Crown ether substituted nickel phthalocyanine catalysts and complexes thereof, methods of preparation and use in electrocatalytic reduction of carbon dioxide

Abstract

The application discloses a crown ether substituted nickel phthalocyanine catalyst and a complex thereof, a preparation method and application in electrocatalytic reduction of carbon dioxide. The catalyst is synthesized from 4,5-dicyano benzene-18-crown-6 ether and nickel salt under specific conditions, and is formed into a hybrid catalyst by being loaded on the surface of carbon nanotubes. The application also discloses application of the catalyst in an acidic membrane electrode (MEA) electrolytic cell based on a bipolar membrane (BPM). The electrolytic cell can realize efficient electrocatalytic CO2 reduction reaction in a wide CO2 feeding concentration range (CO2 volume concentration 10-100%), the selectivity of product carbon monoxide is high, the CO selectivity can reach 77.77% when the CO2 volume concentration is as low as 10%, and no liquid by-product is generated. The application solves the problems of complex product at high potential, unknown performance under acidic conditions and poor adaptability to low-concentration CO2 in the prior art, and can be widely applied to low-concentration CO2 capture and conversion, energy storage systems and extreme environment carbon management scenes.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalysis technology, specifically to a molecular catalyst for the electrochemical reduction of carbon dioxide (CO2RR), and more particularly to a nickel phthalocyanine catalyst with a tetracrown ether substituent, its preparation method, an electrode containing the catalyst, and its efficient electroreduction application under low-concentration carbon dioxide conditions. Background Technology

[0002] With the increasing severity of global climate change, CO2 capture, utilization, and storage technologies have attracted widespread attention. Among them, CO2 electrocatalytic reduction technology can convert CO2 into valuable chemicals or fuels such as carbon monoxide, methanol, and ethylene, and has broad application prospects.

[0003] Currently, catalysts used for the electrocatalytic reduction of CO2 mainly include metals (such as Au and Ag), metal oxides, and molecular catalysts (such as metal phthalocyanines). Among them, molecular catalysts have attracted widespread attention due to their well-defined active center structure and tunable electronic properties. Existing research has shown that functionalizing the periphery of phthalocyanines, particularly by introducing crown ether groups with ion recognition capabilities, can significantly improve the catalyst's solubility, dispersibility, and stabilization of reaction intermediates, thereby enhancing its catalytic performance.

[0004] In existing technologies, a typical approach involves loading tetracrown ether-substituted cobalt phthalocyanine (CoPc-CE) onto multi-walled carbon nanotubes (CNTs), and then connecting the crown ether with K... + The host-guest interaction of ions enables the catalyst to be dispersed at the monomolecular level on the support. In a neutral KHCO3 electrolyte in an H-type electrolyzer, the catalyst achieves a CO Faradaic efficiency (FE) of >96% and a CO partial current density of 38 mA / cm² at a potential of -0.680 V vs. RHE.

[0005] However, this technology suffers from three major drawbacks that severely restrict its industrial application:

[0006] (1) Product selectivity limitation: When the catalyst with cobalt as the central metal is at a higher current density or a more negative potential, the side reactions such as hydrogen evolution reaction (HER) are aggravated, resulting in complex product distribution (such as H2, CH3OH, etc.), which increases the cost of subsequent separation and purification.

[0007] (2) Lack of adaptability to acidic environments: Existing studies have all been conducted in neutral H-type electrolyzers, and their performance has not been verified in acidic membrane electrode electrolyzers, which have greater industrial potential. Acidic MEA systems can fundamentally avoid the formation of carbonates / bicarbonates, thereby significantly improving the single-pass conversion efficiency of CO2, and represent the development direction of next-generation CO2 electrolysis technology.

[0008] (3) Poor adaptability to low CO2 concentrations: All performance data were obtained under saturated CO2 (~100%) conditions, and its catalytic activity and stability under low CO2 conditions, such as simulated real industrial flue gas (usually containing 10-20% CO2), were not investigated. Low CO2 concentrations can lead to severe mass transfer limitations and intense HER competition, resulting in a sharp decline in performance.

