Electrochemically mediated gas capture including from low concentration streams

Abstract

Methods, apparatus and systems are provided for electrochemical separation of a target gas from a gas mixture. In some cases, an electrochemical cell is used to capture and optionally release a target gas such as carbon dioxide (e.g., by bonding to an electroactive species in a reduced state). Some embodiments are particularly useful for selectively capturing a target gas while reacting little or no with oxygen that may be present in the gas mixture. Some such embodiments may be used in applications involving separation from a gas mixture having a relatively low concentration of the target gas, such as direct air capture and ventilation air treatment.

Description

[0001] Related Applications

[0002] This application is a continuation-in-part of U.S. patent application No. 16 / 659,398, entitled “Electrochemically Mediated Gas Capture, Including from Low Concentration Streams,” filed on October 21, 2019, and is also a continuation-in-part of International Patent Application No. PCT / US2019 / 057224, entitled “Electrochemically Mediated Gas Capture, Including from Low Concentration Streams,” filed on October 21, 2019, each of which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 62 / 892,962, entitled “Electrochemically Mediated Carbon Capture from Low Concentration Streams,” filed on August 28, 2019, all of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0003] Methods, apparatus, and systems related to electrochemical separation of a target gas from a gas mixture are generally described. Background Art

[0004] Efforts are made to remove target substances from gas mixtures. For example, over the past two decades, efforts have been made to mitigate global warming by suppressing anthropogenic carbon dioxide (CO2) emissions. Many methods have been carried out, such as conventional thermal methods to process carbon dioxide capture at different stages of its production: capturing it after combustion in power plants, or concentrating it from the atmosphere, then pressurizing it and storing it in geological formations, or converting it into commercially useful chemical compounds. Other potential applications for target gas removal include removing the target gas directly from air or from ventilated air. Improved devices, methods and / or systems are desired. Summary of the invention

[0005] Provided are methods, apparatus and systems associated with the electrochemical separation of a target gas from a gas mixture. In some cases, an electrochemical cell is used to capture and optionally release a target gas such as carbon dioxide (e.g., by bonding to an electroactive substance in a reduced state). Some embodiments are particularly useful for selectively capturing a target gas while reacting little or no with oxygen that may be present in a gas mixture. Some such embodiments may be used for applications involving separation from a gas mixture with a relatively low concentration of the target gas, such as direct air capture and ventilation air treatment. In some cases, the subject matter of the present invention relates to associated products, alternative solutions to specific problems and / or a variety of different uses of one or more systems and / or articles.

[0006] In one aspect, an electrochemical cell is described. In some embodiments, the electrochemical cell includes a negative electrode comprising a first electroactive substance; a positive electrode; and a separator between the negative electrode and the positive electrode, the separator being capable of containing a conductive liquid, wherein the first electroactive substance has an oxidized state and at least one reduced state, in which the substance is capable of bonding with a target gas, but for the at least one reduced state, the reaction with oxygen (O2) at at least one temperature is thermodynamically unfavorable. In some embodiments, the first electroactive substance has at least one reduced state, in which the substance is capable of bonding with a target gas, but for the at least one reduced state, the reaction with oxygen (O2) at at least one temperature greater than or equal to 223K and less than or equal to 573K is thermodynamically unfavorable. In some embodiments, the first electroactive substance has at least one reduced state, in which the substance is capable of bonding with a target gas, but for the at least one reduced state, the reaction with oxygen (O2) at at least one temperature greater than or equal to 223K and less than or equal to 373K is thermodynamically unfavorable.

[0007] In some embodiments, the electrochemical cell comprises: a negative electrode comprising a first electroactive substance fixed to the negative electrode; and a positive electrode; wherein the first electroactive substance has an oxidized state and at least one reduced state, in which the substance is capable of bonding with a target gas, but for the at least one reduced state, the reaction with oxygen (O2) at at least one temperature is thermodynamically unfavorable. In some embodiments, the first electroactive substance has at least one reduced state, in which the substance is capable of bonding with a target gas, but for the at least one reduced state, the reaction with oxygen (O2) at at least one temperature greater than or equal to 223K and less than or equal to 573K is thermodynamically unfavorable. In some embodiments, the first electroactive substance has at least one reduced state, in which the substance is capable of bonding with a target gas, but for the at least one reduced state, the reaction with oxygen (O2) at at least one temperature greater than or equal to 223K and less than or equal to 373K is thermodynamically unfavorable.

[0008] In another aspect, a gas separation system is described. In some embodiments, the gas separation system includes a plurality of electrochemical cells in fluid communication with a gas inlet and a gas outlet, wherein the gas separation system is configured to have a gas flow rate greater than or equal to 0.001 L / sec and less than or equal to 500 L / sec. 目标气体 / (kg 床 t b ) for capturing target gas, where kg 床 is the bed weight and t b is the breakthrough time of the gas separation system.

[0009] In another aspect, a method of at least partial gas separation is described. In some embodiments, the method includes applying a potential difference across an electrochemical cell; exposing a gas mixture containing a target gas to the electrochemical cell; and removing an amount of the target gas from the gas mixture during and / or after applying a first potential difference, wherein less than or equal to 0.1% by volume of any oxygen (O2) present in the gas mixture is removed from the gas mixture.

[0010] In some embodiments, the method includes applying a first potential difference across an electrochemical cell; exposing a first amount of an input gas mixture comprising a target gas to the electrochemical cell; allowing at least a portion of the target gas to bond with an electroactive substance of the electrochemical cell during and / or after applying the first potential difference to produce a first treated gas mixture having a lower amount of target gas than the first gas mixture; applying a second potential difference across the electrochemical cell; and releasing some or all of the target gas bonded to the electroactive substance to produce a second treated gas mixture; wherein, during and / or after the release, the method further includes flowing the second gas through the electrochemical cell to remove at least some or all of the released target gas from the electrochemical cell, and / or applying vacuum conditions to the electrochemical cell to remove at least some or all of the released target gas from the electrochemical cell.

[0011] Other advantages and novel features of the present invention will become apparent from the following detailed description of various non-limiting embodiments of the present invention when considered in conjunction with the accompanying drawings. In the event that this specification and documents incorporated by reference include conflicting and / or inconsistent disclosures, this specification shall prevail. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Some non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is generally represented by a single numeral. For clarity, not every component is indicated in every figure, nor is every component of every embodiment of the present invention shown, where illustration is not required for one of ordinary skill in the art to understand the present invention. In the drawings:

[0013] Figure 1A shows a schematic side view of an exemplary electrochemical cell including a negative electrode and a positive electrode according to one or more embodiments;

[0014] Figure 1B shows a schematic side view of an exemplary electrochemical cell including a negative electrode, a positive electrode, and a separator according to one or more embodiments;

[0015] Figure 2 shows an exploded schematic diagram of an exemplary electrochemical cell according to one or more embodiments;

[0016] Figure 3A shows an exploded schematic diagram of an electrochemical cell operating in a charging mode according to one or more embodiments;

[0017] Figure 3B shows an exploded schematic diagram of an exemplary electrochemical cell operating in a discharge mode according to one or more embodiments;

[0018] Figure 4 shows a schematic diagram of an exemplary gas separation system according to one or more embodiments;

[0019] Figure 5A A schematic diagram illustrating an exemplary system for performing a gas separation process according to one or more embodiments is shown;

[0020] Figure 5B A schematic diagram showing an exemplary system including a flow field for performing a gas separation process according to one or more embodiments is shown;

[0021] Figures 5C to 5E shows a side schematic view of an exemplary flow field channel pattern according to one or more embodiments;

[0022] Figure 6 shows a schematic diagram of an exemplary gas separation system according to one or more embodiments;

[0023] Fig. 7A A schematic diagram illustrating an exemplary system for performing a gas separation process according to one or more embodiments is shown;

[0024] Figure 7B A schematic diagram illustrating an exemplary system for performing a gas separation process according to one or more embodiments is shown;

[0025] Figures 8A to 8B shows a schematic diagram of a method for flowing a gas through a bed of an electrochemical device according to one or more embodiments;

[0026] Fig. 9 Electrochemical data are shown for various quinones and oxygen according to one or more embodiments.

[0027] Fig. 10A A schematic diagram showing an exemplary system including a plurality of electrochemical cells for performing a gas separation process according to one or more embodiments;

[0028] Fig. 10B A schematic diagram of an exemplary system for performing a gas separation process according to one or more embodiments is shown, the system comprising a plurality of electrochemical cells electrically connected in parallel;

[0029] Fig. 10C A schematic diagram of an exemplary system for performing a gas separation process according to one or more embodiments is shown, the system comprising a plurality of electrochemical cells electrically connected in series;

[0030] Fig.11A schematic diagram of an exemplary system for performing a gas separation process according to one or more embodiments is shown, the system comprising a plurality of electrochemical cells electrically connected in series and one or more conductive materials between the electrochemical cells;

[0031] Figures 12A to 12D 2-Chloro-9,10-anthraquinone (AQ-Cl) ( Fig. 12A )、9,10-anthraquinone ester derivatives (AQ-COO-C3H7) ( Fig. 12B )、9,10-anthraquinone (AQ) ( Fig. 12C ) and ether derivatives of 9,10-anthraquinone (AQ-O-C3H7) ( Fig.12D ) Cyclic voltammetry in a 0.1 M [n-Bu4N]PF6 solution in DMF saturated with N2 (left) or CO2 (right);

[0032] Figures 13A to 13B shows that p-benzoquinone (BQ) ( Fig.13A ) and p-naphthoquinone (p-NQ) ( Fig. 13B ) Cyclic voltammetry in a 0.1 M [n-Bu4N]PF6 solution in DMF saturated with N2 or CO2;

[0033] Fig.14 Shown is the cyclic voltammetry of p-naphthoquinone (p-NQ) in a solution of 0.1 M [n-Bu4N]PF6 in DMF saturated with increasing concentrations of CO2 gas (balanced with N2);

[0034] Fig.15 shows the cyclic voltammetry of 5 mM p-naphthoquinone (p-NQ) in a solution of 0.1 M [n-Bu4N]PF6 in DMF saturated with 20% CO2 (balanced with N2) at different scan rates; and

[0035] Figures 16A to 16B 9,10-phenanthrenequinone (PQ) ( Fig.16A ) and o-naphthoquinone (o-NQ) ( Fig. 16B ) Cyclic voltammetry in a 0.1 M [n-Bu4N]PF6 solution in DMF saturated with N2 or CO2. Specific implementation plan

[0036] Provided are methods, apparatus and systems for electrochemical separation of a target gas from a gas mixture. In some cases, an electrochemical cell is used to capture and optionally release a target gas such as carbon dioxide (e.g., by bonding to an electroactive substance in a reduced state). Some embodiments are particularly useful for selectively capturing a target gas while reacting little or no with oxygen that may be present in a gas mixture. Some such embodiments may be used for applications involving separation from a gas mixture with a relatively low concentration of the target gas, such as direct air capture and ventilation air treatment. Certain such embodiments are less energy intensive or less costly than certain prior arts (e.g., thermal or pressure fluctuation target gas separation).

[0037] In some aspects, methods of at least partially separating gas mixtures are generally described, as well as electrochemical cells and gas separation systems that can be used for such applications. Certain aspects relate to applying a potential difference across an electrochemical cell and exposing a gas mixture (e.g., a low concentration mixture, such as ambient air, ventilation air) containing a target gas (e.g., CO2) to the electrochemical cell. The electrochemical cell may include an electrode comprising certain electroactive substances (e.g., certain optionally substituted quinones or polymer derivatives thereof), which can reach a state generated by the electrochemical potential that is capable of reacting with the target gas but not with potential interfering substances (e.g., oxygen). The reaction between the electroactive substance and oxygen can be reduced or avoided by carefully selecting the electroactive substance (e.g., selecting an electroactive substance with such a reduced state: the reduced state is capable of bonding with the target gas, but for the reduced state, the reaction with oxygen is thermodynamically unfavorable). Certain other aspects relate to methods of gas flow during the capture and release process, and a gas separation system that can capture the target gas with high productivity even in the case of a low concentration gas mixture.

[0038] Targeted gas capture, including from low-concentration target gas streams, can be very valuable but difficult to do inexpensively without using energy-intensive methods. Existing conventional methods and systems have many disadvantages, including high energy requirements and waste. In addition, conventional thermal methods of capturing target gases, such as carbon dioxide, often fail to meet increasingly stringent efficiency and capacity standards set by regulatory agencies.

[0039] As a specific example with respect to the removal of carbon dioxide gas, while most such applications target streams with high CO2 concentrations (3% to 15%) from industry, power generation, and other such point sources, it may be desirable to remove CO2 from enclosed spaces for ventilation purposes in buildings and vehicle cabins, or for cabin environmental control systems onboard spacecraft and submarines, where the maximum CO2 concentration allowed in habitable spaces is 5,000 ppm (or 0.5%). However, in such applications, low CO2 concentrations present challenges, perhaps due to the low driving force and the large number of other substances present in the air in addition to CO2. Such concerns also prevail with direct air capture of CO2 from the atmosphere at concentrations of about 400 ppm, which may be worth considering as a long-term mitigation strategy.

[0040] In particular, with respect to electrochemical CO2 capture (although relevant to other target gases), the electrochemistry of O2 can play an important role in the electrochemically mediated separation of target CO2, particularly in gas mixtures having relatively high oxygen concentrations and / or relatively low CO2 concentrations (e.g., vented air applications, direct air capture applications, etc.). Certain electroactive species that may be suitable for reacting with CO2 when in a reduced state may also be able to react with O2. As a non-limiting example, quinones typically undergo two consecutive one-electron reductions in aprotic electrolyte solutions (e.g., conductive liquids), and both of these reduced states have been observed to effectively complex with CO2. In the context of the present disclosure, it has been found that the standard reduction potential for activating quinones is an important parameter for identifying suitable redox-active molecules for electrochemical CO2 separation. In aprotic electrolyte solutions, the one-electron reduction of dissolved O2 gas produces stable superoxide ions (O2 - ), which can be an effective nucleophile. Superoxide ions undergo nucleophilic addition to carbonyl atoms bonded to electron-withdrawing leaving groups such as anhydrides and esters. Previous studies have shown that superoxide ions are reactive toward CO2 in aprotic electrolyte solutions to generate anionic radical intermediates CO4 -· , which subsequently forms peroxydicarbonate C2O6 2- . In addition, it has been observed in the context of the present disclosure that the use of common alkyl carbonate electrolytes, such as propylene carbonate and ethylene carbonate, is not recommended when superoxide ions are generated in any electrochemical process. Therefore, the standard reduction potential for the single electron reduction of O2 is an important parameter that helps identify suitable redox-active molecules for electrochemical CO2 separation. In addition, chemical oxidation of the electrochemically reduced (activated) electrode by oxygen molecules can produce a charge imbalance in the electrochemical cell. In some cases, this charge imbalance can render the target gas capture electrode inactive to the target gas.

[0041] Certain methods and electrochemical cells that exploit these insights have been developed and are generally described herein. In some cases, the methods and electrochemical cells and systems involve an Electro-Swing Adsorption (ESA) process that, in some cases, can remove a target gas from a gas mixture while removing little or no oxygen that is present.

[0042] In some aspects, electrochemical cells are described. Figure 1A A schematic diagram of an exemplary electrochemical cell 100 is depicted, which includes a negative electrode 110 and a positive electrode 120. In some cases, the electrochemical cell is suitable for reacting with a target gas from a gas mixture in any of a variety of applications including: at least partially separating a target gas mixture (e.g., ambient air, ventilation air, etc.) having a relatively low concentration of the target gas. As used herein, the term "electrochemical cell" refers to a device in which a redox half-reaction occurs at the negative electrode and the positive electrode. The term "electrochemical cell" is intended to include devices that meet these criteria, even when the performance of the cell may arguably be characterized as more pseudocapacitive than faradaic, so it may also be referred to as a type of capacitor.

[0043] As described above, in some embodiments, the electrochemical cell includes a negative electrode. As used herein, the negative electrode of an electrochemical cell refers to the electrode into which electrons are injected during charging. For example, Figure 1A , when the electrochemical cell 100 is charged (e.g., by applying an electric potential from an external power source), electrons travel through an external circuit (not shown) and enter the negative electrode 110. Thus, in some cases, species associated with the negative electrode may be reduced to a reduced state (a state with an increased number of electrons) during the charging process of the electrochemical cell.

[0044] The electrochemical cell may also include a positive electrode. As used herein, the positive electrode of an electrochemical cell refers to the electrode from which electrons are removed during the charging process. For example, again referring to Figure 1A When the electrochemical cell 100 is charged (e.g., by applying an electric potential from an external power source), electrons pass from the positive electrode 120 and enter an external circuit (not shown). Thus, in some cases, a species associated with the positive electrode may be oxidized to an oxidized state (a state with a reduced number of electrons) during the charging process of the electrochemical cell.

[0045] In some embodiments, the negative electrode comprises a first electroactive substance. As used herein, an electroactive substance generally refers to a reagent (e.g., a chemical entity) that undergoes oxidation or reduction when exposed to an electric potential in an electrochemical cell. It should be understood that when an electrode comprises an electroactive substance, the electroactive substance may be located at the surface of the electrode, at least a portion of the interior of the electrode (e.g., in a hole of the electrode), or both. For example, in some embodiments, the negative electrode 110 in FIG. 1 comprises a first electroactive substance. The first electroactive substance may be on the surface of the negative electrode 110 or near the surface of the negative electrode 110, the first electroactive substance may be inside at least a portion of the negative electrode 110, or a combination of the two.

[0046] In some embodiments, the first electroactive material is fixed on the negative electrode. Such an embodiment can be distinguished from the embodiments of other systems, in which the electroactive material can be freely transferred from one electrode to another electrode by, for example, advection. As generally understood, the material fixed on the electrode (for example, the negative electrode) is a material that cannot freely diffuse away from the electrode or separate from the electrode under a given set of conditions. The electroactive material can be fixed on the electrode in a variety of ways. For example, in some cases, the electroactive material can be fixed on the electrode by bonding (for example, by covalent bonds, ionic bonds and / or intramolecular interactions such as electrostatic forces, van der Waals forces, hydrogen bonds, etc.) to the electrode surface or bonding to the material or material attached to the electrode. In some embodiments, the electroactive material can be fixed on the electrode by adsorption to the electrode. In some cases, the electroactive material can be fixed on the electrode by polymerization to the electrode. In some cases, the electroactive material can be fixed on the electrode by being contained in a composition (for example, coating, composite layer, etc.) applied to or deposited on the electrode. In some cases, the electroactive material (e.g., polymeric electroactive material or molecular electroactive material) is infiltrated into a mat of microfibers or nanofibers or carbon nanotubes such that the electroactive material is fixed relative to the mat. The mat can provide enhanced surface area enhancement for electrolyte and gas passages, as well as an extended network for conductivity. In some embodiments, the electroactive material is part of a gel composition associated with an electrode (e.g., as a layer deposited on the electrode, as a composition infiltrated into the pores of the electrode, or as a composition that at least partially encapsulates a component of the electrode (e.g., a fiber or nanotube of the electrode). Such a gel (e.g., a hydrogel, an ionic gel, an organic gel, etc.) containing an electroactive material can be prepared before being associated with the electrode (e.g., applied as a coating to form a layer), or the gel can be prepared in the presence of an electrode by contacting the electrode with a gel precursor (e.g., a prepolymer solution containing an electroactive material) (e.g., by coating or immersion), and then gel formation can be initiated (e.g., by crosslinking via introduction of a crosslinking agent, a free radical initiator, heating and / or irradiation with electromagnetic radiation (e.g., ultraviolet radiation)).

[0047] In some embodiments described in more detail below, the negative electrode comprises an electroactive composite layer comprising an electroactive material and an additional material (e.g., a carbonaceous material) that is immobilized in a polymer composite. For example, in some embodiments, the electroactive composite layer comprises a composite of a polymer containing a first electroactive material (e.g., a redox-active polymer having a reduction potential in the range described below) and carbon nanotubes (CNTs).

[0048] The first electroactive material can have an oxidized state (having fewer electrons than a reduced state) and at least one reduced state (having more electrons than an oxidized state). As a non-limiting example, if the first electroactive material is benzoquinone, neutral benzoquinone would be considered an oxidized state, semiquinone (the product of adding one electron to neutral benzoquinone) would be considered one reduced state, and benzoquinone dianion (the product of adding one electron to neutral benzoquinone) would be considered another reduced state.

[0049] In some embodiments, the first electroactive material has at least one reduced state in which the material is capable of bonding with a target gas (e.g., CO2). A material capable of bonding with a target gas generally refers to the ability of the material to undergo a bonding reaction with the target gas to a sufficiently significant degree and at a sufficiently significant rate for a useful gas separation process to occur. For example, a material capable of bonding with a target gas may have a carbon monoxide content greater than or equal to 10 at room temperature (23°C). 1 M -1 , greater than or equal to 10 2 M -1 , and / or up to 10 3 M -1 Or higher binding constant with target gas. The material capable of bonding with target gas may be capable of bonding with target gas at time scales of minute order, second order, millisecond order or as low as microsecond or lower order. The material may be capable of bonding with target gas at at least one temperature (e.g., at least one temperature greater than or equal to 223K and less than or equal to 573K, such as 298K). In some embodiments, the material may bond with target gas at a first temperature, but bonding with target gas at a second temperature is thermodynamically and / or kinetically unfavorable. Such temperature dependence may be based on the temperature dependence of Gibbs free energy change between material (e.g., reduced quinone) and target gas (e.g., carbon dioxide). With the help of the insights and guidance of the present disclosure, those of ordinary skill in the art will be able to select a suitable temperature to promote bonding between material and target gas in at least one reduced state thereof.

[0050] In some embodiments, the first electroactive material has an oxidized state in which it is capable of releasing a bound target gas. The first electroactive material may be selected such that in at least one reduced state, it has a strong affinity for the intended target gas for its intended specific application. For example, in some embodiments where CO is the target gas, the first electroactive material may be selected to have a 10 1 Up to 10 3 M -1 In some embodiments, the selected electroactive material may have a binding constant of 10 1 Up to 10 3 M -1 Binding constants with different target gases. It has been observed that some quinones can be used as suitable electroactive species. In some embodiments, in the presence of CO2, the optionally substituted quinone can be reduced to its semiquinone or divalent anion (e.g., in a single step or in multiple steps) and then combined with CO2 to form a complex. Other electroactive species that can form a covalent bond with CO2 to form a carboxylate moiety when reduced can also be used.

