Membraneless electrochemically mediated amine regeneration cell, system, and methods of use thereof

Abstract

This invention is directed towards systems and methods of carbon capture. In embodiments, the invention is directed towards electrochemically mediated amine regeneration (EMAR) which provide continuous CO2 capture for extended periods. The EMAR systems and methods described herein can address pitfalls of the EMAR systems and methods known in the art.

Description

Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 MEMBRANELESS ELECTROCHEMICALLY MEDIATED AMINE REGENERATION CELL, SYSTEM, AND METHODS OF USE THEREOF

[0001] This application claims priority to both U.S. Provisional Application No. 63 / 846,773 filed on July 18, 2025, and U.S. Provisional Application No.63 / 703,872 filed on October 04, 2024. The entire contents of each are incorporated herein by reference.

[0002] All patents, patent applications and publications cited herein are hereby incorporated by reference in their entirety. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described and claimed herein.

[0003] This patent disclosure contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the U.S. Patent and Trademark Office patent file or records but otherwise reserves any and all copyright rights. FIELD OF THE INVENTION

[0004] This invention is directed to systems and methods of membraneless electrochemically mediated amine regeneration for carbon capture. BACKGROUND OF THE INVENTION

[0005] The energy transition towards a low-carbon economy depends on the deployment of carbon capture and storage (CCS) technologies across power, transport, and industry sectors. Among these systems, electrochemically mediated amine regeneration (EMAR) has advanced to higher technology readiness levels by indicating continuous CO2capture for extended periods. However, current EMAR systems and methods require cost-prohibitive anion exchange membranes (AEM). SUMMARY OF THE INVENTION

[0006] Aspects of the invention are drawn towards a membraneless electrochemical cell comprising: a power supply; an electrolyte chamber separating two gas diffusion electrodes (GDE), wherein the electrolyte chamber comprises an aqueous absorbent-containing electrolyteDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 solution, wherein one GDE is a cathode gas diffusion electrode (cGDE), and wherein one GDE is an anode gas diffusion electrode (aGDE); a stream gas channel on the exterior of the cGDE, wherein the stream gas channel comprises a stream gas inlet and a stream gas outlet; and a sweep gas channel on the exterior of the aGDE, wherein the sweep gas channel comprises a sweep gas inlet and a sweep gas outlet. In embodiments, the aqueous absorbent-containing electrolyte solution comprises a cupric ion source, an amine source, and a background electrolyte. In embodiments, the background electrolyte comprises sodium sulfate (Na2SO4), potassium sulfate (K2SO4), or a combination thereof; the cupric ion source comprises copper (II) sulfate pentahydrate (CuSO4, 5H2O); the amine source comprises ethylenediamine (EDA), monoethanolamine (MEA), or a combination thereof; or any combination thereof. In embodiments, cupric ion source is present from about 0.1 M to about 0.4 M; the background electrolyte is present from about 0.2 M to about 2.0 M; the amine source is present in a concentration of about 0.5 M to about 1.5 M; or any combination thereof. In embodiments, the GDE comprises a gas diffusion layer (GDL), wherein the GDL comprises a porous current collector adjacent to the gas channel; a microporous layer (MPL), wherein the MPL is adjacent to the GDL or integrated into the GDL; and a copper layer (Cu0) adjacent to the MPL or the GDL with the integrated MPL and interfacing with the electrolyte layer. In embodiments, the porous current collector comprises a carbon fiber composite paper or a carbon cloth; and the MPL comprises a conductive composition, a hydrophobic composition, or a combination thereof. In embodiments, the conductive composition comprises carbon black. In embodiments, the hydrophobic composition comprises polytetrafluoroethylene (PTFE). In embodiments, the copper layer comprises about 0.7 mg / cm2to about 3.3 mg / cm2copper loading. In embodiments, the cell absorbs about 0.01% to about 100% CO2from the stream gas. In embodiments, the cell comprises an absorption capacity of about 0.1 mol CO2 / mol absorbent to about 0.9 mol CO2 / mol absorbent. In embodiments, the cell does not comprise an anionic exchange membrane (AEM), an absorption column, a flash tank, a pump, or any combination thereof.

[0007] Aspects of the disclosure are drawn towards a method of carbon dioxide separation using the membraneless electrochemical cell described herein. In embodiments, the method comprises applying an electric potential to the membraneless electrochemical cell; flowing a stream gas through the stream gas channel on the exterior of the cGDE, thereby absorbing carbon dioxide present in the stream gas into the cathode gas diffusion electrode (cGDE) and into the absorbent- containing electrolyte solution; and flowing a sweep gas through the sweep gas channel on theDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 exterior of the aGDE, thereby removing the carbon dioxide from the electrolyte solution and desorbing the carbon dioxide through the aGDE. In embodiments, the electric potential comprises about 0.5 V to about 1.5 V. In embodiments, the stream gas comprises less than 0.01% to about 100% CO2. In embodiments, the method comprises a CO2 removal efficiency of about 30% to about 100%. In embodiments, the method comprises a current density of about 50 A / m2to about 300 A / m2. In embodiments, the method comprises an energy consumption of about 6kJ / mol CO2to about 250 kJ / mol CO2. In embodiments, the membraneless electrochemical cell operates at a temperature less than 50 degrees Celsius. In embodiments, the membraneless electrochemical cell facilitates the transport of the copper-amine complex and CO2amine complex to their respective electrodes using non-convective forces. In embodiments, the non-convective forces comprise a combination of electric forces and concentration gradients. In embodiments, the membraneless electrochemical cell operates in batch mode. In embodiments, each GDE comprises either a mesh attached assembly or an electrodeposited assembly. In embodiments, the mesh attached assembly comprises a metal mesh mechanically attached to a porous carbon-based substrate. In embodiments, the electrodeposited assembly comprises metal electrodeposited onto the same porous carbon-based substrate.

[0008] Other objects and advantages of this invention will become readily apparent from the ensuing description. BRIEF DESCRIPTION OF THE FIGURES

[0009] FIG.1 shows non-limiting, exemplary schematics of conventional and new membraneless EMAR systems as described herein. Panel A shows the process scheme of the conventional EMAR with a two-compartment electrochemical cell separated by an anion exchange membrane (AEM), illustrated as a dashed line. The system also includes an absorption column, pumps, and a flash tank. Panel B shows conventional EMAR without the AEM. In this configuration, the desorbed CO2 at the anode is reabsorbed by the regenerated absorbent at the cathode, leading to low removal efficiency. Panel C shows developed membraneless EMAR with gas diffusion electrodes (GDEs). On the cathode side, CO2 is absorbed through a gas-breathing interface, where the absorbent is regenerated. The desorbed CO2 at the anode is removed from the electrolyte through a similar gas- breathing GDE and collected using a sweep gas (SG; e.g., water vapor). The carbon-based GDE consists of a copper layer (Cu⁰), a microporous layer (MPL), a gas diffusion layer (GDL), and a porous current collector (CC) facing the gas channel. A photo of the membraneless EMAR unitDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 cell is included. The illustrations depict the use of copper (Cu) as the metal and an amine (Am) as the absorbent.

[0010] FIG. 2 shows non-limiting, exemplary data and schematics indicating the mesh-attached GDE performance. Panel A shows CO2 removal efficiency of the mesh-attached GDEs with three different carbon-based substrates (Toray 060, GDS 230, and GDL 240). Two different mesh sizes, 50x50 and 100x100, were tested. The error bars show the standard deviation of three independent experiments. The inset is a photo of the mesh-attached GDE. Panel B shows a schematic representation of the mesh-attached GDE, illustrating a microscale gap (microgap) between the mesh and the carbon-based substrate. Desorbed CO2at the anode interface is reabsorbed by amine (Am) and hydroxide (OH−), leading to ineffective collection of CO2by the gas channel located at the back of the GDE.

[0011] FIG.3 shows non-limiting, exemplary data and schematics indicating the electrodeposited GDE performance. Panel A shows CO2removal efficiency of electrodeposited GDEs with three different carbon-based substrates (Toray 060, GDS 230, and GDL 240) and various copper loadings. The error bars show the standard deviation of three independent experiments. The dashed line indicates the average efficiency of the mesh-attached GDE. Panel B shows a schematic illustration showing the physical barriers created by both the copper layer and the microporous layer. These barriers facilitate the reabsorption of desorbed CO2 by amine (Am) or hydroxide (OH−). Panel C through Panel F shows SEM images of Toray 060 with copper loadings of (Panel C) 0, (Panel D) 0.7, (Panel E) 1.7, and (Panel F) 3.3 mg / cm2. Panel G – Panel J shows SEM images of GDS 230 with copper loadings of (Panel G) 0, (Panel H) 0.7, (Panel I) 1.7, and (Panel J) 3.3 mg / cm2. Panel K – Panel N shows SEM images of GDL 240 with copper loadings of (Panel K) 0, (Panel L) 0.7, (Panel M) 1.7, and (Panel N) 3.3 mg / cm2. For all SEM images, EDS results are overlaid, with green indicating the presence of carbon, blue for oxygen, and orange for copper.

[0012] FIG. 4 shows non-limiting, exemplary graphs indicating the performance comparison of different GDEs. The current density and energy consumption for carbon capture using the developed membraneless EMAR system were evaluated. The corresponding CO2 removal efficiency (η) values are provided for all developed GDEs and categorized into three groups: Low (η ≤ 50%; red), Medium (50% < η < 75%; orange), and High (η ≥ 75%; green). Panel A shows performance of all mesh-attached GDE assemblies, including mesh sizes of 50×50 and 100×100. Panel B shows performance of all electrodeposited GDEs with different copper loadings. For bothDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 mesh-attached and electrodeposited GDEs, three different carbon-based substrates were used: Toray 060, GDS 230, and GDL 240. Panel C shows comparison of the membraneless EMAR system with the two different GDE configurations against the conventional EMAR in terms of current density and energy consumption.

[0013] FIG. 5 shows non-limiting, exemplary graphs and data indicating the economics of the membraneless EMAR. Purchased equipment cost (PEC) breakdown for (Panel A) the conventional EMAR and (Panel B) the membraneless EMAR. The sliced pie chart illustrates the cost shares of all associated process components, while the donut chart represents the cost shares of the electrochemical cell components. Panel C shows comparison of the levelized cost of carbon capture (LCOCC) for the conventional versus membraneless EMAR. OpEx includes both non- feedstock costs (e.g., labor, on-site feedstock handling, and maintenance) and electricity, while depreciation is considered for CapEx. Panel D shows sensitivity analysis of four key parameters, showing the LCOCC at their associated lower and upper bounds. Cost target analysis for the membraneless EMAR with cell lifetime of 8 years (Panel E) and 12 years (Panel F). The contour plot represents the LCOCC as a function of varying efficiency and current density. The lines indicate LCOCC values of $50, $75, and $100 per tonne CO2, while the circles represent the LCOCC for the developed membraneless EMAR at its current performance metrics.

