Three-chamber device and method for preparing methane by photovoltaic driving of carbon dioxide and simultaneously purifying heavy metal wastewater

Abstract

The invention relates to the technical field of electrochemical energy storage, and provides a three-chamber device and method for preparing methane by photovoltaic driving of carbon dioxide and simultaneously purifying heavy metal wastewater. The device comprises structures and components such as a carbon dioxide gas tank, a methane storage tank, a heavy metal wastewater liquid inlet tank, a cathode region, a cathode electrode, an anion exchange membrane, a middle region, an oxygen storage tank, an anode electrode, an anode region, a centrifugal machine, a storage battery, a photovoltaic panel, a vacuum filter, a heavy metal sediment collecting tank and a reclaimed water storage tank. CO2 is driven to be subjected to a reduction reaction at the cathode to generate and store CH4, O2 is generated and stored at the anode, the middle area utilizes OH <-> generated by the cathode reaction to purify heavy metal wastewater, heavy metal precipitates and recycled water are obtained through separation, CO2 recycling, wastewater purification and energy storage are coordinated, and secondary pollution is avoided.

Description

A three-chamber device and method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater Technical Field

[0001] This invention relates to the fields of electrochemical energy storage technology and environmental protection technology, specifically to a three-chamber device and method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater. Background Technology

[0002] Global carbon dioxide emissions continue to rise, and the resulting greenhouse effect poses a severe threat to ecosystems and human society. Current methods for carbon dioxide treatment mainly include carbon capture and storage (CCS) and carbon capture and utilization (CCU). While CCS technology can achieve long-term carbon dioxide storage, it suffers from high costs and potential leakage risks. For example, Chinese invention patent CN120662083A discloses a long-term stable carbon dioxide absorbent, its preparation method, and its application. The raw materials for preparing the carbon dioxide absorbent include quaternary ammonium salt hydrogen bond acceptors, amine compounds, alcohol hydrogen bond donors, and enhancers. This carbon dioxide absorbent not only exhibits excellent absorption and desorption effects but also innovatively incorporates enhancers. However, this method places higher demands on equipment, potentially increasing initial investment and maintenance costs.

[0003] Heavy metal wastewater (containing Cd) generated from industrial production (such as electroplating, metallurgy, and chemical processes) 2+ Ni 2+ Mn 2+ Heavy metal ions, if discharged directly without effective treatment, will accumulate through the food chain, harming human health and the ecological environment. Existing heavy metal wastewater treatment methods, such as electrochemical oxidation, take manganese ion removal as an example. Chinese invention patent CN119736640A discloses a manganese removal method that utilizes pulsed potential regeneration of permanganate ions and in-situ coupled organic matter oxidation. This method uses pulsed electrolysis technology to oxidize divalent manganese ions to permanganate ions, forming a redox cycle to achieve manganese removal, thus solving the problem of insufficient manganese removal efficiency in traditional methods. However, this method is less effective in environments containing high concentrations of complex organic matter or Cl-. - In wastewater systems with coexisting ions, organic matter and Mn 2+ Competing for anodic oxidation sites, Cl - It may also generate Cl2, which not only interferes with the manganese removal reaction and easily causes secondary pollution, but also limits its application scenarios. At the same time, the generated MnO4 has strong oxidizing properties, which will accelerate anodic corrosion and passivation. Furthermore, negative potential regeneration cannot completely remove the MnO2 deposits on the electrode surface, resulting in short electrode life, frequent shutdowns for replacement, high maintenance costs, and impact on continuous operation efficiency.

[0004] Furthermore, current technologies for treating carbon dioxide and heavy metal wastewater are mostly single-target approaches, lacking integrated technologies that can treat both simultaneously and achieve "waste-to-waste treatment," resulting in complex processes and serious resource waste.

