A high-current multiphase electrode with a vertical array carbon nanocatalytic layer and controllable preparation method and application thereof

Abstract

The application belongs to the field of composite electrode preparation, and particularly relates to a high-current multiphase electrode with a vertical array type carbon nanometer catalytic layer and a controllable preparation method and application thereof. The application mainly synthesizes a vertical array type carbon nanometer catalytic layer with different structural sizes (diameter and height) through a magnetic control guide rail and a synchronous double temperature zone, and assists a chemical vapor deposition method to heat-press a multiphase electrode with different functional layers on a carbon-based composite carrier. Compared with a traditional disordered structure multiphase electrode, the high-current multiphase electrode can maintain a high electric current efficiency of hydrogen peroxide under an industrial large current (300 mA / cm 2 ). The composite electrode is mainly used for in-situ electro-catalytic production of hydrogen peroxide, and under the condition of an industrial large current (300 mA / cm 2 ), the hydrogen peroxide concentration can reach 1-5 wt%, and the current efficiency can be maintained at 80-99%.

Description

Technical Field

[0001] This invention belongs to the field of composite electrode preparation, specifically relating to a high-current multiphase electrode with a vertically arrayed carbon nanocatalytic layer, its controllable preparation method, and its application. Background Technology

[0002] Hydrogen peroxide is a widely used inorganic chemical raw material and an environmentally friendly and efficient oxidant, widely applied in pharmaceutical plants, chemical enterprises, environmental protection, and textile bleaching industries. In 2018, China's hydrogen peroxide production reached 10.29 million tons, a year-on-year increase of 16.5%; in 2019, it reached 10.75 million tons, a year-on-year increase of 4.5%; and in 2020, it reached 14.67 million tons, a year-on-year increase of 36.5%.

[0003] To achieve efficient and large-scale electrosynthesis of H2O2, novel composite electrodes have been developed, offering advantages such as low cost, high usability, and superior performance. These electrodes hold promise for further improving the selectivity and efficiency of oxygen reduction reactions in producing high-concentration H2O2. Electrode fabrication technology was first applied to fuel cells, discovered by the Englishman Grove in 1839. However, with the widespread use of carbon materials in the late 1970s and the emergence of porous carbon-based materials with low-loaded catalysts, the production cost of electrodes has been significantly reduced, expanding their application range to include the electrochemical reduction of various gases, including oxygen, carbon dioxide, and ammonia.

[0004] Vertically arrayed carbon nanostructures have been a research hotspot in recent years due to their unique mechanical, thermal, electrical, and optical properties. The significant advantages of vertical alignment over random orientation are mainly reflected in promising applications in nanoelectronics, field emitters, light absorbers, drug delivery systems, gas sensors, water and molecular sieves, and energy storage devices.

[0005] Since the discovery of vertically arrayed carbon nanostructures, their unique physical and chemical properties, such as high electrical conductivity and mechanical strength, have attracted considerable interest from researchers and engineers. Vertically arrayed carbon nanostructures possess a higher specific surface area, resulting in superior performance compared to traditional electrode materials. This allows for significant improvements in energy efficiency. Controlling the diameter and density of vertically arrayed carbon nanostructures reveals that increasing density leads to increased electrical conductivity and decreased gas permeability. Conversely, increasing the diameter improves the dispersion of catalyst nanoparticles, increasing electrical conductivity but decreasing gas permeability. Therefore, methods for individually controlling the diameter and density of vertically arrayed carbon nanostructures are crucial for the application of novel electrode materials.

[0006] At room temperature and normal pressure, the dissolved oxygen saturation in pure water ranges from 7.5 to 9.0 mg / L, which limits the reduction of O2 on the electrode surface. The vertically arrayed carbon nanotube catalytic layer composite electrode has large pores and a large specific surface area, which facilitates mass transfer between the gas, liquid, and solid phases. It can provide gaseous substances under continuous aeration, while also allowing gas to pass through the pores from the electrolyte into the electrode, thus greatly improving mass transfer efficiency and making it superior to traditional planar electrodes.

[0007] In existing technologies, when growing vertically arrayed carbon nanocatalysts in a CVD tube furnace, a period of low-temperature treatment is required (to allow the precursor to vaporize and volatilize) before high-temperature treatment can proceed. Therefore, the tube furnace needs to be set to a low temperature first, then heated to a high temperature. This time interval between precursor vaporization and catalyst growth prevents the vaporized precursor (carbon source and catalyst) from immediately starting the growth of the vertically arrayed carbon nanocatalyst material at high temperature, resulting in a relatively disordered catalyst structure or making the morphology, diameter, and height of the vertically arrayed structure uncontrollable. Summary of the Invention

[0008] The purpose of this invention is to provide a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer, its controllable preparation method, and its applications. This addresses the problems of unimproved electrodes, which suffer from limited hydrophobicity leading to water flooding, low electron transport rates, few active sites, and small specific surface areas, resulting in low current efficiency, low hydrogen peroxide production, short lifespan, and difficulty in achieving industrial-grade high current densities (over 100 mA / cm²). 2 This method addresses the issues encountered when running and using this technology, and it is also applicable to large-scale industrial production.

[0009] The high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer allows gaseous oxygen to pass through the catalytic layer from the gas phase to the hydrophobic diffusion layer without passing through the electrolyte. Furthermore, the controllable preparation of its structure enables the construction of a superhydrophobic three-phase interface, thereby achieving the efficient generation of H2O2.

[0010] To address the aforementioned issues, this invention provides a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanocatalyst layer. This electrode utilizes a method for controllable fabrication of the vertically arrayed carbon nanocatalyst layer structure, taking advantage of its short electron transport path, high charge transfer efficiency, and excellent gas diffusion capability. Furthermore, its high hydrophobicity is crucial for maintaining a stable three-phase structure over the long term. The controllable fabrication of the vertically arrayed carbon nanocatalyst layer height facilitates rapid electron transfer from the catalyst to the current collector, thereby preventing electron recombination. The controllable fabrication of the vertically arrayed carbon nanocatalyst layer morphology increases the active sites of the electrolyte and promotes ion transport. The layered, ordered support structure accelerates the release of accumulated bubbles, especially under electrowetting conditions, contributing to the sustained and stable maintenance of the electrode's excellent performance. The controllable fabrication of the vertically arrayed carbon nanocatalyst layer diameter facilitates the formation of different pore sizes, and the ordered pore distribution is beneficial for ion transport.

[0011] This high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer can be applied to electrocatalytic devices capable of gas-liquid separation.

[0012] The principle behind increasing hydrogen peroxide production is to achieve the optimal gas-liquid equilibrium state of the electrode. Generally, the better the hydrophobicity of the electrode, the shorter the electron transport path, the higher the charge transfer efficiency, and the stronger the gas diffusion ability, resulting in a faster oxygen mass transfer rate and better performance in electrogenerating hydrogen peroxide. The high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer used in this invention has a unique and controllable vertical array structure. By adjusting its height, diameter, and morphology, a better three-phase interface can be constructed, thereby achieving the optimal gas-liquid equilibrium state of the electrode. This prevents electrowetting under high current density, achieving high hydrogen peroxide production and utilization rates.

[0013] One objective of this invention is to disclose a high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer. The superhydrophobic vertically arrayed carbon nanocatalytic layer is synthesized by chemical vapor deposition using a precursor transport mechanism and a synchronous dual-temperature zone. The vertically arrayed carbon nanocatalytic layer is then thermally transferred onto the electrode under negative pressure to form a high-current multiphase electrode with a vertically arrayed carbon nanocatalytic layer.