[0009] Therefore, developing a CO2 electroreduction catalyst that can overcome the above-mentioned defects, operate stably under acidic conditions, has high adaptability to low concentrations of CO2, and exhibits single product selectivity is of great practical significance and application value. Summary of the Invention

[0010] To address the aforementioned problems, this invention provides a novel crown ether-substituted nickel phthalocyanine catalyst, its preparation method, and its applications. This catalyst exhibits excellent electrocatalytic reduction performance over a wide concentration range, particularly low concentrations of CO2, in a bipolar membrane electrode (MEA) electrolyzer, demonstrating high selectivity in generating carbon monoxide. This invention aims to solve the following technical problems:

[0011] 1. To address the issues of complex products and high separation costs associated with cobalt phthalocyanine catalysts at high potentials, a method is proposed that uses nickel as the central metal and introduces a tetracrown ether substituent to achieve the selective generation of a single high-value product (carbon monoxide), thereby suppressing the generation of byproducts such as hydrogen and methanol.

[0012] 2. To address the limitations of existing technologies that can only be verified in neutral H-type electrolytic cells and lack performance data under acidic conditions, this invention constructs an acidic membrane electrode system suitable for bipolar membranes to verify the catalytic performance of the catalyst in an acidic environment.

[0013] 3. To address the issue that existing technologies can only be tested under saturated CO2 (100% concentration) and cannot adapt to low-concentration gas sources such as industrial flue gas, the local concentration and mass transfer efficiency of the catalyst under low partial pressure CO2 conditions are improved by utilizing the CO2-specific recognition and enrichment effect of crown ether molecules. The catalytic performance of the catalyst is also verified under low concentration CO2 (as low as 10%).

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] In a first aspect, the present invention proposes a method for preparing a crown ether-substituted nickel phthalocyanine catalyst complex, comprising the following process steps:

[0016] S1: Synthesis of crown ether-substituted nickel phthalocyanine molecule catalysts:

[0017] S11: Mix 4,5-dicyanobenzo-18-crown-6 ether with a nickel salt in an organic solvent;

[0018] S12: React at 130-160°C for 20-28 hours under an inert atmosphere;

[0019] S13: After the reaction is completed, the catalyst is separated and purified to obtain the crown ether substituted nickel phthalocyanine molecule catalyst;

[0020] S2: Anchoring of molecular catalysts:

[0021] S21: Dissolve the crown ether-substituted nickel phthalocyanine molecular catalyst obtained in step S1 with an alkali metal salt in a first solvent to form a catalyst precursor solution;

[0022] S22: The second solvent containing dispersed carbon nanotubes is mixed with the catalyst precursor solution and subjected to ultrasonic treatment to load the molecular catalyst onto the surface of the conductive support.

[0023] S23: Separate, wash and dry to obtain a tightly anchored molecular catalyst / carbon nanotube hybrid, which is the catalyst complex.

[0024] Furthermore, in step S1, the nickel salt is Ni(OAc)2·4H2O; and the organic solvent is N,N-dimethylethanolamine.

[0025] Furthermore, in step S1, the molar ratio of the 4,5-dicyanobenzo-18-crown-6 ether to the nickel salt is (3.5-4.5):1, preferably 4:1.

[0026] Furthermore, in step S2, the alkali metal salt is potassium hexafluorophosphate, and its amount is 10-20 times the molar amount of the molecular catalyst; both the first solvent and the second solvent are N,N-dimethylformamide.

[0027] Secondly, this invention proposes a crown ether-substituted nickel phthalocyanine molecular catalyst, prepared using the process described in step S1 above. The molecular catalyst has the following structure: four 18-crown-6 ether groups are attached to the outer periphery of the phthalocyanine ring, and the central metal is nickel. The general molecular formula is [NiPc-(C 12 H 24 The introduction of nickel centers in this catalyst, compared to common cobalt centers, exhibits a more singular and stable selectivity for CO products under the specific crown ether modification and acidic MEA environment of this invention.

[0028] Thirdly, this invention proposes a crown ether-substituted nickel phthalocyanine catalyst complex, prepared using the method described above. The complex comprises the crown ether-substituted nickel phthalocyanine molecular catalyst and carbon nanotubes as a conductive support. The host-guest complex formed by the complexation of the crown ether with alkali metal ions can introduce flexible cationic groups onto the molecule, thereby effectively balancing the relative strength of the interactions between molecules and between the molecule and the support. This allows the molecular catalyst to be rapidly loaded onto the surface of the carbon nanotubes in a non-aggregate form. The loading amount of the molecular catalyst is 30 to 70 nmol / mg support.

