Ammonium ion-containing acidic carbon dioxide reduction system and application thereof

Abstract

The invention discloses an ammonium ion-containing acidic carbon dioxide reduction system and application thereof, and belongs to the technical field of electrocatalytic carbon dioxide reduction. The system provided by the invention comprises a CO2 reaction zone, an anode supply zone, a cathode absorption zone and a pump, the system adopts an acidic ammonium-containing solution, inhibits a hydrogen evolution reaction and stabilizes a CO2 intermediate through a cation effect of NH4 < + >, and constructs an NH4 < + > / NH3 circulation mechanism at the same time, NH4HCO3 precipitate generated by a cathode is decomposed into NH3, CO2 and H2O through low-temperature heating, NH3 is captured and regenerated into NH4 < + > and is conveyed back to an anode to form a closed cycle, and the closed cycle is completed. The salting-out problem is effectively eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic carbon dioxide reduction, and particularly relates to an acidic carbon dioxide reduction system based on ammonium ions and its application. Background Art

[0002] Electrocatalytic CO2 reduction (CO2R) is a promising technology for converting CO2 into valuable chemical products using renewable energy. Currently, both alkaline and acidic electrolyzers have been widely studied for CO2 conversion. Among them, acidic electrolyzers have unique advantages, which can prevent CO2 carbonation and eliminate the problem of CO2 transmembrane shuttle, thereby achieving higher CO2 conversion rate and avoiding the purification cost caused by the mixing of CO2 and O2.

[0003] Industrial implementation of CO2R requires an electrolyzer that can provide high energy efficiency and scalability. Among various configurations, the membrane electrode assembly (MEA) represents the most promising commercialization approach. By eliminating the liquid cathode solution and enabling zero-gap operation, the MEA significantly reduces ohmic losses and system complexity, providing a practical route for industrial-scale production. Although both proton exchange membranes and anion exchange membranes can be used in the MEA system, proton exchange membranes offer unique advantages in acidic environments, which can prevent CO2 carbonation and transmembrane shuttle.

[0004] However, the primary challenge of CO2R in acidic MEAs is the selectivity issue. Although the acidic environment can prevent CO2 carbonation and transmembrane shuttle, the acidic environment also promotes the competing reaction HER, resulting in poor selectivity of CO2R. On the basis of solving the selectivity challenge, low cell voltage and long-term stability are also key indicators for industrialization. Summary of the Invention

[0005] Aiming at the above-mentioned prior art, the present invention provides an acidic carbon dioxide reduction system based on ammonium ions and its application, which solves the problems of low selectivity and poor stability of the existing acidic carbon dioxide reduction.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide an acidic carbon dioxide reduction system based on ammonium ion-containing, including a CO2 reaction zone, an anode supply zone, a cathode absorption zone and a pump; the CO2 reaction zone includes a cathode and an anode arranged oppositely, the cathode includes a cathode plate, a CO2 inlet and a product outlet are arranged outside the cathode plate, a cathode catalyst layer is arranged inside the cathode plate, and the catalyst in the cathode catalyst layer is a catalyst for catalyzing the carbon dioxide reduction reaction; the anode includes an anode plate, a reaction liquid inlet and a reflux outlet are arranged outside the anode plate, an anode catalyst layer is arranged inside the anode plate, and the catalyst in the anode catalyst layer is a catalyst for catalyzing water oxidation; the cathode and the anode are connected by a power supply, and a cation exchange membrane A is arranged between them; the anode supply zone and the cathode absorption zone are separated by a cation exchange membrane B, and a mixed solution of organic ammonium and sulfuric acid is filled in both the anode supply zone and the cathode absorption zone; the outlet of the anode supply zone is connected to the reaction liquid inlet of the anode plate through a pump, and the inlet of the anode supply zone is connected to the reflux outlet of the anode plate through a pipeline; the CO2 inlet of the cathode plate is externally connected to a CO2 supply device, and the product outlet of the cathode plate is connected to the cathode absorption zone through a pipeline.