[0051] In some embodiments, the first electroactive material has at least one reduced state in which the material is capable of bonding with the target gas, but there is at least one temperature (e.g., 298K) for the at least one reduced state at which the reaction of the material with oxygen (O2) is thermodynamically unfavorable. In some cases, the first electroactive material has at least one reduced state in which the material is capable of bonding with the target gas, but there is at least one temperature (e.g., 298K) for the at least one reduced state at which the reaction of the material with oxygen (O2) is kinetically unfavorable because the rate constant of the reaction is too low to allow the reaction to occur on a time scale commensurate with gas capture (e.g., microseconds, milliseconds, seconds, or minutes). As described above, the ability of the electroactive material to react with the target gas but not with oxygen (at least in a thermodynamically and / or kinetically favorable manner) may be useful in certain applications where relatively large amounts of oxygen are present in the gas mixture to be separated, or when the target gas is present in relatively low amounts (thus, if oxygen is present, it must compete with oxygen for reaction in the at least one reduced state). In some embodiments, the first electroactive material has at least one reduced state in which the material is capable of bonding with a target gas, but for which a reaction of the material with oxygen (O2) is thermodynamically unfavorable at at least one temperature in the range of 223 K or more, 248 K or more, 273 K or more, 298 K or more, and / or up to 323 K, up to 348 K, up to 373 K, up to 398 K, up to 423 K, up to 448 K, up to 473 K, up to 498 K, up to 523 K, up to 548 K, up to 573 K, or more. In some embodiments, the first electroactive material has at least one reduced state in which the material is capable of bonding with a target gas, but for which a reaction of the material with oxygen (O2) is thermodynamically unfavorable at a temperature of 298 K. It is to be understood that, as used herein, a reaction that is thermodynamically unfavorable at a given temperature is one that has a positive Gibbs free energy change (ΔG rxn). For example, a reaction between a substance in at least one reduced state and oxygen can have a Gibbs free energy change (ΔG) greater than 0 kcal / mol, greater than or equal to +0.1 kcal / mol, greater than or equal to +0.5 kcal / mol, greater than or equal to +1 kcal / mol, greater than or equal to +2 kcal / mol, greater than or equal to +3 kcal / mol, greater than or equal to +5 kcal / mol, and / or up to +8 kcal / mol, up to +10 kcal / mol, up to +20 kcal / mol, or more at at least one temperature within the following ranges: rxn ): greater than or equal to 223K, greater than or equal to 248K, greater than or equal to 273K, greater than or equal to 298K, and / or up to 323K, up to 348K, up to 373K, up to 398K, up to 423K, up to 448K, up to 473K, up to 498K, up to 523K, up to 548K, up to 573K, or higher. In some embodiments, the reaction between the species in at least one reduced state and oxygen has a Gibbs free energy change (ΔG) of greater than 0 kcal / mol, greater than or equal to +0.1 kcal / mol, greater than or equal to +0.5 kcal / mol, greater than or equal to +1 kcal / mol, greater than or equal to +2 kcal / mol, greater than or equal to +3 kcal / mol, greater than or equal to +5 kcal / mol, and / or up to +8 kcal / mol, up to +10 kcal / mol, up to +20 kcal / mol, or more at a temperature of 298 K. rxn ).

[0052] It has been found in the context of the present disclosure that some electroactive materials that can bond with the target gas can still be reactive to oxygen or its reduction products (e.g., superoxide ions, divalent peroxide anions, etc.). In some such cases, the reactivity with oxygen or its reduction products is harmful to the gas separation process. For example, the reactivity with oxygen can reduce the efficiency of capturing the target gas, or superoxide ions or peroxide ions can have harmful reactivity to the components of the electrochemical cell (e.g., electroactive materials, target gas, separators, conductive liquids (when present), etc.). However, it has been found in the context of the present disclosure that some specific electroactive materials can have at least one reduced state that can bond with the target gas, but for the reduced state, the reaction with oxygen (O2) is thermodynamically and / or kinetically unfavorable. The examples and selection criteria of some such electroactive materials are described in more detail below.

[0053] In some embodiments, the standard reduction potential for generating at least one reduced state of the first electroactive species in the conductive liquid is greater than the standard reduction potential for oxygen (O2) and superoxide ions (O2 - ) are converted to the standard reduction potential between the two states. Having such a standard reduction potential can help the substance in at least one reduced state to bond with the target gas, while being thermodynamically unfavorable for the reaction with oxygen. As an example, at room temperature, in a conductive liquid of 0.1 M tetrabutylammonium hexafluorophosphate in dimethylformamide (DMF), (O2 / O2 - ) redox couple may have a standard reduction potential of -1.35 V relative to a given reference. Thus, any suitable electroactive species having a standard reduction potential more positive than -1.35 V (for a given reference) in the conductive liquid at room temperature will be referred to as having a standard reduction potential more positive than for oxygen (O2) and superoxide ions (O2 - ) is at least one reduced state that has a standard reduction potential that is more positive for the interconversion between the oxidized state and the at least one reduced state of the first electroactive substance in the conductive liquid than for superoxide (O2 2- ) and peroxide (O2 2- ) are corrected for the standard reduction potentials of the interconversions.

[0054] With the benefit of this disclosure, one of ordinary skill in the art will be able to determine the standard reduction potential of an electroactive substance in a given conductive liquid. For example, one of ordinary skill in the art can use cyclic voltammetry, linear sweep voltammetry, or any other suitable electrochemical technique to measure the standard reduction potential. In some cases where, for example, the cyclic voltammetry wave is irreversible for the electroactive substance, the standard reduction potential can be approximately determined using any suitable technique known to one of ordinary skill in the art, such as peak potential. The standard reduction potential may depend on the temperature at the time of measurement. In some embodiments, the standard reduction potential is measured at any of the above-mentioned temperatures, for example, at 298K.

[0055] In some embodiments, the standard reduction potential for producing at least one reduced state of the first electroactive species in the conductive liquid is at least 5 mV, at least 10 mV, at least 20 mV, at least 50 mV, at least 100 mV, at least 200 mV, at least 400 mV, or more than the standard reduction potential for oxygen (O2) and superoxide ions (O2 -As an example, if the interconversion of oxygen and superoxide ions in a conductive liquid is -1.35 V relative to a given reference, and the standard reduction potential of the electroactive substance for producing the reduced state of the substance is -1.00 V relative to the given reference, then the standard reduction potential of the electroactive substance for producing the reduced state is higher than that for oxygen (O2) and superoxide ions (O2 - ) is 350 mV more positive than the standard reduction potential for the interconversion between oxygen (O2) and superoxide ions (O2). In some embodiments, the standard reduction potential for generating at least one reduced state of the first electroactive species in the conductive liquid is greater than the standard reduction potential for generating at least one reduced state of the first electroactive species in the conductive liquid. - ) is less than or equal to 1 V, less than or equal to 900 mV, less than or equal to 800 mV, less than or equal to 600 mV, or less than or equal to 500 mV.

[0056] In some embodiments, the standard reduction potential for generating at least one reduced state of the first electroactive species in the conductive liquid is greater than that for superoxide ions (O2 - ) and the peroxide divalent anion (O2 2- ) is at least 5 mV, at least 10 mV, at least 20 mV, at least 50 mV, at least 100 mV, at least 200 mV, at least 400 mV or more positive. In some embodiments, the standard reduction potential for generating at least one reduced state of the first electroactive species in the conductive liquid is greater than that for superoxide ion (O2 - ) and the peroxide divalent anion (O2 2- ) is less than or equal to 1 V, less than or equal to 900 mV, less than or equal to 800 mV, less than or equal to 600 mV, or less than or equal to 500 mV.

[0057] The first electroactive substance can be in any suitable form, provided that it meets at least one of the criteria required herein. In some embodiments, the first electroactive substance is or comprises a molecular substance. For example, the first electroactive substance can be or comprises an organic molecule. The first electroactive substance can include one or more functional groups that can bind to the target gas and the gas mixture (for example, when the electroactive substance is in a reduced state). The functional groups can include, for example, carbonyl groups. In some embodiments, the first electroactive substance is part of a polymer, such as a redox-active polymer. The first electroactive substance can be part of a polymer material fixed to the negative electrode. For example, referring to Figure 1A , the first electroactive material may be a portion of a polymer material fixed on the negative electrode 110 of the electrochemical cell 100 .

[0058] In some embodiments, the first electroactive material is or comprises an optionally substituted quinone (i.e., the quinone may comprise functional groups and / or other moieties or bonds bonded to the main structure of the quinone). In some cases, the first electroactive material is or comprises a redox-active polymer comprising an optionally substituted quinone. The choice of a substituent (e.g., a functional group) on the optionally substituted quinone may depend on any of a variety of factors, including, but not limited to, its effect on the standard reduction potential of the optionally substituted quinone. With the benefit of this disclosure, one of ordinary skill will understand how to determine which substituents or combinations of substituents on the optionally substituted quinone are suitable for the first electroactive material based on, for example, synthetic feasibility and the resulting standard reduction potential. Exemplary functional groups that may functionalize the optionally substituted quinone include, but are not limited to, halogen (e.g., chlorine, bromine, iodine), hydroxyl, carboxylate / carboxylic acid, sulfonate / sulfonic acid, alkylsulfonate / alkylsulfonic acid, phosphonate / phosphonic acid, alkylphosphonate / alkylphosphonic acid, acyl (e.g., acetyl, ethyl ester, etc.), amino, amido, quaternary ammonium (e.g., tetraalkylamino), branched or unbranched alkyl (e.g., C1 to C18 alkyl), heteroalkyl, alkoxy, glycoloxy (glycoxy), polyalkylene glycoloxy (e.g., polyethylene glycoloxy), imino, polyimino, branched or unbranched alkenyl, branched or unbranched alkynyl, aryl, heteroaryl, heterocyclyl, nitro, nitrile, thio, and / or carbonyl, any of which is optionally substituted.

[0059] The optionally substituted quinone of the first electroactive material may comprise one or more of the structures selected from formula (IA) and (IB):

[0060]

[0061] Where R 1 , R 2 , R 3 , and R 4 R may be the same or different, and may be hydrogen, halogen (e.g., chlorine, bromine, iodine), hydroxyl, carboxylate / carboxylic acid, sulfonate / sulfonic acid, alkylsulfonate / alkylsulfonic acid, phosphonate / phosphonic acid, alkylphosphonate / alkylphosphonic acid, acyl (e.g., acetyl, ethyl ester, etc.), amino, amido, quaternary ammonium (e.g., tetraalkylamino), branched or unbranched alkyl (e.g., C1 to C18 alkyl), heteroalkyl, alkoxy, glycoloxy, polyalkylene glycoloxy (e.g., polyethylene glycoloxy), imino, polyimino, branched or unbranched alkenyl, branched or unbranched alkynyl, aryl, heteroaryl, heterocyclic, nitro, nitrile, thio, and / or carbonyl, any of which is optionally substituted, and / or R 1 To R 4 Any two adjacent groups of may be joined together to form an optionally substituted ring.

[0062] In some embodiments, the optionally substituted quinone is or comprises an optionally substituted naphthoquinone. In some cases, the optionally substituted quinone is or comprises an optionally substituted anthraquinone. In some embodiments, the optionally substituted quinone is or comprises an optionally substituted phenanthrenequinone (also referred to as an optionally substituted phenanthrene dione). Substituents (e.g., functional groups) can be any one of those listed above.

[0063] In some embodiments, the electroactive material is or comprises one or more of the following: phenanthrenequinone ester (PQ-ester), iodophenanthrenequinone (PQ-I), diiodophenanthrenequinone (PQ-I2), phenanthrenequinone (PQ), o-naphthoquinone (o-NQ), dimethyl-p-naphthoquinone (p-NQ-Me2), p-naphthoquinone (p-NQ), di-tert-butylbenzoquinone (TBQ), and benzoquinone (BQ), whose structures are shown below:

[0064]

[0065] Where R 5 is an optionally substituted branched or unbranched C1 to C18 alkyl group (eg, methyl, ethyl, propyl, butyl, etc.).

[0066] In some cases, other regio-isomers of the above non-limiting examples of electroactive materials may also be suitable (eg, having substituents at different positions of the quinone).

[0067] As described above, the first electroactive material can be part of a redox-active polymer. In some cases, any of the optionally substituted quinones described herein can be part of a redox-active polymer. In some such cases, at least a portion of the redox-active polymer comprises one or more of a main chain and an optionally substituted quinone covalently bonded to the main chain. The main chain generally refers to the longest series of covalently bonded atoms that together form a continuous chain of polymer molecules. In certain other cases, the optionally substituted quinones described herein can be part of the main chain of a redox-active polymer.

[0068] The electroactive material (e.g., the first electroactive material) may include a cross-linked polymer material. For example, in some embodiments, the electroactive material includes a hydrogel, an ion gel, an organogel, or a combination thereof, or is incorporated therein. Such cross-linked polymer materials are generally known in the art, and in some cases the electroactive material described herein may be included as part of a three-dimensional structure (e.g., by a covalent bond). However, in some embodiments, the electroactive material is incorporated into a cross-linked polymer material by adsorption (e.g., physical adsorption and / or chemical adsorption). In some embodiments, the electroactive material includes an extended network. For example, the electroactive material may include a metal organic framework (MOF) or a covalent organic framework (COF). In some embodiments, the electroactive material includes a functionalized carbonaceous material. For example, the electroactive material may include functionalized graphene, functionalized carbon nanotubes, functionalized carbon nanobelts, edge functionalized graphite, or a combination thereof.

[0069] In some embodiments, the separator is between the negative electrode and the positive electrode. Figure 1B , the separator 130 is between the negative electrode 110 and the positive electrode 120. The separator can be used as a protective layer, which can prevent the corresponding electrochemical reactions at each electrode from interfering with each other. The separator can also help to electrically isolate the negative electrode and the positive electrode from each other and / or from other components in the electrochemical cell to prevent short circuits. With the benefit of this disclosure, ordinary technicians will be able to select a suitable separator. The separator may include a porous structure. In some cases, the separator is or includes a porous solid material. In some embodiments, the separator is or includes a film. The film of the separator can be made of a suitable material. For example, the film of the separator can be or include a plastic film. Some non-limiting examples of plastic films include polyamides, polyolefin resins, polyester resins, polyurethane resins, or acrylic resins containing lithium carbonate, or potassium hydroxide, or sodium peroxide-potassium dispersed therein. The material for the separator may include a cellulose film, a polymer material, or a polymer-ceramic composite material. Other examples of separators include polyvinylidene fluoride (PVDF) separators, PVDF-alumina separators, or Celgard.

[0070] In some embodiments, the electrochemical cell includes one or more separators that contain or are capable of containing a conductive liquid (e.g., an ionic liquid). Figure 1B, the separator 130 of the electrochemical cell 100 may contain or be capable of containing a conductive liquid. A conductive liquid generally refers to a liquid having a relatively high conductivity at room temperature (23° C.). The conductive liquid may have a sufficiently high conductivity to facilitate electrochemical reactions in an electrochemical circuit involving a negative electrode and a positive electrode. The conductive liquid is typically ionically conductive because it can facilitate the transport of ions. However, the conductive liquid typically has a relatively low electronic conductivity (e.g., conductivity due to the movement of charges, such as by electrons or holes) to prevent short circuiting of the electrochemical cell.

[0071] In some cases, the separator containing the conductive liquid is at least partially (or completely) soaked with the conductive liquid. For example, the separator can absorb a certain amount of conductive liquid when immersed, coated, impregnated or otherwise related to the conductive liquid. In some such cases where the separator is porous, some or all of the pores of the separator (inside the separator and / or near the surface of the separator) may become at least partially filled with the conductive liquid. In some embodiments, the separator is saturated with the conductive liquid. A separator saturated with a conductive liquid generally refers to a separator containing the maximum amount of conductive liquid that can be accommodated in the volume of the separator at room temperature (23°C) and ambient pressure. In some embodiments, the electrochemical cell can be configured so that no conductive liquid is present in the separator, but the separator can contain a conductive liquid when it is put into operation to perform a gas separation process. One way in which the separator can contain a conductive liquid is by having a relatively high porosity and / or containing a material that can absorb a conductive liquid and / or be wetted by a conductive liquid.

[0072] In some embodiments, the conductive liquid includes an ionic liquid, such as a room temperature ionic liquid (RTIL). The RTIL electrolyte may have low volatility (i.e., a room temperature vapor pressure of less than 10 -5 Pa, for example 10 -10 Pa to 10 -5 In some embodiments, the ionic liquid constitutes substantially all (e.g., at least 80 vol%, at least 90 vol%, at least 95 vol%, at least 98 vol%, at least 99 vol%, at least 99.9 vol%) of the conductive liquid.

[0073] Ionic liquids may contain anionic components and cationic components. Anions of ionic liquids may include, but are not limited to, halides, sulfates, sulfonates, carbonates, bicarbonates, phosphates, nitrates, nitrates, acetates, PF6 - 、BF4 -, trifluoromethanesulfonate, perfluorobutylsulfonate, bis(trifluoromethanesulfonyl)amide, trifluoroacetate, heptafluorobutyrate, haloaluminate, triazolide, and amino acid derivatives (e.g., proline with a proton removed from the nitrogen). The cation of the ionic liquid may include, but is not limited to: imidazole , pyridine Pyrrolidine ,phosphorus , ammonium, sulfonium, thiazole , pyrazoline (pyrazolium), piperidine , triazole , pyrazoline , Azoles ,guanidine and dialkylmorpholine In some embodiments, the room temperature ionic liquid comprises imidazole As a cationic component. As an example, in some embodiments, the room temperature ionic liquid comprises 1-butyl-3-methylimidazole ("Bmim") as a cationic component. In some embodiments, the room temperature ionic liquid comprises bis(trifluoromethylsulfonyl)imide ("TF2N") as an anionic component. In some embodiments, the room temperature ionic liquid comprises 1-butyl-3-methylimidazole represented by the following formula (IIA): Bis(trifluoromethylsulfonyl)imide ([Bmim][TF2 N]):

[0074]

[0075] In some embodiments, the room temperature ionic liquid comprises 1-butyl-3-methylimidazole represented by the following formula (IIB): Tetrafluoroborate (BF4) ([Bmim][BF4]):

[0076]

[0077] In some embodiments, the conductive liquid comprises a low volatility electrolyte solution. For example, the conductive liquid may include a liquid solvent having a relatively high boiling point and ionic species dissolved therein (e.g., dissolved supporting electrolyte ions). The liquid solvent having a relatively high boiling point may be non-aqueous. For example, the liquid solvent may include N,N-dimethylformamide (DMF) and the like.

[0078] Starting with the positive electrode, in some embodiments, the positive electrode comprises a second electroactive substance. The second electroactive substance may be a composition different from the first electroactive substance of the negative electrode, although in some embodiments, the second electroactive substance is the same as the first electroactive substance. In some embodiments, the positive electrode comprises an electroactive layer (sometimes referred to as a complementary electroactive layer) comprising a second electroactive substance. The complementary electroactive layer may be in the form of a composite material and may therefore be a complementary electroactive composite layer. During operation, the second electroactive substance may be used as an electron source for reducing the first electroactive substance present in the negative electrode. Similarly, during oxidation of the first electroactive substance, the second electroactive substance may be used as an electron sink (sink for electron). In this way, the electroactive layer of the positive electrode may be described as "complementary". The second electroactive substance may include, for example, a redox-active polymer. In some embodiments, the redox-active polymer is or comprises a polymer containing ferrocene (e.g., as a portion bonded to the polymer backbone). In some embodiments, the second electroactive substance comprises a metallocene (e.g., ferrocene). In some such cases, the second electroactive substance comprises a redox-active polymer containing a metallocene. As a non-limiting embodiment, the redox-active polymer includes polyvinylferrocene. As another example, the second electroactive material can include a polymer comprising thiophene. In some such cases, the second electroactive material includes poly(3-(4-fluorophenyl)thiophene). In some embodiments, the second electroactive material includes phenothiazine. As another example, in some embodiments, the second electroactive material includes (2,2,6,6-tetramethylpiperidin-1-yl)oxy (referred to as "TEMPO") or a derivative thereof (e.g., including optional substituents). In some cases, the second electroactive material includes such a faradaic redox material: it has a standard reduction potential of at least 0.5 volts (V), at least 0.6V, at least 0.8V, and / or up to 1.0V, up to 1.5V or higher than the first reduction potential of the first electroactive material.

[0079] As with the main electroactive composite layer of the negative electrode, the complementary electroactive composite layer of the positive electrode may include a fixed polymer composite of an electroactive substance and another material (e.g., a carbonaceous material). Some examples of carbonaceous materials include carbon nanotubes (e.g., single-walled carbon nanotubes, multi-walled carbon nanotubes), carbon black, Ketjen Black, carbon black Super P, or graphene. Other materials are also possible. In some cases, the second electroactive substance may be fixed on the positive electrode by being included in a composition (e.g., a coating, a composite layer, etc.) applied to or deposited on the positive electrode. In some cases, the second electroactive substance (e.g., a polymer electroactive material or a molecular electroactive material) infiltrates a pad of microfibers, nanofibers, or carbon nanotubes associated with the positive electrode, so that the second electroactive substance is fixed relative to the pad of the positive electrode. Relative to the first electroactive substance, the second electroactive substance may also be part of a gel associated with the positive electrode in the same or similar manner as described above.

[0080] According to one or more embodiments, the electroactive composite layer of the positive electrode can have a specific weight ratio of electroactive material to carbonaceous material. The weight ratio can be selected to promote high electron current per mass of electroactive material. In some embodiments, the weight ratio of the mass of electroactive material to the mass of carbonaceous material for the complementary electroactive composite layer can be 1 to 2 to 2 to 1. In some embodiments, it can be 1 to 1. Other ratios are also possible.

