KR20190096265A - Stack for carbon dioxide conversion and method for carbon dioxide conversion using the same - Google Patents

Abstract

The present invention relates to a stack for converting carbon dioxide and a method for converting carbon dioxide using the same. More specifically, the present invention relates to a multi-stack for converting carbon dioxide of a large area which can be utilized as a carbon dioxide removal device and a carbon monoxide generating device, and the like, and a method for converting carbon dioxide using the same. According to one embodiment of the present invention, carbon dioxide can be converted for a long term economically and efficiently using the stack.

Description

Stack for carbon dioxide conversion and method for carbon dioxide conversion using the same}

The present invention relates to a stack for converting carbon dioxide and a method of converting carbon dioxide using the same. More specifically, the present invention relates to a multi-stack for converting carbon dioxide to a large area that can be utilized as a carbon dioxide removal device, a carbon monoxide generating device, and the like, and a carbon dioxide conversion method using the same.

The Kyoto Protocol sets targets for reducing the greenhouse gas emissions of six greenhouse gases. Efforts and research to reduce emissions of atmospheric carbon dioxide (CO ₂ ), one of the greenhouse gases, are being actively conducted worldwide. From 1990 to 2012, the largest sources of CO2 emissions in the United States were power plants (32%), transportation (28%) and industry (20%). Thus, attempts have been made to reduce and then capture carbon dioxide emitted from large sources such as power plants in order to maintain the concentration of carbon dioxide in the atmosphere.

These research areas can be broadly divided into two fields: carbon capture and storage (CCS) from carbon sources and carbon capture and utilization (CCU). )to be.

CCS technology is a technology that captures carbon dioxide from mass sources, packs it in an enclosed space, and then burys it and isolates it from the atmosphere. Carbon dioxide is mainly stored through carbonation of the inorganic catalyst, and the sealed container is stored in the deep sea layers and the basement of the ground surface, and it is difficult to commercialize because it has problems such as ecosystem damage.

CCU technology, on the other hand, is beneficial to industrialization, both environmentally and economically, in that it produces profits without the need for storage space. In particular, the electrochemical method can selectively produce various organic compounds such as formic acid, carbon monoxide, methanol, and oxalic acid according to the selection of electrode material, and can be operated at room temperature and atmospheric pressure, and thus, the cost of configuring the system is low. It is attracting attention in that it can be miniaturized according to the design or large capacity through stacking and can be applied to various industries.

Conventional techniques in this regard include US Pat. No. 7,790,012 (2010), which discloses electrochemical carbon dioxide conversion (ECC).

However, there is a lack of research on the large-area research of a catalytic electrode of 100 cm 2 or more and the stacking of electrochemical cells having excellent CO conversion efficiency to minimize the reduction rate of CO production.

It is an object of the present invention to provide a large area carbon dioxide conversion stack.

Another object of the present invention is to provide a multi-stack for carbon dioxide conversion comprising two or more cells.

Another object of the present invention is to provide a method for converting carbon dioxide efficiently for a long time using the stack.

Other objects and advantages of the present invention will become apparent from the following detailed description, claims and drawings.

The present inventors derive and optimize the electrode activity and durability influencing factors such as stack shape, structure, electrode type, electrolyte membrane type, potential, electrolyte flow rate, pH, and the like, thereby considering a large area of anode / cathode active area. The stack for the conversion was developed to complete the present invention.

According to an aspect of the present invention, a polymer electrolyte membrane and an anode electrode and a first fluid diffusion layer are sequentially stacked on one surface of the electrolyte membrane, and a cathode electrode and a second fluid diffusion layer are sequentially stacked on the other surface of the electrolyte membrane. A separator having a first fluid diffusion layer, an anode electrode, an electrolyte membrane, a cathode electrode, and a through hole for accommodating the second fluid diffusion layer, and having a plurality of microchannels, one side of which is open to the first fluid diffusion layer or the second fluid diffusion layer. Comprising a membrane electrode assembly comprising a, the cross section of the stack is circular or oval, there is provided a stack for carbon dioxide conversion.