[0007] The beneficial effect of the present invention is: the acidic carbon dioxide reduction system based on ammonium ion-containing provided by the present invention utilizes the synergistic effect of high selectivity and low voltage, so that the organic ammonium in the anode supply zone and NH4 + migrate to the cathode surface under the action of an electric field, stabilize the CO2 intermediate through the dipole-electric field effect, and at the same time reduce the local H + concentration, effectively inhibiting the HER competitive reaction, improving the selectivity of carbon dioxide reduction to 60-92%, realizing high-selectivity, low-voltage, and long-life acidic carbon dioxide reduction, and the NH3 gas is regenerated into NH4 + after being recovered by the cathode absorption zone, forming a closed circulation system, reducing raw material consumption, reducing operating costs, and having significant industrial application potential.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows.

[0009] Further, the concentration of ammonium cation-containing in the acidic ammonium-containing solution filled in the anode supply zone and the cathode absorption zone is 0.1M, and the concentration of sulfuric acid is 0.1-0.3M.

[0010] Further, the ammonium cation is ammonium ion, ethylammonium ion or dimethylammonium ion.

[0011] The beneficial effect of adopting the further technical solution is: adopting ammonium ion effectively solves the salting-out problem faced by the alkali metal ion strategy, and realizes the acidic carbon dioxide reduction effect of high selectivity, low voltage and high stability.

[0012] Further, the catalyst for catalyzing the carbon dioxide reduction reaction is CoPc@CNT、 Au, Ag or Cu.

[0013] Furthermore, the catalyst for catalyzing water oxidation is Ir or IrO2.

[0014] Furthermore, the cation exchange membranes A and B are Nafion series membranes.

[0015] The present invention also provides an application of an ammonium ion-containing acidic carbon dioxide reduction system in acidic carbon dioxide reduction.

[0016] The beneficial effects of the present invention are as follows: The ammonium ion-containing acidic carbon dioxide reduction system provided by the present invention can achieve high selectivity, low voltage, and high stability in acidic carbon dioxide reduction under low temperature conditions. Compared with the traditional alkali metal ion strategy, it avoids the salting-out problem of alkali metal ions. Moreover, the NH3 gas generated by this system is recycled as ammonium ions after being recovered in the cathode absorption area, forming a closed-loop system, reducing raw material consumption, and lowering operating costs, showing great potential in the application of acidic carbon dioxide reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of an ammonium ion-containing acidic carbon dioxide reduction system;

[0018] Figure 2 Proton donation effect diagram;

[0019] Figure 3 Cation effect diagram;

[0020] Figure 4 SEM-EDS diagrams of the samples after stability tests for experimental group 1 and the control group;

[0021] Among them, 1. CO2 reaction area, 2. Anode supply area, 3. Cathode absorption area, 4. Pump, 5. Cathode plate, 6. Cathode catalyst layer, 7. Cation exchange membrane A, 8. Anode catalyst layer, 9. Anode plate, 10. Cation exchange membrane B. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following describes in detail the specific embodiments of the present invention in conjunction with the examples.

[0023] Examples

[0024] In the examples of the present invention, as Figure 1As shown in the figure, the present invention provides an acidic carbon dioxide reduction system based on ammonium ion-containing, including a CO2 reaction zone 1, an anode supply zone 2, a cathode absorption zone 3, and a pump 4; the CO2 reaction zone 1 includes a cathode and an anode arranged opposite to each other. The cathode includes a cathode plate 5. A CO2 inlet and a product outlet are arranged on the outer side of the cathode plate 5, and a cathode catalyst layer 6 is arranged on the inner side. The catalyst in the cathode catalyst layer 6 is a catalyst for catalyzing the CO2 reduction reaction; the anode includes an anode plate 9. A reaction liquid inlet and a reflux outlet are arranged on the outer side of the anode plate, and an anode catalyst layer 8 is arranged on the inner side. The catalyst in the anode catalyst layer 8 is a catalyst for catalyzing water oxidation; the cathode and the anode are connected by a power source, and a cation exchange membrane A 7 is arranged between them; the anode supply zone 2 and the cathode absorption zone 3 are separated by a cation exchange membrane B 10, and acidic ammonium-containing solutions are filled in both the anode supply zone 2 and the cathode absorption zone 3; the outlet of the anode supply zone 2 is connected to the reaction liquid inlet of the anode plate 9 through the pump 4, and the inlet of the anode supply zone 2 is connected to the reflux outlet of the anode plate 9 through a pipeline; the CO2 inlet of the cathode plate 5 is externally connected to a CO2 supply device, and the product outlet of the cathode plate 5 is connected to the cathode absorption zone 3 through a pipeline.

