. The mixture was then placed under a 300 W xenon lamp (equipped with a λ>400 nm filter, light intensity 100 mW·cm). -2 Irradiation for 2 h was carried out for photodeposition reaction; after the reaction was completed, the reaction solution was heated at 90℃ to remove water, and a solid product was obtained, named Pt-CN.

[0060] (3) Preparation of DCV-Pt-CN composite material Carboxyl activation: 100 mg of DCV prepared in Example 3 was dissolved in 5 mL of degassed anhydrous SOCl2. The mixture was heated to 70 °C and stirred overnight (48 h) under anhydrous and oxygen-free conditions. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed under reduced pressure to obtain a yellow powder.

[0061] Take 2.54 mg of the activated yellow powder and 100 mg of Pt-CN prepared in step (2), add them to 20 mL of degassed anhydrous DMF, and stir overnight (12 h) at room temperature under argon atmosphere protection. After the reaction is completed, centrifuge to collect the precipitate, and wash it with DMF (10 mL × 3) and DCM (10 mL × 3) in sequence. Finally, vacuum dry at 40 °C for 12 h to obtain the composite material DCV-Pt-CN of compound 1 and Pt-CN.

[0062] Comparative Example 4: Preparation of BnSeV-Pt-CN composite material Comparative Example 4, based on Comparative Example 2, provides a viologen-based defective carbon nitride composite material, the specific preparation process of which is as follows: 2.48 mg of BnSeV and 100 mg of Pt-CN prepared in Example 4 were dispersed in 20 mL of degassed anhydrous DMF and stirred overnight (12 hours) at room temperature under an argon atmosphere. After the reaction was completed, the precipitate was collected by centrifugation and washed with DMF and DCM in sequence. The product was dried under vacuum at 40 °C for 12 hours to obtain viologen-based defective carbon nitride composite material BnSeV-Pt-CN.

[0063] III. Photocatalytic Performance Testing of Composite Materials The viologen compound and viologen-based defective carbon nitride composite material prepared by this invention were subjected to relevant tests. Specific test results are shown in the appendix. Figure 10-20 .

[0064] (1) Violet compound test The four viologen compounds (DCSeV, BCSeV, DCV, BnSeV) prepared in Examples 1-2 and Comparative Examples 1-2 were individually tested for photocatalytic hydrogen evolution. The standard test system contained 4 μmol of viologen compound, 1 mg of PVP-Pt as a co-catalyst, 100 mg of EDTMP sacrificial agent, and 5 mL of sodium acetate buffer. After the reaction flask was thoroughly degassed with argon, it was irradiated with a 300 W xenon lamp (λ>400 nm, light intensity 100 mW·cm). -2 The reaction was carried out for 24 hours. Hydrogen production was monitored periodically by gas chromatography. The test results showed that all four viologen compounds exhibited certain hydrogen evolution activity, with the order of hydrogen production performance being: DCSeV>BnSeV>DCV≈BCSeV. Among them, DCSeV showed the best hydrogen production performance.

[0065] See appendix Figure 10 The photocurrent time response curves (it curves) of four viologens (DCSeV, BCSeV, DCV, BnSeV) are shown. All samples exhibit repeatable transient photocurrent responses. Among them, DCSeV has the highest photocurrent response intensity, indicating that it has the most efficient photogenerated charge separation efficiency and the slowest charge recombination rate. Together, they indicate that DCSeV is the electronic medium with the best overall optoelectronic performance, laying the foundation for the subsequent construction of an efficient "electron bridge".

[0066] See appendix Figure 11 The electrochemical impedance spectroscopy (EIS) spectra of four viologens (DCSeV, BCSeV, DCV, BnSeV) show that all samples exhibit a distinct semicircular arc, the radius of which reflects the charge transfer resistance. R ct Among the various impedance parameters, DCSeV has the smallest impedance radius, indicating that it has the smallest charge transfer resistance and the most efficient interface charge transport capability.