[0081] In some cases, one or more electrodes of an electrochemical cell include an electroactive composite layer. For example, in some embodiments, the negative electrode includes an electroactive composite layer (e.g., a primary electroactive composite layer). Figure 1B According to some embodiments, the negative electrode 110 includes a composite electroactive composite layer 114 facing the positive electrode 120. In some cases, the positive electrode includes an electroactive composite layer (e.g., a complementary electroactive composite layer). Figure 1B In the embodiment of the present invention, the negative electrode 120 includes an electroactive composite layer 124 facing the negative electrode 110. The electroactive composite layer of the positive electrode can also be referred to as a complementary electroactive composite layer because the electroactive material therein serves as an electron sink or electron source for the electroactive material of the negative electrode. In some cases, the electroactive composite layer of the electrode (e.g., negative electrode, positive electrode) extends through the entire thickness dimension of the electrode. For example, the electroactive composite layer can be inserted through the entire thickness of the electrode. However, in some embodiments, the electroactive composite layer of the electrode does not extend through the entire thickness dimension of the electrode. In some such cases, the electroactive composite layer is inserted through some but not the entire thickness of the electrode. In some cases, the electroactive composite layer is a coating on the surface of another component of the electrode (e.g., current collector, gas permeable layer, etc.).

[0082] In some embodiments, the electroactive material of an electrode (e.g., a first electroactive material of a negative electrode, a second electroactive material of a positive electrode) is part of an electroactive composite layer. Figure 1B In some embodiments, electroactive composite layer 114 comprises a first electroactive material as described herein. Similarly, in some embodiments, electroactive composite layer 124 comprises a second electroactive material (eg, polyvinylferrocene).

[0083] In addition to the electroactive material, the electroactive composite layer of the negative electrode may also include a carbonaceous material. Some examples of suitable materials include, but are not limited to, carbon nanotubes (e.g., single-walled carbon nanotubes, multi-walled carbon nanotubes), carbon black, Ketjen black, carbon black Super P, graphene, or a combination thereof. Other examples also include fixing and / or coating the electroactive material (e.g., in polymer or molecular form or other form) to / on a mat of microfibers, nanofibers, or carbon nanotubes by embedding, grafting, chemical vapor deposition (CVD), or other means.

[0084] According to one or more embodiments, the electroactive composite layer of the negative electrode can have a specific weight ratio of electroactive material to carbonaceous material. The weight ratio can be selected to promote high electron current per mass of electroactive material. In some embodiments, the weight ratio of the mass of electroactive material to the mass of carbonaceous material can be 1 to 1 to 10. In some embodiments, it can be 1 to 3. Other ratios are also possible.

[0085] The negative electrode may also include a gas permeable layer. The gas permeable layer (which may also be referred to as a substrate layer) may be adjacent to the electroactive composite layer and face outward relative to the electrochemical cell. In some embodiments, the gas permeable layer is in contact with the first electroactive substance. In some such cases, the gas permeable layer is in direct contact with the first electroactive substance, while in other such cases, the gas permeable layer is in indirect contact with the first electroactive substance. It should be understood that when one part (e.g., a layer) is "on" or "in contact with" another part, it can be directly on the other part, or there may also be an intermediate part (e.g., a layer) (in this case, the one part is understood to be "indirectly on" another part or "indirectly in contact with" another part). A part "directly on" another part, "directly in contact" with another part means that there is no intermediate part. It should also be understood that when a part is referred to as "on" or "in contact with" another part, it can cover the entire part or a portion of the other part. In some embodiments, the gas permeable layer is in contact with the electroactive composite layer of the negative electrode (e.g., direct contact or indirect contact).

[0086] The gas flow can diffuse through the gas permeable layer to contact the electroactive composite layer.The gas permeable layer can comprise a conductive solid material and serve as a current collector within the battery.

[0087] The gas permeable layer may comprise a porous material. In some embodiments, the gas permeable layer has, for example, a porosity greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, or greater. In some embodiments, the gas permeable layer has a porosity less than or equal to 85%, less than or equal to 90%, or greater. Combinations of these ranges are possible. For example, in some embodiments, the gas permeable layer of the negative electrode has a porosity greater than or equal to 60% and less than or equal to 90%. Other porosities are also possible. Some examples of suitable materials for the gas permeable layer include, but are not limited to, carbon paper (treated, TEFLON treated, or untreated), carbon cloth, and nonwoven carbon mats. Other materials may also be used.

[0088] Although in some embodiments the electrochemical cell includes a single negative electrode, in other embodiments the electrochemical cell includes more than one negative electrode. For example, in some embodiments, the negative electrode described herein is a first negative electrode, and the electrochemical cell includes a second negative electrode. The positive electrode may be between the first negative electrode and the second negative electrode. The second negative electrode may also include a first electroactive material. The second negative electrode may be identical to the first negative electrode in configuration and composition. In some embodiments, the electrochemical cell includes more than or equal to 1 negative electrode, more than or equal to 2 negative electrodes, more than or equal to 3 negative electrodes, more than or equal to 5 negative electrodes, more than or equal to 10 negative electrodes, and / or up to 15 negative electrodes, up to 20 negative electrodes, up to 50 negative electrodes, or more.

[0089] Although in some embodiments the electrochemical cell includes a single separator (e.g., between the negative electrode and the positive electrode), in other embodiments, the electrochemical cell includes more than one separator. For example, in some embodiments, the separator described herein is a first separator, and the electrochemical cell includes a second separator. In some embodiments in which there is a second negative electrode, the second separator may be between the positive electrode and the second negative electrode. The second separator may be the same as the first separator in terms of configuration and composition. In some cases, the second separator can contain a conductive liquid (e.g., saturated with a conductive liquid). In some embodiments, the electrochemical cell includes more than or equal to 1 separator, more than or equal to 2 separators, more than or equal to 3 separators, more than or equal to 5 separators, more than or equal to 10 separators, and / or up to 15 separators, up to 20 separators, up to 50 separators, or more. In some cases, each separator is between the corresponding negative electrode and the positive electrode.

[0090] In some embodiments of an electrochemical cell in which a positive electrode has a negative electrode on either side thereof (e.g., a first negative electrode and a second negative electrode), the positive electrode comprises a second electroactive material facing each negative electrode. In some such embodiments, the positive electrode comprises two complementary electroactive composite layers, each facing one of the negative electrodes.

[0091] The positive electrode may also include a substrate layer positioned near one or more electroactive composite layers or between one or more electroactive composite layers. The substrate layer may be in direct or indirect contact with one or more electroactive composite layers. The substrate layer of the positive electrode may include a material that is the same or different from the material of the substrate layer (when present) of the negative electrode. For example, the substrate layer may include materials such as carbon paper (treated, TEFLON treated, or untreated), carbon cloth, or non-woven carbon mats. In some embodiments, the substrate may include a mat that includes, for example, carbon nanotubes, microfibers, nanofibers, or a combination thereof. Other materials are also possible. The substrate layer of the positive electrode may include a conductive material and be used as a current collector in the battery. In some embodiments, the substrate includes a metal and / or a metal alloy. For example, the substrate may include a metal and / or metal alloy foil (e.g., having a relatively small thickness of less than or equal to 200 microns, less than or equal to 100 microns, less than or equal to 10 microns, and / or as low as 1 micron or less). Some examples of suitable foils may include, but are not limited to, aluminum foil and titanium foil. As a specific example, in some embodiments, the positive electrode includes a substrate between a first complementary electroactive composite layer facing a first negative electrode and a second complementary electroactive composite layer facing a second negative electrode. In this case, if a line extending away from the main body of the electroactive composite layer can intersect a particular electrode (e.g., a negative electrode) without passing through the substrate, the electroactive composite layer of the positive electrode can face the electrode. When an object (e.g., an electroactive composite layer) is in contact with another object, or when one or more intermediate materials are located between a surface and another object, the object can face another object. For example, two objects facing each other can be in contact or can include one or more intermediate materials (e.g., a separator) between them.

[0092] Figure 2An example of an electrochemical cell according to some but not necessarily all embodiments and having one or more of the above-described components is depicted. The electrochemical cell 100 includes a positive electrode 120 between two negative electrodes 110. A separator 130 separates the positive electrode 120 from the negative electrode 110. Each negative electrode 110 includes: an optional gas permeable layer 112, which is positioned away from the center of the cell 100; and an optional main electroactive composite layer 114, which faces the positive electrode 120. In some embodiments, the positive electrode 120 includes a substrate layer 122 and two complementary electroactive composite layers 124 thereon. The different components of the electrochemical cell 100 can have certain characteristics described throughout the present disclosure, for example, including the electrode materials (e.g., electroactive substances) described above. The configuration of the two outward-facing negative electrodes 110, for example, Figure 2 As shown, this provides the advantage of doubling the gas absorption area exposed to the gas in some cases.

[0093] According to one or more embodiments, the target gas includes a nucleophilic molecule. According to one or more embodiments, the target gas may include a non-proton acidic gas. According to one or more embodiments, the target gas includes a gas that can form a complex with the electroactive substance of the negative electrode when the electroactive substance is in its reduced state (e.g., by bonding with the substance in its reduced state). According to one or more embodiments, the target gas includes carbon dioxide (CO2). According to one or more embodiments, the target gas includes sulfur dioxide (SO2). According to one or more embodiments, the target gas includes borane (BR3), wherein each R can be the same or different and is a suitable substituent (e.g., hydrogen, alkyl, aryl, etc., each of which is optionally substituted). In some embodiments, the target gas includes a substance (a type of molecule). In some embodiments, the target gas includes more than one substance (e.g., a first type of molecule and a second different type of molecule). The potential window in which capture and release occur may depend on the specific target gas of the embodiment, so the enrichment and removal of the target gas can be controlled by applying an appropriate potential difference applied across the electrochemical cell.

[0094] In some embodiments, the gas mixture to be at least partially separated from the gas mixture by exposure to the electrochemical cell (e.g., an input gas mixture) is ambient air (e.g., air from the surrounding environment such as outdoor air). Ambient air generally refers to air present in a non-enclosed location, such as outdoors. In some such cases, the electrochemical cell is used for direct air capture. The systems and methods described herein can be useful techniques for removing a target gas, such as carbon dioxide, directly from ambient air (e.g., to reduce greenhouse gas levels) without the need for pre-concentration of the target gas. In some cases, certain aspects of the present disclosure can make the systems and methods described herein particularly useful for direct air capture (e.g., being able to bond with the target gas while being thermodynamically unfavorable to react with a major component of ambient air, such as oxygen).

[0095] In some embodiments, the concentration of the target gas in the gas mixture is relatively low. One such situation can be when the gas mixture is ambient air. In some embodiments, before being exposed to the electrochemical cell, the concentration of the target gas in the gas mixture is less than or equal to 500ppm, less than or equal to 450ppm, less than or equal to 400ppm, less than or equal to 350ppm, less than or equal to 300ppm, less than or equal to 200ppm, or lower. In some embodiments, the concentration of the target gas in the gas mixture is as low as 100ppm, as low as 50ppm, as low as 10ppm, or lower. Combinations of these ranges are possible. For example, in some embodiments, the concentration of the target gas in the gas mixture is less than or equal to 500ppm and as low as 10ppm. In some embodiments where the target gas is carbon dioxide, before being exposed to the electrochemical cell, the concentration of carbon dioxide in the gas mixture is less than or equal to 500ppm, less than or equal to 450ppm, less than or equal to 350ppm, or lower. In some embodiments, the concentration of carbon dioxide in the gas mixture prior to exposure to the electrochemical cell is greater than or equal to 300 ppm, greater than or equal to 350 ppm, or higher. Combinations of these ranges are possible. For example, in some embodiments, the concentration of carbon dioxide in the gas mixture prior to exposure to the electrochemical cell is greater than or equal to 300 ppm and less than or equal to 400 ppm, or greater than or equal to 300 ppm and less than or equal to 500 ppm.

[0096] In some embodiments, the gas mixture to be at least partially separated from the gas mixture by exposure to the electrochemical cell (e.g., the input gas mixture) is ventilation air. The ventilation air can be air in a closed or at least partially closed location (e.g., air circulated in a closed location). Some examples of locations in which the gas mixture (e.g., ventilation air) can be located include, but are not limited to, sealed buildings, partially ventilated locations, car compartments, manned submersibles, aircraft, etc.

[0097] The target gas concentration in the ventilation air may be higher than that in ambient air, but lower than the typical concentration of industrial processes. In some embodiments, before being exposed to the electrochemical cell, the concentration of the target gas in the gas mixture is less than or equal to 5,000ppm, less than or equal to 4,000ppm, less than or equal to 2,000ppm, less than or equal to 1,000ppm or lower. In some embodiments, the concentration of the target gas in the gas mixture (for example, when it is the air in the ventilation air / enclosed space) is as low as 1,000ppm, as low as 800ppm, as low as 500ppm, as low as 200ppm, as low as 100ppm, as low as 10ppm, or lower. Combinations of these ranges are possible. For example, in some embodiments, the concentration of the target gas in the gas mixture is less than or equal to 5,000ppm and as low as 500ppm. In some embodiments where the target gas is carbon dioxide, the concentration of carbon dioxide in the gas mixture is less than or equal to 5,000 ppm, less than or equal to 4,000 ppm, less than or equal to 2,000 ppm, less than or equal to 1000 ppm, less than or equal to 500 ppm, or lower before exposure to the electrochemical cell. In some embodiments, the concentration of carbon dioxide in the gas mixture is greater than or equal to 10 ppm, greater than or equal to 100 ppm, greater than or equal to 300 ppm, greater than or equal to 500 ppm, greater than or equal to 1,000 ppm, greater than or equal to 2,000 ppm, or higher before exposure to the electrochemical cell. Combinations of these ranges are possible. For example, in some embodiments, the concentration of carbon dioxide in the gas mixture is greater than or equal to 500 ppm and less than or equal to 5,000 ppm, or greater than or equal to 10 ppm and less than or equal to 5,000 ppm before exposure to the electrochemical cell.

[0098] In some embodiments, the gas mixture comprises oxygen (O2). In some such embodiments, including those in which the gas mixture comprises ambient air or ventilation air, or even a high purity oxygen mixture. In some but not necessarily all embodiments, the gas mixture has a relatively high concentration of oxygen (e.g., before exposure to an electrochemical cell). Certain aspects of the systems and methods described herein (e.g., selection of specific electroactive materials, methods of treating gases in the system, etc.) can contribute to the ability to capture a target gas in a gas mixture (where oxygen is present) without harmful interference. In some embodiments, oxygen is present in the gas mixture (e.g., prior to exposure to the electrochemical cell) at a concentration of greater than or equal to 0 vol%, greater than or equal to 0.1 vol%, greater than or equal to 1 vol%, greater than or equal to 2 vol%, greater than or equal to 5 vol%, greater than or equal to 10 vol%, greater than or equal to 20 vol%, greater than or equal to 50 vol%, greater than or equal to 75 vol%, greater than or equal to 90 vol%, greater than or equal to 95 vol%, greater than or equal to 99 vol%, greater than or equal to 99.9 vol%, greater than or equal to 99.99 vol%, or more. In some embodiments, oxygen is present in the gas mixture at a concentration less than or equal to substantially 100% by volume, less than or equal to 99.9999% by volume, less than or equal to 99.999% by volume, less than or equal to 99.999% by volume, less than or equal to 99.99% by volume, less than or equal to 99.9% by volume, less than or equal to 99.9% by volume, less than or equal to 99.9% by volume, less than or equal to 99% by volume, less than or equal to 95% by volume, less than or equal to 90% by volume, less than or equal to 75% by volume, less than or equal to 50% by volume, less than or equal to 25% by volume, less than or equal to 21% by volume, less than or equal to 10% by volume, less than or equal to 5% by volume, less than or equal to 2% by volume, or less. Combinations of these ranges are possible. For example, in some embodiments, oxygen is present in the gas mixture at a concentration greater than or equal to 0 vol% and less than or equal to substantially 100 vol% (e.g., for dedicated high O2 combustion processes), greater than or equal to 0 vol% and less than or equal to 50 vol%, greater than or equal to 0 vol% and less than or equal to 21 vol% (e.g., in incomplete combustion processes), and greater than or equal to 10 vol% and less than or equal to 25 vol% (e.g., for ventilation air or direct air capture processes).

[0099] In some embodiments, the gas mixture for at least partial gas separation includes water vapor. For example, the gas mixture may include water vapor because the gas mixture is or includes ambient air or ventilation air. In some cases, the gas mixture (e.g., before being exposed to the electrochemical cell) has a relatively high relative humidity. For example, in some embodiments, the gas mixture has a relative humidity greater than or equal to 0%, greater than or equal to 5%, greater than or equal to 10%, greater than or equal to 25%, greater than or equal to 50%, greater than or equal to 75%, greater than or equal to 90%, or higher at at least one temperature in the range of -50°C to 100°C. In some embodiments, the gas mixture has a relative humidity less than or equal to 100%, less than or equal to 95%, less than or equal to 90%, less than or equal to 75%, less than or equal to 50%, less than or equal to 25%, less than or equal to 10%, or less at least one temperature in the range of -50°C to 100°C.

[0100] The gas mixture (e.g., the input gas mixture) that undergoes at least partial separation by exposure to the electrochemical cell can have any of a variety of pressures when exposed to the electrochemical cell. For example, the gas mixture can have a total pressure (e.g., in a gas separation system) of greater than or equal to 0.1 bar, greater than or equal to 0.2 bar, greater than or equal to 0.5 bar, greater than or equal to 1 bar, greater than or equal to 2 bar, and / or up to 5 bar, up to 8 bar, up to 10 bar, or more. The gas mixture can have any of these pressure values ​​while containing the target gas and oxygen in any of the above concentration ranges.

[0101] According to one or more embodiments, the electrochemical cell generally described herein can be operated to at least partially separate a gas mixture. In some embodiments, the gas mixture is a gas stream. In some embodiments, the gas mixture is air in a ventilation structure, and in some cases, the air is ambient air (e.g., in a direct air capture embodiment). However, the gas mixture is not limited to such an embodiment. For example, in some embodiments, the gas mixture is a gas (e.g., flue gas) from an industrial process. In some embodiments, the electrochemical cell can be operated to carry out a gas separation process involving a gas mixture. For example, the electrochemical cell can be operated to remove a portion of the target gas from the gas mixture. In some such cases, the operation of the electrochemical cell involves exposing the gas mixture to the electrochemical cell. The gas mixture can be exposed to the electrochemical cell so that the target gas is bonded to the first electroactive material to produce a treated gas mixture with a lower amount of target gas than the gas mixture (sometimes referred to as "input gas mixture") initially exposed to the electrochemical cell.

[0102] The process of at least partially separating the target gas from the gas mixture can include applying a potential difference across an electrochemical cell. With the benefit of this disclosure, those of ordinary skill will understand how to apply a potential across an electrochemical cell. One way of applying a potential is to connect the negative electrode and the positive electrode to a suitable power supply that can polarize the negative electrode and the positive electrode. In some embodiments, the power supply is a DC voltage to the system. Some non-limiting examples include batteries, power grids, regenerative power sources (e.g., wind turbines, photovoltaic cells, tidal power generators), generators, etc. The power supply can include one or more such power supplies (e.g., batteries and photovoltaic cells).

[0103] In some embodiments, the process also includes exposing the electrochemical cell to a gas mixture. A potential difference can be applied during at least a portion of the time when the gas mixture is exposed to the electrochemical cell. However, some embodiments include applying a potential difference before the gas mixture is exposed to the electrochemical cell. In other words, in some embodiments, the step of exposing the gas pressure to the electrochemical cell occurs during the step of applying a potential difference across the electrochemical cell and / or after applying a potential difference across the battery. In some embodiments, exposing the gas mixture to the electrochemical cell includes introducing a gas stream containing a target gas (e.g., CO2) into the electrochemical cell so that the target gas is bonded to the first electroactive material to produce a treated gas mixture (e.g., a treated gas stream).

[0104] According to some embodiments, applying a positive voltage to the electrochemical cell during the charging mode causes a redox half-reaction at the negative electrode, wherein the electroactive substance is reduced. As discussed herein, the electroactive substance of the negative electrode is selected because of its following properties: when it is in a reduced state relative to when it is in an oxidized state, it has a higher affinity for the target gas (e.g., CO2). By reducing the electroactive substance and passing a gas mixture (e.g., ventilation air, ambient air, industrial gas flow) through the face of the negative electrode, the target gas (e.g., CO2) can be bonded to the electroactive substance. In this way, the target gas can be removed from the gas mixture to provide a treated gas mixture (e.g., including a smaller amount of target gas than the gas mixture).

[0105] As a non-limiting example, in some embodiments where the electroactive material of the negative electrode is an optionally substituted quinone, the electroactive material can be reduced to at least one of its reduced states according to the following reaction (1):

[0106]

[0107] Again as a non-limiting example, in some embodiments where the electroactive species is reduced in the presence of a target gas comprising carbon dioxide, the following reaction (2) occurs:

[0108]

[0109] According to some embodiments, when the first electroactive species (e.g., an optionally substituted quinone) is reduced at the negative electrode, the second electroactive species (e.g., a redox-active polymer such as polyvinylferrocene) is oxidized at the positive electrode. During the charging mode, the oxidation of the second electroactive species provides an electron source for driving the reduction of the first electroactive species.

[0110] Again as a non-limiting example, in some embodiments where the electroactive material of the positive electrode comprises polyvinylferrocene, the second electroactive material may be oxidized according to the following reaction (3):

[0111]

[0112] Although each of reactions (1) to (3) is shown to occur in one direction, some reversibility may be exhibited. As will be appreciated by one of ordinary skill in the art, similar reactions may occur using different substances.

[0113] In some embodiments, the second electroactive material comprises an intercalation compound. For example, the second electroactive material may comprise a metal ion intercalation compound. An exemplary class of intercalation compounds includes metal oxides. Intercalation compounds may include intercalation compounds of alkali metal ions such as lithium ions and / or sodium ions. In some embodiments, the intercalation compound includes an alkali metal ion transition metal oxide (e.g., lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and / or lithium oxides comprising cobalt, manganese, and / or nickel). In some embodiments, the intercalation compound comprises an alkali metal transition metal polyoxyanion, such as a lithium transition metal phosphate. An example of a suitable lithium transition metal phosphate for a positive electrode is lithium iron phosphate (LiFePO4). In some embodiments, during charging mode, oxidation of a second electroactive material in the form of an alkali metal ion intercalation compound (e.g., LiFePO4) provides an electron source for driving the reduction of the first electroactive material, while releasing alkali metal ions (e.g., lithium ions), which can shuttle through the electrolyte (e.g., on or within a separator (when present)) toward the negative electrode to maintain charge balance and complete the electrochemical circuit. In contrast, during the discharge mode, reduction of the second electroactive material in the form of an alkali metal ion intercalation compound provides a sink for electrons from the oxidation of the first electroactive material, while alkali metal ions (e.g., lithium ions) can shuttle through the electrolyte (e.g., on or within the separator (when present)) from a region near the negative electrode toward the positive electrode, where the alkali metal ions can intercalate into the intercalation compound and maintain charge balance.

