Method for the electrofiltration of hydrogen peroxide by means of a carbon nanotube woven membrane

Abstract

The application discloses a method for synthesizing hydrogen peroxide by electric filtration of carbon nanotube woven membrane. The method comprises the following steps: S1. dispersing carbon nanotubes without chemical catalytic modification in a solvent, and ultrasonic treatment to obtain a dispersion liquid; S2. placing the dispersion liquid on a microporous filter membrane, under the driving of pressure, the carbon nanotubes are spontaneously interwoven, physically overlapped and layer-by-layer interlocked on the surface of the microporous filter membrane under the guidance of hydrodynamic orientation, in-situ assembling a three-dimensional network structure of the carbon nanotubes to obtain a carbon nanotube woven membrane; S3. after washing and drying the carbon nanotube woven membrane, the carbon nanotube woven membrane is assembled as a cathode in a cathode chamber of an electrolytic cell, and the edge of the carbon nanotube woven membrane is sealed; and S4. connecting a circuit between the parallel placed cathode and anode, pumping an electrolyte containing dissolved oxygen into the electrolytic cell, and generating hydrogen peroxide through a two-electron oxygen reduction reaction after the electrolyte flows through the anode and vertically penetrates the nanoscale interwoven pore channels in the interior of the cathode.

Description

Technical Field

[0001] This invention relates to the field of electrochemistry, and in particular to a method for synthesizing hydrogen peroxide by electrofiltration using a carbon nanotube woven membrane. Background Technology

[0002] Hydrogen peroxide (H2O2), as an environmentally friendly strong oxidant, is widely used in key areas such as industrial bleaching, fine chemicals, medical disinfection, and environmental water treatment (e.g., advanced oxidation processes) because it only produces water after reaction without secondary pollution. In recent years, with the increasing global emphasis on green chemistry and sustainable development, distributed water treatment and resource recycling scenarios have created a more urgent need for a timely and safe supply of H2O2. However, currently, the vast majority of global H2O2 production still relies on the energy-intensive, highly polluting, and cumbersome "anthraquinone process." This model not only poses significant safety risks due to the long-distance transportation and storage of high concentrations but also fails to meet the modern environmental protection sector's demand for in-situ, on-demand access to green oxidants.

[0003] To overcome the limitations of centralized production, the electrochemical two-electron oxygen reduction (2e-ORR) synthesis of hydrogen peroxide has emerged due to its significant advantages of being green and distributed. However, the efficiency of this reaction is severely limited by the oxygen mass transfer process. Since oxygen has extremely low solubility in water (even at oxygen saturation, it is only about 38 mg / L), achieving efficient mass transfer and H2O2 conversion under low dissolved oxygen conditions is a core challenge that urgently needs to be solved in the process of bringing this technology to practical application.

[0004] To enhance mass transfer, an electrofiltration (through-feedback) reaction configuration has been introduced, forcing convection to allow the electrolyte to permeate through a porous electrode, aiming to overcome the mass transfer limitations at the interface. However, currently used through-feedback electrode substrates (such as carbon cloth, commercial carbon paper, carbon felt, or conventional macroporous carbon-based materials) are primarily composed of coarse pores in the micrometer or even larger sizes. In such predominantly large-pore systems, the liquid-phase diffusion boundary layer on the electrode surface remains relatively thick due to hydrodynamic limitations. For low concentrations of dissolved oxygen, penetrating this thick boundary layer to reach the catalytically active sites still presents significant mass transfer resistance. This means that even in through-feedback mode, the reaction kinetics of the system are still constrained by the sluggish diffusion under low-oxygen conditions, making it difficult to fully utilize the performance limits of the electrocatalyst.

[0005] Therefore, there is an urgent need in this field to develop a solution for the efficient production of hydrogen peroxide even in low-oxygen environments.

[0006] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a method for synthesizing hydrogen peroxide by electrofiltration using carbon nanotube woven membranes, in order to solve the problem of how to overcome the mass transfer bottleneck under low dissolved oxygen conditions and achieve efficient, stable and continuous electrochemical synthesis of hydrogen peroxide.