[0067] (2) Performance testing of viologen-based defective carbon nitride composite materials The photocatalytic hydrogen evolution performance and energy of the viologen-based defective carbon nitride composites prepared in Examples 3-4 and Comparative Examples 3-4 under visible light were systematically evaluated. The specific test methods and results are as follows: The photocatalytic hydrogen evolution performance of the composite material was tested in a 20 mL Pyrex reaction flask. During the test, 2 mg of the DCSeV-Pt-CN composite material prepared in Example 3, 100 mg of ethylenediaminetetramethylenephosphonic acid (EDTMP) as a sacrificial agent, and 5 mL of sodium acetate buffer (0.03 M Hac + 0.07 M NaAc, pH≈4.5) were added sequentially. After sealing the reaction flask, argon gas was purged in the dark for 30 min to purge air, followed by the injection of 100 μL of methane as an internal standard gas. The reaction flask was placed under a 300 W xenon lamp (equipped with a λ>400 nm filter, light intensity 100 mW·cm). -2 The reaction was carried out under constant temperature magnetic stirring (25℃) with irradiation. During the reaction, 200 μL of gas from the top of the reactor was extracted every 1 h using a gas-tight syringe and analyzed by a gas chromatograph (Shimadzu GC-2014ATF / SPL) equipped with a thermal conductivity detector. The hydrogen production was calculated based on the peak area ratio of hydrogen to methane. Under optimal conditions (DCSeV loading of 3 wt%), the DCSeV-Pt-CN catalyst exhibited excellent photocatalytic hydrogen evolution activity, with a hydrogen evolution rate of 3231.9 μmol·h⁻¹. -1 ·g -1 It is a simple Pt-CN catalyst (417.9 μmol·h⁻¹). -1 ·g -1 The hydrogen production rate was 7.7 times that of light. The switching experiment showed that hydrogen generation was entirely dependent on light, confirming the light-driven nature of the reaction.

[0068] Appendix Figure 12 The photocurrent time response (it) curves of the composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) prepared in Examples 3-4 and Comparative Examples 3-4 of this invention, as well as the reference sample Pt-CN, are shown. All samples generate repeatable transient photocurrents. Only the intrinsic photocurrent response of Pt-CN loaded with single-atom Pt is weak, indicating that its charge separation ability is limited. However, after introducing viologen as an electron mediator, the photocurrent of all composite materials is significantly enhanced, which confirms the key role of viologen as an electron bridge in promoting charge separation. Among them, the photocurrent intensity of DCSeV-Pt-CN is the most prominent, indicating that it has the best photogenerated charge separation and interface transport efficiency.

[0069] Appendix Figure 13The electrochemical impedance spectroscopy (EIS) spectra of the composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, BnSeV-Pt-CN) prepared in Examples 3-4 and Comparative Examples 3-4 of this invention, as well as the reference sample Pt-CN, are shown. Unmodified Pt-CN exhibits the largest radius of curvature, indicating the highest interfacial charge transfer resistance and limited charge separation and transport efficiency. After the introduction of viologen molecules, the impedance of all composite materials significantly decreased, demonstrating that viologen effectively promotes interfacial charge transfer as an electron mediator. Among them, DCSeV-Pt-CN has the smallest impedance radius of curvature, indicating the lowest charge transfer resistance and the most efficient interfacial electron transport capability.

[0070] Appendix Figure 14 Electron paramagnetic resonance (EPR) spectra of the viologen-based defective carbon nitride composite material DCSeV-Pt-CN prepared in Example 3 of this invention under different illumination times. In darkness (0 s), no obvious EPR signal was detected in the sample. With increasing illumination time, a symmetrical single-peak signal appeared at g = 2.0055, and the signal intensity significantly increased with illumination time. This g value is close to the free electron g factor (2.0023), indicating that the signal originates from photoinduced organic free radical species, namely the free radical cations of viologen DCSeV. This result directly confirms that DCSeV-Pt-CN can undergo efficient photogenerated charge separation under illumination conditions and stably generate and accumulate free radical intermediates in air, providing crucial paramagnetic resonance evidence for the electron transfer process in its photocatalytic reaction.

[0071] Appendix Figure 15 The cumulative hydrogen production of the composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, and BnSeV-Pt-CN) prepared in Examples 3-4 and Comparative Examples 3-4 of this invention over 48 hours is demonstrated. The hydrogen production performance of the composite materials (BnSeV-Pt-CN, DCV-Pt-CN, BCSeV-Pt-CN, and DCSeV-Pt-CN) with viologen electron mediators is significantly higher than that of unmodified Pt-CN, indicating that the introduction of viologen effectively enhances the photocatalytic activity of the system. Among them, DCSeV-Pt-CN shows the most outstanding performance, with a cumulative hydrogen production of approximately 188.2 μmol over 48 hours, the highest among all samples. This excellent performance is attributed to its unique bilateral covalently bonded parallel "electron bridge" structure, which provides a stable, short-range, and efficient electron transfer channel, greatly promoting the transfer of photogenerated electrons from g0.05 to g0.05. C3N4 significantly improves photocatalytic hydrogen production efficiency by directional migration to Pt active sites via DCSeV. This result directly confirms the key role of parallel interface engineering in optimizing charge flow and improving photocatalytic performance.