[0114] According to one or more embodiments, when the electrochemical cell is charged by applying a potential difference across the positive electrode and the negative electrode, electrons flow from a portion of the second electroactive material on the positive electrode (e.g., the ferrocene (Fc) unit in the pVFc-CNT composite) to the negative electrode through an external circuit, thereby oxidizing the second electroactive material (e.g., by oxidizing ferrocene to ferrocene). (Fc + ) (as shown in reaction (3)). At the negative electrode, the first electroactive substance (e.g., an optionally substituted quinone unit in the CNT composite) is reduced (e.g., reduced to a semiquinone or divalent anion form of the optionally substituted quinone) in the presence of a target gas (e.g., CO2) (which diffuses into the negative electrode). The electroactive substance in its reduced state (e.g., a divalent anion of the optionally substituted quinone) readily binds to CO2 via a covalent bond, as shown in equation (2), to form a complex.

[0115] The potential difference applied across the electrochemical cell during the charging mode can have a specific voltage. The potential difference applied across the electrochemical cell can depend on, for example, the standard reduction potential for producing at least one reduced state of the first electroactive material, and the standard reduction potential for the interconversion between the reduced state and the oxidized state of the second electroactive material (when present). In some embodiments, the potential difference is at least 0V, at least 0.1V, at least 0.2V, at least 0.5V, at least 0.8V, at least 1.0V, at least 1.5V, or higher. In some embodiments, the potential difference is less than or equal to 2.0V, less than or equal to 1.5V, less than or equal to 1.0V, less than or equal to 0.5V, or lower. Combinations of these voltages are also possible. For example, in some embodiments, the potential difference applied across the electrochemical cell is at least 0.5V and less than or equal to 2.0V. Other values ​​are also possible.

[0116] Figure 3A An exploded view of an exemplary electrochemical cell 100a operating in a charging mode according to one or more embodiments is shown. The components of the electrochemical cell 100a may be similar to those described herein with respect to Figure 2 The electrochemical cell 100 described is similar to those described above. Figure 3AAs shown, according to certain embodiments, a power source 140a and wiring 150a are used to apply a potential difference across the electrochemical cell 100a. According to certain embodiments, this results in an electron flow 160a in the external circuit 150a, directing the electrons to the main electroactive composite layer 114a of each negative electrode 110a. In some embodiments, a redox half-cell reaction occurs at the electroactive composite layer 114a to reduce the first electroactive material fixed in the layer 114a. According to certain embodiments, in its reduced state, the electroactive material exhibits an increased affinity for a target gas (not shown) in a gas mixture. The target gas of the gas flow can penetrate the gas permeable layer 112a of the negative electrode to bond with the reduced material of the composite layer 114a.

[0117] In some embodiments, during the processes described herein, relatively large amounts of the target gas are removed from the gas mixture. In some cases, removing relatively large amounts of the target gas can be advantageous for any of a variety of applications, such as capturing gases that may be harmful if released into the atmosphere for environmental reasons. As an example, in some embodiments, the target gas includes carbon dioxide, and removing relatively large amounts of carbon dioxide from the gas mixture can be advantageous for limiting the greenhouse gas impact of a process (e.g., an industrial process or a transportation process) or even reducing the amount of carbon dioxide in a room or atmosphere (whether for thermodynamic reasons for heating and air conditioning processes or for environmental reasons).

[0118] In some embodiments, the amount of target gas in the treated gas mixture (e.g., a gas mixture from which a certain amount of target gas is removed when exposed to the electrochemical cell) is less than or equal to 50%, less than or equal to 25%, less than or equal to 10%, less than or equal to 5%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.5%, less than or equal to 0.1%, or less of the amount of target gas in the original gas mixture before treatment (measured as a percentage by volume) (e.g., the amount of target in the gas mixture before exposure to the electrochemical cell). In some embodiments, the amount of target gas in the treated gas mixture is greater than or equal to 0.001%, greater than 0.005%, greater than or equal to 0.01%, greater than or equal to 0.05%, greater than or equal to 0.1%, greater than or equal to 0.5%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, or more of the amount of target gas in the original gas mixture before treatment (measured as a percentage by volume).

[0119] In some embodiments, the amount of target gas in the treated gas mixture (e.g., a gas mixture from which a certain amount of target gas is removed when exposed to the electrochemical cell) is less than or equal to 50%, less than or equal to 25%, less than or equal to 10%, less than or equal to 5%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.5%, less than or equal to 0.1%, or less of the amount of target gas in the original gas mixture before separation (e.g., the amount of target in the gas mixture before exposure to the electrochemical cell). In some embodiments, the amount of target gas and the treated gas mixture is greater than or equal to 0.001%, greater than 0.005%, greater than or equal to 0.01%, greater than or equal to 0.05%, greater than or equal to 0.1%, greater than or equal to 0.5%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, or more of the amount of target gas in the original gas mixture before treatment (in mole percentage).

[0120] In some embodiments, the methods described herein can be used to remove a certain amount of a target gas from a gas mixture (e.g., during and / or after applying a potential across an electrochemical cell) while removing a relatively small amount of any oxygen (O2) that may be present in the gas mixture. In some such cases, this is beneficial because reactivity with oxygen can be detrimental to the performance of the systems and methods (e.g., reduced capture efficiency, damage to components of the electrochemical cell, etc.). Any of the many features described herein (alone or in combination) can contribute to the ability to remove a certain amount of a target gas from a gas mixture while removing a relatively small amount of any oxygen that may be present in the gas mixture. For example, using a first electroactive material having a reduced state in the negative electrode (in which the material is capable of bonding with the target gas, but for which the reactivity with oxygen is thermodynamically unfavorable) can allow for the removal of a relatively large amount of the target gas, allowing for little or no removal of oxygen.

[0121] One non-limiting way in which the target gas can be removed while removing little or no oxygen from the gas mixture is by applying a potential across the electrochemical cell during at least a portion of the operation. For example, it has been found in the context of the present disclosure that a potential (e.g., a first potential) sufficient to reduce a first electroactive substance to at least one reduced state (at which the substance is capable of reacting with the target gas) can be applied across the electrochemical cell, but the potential is insufficient to achieve a state in which the substance (or the electrode itself) is capable of reacting with oxygen (e.g., to form superoxide ions or peroxide divalent anions). Judicious selection of the first electroactive substance can allow such a potential to be applied, whereas certain conventional electroactive substances may not allow such a potential to be applied. The potential applied across the electrochemical cell can be such that the electrode potential at the negative electrode is positive (e.g., greater than or equal to 10 mV, greater than or equal to 50 mV, greater than or equal to 100 mV, greater than or equal to 200 mV, greater than or equal to 5 mV, and / or up to 1 V or more) relative to the standard reduction potential for the interconversion of oxygen and superoxide ions, or superoxide ions and peroxide ions.

[0122] In some embodiments, an amount of the target gas (e.g., CO2) is removed from the gas mixture during and / or after application of the potential difference, and less than or equal to 0.1%, less than or equal to 0.05%, less than or equal to 0.001%, and or as low as 0.0001%, as low as 0.00001%, or less (in % by volume) of any oxygen present in the gas mixture is removed from the gas mixture. In some embodiments, an amount of the target gas is removed from the gas mixture during and / or after application of the potential difference, and no oxygen is removed from the gas mixture (e.g., during removal of the target gas). These ranges of oxygen removal from the gas mixture can be achievable even when oxygen is present in the gas mixture in relatively high amounts (e.g., greater than or equal to 0 vol%, greater than or equal to 1 vol%, greater than or equal to 5 vol%, greater than or equal to 10 vol%, greater than or equal to 21 vol%, greater than or equal to 50 vol%, and / or up to 75 vol%, up to 90 vol%, up to 99 vol%, substantially 100 vol%, or more).

[0123] In some but not necessarily all cases, when oxygen is present in the gas mixture, an amount of oxygen is removed from the gas mixture during at least a portion of the time during which an amount of target gas is removed from the gas mixture (e.g., during and / or after application of the electrochemical potential). In some such embodiments, the ratio of the amount of target gas removed to the amount of oxygen removed is greater than or equal to relatively high. The ratio may be relatively high in the case where the reaction between the electroactive species in at least one reduced state formed during and / or after application of the potential across the electrodes and the target gas (e.g., CO2) is thermodynamically more favorable than the reaction of the species with oxygen. In some embodiments, the ratio of the amount of target gas removed to the amount of oxygen removed is greater than or equal to 10:1, greater than or equal to 100:1, greater than or equal to 1,000:1, greater than or equal to 10,000:1, and / or up to 100,000:1, up to 1,000,000, up to 10,000,000:1, up to 100,000:1, up to 1,000,000,000:1, or more.

[0124] In some embodiments, the positive electrode (e.g., Figure 3A The positive electrode 120a in is used as an electron source during operation in the charging mode. Figure 3A In the embodiment, according to certain embodiments, a corresponding redox half-cell reaction occurs at the complementary electroactive composite layer 124a of the positive electrode 120a to oxidize its electroactive substance. The oxidation reaction can release electrons from the complementary electroactive substance (e.g., polyvinyl ferrocene). According to certain embodiments, these electronic reaction products can then travel through the substrate layer 122a and / or the external wiring 150a to complete the circuit. According to certain embodiments, the separator 130a separates the positive electrode 120a and the negative electrode 110a.

[0125] According to one or more embodiments, the operation of the electrochemical cell further comprises: applying a second potential difference across the electrochemical cell to release the target gas bonded to the first electroactive substance. In some embodiments, the release of the target gas produces a product or a treated gas mixture (e.g., a gas mixture rich in target gas, such as a gas stream rich in target gas) having a higher concentration of target gas than the original gas mixture exposed to the electrochemical cell. According to some embodiments, after operating the electrochemical cell in a charging mode (during which the target gas is bonded to the first electroactive substance of the negative electrode) for a period of time, the operation can be switched to a discharge mode. During operation in the discharge mode, the applied voltage is switched to provide an electron flow in the opposite direction to the electron flow during the charging mode. When operating in the discharge mode, a negative voltage can be applied across the electrochemical cell. In the discharge mode, a redox half reaction occurs at the negative electrode, wherein the first electroactive substance of the negative electrode is oxidized. During operation in the discharge mode, the target gas can be released from the electroactive substance bonded thereto in the negative electrode.

[0126] According to some embodiments wherein the electroactive material of the negative electrode is an optionally substituted quinone, the electroactive material is oxidized during the discharge mode according to the following reaction (4):

[0127]

[0128] According to some embodiments in which the electroactive species is oxidized after bonding with a target gas comprising carbon dioxide, the following reaction (5) may occur:

[0129]

[0130] According to some embodiments, when the first electroactive material (eg, including an optionally substituted quinone) is oxidized at the negative electrode, the second electroactive material (eg, polyvinylferrocene) is reduced as the positive electrode. During the discharge mode, the reduction of the second electroactive material acts as an electron sink.

[0131] According to some embodiments wherein the electroactive material of the positive electrode comprises polyvinylferrocene, the second electroactive material is reduced according to the following reaction (6):

[0132]

[0133] Although each of reactions (4) through (6) are shown to occur in one direction, some reversibility may be exhibited. Similar reactions may occur using different species, as will be appreciated by one of ordinary skill in the art with the benefit of this disclosure.

[0134] According to some such embodiments, when the polarization of the external circuit is changed to allow electrons to flow in the opposite direction compared to the charging process, the electroactive material of the negative electrode is oxidized by discharging the electrochemical cell. According to certain embodiments, the covalent bond formed between the optionally substituted quinone and the CO2 molecule is broken (as shown in reaction (5)), thereby releasing the CO2 gas to diffuse out of the negative electrode, and the electrons flowing to the positive electrode to oxidize the Fc + The unit is reduced to Fc (as shown in reaction (6)). According to some such embodiments, polyvinylferrocene can be used as an electron source for the reduction of an optionally substituted quinone or an electron sink for the oxidation of a carbon dioxide adduct of an optionally substituted quinone.

[0135] During the discharge mode, the potential difference across the electrochemical cell can have a specific voltage. For example, in some embodiments, the potential difference can be less than 0V, less than or equal to -0.5V, less than or equal to -1.0V, or less than or equal to -1.5V. In some embodiments, the potential difference can be at least -2.0V, at least -1.5V, at least -1.0V, or at least -0.5V. Combinations of these voltages are also possible, such as at least -2.0V and less than or equal to -0.5V. Other values ​​are also possible.

[0136] Figure 3B An exploded view of an exemplary electrochemical cell 100b operating in a discharge mode according to one or more embodiments is shown. According to certain embodiments, the components of the electrochemical cell 100b are Figure 3A However, according to some embodiments, the voltage applied by the power source 140b has been changed to produce a direction that causes the electron flow 160b through the external wiring 150b to be opposite to that of the battery 100a. Figure 3AThe potential difference that reverses the direction of the electron flow 160a in the positive electrode 120b. According to some embodiments, in the discharge mode, a redox half-cell reaction occurs at the electroactive composite layer 114b of the negative electrode 110b to oxidize the first electroactive substance fixed in the layer 114b. In some embodiments, the first electroactive substance exhibits a reduced affinity for the target gas in its oxidized state, resulting in the release of the target gas from the electroactive material. The released target gas can leave through the gas permeable layer 112b and can be directed toward further processing, collection, or other desired destinations. At the same time, in some embodiments, the positive electrode 120b is used as an electron sink during operation in the discharge mode. According to some embodiments, a half-cell reaction occurs at the complementary electroactive composite layer 124b of the positive electrode 120b to reduce the second electroactive substance. In some embodiments, during the reduction reaction, the electrons that have traveled through the wiring 150b and the base layer 122b are bonded to the complementary electroactive substance, making the circuit complete. According to some but not necessarily all embodiments, separator 130b separates positive electrode 120b from negative electrode 110b.

[0137] According to one or more embodiments, one or more electrochemical cells as described herein may be incorporated into a gas separation system. According to any of the embodiments described herein, the gas separation system may include a plurality of electrochemical cells in fluid communication with a gas inlet and a gas outlet.

[0138] The gas separation system may include an external circuit connecting the negative electrode (or the first negative electrode and the second negative electrode when both are present) and the positive electrode of each electrochemical cell to a power source configured to apply a potential difference across the negative electrode and the positive electrode of each electrochemical cell.

[0139] Figure 4 Schematic diagram of an exemplary gas separation system 400 according to one or more embodiments is shown. According to certain embodiments, system 400 includes a housing 460 having an inlet 470 and an outlet 480. Located within the housing is an electrochemical cell 405. Although not shown for clarity in FIG. Figure 4Only one battery 405 is shown in the figure, but it will be readily understood that a plurality of batteries 405 may be located in the housing 460. According to certain embodiments, a power source 440, which may be located inside or outside the housing 460, is connected to the battery 405. According to certain embodiments, the negative electrode 410 is connected to the power source 440 via wiring 450a, and the positive electrode is connected via wiring 450b. When a voltage is applied to operate the battery in a charging mode, a gas mixture to be at least partially separated (e.g., a gas stream, such as ventilation air or ambient air) is delivered through the inlet 470 as described elsewhere herein. In some embodiments, the gas mixture includes a target gas designed to be at least partially removed by the system 400. The gas mixture is then passed near the battery 405, particularly near the negative electrode 410. In some embodiments, a first electroactive substance in at least one of its reduced states in the negative electrode 410 bonds to the target gas, removing at least a portion of the target gas from the gas mixture. According to certain embodiments, an optional second negative electrode 410, a second separator 420, and corresponding wiring 450a are shown in dashed lines. Although Figure 4 The embodiments shown in and other figures include an optional enclosure, but it should be understood that the electrochemical cell may be located in a variety of environments, such as in-line in a conduit, or without an enclosure in other situations.

[0140] Figure 5A A schematic diagram of an exemplary system for performing a gas separation process during a charging mode according to one or more embodiments is shown. Figure 5A In some embodiments, a potential difference is applied across each electrochemical cell so that each electrochemical cell operates in a charging mode. According to some embodiments, in the charging mode, the redox reaction (e.g., reduction) of the first electroactive substance in the negative electrode 510 increases the affinity between the electroactive substance and the target gas 590. A gas mixture 575 containing the target gas 590 is introduced into the system and passed near the negative electrode 510. According to some embodiments, the increased affinity causes the target gas (e.g., CO2) to bond with the electroactive material. In this way, at least a portion of the target gas is separated from the gas mixture 575 to produce a treated gas mixture 585.

[0141] In some embodiments, the gas separation system includes a plurality of electrochemical cells, and the flow field is between at least some (e.g., some or all) of the plurality of electrochemical cells. As an illustrative example, Figure 5BA schematic diagram of an exemplary system according to one or more embodiments is shown, the system including a flow field 511 separating electrochemical cells 500, the electrochemical cells 500 performing a gas separation process during a charging mode. It should be understood that when a first object is between a second object and a third object, it can be between the entirety of the first object and the second object, or between a portion of the first object and the second object. In some embodiments, the flow field between two adjacent electrochemical cells is directly adjacent to each adjacent electrochemical cell, so that there is no intermediate structure / layer between the flow field and the electrochemical cell. However, in some embodiments, the flow field between two adjacent electrochemical cells is indirectly adjacent to one or both batteries, so that there are one or more intermediate structures / layers, such as conductive solids.

[0142] Flow field generally refers to a solid structure configured to limit the path through which a fluid can flow. In some cases, flow field includes a hole or channel that is limited for fluid flow and allows fluid to be exposed to a solid product of adjacent structures. Suitable materials for the solid product of flow field include but are not limited to polymer materials (such as plastics), metals / metal alloys, graphite, composite materials (such as graphite-polymer composite materials). In some embodiments, flow field includes a solid product comprising one or more surfaces with patterned channels. Channel patterns can be selected to effectively distribute fluid (such as, gas) across one or more dimensions of flow field. Suitable channel patterns include but are not limited to serpentine, parallel and interdigitated. Figure 5C , 5D 5E shows a schematic side view of a flow field 511a with a serpentine pattern, a flow field 511b with a parallel pattern, and a flow field 511c with an interdigitated pattern, each with a fluid flow direction as shown by an arrow, according to certain embodiments. The flow field channel pattern can be formed, for example, by etching, cutting, stamping, molding, grinding, or additive manufacturing. In some embodiments, the flow field includes a porous solid. For example, the flow field can include carbon fiber paper, felt, or cloth, or metal foam.

[0143] exist Figure 5B, gas 590 from fluid mixture 575 is distributed along the face area of ​​electrode 510 via flow field 511 (e.g., via channels not shown). It has been recognized in the context of the present disclosure that flow fields can help distribute the gas mixture relatively evenly on the electrode and can help control the duration of gas exposure to the electrode (e.g., to promote efficient capture of the target gas). By utilizing a larger percentage of the electrode area (e.g., including electroactive materials in at least one reduced state) to bind the target gas, the relatively uniform distribution of the gas can improve efficiency. In some embodiments, during at least a portion of the charging process, at least 25%, at least 50%, at least 75%, at least 90%, at least 95%, or more of the flow rate of the gas mixture across the negative electrode face area in the system is within 50%, within 25%, within 15%, within 10%, within 5%, within 2%, within 1%, or less of the average flow rate across the entire negative electrode face area during the charging process.

[0144] According to some embodiments, by changing the voltage applied from the power source 440 to induce electron flow in the opposite direction to the flow in the charging mode, Figure 4 The system 400 shown in FIG. 4 can also be operated in a discharge mode. This change causes a different redox reaction to occur at the negative electrode 410, for example, a redox reaction in which the first electroactive material of the negative electrode is oxidized. Such a change in the oxidation state of the electroactive material can cause the target gas to be released from the electroactive material to produce a treated gas mixture having a higher amount of the target gas than the original gas mixture (e.g., the input gas mixture). The treated gas mixture can exit through the outlet 480 or an alternative outlet (not shown).

[0145] In some, but not necessarily all, embodiments, because operation in the discharge mode causes the target gas material to be released, simultaneously introducing a gas stream to be subjected to at least partial gas separation through inlet 470 will have the opposite effect. Thus, during operation in the discharge mode, inlet 470 is closed, or a different stream (e.g., a waste stream) is redirected to the inlet. However, in certain embodiments, a second portion of the gas mixture to be subjected to at least partial gas separation is introduced via inlet 470 while operation in the discharge mode occurs.

[0146] According to some but not necessarily all embodiments, the gas separation system includes a first electrochemical battery group and a second electrochemical battery group. Each of the first group and the second group may include one or more electrochemical cells as described throughout the present disclosure. The first group and the second group may be operated in parallel in an alternating manner so that one battery group operates in a charging mode and captures a target gas (e.g., CO2) from a gas mixture, while the other battery group operates in a discharge mode and releases the target gas (e.g., CO2). The system may include a separate cover for each of the electrochemical batteries. The system may also include a conduit and a valve arranged to guide the fluid in a desired manner. At a given moment, in the case where the gas mixture is directed to a battery group operating in a charging / capture mode, the gas separation system may allow for continuous or semi-continuous separation of a gas mixture (e.g., a gas stream), and a separate treated mixture of rich target gas is produced by another battery group operating in a discharge / release mode. In addition, according to the needs of the application, additional electrochemical batteries may be added in parallel or in series.

[0147] Figure 6 An example of an embodiment of such a gas separation system is shown. In the gas separation system 600, the first electrochemical battery group 605a is located in the first cover 660a, and the second electrochemical battery group 605b is located in the second cover 660b. A conduit connects the gas inlet 670 with the cover inlets 672a and 672b. The valve 684 can be arranged to direct the fluid to either of the groups 605a and 605b, depending on which group is currently running in the charging mode.

[0148] In operation, a gas stream containing a target gas (e.g., CO2) can be introduced into the gas separation system 600 through the inlet 670. According to certain embodiments, when the first battery pack 605a is operated in a charging / capture mode, the valve 684 can be arranged to direct the flow so that it is close to the first battery pack 605a, where the target gas can be bonded with the electroactive material in the battery 605a to produce a treated gas mixture (a treated gas mixture with a reduced concentration of the target gas) and then exit the hood 660a through the outlet 673a. An additional valve 686a downstream of the hood outlet 673a can be arranged to direct the treated gas stream through the treated gas outlet 680.