[0014] The simultaneous dual-temperature zone refers to the high-temperature zone and the low-temperature zone within the chemical vapor deposition furnace. The temperature of the low-temperature zone is not lower than 190℃, and the temperature of the high-temperature zone is 850-950℃. The precursor consists of a carbon source and a catalyst, with a mass ratio of 7.5-9:1. The catalyst is a metal catalyst with a particle size of 2nm-20nm. When preparing the vertical array carbon nanocatalytic layer, the precursor transport mechanism is used to deliver the precursor to the low-temperature zone. The precursor volatilizes instantaneously in the low-temperature zone. An inert gas is used as a carrier gas to carry the volatilized precursor from the low-temperature zone to the high-temperature zone. Under the action of the catalyst, the carbon source pyrolyzes on the quartz substrate to begin growing the vertical array carbon nanocatalytic material. After continuous growth at 850-950℃ for 25-35 minutes, it is cooled to form the vertical array carbon nanocatalytic layer. The flow rate of the inert gas is 400-600mL / min.

[0015] The precursor transport mechanism is used to transport the ark carrying the precursor to the cryogenic zone, and retrieve the ark after the vertical array structure is fabricated. The precursor transport mechanism can be a magnetically controlled mechanism, such as the magnet and magnetically controlled rail in this invention, or any other mechanism capable of moving the ark carrying the precursor.

[0016] The temperature in the low-temperature zone lies between the carbon source volatilization temperature and the carbon source carbonization temperature. The carbon source selected in this invention has a relatively low volatilization temperature of 170–190°C. After the precursor is pushed into the low-temperature zone, it can volatilize instantly, and then be carried by the carrier gas to the high-temperature zone and carbonized instantly upon falling. If the volatilization rate is slow, it is difficult to quickly grow a vertical array morphology with the catalyst as the core.

[0017] The dual-temperature zone mentioned in this invention does not require a low-temperature program in the tube furnace. Only a high-temperature program needs to be set. When the high temperature reaches 900 degrees Celsius, if the infrared thermometer used to detect the temperature of the low-temperature zone shows that the temperature of the low-temperature zone has reached above 190 degrees Celsius, the boat containing the precursor is pushed along the magnetically controlled guide rail to the pre-marked temperature position, i.e., the low-temperature zone, by a magnet. The low-temperature zone and the high-temperature zone work simultaneously to achieve successful material preparation.

[0018] The dual-temperature zone significantly affects the morphology of the material growth. The instantaneous volatilization rate of the precursor is crucial, as it determines the density of the catalyst deposition on the quartz substrate. A faster precursor volatilization rate results in denser carbon nanotube growth on the quartz substrate, where the mutual compression and dependence between the carbon nanotubes forces them to grow vertically and orderly. Conversely, if the precursor is heated from room temperature to approximately 170–190°C at a certain rate, the volatilization rate slows down, and the resulting material lacks a distinct vertical array structure.

[0019] The dual-temperature zones are closely related to the inert gas flow rate and can work synergistically. The low-temperature zone in the dual-temperature zone is used for the instantaneous volatilization of the precursor, mainly to change the precursor from a solid to a liquid and finally to a gas in a short time (about ten seconds). The role of the low-temperature zone is to rapidly change the state of the precursor in a short time, causing the precursor to volatilize into a gaseous state and float in the low-temperature zone. The appropriate inert gas flow rate can drive an appropriate amount of gaseous precursor to flow to the quartz substrate in the high-temperature zone, thereby starting the growth of the vertical array carbon nanocatalytic layer.

[0020] The optimal location for the quartz substrate is in the center of the tube furnace. This is because the structure of the tube furnace results in a convex temperature distribution, with the highest temperature closer to the center (i.e., the set temperature of 900℃). As the temperature moves away from the center, the temperature gradually decreases towards the furnace inlet and outlet, falling below the set temperature. This is unfavorable for the carbonization and volatilization growth of the material, thus preventing the formation of a vertically aligned array structure of suitable height. Furthermore, the amount of precursor obtained in the center of the tube furnace is also appropriate—neither too much nor too little—allowing for full utilization of the precursor and the growth of a vertically aligned array structure of suitable height.

[0021] The closer the quartz substrate is to the precursor, the more carbon source and catalyst are obtained for growing the vertically arrayed carbon nanocatalyst layer, resulting in an excessively high growth height. If the inert gas flow rate is too low, a large amount of carbon source and catalyst used for growing the vertically arrayed carbon nanocatalyst layer will accumulate in the tube furnace and will not be carried away by the inert gas volatilization, which is not conducive to the formation of the vertically arrayed carbon nanocatalyst layer.

[0022] The amount of carbon source and its packing shape within the tubular furnace both affect the morphology: an optimal carbon source amount of 350-390 mg is best for growing a vertical array morphology. Excessive carbon source (greater than 500 mg) will result in disordered carbon on the resulting array morphology, negatively impacting the gas transport performance of the final product. The carbon source must be stacked in a trapezoidal shape, not randomly. This trapezoidal stacking structure ensures a lower carbon source at the top and a higher amount at the bottom. The lower amount at the top compensates for the carbon source loss before reaching its volatilization point due to inert gas, while the higher amount at the bottom ensures sufficient carbon source for growing the vertical array morphology.

[0023] The optimal ratio of carbon source to catalyst is 8.3:1. An inappropriate ratio will prevent the growth of a vertical array structure. If there is too much carbon source and not enough catalyst, the catalytic performance of the material will be affected. If there is too much catalyst and not enough carbon source, the carbon source will be depleted before the material begins to grow, and the vertical array structure will not be able to grow.

[0024] In the aforementioned high current-carrying multiphase composite electrode, a carbon black and superhydrophobic polymer composite layer serves as the carrier, and a nickel-based multifunctional composite electrode serves as the current collector.

[0025] The preparation steps of the vertical array carbon nanocatalytic layer are as follows: the precursor volatilizes instantaneously in the low temperature region and is carried to the high temperature region with the inert gas, and then falls onto the quartz substrate; the height of the vertical array carbon nanocatalytic layer is controlled by adjusting the position of the quartz substrate and the flow rate of the inert gas; the diameter of the vertical array carbon nanocatalytic layer is controlled by adjusting the size of the CoFeO2 nanoparticles; and the morphology of the vertical array carbon nanocatalytic layer is controlled by adjusting the ratio of carbon source and catalyst.

[0026] Another object of the present invention is to provide a controllable preparation method for a high-current multiphase composite electrode having a vertically arrayed carbon nanocatalytic layer, comprising the following steps:

[0027] (1) Prepare the quartz substrate;

[0028] (2) The carbon source and catalyst are mixed evenly at a mass ratio of 7.5-9:1 as a precursor for growing vertical array carbon nanocatalytic layers; the carbon source and catalyst are stacked in a ladder shape after being mixed evenly; the amount of carbon source does not exceed 500mg.

[0029] (3) Place the quartz substrate in the middle of the chemical vapor deposition furnace. The chemical vapor deposition furnace is a tube furnace. Place the boat containing the precursor on the air inlet side of the tube furnace. Inert gas is introduced to purge the air from the quartz tube of the tube furnace. Then, under the protection of inert gas, the temperature is raised for 2-4 hours and the tube furnace is heated to 850-950℃. The distance between the quartz substrate and the precursor is 10-19cm. The distance between the quartz substrate and the precursor is 10-19cm. This means that when the magnet pushes the boat containing the precursor along the magnetic control rail to the low temperature zone on the left side of the tube furnace, the distance between the precursor and the quartz substrate is such that the precursor can enter the low temperature zone and evaporate instantly. Then, with the movement of the carrier gas, it can reach the high temperature zone in a very short time and fall onto the quartz substrate to start the growth of the vertical array carbon nanocatalytic layer.

