Graphite diacetylene / copper oxide composite material cocatalyst and co-production preparation process and application thereof

Abstract

The invention discloses a graphite diacetylene / copper oxide composite material cocatalyst and a co-production preparation process and application thereof. Graphite diyne has a two-dimensional layered structure and is composed of sp and sp hybridized carbon atoms, a periodically distributed structure is formed, and excellent electron transmission performance and pore structure are shown. An existing graphite diacetylene synthesis method is complex and high in cost, large-scale application of the graphite diacetylene in the industrial field is seriously restricted, the potential value of a copper catalyst cannot be fully exerted, and resource waste is caused. According to the invention, through a simple and efficient co-production process, co-production of graphite diyne and copper oxide nanoparticles is realized for the first time, and the graphite diyne / copper oxide composite material is successfully prepared. The novel composite material can be used as a cocatalyst to effectively improve photocatalytic hydrogen production, and the hydrogen production performance can be comparable with that of noble metal photocatalysts such as Pt. The problems of tedious steps, high energy consumption, low yield and the like in a traditional preparation method are solved, and the preparation method has important application value in the field of high-performance photocatalysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterial preparation, and particularly relates to a graphite diyne / cupric oxide composite cocatalyst, a co-production preparation process thereof, and an application thereof in photocatalytic hydrogen production. Background Art

[0002] Graphite diyne is a new carbon material composed of sp- and sp²-hybridized carbon atoms, with a natural band gap, uniform pore structure, large specific surface area, excellent carrier mobility and conductivity, showing great application potential in the field of photocatalysis.

[0003] The synthesis method of graphite diyne has high technical complexity and cost, seriously restricting its large-scale application in the industrial field. Currently, the graphite diyne materials used for photocatalysis are mainly prepared by the following steps: Since hexaethynylbenzene (HEB) is easily oxidized, hexa-[(trimethylsilyl)ethynyl]benzene (HEB-TMS) is used as a precursor, deprotected to HEB under an inert gas, and then prepared through steps such as copper sheet coupling polymerization and mechanical exfoliation. The detailed method is described as follows: Step 1: Deprotection of HEB-TMS Reaction process: HEB-TMS is deprotected by tetrabutylammonium fluoride to remove the trimethylsilyl (TMS) protecting group at 0 °C under an inert atmosphere (such as nitrogen or argon), extracted with ethyl acetate, and rotary evaporated to obtain hexaethynylbenzene (HEB). Key conditions: The temperature and atmosphere need to be strictly controlled to avoid side reactions caused by oxygen or moisture.

[0004] Step 2: Coupling reaction on the copper substrate surface Reaction process: A pyridine solution of HEB is uniformly dropped into a pyridine solution containing copper foil, and a surface coupling reaction is carried out at 60 °C using a copper catalyst to form graphite diyne. Key conditions: The reaction needs to be carried out under an inert atmosphere, and the flatness of the substrate surface affects the synthesis efficiency and quality.

[0005] Step 3: Mechanical exfoliation Reaction process: The synthesized graphite diyne is exfoliated from the copper substrate by mechanical force (such as scratching, ultrasonic exfoliation, etc.) to obtain graphite diyne powder. Key conditions: The exfoliation process needs to be precisely controlled to avoid damaging the graphite diyne structure.

[0006] Step 4: Cleaning to remove impurities Reaction process: Graphite diyne is cleaned with acetone, DMF, hydrochloric acid, etc. to remove unreacted monomers and residual copper-based catalysts. Key conditions: Multiple cleanings are required to remove impurities.

[0007] The existing processes for preparing graphite diyne materials have the following defects: (1) Complex process flow: It requires multiple steps of reactions, including deprotection, surface coupling, and stripping. The operation process is complex and requires high technical skills. The reaction conditions (such as atmosphere, temperature, and time) for each step need to be strictly controlled, otherwise, it may lead to a decrease in low yield.

[0008] (2) High economic cost: The removal of the TMS protecting group increases the raw material cost. The use of high-purity copper substrates and inert atmosphere equipment further increases the production cost.

[0009] (3) Limited large-scale preparation: The surface coupling reaction on the substrate is difficult to scale up on a large scale, the product yield is limited, and it is difficult to meet the industrial demand. The stripping step is time-consuming and inefficient, affecting batch production.

[0010] (4) Environmental and safety issues: High-reactivity alkynyl compounds need to be processed, which has certain safety hazards. The use of high temperature and pyridine solvent increases energy consumption, generates waste gas and waste liquid, and poses an environmental burden.