[0008] The present invention adopts the following technical solution:

[0009] A method for synthesizing hydrogen peroxide via carbon nanotube woven membrane electrofiltration includes the following steps:

[0010] S1. Unmodified carbon nanotubes are dispersed in a solvent and ultrasonically treated to obtain a dispersion;

[0011] S2. The dispersion is placed on a microporous filter membrane. Under pressure, the solvent in the dispersion passes through the microporous filter membrane, and the carbon nanotubes in the dispersion spontaneously interweave, physically overlap, and interlock layer by layer on the surface of the microporous filter membrane under the directional guidance of hydrodynamics, and are assembled in situ to form a three-dimensional network structure of carbon nanotubes, thereby obtaining a binder-free carbon nanotube woven membrane. The three-dimensional network structure of carbon nanotubes has nanoscale interwoven channels with nanoscale pore size.

[0012] S3. After cleaning and drying the carbon nanotube woven membrane, it is assembled as a cathode in the cathode chamber of the electrolytic cell, and the edges of the carbon nanotube woven membrane are sealed so that the effective reaction area of ​​the carbon nanotube woven membrane completely covers the electrolyte flow section of the cathode chamber.

[0013] S4. Connect a circuit between the parallel-placed cathode and the anode of the electrolytic cell anode chamber, pump an electrolyte containing dissolved oxygen into the electrolytic cell anode chamber, and after the electrolyte flows through the anode, it is forced to vertically penetrate the nanoscale interwoven channels inside the cathode, where a two-electron oxygen reduction reaction occurs to generate hydrogen peroxide, which then flows out from the electrolytic cell cathode chamber.

[0014] This invention solves the core problem of low hydrogen peroxide synthesis efficiency in existing electrochemical hydrogen peroxide synthesis systems under low dissolved oxygen conditions due to limited mass transfer, and includes the following beneficial effects:

[0015] 1. Overcoming the Mass Transfer Bottleneck in Low-Oxygen Environments: Existing planar (flow-through) electrodes often have a diffusion boundary layer of over 100 micrometers during electrochemical reactions. The pore sizes of existing through-hole electrode substrates (such as commercial carbon felt, carbon paper, carbon cloth, and other macroporous carbon materials) are typically in the hundreds of micrometers or even higher. Even in the through-hole mode, the liquid-phase diffusion boundary layer on the electrode surface remains relatively thick. For oxygen molecules, which have extremely low natural solubility, the mass transfer resistance to penetrate this thick boundary layer and reach the catalytic active site is enormous. To address this limitation in mass transfer (thick diffusion boundary layer), the carbon nanotube woven membrane provided in this invention features a three-dimensional network structure of carbon nanotubes on the microporous filter membrane surface with nanoscale pores. In electrofiltration mode, the electrolyte is forced to penetrate these nanopores, greatly compressing the diffusion boundary layer at the solid-liquid interface. This allows low-concentration dissolved oxygen to instantly overcome the mass transfer resistance and reach the catalytic interface, breaking through the bottleneck of insufficient mass transfer in traditional macroporous electrodes at the physical structure level.

[0016] 2. Eliminating the channeling effect and improving Faraday efficiency: Traditional porous materials have wide and disordered pore sizes. Under the forced convection of electrofiltration, the electrolyte easily undergoes "sideflow" or "short-circuit" penetration (i.e., channeling effect) along the macropores with the least resistance. This not only leads to a large number of "catalytic dead zones" within the membrane that cannot contact the water flow, greatly wasting active sites, but also causes excessively high local flow rates, resulting in a mismatch between the residence time of products and reactants, and thus triggering serious side reactions (deep reduction or disproportionation decomposition of hydrogen peroxide). To address the above-mentioned problem of uneven fluid distribution (channeling and short-circuit effect), the uniform micro-woven network of this invention completely solves the problems of uneven fluid distribution and "short-circuit" penetration in the flow permeation mode of traditional macroporous carbon substrates (such as carbon cloth and carbon felt). The electrolyte achieves uniform distribution and precise confined mass transfer within the carbon nanotube woven membrane, which not only multiplies the utilization rate of intrinsic catalytic active sites, but also rapidly and synchronously removes the generated hydrogen peroxide from the electrode surface, effectively inhibiting the deep reduction and decomposition of products.

