Method and device for removing volatile organic compounds through catalytic oxidation of electric field enhanced chromium-based catalytic electrode

Abstract

The invention provides a method and a device for removing volatile organic compounds through catalytic oxidation of an electric field enhanced chromium-based catalytic electrode. The method comprises the following steps: preparing a catalytic electrode plate with active components including chromium diselenide and zinc oxide; arranging a plurality of electrode plates in parallel and connecting the electrode plates with a direct-current power supply to form a catalytic electrode array with alternative cathodes and anodes; applying 30-80V direct-current voltage to the array and periodically inverting the electrodes; and introducing VOCs-containing gas into the array in a direction parallel to the plate surface. The invention also provides a device for realizing the method. According to the invention, by utilizing the synergistic effect of semiconductors of chromium diselenide (p-type) and zinc oxide (n-type), high-efficiency catalysis is carried out under a low-voltage electric field to generate strong oxidizing substances, so that VOCs (Volatile Organic Compounds) are thoroughly degraded; through periodic electrode reversal operation, electrode passivation is effectively prevented, and catalyst valence cycle and long-term stable operation are realized. The air purifier has the advantages of being low in energy consumption, free of ozone by-products, controllable in cost and long in service life, and is particularly suitable for the field of air purifiers.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of air purification and catalytic oxidation, and particularly relates to a method and device for removing volatile organic compounds by catalytic oxidation of a chromium-based catalytic electrode with enhanced electric field. BACKGROUND

[0002] Volatile organic compounds (VOCs) are a class of organic pollutants with low boiling point and easy volatility, and are an important part of atmospheric pollutants. They mainly come from industrial and living emission links such as petroleum chemical industry, spraying, printing, automobile exhaust, and electronic manufacturing. The emission of VOCs not only leads to the formation of ozone and secondary organic aerosols (SOA), causing regional photochemical smog and haze, but also reacts photochemically with NO x to significantly affect the quality of the atmospheric environment. In addition, many VOCs are toxic, carcinogenic, or mutagenic, and pose a serious threat to human health. Therefore, efficient removal of VOCs has become one of the key problems in the prevention and control of air pollution.

[0003] The ideal way to remove VOCs is to completely degrade them into harmless carbon dioxide and water through oxidation. The existing common methods for removing VOCs mainly include adsorption, thermal catalysis, photocatalytic oxidation, and low-temperature plasma methods. Adsorption relies on activated carbon, molecular sieves, and other adsorbents, which can efficiently capture VOC molecules, but the adsorption capacity is limited, and the subsequent disposal and regeneration process is complex, which may also cause secondary pollution. Thermal catalytic oxidation uses metal oxides or noble metal catalysts to achieve the oxidative decomposition of VOCs at high temperatures, which requires a high reaction temperature, usually 250-500℃, and has high energy consumption. The commonly used noble metal catalysts are prone to deactivation, and the treatment process poses a risk of secondary pollution. Photocatalytic oxidation technology generates strong oxidizing free radicals by exciting electron-hole pairs on semiconductor catalysts under light, which can achieve the oxidative degradation of VOCs 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 has high energy consumption and generates toxic and harmful byproducts such as ozone and nitrogen oxides. In summary, the existing VOCs treatment methods have the problems of high energy consumption, low energy utilization efficiency, multiple byproducts, and incomplete degradation.

[0004] Therefore, it is still a technical problem to be solved how to achieve efficient and complete degradation of VOCs under mild and low-energy conditions, and avoid secondary pollution. SUMMARY

[0005] One of the purposes of the present application is to provide a method for removing volatile organic compounds by catalytic oxidation of chromium-based catalytic electrode with enhanced electric field, which can generate strong oxidizing substances such as hydroxyl radicals and oxygen negative ions from oxygen molecules under mild conditions with low energy consumption, so as to realize efficient and complete degradation of VOCs and avoid secondary pollution.

[0006] The second purpose of the present application is to provide a device for removing volatile organic compounds by catalytic oxidation of chromium-based catalytic electrode with enhanced electric field.