[0149] When the first battery pack 605a is operated in a charging mode, the second battery pack 605b can be operated in a discharge mode, wherein the previously accumulated target gas is released from the electroactive material of the second battery pack 605b. In the illustrated embodiment, valve 684 is arranged to separate the gas mixture from the battery pack 605b operating in the discharge mode. The release of the target gas from the battery pack 605b produces a gas mixture rich in target gas, which then leaves the cover 660b through the outlet 673b. Valve 686b can be arranged to separate the gas mixture rich in target gas from the treated flow outlet 680 and direct the flow of the rich target gas to the waste outlet 682b, where the flow of the rich target can be further processed, stored, etc.

[0150] After a period of operation in the above manner, the modes of cells 605a and 605b can be interchanged. The first cell group 605b then operates in a discharge mode to release the accumulated target gas from its electrodes. During this period, valve 684 is rearranged to isolate the process flow from the first cell group 605a. During this period, valve 686a is rearranged to direct the target-rich flow toward the waste outlet 682a.

[0151] At the same time, the operation of the second battery pack 605b is reversed so that they operate in a charging mode to capture the target gas and produce a processed flow. The inlet valve 684 is arranged to direct the process gas mixture from the system inlet 670 to the second battery pack 605b via the second hood inlet 672b through a conduit. The outlet valve 686b is rearranged to direct the processed gas mixture to the outlet 680.

[0152] According to certain embodiments, in this manner, the different battery packs 605a and 605b can be cycled through the modes while together providing continuous or semi-continuous separation of the gas stream containing the target gas. Figure 6 The specific embodiment shown in shows one particular arrangement of system components (e.g., valves, conduits, inlets and outlets), but it will be appreciated that different configurations may be provided to still meet the goal of providing continuous operation with separate flows of treated and target gas-rich streams.

[0153] Fig. 7A shows a similar Figure 6Schematic diagram of an exemplary system of a system that performs a gas separation process in which a first battery pack 705a operates in a charging mode and a second battery pack 705b operates in a discharge mode. In the charging mode, the applied voltage causes a redox reaction (e.g., reduction) of the electroactive material in the negative electrode 710a, which increases the affinity between the first electroactive material and the target gas 790. A gas stream 575 containing the target gas 590 is introduced into the battery pack 705a and passes near the negative electrode 510a. The increased affinity causes the target gas (e.g., CO2) 790 to bond with the electroactive material. In this way, at least a portion of the target gas is separated from the gas stream 775 to produce a treated gas stream 785.

[0154] According to certain embodiments, in the discharge mode, the second applied voltage causes an electron flow in the opposite direction to the electron flow during the charge mode, causing a second redox reaction (e.g., oxidation) of the first electroactive material in the negative electrode 710b, which reduces the affinity between the electroactive material and the target gas 790. The released target gas 790 enters the target gas-rich gas mixture 787.

[0155] Figure 7B Shows something like Figure 6 A schematic diagram of an exemplary system of a system in which Fig. 7A The gas separation process shown and described is a process in which the mode of operation is reversed. Figure 7B In some embodiments, the voltage applied across the first battery group 705a has been changed and the battery 705a operates in a discharge mode to release the stored target gas 790 from the negative electrode 710a to produce a target gas-rich gas mixture. At the same time, the voltage applied across the second battery group 705b has also been changed, causing them to operate in a charge mode. The target gas 790 of the process stream 775 is bonded to the negative electrode 710b to produce a processed stream 785.

[0156] As described above, the gas separation system may include a plurality of electrochemical cells electrically connected in parallel or in series.Benefiting from the present disclosure, those of ordinary skill in the art will generally understand how to electrically connect electrochemical cells to form a circuit.Such a connection can be achieved by establishing a conductive path for electrons to flow between the electrodes of the electrochemical cell (in other words, establishing an electrical coupling between the electrodes).In some cases, the conductive path can be established by one or more conductive solid materials (e.g., conductive metals, alloys, polymers, composite materials, carbonaceous materials, or combinations thereof).For example, the conductive path can be established by wiring the electrodes of the electrochemical cell.The electrochemical cell may have any one of the above configurations.For example, in some embodiments, some or all of the electrochemical cells in the system have a single negative electrode (e.g., comprising a first electroactive substance), a single positive electrode (e.g., comprising a second electroactive substance) and an optional separator between the first positive electrode and the second positive electrode. Fig. 10A A schematic diagram of an arrangement of electrochemical cells 1100 in one such system 1000 is shown, wherein each electrochemical cell 1100 sequentially includes a negative electrode 1010, an optional separator 1020, and a positive electrode 1030. A gas mixture 1075 containing a target gas may be introduced into the system such that the gas mixture 1075 passes near the negative electrode 1010 of a first electrochemical cell 110 and the positive electrode 1030 of an adjacent second electrochemical cell 1100. Although Fig. 10A Three electrochemical cells 1100 are shown, but it will be appreciated that any suitable number of electrochemical cells may be employed in a gas separation system (eg, electrically connected in parallel or in series), depending on the requirements of the particular application desired.

[0157] In other embodiments, some or all of the electrochemical cells in the gas separation system include a positive electrode (e.g., comprising a second electroactive material), a first negative electrode (e.g., comprising a first electroactive material), a second negative electrode (e.g., comprising a first electroactive material), a first separator between the first negative electrode and the positive electrode, and a second separator between the positive electrode and the second negative electrode. Examples of such electrochemical cells are shown in Figure 1B and Figure 2 middle.

[0158] Fig. 10B Schematic diagram of a configuration in which a plurality of electrochemical cells 1100 are electrically connected in parallel in a system 1000 according to certain embodiments. In the parallel configuration, each negative electrode 1010 is electrically coupled to a first terminal (e.g., of a power source), and each positive electrode 1030 is electrically coupled to a second terminal (e.g., of a power source). Fig. 10BIn some embodiments, each negative electrode 1010 is electrically coupled to a first terminal of a power source via a wiring 115 , and each positive electrode 1030 is electrically coupled to a second terminal of the power source via a wiring 116 .

[0159] Fig. 10C Schematic diagram of a configuration in which a plurality of electrochemical cells 11000 are electrically connected in series in a system 1000 according to certain embodiments. In the series configuration, the positive electrode of a first electrochemical cell of the system is electrically connected to the negative electrode of a second electrochemical cell. For example, Fig. 10B In the embodiment, according to some embodiments, the negative electrode 1010 of the first electrochemical cell 1100a is electrically connected to the positive electrode 1030 of the second electrochemical cell 1100b through the wiring 1017, and the negative electrode 1010 of the second electrochemical cell 1100b is electrically connected to the positive electrode 1030 of the third electrochemical cell 1100c through the wiring 1018. In addition, according to some embodiments, the positive electrode 1030 of the first electrochemical cell 1100a is electrically coupled to the first terminal of the power source through the wiring 114, and the negative electrode 1030 of the third electrochemical cell 1100a is electrically coupled to the second terminal of the power source through the wiring 119.

[0160] It has been determined in the context of the present disclosure that certain configurations of a gas separation system including a plurality of electrochemical cells electrically connected in series can promote relatively efficient charge transfer / and / or gas transfer. For example, in some embodiments, the conductive material between the electrochemical cells can establish a conductive path instead of using external wiring. For example, the gas separation system may include a first electrochemical cell and a second electrochemical cell electrically connected in series, wherein the electrical connection is established by one or more conductive materials between the first electrochemical cell and the second electrochemical cell. Any of a variety of suitable conductive materials may be located between the electrochemical cells to establish an electrical connection between, for example, the negative electrode of the first electrochemical cell and the positive electrode of the second electrochemical cell. For example, the conductive material may be a conductive solid. Conductive solids may include, for example, metals and / or metal alloys (e.g., steel, silver metal / alloys, copper metal / alloys, aluminum metal / alloys, titanium metal / alloys, nickel metal / alloys). In some embodiments, the conductive solid comprises a carbonaceous material (e.g., graphite, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, carbon mats (e.g., carbon nanotube mats), Ketjen black, carbon black Super P, graphene, etc.). In some embodiments, the carbonaceous material is a porous carbonaceous material as described elsewhere herein. In some embodiments, the conductive solid comprises a composite material of a conductive solid and a binder resin. In some embodiments, the conductive solid between the electrochemical cells comprises a conductive polymer material.

[0161] In some but not necessarily all embodiments, the conductive material between the electrochemical cells comprises a bipolar plate. It should be understood that in the context of the present disclosure, the plate need not necessarily be flat. Bipolar plates are known to those skilled in the art and are commonly used in fields other than gas separation, such as fuel cells. The bipolar plate can be configured to separate the fluid (e.g., gas) contacting the positive electrode from the fluid contacting the negative electrode. The bipolar plate can include a conductive solid, such as steel, titanium, or graphite.

[0162] In some embodiments, at least some of the plurality of electrochemical cells (e.g., connected in series) are separated by flow fields. As described above, positioning the flow field between adjacent electrochemical cells can promote beneficial gas distribution and relatively efficient interaction between the gas and the electrode (e.g., for bonding). In some embodiments, the bipolar plate described above includes a flow field (e.g., by etching a fluid passage in one or both faces of the plate), however, in other embodiments a different flow field is used as an alternative or supplement to the bipolar plate including the flow field.

[0163] Fig.11 1 shows a schematic diagram of an exemplary gas separation system 1000 including electrochemical cells 1100 electrically connected in series via one or more conductive materials between the cells, according to certain embodiments. Fig.11 In the embodiment of the present invention, the system 1000 includes a conductive solid material in the form of a bipolar plate 1012 and a rib 1014. The ribs in the gas separation system can be made of any of the conductive solid materials described above. Fig.11 In the embodiment shown in , the first electrochemical cell 1100a is separated from the second electrochemical cell 1100b by the bipolar plate 1012 and the rib 1014. The bipolar plate 1012 and the rib 1014 can be directly adjacent to the negative electrode 1010 of the first electrochemical cell 1100a and the positive electrode 1030 of the second electrochemical cell 1100b, thereby establishing a conductive path for series connection. Other electrochemical cells in the system can be similarly electrically connected. Although Fig.11 Bipolar plates and ribs are shown, but such depiction is non-limiting and other configurations (eg, no bipolar plates, no ribs, etc.) are possible. Fig.11 Also shown is an optional flow field 1011 separating electrochemical cells 1100 according to certain embodiments. In some embodiments, one or more components (e.g., conductive solids such as ribs) can establish a channel between the negative electrode and the positive electrode of adjacent electrochemical cells. For example, Fig.11The ribs 1014 in the flow field 1011 can have dimensions such that the channels 1013 establish pathways for gas (e.g., gas mixture) to flow between the electrochemical cells 1011 and interact with the electrodes. For example, according to certain embodiments, the gas mixture 1075 can pass through the channels 1013, through the flow field 1011, and between the first electrochemical cell 1100a and the second electrochemical cell 1100b.

[0164] Compared to other configurations, the flow of current in certain embodiments described above may encounter less resistance. For example, in some embodiments where the electrochemical cells are connected in series by conductive materials between at least some of the electrochemical cell stacks, the current may flow in a direction perpendicular to the stack. Fig.11 One such example is shown, where the current can flow in a direction x perpendicular to the electrochemical cell 1100, while the gas mixture 1075 can flow in a direction parallel to the electrochemical cell 1100. Fig.11 In the embodiment, the path through which the current travels is relatively short and is determined by the thickness of the bipolar plate 1012 and the rib 1014. In some embodiments, the thickness of one or more conductive solids between the electrochemical cells is less than or equal to 10 mm, less than or equal to 5 mm, less than or equal to 2 mm, less than or equal to 1 mm, and / or as low as 0.5 mm, as low as 0.2 mm, as low as 0.1 mm, or lower. In contrast, in embodiments in which the electrochemical cells are electrically connected in parallel or in series by external wiring, the current must flow through the entire height and / or length of the electrode (e.g., the current collector of the electrode) and flow through the electrode tab to reach the external wiring. Such a height and / or length can be, for example, at least 1 cm, at least 2 cm, at least 5 cm, at least 10 cm, and / or up to 20 cm, up to 50 cm, up to 100 cm, or higher. In such an embodiment, the greater distance that the current travels generally results in a greater total cell resistance, which may reduce the charge transport and / or energy efficiency of the method for at least partial gas separation described herein.

[0165] The electrochemical cells, systems, and methods described herein can be implemented in a variety of applications. The number of electrochemical cells or battery packs can be adjusted in proportion to the requirements of the specific application required. In some embodiments, the systems and methods described herein can be used to remove CO2 from ambient air and enclosed spaces such as closed buildings, car compartments - reducing the heating cost of incoming air for ventilation - and submarines and space capsules, where the increase in CO2 levels may be catastrophic. In embodiments involving the power industry, they can be used to capture different concentrations of post-combustion carbon dioxide. In some embodiments, the systems and methods are suitable for separating target gases from industrial flue gases. In addition, they can be used to capture sulfur dioxide and other gases from flue gases. In embodiments involving the oil and gas industry, the disclosed systems and methods can be used to capture carbon dioxide and other gases from different processes and transfer them for downstream compression and / or processing. The disclosed systems and methods can be used to capture carbon dioxide from natural gas burned for heating greenhouses in mild and cold climates, and then transfer the captured carbon dioxide to the greenhouse for plants to use in photosynthesis, i.e., feed plants.

[0166] In some embodiments, the gas separation systems described herein can capture a target gas at a relatively high productivity. The productivity of a gas separation system in capturing a target gas from a gas mixture, at a given gas flow rate through the gas separation system, generally refers to the ratio of the target gas captured during the gas capture process (measured in mass and referred to herein as kg 目标气体 ) divided by the mass of the bed in the gas separation system (referred to herein as kg bed) and the breakthrough time (referred to as t b ). The bed of a gas separation system generally refers to the absorbent material of the gas separation system, such as a layer of electroactive material (e.g., a primary electroactive composite layer) of an electrochemical cell described herein. One of ordinary skill in the art will understand that the breakthrough time of a gas separation system generally refers to the time required for an electrode to reach saturation or for the outlet target gas concentration to begin to increase as a gas mixture flows through the system during the capture process. In situations where a gas separation system is desired to operate at high efficiency, relatively high productivity can be expected even if the gas separation system is relatively small (e.g., a total volume of less than or equal to 1,000 cubic feet (ft 3), less than or equal to 500 cubic feet, less than or equal to 200 cubic feet, less than or equal to 100 cubic feet, less than or equal to 50 cubic feet, less than or equal to 25 cubic feet, less than or equal to 10 cubic feet, and / or as low as 5 cubic feet, as low as 2 cubic feet, as low as 1 cubic foot, as low as 0.1 cubic foot, or less). Some such small gas separation systems can be particularly useful for ventilation systems or systems for direct air capture. One or more features described herein can contribute to the relatively high productivity of the gas separation system, such as the use of specific electroactive materials, the use of porous electrodes, and the use of an electrochemical cell having a first negative electrode, a second negative electrode, and a positive electrode between the first negative electrode and the second negative electrode).

[0167] In some embodiments, the gas separation system is configured to have a gas flow rate greater than or equal to 0.003 kg at a gas flow rate greater than or equal to 0.001 L / sec and less than or equal to 500 L / sec. 目标气体 / (kg 床 t b ), greater than or equal to 0.005kg 目标气体 / (kg 床 t b ), greater than or equal to 0.01kg 目标气体 / (kg 床 t b ), greater than or equal to 0.02kg 目标气体 / (kg 床 t b ), greater than or equal to 0.03kg 目标气体 / (kg 床 t b ), or greater productivity for capturing target gas (e.g., CO2). In some embodiments, the gas separation system is configured to have a gas flow rate of less than or equal to 0.05 kg at a gas flow rate of greater than or equal to 0.001 L / sec and less than or equal to 500 L / sec. 目标气体 / (kg 床 t b ), less than or equal to 0.04kg 目标气体 / (kg 床 t b ), less than or equal to 0.03kg 目标气体 / (kg 床 t b ), less than or equal to 0.02kg 目标气体 / (kg 床 t b ), less than or equal to 0.015kg 目标气体 / (kg 床 t b), or less, for capturing a target gas (e.g., CO2). In some cases, due to the contribution of certain features described herein, the gas separation system is able to have these ranges of productivity even in the case of a gas mixture containing a relatively low concentration of the target gas and or in the case of a gas mixture containing a potential interfering gas such as oxygen. It should be understood that although the gas separation system can be configured to achieve the above productivity when operating within the flow range, in some cases, the gas separation system can operate at a flow rate other than the indicated flow rate, provided that the indicated productivity is achieved under such the same configuration (e.g., electrochemical cell type, size, arrangement). In some embodiments, the flow rate described herein refers to the gas flow rate per negative electrode surface area. For example, in some embodiments, the flow rate described herein refers to per 100cm 2 In this case, the negative electrode surface area can be the sum of the surface areas of multiple negative electrodes in multiple electrochemical cells and multiple electrochemical cell stacks in the system. In some embodiments, the flow rate described herein refers to the airflow rate per electrochemical cell stack in the system. For example, in some embodiments, the flow rate described herein refers to the airflow rate per 10 electrochemical cells in the system.

[0168] According to one or more embodiments, a gas mixture (e.g., a gas stream, such as an input gas stream) is introduced into a gas separation system at a specific flow rate. In some embodiments, the flow rate is greater than or equal to 0.001 L / sec, greater than or equal to 0.005 L / sec, greater than or equal to 0.01, greater than or equal to 0.05 L / sec, greater than or equal to 0.1 L / sec, greater than or equal to 0.5 L / sec, greater than or equal to 1 L / sec, greater than or equal to 5 L / sec, greater than or equal to 10 L / sec, greater than or equal to 50 L / sec, greater than or equal to 100 L / sec, or greater. In some embodiments, the flow rate of the gas mixture (e.g., gas flow, such as input gas flow) is less than or equal to 500 L / second, less than or equal to 400 L / second, less than or equal to 300 L / second, less than or equal to 200 L / second, less than or equal to 100 L / second, less than or equal to 50 L / second, less than or equal to 10 L / second, less than or equal to 1 L / second, less than or equal to 0.5 L / second, less than or equal to 0.1 L / second, or less. Combinations of these ranges are possible. For example, in some embodiments, the flow rate is greater than or equal to 0.001 L / second and less than or equal to 500 L / second. As described above, in some embodiments, these flow rates are per 100 cm 2 In some embodiments, these flow rates are for every 10 electrochemical cells in the system.

[0169] Certain aspects described herein relate to methods for capturing and releasing a target gas. For example, certain embodiments include capturing a target gas by applying a first potential difference across an electrochemical cell (e.g., electrochemical cell 100) and exposing a first amount of an input gas mixture containing a target gas to the electrochemical cell. The first amount of input gas mixture can be exposed by causing the first amount of input gas mixture to flow through an electrochemical cell (or a gas separation system comprising a plurality of electrochemical cells) as a gas stream, such as shown in Figures 5 to 7B. In some embodiments, during and / or after applying a first potential difference, a portion of the target gas is bonded to the electroactive material of the electrochemical cell to produce a first treated gas mixture. For example, when the first electroactive material is in at least one of its reduced states produced by applying a potential across an electrochemical cell, the target gas (e.g., carbon dioxide) can be bonded to the first electroactive material of the negative electrode of the electrochemical cell. The bonding of the target gas to the electroactive material can result in a treated gas mixture having a lower amount of target gas (as described above with respect to the range of the amount of the target gas removed) than the first gas mixture. Figures 8A to 8B 1 and Example 2 below describe exemplary methods of flowing an input gas mixture and a second gas. It should be understood that in addition to the input gas mixture and the second gas, additional gases may be flowed (e.g., a third gas, a fourth gas, a fifth gas, etc.). The additional gas may flow through the electrochemical system before and / or after the second gas flows.

[0170] In some cases, after at least a portion of the target gas is bonded to the electroactive material, a second potential difference is applied across the electrochemical cell. The second potential difference may be different from the first potential difference. In some embodiments, applying a second potential difference produces a step of partially or completely releasing the target gas bonded to the electroactive material to produce a second treated gas mixture. The second treated gas mixture may have a higher amount of target gas than the input gas mixture. For example, the target gas may be present in the second treated gas mixture in an amount that makes its volume percentage higher than the first amount of gas mixture by 10%, 20%, 50%, 100%, 200%, 1000%, and / or up to 2,000%, 5,000%, 10,000%, or more.

[0171] In some embodiments, during and / or after the release of the target gas from the electroactive material, the method further comprises flowing a second gas through the electrochemical cell to remove at least some or all of the released target gas from the electrochemical cell. In some embodiments, the second gas is different from the input gas mixture. For example, the second gas can be an inert gas. In other cases, the second gas is a substantially pure gas of the target gas (e.g., a purity greater than or equal to 99.9%, greater than 99.99%, greater than or equal to 99.999%, greater than 99.9999%, or higher). For example, the second gas can be substantially pure CO2. As another example, the second gas can include steam.

[0172] An exemplary case in which it may be beneficial to pass a second gas through an electrochemical cell to remove at least part or all of the released target gas from the electrochemical cell is when the amount of captured target gas is greater than the bed volume of the electrochemical cell. In some such cases, more than one bed volume of target gas is bonded to the first electroactive material. For example, in some cases, the volume of target gas captured by the electrochemical cell is equal to at least 1.5 times, at least 2 times, at least 3 times, at least 5 times, at least 10 times, at least 20 times, or more of the bed volume of the electrochemical cell. In some such cases in which the volume of captured target gas is greater than the bed volume of the electrochemical cell, more than one bed volume of target gas is released from the first electroactive material. In these cases, the release of the captured target gas may result in the gas pressure of the electrochemical cell being greater than the ambient gas pressure. In some such cases, the released target gas will then flow out of the electrochemical cell by force of the pressure difference generated with the ambient atmosphere until about 1 bed volume of target gas remains. In order to remove the remaining released target gas, the second gas may be flowed through the electrochemical cell. In some cases, a substantially pure target gas (e.g., CO2) is flowed through to remove the remaining target gas. In other cases, an inert gas (e.g., nitrogen, N2) is flowed through the electrochemical cell to remove the remaining released target gas.