[0017] 3. Excellent Long-Term Structural Stability Without Binders: Existing through-type electrodes typically require insulating polymer binders to coat the catalyst onto a supporting substrate. This not only masks intrinsic catalytic active sites and significantly increases interfacial contact resistance, but also results in a fragile mechanical structure due to the lack of self-supporting coating. Under the long-term high flux, high pressure differential, and intense water shearing forces of the electrofiltration system, the catalyst layer is prone to irreversible peeling, deformation, or collapse. Furthermore, the reliance on complex chemical catalytic modifications for some electrodes further increases their instability during long-term operation, leading to short lifespans and making them unsuitable for long-term, stable continuous hydrogen peroxide synthesis. To address the aforementioned problems of poor structural stability and easy deactivation and detachment of traditional coated electrodes, the carbon nanotube woven membrane of this invention serves as the electrode, eliminating the need for insulating polymer binders or complex chemical catalytic modifications. The one-dimensional carbon nanotubes spontaneously interweave and physically overlap under pressure, endowing the woven membrane with excellent macroscopic tensile and shear strength. It can readily withstand the long-term high pressure differential and fluid erosion in the electrofiltration system, avoiding the fatal defects of easy detachment and short lifespan of traditional coated electrodes.

[0018] 4. Pure Physical Assembly and Easy Scale-up: The preparation of traditional high-performance porous catalytic electrodes often relies on harsh high-temperature treatments (such as high-temperature carbonization and calcination) or complex chemical reaction conditions, which are not only energy-intensive and time-consuming, but also result in large batch-to-batch variations. More challenging is the difficulty of easily and precisely controlling key engineering parameters such as membrane material thickness and internal micropore size distribution using existing conventional preparation methods, leading to poor electrode structure consistency. This cumbersome and difficult-to-control process significantly increases manufacturing costs, severely restricting its large-scale industrial application in distributed hydrogen peroxide production devices. Addressing the problems of cumbersome existing electrode preparation processes and difficulties in achieving precise parameter control and large-scale production, this invention utilizes a simple pressure-driven (such as vacuum filtration) fluid dynamics directional guidance process, enabling batch assembly of membrane materials without harsh high-temperature or chemical reaction conditions. By simply adjusting the concentration and volume of the dispersion, precise control of key parameters such as membrane thickness and nanopore size distribution can be achieved, highly meeting the large-scale industrial needs of distributed hydrogen peroxide production devices.

[0019] In summary, this invention induces the self-assembly of carbon nanotubes under pressure to form a woven membrane with uniform nanoscale pores, and applies it to an electrofiltration configuration. When the electrolyte is forced to penetrate these nanopores, the nanopores effectively compress the diffusion boundary layer at the solid-liquid interface. This significant thinning of the diffusion boundary layer can shorten the diffusion distance of low-concentration dissolved oxygen to the active sites by orders of magnitude, thereby fundamentally overcoming the mass transfer bottleneck under hypoxic conditions and greatly promoting the mass transfer of low-concentration dissolved oxygen. This achieves highly efficient electrochemical synthesis of hydrogen peroxide without actual catalytic modification. This invention provides a novel solution for achieving decentralized, low-energy-consumption, and highly efficient electrofiltration synthesis of hydrogen peroxide. Attached Figure Description

[0020] Figure 1 This is a physical image of the carbon nanotube woven membrane of Embodiment 1 of the present invention.

[0021] Figure 2 This is a top-view scanning electron microscope image of the carbon nanotube woven membrane of Example 1 of the present invention.

[0022] Figure 3 This is a pore size distribution diagram of the carbon nanotube woven membrane of Example 1 of the present invention.

[0023] Figure 4 This is a cross-sectional scanning electron microscope image of the carbon nanotube woven membrane of Example 1 of the present invention.

[0024] Figure 5 This is a schematic diagram of the reaction system for synthesizing hydrogen peroxide by electrofiltration of carbon nanotube woven membrane in Embodiment 2 of the present invention.

[0025] Figure 6 This is a comparison chart of the performance of carbon nanotube woven membranes in producing hydrogen peroxide in flow-through and through-flow modes in Example 2.

[0026] Figure 7 This is a computational fluid dynamics simulation verification diagram of the performance of carbon nanotube woven membrane in producing hydrogen peroxide in flow-through and through-flow modes in Example 2.

[0027] Figure 8 This is a comparison chart of the performance of carbon nanotube woven membranes in producing hydrogen peroxide under different dissolved oxygen concentrations in Example 2. Detailed Implementation

[0028] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope of the present invention or its application. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0029] This invention provides a method for synthesizing hydrogen peroxide via carbon nanotube woven membrane electrofiltration, comprising the following steps:

[0030] S1. Unmodified carbon nanotubes are dispersed in a solvent and ultrasonically treated to obtain a dispersion;

[0031] S2. The dispersion is placed on a microporous filter membrane. Under pressure, the solvent in the dispersion passes through the microporous filter membrane, and the carbon nanotubes in the dispersion spontaneously interweave, physically overlap, and interlock layer by layer on the surface of the microporous filter membrane under the directional guidance of hydrodynamics, and are assembled in situ to form a three-dimensional network structure of carbon nanotubes, thereby obtaining a binder-free carbon nanotube woven membrane. The three-dimensional network structure of carbon nanotubes has nanoscale interwoven channels with nanoscale pore size.