[0005] Therefore, there is an urgent need to develop an integrated device that is low-cost, low-polluting, and can synergistically treat carbon dioxide and heavy metal wastewater. On the one hand, by directionally converting carbon dioxide into methane, a coupling of the "carbon cycle" and the "energy cycle" can be achieved. On the other hand, during the electrochemical reaction process, heavy metal ions in the wastewater react with OH- ions generated at the cathode. - A chemical reaction occurs, and after subsequent precipitation and filtration, heavy metals can be separated and recovered, and wastewater can be purified and recycled without secondary pollution. Moreover, the precipitation reaction occurs in the intermediate zone and has no effect on the electrochemical reactions in the cathode and anode zones, nor will it corrode the cathode and anode electrodes. Summary of the Invention

[0006] The purpose of this invention is to provide a three-chamber device and method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater, achieving the synergistic treatment and purification of CH4 and O2 with heavy metal wastewater. The device employs a three-chamber structure design, with each chamber having a clearly defined function and working in synergy: the cathode region is used for CH4 and OH... - The device utilizes a central zone for heavy metal wastewater precipitation and an anode zone for O2 generation. Through directional mass transfer design of the anion exchange membrane, selection of copper-based catalytic electrodes, and a filtration structure combining a centrifuge and a vacuum filter, it significantly improves CO2 conversion efficiency and heavy metal ion removal rate. Ultimately, it achieves the dual goals of energy storage and wastewater purification, addressing the problems of existing technologies that often employ single-objective approaches to CO2 and heavy metal wastewater treatment, resulting in complex processes, high costs, and severe secondary pollution.

[0007] To achieve the above-mentioned objectives, we adopt the following technical solution: The present invention proposes a three-chamber device for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater, characterized in that it comprises a cathode region, an intermediate region, and an anode region connected in sequence; the cathode region and the intermediate region are separated by anion exchange membrane I, and the intermediate region and the anode region are separated by anion exchange membrane II; a cathode electrode is disposed in the cathode region; an anode electrode is disposed in the anode region; the bottom of the cathode region is connected to a carbon dioxide gas tank via a pipeline; the cathode region is connected to a methane storage tank via a pipeline; the anode region is connected to an oxygen storage tank via a pipeline; the top of the intermediate region is connected to a heavy metal wastewater inlet tank via a pipeline; the bottom of the intermediate region is connected to a centrifuge, the bottom of the centrifuge is connected to a vacuum filter, the vacuum filter is connected to a heavy metal precipitation collection tank, and the top of the centrifuge and the vacuum filter are respectively connected to a reclaimed water storage tank; a photovoltaic panel is connected to a battery, and the positive and negative terminals of the battery are respectively connected to the anode electrode and the cathode electrode.

[0008] The cathode electrode is a polymer-modified copper-based catalytic electrode; the anode electrode is a platinum (Pt) electrode; the anion exchange membrane can achieve OH- - The directional movement of heavy metal ions from the cathode region to the intermediate region, and then from the intermediate region to the anode region, achieves the precipitation of heavy metal ions and replenishment of OH groups at the anode. - The purpose is to prevent heavy metal ions from entering the cathode and anode areas; the shell of the three chambers consisting of the cathode area, the intermediate area, and the anode area is made of polytetrafluoroethylene (PTFE), which has excellent resistance to strong acids and alkalis and resistance to heavy metal ion corrosion.

[0009] The electrolyte in the cathode region is NaHCO3 with a concentration between 0.05M and 2M; the electrolyte in the anode region is a mixture of KOH and NaHCO3, both with a concentration between 0.05M and 2M; the liquid in the heavy metal wastewater inlet tank contains heavy metal ions (X). n+ X n+ Can be Cd 2+ Ni 2+ Mn 2+ These exist in solution in ionic form and can react with OH-. - Wastewater that produces heavy metal ions that form insoluble hydroxide precipitates.