According to an embodiment of the present invention, the electrolyte membrane may be a cation exchange membrane.

According to an embodiment of the present invention, the cathode electrode may be composed of silver or silver alloy.

According to one embodiment of the invention, at least one of the first fluid diffusion layer and the second fluid diffusion layer may be composed of a porous felt or foam.

According to an embodiment of the present invention, the membrane electrode assembly is connected to two or more via a current collector, the first inflow passage connected to the anode electrolyte is introduced into the first fluid diffusion layer of the anode electrode of the plurality of membrane electrode assembly, A first discharge passage through which the fluid flowing out of the first fluid diffusion layer of the anode electrode of the plurality of membrane electrode assemblies is discharged; And a second inflow passage connected such that the cathode electrolyte flows into the second fluid diffusion layer of the cathode electrode of the plurality of membrane electrode assemblies, and the second fluid flowing out of the second fluid diffusion layer of the cathode electrode of the plurality of membrane electrode assemblies is discharged. It may include an outlet flow path.

According to an embodiment of the present invention, the separator may further include a sealing member for sealing the first fluid diffusion layer or the second fluid diffusion layer.

According to one embodiment of the invention, the carbon dioxide conversion stack may further include a pressurizing means for increasing the carbon dioxide solubility in at least one of the anode electrolyte and the cathode electrolyte.

According to an embodiment of the present invention, the carbon dioxide conversion stack including two or more membrane electrode assemblies may have a CO reduction rate of 20% or less.

According to one embodiment of the present invention, the carbon dioxide conversion stack may be supplied with a constant voltage less than 3V / cell.

According to one embodiment of the present invention, the carbon dioxide conversion stack can maintain an electrolyte supply flow rate of 1.8 L / min or more.

According to an embodiment of the present invention, the carbon dioxide conversion stack may be directly connected to the solar cell.

According to another aspect of the present invention, there is provided a carbon monoxide generating apparatus comprising the stack for converting carbon dioxide.

According to another aspect of the present invention, there is provided a carbon dioxide removal device comprising the stack for converting carbon dioxide.

According to another aspect of the present invention, a carbon dioxide conversion method for converting carbon dioxide efficiently for a long time using the stack for carbon dioxide conversion is provided.

According to an embodiment of the present invention, in the carbon dioxide conversion method, a constant voltage may be supplied at less than 3V / cell.

According to one embodiment of the invention, the electrolyte supply flow rate in the carbon dioxide conversion method can be maintained at 1.8 L / min or more.

According to one embodiment of the present invention, it is possible to provide a stack for converting carbon dioxide having a large area of 100 cm 2 or more.

In addition, according to an embodiment of the present invention, it is possible to provide a multi-stack for converting carbon dioxide comprising two or more cells with a minimum reduction in CO production.

According to one embodiment of the present invention, it is possible to convert carbon dioxide to the long term economically and efficiently using the stack.

According to one embodiment of the present invention, it is possible to produce carbon monoxide economically and efficiently for a long time using the stack.