[0173] Another situation in which it can be beneficial for a second gas to flow through an electrochemical cell to remove at least part or all of the released target gas from the electrochemical cell is when the amount of the captured target gas is less than or equal to the bed volume of the electrochemical cell. For example, in some cases, the volume of the target gas captured by the electrochemical cell is less than or equal to 1.0 times, less than or equal to 0.8 times, less than or equal to 0.5 times, less than or equal to 0.3 times, and / or as low as 0.2 times, as low as 0.1 times, as low as 0.01 times, or lower, of the bed volume of the electrochemical cell. In some such cases, the pressure inside the bed of the electrochemical cell will be less than or equal to ambient pressure. In these cases, it can be beneficial to flow the second gas through the electrochemical cell to provide the force required to remove the released target gas from the electrochemical cell. In some such cases, the second gas is a carrier gas. The carrier gas can be any suitable gas that can transport the target gas without reacting with the target gas or the electrochemical cell components. The carrier gas can be easily separated from the target gas by any one of a variety of techniques, which is less costly or less energy intensive as the initial separation of the target gas from the gas mixture. For example, the target gas and the carrier gas can be separated by condensation or flash separation techniques. The carrier gas can flow through the electrochemical cell during the step of releasing the target gas and / or after the step of releasing the target gas. In some cases, the carrier gas is an inert gas. In some cases, the carrier gas is a substantially pure target gas (e.g., substantially pure CO2). In some cases, the carrier gas includes steam. In some embodiments, the second gas (e.g., carrier gas) is the second part of the input gas mixture. For example, in ventilation applications, a certain amount of target gas can be removed from the ventilation air during the application of the first potential across the electrochemical cell, and then during and / or after the release of the target gas, more ventilation air is made to flow through the electrochemical cell to remove the released target gas.

[0174] In some embodiments, during and / or after the step of releasing the target gas, the method also includes applying a vacuum condition to the electrochemical cell to remove at least some or all of the released target gas from the electrochemical cell. With the benefit of this disclosure, a person of ordinary skill will understand suitable techniques and equipment for applying a vacuum condition to the electrochemical cell. For example, a vacuum pump can be connected to the gas outlet fluid of the electrochemical cell. The vacuum pump can be operated to generate a negative pressure difference between the electrochemical cell bed and a downstream position. Such a vacuum condition can provide a force sufficient to cause the target gas released during the above-mentioned release step to flow out of the electrochemical cell. Vacuum conditions can be applied so that the pressure inside the electrochemical cell during and / or after the release of the target gas is less than or equal to 2000 Torr, less than or equal to 1500 Torr, less than or equal to 1200 Torr, less than or equal to 1000 Torr, less than or equal to 900 Torr, less than or equal to 800 Torr, less than or equal to 760 Torr, less than or equal to 700 Torr, less than or equal to 500 Torr, less than or equal to 100 Torr, less than or equal to 50 Torr, less than or equal to 10 Torr, less than or equal to 10 Torr, and / or as low as 5 Torr, as low as 1 Torr, as low as 0.5 Torr, as low as 0.1 Torr, or lower. Vacuum conditions can be applied so that the pressure inside the electrochemical cell during and / or after the release of the target gas is less than the pressure of the environment around the gas separation system including the electrochemical cell. Such an environment can be an environmental condition at sea level on Earth, so that the vacuum condition is established in the electrochemical cell during and / or after the release of the target gas, and the pressure is less than or equal to 760 Torr, less than or equal to 100 Torr, less than or equal to 10 Torr, etc. However, the environment surrounding the gas separation system may be pressurized, such as in some cases where the gas separation system is in a pressurized structure such as a spacecraft (which may be pressurized to 1.2 times the atmospheric pressure at sea level). In some such pressurized environments, vacuum conditions establish a pressure of, for example, 2000 Torr, less than 1000 Torr, etc., within the electrochemical cell during and / or after releasing the target gas.

[0175] In some embodiments of releasing target gas (for example, CO from electrochemical cell), the target gas released can be processed in any one of a variety of ways.For example, the target gas released can be discharged from electrochemical cell (and gas separation system) under the same partial pressure set up when initially released. The target gas released can be discharged into the surrounding environment as waste gas subsequently, or it can be guided (for example, by flowing) for further downstream processing. In some embodiments, the target gas released can be incorporated into the target gas with relatively high partial pressure (for example, greater than or equal to 10 bar, greater than or equal to 20 bar, greater than or equal to 50 bar, greater than or equal to 50 bar, greater than or equal to 75 bar, greater than or equal to 100 bar and / or up to 110 bar, up to 120 bar, up to 150 bar or higher) fluid mixture (for example gas mixture). In some embodiments, the partial pressure of the resulting fluid mixture is greater supercritical (for example, for carbon dioxide, greater than 130 bar). In some cases, incorporation into a fluid mixture can be achieved by merging the released target gas with a fluid mixture already containing the target gas (thereby increasing the partial pressure of the target gas). In some embodiments, the target gas is incorporated into a fluid mixture having a relatively high partial pressure of the target gas by compressing the released target gas. With the benefit of this disclosure, one of ordinary skill in the art will understand how to compress the released target gas (e.g., CO2) discharged from an electrochemical cell, for example, using standard compressor equipment and techniques.

[0176] In some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) has a specific capacity to absorb a target gas (e.g., CO2). For example, in some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) has a specific capacity to absorb a target gas (e.g., CO2). 2 , at least 0.02 mol / m 2 , at least 0.05 mol / m 2 In some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) has an absorption capacity of less than or equal to 0.1 mol / m 2 , less than or equal to 0.08 mol / m 2 , less than or equal to 0.5 mol / m 2 , less than or equal to 0.03 mol / m 2 , or less. Combinations of these ranges are possible. For example, in some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) has at least 0.01 mol / m 2 And less than or equal to 0.1 mol / m 2, or at least 0.01 mol / m 2 And less than or equal to 0.03 mol / m 2 absorption capacity.

[0177] In some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) is capable of absorbing a target gas (e.g., CO2) at a specific rate. For example, in some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) has a gas concentration of at least 0.0001 mol / m 2 / second, at least 0.0002mol / m 2 / second, at least 0.0005mol / m 2 / second, or greater absorption capacity rate. In some embodiments, the negative electrode or a portion thereof (e.g., the electroactive composite layer of the negative electrode (when present)) has less than or equal to 0.001 mol / m 2 / second, less than or equal to 0.0008mol / m 2 / second, less than or equal to 0.0005mol / m 2 / second, or less. In some embodiments, the electroactive composite layer has at least 0.0001 mol / m 2 / second and less than or equal to 0.0005mol / m 2 / second absorption capacity rate. Other absorption capacity rates are also possible.

[0178] In some embodiments, the electroactive composite layer of the negative electrode can have a specific surface area exposed to the gas mixture, such as greater than or equal to 5 cm 2 , greater than or equal to 8cm 2 , greater than or equal to 10cm 2 , and / or up to 10 cm 2 , up to 20cm 2 , up to 50cm high 2 , up to 1m 2 , or greater. Other values ​​are also possible.

[0179] In some embodiments, at least part or all of the electrodes described herein (e.g., negative electrode, positive electrode) comprises a porous material. The porous electrode can be made of any suitable material and / or can include any suitable shape or size. In a non-limiting embodiment, the electrode comprises a porous carbonaceous material. The term carbonaceous material is given in the art with its usual meaning, and refers to a conductive material comprising carbon or graphite. Non-limiting examples of carbonaceous materials include carbon nanotubes, carbon fibers (e.g., carbon nanofibers), and / or graphite. In some such embodiments, the electrode can be partially made of carbonaceous material, or the carbonaceous material can be deposited on the material located below. The material located below generally includes a conductive material, such as a metal and / or metal alloy solid (e.g., steel, copper, aluminum, etc.). Other non-limiting examples of conductive materials are described herein.

[0180] In some embodiments, the electrode (e.g., negative electrode, positive electrode) is porous. The porosity of the electrode can be measured as a percentage or fraction of the void space in the electrode. The porosity percentage of the electrode can be measured using techniques known to those of ordinary skill in the art, such as using volume / density method, water saturation method, water evaporation method, mercury intrusion porosimetry method, and nitrogen adsorption method. In some embodiments, the electrode is at least 10% porous, at least 20% porous, at least 30% porous, at least 40% porous, at least 50% porous, at least 60% porous, at least 70% porous or more. In some embodiments, the electrode is at most 90% porous, at most 85% porous, at most 80% porous, at most 70% porous, at most 50% porous, at most 30% porous, at most 20% porous, at most 10% porous or less. Combinations of these ranges are possible. For example, the electrode can be at least 10% porous and at most 90% porous. The pores can be open pores (e.g., at least a portion of the pores are open to the outer surface of the electrode and / or other pores). In some cases, only a portion of the electrode is porous. For example, in some cases, only a single surface of the electrode is porous. As another example, in some cases, the outer surface of the electrode is porous, while the inner core of the electrode is substantially non-porous (e.g., less than or equal to 20%, less than or equal to 10% porous, less than or equal to 5% porous, less than or equal to 1% or less). In a specific embodiment, the entire electrode is substantially porous.

[0181] In some embodiments, the electrochemical cell has a specific cycle time. The cycle time of an electrochemical cell generally refers to the time period of a charge mode and a discharge mode. The cycle time can be at least 60 seconds, at least 100 seconds, at least 300 seconds, at least 500 seconds, at least 1000 seconds, or longer. In some embodiments, the cycle time is less than or equal to 3600 seconds, less than or equal to 2400 seconds, less than or equal to 1800 seconds or shorter. The combination of these ranges is possible. For example, in some embodiments, the cycle time is at least 60 seconds and less than or equal to 3600 seconds, or at least 300 seconds and less than or equal to 1800 seconds.

[0182] According to some embodiments, the electrochemical cell and its components have a specific thickness, which depends on the desired application (e.g., gas separation of ventilator air, direct air capture, etc.). In some embodiments, the electrochemical cell has a thickness of at least 10 μm, at least 20 μm, at least 50 μm, at least 100 μm, at least 200 μm, at least 300 μm, at least 500 μm, or more. In some embodiments, the electrochemical cell has a thickness of less than or equal to 750 μm, less than or equal to 600 μm, less than or equal to 500 μm, less than or equal to 300 μm, or less. Combinations of these ranges are possible. For example, in some embodiments, the electrochemical cell has a thickness of at least 200 μm and less than or equal to 750 μm. In some embodiments, the electrochemical cell has a thickness of at least 10 μm and less than or equal to 750 μm.

[0183] In some embodiments, the negative electrode or positive electrode has a thickness of at least 0.5 μm, at least 1 μm, at least 2 μm, at least 5 μm, at least 10 μm, at least 20 μm, at least 50 μm, at least 75 μm, at least 100 μm or more. In some embodiments, the negative electrode or positive electrode has a thickness of less than or equal to 200 μm, less than or equal to 150 μm, less than or equal to 100 μm, or less. Combinations of these ranges are possible. For example, in some embodiments, the negative electrode or positive electrode has a thickness of at least 50 μm and less than or equal to 200 μm. In some embodiments, in some embodiments, the negative electrode or positive electrode has a thickness of at least 0.5 μm and less than or equal to 200 μm.

[0184] In some embodiments, the electroactive composite layer of the negative electrode or the positive electrode has a thickness of at least 10 nm, at least 20 nm, at least 40 nm, at least 0.1 μm, at least 0.2 μm, at least 0.5 μm, at least 1 μm, at least 2 μm, at least 5 μm, at least 10 μm, at least 50 μm, at least 100 μm or more. In some embodiments, the electroactive composite layer of the negative electrode or the positive electrode has a thickness of less than or equal to 200 μm, less than or equal to one hundred 50 μm, less than or equal to one hundred microns, less than or equal to 50 μm, less than or equal to 20 μm, less than or equal to 10 μm, less than or equal to 5 μm, less than or equal to 2 μm, less than or equal to 1 μm, less than or equal to 0.5 μm, less than or equal to 0.2 μm, less than or equal to 0.1 μm, or less. Combinations of these ranges are possible. For example, in some embodiments, the electroactive composite layer of the negative electrode or the positive electrode has a thickness greater than or equal to 10 μm and less than or equal to 200 μm. In some embodiments, the electroactive composite layer of the negative electrode or the positive electrode has a thickness greater than or equal to 10 nm and less than or equal to 100 nm, or greater than or equal to 50 nm and less than or equal to 500 nm.

[0185] Various components of the system, such as electrodes (e.g., negative electrode, positive electrode), power source, electrolyte, separator, container, circuit, insulating material, etc., can be manufactured by one of ordinary skill in the art from any of a variety of components. The components can be molded, machined, extruded, pressed, isopressed, infiltrated, coated, or formed by any other suitable technique in a green or fired state. Techniques for forming the components of the system herein are readily known to one of ordinary skill in the art.

[0186] The electrodes described herein (e.g., negative electrode, positive electrode) can have any suitable size or shape. Some non-limiting examples of shapes include sheets, cubes, cylinders, hollow tubes, spheres, etc. The electrodes can have any suitable size, depending on the application they are used for (e.g., separation of gases from ventilation air, direct air capture, etc.). Additionally, the electrodes can include means for connecting the electrodes to another electrode, a power source, and / or another electrical device.

[0187] The various electrical components of the system can be in electrical communication with at least one other electrical component through a device for connection. The device for connection can be any material that allows the flow of electricity to occur between the first component and the second component. A non-limiting example of a device for connecting two electrical components is a wire comprising a conductive material (e.g., copper, silver, etc.). In some cases, the system may also include an electrical connector between two or more components (e.g., a wire and an electrode). In some cases, a wire, an electrical connector, or other devices for connection can be selected so that the resistance of the material is low. In some cases, the resistance can be substantially less than the resistance of the electrodes, electrolytes, and / or other components of the system.

[0188] U.S. Provisional Application No. 62 / 892,962, filed on August 28, 2019, entitled “Electrochemically Mediated Carbon Capturefrom Low Concentration Streams,” U.S. Patent Application No. 15 / 335,258, filed on October 26, 2016, entitled “Electrochemical Process for Gas Separation,” U.S. Patent Application No. 16 / 659,398, filed on October 21, 2019, entitled “Electrochemically Mediated Gas Capture, Including from Low Concentration Streams,” and International Patent Application No. PCT / US2019 / 057224, filed on October 21, 2019, entitled “Electrochemically Mediated Gas Capture, Including from Low Concentration Streams,” are each incorporated herein by reference in their entirety for all purposes.

[0189] The following examples are intended to illustrate certain embodiments of the invention, but are not intended to exemplify the full scope of the invention.

[0190] Example 1

[0191] This example describes experiments, embodiments, and non-limiting theory regarding the effects of oxygen electrochemistry and reactivity on electrochemical separation of a target gas from a gas mixture, as well as methods described herein. The materials and parameter values ​​described in this example are non-limiting and are provided as examples only.

[0192] In the electrochemical process, superoxide ions can be produced by heterogeneous single electron reduction on the electrode surface or by homogeneous single electron transfer reaction of redox-active molecules with dissolved O2. It has been reported that in DMF electrolyte solution, O2 exhibits quasi-reversible electron transfer to form superoxide ions with a half-wave potential of -1.35V (0.87V relative to the standard calomel electrode (SCE) reference electrode). In order to limit or prevent the production of superoxide by heterogeneous reduction on the electrode surface, it has been found in the context of the present disclosure that the half-wave reduction potential of activating quinones should be more positive than the half-wave potential of forming superoxide ions in some cases. In addition, the reduced quinone can undergo a homogeneous single electron transfer reaction with O2 if the half-wave reduction potential of the quinone is more negative than the half-wave reduction potential of O2. The formation of superoxide ions follows or reaction. In the case of weakly complexing quinones, it has been determined that the electrode potential should be sufficiently negative to form the divalent anion quinone required for carboxylation with CO2 in some cases, while in the case of strongly complexing quinones, the formation of semiquinone is sufficient to promote complexation with CO2. In the case of weakly associating quinones, the equilibrium constant for the electron transfer from the divalent anion quinone to O2 can be calculated using the following:

[0193]

[0194] In the case of strongly associating quinones, the equilibrium constant for electron transfer from semiquinone to O2 can be calculated using:

[0195]

[0196] in, and are the formula standard reduction potentials for the first and second electron transfers to quinone, respectively, and is the formula weight standard reduction potential for O2 reduction. Cyclic voltammetry was performed to measure or approximate the standard reduction potentials of various quinones. Tables 1 and 2 summarize the equilibrium constants measured and determined for various quinones. The calculated equilibrium constant (K) of DBQ semiquinone with O2 from this example is 反应 =49.0M -1 ) and the previously reported experimental value (K 反应 =43.8±3.8M -1 )resemblance.

[0197] Table 1. Equilibrium reactions of divalent anions of weakly complex quinones with O2.

[0198]

[0199] Table 2. Equilibrium reactions of semiquinones of strongly complex quinones with O2.

[0200]

[0201] Based on the reaction constants, none of the weakly associating quinones are suitable for electrochemical CO2 separation in the presence of O2 under the measured conditions, because the electron transfer from the divalent anion quinone to O2 is favorable and superoxide ions will be generated in the system. Several strongly associating quinones were determined to be suitable for electrochemical CO2 separation in the presence of O2: PQ-ester (phenanthrenequinone ethyl ester), PQ-I, PQ-I2, PQ, o-NQ, p-NQ-Me2, p-NQ, TBQ, and BQ. The peak potentials of the reduction waves of the various quinone structures measured in this example under N2 and CO2 are summarized in Fig. 9 middle. Fig. 9 The results of cyclic voltammetry tabulated for 20 mM solutions of various quinones shown in Scheme 1 in anhydrous 0.1 M n-tetrabutylammonium hexafluorophosphate ([n-Bu4N]PF6) dimethylformamide (DMF) electrolyte saturated with N2 (upper circular symbols connected by lines for each quinone) or CO2 (lower circular symbols for each quinone) at a scan rate of 100 mV / sec are shown. The filled circular symbols represent the half-wave potentials for the first electron transfer from quinone to semiquinone (right symbol) and the second electron transfer from semiquinone (left symbol) occurring at a more negative electrode potential. The half-wave potentials can be used to approximately determine the standard reduction potential for the transformation.

[0202] Scheme 1. Structures and names of quinone molecules measured in this example.

[0203]

[0204] The more negative electrode potentials and two reduction waves required for carboxylation of weakly complexed quinones in some cases prevent their use as complexing agents in CO2 separation. This is not the case for some strongly complexed quinones, which exhibit sufficient redox properties for efficient separation of CO2 from gas mixtures, especially those containing O2. During the complexation step, these compounds can be electrochemically activated to form semiquinones with electrode potentials of -0.87 V to -1.07 V, which in this case, as expected, is more positive than the -1.35 V that forms undesirable superoxide anions at the electrode.

[0205] These experimental results show that suitable electroactive materials can be identified that have at least one reduced state that is capable of bonding with an exemplary target gas (CO2) but cannot react with oxygen. This example also demonstrates an exemplary way to make such an identification for a given candidate electroactive material.

[0206] Example 2

[0207] This example describes methods for capturing and releasing an exemplary target gas (e.g., CO2), and embodiments of the methods described herein including for ventilation and direct air capture applications, and non-limiting theory. The materials and parameter values ​​described in this example are non-limiting and are provided as examples only.

[0208] The apparatus of this example can be used for a variety of carbon capture applications (low concentration or CO2 rich streams and compositions) at a variety of possible scales. These applications can be classified into those where the goal is to remove CO2 and those where the goal is to elevate CO2 for downstream storage or disposal.

[0209] When CO2 recovery is not important

[0210] Unlike in direct air capture (DAC), in these applications the released CO2 is generally discarded since its volume is small compared to the total gas volume being processed. Therefore, this mode of operation makes sense primarily for applications with feed concentrations <1% CO2 (10,000 ppm), which is advantageous for ventilation applications. Here, CO2 is removed from the input gas mixture ("feed stream") and the bed of the electrochemical cell is saturated. Pure CO2 is then released into the same inlet stream, which is used to purge the bed during the release to regenerate the bed. In this mode, the energy of capture may also not be very important since the bed must be regenerated at a much lower frequency than in other modes (about 10 times / day to 50 times / day). In addition, the energy cost of the convection of the inlet air via a fan is comparable to the capture energy. Therefore, full-bed activation and full-bed regeneration can be performed before adsorption. This will increase the capture energy to about 120 kJ / mol. Fig. 8A A schematic diagram of one non-limiting example of a method of flowing an input gas mixture and other gases (eg, a second gas) under these conditions is shown.

[0211] Aeration (feed concentration: 1,000ppm CO2 to 5,000ppm CO2)

[0212] Removing metabolic CO2 from buildings and other structures has recently gained more attention to improve the efficiency of HVAC (heating, ventilation, and air conditioning) systems by reducing the amount of heat required for incoming air. Indoor CO2 concentrations in human habitation areas are maintained below 5,000 ppm by constantly replacing indoor air with fresh outdoor air up to 10 times a day. The temperature requirements for replacing air (whether cooling or heating) usually result in excessive energy consumption for typical residential and commercial buildings. However, it has been realized that if CO2 is removed from the air, indoor air can be recirculated for longer periods of time with intermittent replacement of much smaller volumes.

[0213] While volatile organic compounds (VOCs) and other indoor air pollutants present at concentrations of <100 ppm are removed by physical filtration and occasional dehumidification, CO2 can be captured directly from recirculated air by the electrochemical cell and gas separation system described herein. After capture, the feed air is depleted of CO2 and used to purge the bed at the time of release, where the outlet flow of the bed is diverted to the outdoors. Constant current release at high current can achieve high regeneration rates of the bed, although not full generation.

[0214] The bed volume required per person can be calculated by scaling the fabricated device. With a CO2 generation rate of about 22 mol / day.person and a bed saturation period of about 0.5 hours, i.e. a regeneration frequency of about 50 / day, the electrochemical cell bed required per person is 0.8×10 -2 m 3 Up to 1×10 -2 m 3 (8L to 10L). This can be easily integrated into existing HVAC systems where the 7.5L / sec. 1 With a standard ventilation requirement of 1000 m / s and a 25°C indoor-outdoor temperature difference, energy consumption reductions of up to 60% can be expected. Heating or cooling at this ventilation rate would require >150 W, while the electrochemical method described herein, at 120 kJ / mol at a rate of 250 μmol / s, would require about 30 W. By reducing the total air replacement requirement to 20% of the specified value, the total energy consumption should not exceed 60 W.