[0025] The operation process of the acidic carbon dioxide reduction system based on ammonium ion-containing is as follows: After the acidic carbon dioxide reduction system based on ammonium ion-containing is assembled, the CO2 reaction zone 1 is placed in a water bath for temperature control, and then the power source is started to energize the CO2 reaction zone 1. Then the pump 4 is operated. Under the push of the pump 4, the ammonium ion-containing in the anode supply zone 2 enters the anode region of the CO2 reaction zone 1 and migrates to the vicinity of the cathode catalyst layer 6 under the action of the electric field, promoting the highly selective reduction of CO2. During the reduction process, the ammonium ion releases a proton to generate NH3, and the generated NH3 reacts with CO2 to form an NH4HCO3 precipitate, which decomposes into NH3, CO2, and H2O under heating conditions. The principle is as Figure 2 , where the generated NH3 gas is captured in the cathode absorption zone 3 and reacts with H3O + to regenerate ammonium ion. The principle is as Figure 3 ; the regenerated ammonium ion returns to the anode supply zone 2 through diffusion through the cation exchange membrane, forming a closed NH4 + / NH3 circulation system, thereby continuously and stably providing ammonium ion for the cathode reaction.

[0026] Experimental Example

[0027] Performance test: Assemble the acidic carbon dioxide reduction system based on ammonium ion-containing in the manner of the embodiment, divided into 5 experimental groups and 1 control group. The acidic ammonium-containing solution components in the anode supply zone and the cathode absorption zone of experimental group 1 are 0.1M ammonium sulfate (the ammonium cation is ammonium ion) and 0.2M sulfuric acid, and the operating current density is 100 mA / cm 2, the temperature of the CO2 reaction zone is 60 °C. The catalyst used in the cathode catalyst layer is CoPc@CNT, and the catalyst used in the anode catalyst layer is Ir. The cation exchange membranes A and B use Nafion 117 membranes. In experimental group 2, the acidic ammonium-containing solution in the anode supply area and the cathode absorption area consists of 0.1 M ethyl ammonium sulfate (the ammonium cation is ethyl ammonium ion) and 0.2 M sulfuric acid, and the operating current density is 100 mA / cm 2 , the temperature of the CO2 reaction zone is 40 °C. The catalyst used in the cathode catalyst layer is Ag, and the catalyst used in the anode catalyst layer is IrO2. The cation exchange membranes A and B use Nafion 115 membranes. In experimental group 3, the acidic ammonium-containing solution in the anode supply area and the cathode absorption area consists of 0.1 M dimethyl ammonium sulfate (the ammonium cation is dimethyl ammonium ion) and 0.2 M sulfuric acid, and the operating current density is 100 mA / cm 2 , the temperature of the CO2 reaction zone is 100 °C. The catalyst used in the cathode catalyst layer is Cu, and the catalyst used in the anode catalyst layer is Ir. The cation exchange membranes A and B use Nafion 117 membranes. In experimental group 4, the acidic ammonium-containing solution in the anode supply area and the cathode absorption area consists of 0.1 M dimethyl ammonium sulfate (the ammonium cation is dimethyl ammonium ion) and 0.3 M sulfuric acid, and the operating current density is 150 mA / cm 2 , the temperature of the CO2 reaction zone is 60 °C. The catalyst used in the cathode catalyst layer is Au, and the catalyst used in the anode catalyst layer is IrO2. The cation exchange membranes A and B use Nafion 117 membranes. In experimental group 5, the acidic ammonium-containing solution in the anode supply area and the cathode absorption area consists of 0.1 M ammonium sulfate (the ammonium cation is ammonium ion) and 0.1 M sulfuric acid, and the operating current density is 50 mA / cm 2 , the temperature of the CO2 reaction zone is 60 °C. The catalyst used in the cathode catalyst layer is Au, and the catalyst used in the anode catalyst layer is Ir. The cation exchange membranes A and B use Nafion 115 membranes. In the control group, the solutions in the anode supply area and the cathode absorption area consist of 0.1 M potassium sulfate and 0.2 M sulfuric acid, and the operating current density is 100 mA / cm 2 , the temperature of the CO2 reaction zone is 60 °C. The catalyst used in the cathode catalyst layer is Au, and the catalyst used in the anode catalyst layer is Ir. The cation exchange membranes A and B use Nafion 117 membranes, and the results are shown in Table 1.