1 is a plan view schematically showing electrolyte circulation and carbon monoxide generation of a stack for converting carbon dioxide according to an embodiment of the present invention.
Figure 2a is an exploded perspective view of a stack for converting carbon dioxide according to an embodiment of the present invention.
2B is an exploded perspective view of a membrane electrode assembly (MEA) according to an embodiment of the present invention.
3A is a view showing an anode electrode surface of a membrane electrode assembly according to an embodiment of the present invention.
3B is a view showing the cathode electrode surface of the membrane electrode assembly according to an embodiment of the present invention.
4 shows a unit cell ((a) unit cell having an electrode area of 16 cm 2), one cell of carbon dioxide conversion stack ((b) a large area of 102 cm 2 stack-1), and two cells of carbon dioxide conversion multi-stack ( (c) It is a photograph compared and comparing stack-2) of large area of 102 cm <2>.
5 is a schematic diagram showing a carbon dioxide conversion reaction in a multi-stacked carbon dioxide conversion multi-stack in accordance with an embodiment of the present invention.
6A shows the results of a computational fluid dynamics simulation when the electrode space of the stack is empty and filled with a porous structure.
Figure 6b is a photograph showing the shape of the Ti felt (felt) applied to the stack.
FIG. 7A is a graph showing CO conversion efficiency when Ni cathode electrode is used and the polymer electrolyte membrane is a cation exchange membrane (PEM). FIG.
FIG. 7B is a graph showing CO conversion efficiency when Ag cathode electrode is used and the polymer electrolyte membrane is a cation exchange membrane (PEM).
8A is a graph illustrating LSV test results performed for performance evaluation of a stack for converting carbon dioxide according to an embodiment of the present invention.
8B is a graph showing a result of a constant voltage test performed for performance evaluation of a stack for converting carbon dioxide according to an embodiment of the present invention.
9A is a graph showing changes in current density and CO conversion efficiency with time at a constant voltage (2.6 V / cell) of Stack-1.
9B is a graph showing changes in current density and CO conversion efficiency with time at a constant voltage (5.2 V / cell) of Stack-2.
10 is a graph showing a change in current density according to a change in the electrolyte supply flow rate in the stack-2.

Objects, specific advantages, and novel features of the present disclosure will become more apparent from the following detailed description and embodiments associated with the accompanying drawings.

Prior to this, the terms or words used in this specification and claims are not to be interpreted in a conventional and dictionary sense, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present disclosure on the basis of the principle of the present invention.

In the present specification, when a component such as a layer, part, or substrate is described as being "on", "connected", or "coupled" to another component, it is directly on another component "on", " Connected, "or" coupled ", and may be interposed between one or more other components. In contrast, if a component is described as being "directly on", "directly connected", or "directly coupled" to another component, no other component may be interposed between the two components. .

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this specification, terms such as "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

In the present specification, when a part is said to "include" a certain component, it means that it may further include other components, without excluding the other components unless otherwise stated. In addition, throughout the specification, "on" means to be located above or below the target portion, and does not necessarily mean to be located above the gravity direction.

The present disclosure may be variously modified and have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present disclosure to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present disclosure. In the description of the present disclosure, when it is determined that the detailed description of the related known technology may obscure the gist of the present disclosure, the detailed description thereof will be omitted.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, and in the following description with reference to the accompanying drawings, the same or corresponding components will be given the same reference numerals, and redundant description thereof will be omitted. do.

1 is a plan view schematically showing electrolyte circulation and carbon monoxide generation of a stack for converting carbon dioxide according to an embodiment of the present invention. Figure 2a is an exploded perspective view of a stack for converting carbon dioxide according to an embodiment of the present invention. 2B is an exploded perspective view of a membrane electrode assembly (MEA) according to an embodiment of the present invention. 3A and 3B are views illustrating an anode electrode surface and a cathode electrode surface of a membrane electrode assembly according to an embodiment of the present invention, respectively.

1 and 2A, a stack for converting carbon dioxide according to an embodiment of the present invention includes a membrane electrode assembly (MEA, 10), first and second current collectors (20, 22). , Bipolar plates 21, first and second insulating plates 30 and 32, and first and second end plates 40 and 42. The components may be fastened with screws.

Although not limited thereto, the driving power source 50 of the stack may include a renewable energy source. The renewable energy source may include solar light, solar heat, wind power, and fuel cells. The renewable energy source may be directly connected to the stack to reduce coupling loss. The previously reported renewable energy (solar) linkage is a structure that generates power from a solar cell, stores it in a battery, and drives the device using the stored battery power. Such a structure is reported to have an energy loss rate of more than 40% due to the coupling loss (coupling loss), so it is effective to supply the stack power by reducing the energy loss due to the coupling loss in direct connection with the solar cell You can build a system.

