Electrochemical System

This application claims priority to Korean Patent Application No. 10-2024-0047674, filed on Apr. 8, 2024, and Korean Patent Application No. 10-2024-0073918, filed on Jun. 5, 2024, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in their entirety are herein incorporated by reference.

The disclosure relates to an electrochemical system applicable to an electrochemical device configured to reduce carbon oxides.

A reduction product generated on a cathode inside an electrochemical device may cross over an electrolyte membrane and may be contained in an anolyte.

For a high concentration of the reduction product contained in the anolyte inside the electrochemical device, the reduction product may be oxidized on an anode.

When the reduction product is oxidized on the anode inside the electrochemical device, the reduction efficiency of the electrochemical device may be degraded.

Provided is an electrochemical system configured to circulate an anolyte to the outside of an electrochemical device.

Provided is an electrochemical system configured to separate, in real time, a reduction product contained in an anolyte.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

According to an aspect of the disclosure, in an electrochemical system including a purification module configured to separate, in real time, a reduction product reduced by an electrochemical device configured to reduce a carbon oxide, the electrochemical device includes an electrolyte membrane including a first surface and a second surface that are opposite to each other, a cathode arranged in parallel with the first surface of the electrolyte membrane and in which the reduction product is generated, an anode arranged in parallel with the second surface of the electrolyte membrane, and an anolyte for exchanging electric charges with the anode and containing at least a part of the reduction product having crossed over the electrolyte membrane, and the purification module includes a first flow path configured to extract the anolyte to the outside of the electrochemical device, a separation unit configured to separate the reduction product from the anolyte extracted to the outside of the electrochemical device, and a second flow path configured to supply, to the electrochemical device, the anolyte from which the reduction product is separated.

The purification module may control anolyte environmental conditions in the electrochemical device to be constant.

The anolyte environmental conditions controlled by the purification module may include at least one of pH conditions, concentration conditions of the reduction product, and an amount of the anolyte.

The purification module may include a pH sensor configured to measure a pH of the anolyte extracted to the outside of the electrochemical device and/or a concentration sensor configured to measure a concentration of the reduction product contained in the anolyte and an anolyte chamber connected to the second flow path and configured to replenish the anolyte, from which the reduction product is separated, to the inside of the electrochemical device.

The purification module may further include a third flow path connected to the first flow path and the second flow path and through which the anolyte extracted to the outside of the electrochemical device to selectively bypass the separation unit.

The separation unit may include a pervaporation unit or a vacuum membrane distillation unit.

The reduction product may include a multicarbon compound including at least one of methanol, ethanol, 1-propanol, 2-propanol, formic acid, acetic acid, acetaldehyde, and ethylene glycol.

The reduction product may include ethanol.

The anolyte may include at least one of KHCO, KOH, and HSO.

The electrochemical device may include a membrane electrode assembly (MEA) or a flow cell.

According to an aspect of the disclosure, a method of controlling anolyte environmental conditions in an electrochemical device configured to reduce a carbon oxide includes: circulating an anolyte to communicate with a purification module arranged outside the electrochemical device, measuring, by the purification module, the anolyte environmental conditions, separating, by a separation unit in the purification module, a reduction product from the anolyte, when the anolyte environmental conditions do not satisfy a predetermined criterion, and supplying the anolyte, from which the reduction product is separated, back to inside of the electrochemical device.

The anolyte environmental conditions may include pH conditions and/or concentration conditions of the reduction product.

The measuring, by the purification module, of the anolyte environmental conditions may include measuring, by a detection sensor disposed on a first flow path arranged in a front end of the separation unit, the anolyte environmental conditions.

The measuring, by the purification module, of the anolyte environmental conditions may include measuring, by a detection sensor disposed on a second flow path arranged in a rear end of the separation unit, the anolyte environmental conditions.

A case where the anolyte environmental conditions do not satisfy the predetermined criterion may include a case where a pH of the anolyte extracted to an outside of the electrochemical device is less than or equal to a first preset value or a case where a concentration of the reduction product is greater than or equal to a second preset value.

The method may further include, after the measuring, by the purification module, of the anolyte environmental conditions, when the pH of the anolyte exceeds the first preset value or the concentration of the reduction product is less than the second preset value, supplying, by the purification module, the anolyte, extracted to the outside of the electrochemical device, back to the electrochemical device without to passing through the separation unit.