[0007] The technical solution adopted by the present application to achieve one of the purposes is to provide a method for removing volatile organic compounds by catalytic oxidation of chromium-based catalytic electrode with enhanced electric field, which comprises the following steps: Preparation of catalytic electrode plate, the active ingredients of which include chromium diselenide and zinc oxide; Parallel arrangement of multiple catalytic electrode plates and connection to a direct current power supply, with opposite polarity of adjacent electrodes to form alternating anodes and cathodes, thus constituting a catalytic electrode array; Application of direct current voltage to the catalytic electrode array to generate an electric field and perform periodic reversal of the electrodes; Passing of gas containing volatile organic compounds into the catalytic electrode array in a direction parallel to the surface of the catalytic electrode plate.

[0008] The general idea and invention principle of the present application are as follows: The present application proposes a chromium-based electrocatalytic technology based on electric field enhancement, which can catalyze oxygen and water molecules in polluted air to generate reactive oxygen species under low voltage, thus realizing efficient degradation of VOCs. The core of the present application lies in the synergistic catalytic effect of n-type semiconductor ZnO and p-type semiconductor CrSe2, and the long-term activity of the catalyst is maintained through periodic reversal of the electrodes.

[0009] Specifically: at the cathode, the n-type semiconductor ZnO takes the abundant conduction band electrons (e - ) as the main carrier, efficiently adsorbs and catalytically reduces oxygen (O2 •- ), generates superoxide anion radicals (O2 6+ ), hydrogen peroxide (H2O2) and further converts them into hydroxyl radicals (•OH). At the same time, the reduction environment of the cathode also reduces the high-valence chromium (such as Cr 4+ ) in the catalyst to a low-valence state (such as Cr + ).

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

[0011] The applied electric field not only provides driving force for the above reaction, but also significantly promotes the separation and migration rate of electron-hole pairs in ZnO and CrSe2, reduces the reaction energy barrier, and thus improves the overall catalytic efficiency. Further, through periodic reverse electrode operation, the cyclic regeneration of the valence state of the chromium active center is realized (such as Cr 4+ Cr 6+ ). This makes the electrode surface not easily occupied by a single valence state and passivated, thereby greatly improving the reusability and stability of the electrode material. Ultimately, these various active oxygen species (·OH, O2 •- , H2O2) produced continuously and efficiently under the action of an electric field work together to completely oxidize and degrade VOCs molecules into CO2 and H2O.

[0012] Further, the preparation method of the catalytic electrode plate comprises: coating a slurry of the active ingredient, the conductive material and the binder on the electrode substrate, and forming a catalytic coating on the electrode substrate after drying.

[0013] Further, 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 not be enough active sites, and the catalytic efficiency will decrease significantly; if the content is too high, the conductivity and mechanical adhesion of the coating will be poor, affecting the stability and service life of the electrode.

[0014] Further, in the active ingredient, the mass ratio of chromium diselenide to zinc oxide is 1:6 to 6:1, and under this ratio, the band structures of the two semiconductors can be reasonably matched to form a stable and efficient p-n heterojunction interface. The present application utilizes the synergistic effect of CrSe2 (p-type semiconductor) and ZnO (n-type semiconductor) under an electric field, and mixes both as the active ingredient of the catalytic electrode material. In the catalytic process, the electrons in the conduction band act as reducing agents, and the holes in the valence band act as oxidizing agents. If the content of chromium diselenide is too low, the p-n junction will not be formed, the interface electric field will be weakened, and the electron-hole separation efficiency will be reduced, resulting in a decrease in the redox reaction rate; if the content of chromium diselenide is too high, the overall conductivity of the system will decrease, and the chemical stability of chromium diselenide will be poor, which can cause the electrode structure to be loose or the activity to be attenuated. The present application has proved through experiments that when the mass ratio of chromium diselenide to zinc oxide is controlled in the range of 1:6 to 6:1, the interface carrier migration rate and structural stability reach a good balance, and the best catalytic activity and durability can be obtained.