[0014] FIG. 6 shows non-limiting, exemplary graphs of the optimization of electrolyte composition: Panel A shows background electrolyte and Panel B shows copper concentration. CO2removal efficiency, current density, and energy consumption were used as the three main performance metrics to compare different electrolytes. The error bars indicate the standard deviation from three independent experiments.

[0015] FIG.7 shows a non-limiting, exemplary graph of the optimization of applied potential by monitoring current density and energy consumption. CO2 removal efficiencies are reported above each data point. Applied potentials of 0.25, 0.5, 0.75, 1.0, and 1.25 V were tested, and the steady- state current density (inset) was recorded. Energy consumption was calculated based on the applied potential, current, and the amount of CO2 desorbed.

[0016] FIG.8 shows non-limiting, exemplary photos of the three carbon-based substrates used for GDEs.

[0017] FIG. 9 shows non-limiting, exemplary voltage profiles of the electrodeposition process conducted for varying durations. Panel A shows Toray 060, Panel B shows GDS 230, and PanelDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 C shows GDL 240. Corresponding SEM images for copper loadings of 0, 0.7 (15 minutes of deposition), and 3.3 (60 minutes of deposition) mg / cm2are provided for each substrate

[0018] FIG. 10 shows non-limiting, exemplary SEM images and EDS results. Panel A shows Toray 060, Panel B shows GDS 230, and Panel C shows GDL 240. The SEM images show the gas diffusion layer in all samples, with an MPL present only in GDL 240. The EDS results identified the presence of carbon (C), fluorine (F), and oxygen (O).

[0019] FIG.11 shows non-limiting, exemplary cross-sectional SEM and EDS images and data of Toray 060 with various copper loadings. Panel A shows a loading of 0 mg / cm2, Panel B shows a loading of 0.7 mg / cm2, and Panel C shows a loading of 3.3 mg / cm2. The deposition begins at the surface and gradually builds up on the top layer, creating an increasing physical barrier against CO2 removal.

[0020] FIG. 12 shows a non-limiting, exemplary 3D schematic of the membraneless electrochemical cell, illustrating the EMAR with mesh-attached GDEs. All key components are shown, including the main chamber (electrolyte holder), GDE assembly (including the mesh and carbon substrate), and gas inlet / outlet ports for CO2 absorption and desorption.

[0021] FIG. 13 shows a non-limiting, exemplary current profiles obtained from the 15-minute desorption experiments, illustrating the performance of three different electrodeposited GDEs. Panel A shows Toray 060, Panel B shows GDS 230, and Panel C shows GDL 240. The experiments were performed at room temperature (22°C) by applying a constant potential of 1 V. The current response (I) was recorded during the desorption experiments. The profiles correspond to copper loadings of 1.7 and 2.5 mg / cm2on each GDE substrate.

[0022] FIG.14 shows a non-limiting exemplary titration experimental set up and non-limiting GC analysis. Panel A shows the titration setup used to analyze the CO2content in the liquid phase. Panel B shows GC results of the desorbed CO2 from the electrochemical cell along with the analysis of the headspace gas phase. Results for both Channel A (O2 and N2) and Channel B (CO2 and other gases) are provided.

[0023] FIG. 15 shows non-limiting, exemplary GC and FTIR data. Panel A shows Gas chromatography (GC) analysis of the desorbed gas collected from the anode GDE during the electrochemical experiment. Helium (He) was used as the sweep gas. Panel B shows Fourier Transform Infrared (FTIR) spectra of the electrolyte before and after the desorption experiment,Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 measured in absorbance mode over a wavenumber range of 450–4000 cm–1using an Attenuated Total Reflection (ATR) setup with a diamond crystal.

[0024] FIG.16 shows non-limiting, exemplary photographs of the structural failure of the carbon- based substrates after mesh attachment under different conditions. Panel A shows failure at elevated temperature. Panel B shows failure at elevated pressure (B), highlighting the fragility of the material under these conditions. A 12-ton hydraulic press with two independently controlled heating plates (Panel C) was used for the process.

[0025] FIG.17 shows a non-limiting, exemplary process flow diagram. Panel A shows a diagram for the conventional EMAR system. Panel B shows a diagram for the membraneless EMAR systems.

[0026] FIG. 18 shows non-limiting, exemplary graphs of current density and efficiency. Cost target analysis for the membraneless EMAR for GDE costs of $10 / m2(Panel A) and $5 / m2(Panel B). The lines indicate LCOCC values of $50 and $75 per tonne CO2, while the circles represent the LCOCC for the developed membraneless EMAR at its current performance metrics.

[0027] FIG.19 shows a non-limiting, exemplary schematic of a coupled electrochemical cell of CO2capture and conversion. This diagram illustrates the dual-compartment cell, where (1) represents the capture and concentration compartment, mirroring the membraneless EMAR system, and (2) depicts the conversion compartment, inspired by the state-of-the-art water-fed CO2 electrolyzer utilizing an anion exchange membrane (AEM) and a cation exchange membrane (CEM). A bipolar gas diffusion electrode (GDE) is centrally positioned, with its anodic side facing the capture compartment and its cathodic side facing the conversion compartment. The GDE comprises a microporous layer (MPL), a gas diffusion layer (GDL), and specialized catalysts tailored for either the CO2reduction reaction (CRR) or the oxygen evolution reaction (OER). A porous current collector (CC) is also incorporated within the two GDEs that are connected to the external circuit.

[0028] FIG. 20 shows non-limiting, exemplary graphs of cell optimization data. Panel A shows cell operating voltage over time. Panel B shows flowrate for CO2 over time.

[0029] FIG.21 shows non-limiting, exemplary graphs of long-term performance of optimized cell at 75 mA. Panel A shows voltage changes with the applied current over 50 hours without compensation for Ohmic drop in the cell. Panel B shows CO2flow profiles for both left and rightDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 sides over 50 hours. Panel C shows energetics and efficiency after compensating for solution resistance (1.5 Ω).

[0030] FIG.22 shows non-limiting exemplary graphs of long-term performance of optimized cell at 75 mA zoomed in to a five-hour timeframe. Panel A shows voltage changes with the applied current over 5 hours without compensation for Ohmic drop in the cell. Panel B shows CO2 flow profiles for both left and right sides over 5 hours. Panel C shows energetics and efficiency after compensating for solution resistance (1.5 Ω).

[0031] FIG.23 shows non-limiting, exemplary graphs of electrolyte stability tests. Panel A shows Ion Chromatography data before optimization experiment. Panel B shows Ion Chromatography data after optimization experiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] Detailed descriptions of one or more embodiments are provided herein. It is to be understood, however, that the present invention can be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in any appropriate manner.

[0033] The singular forms “a”, “an” and “the” include plural reference unless the context clearly dictates otherwise. The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and / or the specification can mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0034] Wherever any of the phrases “for example,” “such as,” “including” and the like are used herein, the phrase “and without limitation” is understood to follow unless explicitly stated otherwise. Similarly, “an example,” “exemplary” and the like are understood to be nonlimiting.

[0035] The term “substantially” allows for deviations from the descriptor that do not negatively impact the intended purpose. Descriptive terms are understood to be modified by the term “substantially” even if the word “substantially” is not explicitly recited.

[0036] The terms “comprising” and “including” and “having” and “involving” (and similarly “comprises”, “includes,” “has,” and “involves”) and the like are used interchangeably and have the same meaning. Specifically, each of the terms is defined consistent with the common United States patent law definition of “comprising” and is therefore interpreted to be an open termDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 meaning “at least the following,” and is also interpreted not to exclude additional features, limitations, aspects, etc. Thus, for example, “a process involving steps a, b, and c” means that the process includes at least steps a, b and c. Wherever the terms “a” or “an” are used, “one or more” is understood, unless such interpretation is nonsensical in context.

[0037] As used herein, the term “about” can refer to approximately, roughly, around, or in the region of. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 20 percent up or down (higher or lower).

[0038] As used herein, the term “substantially the same” or “substantially” can refer to variability typical for a particular method is taken into account.

[0039] The terms “sufficient” and “effective”, as used interchangeably herein, can refer to an amount (e.g., mass, volume, dosage, concentration, and / or time period) needed to achieve one or more desired result(s).

[0040] Before explaining at least one embodiment of the disclosure in detail, it is to be understood that the disclosure is not necessarily limited in its application to the details set forth in the following description or exemplified by the examples. The disclosure is capable of other embodiments or of being practiced or carried out in various ways. Other compositions, compounds, methods, features, and advantages of the present disclosure will be or become apparent to one having ordinary skill in the art upon examination of the following drawings, detailed description, and examples. All such additional compositions, compounds, methods, features, and advantages can be included within this description, and be within the scope of the present disclosure.

[0041] Aspects of the disclosure are drawn towards a membraneless electrochemical cell. In embodiments, the membraneless electrochemical cell can comprise a power supply; an electrolyte chamber separating two gas diffusion electrodes (GDE), wherein the electrolyte chamber comprises an aqueous absorbent-containing electrolyte solution, wherein one GDE is a cathode gas diffusion electrode (cGDE), and wherein one GDE is an anode gas diffusion electrode (aGDE); a stream gas channel on the exterior of the cGDE, wherein the stream gas channel comprises a stream gas inlet and a stream gas outlet; and a sweep gas channel on the exterior of the aGDE, wherein the sweep gas channel comprises a sweep gas inlet and a sweep gas outlet.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0042] As used herein, the term “power supply” can refer to a device or system that delivers electrical energy. For example, the power supply can comprise a potentiostat.

[0043] As used herein, the term “gas diffusion electrode” can refer to a porous electrode that facilitates the transport of gas-phase species to and from an electrochemical interface. The GDE can comprise a catalyst or reaction layer where electrochemical reactions occur, a gas diffusion layer (GDL) that allows gas permeability, and a current collector for electron transport. For example, in embodiments of the disclosure, the GDE serves as a gas-breathing interface to facilitate CO₂ absorption at the cathode and CO₂ desorption at the anode, thereby eliminating the need for a membrane in the electrochemical system. In addition, the GDE can comprise hydrophobic coating on the external layer of the GDE (i.e., exposed to the gas phase). In embodiments, the hydrophobic coating can prevent electrolyte leakage into the gas channel and bubbling gas into the electrolyte, ensuring stable operation and maintaining efficient gas-liquid separation. In embodiments, the hydrophobic coating can be applied to the surface and / or integrated into overall material of the MPL, the GDL, or both the MPL and the GDL.