[0030] (4) When the temperature in the high-temperature zone of the tube furnace reaches 850-950℃, the temperature in the low-temperature zone of the tube furnace is not lower than 190℃. The boat with the precursor on the gas inlet side of the tube furnace is pushed along the magnetic control rail to the low-temperature zone on the left side of the tube furnace using a magnet. The high-temperature zone in the middle of the tube furnace at 850-950℃ is used for the growth of the vertical array carbon nanocatalytic layer, and the low-temperature zone on the left side of the gas inlet of the tube furnace is used for the instantaneous volatilization of the precursor. The inert gas is used as a carrier gas to carry the instantaneously volatilized precursor from the low-temperature zone to the high-temperature zone and fall onto the quartz substrate. The carbon source begins to pyrolyze and grow the vertical array carbon nanocatalytic material under the action of the catalyst. After continuous growth at 850-950℃ for 25-35 minutes, it is cooled under the protection of inert gas to form the vertical array carbon nanocatalytic layer. The flow rate of the inert gas is in the range of 400-600 mL / min.

[0031] (5) The vertical array carbon nanocatalyst layer is transferred onto the electrode under negative pressure to form a high current-carrying multiphase electrode with the vertical array carbon nanocatalyst layer. The heat transfer process is as follows: the quartz substrate with the vertical array carbon nanocatalyst layer and the electrode are operated under negative pressure. The negative pressure is -0.03 to -0.05 MPa, the transfer pressure is 3 to 5 MPa, the hot pressing temperature is 100 to 110℃, and the hot pressing time is 1 to 15 s. After the negative pressure hot pressing is completed, the pressure is adjusted to the standard atmospheric pressure and the quartz substrate is removed to realize the negative pressure heat transfer of the vertical array carbon nanocatalyst layer.

[0032] Negative pressure thermal transfer allows for better bonding between the catalyst and current collector, reducing intermediate pores, increasing electron transfer rate, and decreasing electrode impedance. Negative pressure also ensures Nafion is evenly distributed across the surface of the arrayed catalyst, minimizing breakage during the thermal transfer process. The transfer time is 1–15 seconds, depending on the thickness of the catalytic layer in the arrayed electrode. For arrayed carbon nanotube layers of 30–40 μm thickness, the transfer time is controlled at 3–10 seconds; for layers of 40–80 μm thickness, the transfer time is controlled at 10–15 seconds. Excessive transfer time (e.g., 5 minutes) can cause the vertically arrayed carbon nanotube catalytic structure to be under pressure for an extended period, leading to structural damage.

[0033] The quartz substrate should be 10-19 cm away from the precursor. Since the precursor volatilizes instantaneously in the low-temperature region and is rapidly carried to the high-temperature region by the carrier gas to grow on the quartz substrate, if the quartz substrate is too close to the precursor, a large amount of carbon source will accumulate instantaneously, resulting in the formation of disordered carbon on the array structure, which is detrimental to the successful negative transfer of the array structure. If the quartz substrate is too far from the precursor, the resulting array structure will be too thin (i.e., too low in height), with poor adhesion to the transfer substrate, also hindering successful negative transfer. A distance of 10-19 cm between the quartz substrate and the precursor ensures a suitable height for the array structure growth, prevents the formation of disordered carbon, and provides good adhesion to the transfer substrate, enabling a relatively complete and successful transfer.

[0034] Preferably, the carbon source is a volatile carbon source such as camphor or sucrose. The mass ratio of carbon source to catalyst in step (2) is 8.3:1. The catalyst is a metal catalyst with a particle size of 2nm to 20nm; the metal catalyst is ferrocene or cobalt iron oxide. Preferably, the catalyst in step (2) can be CoFeO2 nanoparticles.

[0035] The preparation steps of CoFeO2 nanoparticle catalyst are as follows:

[0036] (1) A mixture of 6-7 mM Fe(acac)3, 3-4 mM Co(acac)2, 25-30 mM 1,2-hexadecanediol, 18-20 mM oleic acid and 18-20 mM oleylamine was mixed with a solvent, wherein acac represents acetylacetone;

[0037] (2) Under the protection of an inert gas, the mixture was heated in a solvent from room temperature to 180-220°C and stirred; then, the resulting dark brown mixture was stirred at different reflux temperatures and continuously refluxed for different times to obtain CoFeO2 nanoparticles of different particle sizes.

[0038] The reflux temperature was set to 263–300℃, the heating rate was set to 4–14℃, and the reflux time was set to 30–70 min, so as to prepare CoFeO2 nanoparticle catalysts with a particle size of 2nm–20nm.

[0039] (3) After reflux, cool, dissolve the product and centrifuge;

[0040] (4) Dry the precipitate, which is the catalyst.

[0041] The final objective of this invention is to disclose the application of the aforementioned high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer in improving the yield and current efficiency of in-situ electrocatalytic hydrogen peroxide production or in synergistic degradation of pyridine using an ozone system. In application, due to its unique vertically arrayed structure, the height, diameter, and morphology of the carbon nanocatalytic layer on the electrode can be controllably adjusted, thus visually constructing the three-phase interface. Before catalytic hydrogen peroxide synthesis in the electrocatalytic device, an electrode needs to be installed, with the high-current-carrying multiphase composite electrode with the vertically arrayed carbon nanocatalytic layer serving as the cathode. Hydrogen peroxide production is carried out in the electrocatalytic device. A ruthenium-iridium-titanium electrode (1.5cm × 1.5cm) is installed as the anode in the electrocatalytic device, and 100mL or 30mL of 500mM Na₂SO₄ solution is prepared. The solution circulation flow rate is set to 50mL / min, the pressure is controlled at 2.5-5KPa, the voltage at 4.35-5.02V, the current at 0.45A, the solution pH is adjusted to 7.0, and the reaction is carried out for 2 hours.

[0042] Preferably, the high-current multiphase composite electrode is a cleverly designed CVD method assisted by a self-modified dual-temperature zone magnetically controlled guide rail. The precursor can instantly evaporate at a specified temperature and fall onto the quartz substrate. By adjusting the position of the quartz substrate and the flow rate of the inert gas, the controllable growth (height, morphology, and diameter) of the arrayed carbon nanotubes can be achieved.

[0043] In a preferred embodiment, the controllable preparation process of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer is as follows:

[0044] (1) The size of the quartz substrate (which is a quartz substrate plate) used is 3cm×3cm×3mm. Before synthesis, the quartz substrate needs to be cleaned with acetone or ethanol, then ultrasonically cleaned with pure water, and then smoothed and polished with lens paper.

[0045] (2) The carbon source and catalyst are mixed uniformly at a certain mass ratio as a precursor for growing a vertically arrayed carbon nanocatalytic layer. After the carbon source and catalyst are mixed uniformly, the packing shape is trapezoidal and should not be randomly piled up in the tube furnace. The color is light yellow, and the precursor needs to be gently ground in a mortar. The amount of carbon source is optimally controlled between 350-390 mg and should not exceed 500 mg. The optimal ratio (mass ratio) of carbon source to catalyst is 8.3:1.

[0046] (3) Place the quartz substrate in the center of the tube furnace, and place the boat containing the precursor on the inlet side of the tube furnace. Inert gas is introduced to purge the air from the quartz tubes inside the tube furnace. Then, after heating in an inert gas environment at room temperature for 3 hours, the tube furnace is heated to 900℃. The distance between the quartz substrate and the precursor can be set to 10-19 cm. The optimal choice is that the quartz substrate must be placed in the center of the tube furnace chamber, which is beneficial for the balanced growth of the vertical array structure and the successful negative transfer. The inert gas used in this process is argon, nitrogen, etc.

[0047] (4) When the temperature reaches 900°C inside the tube furnace, immediately use a magnet to push the boat containing the precursor on the inlet side to the pre-marked position on the left side of the tube furnace – namely, the low-temperature zone (not lower than 190°C). The high-temperature zone of 900°C in the middle of the tube furnace is used for the growth of vertically arrayed carbon nanostructures, while the low-temperature zone on the left side of the inlet is used for the instantaneous volatilization of the precursor. At this time, the inert gas acts as a carrier gas, carrying the instantaneously volatilized precursor from the low-temperature zone to the high-temperature zone, and then it falls onto the quartz substrate. The carbon source begins to pyrolyze and grow vertically arrayed carbon nanostructures under the action of the catalyst. After continuous growth at 900°C for 30 minutes, cool to room temperature in an inert gas environment. A vertically arrayed carbon nanocatalytic layer can then be formed, wherein the flow rate of the inert gas ranges from 400 to 600 mL / min. The optimal flow rate is 500 mL / min.