[0015] On the cathode catalytic electrode, n-type semiconductor ZnO plays a major role, and oxygen is adsorbed on the catalytically active sites on the surface of ZnO, which include zinc (Zn), oxygen (O) edge sites, oxygen vacancies, and interlayer defects on the surface. As shown in Equation 1, on these sites, the adsorbed O2molecules are converted into oxygen anions (O2 •- ) by accepting ZnO conduction band electrons (e •- ), and the oxygen anions (O2 •- ) react with water molecules adsorbed on the surface to generate hydrogen peroxide (H2O2), which can then react with O2 + or accept electrons on the surface of ZnO to further generate hydroxyl radicals (•OH) (as shown in Equations 2-4); at the same time, H2O2molecules adsorbed on the surfaces of ZnO and CrSe2enhance the activation energy and can promote the breaking of the O-O bond, and are dissociated into two hydroxyl radicals (•OH) (Equations 5-6). In addition, high-valence chromium is converted into low-valence chromium by receiving electrons from the cathode electrode (Equation 7).

[0016] On the anode catalytic electrode, p-type semiconductor CrSe2plays a major role, and the strong oxidizing holes (h - ) in its valence band can react with water molecules or hydroxyl groups (OH 2- ) adsorbed on the surface to generate hydroxyl radicals (•OH), as shown in Equations 8-9. At the same time, under the synergistic action of low-valence chromium and CrSe2holes, H2O2reacts to generate •OH, and low-valence chromium is converted into high-valence chromium (Equation 10). In addition, the catalytic activity of CrSe2is not only derived from the variable valence characteristics of chromium, but also from the selenium elements in its crystal lattice, which can also participate in and promote the electron transfer process through their own valence changes (such as Se 0 / Se •- ). These active oxygen species (•OH, O2 - , H2O2) have strong oxidizing properties, and as active oxygen species with strong oxidizing ability, they can continuously oxidize and degrade VOCs.

[0017] The applied electric field can effectively promote the above catalytic oxidation process. Specifically, the electric field can promote the migration of electrons in zinc oxide and chromium selenide from the valence band to the conduction band, and further promote the effective separation of electrons in the conduction band and holes in the valence band. In this process, the recombination of electrons and holes is reduced, the migration rate of electrons in the conduction band is accelerated, the electron density on the surface of the catalyst is increased, and the chromium and selenium atoms on the surface can more efficiently provide electrons, thereby promoting the reduction reaction of oxygen. In addition, the electric field can also change the local potential of the zinc oxide and chromium selenide surface, reduce the adsorption energy between the reactant molecules such as oxygen and hydrogen peroxide and the catalyst surface, and enhance the adsorption ability of the reactant molecules. Through this mechanism, the electric field improves the activation efficiency of oxygen molecules and water molecules, so that the catalyst surface can more efficiently participate in the reduction reaction of oxygen and the generation of active oxygen species. The applied electric field can also optimize the distribution of defect sites on the catalyst surface, enhance the catalytic activity of the defect sites, improve the stability of the catalyst, and thus maintain its high efficiency in long-term catalytic reaction. Due to the different roles of zinc oxide and chromium diselenide on the anode and cathode, by mixing and regularly reversing the electrodes, the effective cycle of high-valence and low-valence chromium can be realized, which is beneficial to the repeated use of the electrode.

[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 (Formula 5) H2O2[CrSe2] = 2•OH+ CrSe2 (Formula 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 complex and interface effect, promote each other, and achieve the highest electron-hole separation efficiency and active oxygen species yield.

[0019] Further, the electrode substrate comprises one of copper plate, aluminum plate, nickel plate, and graphite plate, and the thickness is 0.5-2 mm.

[0020] Further, the conductive substance is one or a combination of coconut shell activated carbon, conductive carbon black, conductive graphite, carbon nanotube, supercapacitor activated carbon, and conductive carbon fiber, and the mass percentage of the conductive substance in the catalytic coating is 5%-20%. The conductive substance 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 is too large, affecting the efficiency; and if the content is too high, the active ingredients are excessively squeezed.

[0021] Further, the binder comprises one of ammonium carboxymethylcellulose, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE), for ensuring the adhesion strength of the catalytic coating to the substrate and the cohesion of the catalytic coating itself.