2B, 3A, and 3B, the membrane electrode assembly 10 includes a polymer electrolyte membrane 12 and an anode electrode 13 and a first fluid diffusion layer on one surface of the electrolyte membrane 12. 14 are sequentially stacked, and the cathode electrode 15 and the second fluid diffusion layer 16 are sequentially stacked on the other surface of the electrolyte membrane 12, and the first fluid diffusion layer 14 and the anode electrode 13 are sequentially stacked. And a separator 11 including a body portion 11b having a frame shape including an electrolyte membrane 12, a cathode electrode 15, and a through portion 11a for receiving the second fluid diffusion layer 16. . The separator 11 includes a plurality of fine inflow passages 11c and 11e and discharge passages 11d and 11f, one side of which is open to the first fluid diffusion layer 14 or the second fluid diffusion layer 16.

As shown in Figures 1 to 3b, the large-area carbon dioxide conversion stack and the membrane electrode assembly 10 according to the present invention is advantageous in the form of laminar flow when the cross section is approximately circular or elliptical, It may be suitable for a uniform fluid flow if the electrode space of the stack is of porous structure rather than empty. The laminar flow formation and uniform fluid flow as described above can provide a large-area carbon dioxide conversion stack. Although not limited thereto, the carbon dioxide conversion stack of the present invention may have a large area of 100 cm 2 or more in cross section.

Figure 3a is a view showing the anode electrode surface of the membrane electrode assembly according to an embodiment of the present invention, Figure 3b is a view showing the cathode electrode surface of the membrane electrode assembly according to an embodiment of the present invention.

Referring to FIGS. 3A and 3B, one surface (eg, an anode electrode surface) of the body portion 11b of the separator 11 may include a first inflow passage 11c and a first discharge passage 11d in a predetermined region. And a second inflow passage 11e and a second discharge passage 11f in a predetermined region on the other surface (for example, the cathode electrode surface) of the body portion 11b of the separator 11.

1, 2B, and 3A, for example, an anode electrolyte of KHCO ₃ saturated with carbon dioxide introduced through the first inflow passage 11c is in contact with the surface of the anode electrode 13. After the reaction occurs, the oxygen may be discharged together while being discharged through the first discharge passage 11d, and the anode electrolyte is recycled.

1, 2B, and 3B, a cathode electrolyte of KHCO ₃ , in which carbon dioxide introduced through the second inflow passage 11e is dissolved, contacts with the surface of the cathode electrode 15 to react. After being discharged through the second discharge passage 11f, carbon monoxide and hydrogen can be discharged together, and the cathode electrolyte is recycled. The discharged carbon monoxide and hydrogen can be separated using a hydrogen separation membrane. Therefore, the stack for converting carbon dioxide according to the present invention can be used as a carbon monoxide generating device.

The electrolyte may be cyclically supplied to the stack for converting carbon dioxide. Specifically, by supplying and discharging the electrolyte to the carbon dioxide conversion stack at a constant flow rate, a predetermined amount of electrolyte may be filled and maintained in the reactor. The electrolyte solution may include a basic solution such as KOH aqueous solution, NaOH aqueous solution, LiOH aqueous solution, K ₂ CO ₃ aqueous solution or KHCO ₃ aqueous solution, but is not limited thereto.

3A and 3B, the first and second inflow passages 11c and 11e and the first and second discharge passages 11d and 11f are formed on both surfaces of the body portion 11b of the separator 11. O-ring-shaped gaskets (17 in FIGS. 2A and 2B) fitted into rectangular grooves 11g and 11h formed to be included inside are provided as a sealing member to prevent leakage of electrolyte and gas. . The O-ring portion 18 of FIG. 2 may prevent leakage of electrolyte and gas when moving from a multi-stack including two or more cells to the next cell.

Referring again to FIG. 2B, the electrolyte membrane 12 may be a cation exchange membrane (PEM) or anion exchange membrane (AEM). Although not limited thereto, the electrolyte membrane 12 may be a polymer electrolyte membrane, and the cation exchange membrane may be suitable because of its excellent carbon dioxide conversion rate. Although not limited thereto, the cation exchange membrane may be Nafion, which is a fluorine-based cation exchange membrane.