[0029] Fourthly, this invention proposes the application of the above-mentioned crown ether-substituted nickel phthalocyanine catalyst complex in the electroreduction of a low-concentration CO2 acidic membrane electrode electrolyzer. Using the catalyst complex as described above as the cathode catalyst, in a bipolar membrane electrode assembly (MEA) electrolyzer, a gas containing carbon dioxide is introduced into the cathode chamber. Under reverse bias conditions, the cathode selectively reduces carbon dioxide to carbon monoxide in an acidic environment.

[0030] Furthermore, in the above applications, the cathode inlet gas is a gas containing carbon dioxide, with a volume concentration of carbon dioxide of 10% to 100%, preferably 10% to 40%.

[0031] Furthermore, in the above applications, the electrocatalytic reduction is carried out under constant current conditions, with a current density of 10 to 100 mA / cm². 2 At a carbon dioxide volume concentration of 10% and a current density of 50 mA / cm², 2 Under certain conditions, the Faraday efficiency of carbon monoxide is no less than 77%.

[0032] Fifthly, the present invention also proposes a carbon dioxide electroreduction device, including a cathode, wherein the cathode uses the catalyst complex described above as a cathode catalyst.

[0033] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0034] (1) Excellent product selectivity: By replacing the central metal with Ni from Co and combining the unique spatial and electronic effects of crown ether substituents, the catalyst of the present invention exhibits high single selectivity for CO at high current density, effectively suppressing the generation of by-products such as hydrogen and methanol, simplifying the subsequent product separation process, and reducing costs.

[0035] (2) Excellent adaptability to acidic environments: This invention is the first to successfully apply this type of crown ether modified molecular catalyst to an acidic MEA system based on a bipolar membrane (BPM). Experiments have shown that the catalyst is structurally stable and has well-defined active sites in an acidic working environment, and can efficiently catalyze CO2 reduction, overcoming the shortcomings of traditional neutral systems that are prone to carbonate formation and have low carbon efficiency.

[0036] (3) Outstanding low-concentration CO2 conversion capability: Addressing the issue that existing technologies can only be tested under saturated CO2 (100% concentration) and cannot adapt to low-concentration gas sources such as industrial flue gas, the crown ether-substituted nickel phthalocyanine molecule catalyst constructed in this invention not only plays a dispersing and anchoring role, but its cavity structure also exhibits a certain weak interaction or local enrichment effect on CO2 molecules. This allows the catalyst of this invention to maintain a CO Faraday efficiency of over 77% even under CO2 volume concentrations as low as 10% (simulated industrial waste gas), demonstrating unprecedented adaptability to low-concentration CO2 and mass transfer optimization capabilities, providing a possibility for directly treating industrial waste gas without requiring a high-energy-consuming pre-concentration step. Attached Figure Description

[0037] Figure 1 The proton nuclear magnetic resonance spectrum of the crown ether-substituted nickel phthalocyanine molecule prepared in Example 1 of this invention ( 1 (H NMR) image.

[0038] Figure 2 The image shows a comparison of the Ni 2p orbital X-ray photoelectron spectroscopy (XPS) spectra of the catalyst composite (NiPc-CE / CNTs) prepared in Example 2 before and after loading.

[0039] Figure 3 In Example 3, the catalyst was subjected to constant current electrolysis (50 mA / cm²) in an acidic MEA electrolyzer under different CO₂ partial pressure inlet conditions. 2 The graph shows the change in the Faraday efficiency of the product CO when ).

[0040] Figure 4 This is a schematic diagram of the bipolar membrane electrode (MEA) electrolyzer structure used for the catalyst application of this invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Example 1: Synthesis of crown ether-substituted nickel phthalocyanine (NiPc-CE)

[0043] In an argon-protected glove box, weigh 1.2 mmol (4 equivalents) of 4,5-dicyanobenzo-18-crown-6 ether and 0.3 mmol (1 equivalent) of nickel acetate tetrahydrate (Ni(OAc)₂·4H₂O) and place them in a 50 mL pressure-resistant reaction tube. Add 5 mL of N,N-dimethylethanolamine as a solvent. Seal the reaction tube, remove it from the glove box, and place it in an oil bath preheated to 145°C. Stir the reaction continuously for 24 hours.