[0048] (5) The vertical array carbon nanocatalyst layer is transferred onto a regular electrode by a negative pressure heat transfer machine to form a high current-carrying multiphase electrode with a vertical array carbon nanocatalyst layer.

[0049] (6) Heat transfer process: The small hot-pressing mold, the quartz catalyst layer (i.e., the quartz substrate with a vertically arrayed carbon nanotube catalyst layer), and the electrode are placed under a negative pressure environment. The negative pressure is -0.03 to -0.05 MPa, the transfer pressure is 3 to 5 MPa, the hot-pressing temperature is 100 to 110℃, and the hot-pressing time is 1 to 15 seconds. After completing the negative pressure hot-pressing, the pressure is adjusted to standard atmospheric pressure and the quartz substrate is removed, thus realizing the negative pressure heat transfer of the catalyst layer.

[0050] Preferably, the carbon source in step (2) is mainly a volatile material such as camphor or sucrose. The mass ratio of carbon source to catalyst is 7.5–9:1. The catalyst is a metal catalyst (ferrocene, cobalt iron oxide) with a particle size of 2 nm–20 nm. If camphor is used as the carbon source, its state needs to be observed before use. If the camphor particles are found to be relatively damp, they need to be dried in a vacuum dryer.

[0051] In a preferred embodiment, the preparation steps of the CoFeO2 nanoparticle catalyst of different sizes in step (2) are as follows: (1) A mixture of 6-7 mM Fe(acac)3, 3-4 mM Co(acac)2, 25-30 mM 1,2-hexadecanediol, 18-20 mM oleic acid and 18-20 mM oleylamine is mixed with 60 mL of benzoyl ether or phenyl ether as a solvent. Wherein acac represents acetylacetone. (2) Under Ar gas flow, the mixture is heated from room temperature to 200 °C in benzoyl ether solvent and stirred for 2 h or in phenyl ether solvent for 30 min. Subsequently, the resulting dark brown mixture is stirred at different reflux temperatures and continuously refluxed for different times to obtain CoFeO2 nanoparticles of different sizes. (3) Set the reflux temperature of the water bath to 263–300℃, the heating rate to 4–14℃, and the reflux time to 30–70 min. Immerse the mixture in a solvent (60 mL of phenyl ether or benzoyl ether) to prepare 2 nm–20 nm CoFeO2 nanoparticle catalyst. (4) After reflux, cool to room temperature and mix the product in 40 mL of anhydrous ethanol. Then, separate the mixture and place it in four centrifuge tubes, centrifuge at 9000–10000 rpm for 8–10 min. After removing the supernatant, mix the precipitate in 30 mL of ethanol. Then, place the mixture in two centrifuge tubes and centrifuge for 5–10 min. Repeat this operation twice. (5) After removing the supernatant, heat and dry the precipitate at 50–60℃ for 12–15 h. Then, a black precipitate is obtained. This black precipitate is the catalyst.

[0052] In a preferred embodiment, to precisely control the size of the CoFeO2 nanoparticles, the reflux temperature of the water bath is set to 265°C, the heating rate is 5°C, the reflux time is 32 min, and the immersion solvent is 60 ml of phenyl ether, to prepare 2-4 nm CoFeO2 nanoparticle catalysts. Setting the reflux temperature of the water bath to 275°C, the heating rate is 8°C, the reflux time is 58 min, and the immersion solvent is 60 ml of benzoyl ether, yields 6-10 nm CoFeO2 nanoparticles. Setting the reflux temperature of the water bath to 298°C, the heating rate is 12°C, the reflux time is 66 min, and the immersion solvent is 60 ml of benzoyl ether, yields 13-20 nm CoFeO2 nanoparticles. The CoFeO2 nanoparticles are prepared through three steps: hydrothermal treatment, centrifugation, and drying, which effectively removes impurities from the catalyst and improves its purity.

[0053] In a preferred embodiment, the diameter-controlled synthesis of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalyst layer requires controlling the flow rates of Ar, Ar+H2 (4%), and acetylene (C2H2) using an electric mass flow meter. The pressure is set to 103 kPa under either Ar+H2 or C2H2 flow conditions. A gas-pumped state is maintained at 1023 K under Ar+H2 flow for 60 minutes. Then, the vertically arrayed carbon nanocatalyst layer is grown by remaining in a C2H2 flow at 1023 K (750 °C) for 10 minutes.

[0054] Preferably, the hot pressing transfer in step (5) requires the preparation of a certain transfer liquid, which is 1 mL of isopropanol and 50 μL of 5 wt% Nafion solution, and is subjected to ultrasonication for 5 min.

[0055] The high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer was fabricated and then cut into electrode products of the same size, each with an effective area of ​​2 cm². 2 .

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] This invention relates to the controllable preparation and application of a high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer, which has controllable diameter, height, and morphology. It is applied to the in-situ electrochemical production of hydrogen peroxide or the degradation of pyridine in a synergistic ozone system under industrial-grade high current.

[0058] This invention utilizes a magnetically controlled rail-assisted method to form a dual-temperature zone and employs CVD to synthesize vertically arrayed carbon nanotube catalytic layers of varying structural sizes. The main focus is on adjusting the diameter and height of the vertically arrayed carbon nanotubes to enhance electrode current carrying capacity and electrocatalytic performance, resulting in an electrode with high current carrying capacity and high catalytic efficiency. This electrode comprises a superhydrophobic vertically arrayed carbon nanotube structure as the catalytic layer, a carbon black and superhydrophobic polymer composite layer as the carrier, and a nickel-based current collector. Compared to traditional disordered multiphase electrodes, this invention's high-current-carrying multiphase electrode can achieve industrial-grade high current (300 mA / cm²) electrocatalytic performance. 2 This composite electrode maintains high current efficiency under high current density conditions. It is primarily used for in-situ electrocatalytic production of hydrogen peroxide, achieving a hydrogen peroxide concentration of 1–5 wt% and maintaining a current efficiency of 80–99% under these conditions.

[0059] The high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer prepared by this invention can controllably adjust the height, diameter and morphology of the carbon nanocatalytic layer structure, thereby better constructing the three-phase interface of the electrode, optimizing various properties of the electrode, significantly improving the performance of the electrode in producing hydrogen peroxide, and enabling the electrode to operate under high current in industrial applications. Its fabrication method is novel, the electrode has good stability, and it is suitable for large-scale industrial production.

[0060] The high-current multiphase composite electrode of the present invention, with a vertically arrayed carbon nanocatalytic layer, has good stability and maintains a high hydrogen peroxide yield even under long-term operation, while also being able to efficiently degrade the recalcitrant substance pyridine. Attached Figure Description

[0061] Figure 1 Electron microscopy image of a high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer prepared according to the present invention;

[0062] Figure 2 The graph shows the yield of hydrogen peroxide obtained in Example 3 and its corresponding current efficiency: a) yield; b) current efficiency.

[0063] Figure 3 The graph shows the yield of hydrogen peroxide and its corresponding current efficiency obtained in Example 4.

[0064] Figure 4 The graph shows the yield of hydrogen peroxide and its corresponding current efficiency obtained in Example 5.

[0065] Figure 5 The yield of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer prepared according to the present invention during long-term operation is shown in the figure.

[0066] Figure 6 This is a schematic diagram of the degradation of pyridine, a recalcitrant substance, using a high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer in conjunction with an ozone system.