The anode electrode 13 is not limited thereto, but is selected from IrO ₂ , RuO ₂ , PtO ₂ , PdO, other non-noble metal transition metal-based single or binary or more oxides (Co ₃ O ₄ , NiO, CuCo oxide), and the like. Can be configured.

The first fluid diffusion layer 14 may be made of a carbon porous fiber material in order to uniformize the fluid flow when constructing a large area stack. Although not limited thereto, the first fluid diffusion layer 14 may be formed of carbon felt, Ni or Ti foam, or insulating mesh. Ti felt may be suitable because it has good neutral corrosion resistance and no hydrogen generating catalyst. When the first fluid diffusion layer 14 is made of Ni or Ti foam, the distance between the electrolyte membrane 12 and the anode electrode 13 can be controlled by controlling the thickness of the foam.

The cathode electrode 15 is not limited thereto, but may be composed of Ag, Cu, Pt, Co, and an alloy thereof, and may be appropriately composed of silver or silver alloy.

The second gas diffusion layer 16 may be made of a carbon porous fiber material. Although not limited thereto, the second gas diffusion layer 16 may be made of carbon felt, Ni or Ti foam, or insulating mesh, and carbon felt may be suitable. When the second gas diffusion layer 16 is made of Ni or Ti foam, the distance between the electrolyte membrane 12 and the cathode electrode 15 can be controlled by controlling the thickness of the foam.

4 is a unit cell ((a) unit cell having an electrode area of 16 cm 2), a single cell carbon dioxide conversion stack ((b) at a large area of 102 cm 2), and 2 according to an embodiment of the present invention. It is a photograph comparing the multi-stack for carbon dioxide conversion ((c) 102-2 cm <2> of stack 2) of a cell. 5 is a schematic diagram showing a carbon dioxide conversion reaction in a multi-stacked carbon dioxide conversion multi-stack in accordance with an embodiment of the present invention.

The multi-stack for converting carbon dioxide of the two cells shown in FIGS. 4 and 5 is a structure in which the membrane electrode assemblies 10 of the stack shown in FIG. 1 are connected through a current collector 122. Although FIG. 5 illustrates a multi-stack composed of two cells of the first cell 100 and the second cell 200, a multi-stack of three or more cells is also manufactured by connecting a plurality of cells in the same manner with a current collector interposed therebetween. can do.

Therefore, the multi-stack for carbon dioxide conversion according to the present invention is a structure that can be easily stacked by increasing the number of cells, it is possible to design that can easily adjust the number of cells to suit the purpose.

Referring to FIG. 5, when the carbon dioxide saturated electrolyte is supplied to the first inflow passage 111c of the separator 111 of the first cell 100 along the red arrow, the anode electrode 113 of the first cell 100 is supplied. An electrolyte solution in which carbon dioxide is saturated is supplied to the first fluid diffusion layer 114 of) and the first fluid diffusion layer 214 of the anode electrode 213 of the second cell 200. In this case, the first fluid diffusion layer 114 of the anode electrode 113 of the first cell 100 is sealed with a gasket, and the first inflow passage 111c is sealed with an O-ring. The electrolyte flows to the first fluid diffusion layer 214 of the anode electrode 213 of the two cells 200 to supply the saturated carbon dioxide electrolyte. Even if the cell is stretched in this manner, the carbon dioxide-saturated electrolyte supplied to the anode electrode is configured to be supplied only to the anode electrodes of the plurality of membrane electrode composites without leakage of the electrolyte solution and gas.

Referring to FIG. 5, when the carbon dioxide saturated electrolyte is supplied to the second inflow passage 211c of the separator 211 of the second cell 200 along the blue arrow, the cathode electrode 215 of the second cell 200 is supplied. An electrolyte solution in which carbon dioxide is saturated is supplied to the second fluid diffusion layer 216 of the second electrode diffusion layer 216 and the second fluid diffusion layer 116 of the cathode electrode 115 of the first cell 100. In this case, the second fluid diffusion layer 216 of the cathode electrode 215 of the second cell 200 is sealed with a gasket, and the second inflow passage 211c is sealed with an O-ring, so that electrolyte and gas are not leaked immediately. The electrolyte flows to the second fluid diffusion layer 116 of the cathode electrode 115 of the first cell 100 to supply carbon dioxide saturated electrolyte. Even if the cell is expanded in this manner, the carbon dioxide-saturated electrolyte supplied to the cathode electrode 115 is configured to be supplied only to the cathode electrodes of the plurality of membrane electrode composites without leakage of the electrolyte and gas.