[0044] After the reaction was complete, the mixture was cooled to room temperature. The solid product was washed with methanol and filtered. The crude product obtained by filtration was purified by silica gel column chromatography (eluent: dichloromethane / methanol, volume ratio 5:1). The target fraction was collected, and the solvent was removed by rotary evaporation to obtain a dark green powdery solid product.

[0045] The yield was approximately 65%. The result was obtained by proton nuclear magnetic resonance spectroscopy (NMR). 1 The product was characterized by ¹H NMR, and the results are as follows: Figure 1 As shown. 1 ¹H NMR (400 MHz, CDCl₃) δ 7.85 (s, 8 H), 4.57 (s, 16 H), 4.28 (s, 16 H), 4.01 (s, 16 H), 3.88 (s, 16 H), 3.81 (s, 16 H). The spectra are consistent with the target molecule structure, confirming the successful synthesis of crown ether-substituted nickel phthalocyanine.

[0046] Example 2: Preparation of NiPc-CE / carbon nanotube (CNT) catalyst composite

[0047] Weigh 1.5 mg of the NiPc-CE molecular catalyst synthesized in Example 1 and 15 molar equivalents of potassium hexafluorophosphate (KPF6), dissolve them in 10 mL of N,N-dimethylformamide (DMF), and sonicate for 10 seconds to completely dissolve them to obtain a catalyst precursor solution.

[0048] 20 mg of multi-walled carbon nanotubes (CNTs, outer diameter 20-40 nm, length ~50 μm) were dispersed in 10 mL of DMF and sonicated for 2 hours to form a uniform black dispersion. The catalyst precursor solution was added dropwise to the CNTs dispersion, and the mixture was sonicated for 1 minute to complete the loading. The mixture was then centrifuged at 5000 rpm for 1 minute, and the supernatant was discarded. The precipitate was washed twice with DMF and then three times with deionized water to remove unloaded catalyst molecules and excess salt. Finally, the obtained solid was dried in a vacuum oven at 60°C for 12 hours to obtain a tightly anchored molecular catalyst / carbon nanotube hybrid, namely the NiPc-CE / CNTs catalyst composite.

[0049] The nickel (Ni) content in the composite was determined by ICP-MS, and the saturated loading of the molecular catalyst was calculated to be 51.6 nmol / mg CNTs. The catalyst before and after loading was characterized by X-ray photoelectron spectroscopy (XPS), such as... Figure 2 As shown, after loading, the binding energy positions of the Ni 2p orbitals are basically the same as those of the pure molecular catalyst before loading, indicating that the electronic structure and chemical environment of the Ni center of the molecular catalyst did not change significantly during the loading process, and the active center was well preserved.

[0050] Example 3: Electrocatalytic reduction performance of NiPc-CE / CNTs for low concentrations of CO2 in acidic MEA

[0051] 1. Fabrication of membrane electrode (MEA):

[0052] The acidic MEA electrolyzer based on BPMs used a CRRMEA4a-6 model purchased from the Scientific Materials Station. Its cathode plate was a Ti metal plate with a serpentine flow channel, and the flow channel area was 4 cm². 2 The anode plate is a platinum-plated Ti metal plate with a serpentine flow channel, and the flow channel area is 9 cm². 2 .

[0053] Working electrode: The cathode is a gas diffusion electrode (hydrophobic carbon paper electrode, electrode area: 2.5 cm × 2.5 cm) loaded with a certain mass concentration of molecular catalyst / carbon nanotube hybrid. Specifically, the NiPc-CE / CNTs catalyst composite prepared in Example 2 was mixed with Nafion ionomer (5 wt% solution) at a mass ratio of 10:1, and a DMF / ethylene glycol (volume ratio 4:1) mixed solvent was added. The mixture was then ultrasonically sonicated to form a uniform catalyst slurry. The slurry was then loaded onto hydrophobic carbon paper (CP-B240T 20wt% PTFE hydrophobic carbon paper) using a spray gun coating method. The catalyst layer loading was 0.5 mg / cm² (based on the total mass of the catalyst composite), and the active area was 6.25 cm².2 (2.5 cm × 2.5 cm).

