A method and apparatus for catalytic oxidation removal of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode.

Abstract

This invention provides a method and apparatus for the catalytic oxidation removal of volatile organic compounds (VOCs) using an electric field-enhanced chromium-based catalytic electrode. The method includes: preparing a catalytic electrode plate whose active components include chromium diselenide and zinc oxide; arranging multiple electrode plates in parallel and connecting them to a DC power supply to form a catalytic electrode array with alternating anode and cathode; applying a DC voltage of 30-80V to the array and periodically reversing the electrodes; and introducing VOC-containing gas into the array in a direction parallel to the plate surface. This invention also provides an apparatus for implementing the above method. This invention utilizes the synergistic effect of chromium diselenide (p-type) and zinc oxide (n-type) semiconductors to efficiently catalyze the generation of strong oxidizing substances under a low-voltage electric field, thoroughly degrading VOCs; through periodic electrode reversal, electrode passivation is effectively prevented, achieving catalyst valence state cycling and long-term stable operation. This invention has the advantages of low energy consumption, no ozone byproducts, controllable cost, and long service life, and is particularly suitable for the air purifier field.

Description

Technical Field

[0001] This invention belongs to the field of air purification and catalytic oxidation technology, specifically relating to a method and apparatus for removing volatile organic compounds by catalytic oxidation using an electric field-enhanced chromium-based catalytic electrode. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of low-boiling-point, easily volatile organic pollutants and a significant component of air pollutants. They primarily originate from industrial and domestic emissions sources such as petrochemicals, painting, printing, vehicle exhaust, and electronics manufacturing. VOC emissions not only contribute to the formation of ozone and secondary organic aerosols (SOA), causing regional photochemical smog and haze, but also interact with NOx. x Photochemical reactions occur, significantly impacting atmospheric environmental quality. Furthermore, many VOCs are toxic, carcinogenic, or mutagenic, posing serious threats to human health. Therefore, efficient VOC removal has become one of the key issues in air pollution control.

[0003] The ideal way to remove VOCs is through oxidation, which completely degrades them into harmless carbon dioxide and water. Common existing VOCs removal methods include adsorption, thermocatalysis, photocatalytic oxidation, and low-temperature plasma methods. Adsorption relies on adsorbent materials such as activated carbon and molecular sieves, which can efficiently capture VOCs molecules, but their adsorption capacity is limited, and subsequent treatment and regeneration processes are complex, potentially causing secondary pollution. Thermocatalytic oxidation utilizes metal oxides or noble metal catalysts to oxidize and decompose VOCs under high-temperature conditions, requiring high reaction temperatures, typically 250-500℃. This results in high energy consumption, and commonly used noble metal catalysts are prone to deactivation, posing a risk of secondary pollution. Photocatalytic oxidation technology uses semiconductor catalysts to excite electron-hole pairs under light irradiation, generating highly oxidizing free radicals, achieving VOCs oxidative degradation at low temperatures. However, the light source utilization efficiency is low, the byproduct composition is complex, and the actual degradation efficiency is limited. Low-temperature plasma technology releases a large number of high-energy electrons and active groups through high-voltage discharge to degrade VOCs, but it has high energy consumption and produces toxic and harmful byproducts such as ozone and nitrogen oxides. In summary, existing VOCs treatment methods suffer from prominent problems such as high energy consumption, low energy efficiency, numerous byproducts, and incomplete degradation.

[0004] Therefore, how to achieve efficient and complete degradation of VOCs under mild and low-energy conditions, and avoid secondary pollution, remains a technical challenge that urgently needs to be solved. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for the catalytic oxidation removal of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode. Under mild and low-energy conditions, the method catalyzes oxygen molecules to generate strong oxidizing substances such as hydroxyl radicals and oxygen anions, thereby achieving efficient and thorough degradation of VOCs and avoiding secondary pollution.

[0006] A second objective of this invention is to provide an apparatus for the catalytic oxidation and removal of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode.

[0007] One of the technical solutions adopted by this invention to achieve its objective is: providing a method for catalytic oxidation of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: A catalytic electrode plate is prepared, wherein the active components of the catalytic electrode plate include chromium diselenide and zinc oxide; Multiple catalytic electrode plates are arranged in parallel and connected to a DC power supply, so that the polarities of adjacent electrodes are opposite, forming alternating anodes and cathodes, thus constituting a catalytic electrode array. A DC voltage is applied to the catalytic electrode array to generate an electric field, and periodic reversal operations are performed. A gas containing volatile organic compounds is introduced into the catalytic electrode array in a direction parallel to the surface of the catalytic electrode plate.

[0008] The overall concept and inventive principle of this invention are as follows: This invention proposes a chromium-based electrocatalytic technology based on electric field enhancement, which can catalyze the generation of reactive oxygen species from oxygen and water molecules in polluted air under low voltage, thereby achieving efficient degradation of VOCs. Its core lies in utilizing the synergistic catalytic effect of n-type semiconductor ZnO and p-type semiconductor CrSe2, and maintaining the long-term activity of the catalyst through periodic electrode reversal.