[0032] S3. After cleaning and drying the carbon nanotube woven membrane, it is assembled as a cathode in the cathode chamber of the electrolytic cell, and the edges of the carbon nanotube woven membrane are sealed so that the effective reaction area of ​​the carbon nanotube woven membrane completely covers the electrolyte flow section of the cathode chamber.

[0033] S4. Connect a circuit between the parallel-placed cathode and the anode of the electrolytic cell anode chamber, pump an electrolyte containing dissolved oxygen into the electrolytic cell anode chamber, and after the electrolyte flows through the anode, it is forced to vertically penetrate the nanoscale interwoven channels inside the cathode, where a two-electron oxygen reduction reaction occurs to generate hydrogen peroxide, which then flows out from the electrolytic cell cathode chamber.

[0034] In step S1, the van der Waals forces between carbon nanotubes are broken by the cavitation effect of ultrasound, resulting in a uniform and stable dispersion of carbon nanotubes in the form of single tubes or small tube bundles.

[0035] In step S2, under pressure, the solvent penetrates the microporous filter membrane vertically downwards; simultaneously, the one-dimensional carbon nanotubes are guided by hydrodynamics and uniformly trapped on the filter membrane surface. As the liquid level decreases, the carbon nanotubes spontaneously interweave, physically overlap, and interlock layer by layer at the microscale, assembling in situ to form a "woven" structure with a highly uniform nanoscale pore network (in the three-dimensional carbon nanotube network structure, more than 90% of the pores have a pore size between 10 and 100 nm).

[0036] In step S3, by mechanically pressing and sealing the edges of the carbon nanotube woven membrane (for example, by using insulating and corrosion-resistant silicone gaskets or polytetrafluoroethylene gaskets to mechanically press and seal the edges of the carbon nanotube woven membrane), the edge bypass or short-circuit effect can be eliminated, thereby ensuring that the effective reaction area of ​​the carbon nanotube woven membrane completely covers the electrolyte flow section of the cathode chamber.

[0037] In step S4, the electrolyte must be forced to penetrate the nanoscale interwoven channels of the carbon nanotube woven membrane in a direction perpendicular to the membrane surface. A two-electron oxygen reduction reaction occurs in the three-dimensional network structure of the carbon nanotubes to generate hydrogen peroxide, which then flows out from the outlet, thereby constructing an integrated electrofiltration (penetration) flow path of "flow-reaction-separation".

[0038] In the above method, the nanopores of the three-dimensional network structure of carbon nanotubes in the carbon nanotube woven film significantly compress the solid-liquid diffusion boundary layer, which can essentially enhance the mass transfer efficiency of low-concentration dissolved oxygen and achieve efficient synthesis of hydrogen peroxide even under low-oxygen conditions.

[0039] In some embodiments, the pressure drive is provided by vacuum filtration, during which the solvent in the dispersion penetrates the microporous filter membrane under negative pressure, and the carbon nanotubes are trapped and assembled into the three-dimensional network structure of the carbon nanotubes on the surface of the microporous filter membrane by hydrodynamics.

[0040] In some embodiments, the carbon nanotubes are multi-walled carbon nanotubes.

[0041] In some embodiments, the carbon nanotubes in step S1 have an inner diameter of 3-10 nm, an outer diameter of 8-100 nm, and a length of 1-30 μm. Preferably, the carbon nanotubes have an inner diameter of 3-5 nm, an outer diameter of 8-15 nm, and a length of 8-14 μm.

[0042] In some embodiments, the pore size of the three-dimensional network structure of carbon nanotubes in the carbon nanotube woven membrane is concentrated in the range of 20-50 nm (i.e., more than 50% of the pores have a pore size in the range of 20-50 nm).

[0043] In some embodiments, the concentration of dissolved oxygen in the electrolyte is between the concentration of naturally dissolved oxygen without aeration and the concentration of dissolved oxygen with aeration up to oxygen saturation.

[0044] In some embodiments, the electrode spacing between the anode and the cathode is 1-10 mm. By controlling the electrode spacing between the anode and the cathode to be 1-10 mm, the ohmic internal resistance of the system can be minimized.