[0022] Further, the coating method of the slurry comprises one of doctor blade method, roll coating method, and dip coating method, and the thickness of the coating formed by the slurry is 50-150 μm. The coating thickness is a key parameter for ensuring that the reaction gas can fully contact the active sites. If the thickness is less than 50 μm, the total active sites are insufficient, and the treatment capacity is limited; and if the thickness exceeds 150 μm, the utilization efficiency of the inner layer catalyst will decrease due to the increased mass transfer resistance, and the coating is prone to cracking and peeling. Preferably, the coating thickness is 75-125 μm, which can ensure high activity while having good stability and economy.

[0023] Further, the spacing between adjacent catalytic electrode plates is 2-10 mm. In the present application, the spacing of the catalytic electrode plates is a key to balance the catalytic efficiency and energy consumption. If the spacing is too small, although the electric field strength is higher, the gas flow resistance will increase sharply, which is prone to dust accumulation and blockage, and increases the process risk of short circuit between electrodes; and if the spacing is too large, the electric field strength between the electrode plates will be significantly weakened, which will result in insufficient driving ability of the catalyst electron migration and insufficient activation of the reactants, and the catalytic efficiency will decrease.

[0024] Further, the voltage of the direct current electric field is 30-80 V. When the voltage is lower than 30 V, the electric field strength is insufficient to effectively drive the separation and migration of electron-hole pairs inside the catalyst and the efficient activation of oxygen molecules, resulting in a low yield of active oxygen species. When the voltage is higher than 80 V, the energy consumption is increased and air breakdown and the generation of ozone and other side reactions may occur. Preferably, the direct current voltage is 50-60 V, which is the best balance point for achieving high catalytic efficiency and low operating energy consumption.

[0025] Existing low-temperature plasma technology generally relies on high-voltage electric fields (typically in the range of several thousand volts to tens of thousands of volts) to generate corona discharge to generate high-energy electrons, ozone and active groups to achieve degradation of volatile organic compounds (VOCs). However, this technology has inherent defects such as high operating voltage (several thousand volts or more), high energy consumption, easy generation of toxic byproducts such as ozone, low energy utilization efficiency and poor device reliability. In contrast, the electric field enhanced electrocatalysis method provided by the present application can efficiently catalyze oxygen molecules to generate hydrogen peroxide (H2O2), superoxide anion radicals (O2 •- ), hydroxyl radicals (•OH) and other active oxygen species on the electrode surface under the condition of a mild low voltage of 30-80 V, achieving complete oxidative decomposition of VOCs. This method not only significantly reduces the voltage requirement and energy consumption, but also has fewer byproducts, high system stability and longer electrode material life due to the fact that the reaction process mainly relies on electrocatalysis. In addition to ensuring degradation efficiency, the method overcomes the high energy consumption and byproduct problems of existing low-temperature plasma technology, and exhibits unique advantages.

[0026] Further, the frequency of the periodic polarity reversal operation is not higher than 0.01 Hz. If the frequency is too high (the interval is too short), the power supply is switched frequently, which is not conducive to stable operation of the device and cannot fully utilize the continuous catalytic capacity of the electrode under single polarity.

[0027] Preferably, the time interval of the periodic polarity reversal operation is 15 minutes to 45 minutes. Research has found that this time range is the optimal result for achieving chromium valence state cyclic regeneration and preventing electrode passivation. If the interval is too short, the catalytic cycle on the electrode surface has not been fully performed and the efficiency is not high. If the interval is too long, the catalyst on one side of the electrode (especially the side acting as the anode) may start to passivate due to the accumulation of a specific valence chromium (such as Cr 6+ ) or the coverage of byproducts, and the activity may irreversibly decay. By reversing the polarity at a fixed time, the electrode that tends to passivate is "refreshed", thereby restoring the activity. Under this preferred time interval, the device can continuously maintain a high removal rate with minimal performance degradation.

[0028] Further, the flow direction of the VOCs-containing gas is parallel to the plate surface of the catalytic electrode plate in the present application. This arrangement optimally matches the catalytic electrode array structure, which not only maximizes the contact of the electric field with the reactants, but also optimizes the mass transfer and residence time. Compared with the flow direction perpendicular to the plate surface, the parallel flow channel design can provide a more controllable gas residence time distribution, ensuring that VOCs molecules have enough opportunity to diffuse to the catalyst surface for reaction. In addition, this flow mode has a synergistic effect with low voltage and periodic reversal operation conditions: at low voltage, a sufficiently long effective reaction path is required to ensure purification efficiency, and a uniform flow field is also conducive to quickly establishing a new stable reaction interface after reversal.