[0009] Specifically: at the cathode, the n-type semiconductor ZnO, with its abundant conduction band electrons (e... - Using ions as the main charge carriers, it efficiently adsorbs and catalytically reduces oxygen (O2), generating superoxide anion radicals (O2). •- The process involves the conversion of hydrogen peroxide (H₂O₂) into hydroxyl radicals (•OH). Simultaneously, the reducing environment at the cathode also allows high-valent chromium (such as Cr₂) in the catalyst to undergo further oxidation. 6+ ) is reduced to a lower valence state (such as Cr) 4+ ).

[0010] At the anode, the p-type semiconductor CrSe2 utilizes its valence band holes (h + With ions as the main charge carriers, these holes can directly oxidize water molecules or hydroxyl groups to generate •OH; at the same time, H2O2 generated and migrated from the cathode can also be catalytically decomposed on the CrSe2 surface by holes or low-valent chromium ions to generate •OH, and in this process, the low-valent chromium is re-oxidized to a high-valent state.

[0011] The applied electric field not only provides the driving force for the above reactions but also significantly promotes the separation and migration rate of electron-hole pairs in ZnO and CrSe2, lowering the reaction energy barrier and thus improving the overall catalytic efficiency. Furthermore, through periodic polarity reversal, the valence state of chromium active centers (such as Cr...) is cyclically regenerated. 4+ Cr 6+ This makes the electrode surface less susceptible to passivation due to the occupation of a single valence state, thus significantly improving the reusability and stability of the electrode material. Ultimately, these various reactive oxygen species (•OH, O2) are continuously and efficiently generated under the influence of the electric field. •- The combined action of CO2 and H2O2 completely oxidizes and degrades VOCs molecules into CO2 and H2O.

[0012] Furthermore, the method for preparing the catalytic electrode plate includes: coating a slurry of the active ingredient, conductive material and binder onto an electrode substrate, and then drying it to form a catalytic coating on the electrode substrate.

[0013] Furthermore, the active ingredient accounts for 60%-90% of the mass percentage of the catalytic coating. The active ingredient is the core of the catalytic reaction, and its content directly affects the number of catalytic sites. If the content is too low, there will be insufficient active sites, and the catalytic efficiency will decrease significantly; if the content is too high, the conductivity and mechanical adhesion of the coating will deteriorate, affecting the stability and service life of the electrode.

[0014] Furthermore, in the active component, the mass ratio of chromium diselenide to zinc oxide is 1:6 to 6:1. Under this ratio, a reasonable match between the band structures of the two semiconductors can be achieved, forming a stable and efficient pn heterojunction interface. This invention utilizes the synergistic effect of CrSe2 (p-type semiconductor) and ZnO (n-type semiconductor) under an electric field, mixing the two and using them simultaneously as the active component of the catalytic electrode material. During the catalytic process, electrons in the conduction band act as a reducing agent, and holes in the valence band act as an oxidizing agent. If the chromium diselenide content is too low, the pn junction formation will be insufficient, the interfacial electric field will weaken, and the electron-hole separation efficiency will decrease, thus leading to a decrease in the redox reaction rate. If the chromium diselenide content is too high, the overall conductivity of the system will decrease, and the chemical stability of chromium diselenide is poor, which can easily cause the electrode structure to become loose or the activity to decay. This invention demonstrates through experiments that when the mass ratio of chromium diselenide to zinc oxide is controlled within the range of 1:6 to 6:1, a good balance is achieved between the interfacial carrier migration rate and structural stability, resulting in optimal catalytic activity and durability.

[0015] In the cathode catalytic electrode, n-type semiconductor ZnO plays a major role. Oxygen is adsorbed onto catalytically active sites on the ZnO surface. These active sites include zinc (Zn), oxygen (O) edge sites, oxygen vacancies, and interlayer defects. As shown in Equation 1, at these sites, adsorbed O2 molecules accept electrons from the ZnO conduction band (electrons). - ) is converted into oxygen negative ions (O2) •- ), oxygen negative ions (O2) •- The oxygen reacts with water molecules adsorbed on the surface to generate hydrogen peroxide (H2O2), which can then react with O2. •- The reaction or acceptance of electrons from the ZnO surface further generates hydroxyl radicals (•OH) (as shown in Equations 2-4); simultaneously, H2O2 molecules adsorb onto the ZnO and CrSe2 surfaces, with enhanced activation energy, promoting the breaking of the OO bond and dissociation into two hydroxyl radicals (•OH) (Equations 5-6). Furthermore, high-valent chromium gains electrons through the cathode electrode and is converted into low-valent chromium (Equation 7).