[0010] This invention also proposes a method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater, characterized by the following steps: Step 1: Introducing NaHCO3 electrolyte into the cathode region and KOH and NaHCO3 electrolyte into the anode region; Step 2: Introducing a CO2 gas source into the cathode region of the device, while simultaneously introducing heavy metal ions (X) into the intermediate region. n+Wastewater; Step 3: Photovoltaic panels provide power to the device, and the positive and negative terminals of the battery are connected to the anode and cathode electrodes, respectively; Step 4: An oxidation reaction occurs at the anode to generate O2, which is then transported to the oxygen storage tank through a pipeline; Anode reaction formula: 4OH - -4e - =O2↑ + 2H2O; At the cathode, CO2 is reduced to produce CH4 and OH. - CH4 is collected in the methane storage tank; cathode reaction: CO2 + 8e - +6H₂O=CH₄+8OH - In the intermediate zone, heavy metal ions (X) in the wastewater n+ OH generated by the reaction with the cathode - A chemical reaction occurs, producing a precipitate; intermediate zone reaction formula: X n+ +nOH - =X(OH) n ↓; Step 5: Transfer the effluent from the intermediate zone to a centrifuge, and separate the solid product X(OH). n The liquid is further dried in a vacuum filter, and the remaining liquid is reclaimed water that can be discharged.

[0011] The method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater is characterized in that: in step one, the pH range of the cathode electrolyte is 4.8~6.8, and the pH range of the anolyte is 9.5~11.5; in step four, the applied cathode catalytic potential ranges from -0.82V to -1.02V, the anolyte catalytic potential ranges from 0.82V to 1.02V, and the reaction temperature ranges from 25℃ to 65℃.

[0012] The beneficial effects of this invention are: (1) Achieving multi-objective synergistic treatment. This invention, through a three-chamber integrated design, simultaneously completes the treatment of carbon dioxide and heavy metal wastewater, and the storage of methane and oxygen, achieving "waste treatment with waste"; (2) Enhancing the utilization value of carbon dioxide, reducing wastewater treatment costs, and eliminating secondary pollution. This invention converts carbon dioxide into methane and achieves the storage of oxygen and methane through an electrochemical reaction; existing heavy metal wastewater treatment methods, such as chemical precipitation, have the disadvantages of high cost and easy secondary pollution; (3) The device has strong stability and corrosion resistance, and is suitable for complex working conditions. The shell of the three chambers is made of polytetrafluoroethylene (PTFE), which has the characteristics of resistance to strong acids and alkalis and corrosion of heavy metal ions, high temperature resistance, excellent sealing and gas barrier properties, ensuring long-term stable operation of the device; (4) Low energy cost. Powered by photovoltaic panels (renewable light energy), it does not require the consumption of traditional fossil energy, and is suitable for low-cost energy supply in scenarios such as communities. Attached Figure Description

[0013] Figure 1 is a schematic diagram of a three-chamber device for photovoltaic-driven carbon dioxide to methane production and simultaneous purification of heavy metal wastewater provided by the present invention; the markings in Figure 1 have the following meanings: carbon dioxide gas tank (1); methane storage tank (2); heavy metal wastewater inlet tank (3); cathode area (4); cathode electrode (5); anion exchange membrane I (6); intermediate area (7); oxygen storage tank (8); anode electrode (9); anode area (10); centrifuge (11); battery (12); photovoltaic panel (13); vacuum filter (14); heavy metal precipitation collection tank (15); reclaimed water storage tank (16); anion exchange membrane II (17). Detailed Implementation

[0014] To better explain the present invention, a detailed description will be provided below with reference to the accompanying drawings and embodiments. Obviously, the drawings described below are merely embodiments of the present invention. Those skilled in the art can obtain other drawings and other implementation methods based on these drawings without any creative effort.

[0015] In this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connected" should be interpreted broadly: it can refer to both pipe-like and circuit-like connections; it can be a direct connection or an indirect connection through an intermediate medium; it encompasses both external connections between components and the assembly connections between chambers and internal components such as membranes and electrodes. For those skilled in the art, the specific meaning of the above terms in this invention can be understood based on specific functional scenarios such as gas transport, liquid flow, electrical energy conduction, and solid-liquid separation. Example 1