[0045] In some embodiments, the microporous filter membrane is an organic microporous filter membrane or an aqueous mixed cellulose filter membrane.

[0046] In some embodiments, the anode is a metal oxide mesh electrode, a platinum mesh electrode, or a stainless steel mesh electrode.

[0047] In some embodiments, the solvent in step S1 is water (such as ultrapure water); in step S1, an appropriate amount of dispersant (such as a small amount of anhydrous ethanol or a nonionic surfactant) may also be added to help disperse the carbon nanotubes.

[0048] In some embodiments, the ultrasonic power in step S1 is 100 ~ 500 W, and the ultrasonic treatment is performed at -10 to 0°C (e.g., in an ice water bath).

[0049] In some embodiments, the unmodified carbon nanotubes used in step S1 are acid-treated to remove residual metals before being dispersed in a solvent. For example, the carbon nanotubes are dispersed in 5 M hydrochloric acid, heated under reflux at 60 °C for 24 hours, and then purified by repeated washing with ultrapure water, centrifugation, and freeze-drying.

[0050] In some embodiments, the cleaning and drying in step S3 specifically involves washing the formed carbon nanotube woven membrane multiple times with deionized water and anhydrous ethanol to remove residual solvent and excess dispersant (if any) between the networks, preventing them from clogging the nanopores. Subsequently, the membrane is freeze-dried under vacuum for more than 12 hours to obtain a carbon nanotube woven membrane with excellent mechanical strength that has not undergone specific catalytic modification, requires no additional binder, and has no special mechanical modification requirements.

[0051] This invention also provides a reactor for synthesizing hydrogen peroxide via carbon nanotube woven membrane electrofiltration, used to implement the method, comprising:

[0052] The main body of the electrolytic cell is divided into a cathode chamber and an anode chamber. The anode chamber is provided with an inlet, and the cathode chamber is provided with an outlet. The inlet is used to connect a liquid pump to pump the electrolyte in, so that it flows through the anode and is forced to vertically penetrate the cathode before flowing out from the outlet.

[0053] A carbon nanotube woven membrane, which serves as the cathode, is disposed within the cathode chamber, and the edges of the cathode are sealed by a sealing element, so that the effective reaction area of ​​the carbon nanotube woven membrane completely covers the electrolyte flow section of the cathode chamber.

[0054] The anode, parallel to the cathode and disposed within the anode chamber; and

[0055] A power interface for applying voltage to the cathode and the anode.

[0056] This invention also provides a system for synthesizing hydrogen peroxide via carbon nanotube woven membrane electrofiltration, comprising:

[0057] The aforementioned reactor for electrofiltration synthesis of hydrogen peroxide using a carbon nanotube woven membrane;

[0058] An infusion pump, connected to the inlet, is used to deliver electrolyte at a controllable flow rate;

[0059] A DC power supply, connected to the power interface, for providing the voltage required for electrolysis; and

[0060] A collection device for collecting liquid containing synthesized hydrogen peroxide flowing out of the cathode chamber.

[0061] In some implementations, the infusion pump is a constant flow pump, such as a peristaltic pump or a horizontal flow pump; the inlet of the anode chamber is connected to the infusion pump through a corrosion-resistant pipeline to precisely control the apparent flow rate of the electrolyte penetrating the carbon nanotube woven membrane, so that the electrolyte flows steadily into the anode and cathode in sequence and then flows out.

[0062] The following describes specific embodiments of the present invention.

[0063] Example 1

[0064] This embodiment 1 provides a carbon nanotube woven film and its preparation method, including the following steps:

[0065] S1. Commercially available multi-walled carbon nanotubes are used as the initial raw material. Specifically, the purchased multi-walled carbon nanotubes have a purity greater than 99%, an inner diameter between 3-5 nm, an outer diameter between 8-15 nm, a length between 8-14 μm, and a specific surface area ≥ 250 m². 2 ·g -1 .

[0066] S2. The initial multi-walled carbon nanotube raw material is treated with acid to remove residual metals. Specifically, the multi-walled carbon nanotubes are dispersed in 5 M hydrochloric acid and heated under reflux at 60 °C for 24 hours. Then, the multi-walled carbon nanotubes are purified by repeated washing with ultrapure water, centrifugation, and freeze drying.