[0044] As used herein, the term “stream gas” can refer to a gas comprising a target gas. For example, the target gas can refer to a gas targeted for removal from a system. In some embodiments, the gas targeted for removal can be a pollutant. In some embodiments, the stream gas can refer to a mixture of gases. In some embodiments, the stream gas can refer to a flue gas. For example, the stream gas can be released by a system after energy exchange or a conversion process. For example, stream gas can refer to combustion gases and / or exhaust gases. In embodiments, the stream gas can comprise nitrogen (N2), carbon dioxide (CO2), carbon monoxide (CO), sulphur oxides (SOx), nitrogen oxides (NOx), oxygen (O2), particulate matter, or any combination thereof. In embodiments, the stream gas described herein can comprise less than about 0.01% to about 100% CO2. For example, the stream gas can comprise about 0.005% to about 100% CO2. For example, the stream gas can comprise less than about 0.005%, about 0.0075%, about 0.001%, about 0.0025%, about 0.005%, about 0.0075%, about 0.01%, about 0.0125%, about 0.015%, about 0.0175%, about 0.02%, about 0.0225%, about 0.025%, about 0.0275%, about 0.03%, about 0.0325%, about 0.035%, about 0.0375%, about 0.04%, about 0.0425%, about 0.045%, about 0.0475%, about 0.05%, about 0.055%, about 0.06%, about 0.07%, about 0.08%, about 0.9%, about 1%, about 1.5%, about 2%, about 2.5%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 12.5%, about 13%,Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 about 14%, about 15%, about 16%, about 17%, about 17.5%,about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 37.5%, about 40%, about 42.5%, about 45%, about 47.5%, about 50%, about 52.5%, about 55%, about 57.5%, about 60%, about 62.5%, about 65%, about 67.5%, about 70%, about 72.5%, about 75%, about 77.5%, about 80%, about 82.5%, about 85%, about 87.5%, about 90%, about 92.5%, about 95%, about 97.5%, about 98%, about 99%, or about 100% CO2.

[0045] As used herein, the term “sweep gas” can refer to a gas introduced into a system to remove or carry away a stream gas. For example, the stream gas can be a mixture of gases comprising a target gas. For example, the stream gas can comprise CO2. In embodiments, the sweep gas can comprise water vapor, argon, nitrogen, helium, or any combination thereof.

[0046] In embodiments, the external layer of the GDE (i.e., exposed to the gas phase) comprises a hydrophobic coating that can prevent electrolyte leakage into the gas channel and gas bubbling into the electrolyte, thereby facilitating stable operation and maintaining efficient gas-liquid separation.

[0047] In embodiments, the aqueous absorbent-containing electrolyte solution can comprise a cupric ion source, an amine source, and a background electrolyte.

[0048] As used herein, the term “background electrolyte” can refer to ions that are not directly involved in the electrochemical reaction but rather are included in the solution conductivity and / or maintaining constant ionic strength. In embodiments, the background electrolyte comprises sodium sulfate (Na2SO4), potassium sulfate (K2SO4), or a combination thereof. In embodiments, the background electrolyte(s) can be present in a concentration of about 0.25 M to about 2.0 M. For example, the background electrolytes can be present in a concentration of about 0.05 M, about 0.075 M, about 0.1 M, about 0.125 M, about 0.15 M, about 0.175 M, about 0.2 M, about 0.225 M, about 0.25 M, about 0.275 M, about 0.3 M, about 0.325 M, about 0.35 M, about 0.375 M, about 0.4 M, about 0.425 M, about 0.45 M, about 0.475 M, about 0.5 M, about 0.525 M, about 0.55 M, about 0.575 M, about 0.6 M, about 0.625 M, about 0.65 M, about 0.675 M, about 0.7 M, about 0.725 M, about 0.75 M ,about 0.775 M, about 0.8 M, about .825 M, about 0.85 M, about 0.875 M, about 0.9 M, about 0.925 M, about 0.95 M, about 0.975 M, about 1.0 M, about 1.025 M, about 1.05 M, about 1.075 M, about 1.1 M, about 1.125 M, about 1.15 M, about 1.175 M, about 1.2 M, about 1.225 M, about 1.25 M, about 1.275 M, about 1.3 M, about 1.325 M, about 1.35 M, aboutDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 1.375 M, about 1.4 M, about 1.425 M, about 1.45 M, about 1.475 M, about 1.5 M, about 1.525 M, about 1.575 M, about 1.6 M, about 1.625 M, about 1.65 M, about 1.7 M, about 1.725 M, about 1.75 M, about 1.8 M, about 1.9 M, or about 2.0 M. In some embodiments, the background electrolyte is present in a concentration of about 1.0 M.

[0049] In embodiments, the cupric ion source is present from about 0.1 M Cu2+to about 0.4 M Cu2+. For example, the cupric ion source is present in about 0.05 M, about 0.075 M, about 0.1 M, about 0.125 M, about 0.15 M, about 0.175 M, about 0.2 M, about 0.225 M, about 0.25 M, about 0.275 M, about 0.3 M, about 0.325 M, about 0.35 M, about 0.375 M, about 0.4 M, about 0.425 M, about 0.45 M, about 0.475 M, about 0.5 M, about 0.525 M, about 0.55 M, about 0.575 M, about 0.6 M, about 0.625 M, about 0.65 M, about 0.675 M, about 0.7 M, about 0.725 M, about 0.75 M ,about 0.775 M, about 0.8 M, about .825 M, about 0.85 M, about 0.875 M, about 0.9 M, about 0.925 M, about 0.95 M, about 0.975 M, or about 1.0 M Cu2+. In embodiments, the cupric ion source can comprise any cupric ion source known in the art. For example, the cupric ion source can comprise copper (II) sulfate pentahydrate (CuSO4, 5H2O). In embodiments, the copper (II) sulfate pentahydrate can be present in a concentration of about 0.1 M Cu2+to about 0.4 M Cu2+.

[0050] In embodiments, the CO2absorbent source can comprise a variety of amines (i.e., amine sources). In embodiments, the amine source can comprise any amine source known in the art. For example, the amine source can comprise diethanolamine (DEA), methyldiethanolamine (MDEA), piperazine, diisopropanolamine (DIPA), aminoethylethanolamine (AEEA), triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AM), ethylenediamine (EDA), monoethanolamine (MEA), or a combination thereof. In embodiments, the amines can be used individually. In embodiments, the amines can be used as a mixture. In some embodiments, the amine source can comprise about 10 / 90 wt.%, about 20 / 80 wt.%, about 30 / 70 wt.%, about 40 / 60 wt.%, about 50 / 50 wt.%, about 60 / 40 wt.%, about 70 / 30 wt.%, about 80 / 20 wt.%, or about 90 / 10 wt.% EDA / MEA. For example, the amines can be in a 50 / 50 wt.% ratio.

[0051] In embodiments, the amine source can be present in a concentration of about 0.5 M to about 1.5 M. For example, the amine source can be present in about 0.225 M, about 0.25 M, about 0.275 M, about 0.3 M, about 0.325 M, about 0.35 M, about 0.375 M, about 0.4 M, about 0.425 M, about 0.45 M, about 0.475 M, about 0.5 M, about 0.525 M, about 0.55 M, about 0.575 M, about 0.6 M, about 0.625 M, about 0.65 M, about 0.675 M, about 0.7 M, about 0.725 M, about 0.75 M ,about 0.775 M, about 0.8 M, about .825 M, about 0.85 M, about 0.875 M, about 0.9 M, about 0.925 M,Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 about 0.95 M, about 0.975 M, about 1.0 M, about 1.025 M, about 1.05 M, about 1.075 M, about 1.1 M, about 1.125 M, about 1.15 M, about 1.175 M, about 1.2 M, about 1.225 M, about 1.25 M, about 1.275 M, about 1.3 M, about 1.325 M, about 1.35 M, about 1.375 M, about 1.4 M, about 1.425 M, about 1.45 M, about 1.475 M, about 1.5 M, about 1.525 M, about 1.575 M, about 1.6 M, about 1.625 M, about 1.65 M, about 1.7 M, about 1.725 M, about 1.75 M, about 1.8 M, about 1.9 M, or about 2.0 M.1 M. In some embodiments, the amine source is present in about 1.0 M.

[0052] In embodiments, the gas diffusion electrodes (GDE) described herein can comprise a porous current collector, a gas diffusion layer (GDL), a microporous layer (MPL), a copper layer (Cu0), or any combination thereof. In some embodiments, the porous current collector and MPL can be distinct layers from the GDL. For example, in some embodiments, the GDL can be disposed between the current collector and the MPL. In some embodiments, the porous current collector, MPL, or a combination thereof can be integrated into the GDL. For example, the porous current collector can be integrated into the GDL as one layer. In some embodiments, the MPL can be integrated into the GDL or applied to (e.g., coated with) the GDL. In some embodiments, the GDL does not include an MPL.

[0053] As used herein, the term “porous current collector” can refer to a porous, conductive composition that can collect and transport electrons. The porous structure can enhance surface area and facilitate gas penetration. In embodiments, the porous current collector can be selected from a carbon-based current collector, a foam-type current collector, a mesh-type current collector, a conductive polymer composite, or any combination thereof. In embodiments, the carbon-based current collector can comprise carbon fiber composite paper or a carbon cloth. For example, the carbon fiber composite paper can comprise a carbon fiber paper with or without a hydrophobic coating, a carbon fiber composite paper with or without a micro-porous layer coating, or any combination thereof (see, e.g., Toray 060 (thickness 190 μm, Fuel Cell Store), GDS 230 (thickness 230 μm, Fuel Cell Store), and GDL 240 (thickness 240 μm, Fuel Cell Store)). In some embodiments, the thickness of the carbon fiber paper can comprise about 100 μm to about 300 μm.

[0054] As used herein, the term “gas diffusion layer” can refer to a porous, conductive substrate that facilitates the transport of gases to and from the catalyst or reaction layer while providing electrical conductivity and mechanical support within a gas diffusion electrode (GDE). In embodiments, the gas diffusion layer (GDL) comprises a carbon-based substrate, including but not limited to a carbon fiber paper or a carbon cloth, with or without a microporous layer (MPL) andDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 with or without a hydrophobic treatment (e.g., polytetrafluoroethylene (PTFE)) to optimize gas permeability, hydrophobicity, and mechanical stability. The GDL facilitates efficient gas exchange while preventing electrolyte flooding, thereby enhancing the performance of the electrochemical system. In some embodiments, the MPL and hydrophobic layer can be separate layers from the GDL. In some embodiments, the MPL, the hydrophobic layer, or both the MPL and hydrophobic layer can be integrated into the GDL.