[0215] The electrochemical cells and gas separation systems and methods described herein can also be used for cabin ventilation, in which case the operating mode is very similar to indoor ventilation, with smaller beds and more frequent regeneration. In addition, the electrochemical ventilation unit can be installed on spacecraft and space stations where CO2 removal is the only possible ventilation mechanism. Current NASA requirements for the International Space Station (ISS) require the removal of about 4kg / day of CO2. Current pressure swing adsorption (PSA) or temperature swing adsorption (TSA) systems operate at 300W. In this case, the regeneration of the bed can be carried out by releasing pure CO2 into the vacuum of space with the inlet valve closed. But recently, considering NASA's "zero waste" policy, there has been interest in valuing captured CO2 into other useful compounds and oxygen. In this case, the electrochemical system described herein must operate in a CO2 recovery mode.

[0216] CO2 recovery is important

[0217] One possible use for CO2 capture in this mode of operation is to boost CO2 concentration from low inlet concentrations to nearly pure CO2 for downstream storage or valorization. CO2 capture by the electrochemical method described herein is performed in this mode in a similar manner as before. For high feed concentrations and where capture energetics are important, adsorption can be performed by activating a half-bed followed by constant potential capture. However, full-bed activation can also be performed when the inlet concentration is very low and it is desirable to disconnect the power supply.

[0218] However, the release of pure CO2 is carried out with the inlet seal just before breakthrough after flushing the bed with a pure CO2 stream to remove the CO2-depleted gas column. The last CO2 column is then removed by flushing with pure N2, as Figure 6 As shown. During the flushing step (before and after release, respectively), the flow rates of pure CO2 and N2 are very high to achieve Re>2000, which ensures a plug flow with a sharp front. This minimizes mixing at the gas column interface, which allows a sharp transition from one gas to the other at the outlet. Figure 8B A schematic diagram of one non-limiting example of a method of flowing an input gas mixture and other gases (eg, a second gas) under these conditions is shown.

[0219] The water content in exhaust and indoor air can have negative effects on electrochemical cells, including decomposition of the electrolyte ionic liquid (IL) and reduction of electrode capacity by competing with CO2 for reaction with reduced quinones. In some cases, this can be avoided by using a hydrophobic IL that repels water from the wet electrode. Hydrophobic ILs typically have highly fluorinated cations and anions, such as bis[(trifluoromethyl)sulfonyl]imide [Tf2N - ], which further increases the solubility of CO2 in the IL and may enhance its transport through the electrode.

[0220] Direct Air Capture (DAC) (e.g., feed concentration: 300 ppm CO2 to 400 ppm CO2)

[0221] DAC has gained importance with the growing interest in it as a negative carbon technology to offset the carbon footprint. However, most existing adsorbent materials considered or under development for DAC require thermal regeneration; a process associated with energy losses of the adsorbent and other matrix materials used.

[0222] The thermodynamic minimum work to recover 100% of CO2 at 100% purity from a binary gas mixture is given by:

[0223]

[0224] Where R is the gas constant, T is the temperature, and y is the mole fraction of CO2 in the binary mixture. The above equation shows that the minimum work of separation increases significantly with decreasing CO2 concentration, reaching a value of about 22 kJ / mol at 400 ppm (the average value of atmospheric CO2 concentration). However, the charge and discharge electrochemistry of quinone has a minimum VQ work greater than that. Therefore, the energy required for DAC using the electrochemical method described herein is independent of the inlet CO2 concentration.

[0225] The capture process can be performed with half-bed or full-bed activation. However, considering the energy economy of DAC technology, it is recommended in some cases to perform capture at constant potential after half-bed activation. The release process can follow Figure 8B The scheme described in allows the recovery of pure CO2. The regeneration frequency of the beds in a DAC (even for small beds at reasonable inlet flow rates) is very small, and the capture time can be of the order of days.

[0226] While the electrochemical systems and methods described herein have been determined to allow for a DAC of about 45 kJ / mol, which is lower than many thermal regeneration systems (55 kJ / mol to 130 kJ / mol), additional expense may be incurred when running fans to force convection of air through the electrochemical cells. The electrochemical devices described herein have been fabricated and found to have a pressure drop of no greater than 100 Pa at flow rates of 1 L / min to 2 L / min. However, a greater pressure differential may be required in some cases to allow for physical filtering of dust and other air pollutants.

[0227] Example 3

[0228] This example describes experiments, embodiments, and non-limiting theory regarding the electrochemically mediated reactivity of certain electroactive species with target gases.The materials and parameter values ​​described in this example are non-limiting and are provided as examples only.

[0229] To demonstrate the reactivity of the electroactive species of the non-limiting examples with carbon dioxide, cyclic voltammetry experiments were performed with the above optionally substituted quinones in the presence of carbon dioxide and in an inert nitrogen atmosphere. Cyclic voltammetry of weakly complexed quinones was also performed.

[0230] Cyclic voltammetry measurements were performed using a VersaStudio RT-PCR system from Princeton Applied Research. TM The Parstat 3000-A potentiostat with software was carried out with a standard three-electrode cell. The electrochemical measurements were carried out in a glass cell, and the temperature of the solution was maintained at a defined temperature. The platinum working electrode was purchased from BASi. Platinum wire was used as the counter electrode and a leak-free Ag / AgCl reference electrode was used. Ferrocene was used as an internal standard. 0.1M [n-BU4N] PF6 electrolyte in DMF was used. The solution was carefully purged with nitrogen under gentle stirring for 30 minutes, and a nitrogen atmosphere was maintained during the electrochemical experiment.

[0231] Weak complex quinone

[0232] The five weak complex quinones mentioned in Example 1 are classified based on their reactivity with carbon dioxide during electrochemical reduction. Based on the effect of its interaction with CO2 on its redox properties, the weak complex quinones are tetrachlorobenzoquinone (BQ-Cl4), 2,7-dichlorobenzoquinone (BQ-Cl2), 2-3-dichloronaphthoquinone (p-NQ-Cl2), 2-chloro-9,10-anthraquinone (AQ-Cl), 9,10-anthraquinone 2-propionate (AQ-COO-C3H7) and 9,10-anthraquinone butylamide derivative (AQ-CONH-C4H9). Figure 12a shows the cyclic voltammogram of AQ-C1 at a scan rate of 100mV / second under N2 (left) and CO2 (right) atmospheres. The results of AQ-Cl represent the other four specified weak complex quinones. When the electrolyte solution was saturated with CO2, no changes were observed in either the cathodic or anodic waves of the first electron transfer (at more positive potentials), but the cathodic wave of the second electron transfer shifted positively and the oxidation wave exhibited features indicative of irreversibility at the scan rate employed. Fig. 12A In the N2 atmosphere, AQ-Cl exhibits two reversible single electron transfer processes, in which relative to ferrocene / Ferrocene(Fc + / Fc), the first half-wave potential at -1.26 V and the second half-wave potential at -2.00 V. When CO2 was introduced into the solution, no change was observed in the cathodic peak current and position of the first electron transfer, but the positive shift of the second cathodic wave indicated that the reductive addition of CO2 to the AQ-C1 dianion occurred. This chemical reaction between the dianion and CO2 is believed to occur through a nucleophilic addition reaction between the oxygen anion and the positively charged carbon atom of the CO2 molecule.

[0233] The value of the association constant for the complex of CO2 with the divalent anion of the weakly complex quinone is calculated from the positive shift of the half-wave potential of the second electron transfer when CO2 is introduced into the solution using the following formula:

[0234]

[0235]

[0236] where F is the Faraday constant, R is the ideal gas constant, T is the temperature, is the shift in the half-wave potential when CO2 is introduced into the system, and [CO2] is the concentration of dissolved CO2. The calculated values ​​range from 6×10 1 M -1 to 2.32×10 of AQ-Cl 3 M -1 .

[0237] The changes in the CO2 association constants of BQ-Cl2, BQ-Cl4, and p-NQ-Cl2 are due to the resonance and inductive stabilization effects of the oxygen anions caused by the electron withdrawing substituents on the quinone-type ring structure. Greater stabilization of the oxygen anions reduces their nucleophilic reactivity towards CO2 addition and reduces the CO2 association constant. For example, the reduction in the CO2 binding constant of p-NQ-Cl2 relative to the BQ-Cl2 dianion is believed to be primarily due to resonance stabilization caused by electron delocalization within the aromatic phenyl group fused to the quinone ring structure, which is consistent with the effects of resonance stabilization on the basicity of aromatic oxide anions observed in phenol and 1-naphthol molecules. In dilute aqueous solutions, phenol (phenolate pk b =3.11) than 1-naphthol (naphthol salt pK b =3.66) has a greater basicity. In organic solvents, the strength of the oxygen anion as a Lewis base is reflected in its hydrogen bonding and ability. The lower CO2 binding constant measured for BQ-Cl4 compared to BQ-Cl2 is believed to be mainly due to the electron-withdrawing properties of the chlorine side groups; replacing the two hydrogen atoms of BQ-Cl2 with two chlorine atoms makes the divalent anion BQ-C14 more stabilized and reduces the nucleophilicity of the anion to CO2.

[0238] The fusion of an aromatic phenyl group to the quinone ring exhibits a lesser effect on the resonance stabilization of the oxygen anion than the attachment of an electron withdrawing group to the quinone ring structure. Thus, replacing the electron withdrawing group with a fused aromatic phenyl group increases the CO2 association constant, as shown by the anthraquinone derivatives AQ-Cl, AQ-CONH-C4H9, and AQ-COO-C3H7, which are classified as weakly complexed quinones because CO2 addition does not affect the reduction and oxidation waves of the first electron transfer and the half-wave electron transfer is positively shifted.

[0239] Electrochemical properties of strongly complex quinones in the presence of CO2

[0240] The addition of CO2 to quinones that interact strongly with CO2 results in cyclic voltammetric waves that are significantly different from those discussed for the weakly complexed quinones described above. The 11 quinones mentioned in Example 1 are classified as strongly complexed quinones: BQ, p-NQ, AQ, AQ-O-C3H7, o-NQ, PQ, DBQ, TBQ, p-NQ-Me2, PQ-I, and PQ-I2. The first six compounds are discussed below because these quinones present unique cyclic voltammetric patterns over the full range of interactions.

[0241] The anthraquinone derivative AQ-COO-C3H7 exhibits the strongest CO2 association constant in the group of weakly complex quinones. The electron-withdrawing property of the carbonyl group (C=O) of the ester substituent reduces the Lewis basicity of the oxygen anion, which is believed to limit its association constant with CO2. Replacing the ester group with any electron-donating substituent is believed to result in an increase in the CO2 association constant. The electrochemical behavior of two anthraquinone derivatives AQ-COO-C3H7 and AQ-O-C3H7 with opposite inductive effects was compared with that of the unsubstituted anthraquinone molecule AQ, in which the inductive effect of the hydrogen substituent is between the inductive effects of the ester and ether substituents.

[0242] Figures 12B to 12D Cyclic voltammograms of AQ-COO-C3H7, AQ, and AQ-O-C3H7 at a scan rate of 100 mV / sec in DMF electrolyte saturated with N2 (left) and saturated in CO2 (right) atmosphere are shown, respectively. The cyclic voltammograms of AQ-COO-C3H7, AQ, and AQ-O-C3H7 show two single electron transfer waves under N2, which are separated by about 0.7 V. Like other weakly complex quinones, when the electrolyte solution is saturated with CO2, the peak current and position of the first reduction wave of AQ-COO-C3H7 do not change, but the second reduction wave is positively shifted ( Fig. 12B ). In both the hydrogen and ether substituent cases, the CO2 association constants are expected to be stronger than those in the ester case, so for AQ and AQ-O-C3H7 (respectively Fig. 12C and 12D ), a larger positive shift of the second reduction wave is observed. The positive shift of the second (more negative) reduction wave is accompanied by an increase in the first cathode current. Fig. 12C ), the second reduction wave is only a shoulder, while in AQ-O-C3H7( Fig.12D ) was not observed in the case of AQ-O-C3H7. The first cathode peak current of AQ increased from 56μA to 70μA, while the cathode peak current of AQ-O-C3H7 increased from 56vA to 83μA. Only one oxidation wave was observed in the voltammograms of AQ and AQ-O-C3H7, where the current of the oxidation wave under CO2 was higher than that of the oxidation wave under N2. The current increase in the first oxidation wave is believed to correspond to the oxidation of the quinone-CO2 monoadduct, which releases CO2 and regenerates semiquinone, which is immediately oxidized to a neutral quinone species. Since the energy of the electrode potential of the oxidized monoadduct is sufficient to further oxidize the semiquinone produced thereby, two simultaneous oxidation processes occur.

[0243] Quinones with electron donating substituents are expected to have stronger CO2 association constants. Based on their molecular structures, the CO2 association constants of the oxyanions of BQ and p-NQ should be higher than those of both AQ and AQ-O-C3H7. Based on the previously described concept of resonance stabilization and its effect on the basicity of aromatic oxyanions, the basicity of the p-NQ oxyanion is expected to be between the basicities of the oxyanions of BQ and AQ. In the absence of a fused aromatic benzene ring, the BQ oxyanion is the strongest Lewis base among the three quinones.

[0244] Figures 13A to 13B Shown is the scanning rate of p-benzoquinone (BQ) in 0.1 M [n-Bu4N]PF6 in DMF saturated with N2 or CO2 at a scan rate of 100 mV / sec using quinone concentrations of 4 mM (left) and 20 mM (right) Fig.13A ) and p-naphthoquinone (p-NQ) ( Fig. 13B ) solutions. Under nitrogen, two well-separated electrochemical waves were observed for BQ and p-NQ solutions. In the presence of CO2, these quinones showed: a significant increase in the peak current of the first electron transfer, which was attributed to two consecutive electron transfers at this reduction potential; and the disappearance of the reduction wave of the second electron transfer, which may be attributed to the rapid disproportionation of semiquinone (producing a monoadduct dianion and a neutral quinone).

[0245] At a BQ concentration of 4 mM, the presence of CO2 increased the peak current of the first electron transfer from 24.5 μA to 36.0 μA, an increase of about 47%. For 20 mM BQ, the current increase reached 54%. Similarly, at 4 mM p-NQ, the peak current increased from 22.6 vA to 30.3 μA, or an increase of about 34%, while at 20 mM p-NQ, the peak current increased from 77.6 μA to 135.5 μA, or an increase of about 75%. This indicates that the formation of monoadduct dianions of BQ and p-NQ depends on the concentration of their semiquinones within the boundary layer at the electrode surface.

[0246] Figures 13A to 13B The voltammograms of BQ and p-NQ are shown, which show two oxidation waves due to electron abstraction from the products of the interaction of the divalent anion quinone with CO2, which correspond to two different oxidation mechanisms at two oxidation potentials. Figures 13A to 13BThe first oxidation wave is attributed to the CO2 monoadduct, while the second oxidation wave occurring at a less negative potential is attributed to the oxidation process of the diadduct. In the case of BQ, the anodic peak current of the monoadduct was observed at -0.83 V, while the anodic peak current of the diadduct was observed at -0.32 V. In the case of p-NQ, the anodic peak current of the monoadduct oxidation process was observed at -1.01 V, while the anodic peak current of the diadduct was observed at -0.50 V.

[0247] Mechanistic analysis of the electrochemistry of naphthoquinone and subsequent CO2 addition

[0248] A more in-depth mechanistic analysis of p-NQ was performed to gain a more complete understanding of the mechanism of electrochemically induced reductive CO2 addition. This was accomplished by studying the CV of p-NQ in the presence of increasing concentrations of CO2 (balanced with N2). Fig.14 Shown is the cyclic voltammetry of a 5 mM solution of p-naphthoquinone (p-NQ) in 0.1 M [n-Bu4N]PF6 in DMF saturated with increasing concentrations of CO2 gas (balanced with N2) at a scan rate of 500 mV sec using a glassy carbon working electrode. Fig.14 The CVs in Figure 2 show a clear trend of new peaks appearing and other peaks decreasing at very low CO2 concentrations. The following discussion will constantly refer to Fig.14 The main observed features are explained by thermodynamic and kinetic phenomena.

[0249] From Fig.14 The first major observation in the CV is that in the presence of CO2 the two reduced species semiquinone NQ ·- and quinol dianion NQ 2- The behavior of NQ is very different. ·- The intensity of the first reduced cathodic peak decreases only slightly with increasing CO2 concentration, indicating a relatively weak equilibrium with CO2.

[0250] The semiquinone monoadduct resulting from this equilibrium has electron density acquired during the first reduction wave (moving from the conjugation of the naphthoquinone aromatic ring to the conjugation of the newly added carboxylate moiety, which is separated from the conjugation of the rest of the molecule by the newly formed sigma bond). This results in relative neutralization of the aromatic ring, which can now acquire a second electron at a more positive potential, the first reduction potential, or a few tens of mV thereof, as Fig.14 100% CO2CV and Fig. 13B This is believed to be mainly because the reduction of quinone at the electrode interface occurs via electron transfer from the electrode to the aromatic conjugated system.

[0251] At low CO2 concentrations, Fig.14In the 0.5% CO2CV and 1.0% CO2CV in the graph, the forward reaction rate in the semiquinone monoaddition formation reaction is relatively slow, and the cathodic peak between the first reduction wave and the second reduction wave appears closer to the second reduction wave. As the concentration of CO2 increases, in the 20% CO2CV and 100% CO2CV, the peak moves more positively, and in the case of 100% CO2, the peak merges with the cathodic peak of the first reduction wave, causing the peak position to move due to the convolution effect. This peak is believed to be mainly caused by kinetic effects: as shown in the NQ in the first reduction wave near the electrode, the peak moves more positively. ·- The formation of CO2 in the electrode diffusion layer reacts with the semiquinone diadduct, which in turn can accept a second electron at a more positive reduction potential. However, during the negative (cathodic) scan of the CV, the glassy carbon electrode acquires increasingly negative potentials and thus increasingly larger overpotentials η, where η = E 施加 -E 平衡 and E 平衡 Obtained from the Nernst expression. According to the Butler-Volmer expression (where i is the current associated with the Faraday electrochemical reaction), the overpotential η drives the kinetics of the second reduction of the semiquinone monoadduct (i.e., the reduction of the semiquinone monoadduct), which increases exponentially until it is offset by the transport resistance, i.e., the depletion of the reactants in the electrode diffusion layer. This is believed to result in the appearance of a kinetic cathodic peak between the two thermodynamic cathodic peaks (which correspond to the two reduction waves of p-NQ).

[0252] think Fig.14 The position of the peak between the two reduction peaks in is strictly determined by the chemical formation rate of the semiquinone (which depends on the concentration of CO2 dissolved in the electrolyte) - the bimolecular reaction rate r = k[NQ ·- The rate constant for the bimolecular reaction was estimated to be k = 25 M -1 Second -1 , which gives about 5 × 10 -3 M seconds -1 The position of this peak depends on the scan rate and can be found in Fig.15 It can be seen that Fig.15 Cyclic voltammetry of a 5 mM solution of p-naphthoquinone (p-NQ) in 0.1 M [n-Bu4N]PF6 in DMF saturated with 20% CO2 (balanced with N2) at different scan rates using a glassy carbon working electrode is shown. Fig.15In the , at low scan rates of 50mV / sec to 100mV / sec, this peak merges with the cathodic peak of the first reduction wave, while at higher scan rates (considered to be greater than the time constant of the chemical reaction), a second peak appears and moves negatively away from the first peak. The intensity of this peak also increases relative to the first reduction wave because the electrochemical reaction that occurs only after the chemical reaction has occurred occurs at a greater overpotential. The voltage difference between the two cathodic peaks corresponds to the time required for the chemical reaction to proceed.

[0253] The secondary chemical reaction of the dianion diadduct proceeds as expected and does not contribute much to the electrochemical behavior beyond the thermodynamic stabilization of the dianion diadduct.

[0254] The steric effect of p-quinone and o-quinone

[0255] Quinones exist in two isomeric forms: 1,4-cyclohexadienedione (p-quinone) and 1,2-cyclohexadienedione (o-quinone). The above discussion has focused on the association of the p-quinone dianion with CO2. The association of CO2 with two o-quinones, PQ (an isomeric form of AQ) and o-NQ (an isomeric form of p-NQ), was evaluated. In dilute aqueous solutions, the deprotonated hydroquinone (pK b =3.65) than the deprotonated catechol (pk b =4.15) has a greater basicity; therefore, the basicity of the dianion of o-quinone is considered to be less than that of the dianion of p-quinone. Figures 16A to 16B Shown is the 9,10-phenanthrenequinone (PQ) ( ) in a 0.1 M [n-Bu4N]PF6 solution in DMF saturated with N2 or CO2 at quinone concentrations of 4 mM (left) and 20 mM (right) using a platinum electrode at a scan rate of 100 mV / sec. Fig.16A ) and o-naphthoquinone (o-NQ) ( Fig. 16B ) by cyclic voltammetry. Figures 16A to 16B As shown, in a nitrogen-saturated DMF electrolyte solution, PQ shows two typical electrochemical waves, corresponding to the formation of semiquinone and divalent anion quinone, respectively. In the case of PQ, the half-wave potential of the first electron transfer appears at -1.09V, and the half-wave potential of the second electron transfer appears at -1.96V, with an interval of about 0.87V. This value is greater than the half-wave potential interval of about 0.75V observed for AQ. Similarly, the potential interval of o-NQ is about 0.89V, which is slightly wider than the potential interval of 0.87V of p-NQ. It is believed that the larger potential interval of ortho-quinone is due to the close proximity of the two oxygen anions at the C1 and C2 positions (which experience greater electrostatic repulsion).