[0067] S3. Add 30 mg of purified multi-walled carbon nanotubes from S2 to ultrapure water to prepare a multi-walled carbon nanotube suspension with a concentration of 1 mg / mL. Then, under ice-water bath conditions, use a cell disruptor at 300 W power for sonication for 10 minutes to completely break the van der Waals aggregation between carbon nanotubes through cavitation, and obtain a highly uniform and stable dispersion (a suspension in which carbon nanotubes are evenly dispersed).

[0068] S4. The dispersion obtained in S3 is transferred to a vacuum filtration device equipped with a microporous filter membrane (a polytetrafluoroethylene filter membrane with a pore size of 5 μm). Driven by negative pressure and guided by hydrodynamics, the solvent rapidly penetrates the microporous filter membrane vertically downwards. Simultaneously, one-dimensional carbon nanotubes spontaneously interweave, physically overlap, and interlock layer by layer on the surface of the microporous filter membrane, assembling in situ to form a three-dimensional network structure of carbon nanotubes with highly uniform nanoscale pores, thereby obtaining a carbon nanotube woven membrane, which includes the microporous filter membrane and the three-dimensional network structure of carbon nanotubes formed on the microporous filter membrane.

[0069] S5. After filtration, the formed carbon nanotube woven membrane is washed repeatedly with ultrapure water and anhydrous ethanol to thoroughly remove residual solvent and dispersant between the networks. Then, the entire carbon nanotube woven membrane is transferred to a vacuum freeze-drying oven and dried for 12 hours. After drying, a binder-free carbon nanotube woven membrane is obtained, such as... Figure 1 As shown. A top-view scanning electron microscope image of the carbon nanotube woven membrane is shown below. Figure 2 As shown, the pore size of the carbon nanotube woven membrane is concentrated between 20 and 50 nm (e.g. Figure 3 As shown), the film thickness is approximately 200 μm (e.g. Figure 4 (As shown).

[0070] Example 2

[0071] In this embodiment 2, carbon nanotube woven membranes are used for electrofiltration to synthesize hydrogen peroxide, including the following steps:

[0072] S1. A schematic diagram of the main structure of the electrofiltration reaction system is shown below. Figure 5 As shown. The carbon nanotube woven membrane 1 obtained in Example 1 was used as the working electrode (cathode) and horizontally assembled in the cathode chamber of a through-cell electrolytic cell. The anode 2 was a stainless steel mesh electrode, and silicone insulating gaskets were used to mechanically press and strictly seal the edges of the carbon nanotube woven membrane to completely eliminate fluid sideflow. The distance between the anode and cathode was controlled at 10 mm.

[0073] S2. An aqueous solution of sodium sulfate containing dissolved oxygen was used as the electrolyte. The oxygen concentration in the electrolyte was 38 mg / L, and the sodium sulfate concentration was 0.1 mol / L. The electrolyte was pumped in at an apparent flow rate of 2 mL / min using a constant flow pump (not shown). After flowing through the anode, the electrolyte was forced to penetrate vertically and completely through the nanopores of the carbon nanotube woven membrane 1 (e.g., ...). Figure 5 Simultaneously, a two-electron oxygen reduction reaction is carried out by applying a constant external voltage of 2.5 V.

[0074] S3. Collect a quantitative amount of electrofiltration filtrate from the outlet of the cathode chamber and titrate it with a standard potassium permanganate solution (4 mM) to test the hydrogen peroxide production generated by electrofiltration. Calculate the amount of H2O2 produced (n) based on the volume of standard potassium permanganate solution consumed. H2O2 As shown in equation (1):

[0075]

[0076] In equation (1), C KMnO4 V represents the concentration of KMnO4 consumed during the titration process. KMnO4 This indicates the volume of KMnO4 consumed during the titration process.