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

Hereinafter, various embodiments disclosed herein will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals denote like components, and sizes of components in the drawings may be exaggerated for convenience of explanation. Meanwhile, embodiments to be described are merely examples, and various modifications may be made from such embodiments. When an expression “above” or “on” may include not only “directly on/under/at left/right contactually”, but also “on/under/at left/right contactlessly”. Singular forms may include plural forms unless apparently indicated otherwise contextually. When a portion is referred to as “comprises” a component, the portion may not exclude another component but may further include another component unless stated otherwise. The use of the terms of “the above-described” and similar indicative terms may correspond to both the singular forms and the plural forms. When there is an explicit description of the order of operations of the method or there is no description contrary thereto, these operations may be performed in an appropriate order and the order is not necessarily limited to the described order. The term used herein such as “unit” or “module” indicates a unit for processing at least one function or operation, and may be implemented in hardware, software, or in a combination of hardware and software. Connections of lines or connection members between components shown in the drawings are illustrative of functional connections and/or physical or circuit connections, and in practice, may be represented as alternative or additional various functional connections, physical connections, or circuit connections. The use of all examples or exemplary terms is only to describe technical spirit in detail, and the scope is not limited by these examples or terms unless limited by the claims.

It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein. Hereinbelow, an electrochemical systemaccording to an embodiment will be described in more detail.

is a schematic diagram of the electrochemical systemaccording to an embodiment.is an exploded perspective view of an electrochemical deviceaccording to an embodiment.

Referring to, the electrochemical systemaccording to an embodiment may include the electrochemical deviceconfigured to reduce carbon oxides. A carbon oxide that may be reduced by the electrochemical devicemay include, but not limited to, at least one type of a carbon dioxide and a carbon monoxide. The carbon oxide may be reduced to a multicarbon compound by the electrochemical device. The electrochemical devicemay synthesize the multicarbon compound by reducing the carbon oxide. Herein, the multicarbon compound may include methanol, ethanol, 1-propanol, 2-propanol, formic acid, acetic acid, acetaldehyde, ethylene glycol, etc.

The electrochemical deviceaccording to an embodiment may reduce the carbon oxide by reducing the carbon oxide supplied from the outside into a multicarbon compound. The electrochemical devicemay reduce the carbon oxide supplied from the outside to the multicarbon compound, e.g., ethanol, etc. The carbon oxide reduced by the electrochemical devicemay be referred to as a “reduction product”.

The electrochemical deviceaccording to an embodiment may include an electrolyte membrane, a cathode, and an anode. The electrolyte membranemay exchange electric charges with the cathode. The electrolyte membranemay exchange electric charges with the anode. The electrolyte membranemay be disposed between the cathodeand the anodeand may electrically connect the cathodeto the anode. The electrolyte membranemay include, but is not limited to, an anion exchange membrane (“AEM”) or a cation exchange membrane (“CEM”). For example, the electrolyte membranemay include a proton exchange membrane (“PEM”).

The electrochemical deviceaccording to an embodiment may include a first housingand a second housing. Between the first housingand the second housing, the cathode, the electrolyte membrane, and the anodemay be sequentially disposed. The first housingmay face the cathode. The carbon oxide may be supplied to the inside of the electrochemical devicethrough the first housing. The carbon oxide may be supplied to the cathodethrough the first housing.

When the electrochemical deviceaccording to an embodiment operates, a reduction reaction may occur on the cathode. The carbon oxide may be reduced to a reduction product on the cathodeof the electrochemical device. The reduction product may be generated on the cathode. At least a part of the reduction product may travel to the outside of the electrochemical devicethrough the first housing. However, at least a part of the reduction product may cross over the electrolyte membranein a direction toward the anode, as described below in more detail.

The electrolyte membraneaccording to an embodiment may include a first surfaceand a second surfacethat are opposite to each other. The cathodeand anodemay be formed in a film form to correspond to the first surfaceand the second surfaceof the electrolyte membrane, respectively. The cathodemay be disposed on the first surfaceof the electrolyte membrane. The anodemay be disposed on the second surfaceof the electrolyte membrane.

External voltage may be applied to the anodeand the cathodesuch that the electrochemical deviceaccording to an embodiment may reduce the carbon oxide. External voltage may be applied between the anodeand the cathodesuch that a current density of 50 microamperes per square centimeters (mA/cm) or more may be formed between the anodeand the cathodeof the electrochemical device. In another embodiment, external voltage may be applied to the anodeand the cathodesuch that a current density of 100 mA/cmor more may be formed between the anodeand the cathodeof the electrochemical device.

The cathodeaccording to an embodiment may be disposed to face the first surfaceof the electrolyte membrane. That is, the cathodemay be disposed in parallel to the first surfaceof the electrolyte membrane. When the cathodeis disposed in parallel to the first surfaceof the electrolyte membrane, an area in which the cathodemay exchange electric charges with the electrolyte membranemay be large.