[0067] Figure 7 This is a schematic diagram of the structure of each component of a tubular furnace;

[0068] The components include: 1. Air inlet; 2. Air outlet; 3. Magnet; 4. Ark; 5. Magnetically controlled guide rail; 6. Low temperature zone; 7. High temperature zone; 8. Furnace chamber; 9. Tube furnace; 10. Quartz substrate; 11. Quartz tube; 12. Magnetically controlled point. Detailed Implementation

[0069] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0070] In a specific embodiment, three different electrodes were prepared to compare their performance in electrogenerating hydrogen peroxide. These three electrodes were named a conventional hot-pressed electrode, a disordered electrode, and a high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer (abbreviated as: carbon array catalytic layer composite electrode).

[0071] In preparing a high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer, this invention employs an improved CVD tube furnace. The improved CVD tube furnace 9 includes an inlet 1, an outlet 2, a furnace chamber 8, and a quartz tube 11, all of which are existing technologies. A magnet 3 and a magnetically controlled guide rail 5 are located on the inlet side. The magnet is located inside the quartz tube of the tube furnace but not within the furnace chamber, while the magnetically controlled guide rail is located outside the quartz tube. The magnet can push the boat carrying the precursor along the magnetically controlled guide rail, allowing the boat 4 carrying the precursor to enter the low-temperature zone on the left side of the tube furnace (i.e., the left side of the quartz tube). The low-temperature zone is located inside the quartz tube, and the low-temperature zone 6 is... Figure 7 The dotted line in the quartz tube indicates the location of the "ark". This corresponds to high temperature zone 7. Figure 7 The quartz base 10 and above the quartz base are located within the quartz tube. A fixed magnetic control rail is in place, and a movable magnetic control point 12 (a small magnet) is installed within the rail. The magnetic control point 12 and magnet 3 are positioned opposite each other and attract each other. Moving the magnetic control point 12 moves magnet 3 along the magnetic control rail. The boat carrying the precursor is positioned in front of magnet 3, and is thus pushed to the low-temperature zone by magnet 3. Afterward, the magnetic control point 12 returns, causing magnet 3 to return to its original position, preventing the magnet from remaining in the low-temperature zone and causing demagnetization.

[0072] The performance of the high-current-carrying composite electrode with a vertically arrayed carbon nanotube catalytic layer prepared in this invention was tested using an electrocatalytic device. The device employed a ruthenium-iridium-titanium electrode (1.5 cm × 1.5 cm) as the anode and a conventional hot-pressed electrode, a disordered electrode, or a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer as the cathode. The high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer was primarily used as the cathode. Furthermore, the electrocatalytic device underwent certain condition settings optimization to improve the electrocatalytic performance of the high-current-carrying composite electrode with a vertically arrayed carbon nanotube catalytic layer in the production of hydrogen peroxide.

[0073] Example 1

[0074] The specific preparation process of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer in this embodiment is as follows:

[0075] Prepare a quartz substrate: 3cm × 3cm × 3mm. The quartz substrate needs to be cleaned with ethanol first, then ultrasonically cleaned with pure water, and polished with lens paper until smooth and shiny. Sucrose and CoFeO2 catalyst are mixed uniformly at a mass ratio of 8.3:1 as a precursor for growing a vertically arrayed carbon nanotube catalytic layer; the sucrose and catalyst are stacked in a ladder shape after being mixed uniformly; the amount of sucrose is 360mg; the preparation process of CoFeO2 catalyst: a mixture of 6.5mM Fe(acac)3, 3.5mM Co(acac)2, 28mM 1,2-hexadecanediol, 20mM oleic acid, and 20mM oleylamine is mixed with... 60 mL of benzoyl ether was mixed; where acac represents acetylacetone; the mixture was heated from room temperature to 200 °C and stirred for 2 h in benzoyl ether solvent under Ar gas flow; subsequently, the resulting dark brown mixture was stirred at reflux temperature and continuously refluxed for a certain period of time to obtain CoFeO2 nanoparticles; the reflux temperature of the water bath was set to 298 °C, the heating rate was 12 °C, the reflux time was 66 min, and the immersion solvent was 60 mL of benzoyl ether to prepare 13-20 nm CoFeO2 nanoparticles; after reflux, the mixture was cooled to room temperature and then mixed in 40 mL of anhydrous ethanol; then, the mixture was separated and placed in four centrifuge tubes and centrifuged at 9000 rpm for 10 min; after removing the supernatant, the precipitate was mixed in 30 mL of ethanol; then, the mixture was placed in two centrifuge tubes and centrifuged for 5 min; this operation was repeated twice; after removing the supernatant, the precipitate was heated and dried at 55 °C for 12 h; then, a black precipitate was obtained; this black precipitate is the catalyst.

[0076] A quartz substrate is placed in the middle of a chemical vapor deposition furnace (CVD tube furnace). The boat containing the precursor is placed on the inlet side of the tube furnace. Ar is introduced to purge the air from the quartz tube of the tube furnace. After heating for 3 hours under Ar protection, the tube furnace is heated to 900°C. The quartz substrate is 15cm away from the precursor. When the temperature in the high-temperature zone of the tube furnace reaches 900°C, the temperature in the low-temperature zone of the tube furnace is not lower than 190°C. The boat containing the precursor on the inlet side of the tube furnace is pushed along the magnetically controlled guide rail to the low-temperature zone on the left side of the tube furnace using a magnet. The high-temperature zone of 900°C in the middle of the tube furnace is used for the growth of the vertical array carbon nanocatalytic layer, and the low-temperature zone on the left side of the tube furnace inlet is used for the instantaneous volatilization of the precursor. Ar is used as a carrier gas to carry the instantaneously volatilized precursor from the low-temperature zone to the high-temperature zone and fall onto the quartz substrate. The carbon source begins to pyrolyze and grow the vertical array carbon nanocatalytic material under the action of the catalyst. After continuous growth at 900°C for 30 min, it is cooled under Ar protection to form the vertical array carbon nanocatalytic layer. The flow rate of Ar is in the range of 500 mL / min.

[0077] A vertically arrayed carbon nanotube catalytic layer was heat-transferred onto a conventional hot-pressing electrode under negative pressure to form a high-current-carrying multiphase electrode with the vertically arrayed carbon nanotube catalytic layer. The heat transfer process specifically involved operating a quartz substrate with the vertically arrayed carbon nanotube catalytic layer and the conventional hot-pressing electrode prepared in Example 3 under negative pressure (-0.04 MPa), a transfer pressure of 4 MPa, a hot-pressing temperature of 100°C, and a hot-pressing time of 8 seconds. After completing the negative pressure hot-pressing, the pressure was adjusted to standard atmospheric pressure, and the quartz substrate was removed. The vertically arrayed carbon nanotube catalytic layer was successfully transferred onto the conventional hot-pressing electrode. After the transfer, the vertically arrayed carbon nanotube catalytic layer adhered tightly to the catalyst ink layer of the conventional hot-pressing electrode.

[0078] Figure 1 The image shows an electron microscope image of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer prepared in Example 1. The left image shows the vertically arrayed catalyst layer grown on a quartz substrate, showing that the vertical array structure has been successfully formed. The right image is a schematic diagram of the structure of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer, showing that the negative pressure thermal transfer of the vertically arrayed carbon nanocatalytic layer has been achieved.

[0079] Example 2

[0080] The specific preparation process of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer in this embodiment is as follows:

[0081] Prepare a quartz substrate: 3cm × 3cm × 3mm. The quartz substrate needs to be cleaned with ethanol first, then ultrasonically cleaned with pure water, and finally smoothed and polished with lens paper. Different amounts of camphor and ferrocene (ferrocene particle size 14-16nm, purity 98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., molecular formula C) were added. 10 H 10 The ratios (mass ratios) of camphor and ferrocene were Cp:Fe = 12.5:1, Cp:Fe = 10.7:1, Cp:Fe = 8.3:1, and Cp:Fe = 7.5:1, and were mixed evenly to serve as precursors for growing vertically arrayed carbon nanocatalytic layers; the camphor and ferrocene were mixed evenly and stacked in a ladder shape; the amount of camphor was 360 mg.