[0077] like Figure 6 As shown, the yield of hydrogen peroxide produced by this carbon nanotube woven membrane in flow-through mode (1614.8 mg L / L) -1 h -1 The yield of hydrogen peroxide produced was significantly higher than that produced in the flow-by mode (where an electrofilter is filled with electrolyte, the ends are sealed, and the test is conducted at the same voltage for a period of time, followed by a measurement of the amount of H2O2 produced). This yield was 10.9 mg / L. -1 h -1 The yield increased by 147 times, indicating that the pores of the one-dimensional carbon nanotube woven membrane significantly reduced the oxygen diffusion distance in the liquid-forced inflow permeation mode, thereby enhancing the local flow field and significantly improving the oxygen transport and consumption rates. This can also be achieved through methods such as... Figure 7 The computational fluid dynamics simulation results shown are validated (wherein, the CFD simulation was designed and executed using Fluent software, such as...). Figure 7 As shown, a cubic fluid domain with a side length of 300 nm, a width of 300 nm, and a height of 500 nm was constructed to simulate the through-flow mode; a multi-channel model with a pore size of 42 nm was used to simulate the through-flow mode. Convection velocities were calculated using laminar flow physics methods based on the Navier-Stokes equations. Local mass transport of O2 was simulated using diffusion equations, considering the case where the concentration satisfies the rare species transport interface under different porosity conditions. The surface reaction reflected by the model conforms to Fick's diffusion law. The inlet boundary was set to a flow rate of 48.5 μm / s, the initial O2 concentration was set to 38 mg / L, and the surface reaction rate was set to 10. -4 kg m -2 s -1 Simulation results show that in the flow-by mode, O2 consumption is less than 10%, while in the flow-through mode, O2 consumption is almost complete. Figure 8 As shown, under conditions of aeration to oxygen saturation (oxygen content approximately 38 mg / L), the carbon nanotube woven membrane produced hydrogen peroxide in permeation mode with a yield of 1614.8 mg / L. -1 h -1 Even under conditions without aeration (in which the electrolyte contains only naturally dissolved oxygen at a concentration of approximately 8 mg / L), the carbon nanotube woven membrane achieved a hydrogen peroxide yield of 424.3 mg / L in permeation mode. -1 h -1 The yield is also much higher than that of hydrogen peroxide produced in the flow mode (10.9 mg / L). -1 h -1This further demonstrates that the carbon nanotube woven membrane-based electrofiltration system possesses excellent mass transfer enhancement capabilities in low dissolved oxygen environments, significantly promoting dissolved oxygen transport and greatly increasing the yield of electrochemically synthesized hydrogen peroxide.

[0078] As a first variation of the above embodiments, the dispersion can also be filtered by internal and external pressure difference through a specific mold or tubular ceramic substrate to prepare a tubular carbon nanotube woven membrane. During electrofiltration, the oxygen-containing electrolyte is radially forced to penetrate from the outside to the inside of the tube (or from the inside to the outside). This variation can greatly increase the membrane packing area (packing density) per unit volume of reactor.

[0079] As a second variation of the above embodiments, multiple carbon nanotube woven membranes with different pore sizes can be stacked in series to construct a multi-level series / gradient stacked configuration. For example, along the fluid direction, the pore size gradually decreases from 80 nm to 20 nm. This variation retains the core advantages of the nano-confined compression boundary layer while further dispersing the water flow pressure drop and extending the membrane's lifespan.

[0080] As a third variation of the above embodiments, for industrial mass production, vacuum filtration can be modified into a continuous "belt pressure filtration" or "roll-to-roll filtration membrane forming process". By continuously passing a porous substrate (microporous filter membrane) through a carbon nanotube dispersion tank and applying negative pressure, continuous and large-area production of carbon nanotube woven membranes can be achieved.

[0081] As a fourth variation of the above embodiments, in addition to relying on the "negative pressure" of filtration, it can also be modified to be driven by the "positive pressure" of applying high pressure gas (such as nitrogen pressure filtration) above in a closed container. Similarly, it can use fluid dynamics to directionally guide carbon nanotubes to interweave and form on the microporous filter membrane at the bottom.

[0082] As a fifth variation of the above embodiments, the through-cell electrolyzer of the present invention can be used as the front end, and the generated hydrogen peroxide-rich fluid is not collected but directly enters the downstream module containing the iron-based catalyst (or flows directly through the second cathode with Fenton activity) to achieve in-situ activation of hydrogen peroxide and generate hydroxyl radicals for efficient and advanced oxidation treatment of recalcitrant environmental wastewater.

[0083] As a sixth variation of the above embodiments, this through-cell electrolyzer, due to its small size and efficient operation under low oxygen conditions, can be deformably packaged into a micro-inline reactor and directly connected in series to the water inlet pipe of industrial washing equipment or household washing machines. Utilizing the natural dissolved oxygen in tap water, hydrogen peroxide is generated in situ while the water flow is dynamically injected, achieving online bleaching, sterilization, and decolorization of clothing or industrial fabrics. This provides the laundry industry with a revolutionary "on-demand" green bleaching and sterilization solution, completely eliminating the safety hazards and chemical consumption associated with the transportation, storage, and addition of traditional high-concentration hydrogen peroxide.