Referring to FIG. 5, a chamber 300 may be further provided on at least one side of the outermost cathode electrode 215 and the outermost anode electrode 113 of the multi-stack. The chamber 300 may improve the reaction efficiency in the stack by increasing the CO ₂ solubility in the electrolyte as a means for applying a high pressure to the stack.

According to an embodiment of the present invention, the carbon dioxide conversion stack including two or more membrane electrode assemblies may have a CO reduction rate of 20% or less. In the case of a stack including two or more cells, the CO production reduction rate is high and thus may not be suitable as a carbon dioxide conversion device. On the other hand, in the case of the present invention, even if two or more cells are included, the CO reduction rate can be controlled to 20% or less, or 16% or less, thereby improving carbon dioxide conversion efficiency.

Although not limited thereto, the stack for converting carbon dioxide of the present invention may be suitable for a constant voltage of less than 3.0 V, or more than 2.0 V and less than 3.0 V to stabilize the current density and maintain the overall faradaic efficiency appropriately. have.

Although not limited thereto, the stack for converting carbon dioxide of the present invention may be suitable for maintaining an electrolyte supply flow rate of 1.8 L / min or more such that the current density is stabilized and the overall faradaic efficiency is appropriately maintained.

According to another aspect, the stack structure of the present invention may be used as a filter for generating various exhaust gases or SOx, NOx, or the like by supplying a combination of one or more of various input gases, catalysts, and electrolytes to the stack. For example, the present application has been described with reference to a stack structure in which carbon dioxide is dissolved and reacted in an electrolyte solution as a solution, but may be applied as a stack structure for supplying gaseous carbon dioxide without using an electrolyte solution.

Illustratively, Tables 2 to 4 list products according to various electrolytes, metals, and essentials that can be applied to the stack structure of the present invention.

According to another aspect, the carbon dioxide conversion stack of the present invention can be used as a device for removing carbon dioxide from a gas containing carbon dioxide.

Example

1. Optimization of stack structure

(1) the shape and porosity of the stack

Before fabricating the stack, simulations were performed using Computational fluid dynamics (CFD) programs to select a structure suitable for large area stacks. Figure 6a shows the results of computational fluid dynamics simulation when the electrode space of the stack is empty and filled with a porous structure such as felt.

It was confirmed that the shape of the cross section of the stack was advantageous for laminar flow formation when the shape was approximately circular or elliptical. In addition, it was confirmed that the porous structure such as foam or felt helps the flow of the uniform fluid rather than the electrode space of the stack.

Since Ni foam, which is easily oxidized in neutral and efficient for hydrogen generation, is not suitable as a fluid diffusion layer, Ti felt having excellent neutral corrosion resistance and no hydrogen generation catalyst is suitable.

Therefore, the overall electrode shape was circular, and the porous structure was selected as Ti felt (porosity 81%, fiber diameter 20 um). Figure 6b is a photograph showing the shape of the Ti felt applied to the stack.

(2) Cathode  Electrode and Polymer Electrolyte Membrane

0.5 M KHCO ₃ saturated with CO ₂ is supplied to the anode and cathode at a flow rate of 1.8 L / min using a metering pump as an anode and a catholyte, and 2.6 V / cell is applied to the current density. , Faradaic efficiency, CO conversion rate, etc. were evaluated.

FIG. 7A is a graph showing CO conversion efficiency when Ni cathode electrode is applied and the polymer electrolyte membrane is a cation exchange membrane (PEM), and FIG. 7B is a cathode electrode of Ag and the polymer electrolyte membrane is a cation exchange membrane ( proton exchange membrane (PEM), a graph showing CO conversion efficiency.