[0016] At the anodic catalytic electrode, the p-type semiconductor CrSe2 plays a major role, with its valence band containing strongly oxidizing holes (h... + It can react with water molecules or hydroxyl groups (OH) adsorbed on the surface. - The reaction generates hydroxyl radicals (•OH), as shown in formulas 8-9. Simultaneously, under the synergistic effect of low-valent chromium and CrSe2 vacancies, H2O2 reacts to generate •OH, converting low-valent chromium to high-valent chromium (formula 10). Furthermore, the catalytic activity of CrSe2 stems not only from the variable valence of chromium, but also from the selenium element in its lattice, which can undergo valence state changes (such as Se...). 2- / Se 0 These reactive oxygen species (•OH, O2) participate in and promote electron transfer processes. •- H2O2 has strong oxidizing properties. As a reactive oxygen species with strong oxidizing ability, it can continuously oxidize and degrade VOCs.

[0017] An applied electric field can effectively promote the aforementioned catalytic oxidation process. Specifically, the electric field can drive the migration of electrons from the valence band to the conduction band in zinc oxide and chromium selenide, thereby promoting the effective separation of electrons in the conduction band and holes in the valence band. During this process, the recombination of electrons and holes decreases, the electron migration rate in the conduction band accelerates, and the electron density on the catalyst surface increases. This allows chromium and selenium atoms on the surface to donate electrons more efficiently, thus promoting the oxygen reduction reaction. Furthermore, the electric field can also alter the local potential of the zinc oxide and chromium selenide surfaces, reducing the adsorption energy between reactant molecules such as oxygen and hydrogen peroxide and the catalyst surface, enhancing the adsorption capacity of reactant molecules. Through this mechanism, the electric field improves the activation efficiency of oxygen and water molecules, enabling the catalyst surface to participate more efficiently in the oxygen reduction reaction and the generation of reactive oxygen species. The applied electric field can also optimize the distribution of defect sites on the catalyst surface, enhance the catalytic activity of defect sites, improve catalyst stability, and thus maintain its high efficiency in long-term catalytic reactions. Since zinc oxide and chromium diselenide play different roles on the anode and cathode, by mixing the two and performing timed reversal, an effective cycle of chromium in high and low valence states can be achieved, which is beneficial for the reuse of the electrodes.

[0018] Cathode reaction: O2+ ZnO (e - → O2 •- + ZnO (Formula 1) 2O2 •- + 2H₂O → H₂O₂ + O₂ + 2OH⁻ - (Formula 2) O2 •- + H2O2→ 2•OH+O2 (Formula 3) H2O2+ ZnO (e - → •OH+OH - (Formula 4) H2O2[ZnO] = 2•OH+ ZnO (Equation 5) H2O2[CrSe2] = 2•OH+ CrSe2 (Equation 6) Cr 6+ + 2e - → Cr 4+ (Formula 7) Anode reaction: CrSe2(h + ) + H2O → CrSe2+ •OH + H + (Formula 8) CrSe2(h + ) + OH - = •OH (Formula 9) Cr 4+ + H2O2+ CrSe2(h + ) → Cr 6+ + •OH + H2O (Equation 10) Preferably, the mass ratio of chromium diselenide to zinc oxide is 1:1. At this ratio, the two semiconductor materials can form the most effective composite and interface effects, promoting each other and achieving the highest electron-hole separation efficiency and reactive oxygen species yield.

[0019] Furthermore, the electrode substrate includes one of copper plate, aluminum plate, nickel plate, and graphite plate, with a thickness of 0.5-2 mm.

[0020] Furthermore, the conductive material is one or more of the following: coconut shell activated carbon, conductive carbon black, conductive graphite, carbon nanotubes, supercapacitor activated carbon, and conductive carbon fiber. The conductive material accounts for 5%-20% of the mass percentage of the catalytic coating. The conductive material constructs a conductive network inside the electrode, ensuring that the electric field can effectively act on the entire catalytic coating. If the content is too low, the coating resistance will be too high, affecting efficiency; while if the content is too high, it will excessively crowd out the space of the active ingredients.

[0021] Furthermore, the binder includes one of carboxymethyl cellulose ammonium, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE) to ensure the adhesion strength between the catalytic coating and the substrate, as well as its own cohesive force.

[0022] Furthermore, the coating method for the slurry includes one of the following: doctor blade coating, roller coating, and dip coating, and the coating thickness formed by the slurry is 50-150 μm. Coating thickness is a key parameter to ensure sufficient contact between the reactant gas and the active sites. If the thickness is less than 50 μm, the total number of active sites is insufficient, resulting in limited processing capacity; if the thickness exceeds 150 μm, the utilization efficiency of the inner catalyst will decrease due to increased mass transfer resistance, and the coating is prone to cracking and peeling. Preferably, the coating thickness is 75-125 μm, a range that ensures high activity while also possessing good stability and economy.

[0023] Furthermore, the spacing between adjacent catalytic electrode plates is 2-10 mm. In this invention, the spacing of the catalytic electrode plates is crucial for balancing catalytic efficiency and energy consumption. When the spacing is too small, although the electric field strength is higher, it leads to a sharp increase in gas flow resistance, making it prone to dust accumulation and blockage, and increasing the process risk of short circuits between electrodes. On the other hand, if the spacing is too large, it will significantly weaken the electric field strength between the plates, resulting in insufficient driving ability for catalyst electron migration and insufficient activation of reactants, thus reducing catalytic efficiency.