[0054] Counter electrode: The anode is nickel foam (electrode area: 3.0 cm × 3.0 cm), used for high-efficiency OER;

[0055] Diaphragm: BPM (specification: Fumasep FBM-PK) is stored in 1 M NaCl aqueous solution and rinsed three times with deionized water before use.

[0056] according to Figure 4 The assembly shown is a membrane electrode electrolytic cell, with the cathode chamber and anode chamber pressed together by titanium plate flow field plates.

[0057] 2. Electrochemical testing and product detection:

[0058] All galvanostatic electrolysis studies based on a two-electrode system were conducted at 25°C, ambient pressure, and without iR compensation. Data acquisition was performed using a PARSTAT 4000A electrochemical workstation (Princeton Applied Research, USA). Humidified carbon dioxide flow to the cathode was 40 standard cubic centimeters per minute (SCCM), achieved through bubble jets. The anolyte was circulated between the anode and the reservoir via a peristaltic pump at a flow rate of 40 mL / min. -1 To rapidly remove O2 generated at the anode, the outlet of the electrolytic cell cathode (containing unreacted CO2 and products) is first introduced into a condenser to collect any possible liquid products, which are then directly passed into an online gas chromatograph for gas phase product detection. Liquid product detection: using 1H NMR spectroscopy (NMR). 1 ¹H NMR was used to analyze possible liquid phase products. The gas chromatograph was a Shimadzu GC2014CAFC / APC, with a 5 Å molecular sieve column, high-purity argon (Ar) as the carrier gas, and a thermal conductivity detector (TCD). The gas chromatograph was calibrated using a calibration gas mixture containing CO, CH₄, H₂, C₂H₄, C₂H₆, and CO₂.

[0059] The anolyte was a 1 M KOH solution, circulated by a peristaltic pump (flow rate 40 mL / min). A humidified gas mixture containing varying volume concentrations of CO2 (equilibrium gas was N2) was introduced into the cathode at a total flow rate of 40 sccm. Gas humidification was achieved using a bubbler flask (water temperature 25°C). Constant current electrolysis tests were performed using an electrochemical workstation (PARSTAT 4000A), and cell voltage changes were recorded.

[0060] 3. Test Results:

[0061] With a catalyst loading of 0.5 mg / cm³, the catalyst (crown ether substituted nickel phthalocyanine / carbon nanotube hybrid) was used. 2 At 50 mA / cm 2 At current densities of 50 mA / cm², when the CO₂ feed volume concentration was gradually reduced from 100%, 80%, 50%, 40%, to 20%, no liquid product methanol was generated, and the selectivity of CO remained above 80% and almost unchanged. Further reducing the CO₂ feed concentration to 10%, the selectivity of CO only decreased slightly, still reaching 77.77%, at 50 mA / cm². 2 The effect of CO2 feed partial pressure on product selectivity was investigated under a constant current density, and the results are summarized in [the table below]. Figure 3 .

[0062] Test results show that:

[0063] (1) Within a wide range of CO2 feed concentrations (100% to 10%), the catalyst of this invention maintains high selectivity for CO (FE). CO (>77%), a single product, and no liquid-phase byproducts. This demonstrates the effective activation ability of crown ether-substituted nickel phthalocyanine molecules for low concentrations of CO2.

[0064] (2) Even under the limiting conditions where the CO2 volume concentration is as low as 10%, the CO selectivity only decreases slightly and is still as high as 77.77%, which is much higher than the sharp performance degradation that usually occurs in existing technologies under similar low concentration conditions. This is attributed to the possible local enrichment effect of crown ether groups on CO2 molecules, which alleviates the mass transfer limitation.

[0065] In summary, the crown ether-substituted nickel phthalocyanine catalyst provided by this invention, through ingenious molecular design, achieves efficient and highly selective electroreduction of low-concentration CO2 to CO in a harsh acidic MEA environment, solving a key bottleneck in the prior art and showing great application potential in the field of integrated carbon capture and conversion of industrial waste gas.

