A method for preparing single-layer porous graphene based on laser photo-thermal-chemical etching synergy

Abstract

The application discloses a method for preparing single-layer porous graphene based on laser photo-thermal-chemical etching synergy, which comprises the following steps: adding hydrogen peroxide into a graphene oxide solution, and irradiating the obtained mixed solution under stirring by using a pulsed laser; and separating and washing the product to obtain porous graphene oxide, and then performing chemical reduction to obtain single-layer porous graphene. The method can complete the preparation of single-layer porous graphene under normal temperature and pressure conditions, significantly shortens the reaction time and improves the energy utilization efficiency; by adjusting the laser energy input parameters and the etching agent concentration, the pore generation process can be effectively controlled, and the uniformity of the pore structure distribution is ensured. The application can effectively maintain the integrity of the single-layer structure of graphene while realizing the controllable construction of nanopores, and provides a new engineering technical approach for the efficient preparation and structure performance optimization of single-layer porous graphene.

Description

Technical Field

[0001] This invention relates to the field of graphene preparation technology, specifically to a method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching. Background Technology

[0002] Graphene is composed of a single layer of carbon atoms through sp... 2 Two-dimensional crystalline materials formed by hybridization, with their excellent electrical conductivity, mechanical strength, thermal conductivity, and chemical stability, have shown broad application prospects in various fields such as energy storage devices, membrane separation, catalysis, and electrochemical sensing. However, pristine graphene, with its ideal and complete lattice structure, has inherent limitations. Its two-dimensional plane lacks effective mass transport channels, and the number of chemically active edge sites is limited, which severely restricts its performance in key application scenarios such as rapid ion diffusion, precise molecular sieving, and efficient interfacial reactions. To overcome this technical bottleneck, constructing nanoscale porous structures within the two-dimensional plane of graphene to form porous graphene (typically with pore sizes less than 50 nm) has become a core research direction in the field of graphene material modification. While retaining the excellent intrinsic properties of graphene, porous graphene significantly shortens the mass transport path through the introduction of nanopores, while greatly increasing the number of chemically active sites. This results in comprehensive performance far exceeding that of pristine graphene in applications such as supercapacitor electrodes, high-performance battery materials, high-efficiency water treatment membranes, gas separation media, and catalytic reaction supports.

[0003] Currently, the preparation of porous graphene mainly includes wet chemical etching and hydrothermal / solvothermal methods, template-assisted and sacrificial structure methods, microwave, plasma, and irradiation etching methods, as well as laser-related processing methods. Wet chemical etching relies on strong oxidants or peroxide systems, achieving etching under high temperature, high pressure, or long reaction conditions. Hydrothermal / solvothermal methods require a closed reactor with overall heating to drive the reaction. These methods generally suffer from long reaction cycles, high energy consumption, and difficulty in precisely controlling pore size and density. Furthermore, the etching process can easily lead to graphene sheet breakage, interlayer aggregation, or structural collapse. Template-assisted and sacrificial structure methods introduce hard or soft templates to form the pore structure, requiring complex steps to remove the template. This technology is not only cumbersome in its process but also suffers from template residue and environmental pollution. Moreover, it is limited by the scalability bottleneck of template preparation and removal, making it difficult to achieve mass production of porous graphene. While microwave, plasma, and irradiation etching methods can rapidly input energy to achieve localized etching, the inherent defect of uneven energy distribution easily leads to localized over-etching or under-etching, resulting in random pore structure distribution and large size dispersion, making it difficult to achieve uniform and controllable construction of nanoporous structures within a single layer of graphene. Existing laser-related processing technologies mostly focus on the reduction, macroscopic patterning, or surface modification of graphene oxide. Their energy input methods are difficult to control precisely at the atomic scale, making it impossible to achieve controllable generation of nanoporous structures within a single layer of graphene, and often accompanied by problems such as damage to the sheet structure.