[0011] (5) The value of copper-based catalysts is not fully utilized: The removal of copper-based catalysts increases the production complexity and cost. Copper-based catalysts are good co-catalysts.

[0012] It can be seen that the synthesis of graphdiyne usually adopts copper-catalyzed reactions. However, in the existing technology, there are various drawbacks. Especially after the reaction is completed, the copper catalyst is generally removed and treated as waste. This method increases the complexity and cost of the production process, and also fails to fully utilize the potential value of copper catalysts, resulting in a waste of resources. Therefore, it is necessary to optimize the process of the existing synthesis method to solve the above technical problems. Summary of the Invention

[0013] As can be seen from the above, the current synthesis of graphdiyne for photocatalysis requires multiple steps of reactions, complex separation and purification steps, as well as expensive reagents and energy consumption. At the same time, the potential value of copper catalysts is not fully utilized, resulting in a waste of resources, which seriously restricts the large-scale preparation and popularization of graphdiyne in photocatalysis. In view of the above problems, the present invention provides a graphdiyne / cupric oxide composite co-catalyst, its co-production preparation process and application. The present invention aims to solve the problems of cumbersome steps, harsh reaction conditions, high energy consumption, and low yield in the traditional graphdiyne preparation method. At the same time, through a simple and efficient co-production process, the co-production of graphdiyne and cupric oxide nanoparticles is realized for the first time, and a new composite co-catalyst is successfully prepared to assist in high-performance photocatalytic hydrogen production.

[0014] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a co-production process for preparing a graphene bisacetylene / copper oxide composite catalyst, specifically using hexa-[(trimethylsilyl)ethynyl]benzene as a monomer, CuCl as a copper catalyst, and adopting an efficient reaction path without deprotection to prepare a graphene bisacetylene / copper oxide nanoparticle catalyst by a one-step method. The process steps are as follows: S1: Mixing the monomer hexa-[(trimethylsilyl)ethynyl]benzene and the copper catalyst in a certain molar ratio, dissolving them in an organic solvent, and mixing them uniformly by ultrasonication; S2: Under air conditions, react the system in step S1 at a predetermined temperature to ensure that the monomers are fully polymerized to generate graphene diacetylene; S3: After the reaction structure, the solid product is separated by centrifugation; S4: further washing with DMF, THF, and methanol to remove unreacted monomers; S5: After drying, a graphite diyne / copper oxide composite material co-catalyst is obtained.

[0015] Furthermore, the copper catalyst is CuCl; and the molar ratio of the monomer to the copper catalyst is 1:1.

[0016] Furthermore, in step S2, the reaction temperature is 60-70°C and the reaction time is 20-24h; Furthermore, the organic solvent in step S1 is DMF, which is used to provide good solubility and reaction environment.

[0017] On the other hand, the present invention also proposes a graphene diyne / copper oxide composite material catalyst co-catalyst obtained by the above-mentioned co-production preparation process.

[0018] In a third aspect, the present invention also proposes the use of the above-mentioned graphene diacetylene / copper oxide composite material co-catalyst in photocatalytic hydrogen production, which exhibits excellent photocatalytic hydrogen production activity.

[0019] The technical route of the present invention has the following significant advantages: (1) Simplified process: No need for multi-step synthesis and complex separation and purification operations in traditional methods, it can be obtained by one-step reaction in air; (2) High yield: The reaction yield reaches 100%; (3) Environmentally friendly: Avoids excessive consumption of chemical reagents and generation of by-products; (4) Full utilization of copper-based catalysts: Graphene diacetylene / copper oxide nanoparticles are prepared by a one-step method, which exhibits excellent photocatalytic hydrogen production activity, comparable to that of precious metal Pt co-catalysts.

[0020] In summary, this method not only has extremely high innovation in academic research, but also provides a feasible path for the large-scale preparation of graphdiyne and its photocatalytic applications, with significant industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the co-production synthesis process of the graphdiyne / CuO composite cocatalyst of the present invention; Figure 2 Mechanism diagram for the preparation of graphdiyne / CuO by the one-step method without deprotection; Figure 3 High-resolution Cu 2p spectrum of graphdiyne / CuO; Figure 4 TEM characterization diagram of the prepared graphdiyne / CuO; among which, (a) is the bright-field TEM image of graphdiyne / CuO; (b) is the particle size distribution of CuO in graphdiyne; (c, d) are the HRTEM images of CuO in graphdiyne and the enlarged view of the red box area; Figure 5 Comparison chart of hydrogen production rates based on different photocatalysts; Figure 6 Schematic diagram of the photocatalytic hydrogen production reaction mechanism. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope protected by the present invention.