[0082] A quartz substrate is placed in the middle of a chemical vapor deposition furnace (CVD tube furnace). The boat containing the precursor is placed on the inlet side of the tube furnace. Ar is introduced to purge the air from the quartz tube of the tube furnace. After heating for 3 hours under Ar protection, the tube furnace is heated to 900°C. The quartz substrate is 15cm away from the precursor. When the temperature in the high-temperature zone of the tube furnace reaches 900°C, the temperature in the low-temperature zone of the tube furnace is not lower than 190°C. The boat containing the precursor on the inlet side of the tube furnace is pushed along the magnetically controlled guide rail to the low-temperature zone on the left side of the tube furnace using a magnet. The high-temperature zone of 900°C in the middle of the tube furnace is used for the growth of the vertical array carbon nanocatalytic layer, and the low-temperature zone on the left side of the tube furnace inlet is used for the instantaneous volatilization of the precursor. Ar is used as a carrier gas to carry the instantaneously volatilized precursor from the low-temperature zone to the high-temperature zone and fall onto the quartz substrate. The carbon source begins to pyrolyze and grow the vertical array carbon nanocatalytic material under the action of the catalyst. After continuous growth at 900°C for 30 min, it is cooled under Ar protection to form the vertical array carbon nanocatalytic layer. The flow rate of Ar is in the range of 500 mL / min.

[0083] A vertically arrayed carbon nanotube catalytic layer was transferred onto a conventional hot-pressing electrode under negative pressure to form a high-current multiphase electrode with a vertically arrayed carbon nanotube catalytic layer. The heat transfer process was as follows: a quartz substrate with a vertically arrayed carbon nanotube catalytic layer was subjected to negative pressure operation with the conventional hot-pressing electrode prepared in Example 3. The negative pressure was -0.04 MPa, the transfer pressure was 4 MPa, the hot-pressing temperature was 100°C, and the hot-pressing time was 8 s. After the negative pressure hot-pressing was completed, the pressure was adjusted to standard atmospheric pressure and the quartz substrate was removed, thus realizing the negative pressure heat transfer of the vertically arrayed carbon nanotube catalytic layer.

[0084] Example 3

[0085] This embodiment mainly employs three different electrodes: a high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer, a conventional hot-pressed electrode, and a disordered electrode, operating at 10-350 mA / cm². 2The performance of hydrogen peroxide generation under a certain current density was investigated. 1 g of acidified carbon black (CABOTVXC-72 conductive carbon black), 26 mL of 95% ethanol solution, and 1.2 mL of 60 wt% concentrated polytetrafluoroethylene dispersion were taken, with the acidified carbon black acting as a catalyst and the 60 wt% concentrated polytetrafluoroethylene dispersion acting as a gelling agent. The mixture was stirred for 12 min, sonicated for 35 min, and then dried at 65℃ to form a semi-solid. The semi-solid (catalyst ink) was rolled into spherical shapes and placed above a nickel mesh for later use. It was then placed on a hot press platform, and the appropriate temperature and pressure were adjusted. The hot pressing temperature was 60℃, the hot pressing pressure was 15 MPa, and the pressing time was 20 s, thus producing a carbon black gas diffusion electrode, referred to as a common hot-pressed electrode. Take 10 mg of commercially purchased disordered carbon nanotubes, 2 mL of ethanol solution, and 100 μL of 5 wt% Nafion solution, mix them evenly, sonicate for 30 min, and oscillate 3 times. Then, use a spin coater or a small spray gun to load the carbon black gas diffusion electrode prepared above, referred to as the disordered electrode.

[0086] The high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer in this embodiment was prepared in Example 1.

[0087] Anode: A ruthenium-iridium titanium electrode (1.5cm × 1.5cm) with a cation exchange membrane (Nafion 115 membrane) is used, circulating 0.5M-30mL of sulfuric acid solution at a flow rate of 5mL / min. Cathode: A high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer, a conventional hot-pressed electrode, or a disordered electrode (1.5cm × 1.5cm). Current range: 0.022-0.787A; Voltage range: 1.71-5.86V; Oxygen pressure control conditions: current density 10-100mA / cm³. 2 At an oxygen pressure of 2.5 kPa, the current density is 150 mA / cm². 2 At that time, the oxygen pressure was controlled at 3.5 kPa, and the current density was 200-350 mA / cm². 2 The oxygen pressure was controlled at 4.5 kPa. The effects of adding 0.5 M-30 mL Na2SO4 solution as electrolyte, circulating at a flow rate of 50 mL / min, and with an electrode spacing (i.e., the distance between the cathode and anode) of 3 mm on the H2O2 yield and current efficiency were investigated after 2 hours of operation.

[0088] like Figure 2 The high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer (referred to as the carbon array catalytic layer composite electrode) exhibits the best performance in electro-generating hydrogen peroxide, at 200 mA / cm². 2 The optimal current density is 350 mA / cm². 2The current density is the limiting current density of the carbon array catalyst layer composite electrode. When the applied current density is low, its current efficiency can reach up to 99%. As the current density increases, the current efficiency decreases, and the H2O2 yield of the carbon array catalyst layer composite electrode first increases and then decreases. The optimal current density is 250 mA / cm². 2 Or 300mA / cm 2 At that time, the yield of H2O2 can reach a maximum of 164 mg / h. -1 cm -2 Around, when the current density is 250 mA / cm² 2 Its current efficiency is around 90%, and its current density is 300 mA / cm². 2 At that time, its current efficiency is about 80%. When the current density is 200 mA / cm², its efficiency is approximately 80%. 2 The yield of H2O2 can reach up to 138 mg / h. -1 cm -2 Its current efficiency is as high as 96%. And when the current density reaches 350 mA / cm², it is even higher. 2 At that time, its yield decreased and the current efficiency also decreased significantly, to only about 50%, indicating that it has reached the limit current density of the carbon array catalyst layer composite electrode.

[0089] Example 4

[0090] This embodiment primarily investigates the electrochemical hydrogen peroxide production performance of a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer, prepared using the same process as in Example 2, with conventional hot-pressed electrodes and disordered electrodes serving as controls. Vertically arrayed carbon nanotube catalytic layers of different structural sizes were synthesized via CVD using a magnetron-assisted method to form a dual-temperature zone. The diameter and height of the vertically arrayed carbon nanotubes were adjusted to enhance the electrode's current carrying capacity and electrocatalytic performance, resulting in a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer exhibiting both high current carrying capacity and high catalytic efficiency. Different amounts of camphor and ferrocene were added to achieve ratios of Cp:Fe = 12.5:1, Cp:Fe = 10.7:1, Cp:Fe = 8.3:1, and Cp:Fe = 7.5:1. Cp is the abbreviation for camphor, and Fe is the abbreviation for ferrocene. Anode: A ruthenium-iridium titanium electrode (1.5cm × 1.5cm) with a cation exchange membrane (Nafion 115 membrane) circulating 0.5M-30mL of sulfuric acid solution at a flow rate of 5mL / min. Cathode: A high-current-carrying multiphase composite electrode (1.5cm × 1.5cm) with a vertically arrayed carbon nanotube catalyst layer. Oxygen pressure control is 4.5 kPa. Current density: 200 mA / cm². 2The current was 0.45A and the voltage was 4.16V. The effects of adding 0.5M-100mL Na2SO4 solution as electrolyte, circulating at a flow rate of 50mL / min, and with an electrode spacing of 10mm for 2 hours on the H2O2 yield and current efficiency were investigated.

[0091] like Figure 3 The results show that the high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer exhibits the best performance in the electrogeneration of hydrogen peroxide when the Cp:Fe ratio is 8.3:1. When the Cp:Fe ratio is 8.3:1, the yield of H₂O₂ is significantly increased, reaching 137 mgh. -1 cm -2 With approximately 95% current efficiency, the resulting high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer achieved an unexpectedly high technical effect. However, with other doping ratios, the performance of the high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer in generating hydrogen peroxide was significantly lower, indicating that the other doping ratios were unsuitable.