[0024] Furthermore, the voltage of the DC electric field is 30-80 V. When the voltage is below 30 V, the electric field strength is insufficient to effectively drive the electron-hole separation and migration within the catalyst, as well as the efficient activation of oxygen molecules, resulting in a low yield of reactive oxygen species. When the voltage is above 80 V, it increases energy consumption and may trigger side reactions such as air breakdown and ozone generation. Preferably, the DC voltage is 50-60 V, which is the optimal balance point for achieving high catalytic efficiency and low operating energy consumption.

[0025] Existing low-temperature plasma technologies typically rely on high-voltage electric fields (generally in the range of several kilovolts to tens of thousands of volts) to generate corona discharge, producing high-energy electrons, ozone, and active radicals to degrade volatile organic compounds (VOCs). However, this technology suffers from inherent drawbacks such as high operating voltage (above several kilovolts), high energy consumption, easy generation of toxic byproducts such as ozone, low energy utilization efficiency, and poor equipment reliability. In contrast, the electric field-enhanced electrocatalysis method provided by this invention only requires operation under mild low-voltage conditions of 30-80 V to efficiently catalyze the generation of hydrogen peroxide (H2O2) and superoxide anion radicals (O2O2) from oxygen molecules on the electrode surface. •- This method utilizes reactive oxygen species such as hydroxyl radicals (•OH) to achieve complete oxidative decomposition of VOCs. It not only significantly reduces voltage requirements and energy consumption, but also, because the reaction process primarily relies on electrocatalysis, produces fewer byproducts, exhibits high system stability, and extends electrode material lifespan. While ensuring degradation efficiency, it overcomes the high energy consumption and byproduct problems of existing low-temperature plasma technologies, demonstrating unique advantages.

[0026] Furthermore, the frequency of periodic polarity reversal operations should not exceed 0.01 Hz. If the frequency is too high (interval too short), the power supply will switch frequently, which is not conducive to the stable operation of the device and will not be able to fully utilize the continuous catalytic capacity of the electrode under unipolar conditions.

[0027] Preferably, the time interval for the periodic reverse electrode operation is 15 to 45 minutes. Studies have found that this time range is an optimized result for achieving chromium valence state recycling and preventing electrode passivation. If the interval is too short, the catalytic cycle on the electrode surface will not be fully completed, resulting in low efficiency; if the interval is too long, the catalyst on one side of the electrode (especially the anode side) may be affected by specific valence states of chromium (such as Cr). 6+ Excessive accumulation of byproducts or covering of the electrode can cause passivation, leading to irreversible degradation of its activity. By periodically reversing the electrodes, the roles of the anode and cathode are interchanged, "refreshing" the passivating electrodes and restoring their activity. At this optimal time interval, the device can maintain a high removal rate with minimal performance degradation.

[0028] Furthermore, in this invention, the flow direction of the VOC-containing gas is set parallel to the surface of the catalytic electrode plate. This arrangement is optimally matched with the catalytic electrode array structure, maximizing the contact between the electric field and the reactants, and optimizing mass transfer and residence time. Compared to a flow direction perpendicular to the plate surface, the parallel flow channel design provides a more controllable gas residence time distribution, ensuring that VOC molecules have sufficient opportunity to diffuse to the catalyst surface for reaction. In addition, this flow pattern has a synergistic effect with the operating conditions of low voltage and periodic electrode reversal: at low pressure, a sufficiently long effective reaction path is required to ensure purification efficiency, while a uniform flow field also facilitates the rapid establishment of a new stable reaction interface after electrode reversal.

[0029] The second technical solution adopted by the present invention to achieve the objective is: to provide a device for the catalytic oxidation of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode, comprising: The catalytic electrode array consists of multiple catalytic electrode plates arranged in parallel, with a spacing of 2-10 mm between adjacent catalytic electrode plates; the active components of the catalytic electrode plates contain chromium diselenide to zinc oxide in a mass ratio of 1:6 to 6:1. A DC power supply, electrically connected to the catalytic electrode array, is configured to: reverse the polarity of adjacent electrodes to form alternating anodes and cathodes; apply a DC voltage of 30-80V to the catalytic electrode array; and perform periodic electrode reversal operations at a frequency not exceeding 0.01 Hz. The catalytic electrode array is arranged such that the flow direction of the introduced volatile organic compound-containing gas is parallel to the surface of the catalytic electrode plate.

[0030] The device provided by this invention is a dedicated equipment for realizing the aforementioned efficient and stable VOCs catalytic oxidation method. The various components of the device and their parameter configurations can work synergistically to initiate a highly efficient catalytic oxidation reaction at a low voltage of 30-80V, and maintain the long-term activity of the electrodes through periodic electrode reversal operations, thereby achieving efficient, stable, and low-energy-consumption purification of volatile organic compounds.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) High efficiency and thorough purification: This invention can efficiently catalyze the generation of hydroxyl radicals (·OH) and superoxide anions (O2) from oxygen molecules by applying a low-voltage DC electric field of 30-80V to the catalytic electrode array. •- It uses highly reactive oxygen species such as CO2 and H2O to achieve efficient catalytic oxidation and thorough mineralization of volatile organic compounds, decomposing them into harmless CO2 and H2O.