[0004] In summary, existing methods for preparing porous graphene generally suffer from several shortcomings that urgently need to be addressed: most methods rely on prolonged bulk heating or high-temperature, high-pressure environments, resulting in inefficient energy utilization, low preparation efficiency, and excessive energy consumption; the pore structure formation process lacks precise and controllable energy input and reaction regulation mechanisms, making it difficult to accurately adjust pore size, pore density, and distribution uniformity, leading to poor product performance consistency; etching or processing easily causes graphene sheet breakage, interlayer overlap, or structural collapse, making it difficult to stably obtain single-layer porous graphene products and severely affecting the material's application performance; existing laser processing technology has not overcome the technical bottleneck of atomically precise pore formation, making it impossible to achieve efficient and controllable construction of intraplane nanopores in single-layer graphene under mild conditions of ambient temperature and pressure, thus hindering the industrial application of porous graphene materials. Therefore, developing a preparation method that can achieve rapid, uniform, and stable formation of intraplane nanopores in single-layer graphene under mild conditions of ambient temperature and pressure through precise and controllable energy input has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the technical problems of low preparation efficiency, high energy consumption, poor controllability of pore structure, difficulty in stably obtaining single-layer porous structures, and the inability of existing laser processing technology to achieve efficient and precise pore formation of nanopores in the plane of single-layer graphene under mild conditions of ambient temperature and pressure. This invention provides a method for preparing single-layer porous graphene based on the synergistic effect of laser photothermal-chemical etching. This method improves the energy input method and etching process, induces pore structure generation in the graphene oxide system by means of transient photothermal effect of laser, and combines it with subsequent chemical reduction treatment. Under ambient temperature and pressure, nanopore structures can be rapidly and uniformly formed in the two-dimensional plane of single-layer graphene through controllable energy input, while effectively maintaining the integrity of the single-layer graphene structure and achieving stable construction of porous structures.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching includes the following steps:

[0008] (1) Graphene oxide is dispersed in a solvent to obtain a graphene oxide solution;

[0009] (2) Hydrogen peroxide is added to the graphene oxide solution, and the volume fraction of hydrogen peroxide in the resulting mixed solution is 0.1%-0.3%;

[0010] (3) Under stirring conditions, the mixed solution is irradiated with a pulsed laser. After the treatment, the product is separated and cleaned to obtain porous graphene oxide. The parameters of the pulsed laser are: single pulse width of 5-20 ns, pulse energy of 40-120 mJ, and pulse frequency of 5-50 Hz.

[0011] (4) The porous graphene oxide is chemically reduced to obtain the single-layer porous graphene.

[0012] This invention achieves efficient construction of nanoporous structures within a two-dimensional plane of monolayer graphene through the synergistic regulation of laser photothermal effects and chemical etching. The underlying principle is as follows: The presence of numerous oxygen-containing functional groups (hydroxyl, epoxy, and carboxyl groups) in graphene oxide sheets creates localized lattice defects, which become active sites for the etching reaction. In this invention, pulsed laser irradiation serves as a precise energy input method. The energy is rapidly absorbed by the graphene oxide, but instead of causing a general temperature rise, it creates a highly localized transient, unstable high-temperature environment within a nanosecond timescale. This localized high temperature, on the one hand, activates the structure of localized areas of the graphene oxide sheets, reducing the binding energy between carbon atoms and creating thermodynamic conditions for selective etching; on the other hand, it promotes the rapid decomposition of hydrogen peroxide in the system, generating highly oxidizing reactive species such as hydroxyl radicals. Unlike traditional wet chemical etching, where active species diffuse randomly and are etched indiscriminately, the laser-induced local high-temperature field in this invention causes active species to preferentially react with activated carbon atoms in an oxidative etching reaction, achieving selective removal of carbon atoms in the two-dimensional plane of monolayer graphene oxide, thereby rapidly forming a nanoscale porous structure within the substrate.

[0013] Compared with existing technologies, the method of this invention can prepare monolayer porous graphene under ambient temperature and pressure conditions, significantly shortening the reaction time and improving energy utilization efficiency. By adjusting the laser energy input parameters and etchant concentration, the pore formation process can be effectively controlled, ensuring that the resulting pore size is stable below 50 nm while maintaining the uniformity of the pore structure distribution. This invention achieves controllable construction of nanopores while effectively maintaining the integrity of the monolayer graphene structure, providing a new engineering approach for the efficient preparation and structural and performance optimization of monolayer porous graphene.