[0092] Example 5

[0093] This embodiment primarily investigates the electrochemical hydrogen peroxide production performance of a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer under different Ar flow rates, using a conventional hot-pressed electrode and a disordered electrode as controls. The preparation process of the high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer in this embodiment is identical to that in Example 1, except for the Ar flow rate variation. Vertically arrayed carbon nanotube catalyst layers of different structural sizes are synthesized using a CVD method with a dual-temperature zone formed by a magnetron-controlled rail, mainly adjusting the diameter and height of the vertically arrayed carbon nanotubes to enhance the electrode's current carrying capacity and electrocatalytic performance, thus creating a multiphase carbon-based composite electrode with high current carrying capacity and high catalytic efficiency—that is, a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer. Different Ar flow rates are controlled, for example, adjusting the Ar flow rate in the tube furnace to 400 mL / min, 450 mL / min, 500 mL / min, 550 mL / min, and 600 mL / min. Anode: A ruthenium-iridium titanium electrode (1.5cm × 1.5cm) with a cation exchange membrane (Nafion 115 membrane) circulating 0.5M-30mL of sulfuric acid solution at a flow rate of 5mL / min. Cathode: A high-current-carrying multiphase composite electrode (1.5cm × 1.5cm) with a vertically arrayed carbon nanotube catalyst layer. Oxygen pressure control is 4.5 kPa. Current density: 200 mA / cm². 2The current was 0.45A and the voltage was 4.32V. The effects of adding 0.5M-100mL Na2SO4 solution as electrolyte, circulating at a flow rate of 50mL / min, and with an electrode spacing of 10mm for 2 hours on the yield of H2O2 and the current efficiency were investigated.

[0094] like Figure 4 The results show that the carbon array catalyst layer composite electrode exhibits optimal performance in the electro-production of hydrogen peroxide when the Ar flow rate is 500 mL / min. At an Ar flow rate of 500 mL / min, H₂O₂ is produced continuously, stably, and efficiently in the system, with a yield of 136 mg / h. -1 cm -2 The current efficiency is around 94.5%. However, the performance of the carbon array catalyst layer composite electrode made of the grown carbon nanoarray structure with the remaining Ar flow rate is significantly lower, indicating that the remaining Ar flow rate is unsuitable.

[0095] Application Example 1

[0096] This application example primarily utilizes the high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer from Example 1 to investigate the electrogenerated hydrogen peroxide yield under long-term operation. Anode: A ruthenium-iridium titanium electrode (1.5cm × 1.5cm, titanium substrate, ruthenium-iridium plated electrode) with a cation exchange membrane (Nafion 115 membrane) circulating 0.5M-30mL of sulfuric acid solution at a flow rate of 5mL / min. Cathode: A high-current-carrying multiphase composite electrode (1.5cm × 1.5cm) with a vertically arrayed carbon nanotube catalyst layer. Oxygen pressure control was 4.5 kPa. Current density: 200 mA / cm². 2 The current was 0.45A and the voltage was 4.22V. The effects of adding 0.5M-100mL Na2SO4 solution as electrolyte, circulating at a flow rate of 50mL / min, and with an electrode spacing of 10mm on the H2O2 yield and current efficiency were investigated after 10 hours of operation.

[0097] like Figure 5 As shown, the high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer reached its highest concentration (approximately 3.5 wt%) after 10 hours of reaction at a high current density, with a current efficiency of approximately 40%. This is because the H2O2 production environment gradually changes from neutral to acidic. The pH was measured at 3.15 at 6 hours, 2.17 at 8 hours, and 2.05 at 10 hours. As the reaction time increases, the excessively acidic environment is unfavorable for the production and detection of hydrogen peroxide, and the H2O2 concentration gradually reaches an equilibrium state, thus reducing the current efficiency. At 200 mA / cm², the yield reached a higher concentration. 2The experiment demonstrated that the high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanocatalyst layer exhibits excellent performance in the electro-generation of hydrogen peroxide, providing a theoretical basis for its industrial application in high-current electro-generation of hydrogen peroxide.

[0098] Application Example 2

[0099] This application example primarily utilizes the electrocatalytic system for producing hydrogen peroxide using a high-current multiphase composite electrode with a vertically arrayed carbon nanotube catalyst layer, as described in Example 1, in conjunction with an ozone system. It can also degrade pyridine substances. This is because the electro-peroxone technology allows for the in-situ generation of H2O2 at the cathode, thereby activating the production of reactive oxygen species (ROS). The removal of pyridine comes from two reactions: the generation of O3 and ·OH from O3 / H2O2. A 400 mL solution containing 100 mg L... -1 A pyridine solution and 250 mL of 50 mM Na₂SO₄ solution were prepared, followed by the addition of 5 mM tert-butanol (TBA) and 5 mM chloroform (CHCl₃) as ·OH and O₂, respectively. 2- Free radical inhibitors were used to measure the removal efficiency of pyridine. Anode: A cation exchange membrane (Nafion 115 membrane) and a ruthenium-iridium titanium electrode (1.5cm × 1.5cm, titanium substrate, ruthenium-iridium plated electrode) were used, circulating 0.5M-30mL of sulfuric acid solution at a flow rate of 5mL / min. Cathode: A high-current-carrying multiphase composite electrode (1.5cm × 1.5cm) with a vertically arrayed carbon nanotube catalyst layer. Oxygen pressure control was 4.5 kPa. Current density: 200 mA / cm². 2 The current was 0.45A and the voltage was 4.46V. The effect of adding 0.5M-100mL Na2SO4 solution as electrolyte, circulating at a flow rate of 50mL / min, and with an electrode spacing of 10mm on the pyridine removal rate after 15 minutes was investigated. The unmodified electrode (a conventional hot-pressed electrode or a disordered electrode, also used as the cathode) produced a limited amount of hydrogen peroxide, resulting in a limited number of ·OH groups generated during the reaction. Therefore, the pyridine removal rate within 15 minutes was only 65%, and it could not completely degrade pyridine. However, the high-current multiphase composite electrode of this invention, with its vertically arrayed carbon nanotube catalyst layer, achieved a pyridine removal rate close to 100% within 15 minutes. Figure 6 As shown.

[0100] This invention specifically relates to the preparation and application of a high-current-carrying multiphase composite electrode with a vertically arrayed carbon nanotube catalytic layer. The fabrication method is novel, requiring only a single furnace to achieve dual-temperature zone control. This method primarily utilizes magnetically controlled rails to form low-temperature and high-temperature zones, and then uses chemical vapor deposition to grow a vertically arrayed carbon nanotube catalytic layer with controllable diameter, height, and morphology. This unique structure is used to form a three-phase interface, thereby achieving optimal gas-liquid equilibrium and preventing electrowetting and flooding of the electrode surface under high current density, which would otherwise affect the electrode's hydrogen peroxide production performance.

[0101] Because this invention employs a sophisticated design using a self-modified dual-temperature zone magnetically controlled guide rail-assisted CVD method, the precursor can instantly volatilize at a specified temperature and fall onto the quartz substrate. Firstly, adjusting the position of the quartz substrate and the gas flow rate allows for controllable growth of the vertically arrayed carbon nanotube catalytic layer's height. Secondly, adjusting the size of the CoFeO2 nanoparticles allows for controllable growth of the vertically arrayed carbon nanotube catalytic layer's diameter. Thirdly, adjusting the ratio of carbon source to catalyst allows for controllable growth of the morphology of the vertically arrayed carbon nanotube catalytic layer. The superhydrophobic vertically arrayed carbon nanotube structure serves as the catalytic layer, the carbon black and superhydrophobic polymer composite layer as the carrier, and the nickel-based current collector as a multifunctional composite structure, improving the electrode's stability and extending its lifespan, enabling efficient in-situ hydrogen peroxide production. Considering the formation of this special vertical array structure, the specific carbon source and catalyst doping ratio and Ar flow rate of the high-current-carrying multiphase composite electrode with the vertically arrayed carbon nanotube catalytic layer in this invention significantly affect the final in-situ electrocatalytic production yield and current efficiency of hydrogen peroxide.