[0032] (2) Low energy consumption and high safety: Compared with low-temperature plasma technology that requires thousands of volts of high voltage, this invention operates in a safe low-pressure range, significantly reducing energy consumption and fundamentally avoiding the generation of harmful byproducts such as ozone and nitrogen oxides, thus achieving safe purification where humans and machines can coexist.

[0033] (3) Good stability and long lifespan: This invention adopts a strategy that combines periodic reversal operation with a CrSe2 / ZnO composite catalytic system. The reversal operation effectively prevents the polarization and passivation of the electrode catalyst, drives the valence state regeneration of the chromium active center, and enables the electrode array to maintain high activity for a long time, thus greatly extending its service life.

[0034] (4) Low cost and easy to promote: The catalytic electrode used in this invention does not use precious metals, and the raw material cost is low; its preparation process is simple and mature, and it is suitable for large-scale production. These characteristics of high performance, low cost and high stability make it extremely valuable for promotion and application in civilian and industrial fields that require long-term stable operation, such as household / vehicle air purifiers and fresh air devices. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the chromium-based catalytic electrode prepared according to an embodiment of the present invention; Figure 3 This is a SEM image of the catalytic electrode in Example 2 of the present invention; Figure 4 The graphs show the formaldehyde degradation curves catalyzed by the catalytic electrode in Example 1 and Comparative Example 1 of this invention. Figure 5 This is a graph showing the formaldehyde degradation catalyzed by the catalytic electrode in Example 2 of the present invention; Among them, 1-DC power supply; 2-catalytic electrode plate; 3-chromium-based catalyst coating; 4-metal substrate; 5-electrode lead. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 and Figure 2As shown, this embodiment of the invention provides an apparatus for the catalytic oxidation of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode, comprising: a catalytic electrode array and a DC power supply 1. The catalytic electrode array consists of multiple catalytic electrode plates 2 arranged in parallel, with a spacing of 2-10 mm between adjacent plates. Each catalytic electrode plate 2 includes a metal substrate 4, a chromium-based catalyst coating 3 applied to both sides of the metal substrate 4, and electrode leads 5. The active components of the chromium-based catalyst coating 3 include chromium diselenide and zinc oxide. The DC power supply 1 is electrically connected to the catalytic electrode array and is configured to: reverse the polarity of adjacent electrodes to form alternating anodes and cathodes; apply a DC voltage of 30-80V to the catalytic electrode array; and perform periodic electrode reversal operations at a frequency not exceeding 0.01 Hz. The catalytic electrode array is arranged such that the flow direction of the introduced volatile organic compound-containing gas is parallel to the surface of the catalytic electrode plates 2.

[0038] The method for catalytic oxidation removal of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode provided in this invention includes the following steps: Step 1: The slurry containing the active ingredient, conductive material, and binder is coated onto the electrode substrate. After drying, a catalytic coating is formed on the electrode substrate, resulting in a catalytic electrode plate. The active ingredient accounts for 60%-90% of the mass percentage of the catalytic coating; the mass ratio of chromium diselenide to zinc oxide in the active ingredient is 1:6 to 6:1; the conductive material is one or more combinations of coconut shell activated carbon, conductive carbon black, conductive graphite, carbon nanotubes, supercapacitor activated carbon, and conductive carbon fiber, accounting for 5%-20% of the mass percentage of the catalytic coating; the electrode substrate includes one of copper plate, aluminum plate, nickel plate, and graphite plate, with a thickness of 0.5-2 mm; the slurry coating method includes one of doctor blade coating, roller coating, and dip coating, with a catalytic coating thickness of 50-150 μm.

[0039] Step 2: Arrange multiple catalytic electrode plates in parallel at a spacing of 2-10 mm and connect them to a DC power supply so that the polarities of adjacent electrodes are opposite, forming alternating anodes and cathodes, thus constituting a catalytic electrode array.

[0040] Step 3: Apply a DC voltage of 30-80 V to the catalytic electrode array to generate an electric field, and perform periodic reversal operations at a frequency not higher than 0.01 Hz, with a time interval of 15 to 45 minutes.

[0041] Step 4: Air containing volatile organic compounds is introduced into the catalytic electrode array in a direction parallel to the surface of the catalytic electrode plate.

[0042] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0043] The main parameters and variables of each embodiment of the present invention are shown in Table 1 below.