[0055] As used herein, the term “microporous layer” can refer to a porous layer that can enhance gas transport, control wettability, prevent electrolyte flooding, or any combination thereof. In embodiments, the MPL can be applied to a gas diffusion layer (GDL). In some embodiments, the MPL can be integrated into the GDL. In embodiments, the microporous layer can comprise finely dispersed carbon black or similar conductive materials combined with a hydrophobic binder, such as polytetrafluoroethylene (PTFE), to optimize gas permeability while maintaining structural integrity. In some embodiments, the MPL can comprise only a conductive composition. In some embodiments, the MPL can comprise only a hydrophobic composition. In some embodiments, MPL can comprise about 0.1%, about 0.25%, about 0.5%, about 1%, about 1.5%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 17.5% about 20%, about 22.5%, about 25%, about 27.5%, about 30%, about 32.5%, about 35%, about 37.5%, about 40%, about 42.5%, about 45%, about 47.5%, about 50%, about 52.5%, about 55%, about 57.5%, about 60%, about 62.5%, about 65%, about 67.5%, about 70%, about 72.5%, about 75%, about 77.5%, about 80%, about 82.5%, about 85%, about 87.5%, about 90%, about 92.5%, about 95%, or about 100% of a hydrophobic composition. In embodiments, the microporous layer can be integrated with the GDL to improve electrochemical performance by facilitating gas diffusion to the reaction sites while minimizing mass transport resistance and unwanted liquid penetration.

[0056] In embodiments, the porous current collector is adjacent to the gas channel. In embodiments, the GDL is adjacent to the porous current collector. In embodiments, the microporous layer (MPL) is adjacent to the gas diffusion layer. In embodiments, the copper layer (Cu0) can be adjacent to the microporous layer and interfacing with the electrolyte later. For example, in a non-limiting, exemplary embodiments, the layers of the GDE can be arranged as seen in Fig. 1 panel C. In embodiments, the MPL can be integrated into the GDL. In some embodiments, the GDL does not comprise and integrated MPL or an adjacent MPL.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0057] As used herein, the term “copper loading” can refer to the mass of copper deposited, coated, or embedded onto a substrate or within a structure. In embodiments, the copper layer can comprise about 0.25 to about 10.0 mg / cm2copper loading. For example, the copper loading can comprise about 0.25 mg / cm2, about 0.3 mg / cm2, about 0.4 mg / cm2, about 0.5 mg / cm2, about 0.6 mg / cm2, about 0.7 mg / cm2, about 0.8 mg / cm2, about 0.9 mg / cm2, about 1.0 mg / cm2, about 1.1 mg / cm2, about 1.2 mg / cm2, about 1.3 mg / cm2, about 1.4 mg / cm2, about 1.5 mg / cm2, about 1.6 mg / cm2, about 1.7 mg / cm2, about 1.8 mg / cm2, about 1.9 mg / cm2, about 2.0 mg / cm2, about 2.1 mg / cm2, about 2.2 mg / cm2, about 2.3 mg / cm2, about 2.4 mg / cm2, about 2.5 mg / cm2, about 2.6 mg / cm2, about 2.7 mg / cm2, about 2.8 mg / cm2, about 2.9 mg / cm2, about 3.0 mg / cm2, about 3.1 mg / cm2, about 3.2 mg / cm2, about 3.3 mg / cm2, about 3.4 mg / cm2, about 3.5 mg / cm2, about 3.6 mg / cm2, about 3.7 mg / cm2, about 3.8 mg / cm2, about 3.9 mg / cm2, about 4.0 mg / cm2, about 4.1 mg / cm2, about 4.2 mg / cm2, about 4.3 mg / cm2, about 4.4 mg / cm2, about 4.5 mg / cm2, about 5.0 mg / cm2, about 5.25 mg / cm2, about 5.5 mg / cm2, about 5.75 mg / cm2, about 6.0 mg / cm2,, about 6.25 mg / cm2, about 6.5 mg / cm2, about 6.75 mg / cm2, about 7.0 mg / cm2, about 7.25 mg / cm2, about 7.5 mg / cm2, about 7.75 mg / cm2, about 8.0 mg / cm2, about 8.25 mg / cm2, about 8.5 mg / cm2, about 8.75 mg / cm2, about 9.0 mg / cm2, about 9.25 mg / cm2, about 9.5 mg / cm2, about 9.75 mg / cm2, or about 10.0 mg / cm2. In embodiments, the copper layer can comprise copper loading of about 0.7 to about 3.3 mg / cm2. For example, the copper layer can comprise about 1.7 mg / cm2copper loading.

[0058] In embodiments, the cell described herein can absorb about 0.01% to about 100% CO2from the stream gas. For example, the cell described herein can absorb 0.1%, about 0.25%, about 0.5%, about 1%, about 1.5%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 17.5% about 20%, about 22.5%, about 25%, about 27.5%, about 30%, about 32.5%, about 35%, about 37.5%, about 40%, about 42.5%, about 45%, about 47.5%, about 50%, about 52.5%, about 55%, about 57.5%, about 60%, about 62.5%, about 65%, about 67.5%, about 70%, about 72.5%, about 75%, about 77.5%, about 80%, about 82.5%, about 85%, about 87.5%, about 90%, about 92.5%, about 95%, or about 100% CO2 from the stream gas.

[0059] In embodiments, the cell comprises an absorption capacity of about 0.1 mol CO2 / mol absorbent to about 0.99 mol CO2 / mol absorbent. In embodiments, the cell comprises an absorption capacity less than about 0.6 mol CO2 / mol absorbent. In embodiments, the cell comprises an absorption capacity of at least 0.6 mol CO2 / mol absorbent. For example, the cell can compriseDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 about 0.1 mol CO2 / mol absorbent, about 0.2 mol CO2 / mol absorbent, about 0.3 mol CO2 / mol absorbent, about 0.4 mol CO2 / mol absorbent, about 0.5 mol CO2 / mol absorbent, about 0.6 mol CO2 / mol absorbent, about 0.7 mol CO2 / mol absorbent, about 0.8 mol CO2 / mol absorbent, about 0.9 mol CO2 / mol absorbent, about 0.95 mol CO2 / mol absorbent, about 0.99 mol CO2 / mol absorbent, or about 1 mol CO2 / mol absorbent.

[0060] In embodiments, the electrochemical cell described herein does not comprise an anionic exchange membrane (AEM), an absorption column, a flash tank, a pump, or any combination thereof. As used herein, the term “anionic exchange membrane” can refer to a membrane that allows selective transport of anions while blocking other non-anionic substances (e.g., cations, gases, etc.). Anionic exchange membranes can be cost prohibitive. Moreover, incorporating an anionic exchange membrane, absorption column, a flask tank, a pump, or any combination thereof can increase the cost, the complexity of the operation, and the system footprint. Therefore, a system that does not require one or any combination of these components can be advantageous.

[0061] Aspects of the disclosure are drawn towards methods of carbon dioxide separation using the membraneless electrochemical cell described herein. In embodiments, the method of using the membraneless electrochemical cell described herein for carbon dioxide separation can comprise: CO₂ absorption, electrochemical regeneration, and CO₂ desorption. For example, in operation, a stream gas comprising CO₂ flows across the exterior of the cathode gas diffusion electrode (cGDE), where CO₂ is selectively absorbed into the electrolyte. The absorbed CO₂ forms a complex with the electrochemically active species in the electrolyte. Upon applying an electric potential, the electrochemical reaction facilitates the regeneration of the absorbent, enabling the desorption of CO₂ at the anode gas diffusion electrode (aGDE). A sweep gas is introduced on the exterior of the aGDE to carry away the desorbed CO₂ for collection or further processing. This membraneless design simplifies the gas-liquid separation process, eliminates the need for ion- exchange membranes, and improves operational efficiency.

[0062] In embodiments, method of using the membraneless electrochemical cell and / or cell described herein can comprise applying an electric potential to the membraneless electrochemical cell; flowing a stream gas through the stream gas channel on the exterior of the cGDE, thereby absorbing carbon dioxide present in the stream gas into the cathode gas diffusion electrode (cGDE) and into the absorbent-containing electrolyte solution; and flowing a sweep gas through the sweepDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 gas channel on the exterior of the a GDE, thereby removing the carbon dioxide from the electrolyte solution and desorbing the carbon dioxide through the aGDE. In embodiments, the electric potential can comprise about 0.25 V to about 2.0 V. For example, the electric potential can comprise about 0.25 V, about 0.3 V, about 0.4 V, about 0.5 V, about 0.6 V, about 0.7 V, about 0.8 V, about 0.9 V, about 1.0 V, about 1.1 V, about 1.2 V, about 1.3 V, about 1.4 V, about 1.5 V, about 1.6 V, about 1.7 V, about 1.8 V, about 1.9 V, or about 2.0 V. In some exemplary embodiments, the electric potential comprises about 1.0 V.

[0063] As used herein, the term “CO2 removal efficiency” can refer to the ratio of the theoretically expected CO₂ removal, based on the current and electrochemical reaction stoichiometry, to the actual amount of CO₂ collected at the gas diffusion electrode (GDE). This efficiency metric accounts for losses due to mass transport limitations, side reactions, and operational conditions. In embodiments, CO₂ removal efficiency can be influenced by factors such as electrolyte composition, applied potential, gas diffusion properties, and electrode surface characteristics. This efficiency can be determined using a combination of electrochemical measurements and gas-phase analysis techniques as known in the art.

[0064] In embodiments, the method and / or cell described herein can comprise a CO2removal efficiency of less than 30% to about 100%. For example, the CO2removal efficiency can comprise about 10%, about 15%, about 20%, about 25%, about 30%, about 32%, about 35%, about 37%, about 40%, about 42%, about 45%, about 47%, about 50%, about 52%, about 55%, about 57%, about 60%, about 62%, about 65%, about 67%, about 70%, about 72%, about 75%, about 77%, about 80%, about 82%, about 85%, about 87%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 97%, about 98%, about 99%, or about 100%.

[0065] As used herein, the term “current density” can refer to a measure of electric current per unit area. In other words, the current density can refer to the concentration of current. This can reflect the carbon capture rate as the current will be consumed to either absorb on the cathode or desorb from the anode. In embodiments, the method and / or cell described herein has a current density of about 50 A / m2to about 300 A / m2. For example, the current density can comprise about 125 A / m2to about 185 A / m2. For example, the method described herein has a current density of about 25 A / m2, about 50 A / m2, about 75 A / m2, A / m2about 100 A / m2, about 110 A / m2, about 120 A / m2, about 125 A / m2, about 130 A / m2, about 135 A / m2, about 145 A / m2, about 150 A / m2, about 155 A / m2, about 160 A / m2, about 165 A / m2, about 170 A / m2, about 175 A / m2, about 180 A / m2, aboutDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 185 A / m2, about 190 A / m2, about 200 A / m2, about 205 A / m2, about 210 A / m2, about 215 A / m2, about 220 A / m2, about 225 A / m2, about 230 A / m2, about 235 A / m2, about 240 A / m2, about 245 A / m2, about 250 A / m2. about 275A / m2, about 290 A / m2, about 300 A / m2, or about 325 A / m2.