[0102] The high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer prepared by this invention can controllably adjust the height, diameter and morphology of the carbon nanocatalytic layer structure, thereby better constructing the three-phase interface of the electrode, optimizing various properties of the electrode, significantly improving the performance of the electrode in producing hydrogen peroxide, and enabling the electrode to operate under high current in industrial applications. Its fabrication method is novel, the electrode has good stability, and it is suitable for large-scale industrial production.

[0103] The high-current multiphase composite electrode of the present invention, with a vertically arrayed carbon nanocatalytic layer, has good stability and maintains a high hydrogen peroxide yield even under long-term operation, while also being able to efficiently degrade the recalcitrant substance pyridine.

[0104] This invention achieves efficient in-situ production of hydrogen peroxide, with a yield of 1-5 wt% and a production rate of 137 mg / h under high current density. -1 cm -2 The current efficiency is around 95%, while the yield of the unmodified electrode (i.e., the ordinary hot-pressed electrode and the disordered electrode in Example 1) is 70 mg / h.-1 cm -2 The current efficiency is 40%, indicating that its performance in producing hydrogen peroxide decreases significantly at high current densities.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer, characterized in that, A superhydrophobic vertical array carbon nanocatalyst layer is synthesized by chemical vapor deposition using a precursor carrier mechanism and a synchronous dual-temperature zone. The vertical array carbon nanocatalyst layer is then thermally transferred onto the electrode under negative pressure to form a high-current multiphase electrode with the vertical array carbon nanocatalyst layer. The simultaneous dual-temperature zone refers to the high-temperature zone and the low-temperature zone within the chemical vapor deposition furnace. The low-temperature zone has a temperature of not less than 190℃, and the high-temperature zone has a temperature of 850~950℃. The precursor consists of a carbon source and a catalyst, with a mass ratio of 7.5-9:

1. After the carbon source and catalyst are mixed evenly, they are stacked in a ladder shape. The catalyst is CoFeO2 nanoparticles with a particle size of 2nm~20nm. When preparing the vertical array carbon nanocatalytic layer, the precursor transport mechanism is used to deliver the precursor to the low-temperature zone. The precursor volatilizes instantaneously in the low-temperature zone. An inert gas is used as a carrier gas to carry the volatilized precursor from the low-temperature zone to the high-temperature zone. Under the action of the catalyst, the carbon source pyrolyzes on the quartz substrate to begin growing the vertical array carbon nanocatalytic material. After continuous growth at 850~950℃ for 25-35 minutes, it is cooled to form the vertical array carbon nanocatalytic layer. The flow rate of the inert gas is 400~600mL / min.

2. The high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in claim 1, characterized in that, In the aforementioned high current-carrying multiphase composite electrode, a carbon black and superhydrophobic polymer composite layer serves as the carrier, and a nickel-based multifunctional composite electrode serves as the current collector.

3. The high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in claim 1, characterized in that, The preparation steps of the vertical array carbon nanocatalytic layer are as follows: the precursor volatilizes instantaneously in the low temperature region and is carried to the high temperature region with the inert gas, and then falls onto the quartz substrate; the height of the vertical array carbon nanocatalytic layer is controlled by adjusting the position of the quartz substrate and the flow rate of the inert gas; the diameter of the vertical array carbon nanocatalytic layer is controlled by adjusting the size of the CoFeO2 nanoparticles; and the morphology of the vertical array carbon nanocatalytic layer is controlled by adjusting the ratio of carbon source and catalyst.

4. The controllable preparation method of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in any one of claims 1-3, characterized in that, Includes the following steps: Prepare a quartz substrate; The carbon source and catalyst are mixed uniformly at a mass ratio of 7.5-9:1 as a precursor for growing vertically arrayed carbon nanocatalytic layers; the carbon source and catalyst are stacked in a ladder shape after being mixed uniformly; the amount of carbon source does not exceed 500 mg. The quartz substrate is placed in the middle of the chemical vapor deposition furnace, which is a tube furnace. The boat containing the precursor is placed on the gas inlet side of the tube furnace. Inert gas is introduced to purge the air from the quartz tube of the tube furnace. Then, the tube furnace is heated to 850~950℃ after being heated for 2-4 hours under inert gas protection. The quartz substrate is 10-19cm away from the precursor. When the temperature in the high-temperature zone of the tube furnace reaches 850~950℃, the temperature in the low-temperature zone of the tube furnace is not lower than 190℃. A boat with the precursor mounted on the gas inlet side of the tube furnace is pushed along the magnetically controlled guide rail to the low-temperature zone on the left side of the tube furnace using a magnet. The high-temperature zone in the middle of the tube furnace at 850~950℃ is used for the growth of the vertical array carbon nanocatalytic layer, and the low-temperature zone on the left side of the gas inlet of the tube furnace is used for the instantaneous volatilization of the precursor. An inert gas is used as a carrier gas to carry the instantaneously volatilized precursor from the low-temperature zone to the high-temperature zone and drop it onto the quartz substrate. The carbon source begins to pyrolyze and grow the vertical array carbon nanocatalytic material under the action of the catalyst. After continuous growth at 850~950℃ for 25-35 minutes, it is cooled under the protection of inert gas to form the vertical array carbon nanocatalytic layer. The flow rate of the inert gas is in the range of 400~600mL / min. (5) The vertical array carbon nanocatalyst layer is transferred onto the electrode under negative pressure to form a high current-carrying multiphase electrode with the vertical array carbon nanocatalyst layer. The heat transfer process is as follows: the quartz substrate with the vertical array carbon nanocatalyst layer and the electrode are operated under negative pressure. The negative pressure is -0.03~-0.05 MPa, the transfer pressure is 3~5 MPa, the hot pressing temperature is 100~110℃, and the hot pressing time is 1~15s. After the negative pressure hot pressing is completed, the pressure is adjusted to the standard atmospheric pressure and the quartz substrate is removed to realize the negative pressure heat transfer of the vertical array carbon nanocatalyst layer.

5. The controllable preparation method of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in claim 4, characterized in that, The carbon source is camphor or sucrose.

6. The controllable preparation method of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in claim 4, characterized in that, The mass ratio of carbon source to catalyst in step (2) is 8.3:

1.

7. The controllable preparation method of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in claim 4, characterized in that, The preparation steps of CoFeO2 nanoparticle catalyst are as follows: (1) A mixture of 6-7 mM Fe(acac)3, 3-4 mM Co(acac)2, 25-30 mM 1,2-hexadecanediol, 18-20 mM oleic acid and 18-20 mM oleylamine is mixed with a solvent, wherein acac represents acetylacetone; (2) Under the protection of an inert gas, the mixture was heated in a solvent from room temperature to 180-220°C and stirred; then, the resulting dark brown mixture was stirred at different reflux temperatures and continuously refluxed for different times to obtain CoFeO2 nanoparticles of different particle sizes. The reflux temperature was set to 263~300℃, the heating rate was set to 4~14℃, and the reflux time was set to 30~70min, so as to prepare CoFeO2 nanoparticle catalysts with a particle size of 2nm-20nm. (3) After reflux, cool, dissolve and centrifuge the product; (4) Dry the precipitate, which is the catalyst.

8. The application of the high-current multiphase composite electrode with a vertically arrayed carbon nanocatalytic layer as described in any one of claims 1-3 in improving the yield and current efficiency of in-situ electrocatalytic production of hydrogen peroxide or in synergistic degradation of pyridine by an ozone system.

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