[0044] Table 1

[0045] Example 1 This embodiment provides a method for removing formaldehyde by catalytic oxidation using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: Step 1: Mix and grind 300 g of chromium diselenide, 300 g of zinc oxide active ingredient, 66 g of conductive carbon black, and 10 g of carboxymethyl cellulose ammonium for 20 min, then add 1300 ml of water and mix for 20 min to obtain a slurry; coat the slurry onto one side of 20 carbon plates of 325×85×2 mm using a roller coating method to form a catalyst coating with a thickness of 150 μm, vacuum dry at 80℃ for 24 h, then coat the other side of the 20 carbon plates with a catalyst coating of the same thickness, and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0046] Step 2: Arrange 20 catalytic electrodes in a vertical parallel configuration and place them in 20 slots of a 338×338×90mm plexiglass frame. Each electrode is connected to a DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively, and the anode and cathode are arranged alternately. The spacing between adjacent electrode plates is 10 mm, forming a catalytic electrode array.

[0047] Step 3: Apply a 50 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 15 minutes.

[0048] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0049] Example 2 This embodiment provides a method for removing formaldehyde by catalytic oxidation using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: Step 1: Mix and grind 4.5 g chromium diselenide, 4.5 g zinc oxide active ingredient, 0.5 g supercapacitor activated carbon, and 0.1 g carboxymethyl cellulose ammonium for 25 min, then add 10 ml deionized water and mix for 25 min to obtain a slurry; coat the slurry onto one side of 10 60×60×2 mm nickel plates using a scraper method to form a catalyst coating with a thickness of 75 μm, vacuum dry at 80℃ for 24 h, then coat the other side of the 10 nickel plates with a catalyst coating of the same thickness, and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0050] Step 2: Arrange 10 catalytic electrodes in parallel. Each electrode is connected to a DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 4 mm, forming a catalytic electrode array.

[0051] Step 3: Apply a 60 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 30 min.

[0052] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0053] Example 3 This embodiment provides a method for the catalytic oxidation of toluene using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: Step 1: Mix and grind 6 g of chromium diselenide, 2 g of zinc oxide active ingredient, 1 g of coconut shell activated carbon, and 0.2 g of polyvinylidene fluoride for 30 min, then add 15 ml of NMP solvent and mix and stir for 20 min to obtain a slurry; coat the slurry onto one side of 10 50×50×1 mm copper plates by roller coating to form a catalyst coating with a thickness of 125 μm, vacuum dry at 80℃ for 48 h, then coat the other side of the 10 copper plates with a catalyst coating of the same thickness, and vacuum dry at 80℃ for 48 h to obtain the catalytic electrode.

[0054] Step 2: Arrange 10 catalytic electrodes in parallel. Each electrode is connected to a DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 5 mm, forming a catalytic electrode array.

[0055] Step 3: Apply a 70 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 45 min.

[0056] Step 4: Air containing toluene is introduced into the electrode array in a direction parallel to the electrode plates. The toluene is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0057] Example 4 This embodiment provides a method for removing formaldehyde by catalytic oxidation using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: Step 1: Mix and grind 7.2g chromium diselenide, 1.2g zinc oxide active ingredient, 0.5g conductive carbon fiber, and 0.3g sodium carboxymethyl cellulose for 25 min, then add 12.5 ml deionized water and stir for 20 min to obtain a slurry. Coat the slurry onto one side of eight 60×60×2mm graphite plates using a doctor blade method to form a 50 μm thick catalyst coating. After vacuum drying at 80℃ for 24 h, coat the other side of the eight graphite plates with the same thickness of catalyst coating and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0058] Step 2: Arrange the 8 catalytic electrodes in parallel. Each electrode is connected to a DC power supply through a wire. The two adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 2 mm, forming a catalytic electrode array.

[0059] Step 3: Apply an 80 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 30 min.

[0060] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0061] Example 5 This embodiment provides a method for removing formaldehyde by catalytic oxidation using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: Step 1: Mix and grind 1 g of chromium diselenide, 6 g of zinc oxide active ingredient, 1 g of conductive graphite, and 0.2 g of polytetrafluoroethylene for 20 min, then add 10 ml of NMP solvent and mix for 20 min to obtain a slurry. Coat the slurry onto one side of six 65×65×0.5 mm aluminum plates using a doctor blade method to form a catalyst coating with a thickness of 75 μm. After vacuum drying at 80℃ for 24 h, coat the other side of the six aluminum plates with a catalyst coating of the same thickness and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0062] Step 2: Arrange the 6 catalytic electrodes in parallel. Each electrode is connected to a 30V DC power supply through a wire. The two adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately. The spacing between adjacent electrode plates is 8 mm, forming a catalytic electrode array.

[0063] Step 3: Apply a 30 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 30 min.

[0064] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0065] Example 6 This embodiment provides a method for removing formaldehyde by catalytic oxidation using an electric field-enhanced chromium-based catalytic electrode, comprising the following steps: Step 1: Mix and grind 4 g of chromium diselenide, 4 g of zinc oxide active ingredient, 0.5 g of conductive carbon fiber, and 0.3 g of sodium carboxymethyl cellulose for 25 min, then add 15 ml of deionized water and mix for 20 min to obtain a slurry. Coat the slurry onto one side of 10 60×60×3 mm graphite plates using a doctor blade to form a 100 μm thick catalyst coating. After vacuum drying at 80℃ for 24 h, coat the other side of the 10 graphite plates with a catalyst coating of the same thickness and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0066] Step 2: Arrange 10 catalytic electrodes in parallel. Each electrode is connected to a 60 V DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 5 mm, forming a catalytic electrode array.