[0066] In embodiments, the method and / or cell described herein can comprise an energy consumption of about 6.0 kJ / mol CO2 to about 250 kJ / mol CO2. In embodiments, the method can comprise an energy consumption of about 6.0 kJ / mol CO2, about 10 kJ / mol CO2, about 15 kJ / mol CO230 kJ / mol CO2, about 20 kJ / mol CO2, about 25 kJ / mol CO2, about 30 kJ / mol CO2, about 35 kJ / mol CO2, about 40 kJ / mol CO2, about 45 kJ / mol CO2, about 50 kJ / mol CO2, about 55 kJ / mol CO2, about 60 kJ / mol CO2, about 65 kJ / mol CO2, about 70 kJ / mol CO2, about 75 kJ / mol CO2, about 80 kJ / mol CO2, about 85 kJ / mol CO2, about 90 kJ / mol CO2, about 95 kJ / mol CO2, about 100 kJ / mol CO2, about 105 kJ / mol CO2, about 110 kJ / mol CO2, about 115 kJ / mol CO2, about 120 kJ / mol CO2, about 125 kJ / mol CO2, about 130 kJ / mol CO2, about 135 kJ / mol CO2, about 140 kJ / mol CO2, about 145 kJ / mol CO2, about 150 kJ / mol CO2, about 155 kJ / mol CO2, about 160 kJ / mol CO2, about 165 kJ / mol CO2, about 170 kJ / mol CO2, about 175 kJ / mol CO2, about 180 kJ / mol CO2, about 185 kJ / mol CO2, about 190 kJ / mol CO2, about 195 kJ / mol CO2, about 200 kJ / mol CO2, about 205 kJ / mol CO2, about 210 kJ / mol CO2, about 215 kJ / mol CO2, about 220 kJ / mol CO2, about 225 kJ / mol CO2, about 230 kJ / mol CO2, about 235 kJ / mol CO2, about 240 kJ / mol CO2, about 245 kJ / mol CO2, or about 250 kJ / mol CO2. For example, the method and / or cell described herein can comprise an energy consumption of about 60 kJ / mol CO2.

[0067] In embodiments, the method and / or cell described herein can operate at a temperature less than about 50°C. This means that the method and cell described herein can have a lower energy requirement, lower (negligible) rate of amine degradation, and easier operation of the process compared to methods and cells known in the art. For example, the method and / or cell described herein can operate at about 15°C, about 17°C, about 20°C, about 22°C, about 25°C, about 27°C, about 30°C, about 32°C, about 35°C, about 40°C, about 45°C, or about 50°C.

[0068] In embodiments, the method and / or cell described herein can facilitate the transport of the complexes described herein via non-convective forces. In embodiments, the electrochemical cell and method described herein can facilitate the transport of the copper-amine complex and the CO2- amine complex to their respective electrodes using non-convective forces. For example, the non- convective forces can comprise electric forces, concentration gradients, or a combination thereof.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0069] In embodiments, the electrolyte of the method and / or cell described herein can be operated in batch mode. As used herein, “batch mode” can refer to a method of operation where a fixed quantity of reactants or materials are processed in a closed system over a finite period of time. For example, in the method described herein, the reactants and materials operated in batch mode can be in reference to the electrolyte. In other words, in embodiments, the electrolyte can be processed in batch mode while the system continuously captures CO2. In embodiments, the electrolyte methods and cells described herein can be operated in a closed-loop continuous process if higher rates of species mass transport are required.

[0070] In embodiments, the method and / or cell described herein comprises either a mesh attached assembly or an electrodeposited assembly. Advantages of the mesh-attached GDEs can comprise increased current density, which reflects the carbon capture rate. Advantages of electrodeposited GDEs can comprise increased CO2 removal efficiency and, in some embodiments, decreased energy consumption. These differences can be attributed to the structural and morphological characteristics of the substrates.

[0071] In embodiments, the mesh-attached GDEs can be fabricated by mechanically pressing a conductive material mesh onto a substrate. For example, the conductive material can comprise copper and the substrate can comprise a carbon-based substrate, including but not limited to carbon fiber paper. In embodiments, the mesh sizes can be selected to alter performance. For example, the 50x50 mesh exhibited better performance compared to the 100x100 mesh.

[0072] In embodiments, the electrodeposited GDEs can be prepared by depositing a conductive material on a substrate. For example, the electrodeposited GDEs can be prepared by depositing copper on carbon-based substrates, e.g., carbon fiber paper. The microgap present in the mesh- attached GDEs is inherently eliminated in the electrodeposited GDE assembly, as the conductive material is directly deposited onto the surface of the substrate. EXAMPLES

[0073] Examples are provided below to facilitate a more complete understanding of the invention. The following examples illustrate the exemplary modes of making and practicing the invention. However, the scope of the invention is not limited to specific embodiments disclosed in these Examples, which are for purposes of illustration only, since alternative methods can be utilized to obtain similar results.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 EXAMPLE 1

[0074] A Membraneless Electrochemically Mediated Amine Regeneration for Carbon Capture

[0075] Electrochemical carbon capture (ECC) processes offer efficient, scalable, and modular alternatives to conventional thermal-based methods. Among ECCs, electrochemically mediated amine regeneration (EMAR) reached higher technology readiness levels, moving from small-scale laboratory studies toward pilot-scale implementations. Previous EMAR systems rely on ion- selective membranes, which contribute significantly to the cost and present challenges for long- term operation. This study presents a membraneless EMAR system by fundamentally redesigning the process configuration and using gas diffusion electrodes (GDEs) as both the anode and cathode. This setup eliminates the membrane and the need for additional equipment such as the absorption column, flash tank, and pumps, significantly reducing the process footprint and simplifying the flow diagram. Two GDE configurations, mesh-attached and electrodeposited, are tested and compared in terms of CO2 removal efficiency, current density, and energy consumption. Electrodeposited GDEs achieve CO2removal efficiencies above 90% with energy consumption as low as 60 kJ / mol CO2. A techno-economic analysis estimates a levelized cost of capture of ~$70 / tonneCO2, compared to $137 / tonneCO2 for conventional EMAR. Further improvements in current density and removal efficiency can allow costs below $50 / tonneCO2. These results indicate that the membraneless EMAR can be an approach for cost-effective and scalable point-source carbon capture.

[0076] INTRODUCTION

[0077] The most recent Intergovernmental Panel on Climate Change (IPCC) Assessment Report highlighted the key role of carbon capture in climate change mitigation [1]. Electrochemical carbon capture (ECC) processes are rapidly emerging as an alternative to conventional thermally driven amine scrubbing for carbon capture, effectively addressing several challenges of conventional processes, such as high energy requirements for separation and significant absorbent degradation [2-4]. ECC systems also offer inherent advantages of electrochemical technologies, including high efficiency, modularity, ease of retrofitting, and scalability [2, 5]. ECC processes have been successfully implemented for carbon dioxide (CO2) separation from point sources [6, 7], direct air capture (DAC) [8, 9], and, most recently, from seawater [10, 11].Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0078] Depending on how redox reactions are involved, ECCs can be categorized into four broad groups [2]: (1) electrochemical generation of nucleophiles [12-15], (2) electrochemical modulation of proton concentration (also known as pH-swing processes) [16-20], (3) electrochemical capacitive adsorption [21-23], and (4) electrochemically mediated amine regeneration [24-26]. Additionally, some earlier-stage electrochemically based systems are emerging, such as electrochemical mineralization by direct amine–CO2reduction [27, 28]. Among these systems, electrochemically mediated amine regeneration (EMAR) has advanced to higher technology readiness levels; it has progressed from small-scale laboratory settings

[0024] to pilot-scale implementations, demonstrating continuous CO2capture for extended periods nearing one week

[0025] .

[0079] The EMAR process operates similarly to conventional amine-based thermal approaches, but instead of using a high-temperature scrubbing stage (typically at 120°C), it employs a two- compartment electrochemical cell that operates at low to moderate temperatures (<50°C). In this process, CO2 is separated through chemical reactions in the absorption column. The CO2-rich solution is then directed to the anode compartment of the electrochemical desorption unit, where the oxidation of the metal electrode and its subsequent complexation reaction with the absorbent releases the captured CO2. This stream is then sent to a flash tank for CO2removal and subsequently to the cathode for absorbent regeneration, where the metal center of the metal- absorbent complex is plated back onto the electrode. The CO2-lean stream is then returned to the absorption column for reuse (Figure 1 panel A).

[0080] Several fundamental and practical aspects of the EMAR process were recently investigated. Various absorbent chemistries, including different amines and ammonia, were tested [29-32], and different additives [33, 34] and electrode configurations were suggested [35, 36]. Key metrics such as energy consumption, CO2 separation efficiency, and durability were monitored and optimized. Additionally, detailed thermodynamic analyses were conducted across a wide range of operating conditions [37-42]. Despite these advancements, little to no attention has been given to modifying the process configuration (i.e., developing alternative configurations) and the anion exchange membrane (AEM) that separates the anode and cathode compartments. All previous studies have used the same configuration with an AEM, as illustrated in Figure 1 panel A.

[0081] A recent techno-economic analysis (TEA) of the EMAR process aimed to identify the capital expenditure (CapEx) required for components of the scaled-up process, including theDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 electrochemical unit (electrodes, electrolyte, and AEM) and process equipment (such as compressors, pumps, condenser, etc.)

[0043] . The results indicated that the AEM significantly contributed to the overall CapEx, with the cost of the membrane largely dictating the total levelized cost of carbon capture. The function of the membrane in EMAR differs from that in other electrochemical systems, such as flow batteries. In a flow battery, an ion-selective membrane serves as a separator between the individual species of each electrolyte, ensuring that the redox species remain in their corresponding electrolyte tank

[0044] . However, in EMAR, the AEM is essential for the efficient desorption of CO2 in the anode chamber. If the membrane is removed (Figure 1 panel B), the desorbed CO2on the anode side would be reabsorbed by the regenerated amine on the cathode, resulting in the return of a CO2-rich stream to the absorption column, instead of the intended CO2-lean stream (as shown in Figure 1 panel A). Thus, with the current EMAR configuration, removing the membrane would lead to a critically low cyclic capture capacity and desorption efficiency. Re-defining the EMAR configuration with the overall aim of eliminating the membrane while maintaining high desorption efficiency is necessary and offers substantial economic incentives, given the considerable cost of AEMs on the CapEx and capture cost.