[0256] Addition of CO2 to the DMF solution containing PQ resulted in a substantial increase in the peak current of the first electron transfer and the disappearance of the reduction wave of the second electron transfer ( Fig.16A ), which is significantly different from the trend observed in the cyclic voltammogram of AQ ( Fig. 12C ), the cyclic voltammogram of AQ still shows a shoulder in the reduction wave due to the second electron transfer under CO2 atmosphere. These results indicate that the association of PQ with CO2 is stronger than that of AQ with CO2. The increase in the PQ peak current for the first electron transfer is attributed to two consecutive electron transfers at the first reduction wave. Adding CO2 to the DMF solution containing o-NQ also resulted in a significant increase in the peak current for the first electron transfer, and no separate reduction wave for the second electron transfer was observed ( Fig. 16B At a PQ concentration of 4 mM ( FIG. 16 ), the addition of CO2 increased the peak current of the first electron transfer from 22 μA to 39 μA, an increase of about 77%. At a PQ concentration of 20 mM ( Fig. 16B ), the percentage of current increase decreased to 71%. In the case of o-NQ, a more significant decrease in the percentage of current increase was observed with increasing quinone concentration. At 4 mM concentration ( Fig. 16B ), the peak current increase percentage is about 93%, while at 20mM concentration, the peak current increase percentage is only about 84%. According to the results obtained for p-quinone, the difference in the trend of peak current increase with increasing quinone concentration indicates different mechanisms of CO2 binding. For o-quinone, the linear correlation of the peak current increase with the relative concentration ratio of CO2 to quinone indicates the following mechanism: electron transfer, followed by a chemical step, and then electron transfer (ECE). The carbonate complex is formed by the initial single electron reduction of the neutral quinone, which forms a semiquinone, which then compounds with CO2. It is believed that this intermediate complex immediately undergoes a second single electron reduction in close proximity to the electrode surface to form a mono(carbonate) of the divalent anion quinone. When the electrolyte is saturated with CO2, the compounding of semiquinone with CO2 is demonstrated by a small positive shift in the first electron transfer. The positive shift of o-NQ is about 38mV, and the positive shift of PQ is about 14mV.

[0257] As observed and discussed above, the voltammograms of PQ and o-NQ in CO2-saturated DMF electrolyte show two oxidation waves ( Figures 16A to 16B), corresponding to the oxidation of CO2 monoadduct and diadduct, respectively. The relative peak currents of these oxidation waves give an indication of the fraction of divalent anion quinone-CO2 complexes that have undergone each oxidation process in the diffusion layer on the electrode surface. The CO2 concentration dissolved in the DMF electrolyte solution is about 0.175M at 1 bar CO2 pressure, or about 44 times that of 4mM quinone concentration. At the same CO2 concentration, at a quinone load of 20mM, the relative concentration of dissolved CO2 to quinone is 8.75. Along with the increase of relative CO2 concentration, the equilibrium position moves and is unfavorable for the dissociation of CO2-divalent anion quinone diadduct, so the relative peak current of the two oxidation reactions in the case of 4mM quinone solution is lower than the relative peak current of the two oxidation reactions in the case of 20mM quinone solution, as shown in Figure 16.

[0258] The experiments described in this example demonstrate the reactivity between certain electroactive species (e.g., certain semiquinones) and carbon dioxide at relatively positive potentials. As described above, with the insight and guidance of the present disclosure, incorporating certain described electroactive species (e.g., strongly complexing optionally substituted quinones) into electrochemical cells can promote electrochemically mediated carbon dioxide capture under conditions where there is relatively little (or no) electrochemically mediated reactivity with other species such as O2.

[0259] Although several embodiments of the present invention have been described and illustrated herein, a person of ordinary skill in the art will readily envision a variety of other ways and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages described herein, and each of such variations and / or modifications is considered to be within the scope of the present invention. More generally, it will be readily understood by those skilled in the art that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications for which the teachings of the present invention are used. Those skilled in the art will recognize or be able to determine many equivalents of some specific embodiments of the present invention described herein using only routine experiments. Therefore, it should be understood that the foregoing embodiments are given only by way of example, and within the scope of the appended claims and their equivalents, the present invention may be implemented in other ways except for specific description and protection. The present invention relates to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods is included within the scope of the present invention if such features, systems, articles, materials, and / or methods are not inconsistent with each other.

[0260] As used herein in the specification and claims, the phrase "at least a portion" means some or all. According to certain embodiments, "at least a portion" may mean at least 1 wt%, at least 2 wt%, at least 5 wt%, at least 10 wt%, at least 25 wt%, at least 50 wt%, at least 75 wt%, at least 90 wt%, at least 95 wt%, or at least 99 wt%, and / or in certain embodiments, up to 100 wt%. According to certain embodiments, "at least a portion" may mean at least 1 volume%, at least 2 volume%, at least 5 volume%, at least 10 volume%, at least 25 volume%, at least 50 volume%, at least 75 volume%, at least 90 volume%, at least 95 volume%, or at least 99 volume%, and / or in certain embodiments, up to 100 volume%. According to certain embodiments, "at least a portion" may mean at least 1 mol%, at least 2 mol%, at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, at least 90 mol%, at least 95 mol%, or at least 99 mol%, and / or in certain embodiments, up to 100 mol%.

[0261] Unless explicitly stated to the contrary, as used herein in the specification and claims, nouns without quantifiers should be understood to mean "at least one".

[0262] The phrase "and / or" as used herein in the specification and in the claims should be understood to mean "either or both" of the elements so combined, i.e., the elements are present together in some cases and separately in other cases. Unless expressly indicated to the contrary, other elements may optionally be present in addition to the elements specifically identified by the "and / or" clause, whether related or unrelated to those specifically identified. Thus, as a non-limiting example, when used in conjunction with open-ended language such as "comprising", a reference to "A and / or B" may refer to A without B (optionally including elements other than B) in one embodiment; to B without A (optionally including elements other than A) in another embodiment; to both A and B (optionally including other elements) in yet another embodiment; and so on.

[0263] As used herein in the specification and in the claims, "or / or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating the items in a list, "or / or" or "and / or" shall be interpreted as inclusive, i.e., including at least one of a plurality of elements or a list of elements, but also including more than one, and optionally additionally unlisted items. Only explicitly indicating the opposite term, such as "only one of" or "exactly one of", or "consisting of..." when used in the claims, will refer to including exactly one element in a plurality of elements or a list of elements. In general, the term "or / or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e., "one or the other but not both") when preceded by an exclusive term (e.g., "either", "one of", "only one of", or "exactly one of"). "Substantially consisting of..." when used in the claims shall have its ordinary meaning used in the field of patent law.

[0264] As used herein in the specification and claims, when referring to a list of one or more elements, the phrase "at least one" should be understood to mean at least one element selected from any one or more elements in the list of elements, but not necessarily including at least one of each and every element specifically listed in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows that elements other than the elements specifically identified in the list of elements to which the phrase "at least one" refers may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B", or equivalently, "at least one of A and / or B") may refer, in one embodiment, to at least one A, optionally including more than one A, without B being present (and optionally including elements other than B); in another embodiment, to at least one B, optionally including more than one B, without A being present (and optionally including elements other than A); in yet another embodiment, to at least one A, optionally including more than one A, and at least one B, optionally including more than one B (and optionally including other elements); and so on.

[0265] In the claims and in the foregoing specification, all transitional phrases such as "comprising," "including," "with," "having," "containing," "involving," "having," etc. are to be understood as open ended, i.e., meaning including, but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as set forth in the U.S. Patent Office Manual of Patent Examining Procedures Section 2111.03.

Claims

1. An electrochemical cell comprising: a negative electrode comprising a first electroactive material; Positive electrode; and a separator between the negative electrode and the positive electrode, the separator being capable of containing a conductive liquid; The first electroactive material has: Oxidation state; and at least one reduced state in which the substance is capable of bonding with carbon dioxide, but for which a reaction between the first electroactive substance in the at least one reduced state and oxygen O2 has a Gibbs free energy change ΔG greater than 0 kcal / mol at a temperature of 298 K rxn . 2 . The electrochemical cell according to claim 1 , wherein the first electroactive material is immobilized on and / or within the negative electrode.

3. An electrochemical cell comprising: a negative electrode comprising a first electroactive material immobilized on the negative electrode; and Positive electrode; The first electroactive material has: Oxidation state; and at least one reduced state in which the substance is capable of bonding with carbon dioxide, but for which a reaction between the first electroactive substance in the at least one reduced state and oxygen O2 has a Gibbs free energy change ΔG greater than 0 kcal / mol at a temperature of 298 K rxn .

4. The electrochemical cell of any one of claims 1 to 3, wherein the negative electrode comprises a main electroactive composite layer comprising the first electroactive material.

5. The electrochemical cell according to any one of claims 1 to 3, wherein the standard reduction potential ratio for producing the at least one reduced state of the first electroactive species in the conductive liquid is for oxygen O2 and superoxide O2 - The standard reduction potentials for interconversion between them are corrected.

6. The electrochemical cell according to any one of claims 1 to 3, wherein the standard reduction potential for producing the at least one reduced state of the first electroactive species in the conductive liquid is greater than that for superoxide O2 - With peroxide O2 2- The standard reduction potentials of the interconversions are corrected.

7. The electrochemical cell according to any one of claims 1 to 3, wherein the first electroactive material is part of a polymer material immobilized on the negative electrode.

8. The electrochemical cell of any one of claims 1 to 3, wherein the first electroactive material comprises an optionally substituted quinone.

9. The electrochemical cell of any one of claims 1 to 3, wherein the first electroactive material comprises one or more structures selected from formula (IA) and (IB): Where R 1 , R 2 , R 3 , and R 4 are the same or different, and are hydrogen, halogen, hydroxyl, carboxylate / carboxylic acid, sulfonate / sulfonic acid, alkylsulfonate / alkylsulfonic acid, phosphonate / phosphonic acid, alkylphosphonate / alkylphosphonic acid, acyl, amino, amido, quaternary ammonium, branched or unbranched alkyl, heteroalkyl, alkoxy, glycoloxy, polyalkylene glycoloxy, imino, polyimino, branched or unbranched alkenyl, branched or unbranched alkynyl, aryl, heteroaryl, heterocyclyl, nitro, nitrile, thio, and / or carbonyl, any of which is optionally substituted, and / or R 1 To R 4 Any two adjacent groups of are linked together to form an optionally substituted ring.

10. The electrochemical cell of any one of claims 1 to 3, wherein the first electroactive material comprises one or more of the following: PQ-ester, PQ-I, PQ-I2, PQ, o-NQ, p-NQ-Me2, p-NQ, TBQ, and BQ, the structure of which is shown below: Where R 5 is an optionally substituted branched or unbranched C1 to C18 alkyl group.

11. The electrochemical cell of any one of claims 1 to 3, wherein the negative electrode comprises a gas permeable layer.

12. The electrochemical cell of any one of claims 1 to 3, wherein the negative electrode is porous.

13. The electrochemical cell of claim 3, wherein the electrochemical cell comprises a separator between the negative electrode and the positive electrode, the separator being capable of containing a conductive liquid.

14. The electrochemical cell of any one of claims 1, 2, and 13, wherein the separator comprises the conductive liquid.

15. The electrochemical cell of any one of claims 1, 2, and 13, wherein the separator is saturated with the conductive liquid.

16. The electrochemical cell of any one of claims 1, 2, and 13, wherein the conductive liquid comprises a non-volatile electrolyte.

17. The electrochemical cell of any one of claims 1, 2, and 13, wherein the conductive liquid comprises a room temperature ionic liquid.

18. The electrochemical cell of claim 17, wherein the room temperature ionic liquid comprises 1-butyl-3-methylimidazole Bis(trifluoromethylsulfonyl)imide serves as the cationic component.

19. The electrochemical cell of claim 17, wherein the room temperature ionic liquid comprises bis(trifluoromethylsulfonyl)imide as an anion component.

20. The electrochemical cell of any one of claims 1 to 3, wherein the positive electrode comprises a second electroactive material.

21. The electrochemical cell of claim 20, wherein the positive electrode comprises a gas permeable layer and a complementary electroactive composite layer comprising the second electroactive material.

22. The electrochemical cell of any one of claims 1 to 3, wherein the negative electrode is a first negative electrode, and the electrochemical cell further comprises: a second negative electrode comprising the first electroactive material; and A second separator between the positive electrode and the second negative electrode is saturable with a conductive liquid.

23. The electrochemical cell of claim 22, wherein the positive electrode comprises a substrate between a first complementary electroactive composite layer facing the first negative electrode and a second complementary electroactive composite layer facing the second negative electrode.

24. The electrochemical cell of claim 20, wherein the second electroactive material comprises a redox active polymer.

25. The electrochemical cell of claim 24, wherein the redox-active polymer comprises polyvinylferrocene.

26. The electrochemical cell of claim 20, wherein the second electroactive material comprises an intercalation compound.

27. The electrochemical cell of claim 26, wherein the intercalation compound comprises lithium iron phosphate, LiFePO4.

28. The electrochemical cell of claim 4, wherein the primary electroactive composite layer comprises a carbonaceous material.

29. A gas separation system comprising a plurality of electrochemical cells according to any one of claims 1 to 3 in fluid communication with a gas inlet and a gas outlet.

30. The gas separation system according to claim 29, which is configured to have a mass flow rate of 0.003 kg or more at a gas flow rate of 0.001 L / sec or more and 500 L / sec or less. CO2 / (kg 床 t b ) for capturing carbon dioxide, where kg 床 is the bed weight and t b is the breakthrough time of the gas separation system.

31. The gas separation system of claim 30, wherein the gas separation system has a mass fraction of less than or equal to 0.05 kg at a gas flow rate of greater than or equal to 0.001 L / sec and less than or equal to 500 L / sec. CO2 / (kg 床 t b )’s productivity for capturing carbon dioxide.

32. The gas separation system according to claim 30, wherein the gas flow rate is 2 Air flow rate over the negative electrode area.

33. The gas separation system of claim 30, wherein the gas flow rate is the gas flow rate per 10 electrochemical cells of the plurality of electrochemical cells in the system.

34. The gas separation system of claim 29, wherein the plurality of electrochemical cells are electrically connected in parallel.

35. The gas separation system of claim 29, wherein the plurality of electrochemical cells are electrically connected in series.

36. The gas separation system of claim 29, wherein a flow field exists between at least some of the plurality of electrochemical cells.

37. The gas separation system of claim 35, wherein a first electrochemical cell and a second electrochemical cell of the plurality of electrochemical cells electrically connected in series are electrically connected via one or more conductive materials between the first electrochemical cell and the second electrochemical cell.

38. The gas separation system of claim 37, wherein the one or more electrically conductive materials comprise a bipolar plate.

39. A method for at least partial gas separation, the method comprising: Applying a potential difference across the electrochemical cell of any one of claims 1 to 3; exposing a gas mixture comprising carbon dioxide to the electrochemical cell; as well as At least a portion of the carbon dioxide is bonded to the first electroactive species to produce a treated gas mixture having a lower amount of carbon dioxide than the gas mixture.

40. A method for at least partial gas separation, the method comprising: In the gas separation system of claim 29, applying a potential difference across one or more electrochemical cells of the plurality of electrochemical cells; exposing a gas mixture comprising carbon dioxide to the one or more electrochemical cells; as well as At least a portion of the carbon dioxide is bonded to the first electroactive species to produce a treated gas mixture having a lower amount of the carbon dioxide than the gas mixture.

41. A method for at least partial gas separation, the method comprising: Applying a potential difference across the electrochemical cell of any one of claims 1 to 3; exposing a gas mixture comprising carbon dioxide to the electrochemical cell; as well as removing an amount of said carbon dioxide from said gas mixture during and / or after application of a first potential difference, Wherein less than or equal to 0.1% by volume of any oxygen O2 present in the gas mixture is removed from the gas mixture.

42. The method of claim 41, wherein the concentration of the carbon dioxide in the gas mixture prior to exposure to the electrochemical cell is less than or equal to 5,000 ppm.

43. The method of claim 41, wherein the concentration of the carbon dioxide in the gas mixture prior to exposure to the electrochemical cell is less than or equal to 500 ppm.

44. The method of claim 41, wherein the gas mixture comprises oxygen (O2) prior to exposure to the electrochemical cell.

45. The method of claim 41, wherein oxygen O2 is present in the gas mixture at a concentration greater than or equal to 0 volume % or greater than or equal to 10 volume % prior to exposure to the electrochemical cell.

46. ​​The method of claim 41, wherein oxygen O2 is present in the gas mixture at a concentration less than or equal to substantially 100 volume percent prior to exposure to the electrochemical cell.

47. The method of claim 41, wherein oxygen O2 is present in the gas mixture at a concentration less than or equal to 50% by volume prior to exposure to the electrochemical cell.

48. The method of claim 41, wherein oxygen O2 is present in the gas mixture at a concentration less than or equal to 25% by volume prior to exposure to the electrochemical cell.

49. The method of claim 41, wherein oxygen O2 is present in the gas mixture at a concentration less than or equal to 21% by volume prior to exposure to the electrochemical cell.

50. The method of claim 41, wherein no O2 gas is removed from the gas mixture.

51. The method of claim 41, wherein the gas mixture has a relative humidity of 0% to 100%.

52. The method of claim 41, wherein the gas mixture is one of: ambient air, air in an enclosed space, air in a partially ventilated space.

53. The method of claim 41, wherein the gas mixture is air in one of a vehicle cabin, a manned submersible, or an aircraft.

54. The method of claim 41, wherein the negative electrode comprises a main electroactive composite layer comprising the first electroactive material.

55. The method of claim 41, wherein the standard reduction potential ratio for producing the at least one reduced state of the first electroactive species in the conductive liquid is for oxygen O2 and superoxide O2 - The standard reduction potentials for interconversion between them are corrected.

56. The method of claim 41, wherein the standard reduction potential for producing the at least one reduced state of the first electroactive species in the conductive liquid is greater than that for superoxide O2 - With peroxide O2 2- The standard reduction potentials of the interconversions are corrected.

57. The method of claim 41, wherein the first electroactive material is part of a polymer material immobilized on the negative electrode.

58. The method of claim 41, wherein the first electroactive material comprises an optionally substituted quinone.

59. The method of claim 41, wherein the first electroactive material comprises one or more structures selected from formula (IA) and (IB): Where R 1 , R 2 , R 3 , and R 4 are the same or different, and are hydrogen, halogen, hydroxyl, carboxylate / carboxylic acid, sulfonate / sulfonic acid, alkylsulfonate / alkylsulfonic acid, phosphonate / phosphonic acid, alkylphosphonate / alkylphosphonic acid, acyl, amino, amido, quaternary ammonium, branched or unbranched alkyl, heteroalkyl, alkoxy, glycoloxy, polyalkylene glycoloxy, imino, polyimino, branched or unbranched alkenyl, branched or unbranched alkynyl, aryl, heteroaryl, heterocyclyl, nitro, nitrile, thio, and / or carbonyl, any of which is optionally substituted, and / or R 1 To R 4 Any two adjacent groups of are linked together to form an optionally substituted ring.

60. The method of claim 41, wherein the first electroactive material comprises one or more of: PQ-ester, PQ-I, PQ-I2, PQ, o-NQ, p-NQ-Me2, p-NQ, TBQ, and BQ: Where R 5 is an optionally substituted branched or unbranched C1 to C18 alkyl group.

61. The method of claim 41, wherein the negative electrode comprises a gas permeable layer.

62. The method of claim 41, wherein the negative electrode is porous.

63. The method of claim 41, wherein the electrochemical cell comprises a separator between the negative electrode and the positive electrode, the separator being capable of containing a conductive liquid.

64. The method of claim 63, wherein the isolation member contains the conductive liquid.

65. The method of claim 63, wherein the isolation member is saturated with the conductive liquid.

66. The method of claim 63, wherein the conductive liquid comprises a non-volatile electrolyte.

67. The method of claim 63, wherein the conductive liquid comprises a room temperature ionic liquid.

68. The method of claim 67, wherein the room temperature ionic liquid comprises 1-butyl-3-methylimidazole Bis(trifluoromethylsulfonyl)imide serves as the cationic component.

69. The method of claim 67, wherein the room temperature ionic liquid comprises bis(trifluoromethylsulfonyl)imide as an anionic component.

70. The method of claim 41, wherein the positive electrode comprises a second electroactive material.

71. The method of claim 41, wherein the positive electrode comprises a gas permeable layer and a complementary electroactive composite layer comprising a second electroactive material.

72. The method of claim 41, wherein the negative electrode is a first negative electrode, and the electrochemical cell further comprises: a second negative electrode comprising the first electroactive material; and A second separator between the positive electrode and the second negative electrode is saturable with a conductive liquid.

73. The method of claim 72, wherein the positive electrode comprises a substrate between a first complementary electroactive composite layer facing the first negative electrode and a second complementary electroactive composite layer facing the second negative electrode.

74. The method of claim 70, wherein the second electroactive material comprises a redox active polymer.

75. The method of claim 74, wherein the redox-active polymer comprises polyvinylferrocene.

76. The electrochemical cell of claim 70, wherein the second electroactive material comprises an intercalation compound.

77. The electrochemical cell of claim 76, wherein the intercalation compound comprises lithium iron phosphate, LiFePO4.

78. The method of claim 54, wherein the primary electroactive composite layer comprises a carbonaceous material.

79. A method comprising: applying a first potential difference across the electrochemical cell of any one of claims 1 to 3; exposing a first amount of an input gas mixture comprising carbon dioxide to the electrochemical cell; causing at least a portion of the carbon dioxide to bond with an electroactive species of the electrochemical cell during and / or after applying the first potential difference to produce a first treated gas mixture having a lower amount of carbon dioxide than the input gas mixture; applying a second potential difference across the electrochemical cell; as well as releasing some or all of the carbon dioxide bound to the electroactive material to produce a second treated gas mixture; Wherein, during and / or after the release, the method further comprises: (a) flowing a second gas through the electrochemical cell to remove at least some or all of the released carbon dioxide from the electrochemical cell, and / or (b) applying vacuum conditions to the electrochemical cell to remove at least some or all of the released carbon dioxide from the electrochemical cell.

80. The method of claim 79, wherein during and / or after said releasing, a second gas is flowed through said electrochemical cell to remove at least some or all of the released carbon dioxide from said electrochemical cell.

81. The method of claim 79, wherein the second gas is an inert gas.

82. The method of claim 79, wherein the second gas is a carrier gas.

83. The method of claim 79, wherein the second gas is substantially pure CO2.

84. The method of claim 79, wherein the second gas comprises steam.

85. The method of claim 79, wherein the second gas is a second portion of the input gas mixture.

86. The method of claim 79, wherein greater than one bed volume of carbon dioxide is bound to the first electroactive material.

87. The method of claim 86, wherein greater than one bed volume of carbon dioxide is released from the first electroactive material.

88. The method of claim 79, wherein vacuum conditions are applied to the electrochemical cell during and / or after the releasing to remove at least some or all of the released carbon dioxide from the electrochemical cell.

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