[0067] Step 3: Apply a 60 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 30 min.

[0068] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0069] Comparative Example 1 This comparative example demonstrates a method for removing formaldehyde by adsorption with pure activated carbon. The quality of the active material and the experimental framework are the same as in Example 1.

[0070] Comparative Example 2 This comparative example uses a commercial photocatalytic filter. The filter assembly method is the same as in Example 1. No current is applied to the filter, and all other experimental conditions are the same as in Example 1.

[0071] Comparative Example 3 The difference between this comparative example and Example 2 is that a single active ingredient (chromium diselenide) is used to prepare the catalytic electrode, and the catalytic oxidation is used to remove formaldehyde. The specific method includes the following steps: Step 1: Mix and grind 9 g of chromium diselenide active ingredient, 0.5 g of supercapacitor activated carbon, and 0.1 g of carboxymethyl cellulose ammonium for 25 min, then add 10 ml of deionized water and mix for 25 min to obtain a slurry; coat the slurry onto one side of 10 60×60×2 mm nickel plates using a scraper method to form a catalyst coating with a thickness of 75 μm, vacuum dry at 80℃ for 24 h, then coat the other side of the 10 nickel plates with a catalyst coating of the same thickness, and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0072] Step 2: Arrange 10 catalytic electrodes in parallel. Each electrode is connected to a DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 4 mm, forming a catalytic electrode array.

[0073] Step 3: Apply a 60 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 30 min.

[0074] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0075] Comparative Example 4 The difference between this comparative example and Example 2 is that a single active ingredient (zinc oxide) is used to prepare the catalytic electrode, and the catalytic oxidation is used to remove formaldehyde. The specific method includes the following steps: Step 1: Mix and grind 9 g of zinc oxide active ingredient, 0.5 g of supercapacitor activated carbon, and 0.1 g of carboxymethyl cellulose ammonium for 25 min, then add 10 ml of deionized water and mix for 25 min to obtain a slurry; coat the slurry onto one side of 10 60×60×2 mm nickel plates using a scraper method to form a catalyst coating with a thickness of 75 μm, vacuum dry at 80℃ for 24 h, then coat the other side of the 10 nickel plates with a catalyst coating of the same thickness, and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0076] Step 2: Arrange 10 catalytic electrodes in parallel. Each electrode is connected to a DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 4 mm, forming a catalytic electrode array.

[0077] Step 3: Apply a 60 V DC voltage to the catalytic electrode array to generate an electric field, and perform a reversal operation of the DC power supply every 30 min.

[0078] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0079] Comparative Example 5 The difference between this comparative example and Example 2 is that, after applying a DC electric field to the catalytic electrode array, no electrode reversal operation is performed. The specific method includes the following steps: Step 1: Mix and grind 4.5 g chromium diselenide, 4.5 g zinc oxide active ingredient, 0.5 g supercapacitor activated carbon, and 0.1 g carboxymethyl cellulose ammonium for 25 min, then add 10 ml deionized water and mix for 25 min to obtain a slurry; coat the slurry onto one side of 10 60×60×2 mm nickel plates using a scraper method to form a catalyst coating with a thickness of 75 μm, vacuum dry at 80℃ for 24 h, then coat the other side of the 10 nickel plates with a catalyst coating of the same thickness, and vacuum dry at 80℃ for 24 h to obtain the catalytic electrode.

[0080] Step 2: Arrange 10 catalytic electrodes in parallel. Each electrode is connected to a DC power supply via a wire. Adjacent electrode plates are the anode and cathode, respectively. The anode and cathode are arranged alternately, and the spacing between adjacent electrode plates is 4 mm, forming a catalytic electrode array.

[0081] Step 3: Apply a 60 V DC voltage to the catalytic electrode array to generate an electric field, without performing a reversal operation.

[0082] Step 4: Formaldehyde-containing air is introduced into the electrode array in a direction parallel to the electrode plates. The formaldehyde is removed by catalytic oxidation using the electric field generated by the chromium-based catalytic electrode array.

[0083] Application performance testing In all the above embodiments and comparative examples, the concentration of organic pollutant gas in the air was set to 30 ppm, and the introduction time was set to 120 min. The concentration of organic pollutant gas after treatment in each embodiment and comparative example was tested, and the removal rate was calculated, as shown in Table 2 below.