[0066] The crown ether-substituted nickel phthalocyanine catalyst described in this invention has the ability to efficiently electrocatalyze the electroreduction of low-concentration CO2 in an acidic membrane electrode (MEA) system. It can be mainly applied to the direct capture and conversion of low-concentration carbon dioxide, and can efficiently treat low-partial-pressure CO2 gas streams such as petrochemical tail gas. It can achieve the integration of "carbon capture-electrosynthesis" at the source, effectively reducing the cost of deep carbon enrichment and storage and transportation. Potential fields include Power-to-X energy storage systems coupled with wind and solar power generation, carbon management in extreme environments such as deep-sea and Mars / Moon in-situ resource utilization.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. The application of a crown ether-substituted nickel phthalocyanine catalyst composite in the electroreduction of low-concentration CO2 acidic membrane electrode electrolyzer, characterized in that, Using the crown ether-substituted nickel phthalocyanine catalyst composite as the cathode catalyst, in a bipolar membrane electrode assembly electrolytic cell, a gas containing carbon dioxide is introduced into the cathode chamber. Under reverse bias conditions, the cathode selectively reduces carbon dioxide to carbon monoxide in an acidic environment. The preparation method of the crown ether-substituted nickel phthalocyanine catalyst complex includes the following process steps: S1: Synthesis of crown ether-substituted nickel phthalocyanine molecule catalysts: S11: Mix 4,5-dicyanobenzo-18-crown-6 ether with a nickel salt in an organic solvent; S12: React at 130-160°C for 20-28 hours under an inert atmosphere; S13: After the reaction is completed, the catalyst is separated and purified to obtain the crown ether substituted nickel phthalocyanine molecule catalyst; S2: Anchoring of molecular catalysts: S21: Dissolve the crown ether-substituted nickel phthalocyanine molecular catalyst obtained in step S1 with an alkali metal salt in a first solvent to form a catalyst precursor solution; S22: The second solvent containing dispersed carbon nanotubes is mixed with the catalyst precursor solution and subjected to ultrasonic treatment to load the molecular catalyst onto the surface of the conductive support. S23: Separate, wash and dry to obtain a tightly anchored molecular catalyst / carbon nanotube hybrid, which is the catalyst complex.

2. The application of the crown ether-substituted nickel phthalocyanine catalyst composite according to claim 1 in the electroreduction of a low-concentration CO2 acidic membrane electrode electrolyzer, characterized in that, In step S1, the nickel salt is Ni(OAc)2·4H2O; the organic solvent is N,N-dimethylethanolamine.

3. The application of the crown ether-substituted nickel phthalocyanine catalyst composite according to claim 1 in the electroreduction of a low-concentration CO2 acidic membrane electrode electrolyzer, characterized in that, In step S1, the molar ratio of the 4,5-dicyanobenzo-18-crown-6 ether to the nickel salt is (3.5-4.5):

1.

4. The application of the crown ether-substituted nickel phthalocyanine catalyst composite according to claim 1 in the electroreduction of a low-concentration CO2 acidic membrane electrode electrolyzer, characterized in that, In step S2, the alkali metal salt is potassium hexafluorophosphate, and its amount is 10-20 times the molar amount of the molecular catalyst; the first solvent and the second solvent are both N,N-dimethylformamide.

5. The application of the crown ether-substituted nickel phthalocyanine catalyst composite according to claim 1 in the electroreduction of a low-concentration CO2 acidic membrane electrode electrolyzer, characterized in that, The cathode inlet gas is a gas containing carbon dioxide, with a volume concentration of 10% to 40%.

6. The application of the crown ether-substituted nickel phthalocyanine catalyst composite according to claim 1 in the electroreduction of a low-concentration CO2 acidic membrane electrode electrolyzer, characterized in that, The electrolytic cell for the membrane electrode assembly uses a bipolar membrane. The electroreduction is carried out under constant current conditions, with a current density of 10 to 100 mA / cm². 2 At a carbon dioxide volume concentration of 10% and a current density of 50 mA / cm², 2 Under certain conditions, the Faraday efficiency of carbon monoxide is no less than 77%.

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