[0016] A three-chamber device for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater is characterized by comprising a cathode region (4), an intermediate region (7), and an anode region (10) connected in sequence; the cathode region (4) and the intermediate region (7) are separated by anion exchange membrane I (6), and the intermediate region (7) and the anode region (10) are separated by anion exchange membrane II (17); a cathode electrode (5) is disposed in the cathode region (4); an anode electrode (9) is disposed in the anode region (10); the bottom of the cathode region (4) is connected to a carbon dioxide gas tank (1) via a pipeline; the cathode region (4) is connected to a methane storage tank (2) via a pipeline; The anode zone (10) is connected to the oxygen storage tank (8) via a pipe; the top of the intermediate zone (7) is connected to the heavy metal wastewater inlet tank (3) via a pipe; the bottom of the intermediate zone (7) is connected to the centrifuge (11), the bottom of the centrifuge (11) is connected to the vacuum filter (14), the vacuum filter (14) is connected to the heavy metal precipitation collection tank (15), the top of the centrifuge (11) and the vacuum filter (14) are respectively connected to the reclaimed water storage tank (16); the photovoltaic panel (13) is connected to the battery (12), and the positive and negative terminals of the battery (12) are respectively connected to the anode electrode (9) and the cathode electrode (5).

[0017] The cathode electrode (5) is a polymer-modified copper-based catalytic electrode with an electrode area of ​​12 cm². 2 The anode electrode (9) is a platinum (Pt) electrode; both the anion exchange membrane I (6) and the anion exchange membrane II (17) are quaternary ammonium anion exchange membranes, which can achieve OH- catalytic CO2 reduction to achieve highly selective preparation of CH4; the anion electrode (9) is a platinum (Pt) electrode; the anion exchange membrane I (6) and the anion exchange membrane II (17) are quaternary ammonium anion exchange membranes, which can achieve OH- catalytic reduction of CH4 to achieve high selective preparation ... - The directional movement from the cathode region (4) to the intermediate region (7), and then from the intermediate region (7) to the anode region (10), thereby achieving the precipitation of heavy metal ions and replenishment of OH groups at the anode. - The purpose is to prevent heavy metal ions from entering the cathode region (4) and the anode region (10); the shell of the three chambers consisting of the cathode region (4), the intermediate region (7) and the anode region (10) is made of polytetrafluoroethylene (PTFE), which has excellent resistance to strong acids and alkalis and resistance to heavy metal ion corrosion.

[0018] The carbon dioxide tank (1) has a capacity of 4L; the methane storage tank (2) has a capacity of 4L and is used to collect and store the CH4 generated by the reaction; the oxygen storage tank (8) has a capacity of 8L and is used to collect and store the O2 generated by the reaction; the centrifuge (11) and the vacuum filter (14) connected to the bottom of the intermediate zone 7 are used to efficiently separate the solid-liquid mixture generated in the intermediate zone (7); the photovoltaic panel (13) has a power of 72W; and the battery (12) is a 12V, 12Ah (0.5C) lead-acid battery to provide stable power for the electrochemical reaction of the entire device.

[0019] The electrolyte in the cathode region (4) is 12.5 L of 0.1 M NaHCO3 solution (CO2 saturated) with a pH of approximately 6.8; the electrolyte in the anode region (10) is 12.5 L of a mixed solution of 0.15 M KOH and 0.3 M NaHCO3 with a pH of approximately 10.0; the electrolyte in the intermediate region (7) is 10 L of a solution containing Mn 2+ The wastewater concentration was 100 mg / L (0.00182 mol / L).

[0020] A method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater includes the following steps: Step 1: 12.5 L of 0.1 M NaHCO3 solution (CO2 saturated) is introduced into the cathode region, and 12.5 L of a mixed solution of 0.15 M KOH and 0.3 M NaHCO3 is introduced into the anode region; Step 2: A CO2 gas source is introduced into the cathode region of the device at a flow rate of 12 mL / min, a temperature of 25 °C, and a pressure of 0.1 MPa, while simultaneously introducing Mn-containing gas into the intermediate region. 2+ The heavy metal wastewater had a concentration of 100 mg / L (0.00182 mol / L).

[0021] Step 3: The photovoltaic panels provide power to the device, and the positive and negative terminals of the battery are connected to the anode and cathode electrodes, respectively. Step 4: An oxidation reaction occurs at the anode to generate O2, which is then transported to an oxygen storage tank via pipeline. At the cathode, CO2 is reduced to generate CH4 and OH. - CH4 is collected in methane storage tanks; in the intermediate zone, Mn in the wastewater... 2+ OH generated by the reaction with the cathode - A chemical reaction occurs to produce a precipitate; Step 5: The effluent from the intermediate zone is transported to a centrifuge, and the separated solid product Mn(OH)2 is further dried in a vacuum filter. The remaining liquid is reclaimed water that can be discharged.