[0014] Furthermore, in step (1), the solvent is water.

[0015] Further, in step (1), the concentration of the graphene oxide solution is 0.1-0.5 mg / mL.

[0016] Further, in step (1), a graphene oxide solution is obtained by ultrasonic dispersion treatment, with an ultrasonic frequency of 35-40 kHz and an ultrasonic time of 30-60 min.

[0017] Furthermore, in step (1), graphene oxide is dispersed in a solvent and subjected to ultrasonic or mechanical stirring to fully peel off and form a uniformly dispersed and stable graphene oxide solution, so as to ensure that the graphene oxide sheets exist in the solution in a single layer or few layers.

[0018] Further, in step (2), an aqueous solution of hydrogen peroxide is added to the graphene oxide solution so that the volume fraction of hydrogen peroxide in the mixed solution is 0.1%-0.3%.

[0019] Furthermore, in step (3), the stirring is carried out by magnetic stirring, and the rotor speed is 300-600 r / min.

[0020] Furthermore, in step (3), the pulsed laser is preferably a nanosecond pulsed laser. This invention uses a nanosecond pulsed laser, which has the characteristics of short energy loading time and high peak power: the short pulse characteristic avoids energy diffusion to the entire sheet, reducing thermal stress accumulation; the highly localized energy input only acts on the active site region within the sheet, rather than the entire sheet, thus preserving the structural integrity of the monolayer graphene oxide to the maximum extent while etching pores. In addition, the presence of the liquid phase system also plays a crucial buffering role; the solvent can quickly absorb excess energy that has not participated in the reaction, preventing excessively high local temperatures from causing carbonization or breakage of the sheet, while also inhibiting aggregation between sheets, providing a guarantee for the stable preservation of the monolayer structure.

[0021] Preferably, the parameters of the pulsed laser are: single pulse width of 5-10 ns, pulse energy of 40-80 mJ, and pulse frequency of 5-20 Hz.

[0022] Furthermore, in step (3), the irradiation treatment time is 5-30 min.

[0023] By adjusting the single-pulse energy, pulse frequency, or laser duration of the laser, the total energy input into the reaction system can be controlled, thereby enabling control over the degree of nanopore formation. As the laser energy input changes, the number, size, and distribution characteristics of the pores become adjustable, making the formation of porous structures repeatable and tunable.

[0024] Furthermore, in step (3), the separation method is centrifugal separation, with a centrifugal speed of 8000-12000 rpm and a centrifugation time of 5-10 min.

[0025] Further, in steps (2) and (3), an oxidizing etching agent is introduced into the graphene oxide solution, and the mixed solution is subjected to laser irradiation treatment under stirring conditions. The laser energy is rapidly absorbed by the graphene oxide and converted into local transient thermal energy, forming an unstable high-temperature environment within an extremely short timescale (nanosecond scale). Under the laser photothermal effect, the local area of ​​the graphene oxide sheet undergoes structural activation, and at the same time, hydrogen peroxide generates active species with etching capabilities under high temperature, selectively etching carbon atoms in the plane of the graphene oxide, thereby forming a nanoscale porous structure in a two-dimensional plane. This process is the synergistic result of laser photothermal effect and chemical etching effect, and the pore structure is mainly formed inside the plane of the monolayer graphene oxide. By adjusting the laser energy input method, the degree of pore structure formation can be controlled in size. After the laser treatment is completed, the reaction system is separated and cleaned to remove residual etching agent and by-products, resulting in a structurally stable porous graphene oxide material.

[0026] Further, in step (4), the porous graphene oxide is dispersed in a solvent and a chemical reducing agent is added for chemical reduction treatment; the chemical reducing agent is selected from one or more of hydrazine hydrate, ascorbic acid, sodium borohydride, hydroiodic acid, sodium sulfite, tea polyphenols, urea and glucose.

[0027] Furthermore, the mass ratio of the porous graphene oxide to the chemical reducing agent is 1:(0.5-10).