[0082] In this study, we developed a membraneless EMAR system by fundamentally re-designing the process configuration. A gas diffusion electrode (GDE), serving as a gas-breathing interface, was used as the anode to efficiently remove the desorbed CO2 from the electrolyte before it can be reabsorbed in the cathode compartment. The innovation described herein can eliminate the need for a membrane while maintaining high desorption efficiency. Additionally, a similar GDE was employed as the cathode, providing a gas-breathing interface for the absorption of CO2 from the gas mixture (e.g., stream gas), thereby logically eliminating the need for a separate absorption column. The system operates in a flow-by mode, where the stream gas flows parallel to the external surface of the GDEs. At the cathode, CO2 is selectively absorbed into the amine solution, while at the anode, a separate sweeping gas facilitates the removal of desorbed CO2. This selective absorption of CO2, rather than other gases present in the stream gas (such as N2and O2), is primarily driven by the high chemical affinity between the amine and CO2 at the electrode interface, where the amine is continuously regenerated. Maintaining an optimized flow rate of the stream gas can ensure sufficient CO2absorption while minimizing both unabsorbed CO2and the intrusion of other gases into the electrolyte. In addition, the hydrophobic coating on the external layer of the GDE (which is exposed to the gas phase) prevents electrolyte leakage into the gasDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 channel and bubbling gas into the electrolyte, ensuring stable operation and maintaining efficient gas-liquid separation. In some embodiments, the GDE configuration described herein can be similar to those used in other electrochemical systems such as fuel cells [45, 46], air-breathing batteries [47-49], and CO2 reduction cells [50-52], which utilize gas-liquid interfaces to facilitate efficient mass transfer.

[0083] Unlike the conventional EMAR process, which mainly relies on convection for the mass transfer of various species, the new membraneless configuration relies on diffusion and migration. The transport of the copper-amine complex (Cu(EDA)22+(aq)) and EDA-CO2 (aq) complexes to their respective electrodes is facilitated by a combination of electric forces (migration) and concentration gradients (diffusion). The cationic copper-amine complex is driven toward the cathode by the electric field, while the concentration gradient across the electrochemical cell promotes the diffusion of EDA-CO2 (aq) towards the anode. These transport mechanisms are common in other electrochemical systems, such as thermochemical galvanic cells [53, 54], microbial fuel cells [55, 56], and concentration cells [57, 58], where species migrate and diffuse under non-convective forces. As a result, the new system can operate in batch mode, eliminating the need for pumps to circulate the electrolyte (Figure 1 panel C). Overall, the new design not only eliminates the membrane as a major CapEx component but also removes other process equipment, including the absorption column, flash tank, and pumps, which collectively contributed approximately 40% of the CapEx of the conventional EMAR

[0043] . This streamlined design results in simpler configuration and operation and a significantly smaller footprint.

[0084] Two types of GDE assemblies were developed: the "mesh-attached GDE," where a metal mesh is mechanically attached to a porous carbon-based substrate with a hydrophilic layer facing the electrolyte and a hydrophobic layer on the back, and the "electrodeposited GDE," where the metal is electrodeposited onto the same porous carbon-based substrate. The mesh-attached GDE is inspired by the conventional EMAR configuration, where a pure metal electrode is used, while the electrodeposited GDE is inspired by GDE-based electrochemical systems, such as those developed for CO2 reduction

[0059] or air-breathing batteries

[0060] . For all experiments, copper was used as the metal, and ethylenediamine as the absorbent, a combination that has been established as the benchmark for the EMAR process [25, 26].

[0085] An exciting aspect of this disclosure is the development of a membraneless system with high removal efficiency at high current density and low energy consumption. The energyDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 consumption refers to the electrical work required to drive the carbon capture process. These metrics were evaluated to optimize the GDE assembly fabrication parameters as well as the operational parameters. Finally, a TEA was conducted to evaluate the economic performance and the levelized cost of carbon capture of the developed membraneless system in comparison to the conventional membrane-based EMAR process.

[0086] MATERIALS AND METHODS

[0087] Materials

[0088] The electrolyte solution used in all experiments included the following chemicals: 0.25 M copper (II) sulfate pentahydrate (CuSO4·5H2O; 98% purity, Sigma Aldrich) as the initial source of cupric ions (Cu2+), 1 M ethylenediamine (EDA; Sigma Aldrich) as the amine absorbent, and 0.5 M sodium sulfate (Na2SO4; purity > 99.0%, Sigma Aldrich) as a background electrolyte to enhance the electrical conductivity of the solutions. All of the solutions were prepared using deionized water with a resistivity greater than 18 MΩ·cm. The chosen concentrations of cupric ions and background electrolytes were based on an optimization study, the details of which are described herein.

[0089] Three types of carbon-based substrates were used to provide gas diffusion media for the GDEs to facilitate the removal of desorbed CO2. The employed substrates were Toray 060 (thickness 190 μm, Fuel Cell Store), GDS 230 (thickness 230 μm, Fuel Cell Store), and GDL 240 (thickness 240 μm, Fuel Cell Store). All three carbon-based substrates were made of carbon fiber paper; however, structurally, only GDL 240 was coated with carbon black as a microporous layer (MPL). Both Toray 060 and GDL 240 were wet-proofed with a standard 5% polytetrafluoroethylene (PTFE) layer. Additional information about the substrates is provided herein.

[0090] GDE Fabrication

[0091] Two different GDE assemblies were fabricated, both with a projected surface area of 3.14 cm2: mesh-attached and electrodeposited. The mesh-attached GDEs were fabricated by mechanically pressing a copper mesh (with a mesh size of 50x50 or 100x100; McMaster Carr) onto one of the three carbon-based substrates. For GDL 240, the mesh was attached to the MPL side.

[0092] The electrodeposited GDEs were prepared by electrodepositing copper from a copper bath, inspired by the established industrial copper plating process [71, 72]. A two-electrode cell withDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 carbon-based substrates as the cathode and a sacrificial copper anode was employed for this purpose. The electrolyte consisted of 0.25 M CuSO4 (as the copper source) and 0.5 M Na2SO4 (as the background electrolyte). To enhance bulk mass transport, the electrolyte was continuously stirred at 220 rpm. A constant current of 50 mA was applied for varying time periods (15, 22.5, 30, 45, and 60 minutes), resulting in copper loadings of 0.7, 1.2, 1.7, 2.5, and 3.3 mg / cm2. Copper loading was confirmed by measuring the electrode mass before and after deposition, and the measured values closely matched the theoretical values based on the charge transferred, confirming the high efficiency of the electrodeposition process. Further details on the electrodeposition experiments are provided herein.

[0093] Characterization Techniques

[0094] Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to study the morphological characteristics of the fabricated GDEs. Samples were prepared by cutting them into small circles (5 mm diameter) and attaching them to SEM (Axia ChemiSE, 30kV accelerating voltage, ThermoScientific) sample holders using conductive carbon tape. All samples were examined at 200X magnification with a working distance of ~10 mm from the detectors. EDS analysis was subsequently conducted on the same samples by activating the integrated detector through the software interface. To further inspect the fabricated GDEs, cross- sectional SEM and EDS analyses were conducted by vertically placing small slices of the samples on the sample holder. The cross-sectional SEM and EDS results for the three carbon-based substrates are provided herein. These results confirmed the layer compositions and structures of the substrates used.

[0095] Electrochemical Testing

[0096] A batch two-electrode cell was designed and fabricated for testing and operating the membraneless configuration of the EMAR process at the lab scale. It comprised a main cylindrical chamber holding 4 mL of electrolyte and two side endplates having central circular notches (20 mm diameter) for CO2absorption and desorption. The end plates also feature small inlet and outlet ports on the sides to introduce either the simulated flue gas (i.e., stream gas) (15% CO2, 7% O2, 78% N2) on the cathodic side or sweep water vapor on the anodic side, which facilitates the removal of CO2bubbles from the electrode surface. More details of the developed cell are provided herein.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0097] To conduct the desorption experiment, the electrodes were polarized at 1 V using a potentiostat (VMP-300; Biologic) for 15 minutes. The desorption experiments were conducted at room temperature (set at 22°C) using the chronoamperometry technique with a potentiostat (VMP- 300; Biologic), applying a potential of 1 V for 15 minutes. This potential was determined to be the optimal value for the operation of the process. This experimental duration was also sufficient to observe steady-state current density values and stable CO2desorption rates. This initiated the anodic reaction, leading to CO2desorption, and the cathodic reaction, regenerating the absorbent for further CO2 absorption from the simulated flue gas. The current response of the system (I) was recorded using the built-in software (EC-Lab; Biologic), and all the experiments were conducted at room temperature (set at 22°C). The current profiles (I vs. t) for the 15-minute desorption experiments are provided herein.

[0098] CO2 removal efficiency (η; %) was rigorously quantified by measuring the amount of CO2 collected by the anode GDE (∆n_(experimental)) and comparing it to the theoretically expected desorption amount (〖∆n〗_(theoretical); Eqn. 1). The experimental desorption was measured using an acid titration method, ensuring accurate measurement of CO2volume by displacement in a U-shaped manometer. The purity of the desorbed CO2 was validated using gas chromatography (GC), confirming nearly 100% purity. Further details on the titration method and GC analysis are provided herein. The theoretical desorption was calculated based on the charge transferred during the experiment (Q; C) and the stoichiometric ratio of electrons to CO2, which is 1:1

[0025] —meaning that the transfer of one mole of electrons theoretically results in the desorption of one mole of CO2 (Eqn.2). (1)(2)ensure the reliability and long-term applicability of the membraneless EMAR system, the chemical stability of the electrolyte—particularly the EDA amine—was thoroughly evaluated. Both the gas and liquid phases were analyzed to detect any potential degradation products. GC analyzed the composition of the desorbed gas, while Fourier Transform Infrared (FTIR) spectroscopy was used to assess changes in the liquid phase. The results confirmed no detectable degradation products inDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 either phase, indicating high electrolyte stability under the tested conditions. Detailed procedures and results of these analyses are provided herein.

[0099] Finally, the energy consumption for CO2desorption (W; kJ / mol CO2) was calculated as: ∫^^^^^^^^ = 0 ^^^^ ^^^^ ^^^^^^^^∆^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^(3)law efficiency as a standardized matrix for carbon capture techniques

[0073] are also provided herein.

[0100] Techno-Economic Analysis (TEA)

[0101] Process Design.

[0102] A TEA was conducted to compare the costs of carbon capture using the developed membraneless EMAR and a conventional membrane-based system. The membraneless EMAR operates with a simplified one-compartment configuration, combining CO2 absorption and desorption in a single electrochemical unit. This eliminates several pieces of equipment, such as the absorption column, several pumps, and a flash tank, which are necessary for conventional EMAR. The reduction in equipment results in significant simplification of the process and reduces the capital investment. Further details of the process design and flow diagrams for both systems are provided herein.