[0028] Table 1 Performance Statistics

[0029]

[0030] The experimental results show that too low temperature (40 °C) will affect the stability, and too high temperature (100 °C) will affect the selectivity. For different operating current densities, the components in the anode supply area need to be adjusted. Compared with the traditional alkali metal ion strategy, NH4 + can greatly improve the stability.

[0031] Experimental Example 2

[0032] SEM-EDS analysis: Samples after the stability test of Experimental Group 1 and the control group in Experimental Example 1 were subjected to SEM-EDS analysis, and the results are as Figure 4 , The K element signal is distributed throughout the gas diffusion electrode, including the gas diffusion layer, microporous layer, and catalyst layer. This result indicates that the traditional alkali metal ion strategy will cause serious salting-out problems. And the proton-giving cation NH4 introduced by adopting this strategy + After stable operation, the N signal therein only exists in the catalyst layer.

[0033] Although the specific implementation manners of the present invention have been described in detail in combination with the embodiments, it should not be construed as a limitation on the protection scope of this patent. Within the scope described in the claims, various modifications and deformations that can be made by those skilled in the art without creative efforts still fall within the protection scope of this patent.

Claims

1. An acidic carbon dioxide reduction system based on an ammonium ion-containing system, characterized in that, It includes a CO2 reaction zone (1), an anode supply zone (2), a cathode absorption zone (3) and a pump (4); the CO2 reaction zone (1) includes a cathode and an anode arranged oppositely, the cathode includes a cathode plate (5), a CO2 inlet and a product outlet are arranged on the outer side of the cathode plate (5), a cathode catalyst layer (6) is arranged on the inner side, and the catalyst in the cathode catalyst layer (6) is a catalyst for catalyzing the CO2 reduction reaction; the anode includes an anode plate (9), a reaction liquid inlet and a reflux outlet are arranged on the outer side of the anode plate (9), an anode catalyst layer (8) is arranged on the inner side, and the catalyst in the anode catalyst layer (8) is a catalyst for catalyzing the water oxidation; the cathode and the anode are connected by a power supply, and a cation exchange membrane A (7) is arranged between them; the anode supply zone (2) and the cathode absorption zone (3) are separated by a cation B (10), and acidic ammonium-containing solutions are filled in both the anode supply zone (2) and the cathode absorption zone (3); the outlet of the anode supply zone (2) is connected to the reaction liquid inlet of the anode plate (9) through the pump (4), and the inlet of the anode supply zone (2) is connected to the reflux outlet of the anode plate (9) through a pipeline; the CO2 inlet of the cathode plate (5) is externally connected to a CO2 supply device, and the product outlet of the cathode plate (5) is connected to the cathode absorption zone (3) through a pipeline.

2. The acidic carbon dioxide reduction system based on an ammonium ion according to claim 1, wherein: The concentration of ammonium cations in the acidic ammonium-containing solutions filled in the anode supply zone (2) and the cathode absorption zone (3) is 0.1 M, and the concentration of sulfuric acid is 0.1 - 0.3 M.

3. The acidic carbon dioxide reduction system based on an ammonium ion according to claim 2, wherein: The ammonium cation is ammonium ion, ethylammonium ion or dimethylammonium ion.

4. The acidic carbon dioxide reduction system based on an ammonium ion according to claim 1, wherein: The catalyst for catalyzing the CO2 reduction reaction is CoPc@CNT, Au, Ag or Cu.

5. The acidic carbon dioxide reduction system based on an ammonium ion according to claim 1, wherein: The catalyst for catalyzing the water oxidation is Ir or IrO2.

6. The acid carbon dioxide reduction system based on an ammonium ion according to claim 1, characterized in that: The cation exchange membrane A (7) and the cation exchange membrane B (10) are Nafion series membranes.

7. Application of the ammonium ion-based acidic carbon dioxide reduction system according to any one of claims 1 - 6 in acidic carbon dioxide reduction.

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