[0072] Appendix Figure 16 The results show the cyclic hydrogen production stability test results of the composite materials (DCSeV-Pt-CN, BCSeV-Pt-CN, DCV-Pt-CN, and BnSeV-Pt-CN) prepared in Examples 3-4 and Comparative Examples 3-4 of this invention. After six cycles totaling 144 hours, the hydrogen production activity of BnSeV-Pt-CN bound by electrostatic adsorption and BCSeV-Pt-CN covalently linked only on one side showed significant decay after the first few cycles, with final activity losses of approximately 83.7% and 85.3%, respectively, indicating that their interfacial structures have severely insufficient stability under long-term light and reaction conditions. In contrast, the bilaterally covalently anchored DCSeV-Pt-CN exhibited excellent cyclic stability, maintaining its hydrogen production activity at over 92% of its initial value after six cycles, with a decay of less than 8%. This result directly confirms that the parallel "electron bridge" structure in DCSeV-Pt-CN possesses excellent mechanical and chemical stability. The covalent bonding of the diamide effectively locks the interfacial configuration, preventing the loss or deactivation of electron mediators during the reaction process, thereby ensuring the long-term unobstructed flow of photogenerated electron channels and the sustained and efficient operation of the catalytic system. This conclusion further emphasizes the crucial significance of interfacial covalent engineering for realizing durable photocatalysts.

[0073] Appendix Figure 17 The X-ray diffraction (XRD) patterns of the parallel-interface engineered viologen-based defective carbon nitride composite material DCSeV-Pt-CN prepared in Example 4 of this invention are shown before and after photocatalytic cycling. The characteristic diffraction peak positions and intensities of the samples did not change significantly before and after the reaction, indicating that the basic crystal structure of the material remained stable during the long-term photocatalytic reaction, without phase transition or structural collapse. This result confirms that the "electron bridge" interface constructed through bivalent bonds has good structural durability, ensuring the long-term operational stability of the catalyst.

[0074] Appendix Figure 18 The graph shows the hydrogen production rate data of the composite materials (BnSeV-Pt-CN, DCV-Pt-CN, BCSeV-Pt-CN, and DCSeV-Pt-CN) prepared in Examples 4-6 and Comparative Example 2 of this invention. The BnSeV-Pt-CN composite material bonded by electrostatic interaction, the BCSeV-Pt-CN composite material with unilateral covalent bonding, and the DCSeV-Pt-CN composite material constructed with bilateral covalent bonding all exhibited superior hydrogen production activity compared to pure Pt-CN. Among them, the DCSeV-Pt-CN composite material constructed with bilateral covalent bonding exhibited the best photocatalytic hydrogen production performance, with a hydrogen production rate reaching 3231.9 μmol·h⁻¹. -1 ·g -1The efficiency is significantly higher than that of other composite materials. This result clearly confirms that the stable "electron bridge" interface structure constructed by anchoring viologen DCSeV in a parallel configuration on the surface of a single-atom platinum-modified defective carbon nitride (Pt-CN) support through diamide covalent bonds, as described in this invention, can most effectively promote the directional and rapid transport of photogenerated electrons from the support to the catalytic site, thereby achieving extremely high photocatalytic hydrogen production efficiency.

[0075] Appendix Figure 19 The graphs show the hydrogen production rates and benzylamine oxidation rates of the composite materials BnSeV-Pt-CN, DCV-Pt-CN, BCSeV-Pt-CN, and DCSeV-Pt-CN prepared in Examples 4-6 and Comparative Example 2 of this invention. In the coupled reaction system, all composite materials exhibited bifunctional catalytic activity. Among them, the DCSeV-Pt-CN composite material constructed through bilateral covalent bonding showed the highest overall performance, with a hydrogen production rate of 394.9 μmol·h⁻¹. -1 ·g -1 The oxidation rate of benzylamine reached 1390.6 μmol·h⁻¹. -1 ·g -1 This significantly outperforms both the electrostatically bonded BnSeV-Pt-CN and the unilaterally covalently bonded BCSeV-Pt-CN. This result directly confirms that the parallel "electron bridge" interface structure constructed through bilateral covalent anchoring in this invention can simultaneously and efficiently guide photogenerated electrons and holes to their respective catalytic sites in complex bifunctional reaction systems: electrons are efficiently transferred to single-atom Pt sites for proton reduction to produce hydrogen, while holes are effectively used to drive the selective oxidation of benzylamine. This structure achieves efficient spatial separation and synergistic utilization of photogenerated charges, which is key to obtaining high-performance, multifunctional coupled photocatalytic systems.

[0076] See appendix Figure 20 This diagram illustrates the molecular structure of the DCSeV-Pt-CN composite material provided by this invention. It clearly demonstrates the core "parallel interface engineering" design of this invention: the dicarboxylated selenium-containing viologen (DCSeV) is stably anchored parallel to the surface of the defective carbon nitride (CN) support via covalent amide bonds on both sides, while a single-atom platinum (Pt) catalytic site is loaded on the support surface. The bivalent bond structure formed between the viologen molecule and the support surface constructs a stable, short-range, and highly efficient "electron bridge" interface, providing a structural basis for the directional and rapid transport of photogenerated electrons from the carbon nitride support to the single-atom platinum catalytic site. This parallel configuration maximizes the electronic coupling between the viologen conjugated system and the support surface, significantly enhancing interfacial bonding and electron transport efficiency, and is a key structural feature for achieving the excellent photocatalytic performance of this invention.