[0103] Levelized Cost of Carbon Capture.

[0104] The Levelized Cost of Carbon Capture (LCOCC) was calculated for both systems to assess their overall economic viability. The TEA model considered a scaled-up carbon capture facility integrated with a 550 MWe coal-fired power plant based on the National Energy Technology Laboratory (NETL) reference model, with annual CO2 emissions of 3.1 Mtonne [43, 74]. All the process and economic parameters and assumptions used for TEA are summarized in Tables 3 and 4.

[0105] Capital and operating expenditures were analyzed to estimate LCOCC and identify the major cost contributors. Capital expenditures (CapEx) were mainly driven by the purchased equipment cost (PEC), which was divided into process and electrochemical components. The former was estimated based on sizing and data reported for an EDA-based carbon capture unit [43, 75], and the latter was estimated based on a scaled-up plan for the EMAR electrochemicalDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 modules. The calculated PEC for electrochemical and process equipment in both EMAR configurations are provided in Tables 6 and 8.

[0106] CapEx was then calculated by taking depreciation into account, using the capital recovery factor to estimate the annual depreciation costs over the plant's lifetime, ensuring a more comprehensive estimate of the capital costs

[0075] . Further details and relevant data can be found in Table 5, and Tables 7-8. The operating expenses (OpEx) included both feedstock and non- feedstock components. The feedstock component was directly related to the electricity required to run the system, while the non-feedstock component included costs associated with labor, on-site feedstock handling, and maintenance. The LCOCC was then calculated by combining CapEx (with depreciation) and OpEx (including both feedstock and non-feedstock components). Whenever assumptions were necessary for our analysis, we opted for conservative estimates to avoid overly optimistic projections of the LCOCC. As a result, the actual LCOCC values can be lower than those reported here.

[0107] Sensitivity Analysis.

[0108] A sensitivity analysis was performed to examine the impact of key variables on the LCOCC. The analysis evaluated the influence of four factors: energy consumption, GDE cost, cell lifetime, and capture capacity. Energy consumption was analyzed from 1.53 to 2.94 GJ / tonne CO2, ranging from the theoretical minimum for the EMAR process to the highest experimental value observed in our study, which can be the worst-case scenario. GDE cost was evaluated from $5 per m2, achievable based on prices projected by the Department of Energy (DOE)

[0076] , to $30 per m2, reflecting the price range reported in the literature for similar scaled-up processes

[0077] . Cell lifetime was varied from 4 to 12 years, representing the typical range for electrochemical systems [43, 67]. Capture capacity varied from 1 to 5 MtonneCO2 / year, covering facility sizes from average cement plants to large coal power plants

[0079] . Detailed sensitivity analysis assumptions are presented in Table 10.

[0109] Cost Target Analysis.

[0110] A cost target analysis was performed to identify the minimum CO2 removal efficiency and current density required to achieve specific cost targets. This analysis also helped with assessing the impact of CO2separation rate as a key parameter in TEA, which is directly related to the current density and efficiency: ^^^^°= ^^^^×^^^^ ^^^^ (4)Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 where η is the CO2 removal efficiency, I is the average current density, and F is the Faraday constant. The removal efficiency varied from 70% to 100%, and the current density ranged between 100 and 500 A / m2. The analysis also included two different lifetimes for GDEs (8 and 12 years) to provide a comprehensive understanding of how these parameters interact to affect LCOCC in different scenarios. A similar analysis was conducted for GDE costs and the results are provided herein. Contour lines corresponding to LCOCC values of $50, $75, and $100 per tonne of CO2were added to the plot to highlight the operational zones required to reach these target cost levels.

[0111] RESULTS

[0112] CO2Removal Efficiency

[0113] Mesh-attached GDE.

[0114] The CO2 removal efficiency of the two mesh-attached GDEs, one assembled with a 50x50 mesh and the other with a 100x100 mesh, was evaluated across three different carbon- based substrates (Figure 2). The overall removal efficiencies ranged between 35% and 55%, regardless of the carbon-based substrate or mesh size. Among the substrates, GDS 230 exhibited the highest efficiency, reaching up to 55%, followed by Toray 060 and GDL 240. While the 100x100 mesh generally demonstrated slightly higher removal efficiencies compared to the 50x50 mesh, the difference was not significant for most samples. The only notable exception was GDS 230, where the 100x100 mesh showed an approximately 10% increase in efficiency over the 50x50 mesh.

[0115] The results suggest a CO2 removal inefficiency of 45% to 65% from the mesh- attached GDEs. This inefficiency likely originates from two sources: (1) a parasitic oxidation reaction occurring alongside the desired oxidation of copper on the anode electrode (i.e., Cu0→ Cu2++ 2e−), which is the primary driving force for the eventual desorption of CO2, and (2) the desorbed CO2 at the anode interface (the mesh in this case) was not effectively collected in the gas channel behind the GDE. The former can be referred to as Faradaic inefficiency, and the latter as inefficient CO2 collection. Previous studies have demonstrated that the EMAR system achieves nearly 100% Faradaic efficiency, indicating that almost all of the applied current is utilized for the intended copper redox reactions—copper oxidation at the anode and reduction at the cathode— without significant parasitic side reactions [19, 26, 27]. Without wishing to be bound by theory,Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 the primary source of removal inefficiency can be due to inefficient collection rather than inefficient desorption.

[0116] The inefficient CO2collection can be attributed to the presence of a microscale gap, or “microgap”, between the mesh and the carbon-based substrate, which is filled with the electrolyte. As the desorbed CO2 travels through this wetted microgap, it is partially reabsorbed into the electrolyte, either by available free amines or hydroxide ions (Figure 2 panel B). Without wishing to be bound by theory, since CO2absorption by primary amines such as EDA (forming carbamate) is kinetically faster than by hydroxide (forming bicarbonate) [61, 62], reabsorption by amine can be the dominant pathway, given the short distance and brief time during which CO2traverses the electrolyte-filled microgap. Eliminating the microgap is challenging, as it is a consequence of the mechanical attachment of the mesh to the carbon-based substrate. Attempts to create a zero-gap electrode by mechanically pressing the materials at elevated pressures and temperatures were unsuccessful, as the fragility of the carbon paper resulted in its structural failure.

[0117] The relative removal efficiencies of the different carbon-based substrates can be linked to their structural and morphological characteristics. The GDL 240 substrate is coated with a carbon black MPL and a PTFE layer. Toray 060 has only a PTFE layer, while GDS 230 lacks both layers. Cross-sectional SEM images confirmed the presence of these layers. These layers create resistance to CO2 transfer through the material matrix.

[0118] The differences in removal efficiencies between samples with different mesh sizes can be attributed to the variation in their thickness, which affects the travel distance and time for CO2 from desorption at the anode interface to reaching the gas channels. The thickness of the 50x50 mesh (228 μm) is twice that of the 100x100 mesh (128 μm), resulting in CO2being exposed to the electrolyte for almost twice as long after desorption in the 50x50 mesh. This longer exposure increases the likelihood of CO2 reabsorption mainly by amine as described earlier.

[0119] Electrodeposited GDEs. Electrodeposited GDEs were prepared by depositing copper with specific loadings onto the three different carbon-based substrates. In general, the CO2removal efficiency of the electrodeposited GDEs outperformed that of the mesh-attached GDEs, with several samples reaching efficiencies above 90% (Figure 3 panel A). Among the different carbon substrates, GDS 230 and Toray 060 showed similar efficiencies, both of which were significantly higher than that of GDL 240, regardless of the copper loading. These differences canDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 be attributed to the structural and morphological characteristics of the substrates, as observed in the mesh-attached GDEs.

[0120] The efficiency was adversely impacted by higher copper loadings, irrespective of the substrate type. At a copper loading of 0.7 mg / cm2, Toray 060 and GDS 230 achieved efficiencies of 95%, while GDL 240 reached 67%. The efficiencies slightly decreased at a copper loading of 1.2 mg / cm2, with Toray 060 at 91%, GDS 230 at 90%, and GDL 240 at 65%. Further increases in copper loading to 1.7 mg / cm2led to more efficiency reductions: 78% for Toray 060, 76% for GDS 230, and 62% for GDL 240. Beyond 1.7 mg / cm2, a substantial drop in efficiency was observed. At a copper loading of 2.5 mg / cm2, the efficiencies dropped to 48% for Toray 060, 55% for GDS 230, and 42% for GDL 240, nearing the average efficiency of the mesh-attached GDEs (42%). Efficiencies fell below the mesh GDE average when copper loading reached its highest at 3.3 mg / cm2(Figure 3 panel A).

[0121] The microgap present in the mesh-attached GDEs was inherently eliminated in the electrodeposited GDE assembly, as the copper was directly deposited onto the surface of the carbon substrate. However, the deposited copper layer itself can act as a physical barrier to the transport of desorbed CO2from the electrode interface to the gas channel, leading to the reabsorption of desorbed CO2, and consequently, lowering the removal efficiency. In the case of GDL 240, the MPL can also contribute to this barrier effect (Figure 3 panel B), and without wishing to be bound by theory this explains the lower efficiency of GDL 240 compared to Toray 060 and GDS 230, both of which lack an MPL, regardless of the copper loading.

[0122] As copper loading increases, the physical barrier effect intensifies, which without wishing to be bound by theory, can lead to blocking the pores on the carbon paper, as indicated by SEM images (Figure 3 panels C-N). At higher copper loadings (Figure 3 panels F, J, and N), the surface becomes almost completely covered by the copper layer, creating significant resistance to the removal of desorbed CO2, resulting in higher rates of CO2 reabsorption and lower efficiencies. EDS results for all three samples show that the green color representing the porous carbon paper fades away as it becomes covered by the copper layer. In the case of GDL 240, the surface is nearly fully covered with copper even at lower loadings (Figure 3 panel L). This formation of a copper layer as a physical barrier to CO2transport explains the efficiency drop with increasing copper loading. Additional details on the SEM and EDS results can be found herein.

[0123] Current Density and Energy ConsumptionDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0124] In addition to CO2 removal efficiency, two other critical performance metrics were investigated: current density, which reflects the carbon capture rate, and energy consumption, which indicates the energetics of the carbon capture process. As for current density, the mesh- attached GDEs outperformed the electrodeposited GDEs, likely due to the larger amount of copper available per surface area on the electrode. Among the mesh sizes, the 50x50 mesh exhibited better performance compared to the 100x100 mesh, with the highest current density achieved by the 50x50 mesh attached to GDS 230, reaching 184 A / m2(Figure 4 panel A). For the electrodeposited GDEs, increased copper loading led to higher current densities due to the greater amount of redox- active material available for the same surface area. The highest current density for the electrodeposited GDEs was observed with the Toray 060 substrate at a copper loading of 1.7 mg / cm2, reaching 176 A / m2.