[0022] In step one, the pH of the cathode electrolyte is approximately 6.8, and the pH of the anolyte is approximately 10.0. In step four, the applied cathode potential is -0.82V (referencing a silver / silver chloride reference electrode), the anolyte potential is 0.82V (referencing a silver / silver chloride reference electrode), and the cathode current density is 488 mA / cm². 2 The reaction temperature is 25℃.

[0023] Measurements showed that under the above experimental conditions (reaction temperature 25℃, cathode electrolyte 0.1M NaHCO3 (CO2 saturated), CO2 pressure 0.1MPa), when 4L of CO2 was introduced (0.163mol at 25℃ and 0.1MPa), the final CH4 yield was 0.123mol, or 3.01L; 0.006mol of carbon was converted into the byproduct CO; and 0.0013mol of CO2 was converted into HCO3. - If not reduced in time by the catalyst, it reacts with the OH generated at the cathode. - The reaction produces stable CO3 2- It cannot be further converted into gaseous products, therefore the selectivity of methane is 94.4%.

[0024] The amount of CO2 that did not participate in the reaction was 0.0327 mol, therefore the CO2 conversion rate was 80%. The specific loss pathways are as follows: escape of undissolved gas (8%~9%), which did not come into contact with the catalyst; trace migration of CO2 entrained in the electrolyte (5%~6%), where a small amount of CO2 dissolved in the electrolyte is carried to the middle zone by the slight flow of the liquid and is adsorbed by Mn(OH)2 precipitate or discharged with the regenerated water; and trace residues of CO2 remaining after the electrolyte has been left to stand (5%~6%), where some dissolved CO2 is adsorbed on the inner wall of the electrolytic cell or forms tiny bubbles when the liquid is still, without participating in the reaction or being entrained.

[0025] The O2 production was 0.245 mol, or 6.00 L.

[0026] 10L of heavy metal wastewater contains 1g Mn 2+ That is, 0.0182 mol Mn 2+ Under the above experimental conditions, the final yield of Mn(OH)2 was 0.0180 mol, or 1.62 g, and the capacity of the reclaimed water was 10 L. 2+ The removal rate was 98.9%.

[0027] The above data shows that, within the set parameter range, the CO2 conversion rate of this device is 80.0%, and the Mn... 2+ The removal rate was 98.9%, and the selectivity for methane was 94.4%. The device can stably achieve the synergistic goals of CO2 resource recovery, heavy metal wastewater purification, and CH4 and O2 energy storage, verifying its practicality and stability.

[0028] Based on the above electrolysis method steps and analysis, it can be seen that some of the OH- generated by the cathode reaction... - Mn 2+ To ensure charge conservation and normal operation of the device, KOH solution needs to be replenished to the anode area in a timely manner.

[0029] The methane collected by the device can be stored in methane cylinders and used as clean fuel or chemical raw material; oxygen can be stored in high-pressure oxygen cylinders and used for industrial production, medical emergency care, or to generate electricity with methane (methane-oxygen fuel cell); manganese hydroxide can be converted into MnO2 through calcination and used for wastewater treatment or battery materials, realizing resource recycling; reclaimed water can be reused for industrial flushing, municipal greening, etc. after meeting the standards.