PEM (proton exchange membrane, cation exchange membrane) or AEM (anion exchange membrane, anion exchange membrane) can be applied to the polymer electrolyte membrane, but as shown in Figure 7a and 7b, when the PEM is selected as the polymer electrolyte membrane CO conversion efficiency This can be high.

In addition, as shown in FIGS. 7A and 7B, when the CO conversion efficiency of the cathode electrode of Ni and the cathode electrode of Ag was compared, it was analyzed that the CO conversion efficiency of the cathode electrode of Ag was more than two times higher.

Therefore, the polymer electrolyte membrane was PEM, the fluid diffusion layer was Ti felt, the cathode electrode was Ag, and the anode electrode was IrO ₂ .

Table 4 summarizes the features of the components of the large area stack according to one embodiment.

2. Performance Evaluation of Stack-1 and Stack-2

(1) constant voltage test

In order to evaluate the performance of the carbon dioxide conversion stack according to an embodiment of the present invention shown in Figure 1, the anode electrolyte and the cathode electrolyte was used to adjust the carbon dioxide saturated 0.1M KHCO ₃ to pH 6.8.

In order to find the potential of generating gas, LSV test was performed to check the change of current while increasing the voltage, and according to the result, the constant voltage test was conducted at 2.6 V to confirm this. Gas samples were collected under stabilized conditions according to the above results to confirm Faraday efficiency and CO conversion, and the results are shown in Table 5.

8A is a graph illustrating LSV test results performed for performance evaluation of a stack for converting carbon dioxide according to an embodiment of the present invention. 8B is a graph showing a result of a constant voltage test performed for performance evaluation of a stack for converting carbon dioxide according to an embodiment of the present invention.

(2) current density change and CO conversion efficiency

9A is a graph showing the change of current density and CO conversion efficiency with time at the constant voltage (2.6 V / cell) of Stack-1, and FIG. 9B is the time at the constant voltage (5.2 V / cell) of Stack-2. It is a graph showing the change of current density and CO conversion efficiency according to.

Referring to FIG. 9A, in the stack-1, the current density is stabilized to about 1.25 A at a constant voltage of 2.6 V, the faradaic efficiency of H ₂ + CO is 3.77%, and the faradaic efficiency of CO is 1.39. % And H ₂ : CO ratio was 63:37.

In the case of Stack-1, when the applied voltage increases from 2.6 V to 3.0 V, the current density increases to 1.75 V, but the overall Faraday efficiency decreases to 2.27%, so an applied voltage of 2.6 V may be appropriate.

Referring to FIG. 9B, in the case of Stack-2, the current density was stabilized to about 0.75 A at a constant voltage of 5.2 V, the faradaic efficiency of H ₂ + CO was 7.39%, and the Faraday efficiency of CO was 1.17% and H _2. The CO ratio was 84:16 and the CO conversion was lowered to 50% compared to Stack-1, but the CO Faraday efficiency was 84% (16% reduction).

Therefore, stack-2 has a performance reduction rate of 16% or less, thereby enabling a multicell stack having improved conversion efficiency.

Table 6 summarizes the performance of stack-1 and stack-2.

(3) Current Density Variation According to Electrolyte Supply Flow Rate in Stack-2

10 is a graph showing a change in current density according to a change in the electrolyte supply flow rate in the stack-2.

As shown in FIG. 10, the initial 1.8 L / min electrolyte supply flow rate decreased to 1.6 L / min after about 4000 seconds, and the current density was 25% lower than that maintained at 1.8 L / min (0.75 A). Showed.

When a circulating CO ₂ saturated electrolyte is pumped, the flow rate decreases due to the presence of CO ₂ gas bubbles in the stack or inside the inlet and outlet flow paths, which tends to decrease over time. As this becomes apparent and the performance decreases continuously, it is appropriate to keep the feed flow rate constant above 1.8 L / min.