[0028] Furthermore, the mass ratio of the porous graphene oxide to hydrazine hydrate is 1:(0.5-1.5).

[0029] Furthermore, in step (4), the temperature of the chemical reduction treatment is 80-100 ℃ and the time is 60-120 min.

[0030] Furthermore, in step (4), the chemical reduction treatment also includes the operation of washing and separating the product.

[0031] Furthermore, in step (4), the porous graphene oxide is chemically reduced to remove the oxygen-containing functional groups on its surface, thus transforming it into porous graphene. The reduction treatment is carried out without destroying the already formed pore structure, thereby obtaining monolayer porous graphene.

[0032] The present invention also protects a single-layer porous graphene prepared by the above method.

[0033] The monolayer porous graphene provided by this invention has the following structural and performance characteristics: the pore size is stable below 50 nm, and the pore structure is uniformly distributed in a two-dimensional plane; it maintains a complete monolayer structure without obvious sheet breakage, interlayer overlap or structural collapse; the number of effective mass transfer channels and chemically active edge sites is significantly increased, exhibiting better comprehensive performance in electrochemical energy storage, membrane separation and related mass transfer applications, and has broad application prospects.

[0034] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0035] 1. This invention employs laser transient photothermal loading as the primary energy input method. The hole-forming process occurs within an extremely short timescale. Compared to hydrothermal or solvothermal etching methods that rely on prolonged bulk heating, the preparation time is significantly reduced from several hours to tens of hours to just minutes, greatly improving preparation efficiency and effectively reducing energy consumption. Benefiting from the short duration and high degree of spatial localization of laser photothermal action, this invention effectively avoids the damage to the graphene structure caused by prolonged bulk heating during the hole-forming process. After subsequent chemical reduction treatment, the obtained porous graphene still perfectly maintains its single-layer structural characteristics, without significant interlayer overlap or macroscopic structural damage.

[0036] 2. This invention successfully achieves the controllable formation of in-plane porous structures in monolayer graphene. The pores are primarily distributed within the two-dimensional plane of the monolayer graphene, rather than between layers or at the edges, thus avoiding the sheet breakage or structural collapse problems common in existing etching methods. By adjusting the laser energy input method, stable in-plane generation of nanopore structures can be achieved, with pore sizes strictly within the nanoscale range. The uniformity of pore distribution is significantly better than that of random chemical etching methods. Furthermore, the pore structure of this invention is highly tunable; the degree of nanopore formation is closely related to the laser energy input, enabling precise control of the porous structure and overcoming the technical shortcomings of traditional wet chemical etching processes where pore size and density are difficult to control.

[0037] 3. The monolayer porous graphene prepared by this invention introduces a large number of nanoscale pore structures within a two-dimensional plane. This not only significantly shortens the in-plane mass transfer path in the material but also significantly increases the number of active sites at the pore edges. Compared with non-porous graphene, the number of effective diffusion channels per unit area is greatly increased, which is beneficial for the rapid transport of ions or molecules. Relying on the complete preservation of the monolayer structure and the synergistic effect of the nanopores, the porous graphene prepared by this invention exhibits superior comprehensive performance in electrochemical energy storage, membrane separation, and related mass transfer applications. In typical application scenarios, its ion diffusion resistance is significantly reduced, and the effective utilization rate per unit mass or unit area is significantly improved, demonstrating broad application potential.

[0038] 4. The process conditions of this invention are mild and can be smoothly implemented under normal temperature and pressure conditions. The process flow is simple and has good repeatability. The equipment requirements are relatively low. There is no need for complex high temperature and high pressure equipment or cumbersome template preparation and removal steps. This not only reduces the preparation cost, but also makes it more suitable for promotion and application in laboratory conditions and further scale-up preparation. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the synergistic mechanism of laser photothermal-chemical etching in this invention.

[0040] Figure 2 This is a transmission electron microscope image of the monolayer porous graphene prepared in Example 1.

[0041] Figure 3 The images are atomic force microscopy images of the monolayer porous graphene prepared in Examples 1-3, from left to right: Example 1, Example 2, and Example 3.

[0042] Figure 4 An atomic force microscope image of the monolayer porous graphene prepared in Comparative Example 1.