[0030] In summary, this invention, through a three-chamber integrated design, achieves synergistic linkage between CO2 resource recovery (conversion to CH4 storage) and the purification of wastewater containing heavy metal ions. Driven by renewable photovoltaic power, it reduces wastewater treatment and CO2 emission reduction costs, eliminates secondary pollution, and boasts strong device stability and wide applicability. This invention can be widely applied to industries discharging heavy metal wastewater, such as electroplating, metallurgy, and chemicals, as well as industrial CO2 emission reduction scenarios, providing a high-value technological path for the coordinated development of environmental protection and energy storage, with significant economic, environmental, and social benefits.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A three-chamber device for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater, characterized in that: The system comprises a cathode region (4), an intermediate region (7), and an anode region (10) connected in sequence. The cathode region (4) and the intermediate region (7) are separated by anion exchange membrane I (6), and the intermediate region (7) and the anode region (10) are separated by anion exchange membrane II (17). A cathode electrode (5) is disposed in the cathode region (4). An anode electrode (9) is disposed in the anode region (10). The bottom of the cathode region (4) is connected to a carbon dioxide gas tank (1) through a pipe. The cathode region (4) is connected to a methane storage tank (2) through a pipe. The anode region (10) is connected to an oxygen storage tank (8). The middle zone (7) is connected to the heavy metal wastewater inlet tank (3) via a pipe; the bottom of the middle zone (7) is connected to the centrifuge (11), the bottom of the centrifuge (11) is connected to the vacuum filter (14), the vacuum filter (14) is connected to the heavy metal precipitation collection tank (15), the top of the centrifuge (11) and the vacuum filter (14) are respectively connected to the reclaimed water storage tank (16); the photovoltaic panel (13) is connected to the battery (12), and the positive and negative terminals of the battery (12) are respectively connected to the anode electrode (9) and the cathode electrode (5).

2. The three-chamber device for photovoltaic-driven carbon dioxide to methane production and simultaneous purification of heavy metal wastewater according to claim 1, characterized in that: The cathode electrode (5) is a polymer-modified copper-based catalytic electrode; the anode electrode (9) is a platinum (Pt) electrode; the shell of the three chambers formed by the cathode region (4), the intermediate region (7), and the anode region (10) is made of polytetrafluoroethylene (PTFE).

3. A three-chamber device for photovoltaic-driven carbon dioxide to methane production and simultaneous purification of heavy metal wastewater according to claim 1 or 2, characterized in that: The electrolyte in the cathode region (4) is NaHCO3 with a concentration between 0.05M and 2M; the electrolyte in the anode region (10) is a mixture of KOH and NaHCO3 with a concentration between 0.05M and 2M; the liquid in the heavy metal wastewater inlet tank (3) contains heavy metal ions (X). n+ X n+ For Cd 2+ Ni 2+ Mn 2+ It exists in solution in ionic form and can react with OH-. - Wastewater that produces heavy metal ions that form insoluble hydroxide precipitates.

4. A method for photovoltaic-driven carbon dioxide to methane production while simultaneously purifying heavy metal wastewater, characterized in that: The process includes the following steps: Step 1: Fill the cathode region with NaHCO3 electrolyte and the anode region with KOH and NaHCO3 electrolyte; Step 2: Introduce a CO2 gas source into the cathode region of the device, and simultaneously introduce a heavy metal ion (X)-containing gas into the intermediate region. n+ Wastewater; Step 3: Photovoltaic panels provide power to the device, and the positive and negative terminals of the battery are connected to the anode and cathode electrodes, respectively; Step 4: An oxidation reaction occurs at the anode to generate O2, which is then transported to the oxygen storage tank through a pipeline; Anode reaction formula: 4OH - -4e - =O2↑ + 2H2O; At the cathode, CO2 is reduced to produce CH4 and OH. - CH4 is collected in the methane storage tank; cathode reaction: CO2 + 8e - +6H₂O=CH₄+8OH - In the intermediate zone, heavy metal ions (X) in the wastewater n+ OH generated by the reaction with the cathode - A chemical reaction occurs, producing a precipitate; intermediate zone reaction formula: X n+ +nOH - =X(OH) n ↓; Step 5: Transfer the effluent from the intermediate zone to a centrifuge, and separate the solid product X(OH). n The liquid is further dried in a vacuum filter, and the remaining liquid is reclaimed water that can be discharged.

5. The method for photovoltaic-driven carbon dioxide to methane production and simultaneous purification of heavy metal wastewater according to claim 4, characterized in that: In step one, the pH range of the cathode electrolyte is 4.8 to 6.8, and the pH range of the anolyte is 9.5 to 11.

5. In step four, the applied cathode catalytic potential ranges from -0.82V to -1.02V, the anode catalytic potential ranges from 0.82V to 1.02V, and the reaction temperature ranges from 25℃ to 65℃.

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