The anodeaccording to an embodiment may be disposed to face the second surfaceof the electrolyte membrane. That is, the anodemay be disposed in parallel to the second surfaceof the electrolyte membrane. When the anodeis disposed in parallel to the second surfaceof the electrolyte membrane, an area in which the anodemay exchange electric charges with the electrolyte membranemay be large.

The cathodeaccording to an embodiment may be pressed onto the first surfaceof the electrolyte membrane. The anodemay be pressed onto the second surfaceof the electrolyte membrane. When the cathodeand the anodeare pressed onto the first surfaceand the second surfaceof the electrolyte membrane, respectively, an electrical resistance between the cathodeand the anodemay not be great. For example, the electrochemical devicemay include a membrane electrode assembly (“MEA”). However, an arrangement relationship among the cathode, the anode, and the electrolyte membraneis not limited to the foregoing description. For another example, the electrochemical devicemay include a flow cell in which the cathodeand the electrolyte membraneare separated from each other by a predetermined space and a catholyte electrically connects the cathodeto the electrolyte membrane.

The first surfaceand the second surfaceof the electrolyte membraneaccording to an embodiment may have the same type of electric charges. For example, the first surfaceand the second surfaceof the electrolyte membranemay have positive electric charges. For another example, the first surfaceand the second surfaceof the electrolyte membranemay have negative electric charges. However, the types of the electric charges of the first surfaceand the second surfaceof the electrolyte membraneare not limited to the foregoing description. For still another example, the first surfaceand the second surfaceof the electrolyte membranemay have different types of electric charges.

The electrolyte membranebetween the cathodeand the anodeaccording to an embodiment may include one type of an AEM or a PEM. For example, the cathodeand the anodemay contact opposite sides of the AEM. For another example, the cathodeand the anodemay contact opposite sides of the PEM. When the electrolyte membranebetween the cathodeand the anodeincludes one type of exchange membranes, a resistance of the MEA may not be great. When the electrolyte membranebetween the cathodeand the anodeincludes one type of exchange membranes, stability of the MEA may be high. However, the foregoing description of the type of electrolyte membranebetween the cathodeand the anodeis only an example description and the disclosure is not limited thereto. For another example, the electrolyte membranemay include a bipolar membrane formed by joining an AEM and a PEM.

The electrochemical deviceaccording to an embodiment may include an anolyte. The anolyte may exchange electric charges with the anode. The anolyte may include, but not limited to, at least one of KHCO, KOH, and HSO. A concentration of the anolyte may be, but not limited to, at least about 0.01 molarity (M) but not more than about 10 M.

The anodeaccording to an embodiment may include a porous material. At least a part of the anolyte may be dipped in the anode. The anolyte may electrically connect the electrolyte membraneto the anode. However, the foregoing description of the material of the anodeand electrical connection between the electrolyte membraneand the anodeis only an example, and the disclosure is not limited thereto.

The anolyte according to an embodiment may be circulated in communication with the outside of the electrochemical device. More specifically, at least a part of the anolyte may be extracted to the outside of the electrochemical device, undergo a predetermined treatment process, and be supplied to the inside of the electrochemical device. By circulating the anolyte in communication with the outside of the electrochemical device, anolyte environmental conditions in the electrochemical devicemay be controlled to be constant. More specifically, by circulating the anolyte in communication with the outside of the electrochemical device, an oxide oxidized on the anodemay be discharged to the outside of the electrochemical device. For example, when the anolyte is circulated, hydroxide ions generated on the cathodemay be discharged to the outside of the electrochemical device. For example, when the anolyte is circulated, oxygen molecules generated on the cathodemay be discharged to the outside of the electrochemical device.

The second housingaccording to an embodiment may be disposed to face the anode. The second housingmay include an anolyte extraction unitand an anolyte supply unit. At least a part of the anolyte may be extracted to the outside of the electrochemical devicethrough the anolyte extraction unitof the second housingand may be supplied back to the inside of the electrochemical devicethrough the anolyte supply unitafter passing through a predetermined treatment process.