[0077] The DCSeV-Pt-CN catalyst underwent a long-term stability test for six consecutive cycles (24 h per cycle, totaling 144 h). After each cycle, the catalyst was recovered by centrifugation, washed, dried, and reused in the next reaction. The hydrogen evolution test method was the same. Thanks to the robust parallel interface constructed by bivalent bonds, DCSeV-Pt-CN exhibited excellent cycle stability: after six cycles, its hydrogen evolution activity remained above 92% of the initial activity. In contrast, the BnSeV-Pt-CN complex bound only by electrostatic adsorption experienced an activity decline of 82%, and the BCSeV-Pt-CN complex with single-point covalent bonding experienced an activity decline of 84%, fully demonstrating the key role of the parallel interface engineering strategy adopted in improving catalyst durability. XRD characterization of the catalyst after the cycle reaction showed no significant shift or weakening of its crystal structure characteristic peaks, further confirming the integrity of the catalyst's framework structure during long-term photocatalysis.

[0078] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A parallel interface engineered melanin-based defective carbon nitride composite material, characterized in that, Comprise: a defective graphitic carbon nitride support; a single-atom platinum catalytic site supported on the defective graphitic carbon nitride support; and a selenium-containing viologen compound anchored on the surface of the single-atom platinum modified defective graphitic carbon nitride support through a covalent bond; wherein the selenium-containing viologen compound is fixed on the support in a configuration parallel to the surface of the support.

2. A parallel interface engineered, purpurin-based, defective carbon nitride composite material according to claim 1, wherein, The defective graphitic carbon nitride support is a graphitic carbon nitride subjected to a defect engineering treatment, and the defects include at least one of nitrogen vacancies, carbon vacancies, or cyano defects.

3. The parallel interface engineered melanin-based defective carbon nitride composite material of claim 1, wherein, The selenium-containing viologen compound is any one of a monocarboxyl selenium-containing viologen and a dicarboxyl selenium-containing viologen.

4. The parallel interface engineered viologen-based defective carbon nitride composite material according to claim 3, characterized in that, the monocarboxyl selenium-containing viologen has a structure as shown in formula (I) wherein R is any one of methyl, phenyl, benzyl; The structural formula of the dicarboxyl selenium-containing viologen is: .

5. A method of preparing a parallel interface engineered prussian-based defect carbon nitride composite material according to any one of claims 1-4, characterized in that, comprise the following steps: (1) preparing a defective graphitic carbon nitride support; (2) dispersing the defective graphitic carbon nitride support, adding a platinum source, irradiating the reaction with a xenon lamp, removing water by heating, and obtaining a defective graphitic carbon nitride support with single-atom platinum deposition; (3) under argon protection, stirring and reacting the viologen compound with the defective graphitic carbon nitride support with single-atom platinum deposition, washing, vacuum drying, and obtaining a parallel interface engineered viologen-based defective carbon nitride composite material.

6. The method for preparing viologen-based defective carbon nitride composite material with parallel interface engineering according to claim 5, characterized in that, Step (1) specifically includes calcining a urea solution at 500 ℃ to 600 ℃ in an air atmosphere for 2 h to 6 h, and naturally cooling to room temperature.

7. The method for preparing viologen-based defective carbon nitride composite material with parallel interface engineering according to claim 5, characterized in that, In step (2), the mass ratio of the defective graphitic carbon nitride support to the platinum source is (20-50):1, the xenon lamp irradiation time is 1 h to 3 h, and the platinum source is H2PtCl6·6H2O or potassium chloroplatinate.

8. The method for preparing viologen-based defective carbon nitride composite material with parallel interface engineering according to claim 5, characterized in that, In step (3), the mass ratio of the selenium-containing viologen compound to the defective graphitic carbon nitride support with single-atom platinum deposition is 1:(10-100), and the reaction is carried out at room temperature for 6 h to 24 h.

9. Use of the parallel interface engineered viologen-based defective carbon nitride composite material according to any one of claims 1-4 in photocatalytic hydrogen production.

10. A photocatalytic reaction system, characterized by comprising: The parallel interface engineered viologen-based defective carbon nitride composite material according to any one of claims 1-4 is dispersed in a reaction medium in the form of a powder, and is used in a photocatalytic hydrogen evolution reaction or an organic oxidation reaction under visible light driving.

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