[0029] The technical solution adopted by the second purpose of the present application is to provide a device for removing volatile organic compounds by catalytic oxidation of a chromium-based catalytic electrode with enhanced electric field, comprising: a catalytic electrode array, which is formed by parallel arrangement of a plurality of catalytic electrode plates, and the spacing between adjacent catalytic electrode plates is 2-10 mm; the mass ratio of chromium diselenide to zinc oxide in the active component of the catalytic electrode plate is 1:6 to 6:1; a direct current power supply, which is electrically connected to the catalytic electrode array and is configured to: make the polarity of adjacent electrodes opposite, forming alternating anodes and cathodes; apply a direct current voltage of 30-80V to the catalytic electrode array; and perform periodic reversal operation at a frequency not higher than 0.01 Hz; the arrangement of the catalytic electrode array is configured to make the flow direction of the incoming volatile organic compound-containing gas parallel to the plate surface of the catalytic electrode plate.

[0030] The device provided by the present application is a special equipment for realizing the aforementioned high-efficiency and stable VOCs catalytic oxidation method. The various components of the device and their parameter configurations can synergistically act to excite efficient catalytic oxidation reaction at a low voltage of 30-80V and maintain the long-term activity of the electrode through periodic reversal operation, thereby realizing efficient, stable, and low-energy consumption purification of volatile organic compounds.

[0031] Compared with the prior art, the present application has the following beneficial effects: (1) High efficiency and complete purification: the present application can efficiently catalyze oxygen molecules to produce hydroxyl radicals (·OH), superoxide anions (O2 •- ) and other strong oxidizing active oxygen species by applying a low-voltage direct current electric field of 30-80V on the catalytic electrode array, thereby realizing efficient catalytic oxidation and complete mineralization of volatile organic compounds, and decomposing them into harmless CO2 and H2O.

[0032] (2) Low energy consumption and high safety: Compared with low-temperature plasma technology which needs thousands of volts of high voltage, the present application works in a safe low-voltage range, the energy consumption is significantly reduced, and the generation of harmful by-products such as ozone and nitrogen oxides is fundamentally avoided, realizing the safety purification of man-machine coexistence.

[0033] (3) Good stability and long service life: The present application adopts the strategy of periodic reverse electrode operation combined with CrSe2 / ZnO composite catalytic system. The reverse electrode operation effectively prevents the polarization and passivation of the electrode catalyst, drives the valence state cycle regeneration of the chromium active center, so that the electrode array can maintain high activity for a long time, and the service life is greatly extended.

[0034] (4) Low cost and easy promotion: The catalytic electrode used in the present application does not use noble metals, and the raw material cost is low; its preparation process is simple and mature, and is suitable for large-scale production. The characteristics of high performance, low cost and high stability make it have high application value in the fields of household / vehicle air purifiers, fresh air devices and other civil and industrial fields that require long-term stable operation. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The structure schematic diagram of the device provided for the embodiments of the present application is shown in the figure; Figure 2 The schematic diagram of the chromium-based catalytic electrode prepared in the embodiments of the present application is shown in the figure; Figure 3 The SEM image of the catalytic electrode in Example 2 of the present application is shown in the figure; Figure 4 The catalytic formaldehyde degradation curve of the catalytic electrode in Example 1 and Comparative Example 1 of the present application is shown in the figure; Figure 5 The catalytic formaldehyde degradation curve of the catalytic electrode in Example 2 of the present application is shown in the figure; Among them, 1 is a direct current power supply; 2 is a catalytic electrode plate; 3 is a chromium-based catalyst coating; 4 is a metal substrate; 5 is an electrode lead. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] As 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 method to form a catalyst coating with a thickness of 100 μm. 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. 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, supercapacitor activated carbon, and conductive carbon fiber; 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 voltage of the DC electric field is 30-80 V, and the frequency of the periodic polarity 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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