[0023] As Figure 1 shown, the schematic diagram of the co-production synthesis process of the graphdiyne / CuO composite cocatalyst of the present invention; the specific preparation process is as follows: Step 1: Take 16.8 mg of hexa-[(trimethylsilyl)ethynyl]benzene and 2.4 mg of CuCl and mix them in a molar ratio of 1:1, then dissolve them in 2 - 3 ml of DMF solution and ultrasonically mix evenly; Step 2: Under air conditions, heat at 60 °C for 24 hours to ensure that the monomers are fully polymerized to form graphdiyne; Step 3: After the reaction is completed, centrifuge to separate the solid product; Step 4: Further wash with DMF, THF, and methanol to remove unreacted monomers; Step 5: After drying, obtain the graphdiyne / CuO nanoparticle composite material.

[0024] Reference Figure 1 and Figure 2 In the specific co-production process, HEB-TMS first reacts with CuCl to form an intermediate, presumably a monovalent copper (I) species, and then undergoes a reductive elimination reaction during the formation of the butyne bridge to generate zero-valent copper (0). The generated zero-valent copper (0) will be further oxidized to monovalent copper (I) in the presence of air to enter the next catalytic cycle. At the same time, a part of the copper (I) is also oxidized to divalent copper (II). In this mechanism, trimethylsilyl chloride (TMS-Cl) is generated and then converted to TMS-OH and TMS-O-TMS ( Figure 2 ). The prepared graphdiyne / cupric oxide nanoparticles are in powder form and the color is dark black or grayish black; it is confirmed by characterizations such as XRD, TEM, and X-ray photoelectron spectroscopy that the CuO nanoparticles are uniformly distributed on the surface of graphdiyne; Figure 3 Figure Figure 4 a is the TEM characterization diagram of the prepared graphdiyne / cupric oxide. It can be clearly observed that the nanoparticles are loaded on the graphyne, and the average particle size is ~2.9 nm ( Figure 4 b). The nanoparticles exhibit a crystalline phase, which can be attributed to cubic CuO (space group = Fm3m), a = b = c = 4.2450 Å ( Figure 4 c-d). The lattice spacings are 0.245 nm, 0.217 nm, and 0.245 nm, corresponding to the (1-1-1), (200), and (111) planes of cubic CuO ( Figure 4 d), which is consistent with the theoretical simulation and XRD results.

[0025] In summary, the present invention directly uses hexa-[(trimethylsilyl)ethynyl]benzene (HEB-TMS) as a monomer, and the trimethylsilyl (TMS) protecting group is automatically removed during the reaction process without the need for an additional deprotection step; CuCl catalyzes the self-assembly polymerization of the monomer under mild conditions to generate graphdiyne with a highly ordered structure; the graphdiyne powder is directly obtained by a one-step method, avoiding the mechanical exfoliation step, with a simple process and high efficiency, and the yield can reach 100%; CuCl is converted into CuO nanoparticles after the reaction and is firmly loaded on the surface of graphdiyne or embedded in its structure.

[0026] The technical solution of the present invention has the following innovations (1) Process innovation of the deprotection-free method: Traditional methods require additional deprotecting agents or chemical treatments to remove the TMS protecting group. In contrast, in the present invention, by controlling the reaction temperature and catalyst selection, TMS is automatically removed during the polymerization reaction, and the monomer directly forms the target product, avoiding process complication.

[0027] (2) High yield and simplified process: The present invention achieves a 100% yield of graphdiyne through a one-step method, reducing raw material waste and post-treatment steps compared to the prior art and significantly improving the preparation efficiency.

[0028] (3) Co-production of graphdiyne and copper oxide co-catalyst: In the present invention, through a specific chemical reaction system (using hexa-[(trimethylsilyl)ethynyl]benzene as the monomer and cuprous chloride as the catalyst), the simultaneous formation of graphdiyne and copper oxide nanoparticles is achieved. Precise control of the reaction temperature, pressure, time, catalyst dosage, and precursor ratio during the co-production process ensures the simultaneous formation of graphdiyne and copper oxide nanoparticles and their ideal structural properties; the nanoparticles supported on graphdiyne have a narrow particle size distribution, with an average diameter of approximately 2.9 nm. These nanoparticles exhibit a crystal phase, which can be attributed to cubic copper oxide (space group = Fm3 m), with a lattice constant of a = b = c = 4.2450 Å. The spacings of the lattice fringes are 0.245 nm, 0.217 nm, and 0.245 nm, respectively, at 56.48° and 111.40°, corresponding to the (1-1-1), (200), and (111) crystal planes of cubic copper oxide, respectively, which is consistent with the theoretical simulation and XRD results. All of the above results indicate the successful synthesis of in-situ formed copper oxide nanoparticle / graphdiyne.