[0084] As a seventh variation of the above embodiments, the physical mechanism of the "nanopore-based powerful compression diffusion boundary layer" in this invention essentially solves the mass transfer problem of extremely low concentration substances. Therefore, this membrane electrode and its permeable configuration can be directly applied to the field of water resource recovery. For example, for extremely low concentrations of valuable metal ions (such as lithium, uranium, precious metals, etc.) or high-value organic matter in seawater or industrial wastewater, the electrofiltration system of this invention can significantly overcome the radial diffusion resistance of low-concentration ions, achieving high-throughput, highly selective electrochemical adsorption and targeted recovery of trace strategic resources.

[0085] As an eighth variation of the above embodiments, this invention can be applied to portable disinfection terminals in remote areas and medical field operations: hydrogen peroxide is a recognized highly efficient, residue-free, and environmentally friendly disinfectant. Leveraging the invention's characteristics of having no complex mechanical parts and low-voltage operation, it can be combined with solar photovoltaic panels or micro-batteries to develop a portable pure water / sewage in-situ disinfection device. This device only needs to draw natural water and pump it through a carbon nanotube woven membrane to continuously output a hydrogen peroxide-rich aqueous solution that meets medical disinfection standards. It has enormous application potential in scenarios lacking centralized power supply and oxygen sources, such as drinking water purification in remote areas, disaster area sanitation and epidemic prevention, and sterilization of medical equipment in the field.

[0086] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for synthesizing hydrogen peroxide via carbon nanotube woven membrane electrofiltration, characterized in that, Includes the following steps: S1. Unmodified carbon nanotubes are dispersed in a solvent and ultrasonically treated to obtain a dispersion; S2. The dispersion is placed on a microporous filter membrane. Under pressure, the solvent in the dispersion passes through the microporous filter membrane, and the carbon nanotubes in the dispersion spontaneously interweave, physically overlap, and interlock layer by layer on the surface of the microporous filter membrane under the directional guidance of hydrodynamics, and are assembled in situ to form a three-dimensional network structure of carbon nanotubes, thereby obtaining a binder-free carbon nanotube woven membrane. The three-dimensional network structure of carbon nanotubes has nanoscale interwoven channels with nanoscale pore size. S3. After cleaning and drying the carbon nanotube woven membrane, it is assembled as a cathode in the cathode chamber of the electrolytic cell, and the edges of the carbon nanotube woven membrane are sealed so that the effective reaction area of ​​the carbon nanotube woven membrane completely covers the electrolyte flow section of the cathode chamber. S4. Connect a circuit between the parallel-placed cathode and the anode of the electrolytic cell anode chamber, pump an electrolyte containing dissolved oxygen into the electrolytic cell anode chamber, and after the electrolyte flows through the anode, it is forced to vertically penetrate the nanoscale interwoven channels inside the cathode, where a two-electron oxygen reduction reaction occurs to generate hydrogen peroxide, which then flows out from the electrolytic cell cathode chamber.

2. The method as described in claim 1, characterized in that: The pressure drive is provided by vacuum filtration. During the vacuum filtration process, the solvent in the dispersion penetrates the microporous filter membrane under negative pressure, and the carbon nanotubes are trapped and assembled into the three-dimensional network structure of carbon nanotubes on the surface of the microporous filter membrane through hydrodynamics.

3. The method as described in claim 1, characterized in that: The carbon nanotubes are multi-walled carbon nanotubes.

4. The method as described in claim 1, characterized in that: The carbon nanotubes have an inner diameter of 3 to 10 nm, an outer diameter of 8 to 100 nm, and a length of 1 to 30 μm.

5. The method as described in claim 1, characterized in that: The concentration of dissolved oxygen in the electrolyte is between the concentration of naturally dissolved oxygen without aeration and the concentration of dissolved oxygen with aeration up to oxygen saturation.

6. The method as described in claim 1, characterized in that: The distance between the anode and the cathode is 1-10 mm.

7. The method as described in claim 1, characterized in that: The microporous filter membrane is an organic microporous filter membrane or an aqueous mixed cellulose filter membrane.

8. The method as described in claim 1, characterized in that: The anode is a metal oxide mesh electrode, a platinum mesh electrode, or a stainless steel mesh electrode.

9. The method as described in claim 1, characterized in that: The pore size of the three-dimensional network structure of carbon nanotubes in the carbon nanotube woven membrane is concentrated in the range of 20-50 nm.

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