[0043] Figure 5 An atomic force microscope image of the monolayer porous graphene prepared in Comparative Example 2.

[0044] Figure 6 An atomic force microscope image of the monolayer porous graphene prepared in Comparative Example 3. Detailed Implementation

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] This invention provides a method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching, comprising the following steps:

[0047] (1) Graphene oxide is dispersed in a solvent to obtain a graphene oxide solution;

[0048] (2) Add hydrogen peroxide or an aqueous solution of hydrogen peroxide to the graphene oxide solution, and the volume fraction of hydrogen peroxide in the resulting mixed solution is 0.1%-0.3%;

[0049] (3) Under stirring conditions, the mixed solution is irradiated with a pulsed laser. After the treatment, the product is separated and cleaned to obtain porous graphene oxide. The parameters of the pulsed laser are: single pulse width of 5-20 ns, pulse energy of 40-120 mJ, and pulse frequency of 5-50 Hz.

[0050] (4) The porous graphene oxide is chemically reduced to obtain the single-layer porous graphene.

[0051] This invention has a key feature that distinguishes it from existing laser etching technologies for graphene. The laser targets suspended graphene oxide sheets in solution, rather than solid-film graphene or graphene structures on a substrate. During laser processing, an oxidizing etching agent is introduced into the graphene oxide solution. Under the photothermal effect of the laser, this agent generates active species with etching capabilities. This enhances the selective etching effect on carbon atoms within the two-dimensional plane of graphene and helps lower the pore-forming energy barrier, thereby improving pore-forming efficiency.

[0052] This invention achieves selective removal of carbon atoms within the two-dimensional plane of graphene in an extremely short timescale through the synergistic effect of laser transient photothermal loading and chemical etching, thereby forming a nanoscale porous structure. This nanoporous structure is primarily constructed during the laser processing stage. The chemical reduction step, placed after laser-induced pore formation, transforms porous graphene oxide into porous graphene. Its core function is to remove oxygen-containing functional groups, restore the conductivity and structural integrity of graphene, and complete the material transformation without damaging the already formed nanoporous structure. This process sequence design constitutes a key technical feature of this invention. The resulting nanopores are distributed within the two-dimensional plane of the monolayer graphene, not generated by interlayer peeling, sheet fragmentation, or edge erosion, thus achieving stable preparation of monolayer porous graphene.

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0054] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0055] Example 1

[0056] A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching includes the following steps:

[0057] (1) Graphene oxide was dispersed in deionized water and ultrasonically dispersed for 30 min to obtain a uniform and stable aqueous solution of graphene oxide with a concentration of 0.5 mg / mL, wherein the graphene oxide sheets were fully exfoliated and mainly existed in a monolayer state.

[0058] (2) Add a 30% hydrogen peroxide aqueous solution to the graphene oxide aqueous solution and mix the solution thoroughly by magnetic stirring. The volume fraction of hydrogen peroxide in the resulting mixed solution is 0.3%.

[0059] (3) The mixed solution obtained in step (2) was placed in a transparent reaction vessel and irradiated with a nanosecond pulsed laser for 20 min under continuous stirring. The laser wavelength was located in the band that could be effectively absorbed by graphene oxide (532 nm). After treatment, the product was centrifuged at 10,000 rpm for 10 min. After discarding the supernatant, the precipitate was washed multiple times with deionized water to remove residual etching reagents and reaction byproducts, thus obtaining structurally stable porous graphene oxide. The schematic diagram of its mechanism is shown below. Figure 1 As shown; the parameters of the nanosecond pulsed laser are: single pulse width of 7 ns, pulse energy of 40 mJ, and pulse frequency of 10 Hz;

[0060] (4) The porous graphene oxide was redispersed in deionized water, and hydrazine hydrate was added for chemical reduction treatment at 90 °C for 60 min. The mass ratio of porous graphene oxide to hydrazine hydrate was 1:0.88. After the reduction was completed, the product was washed and separated to obtain single-layer porous graphene.