[0029] The graphdiyne / copper oxide composite material prepared by the present invention can significantly enhance the photocatalytic hydrogen production activity as a co-catalyst.

[0030] To verify the potential of the prepared graphdiyne / copper oxide (GDY / CuO) as a co-catalyst, it was hybridized with titanium dioxide (TiO2) by a physical mixing method to prepare a CuO / graphdiyne / TiO2 photocatalyst for photocatalytic hydrogen production. By adjusting the doping amount of CuO / graphdiyne, CuO / graphdiyne / TiO2 with different doping concentrations was prepared. Tests showed that when the doping amount of CuO / graphdiyne was 5% (mass fraction), CuO / graphdiyne / TiO2 exhibited the highest photocatalytic activity, with a hydrogen production rate of 18 mmol·h -1 ·g -1 . It is comparable to the state-of-the-art 0.5% Pt / TiO2 photocatalyst ( Figure 5), this study provides a method for directly synthesizing GDY / CuO powder without deprotection, opening up a new path for the novel application of graphdiyne in catalysis and other sustainable energy applications.

[0031] To better understand the photocatalytic process, we studied the optical band structure of GDY by Tauc plots and XPS valence band spectra. The direct optical band gap of GDY was determined to be ≈1.47 eV. The valence band (VB) edge of the GDY powder was further measured to be approximately 1.12 V relative to the normal hydrogen electrode (NHE). Therefore, the conduction band (CB) edge was calculated to be -0.35 V vs NHE. For TiO2, the main exposed surface (101) is considered to be the electron transfer process because this plane is non-polar and exhibits excellent performance in photoreduction reactions. The CB and VB edges of the (101) surface of TiO2 are -0.78 V and 2.92 V vs NHE, respectively. Therefore, under ultraviolet / visible light excitation, electron / hole pairs are generated on the TiO2 surface, where the electrons are located in the CB and the holes remain in the VB. Due to the appropriate band alignment between TiO2 and GDY, electrons can transfer to the CB of GDY. Then, the electrons are collected by CuO NPs and undergo multiple reductions during this process, thus forming Cu(0). Cu(0) is an effective reduction site for proton reduction and can effectively promote photocatalytic hydrogen production. Therefore, the synergistic effect of GDY and CuO as co-catalysts can effectively inhibit photoinduced carrier recombination and improve photocatalytic hydrogen production (see Figure 6).

[0032] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art of the present invention can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all of them should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A co-production preparation process of a graphite diyne / cupric oxide composite cocatalyst, characterized in that It includes the following technological steps: S1: Mix monomer hexa-[(trimethylsilyl)ethynyl]benzene and a copper catalyst in a certain molar ratio, dissolve them in an organic solvent, and ultrasonically mix them evenly; S2: Under air conditions, carry out the reaction on the system in step S1 at a predetermined temperature to ensure that the monomer is fully polymerized to form graphdiyne; S3: After the reaction structure, centrifugally separate the solid product; S4: Further wash with DMF, THF, and methanol to remove unreacted monomers; S5: Obtain the graphdiyne / cupric oxide composite cocatalyst after drying.

2. The co-production preparation process of a graphite diyne / cupric oxide composite co-catalyst according to claim 1, characterized in that, The copper catalyst is CuCl; the molar ratio of the monomer to the copper catalyst is 1:

1.

3. The co-production preparation process of a graphite diyne / cupric oxide composite co-catalyst according to claim 1, characterized in that, In step S2, the reaction temperature is 60-70°C and the reaction time is 20-24 h.

4. The co-production preparation process of a graphite diyne / cupric oxide composite cocatalyst according to claim 1, characterized in that, In step S1, the organic solvent is DMF.

5. A graphite diyne / cupric oxide composite cocatalyst, characterized in that, It is prepared by using the co-production preparation process described in any one of claims 1-4.

6. Use of a graphite diyne / cupric oxide composite cocatalyst in photocatalytic hydrogen production as described in claim 5, characterized in that, When hybridized with TiO2, when the doping amount of graphdiyne / CuO is 5 wt%, CuO / graphdiyne / TiO2 exhibits excellent photocatalytic activity, and the hydrogen generation rate is 18 mmol·h -1 ·g -1 .

Images