[0084] Table 2

[0085] As can be seen from the above table, The electric field-enhanced chromium-based catalytic electrode catalytic oxidation method provided in Examples 1-6 of this invention exhibits highly efficient removal capabilities for various types of volatile organic compounds (VOCs) such as formaldehyde and toluene, with removal rates exceeding 89.0% within 120 minutes of testing. Compared to Examples 3-5, Examples 2 and 6 used a voltage of 60V, a 30-minute electrode reversal interval, and controlled the mass ratio of chromium diselenide to zinc oxide in the active ingredient to be 1:1, achieving removal rates higher than 90%. This demonstrates that optimizing the electric field conditions and catalyst composition can significantly enhance and maintain the reactivity of the catalytic electrode.

[0086] Comparative Example 1 used activated carbon to adsorb formaldehyde. Although it showed a high removal rate at 60 minutes, its mechanism was physical adsorption, which meant it would quickly reach saturation and become ineffective, failing to achieve sustained degradation of pollutants (e.g., Figure 4 (As shown). In Comparative Example 2, when using a commercial photocatalyst as the catalytic medium, the removal rate was only 62.8% after 120 minutes. In contrast, Example 1 of the present invention achieved a removal rate as high as 98.90% in the same time period, demonstrating that the electrocatalytic method provided by the present invention can decompose VOCs more efficiently and thoroughly.

[0087] Comparative Examples 3 and 4 used chromium diselenide or zinc oxide alone as the active ingredients, with removal rates of only 25.65% and 18.60% respectively under the same test conditions. This result is significantly different from Example 2, fully demonstrating that the present invention, by using chromium diselenide and zinc oxide in a specific ratio (e.g., 1:1), produces a significant synergistic enhancement effect. Comparative Example 5, compared to Example 2, did not perform the electrode reversal operation, and the removal rate decreased to 64.17%. This proves that periodic electrode reversal can effectively prevent electrode polarization and catalyst deactivation, ensuring long-term, stable operation.

[0088] In summary, this invention, through a CrSe2 / ZnO composite catalytic system combined with an optimized DC electric field and periodic reversal operation, overcomes the shortcomings of existing technologies such as low efficiency, easy saturation, and insufficient stability, and provides a catalytic oxidation solution with high degradation efficiency, good stability, and applicability to a variety of VOCs.

[0089] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for catalytic oxidation removal of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode, characterized in that, Includes the following steps: A catalytic electrode plate is prepared, wherein the active components of the catalytic electrode plate include chromium diselenide and zinc oxide; Multiple catalytic electrode plates are arranged in parallel and connected to a DC power supply, so that the polarities of adjacent electrodes are opposite, forming alternating anodes and cathodes, thus constituting a catalytic electrode array. A DC voltage is applied to the catalytic electrode array to generate an electric field, and periodic reversal operations are performed; the DC voltage is 30-80 V. A gas containing volatile organic compounds is introduced into the catalytic electrode array in a direction parallel to the surface of the catalytic electrode plate.

2. The method according to claim 1, characterized in that, The method for preparing the catalytic electrode plate includes: coating a slurry of the active ingredient, conductive material and binder onto an electrode substrate, and then drying it to form a catalytic coating on the electrode substrate.

3. The method according to claim 2, characterized in that, The active ingredient accounts for 60%-90% of the mass percentage of the catalytic coating; the mass ratio of chromium diselenide to zinc oxide in the active ingredient is 1:6 to 6:

1.

4. The method according to claim 2, characterized in that, The electrode substrate includes one of copper plate, aluminum plate, nickel plate, and graphite plate, with a thickness of 0.5-2 mm.

5. The method according to claim 2, characterized in that, The conductive material is one or more of coconut shell activated carbon, conductive carbon black, conductive graphite, carbon nanotubes, and conductive carbon fibers; the conductive material accounts for 5%-20% of the mass percentage of the catalytic coating.

6. The method according to claim 2, characterized in that, The coating method of the slurry includes one of the following: doctor blade coating, roller coating, and dip coating; the thickness of the catalytic coating is 50-150 μm.

7. The method according to claim 1, characterized in that, The spacing between adjacent catalytic electrode plates is 2-10 mm.

8. The method according to claim 1, characterized in that, The frequency of the periodic reversal operation is no higher than 0.01 Hz.

9. The method according to claim 8, characterized in that, The time interval for the periodic reversal operation is 15 to 45 minutes.

10. An apparatus for the catalytic oxidation of volatile organic compounds using an electric field-enhanced chromium-based catalytic electrode, characterized in that, include: The catalytic electrode array consists of multiple catalytic electrode plates arranged in parallel, with a spacing of 2-10 mm between adjacent catalytic electrode plates. In the active components of the catalytic electrode plate, the mass ratio of chromium diselenide to zinc oxide is 1:6 to 6:

1. A DC power supply, electrically connected to the catalytic electrode array, is configured to: reverse the polarity of adjacent electrodes to form alternating anodes and cathodes; apply a DC voltage of 30-80V to the catalytic electrode array; and perform periodic electrode reversal operations at a frequency not exceeding 0.01 Hz. The catalytic electrode array is arranged such that the flow direction of the introduced volatile organic compound-containing gas is parallel to the surface of the catalytic electrode plate.

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