[0061] The monolayer porous graphene prepared in Example 1 was characterized with high resolution using transmission electron microscopy. Figure 2 The image shows a transmission electron microscope (TEM) image of the monolayer porous graphene prepared in Example 1. Figure 2 It can be clearly observed that a uniformly distributed nanopore structure has been formed in the two-dimensional plane of the single-layer porous graphene. The pores exhibit typical two-dimensional in-plane pore formation characteristics, without any trace of sheet breakage or edge erosion.

[0062] Example 2

[0063] A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching is basically the same as that in Example 1, except that the pulse energy in step (3) is 80 mJ.

[0064] Example 3

[0065] A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching is basically the same as that in Example 1, except that the pulse energy in step (3) is 120 mJ.

[0066] Large-format scanning and height analysis were performed on the monolayer porous graphene prepared in Examples 1-3 using atomic force microscopy. Figure 3 Atomic force microscopy images of the monolayer porous graphene prepared in Examples 1-3, from left to right: Example 1, Example 2, and Example 3. Figure 3 As can be seen, with the increase of pulse energy, the nanopore structure in the two-dimensional plane of the monolayer porous graphene exhibits obvious changes: when the pulse energy is 40 mJ, only a few scattered pores appear in the plane; when the energy is increased to 80 mJ, the number of pores increases significantly and the distribution becomes more uniform; when the energy reaches 120 mJ, the pore size further increases and the pore density continues to increase, while the pore structure still maintains a continuous distribution in the two-dimensional plane. Under different pulse energy conditions, no sheet breakage or local collapse of the pore structure was observed, verifying that the monolayer porous graphene prepared by the method of this invention can not only achieve a uniform and continuous distribution of nanopores in the two-dimensional plane, but also precisely adjust the pore structure parameters (size and density) by controlling the pulse energy, intuitively demonstrating the technical advantage of the strong controllability of the pore structure of this invention.

[0067] Comparative Example 1

[0068] A method for preparing monolayer porous graphene based on laser photothermal action includes the following steps:

[0069] (1) Graphene oxide was dispersed in deionized water and ultrasonically dispersed for 60 min to obtain a uniform and stable aqueous solution of graphene oxide with a concentration of 0.5 mg / mL, wherein the graphene oxide sheets were fully exfoliated and mainly existed in a monolayer state.

[0070] (2) The aqueous solution of graphene oxide was placed in a transparent reaction vessel and the mixed solution was irradiated with a nanosecond pulsed laser under continuous stirring. The laser wavelength was located in the band that could be effectively absorbed by graphene oxide. After the treatment, the product was centrifuged at 10,000 rpm for 10 min. After discarding the supernatant, the precipitate was washed multiple times with deionized water to remove residual etching reagents and reaction byproducts, and porous graphene oxide was obtained. The parameters of the nanosecond pulsed laser were: single pulse width of 7 ns, pulse energy of 40 mJ, and pulse frequency of 10 Hz.

[0071] (3) The porous graphene oxide was redispersed in deionized water, and hydrazine hydrate was added for chemical reduction treatment at 90 °C for 60 min. After the reduction was completed, the product was washed and separated to obtain single-layer porous graphene.

[0072] Figure 4 This is an atomic force microscope image of the monolayer porous graphene prepared in Comparative Example 1. From... Figure 4 As can be seen, without the introduction of hydrogen peroxide, laser photothermal treatment alone resulted in localized structural disturbances and defects on the graphene surface, manifesting as sporadic irregular damage. A stable, uniform nanoporous structure was not formed; only dispersed, irregular surface undulations existed. This demonstrates that laser photothermal treatment alone is insufficient to effectively construct nanopores within the two-dimensional plane of a single-layer graphene layer. The synergy between chemical etching and laser photothermal treatment in this invention is crucial for the stable formation of a uniform nanoporous structure, highlighting the irreplaceable role of chemical etchants in the pore-forming process.

[0073] Comparative Example 2

[0074] A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching is basically the same as that in Example 1, except that in step (2), the volume fraction of hydrogen peroxide in the mixed solution is 0.6%.