The present disclosure has been described in detail through specific embodiments, which are intended to specifically describe the present disclosure, and the present disclosure is not limited thereto and may be performed by those skilled in the art within the technical spirit of the present disclosure. It is obvious that modifications and improvements are possible. Simple modifications and variations of the present disclosure are all within the scope of the present disclosure, and the specific scope of protection of the present disclosure will be apparent from the appended claims.

10: membrane electrode assembly
11, 111, 211: separator
11a: through hole
11b: body
11c, 11e, 111c, 211e: inflow channel
11d, 11f, 111d, 211f: discharge flow path
12, 112, 212: electrolyte membrane
13, 113, 213: anode electrode
14, 16, 114, 116, 214, 216: fluid diffusion layer
15, 115, 215: cathode electrode
20, 22, 120, 122, 124: current collector
21: bipolar plate
30, 32: insulation plate
40, 42, 140, 142: end plate
50: drive power
100, 200: cell

Claims (16)

A polymer electrolyte membrane, and an anode electrode and a first fluid diffusion layer are sequentially stacked on one surface of the electrolyte membrane,
The cathode electrode and the second fluid diffusion layer are sequentially stacked on the other surface of the electrolyte membrane,
A through hole for accommodating the first fluid diffusion layer, the anode electrode, the electrolyte membrane, the cathode electrode, and the second fluid diffusion layer, and has a plurality of micro-channels, one side of which is open to the first fluid diffusion layer or the second fluid diffusion layer Including a membrane electrode assembly comprising a separator,
A carbon dioxide conversion stack, wherein the stack has a circular or oval cross section.
The method of claim 1,
The electrolyte membrane is a cation exchange membrane, carbon dioxide conversion stack.
The method of claim 1,
The cathode electrode is composed of silver or silver alloy, carbon dioxide conversion stack.
The method of claim 1,
At least one of the first fluid diffusion layer and the second fluid diffusion layer is composed of a porous felt or foam, carbon dioxide conversion stack.
The method of claim 1,
The membrane electrode assembly is connected to two or more through a current collector,
A first inflow channel connected to the anode electrolyte to flow into the first fluid diffusion layer of the anode electrode of the plurality of membrane electrode assemblies, and a first discharge channel through which the fluid flowing out of the first fluid diffusion layer of the anode electrode of the plurality of membrane electrode assemblies is discharged ; And
A second inflow passage connected to the cathode electrolyte to flow into the second fluid diffusion layer of the cathode electrode of the plurality of membrane electrode assemblies, and a second discharge from which the fluid flowing out of the second fluid diffusion layer of the cathode electrode of the plurality of membrane electrode assemblies is discharged A stack for converting carbon dioxide, comprising a flow path.
The method of claim 5,
The separator further comprises a sealing member for sealing the first fluid diffusion layer or the second fluid diffusion layer, carbon dioxide conversion stack.
The stack for carbon dioxide conversion according to claim 5, further comprising pressurizing means capable of increasing carbon dioxide solubility in at least one of the anode electrolyte and the cathode electrolyte.
The stack for carbon dioxide conversion according to claim 5, wherein the reduction rate of CO production is 20% or less.
The stack for converting carbon dioxide according to any one of claims 1 to 8, wherein a constant voltage is supplied at less than 3 V / cell.
The stack for converting carbon dioxide according to any one of claims 1 to 8, wherein the electrolyte supply flow rate is maintained at 1.8 L / min or more.
The stack for converting carbon dioxide according to any one of claims 1 to 8, which is directly connected to a solar cell.
A carbon monoxide generating device comprising the stack for converting carbon dioxide according to any one of claims 1 to 8.
A carbon dioxide removal apparatus comprising the stack for converting carbon dioxide according to any one of claims 1 to 8.
The carbon dioxide conversion method which converts carbon dioxide into carbon monoxide using the carbon dioxide conversion stack in any one of Claims 1-8.
The method of claim 14, wherein the constant voltage is supplied at less than 3 V / cell.
The carbon dioxide conversion method according to claim 14, wherein the electrolyte supply flow rate is maintained at 1.8 L / min or more.

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