In addition, at least a part of a reduction product generated on the cathodemay cross over the electrolyte membrane. More specifically, the reduction product generated on the cathodemay move through the first surfaceand the second surfaceof the electrolyte membranein a direction toward the anode. For example, ethanol generated on the cathodemay move through the first surfaceand the second surfaceof the electrolyte membranein a direction toward the anode. The anolyte may contain at least a part of the reduction product crossing over the electrolyte membrane. The reduction product crossing over the electrolyte membranemay accumulate in the anolyte. In this case, when the concentration of the reduction product contained in the anolyte is excessive, the reduction product may be oxidized on the anode. For example, when the ethanol generated on the cathodecrosses over the electrolyte membraneand accumulates excessively in the anolyte, the ethanol may be oxidized to acetate on the anode. For example, when the ethanol generated on the cathodecrosses over the electrolyte membraneand accumulates excessively in the anolyte, the ethanol may be oxidized to acetaldehyde on the anode. When the reduction product is oxidized on the anode, the pH inside the electrochemical devicemay decrease. In other words, the pH of the anolyte inside the electrochemical devicemay decrease. When the pH of the anolyte inside the electrochemical deviceis excessively low, the reduction efficiency of the electrochemical devicemay decrease. Herein, the reduction efficiency may include, but not limited to, a Faraday efficiency (“FE”). In this case, by controlling the concentration of the reduction product contained in the anolyte not to increase excessively, the reduction efficiency of the electrochemical devicemay be prevented from being degraded due to excessive oxidation of the reduction product on the anode.

The electrochemical systemaccording to an embodiment may include a purification module. The purification modulemay be configured to separate, in real time, a reduction product reduced by the electrochemical device. The separation of the reduction product by the purification modulemay include separating the reduction product contained in the anolyte from the anolyte. The “real-time separation” may mean, but not limited to, that an operation of the electrochemical deviceand the separation of the reduction product are performed at the same time.

The purification moduleaccording to an embodiment may control the anolyte environmental conditions in the electrochemical deviceto be constant. The anolyte environmental conditions may include pH conditions. Controlling the anolyte environmental conditions to be constant may include controlling the pH of the anolyte not to fall out of a predetermined range. The anolyte environmental conditions may include concentration conditions of the reduction product. Controlling the anolyte environmental conditions to be constant may include controlling the concentration of the reduction product contained in the anolyte not to fall out of a predetermined range. When the purification modulecontrols the anolyte environmental conditions to be constant, the reduction efficiency of the electrochemical devicemay be effectively prevented from degrading.

The purification moduleaccording to an embodiment may be disposed the outside the electrochemical device. The purification modulemay circulate the anolyte to the outside of the electrochemical device. More specifically, the purification modulemay extract at least a part of the anolyte to the outside of the electrochemical deviceand supply the anolyte back to the inside of the electrochemical deviceafter a predetermined treatment process. The concentration of the reduction product contained in the anolyte extracted from the inside of the electrochemical deviceby the purification modulemay be different from, but not limited to, the concentration of the reduction product contained in the anolyte supplied to the electrochemical deviceby the purification module.

The purification moduleaccording to an embodiment may include a first flow path, a separation unit, and a second flow path. The first flow pathmay be configured to extract at least a part of the anolyte to the outside of the electrochemical device. The first flow pathmay be connected to, for example, but not limited to, the anolyte extraction unitof the second housing. The separation unitmay be connected to the first flow path. At least a part of the anolyte inside the electrochemical devicemay reach the separation unitvia the first flow path. The separation unitmay separate the reduction product from the anolyte extracted to the outside of the electrochemical device. The second flow pathmay be connected to the separation unit. The second flow pathmay supply the anolyte from which the reduction product is separated, to the electrochemical device. The second flow pathmay be connected to, for example, but not limited to, the anolyte supply unitof the second housing. That is, the purification modulemay circulate the anolyte to the outside of the electrochemical devicevia the first flow path, the separation unit, and the second flow path.

The separation unitaccording to an embodiment may reduce the concentration of the reduction product contained in the anolyte circulated in the purification module. In other words, the concentration of the reduction product contained in the anolyte may decrease as the anolyte passes through the separation unit. The concentration of the reduction product contained in the anolyte moving in the second flow pathmay be lower than the concentration of the reduction product contained in the anolyte moving in the first flow path. The purification modulemay extract the anolyte including the reduction product of a high concentration in the electrochemical deviceand separate the reduction product from the anolyte, thereby supplying the anolyte including the reduction product of a low concentration to the electrochemical device. The purification modulemay extract the anolyte in the electrochemical device, separate the reduction product contained in the anolyte, and supply the anolyte, from which the reduction product is separated, back to the electrochemical device, thereby controlling the concentration of the reduction product contained in the anolyte in the electrochemical deviceto be maintained below a predetermined value. The purification modulemay control the concentration of the reduction product contained in the anolyte in the electrochemical devicenot to be excessively high, thereby effectively preventing the reduction efficiency of the electrochemical devicefrom decreasing.