[0075] Figure 5 The image shows an atomic force microscope image of the monolayer porous graphene prepared in Comparative Example 2. Figure 5 As can be seen, under conditions of excessive etchant, the etching reaction within the two-dimensional plane of graphene is significantly intensified, resulting in obvious over-etching. The size of the pores within the plane increases substantially, with some pores exceeding the expected nanoscale control range. Simultaneously, the pore size distribution becomes significantly wider. The uniformity and continuity of the pore structure are disrupted, with localized areas showing interconnected pores and damage to the sheet structure. The structural integrity of the monolayer graphene is affected to some extent. This indicates that excessively high etchant concentrations disrupt the synergistic balance between laser photothermal effects and chemical etching, not only failing to achieve precise control of the pore structure but also leading to uncontrolled pore size and uneven distribution, ultimately hindering the acquisition of size-controlled, structurally uniform monolayer porous graphene.

[0076] Comparative Example 3

[0077] A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching is basically the same as that in Example 1, except that the pulse frequency in step (3) is 80 Hz.

[0078] Figure 6 The image shows an atomic force microscope image of the monolayer porous graphene prepared in Comparative Example 3. Figure 6As can be seen, although the left region exhibits a large number of dispersed nanopores, the pore density is significantly uneven; the right region shows significant agglomeration and structural collapse, forming irregular blocky protrusions and depressions. This indicates that at a pulse frequency of 80 Hz, the time density of laser energy input is too high, which breaks the synergistic balance between laser photothermal and chemical etching, causing excessive etching in local areas. This not only destroys the continuity of the graphene sheets, but also significantly affects the integrity of the single-layer structure, ultimately making it impossible to obtain a single-layer porous graphene with a uniform structure.

[0079] In summary, the method provided by this invention can stably construct nanoscale porous structures within a two-dimensional plane of graphene while maintaining the integrity of the graphene monolayer structure. Compared with the original graphene without introduced porous structures, the monolayer porous graphene prepared by this method exhibits a significantly increased number of in-plane mass transfer channels and a uniform and regular pore structure distribution. Furthermore, the pore-forming process can be precisely controlled by adjusting the input parameters of the laser pulse energy, verifying the technical feasibility and process stability of the preparation method of this invention.

[0080] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing monolayer porous graphene based on the synergistic effect of laser photothermal-chemical etching, characterized in that, Includes the following steps: (1) Graphene oxide is dispersed in a solvent to obtain a graphene oxide solution; (2) Hydrogen peroxide is added to the graphene oxide solution, and the volume fraction of hydrogen peroxide in the resulting mixed solution is 0.1%-0.3%; (3) Under stirring conditions, the mixed solution is irradiated with a pulsed laser for 5-30 min. After the treatment, the product is separated and cleaned to obtain porous graphene oxide. The parameters of the pulsed laser are: single pulse width of 5-20 ns, pulse energy of 40-120 mJ, and pulse frequency of 5-50 Hz. (4) The porous graphene oxide is dispersed in a solvent and a chemical reducing agent is added for chemical reduction treatment to obtain the single-layer porous graphene; the chemical reducing agent is selected from one or more of hydrazine hydrate, ascorbic acid, sodium borohydride, hydroiodic acid and sodium sulfite; the temperature of the chemical reduction treatment is 80-100 ℃ and the time is 60-120 min.

2. The method according to claim 1, characterized in that, In step (1), the concentration of the graphene oxide solution is 0.1-0.5 mg / mL.

3. The method according to claim 1, characterized in that, In step (1), a graphene oxide solution is obtained by ultrasonic dispersion treatment. The ultrasonic frequency is 35-40 kHz and the ultrasonic time is 30-60 min.

4. The method according to claim 1, characterized in that, In step (3), the separation method is centrifugal separation, with a centrifugal speed of 8000-12000 rpm and a centrifugation time of 5-10 min.

5. The method according to claim 1, characterized in that, The mass ratio of the porous graphene oxide to the chemical reducing agent is 1:(0.5-10).

6. The method according to claim 1, characterized in that, The mass ratio of the porous graphene oxide to hydrazine hydrate is 1:(0.5-1.5).

7. A single-layer porous graphene prepared by the method according to any one of claims 1-6.

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