[0125] As for energy consumption, electrodeposited GDEs required less energy to remove CO2compared to the mesh-attached GDEs (Figure 4 panel A). Among the mesh-attached GDEs, energy consumption was highest for GDL 240, followed by Toray 060 and GDS 230, which is consistent with the removal efficiencies observed in Figure 2. For the electrodeposited GDEs, energy consumption followed a similar trend, with higher copper loadings requiring more energy. These results highlight the critical impact of removal efficiency on the energy intensity of the carbon capture process.

[0126] Increasing copper loading had a positive impact on current density but negatively affected both CO2removal efficiency and energy consumption. Therefore, there is an optimal copper loading for performance. Considering the high removal efficiency (87%), high current density (176 A / m2), and low energy consumption (76 kJ / mol CO2), Toray 060 with 1.7 mg / cm2of copper loading was identified as the most optimal GDE, exhibiting the best overall performance metrics. The performance of this GDE assembly served as the basis for the TEA discussed in Section 3.3.

[0127] The performance of the developed GDEs, both mesh-attached and electrodeposited, in terms of current density and energy consumption, was compared to the performance metrics reported for a wide range of configurations in conventional membrane-based EMAR systems (Figure 4 panel B). The membraneless EMAR with GDE electrodes proved competitive with conventional EMAR systems. Importantly, the introduction of these new electrodes and the substantial simplification of the process, which without wishing to be bound by theory can reduceDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 costs, did not result in an increase in energy consumption or a reduction in current density. Additionally, the GDE configurations, particularly the electrodeposited GDEs, achieved significantly higher removal efficiencies (>90%) compared to conventional EMAR, which is typically limited to <75%

[0037] . Overall, the developed membraneless EMAR with GDE electrodes demonstrates promising performance metrics, making it a viable option for scalable electrochemical carbon capture.

[0128] Economics of the Membraneless EMAR

[0129] Purchase Cost Contributions.

[0130] TEA was performed to compare the economics of carbon capture using the developed membraneless and the conventional membrane-based EMAR. A breakdown of the purchased equipment cost (PEC) for the membraneless EMAR versus the conventional EMAR is shown in Figures 5 panels A and B, revealing the individual cost components. Due to the significantly simpler process flow diagram of the membraneless EMAR (Figure 15), fewer equipment purchases are required. Specifically, the absorption column and cooling tower, flash tank, and most of the pumps are eliminated. This simplification offers a clear economic advantage for the membraneless system. The electrochemical cell remains the major cost component in both systems, accounting for 78.4% in the membraneless and 80.8% in the conventional system. In the membraneless EMAR, the GDE accounts for 63.1%, while the membrane can be 55.8% of the PEC in the conventional system.

[0131] Levelized Cost of Carbon Capture. Both CapEx and OpEx were considered in evaluating the LCOCC (Figure 5 panel C). In both systems, CapEx is the dominant factor in the levelized cost, with $38.9 / tonneCO2for the membraneless system and $85 / tonneCO2for the conventional EMAR. The primary reason for the reduced CapEx in the membraneless system is the elimination of the expensive ion-selective membrane, which is replaced by the significantly less costly carbon-based GDEs. Additional cost savings are attributed to the elimination of the several process components, as discussed. The major contributor to OpEx is electricity consumption. Due to its more efficient process, the membraneless EMAR has a lower electricity cost ($28.8 / tonneCO2) compared to the conventional EMAR ($47.8 / tonneCO2). When combining both CapEx and OpEx, the levelized cost of CO2capture for the membraneless EMAR drops to $69.7 / tonneCO2, compared to $137 / tonneCO2for the conventional system (Figure 5 panel C). ThisDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 substantial cost reduction makes the membraneless EMAR an attractive, cost-effective solution for carbon capture from point sources.

[0132] Sensitivity Analysis.

[0133] A sensitivity analysis was performed to evaluate the impacts of four key factors— energy consumption, GDE cost, cell lifetime, and capture capacity—on the levelized cost (Figure 5 panel D). This analysis helps identify the most critical factors for optimizing the system’s cost- effectiveness. Energy consumption had the most significant impact; increasing the energy consumption from 1.53 GJ / tonneCO2 (the minimum theoretical required energy) to 2.94 GJ / tonneCO2(the highest energy requirement observed in Figure 4 panel A) led to a rise in the levelized cost from $62 to $111 per tonne CO2. The variation in GDE cost was also prominent, where a GDE cost of $5 / m2resulted in a levelized cost of $52 / tonneCO2, compared to $96 / tonneCO2 when the GDE price was $30 / m2. An increase in cell lifetime from 4 to 12 years reduced the levelized cost from $102 to $59 per tonne of CO2. A decrease in capture capacity from 5 MtonneCO2 / year (an average annual emission of coal-fired power plant) to 1 MtonneCO2 / year (a typical annual emission of cement plant) did not show a significant increase in the levelized cost, reflecting the viability of the process in lower scales, inherited from its modularity.

[0134] Cost Target Analysis.

[0135] A cost target analysis was conducted to determine the minimum CO2 removal efficiency and current density required to meet specific levelized cost targets. The removal efficiency varied between 70% and 100%, ranges that can be effectively achieved with the developed electrodeposited GDEs (Figure 3 panel A), while the current density ranged from 100 to 500 A / m2. Additionally, two different lifetimes, 8 and 12 years, were considered. The 8-year cell lifetime, representing the baseline for LCOCC calculations in both conventional and membraneless EMAR systems, was selected based on the typical lifespan of conventional EMAR systems

[0043] . A 12-year cell lifetime, representing the upper bound in the sensitivity analysis, reflects the potential durability of the membraneless EMAR. Given the simplified process flow and the absence of an ion-selective membrane—known to present long-term operational challenges [63, 64]—achieving this extended lifetime is realistic for the membraneless configuration. A similar analysis was performed for GDE costs, with the detailed results provided herein. The results show that achieving a levelized cost below $50 is feasible, with an operational zone bounded by efficiencies above 85% and current densities exceeding 300 A / m2. With anDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 improvement in the cell lifetime from 8 years to 12 years, achieving a levelized cost below $50 is even more feasible, with an operational zone bounded by efficiencies above 76% and current densities exceeding 200 A / m2. The minimum required current density and efficiency for achieving levelized costs below $50 further decrease with lower GDE costs. Achieving capture costs below $50 / tonneCO2 positions the membraneless EMAR system as a leading electrochemical solution for point-source carbon capture, making it a highly cost-effective technology.

[0136] Identifying these cost target zones is a valuable resource for guiding future research and development. Both efficiency and current density are parameters that can be systematically studied, from fundamental to practical aspects, using established scientific approaches. The plot provides a clear understanding of the extent of development needed to reach the desired cost targets. Given the high removal efficiencies already achieved with the electrodeposited GDEs (>90%), future efforts can focus on increasing the current density. For example, improving the kinetics of redox reactions at the electrode, and thereby increasing the current density, can be achieved through the use of advanced catalysts, optimizing the electrode surface area, or enhancing mass transfer rates at the gas-liquid interface [59, 65-67]. Overall, the cost target analysis provides a crucial framework for setting research priorities, helping to identify the necessary improvements in efficiency and current density to achieve more economically viable carbon capture with the membraneless EMAR system.

[0137] DISCUSSION

[0138] This study successfully developed a novel membraneless EMAR system for carbon capture, utilizing GDEs to eliminate the need for ion-selective membranes. The research was motivated by the significant contribution of membranes to the capital expenditure of conventional EMAR. Two types of GDE assemblies were investigated: mesh-attached and electrodeposited. Electrodeposited GDEs demonstrated superior performance over mesh-attached GDEs, achieving CO2 removal efficiencies exceeding 90% compared to 35-55% for mesh-attached GDEs. Without wishing to be bound by theory, this improvement can be attributed to the elimination of the microgap present in mesh-attached GDEs. This microgap caused inefficiency by allowing the reabsorption of desorbed CO2 back into the electrolyte, a problem that was effectively resolved in the electrodeposited GDEs. However, for electrodeposited GDEs, the determining factor was the copper loading; higher copper loadings resulted in lower carbon removal efficiency due to the copper deposition layer acting as a physical barrier against CO2 transport through the GDE. TheDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 relationship between copper loading and this barrier effect was confirmed by SEM and EDS analyses. Among the carbon-based substrates tested for electrodeposited GDEs, Toray 060 with an optimal copper loading of 1.7 mg / cm2exhibited the best overall performance, achieving 87% removal efficiency, 176 A / m2 current density, and 76 kJ / molCO2 energy consumption.

[0139] TEA confirmed the economic advantages of the membraneless EMAR system, with the LCOCC dropping ~50% to $69.7 / tonneCO2, compared to $137 / tonneCO2 for the conventional system. In some embodiments, this cost reduction can be attributed to lower CapEx, for example the elimination of expensive membranes and other process components i.e., absorption column, pumps, and flash tank. Sensitivity analysis and cost target analysis indicated the feasibility of achieving carbon capture costs as low as $50 / tonneCO2with the membraneless EMAR system if the performance metrics (current density and removal efficiency) are further improved.

[0140] Therefore, without wishing to be bound by theory, we can increase current density while maintaining high carbon removal efficiency and low energy consumption. To enhance the current density of the membraneless EMAR system, several strategies can be explored. Electrode engineering techniques, such as surface modifications through acid, plasma, or thermal treatments, can improve electrode activity and stability. Optimizing the structure of the GDE, including refining the layer configuration and adjusting porosity, can significantly enhance mass transfer efficiency. Further improvements can be achieved by optimizing the cell geometry to promote uniform current distribution and minimize energy losses. Additionally, electrolyte optimization, whether by modifying the background electrolyte composition or introducing specific additives, can play a role in increasing the current densities. However, these strategies to improve current density can involve trade-offs with other performance metrics, such as absorption kinetics, energy consumption, and Faradaic efficiency. Therefore, a systematic investigation focused on enhancing current densities while maintaining other key performance metrics is necessary.

[0141] Long-term cycling studies are also necessary to evaluate the performance stability of carbon substrates, particularly under continuous operation and varying conditions, such as fluctuating CO2 concentrations and electrolyte degradation. Investigating the durability of electrodeposited GDEs at higher copper loadings and their susceptibility to physical and chemical degradation over extended cycles is critical to ensure sustained performance. Furthermore, evaluating the resistance of the GDE to fouling, scaling, and operational stresses (e.g., mechanical stability under pressure) will provide insights into their long-term viability for industrialDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 applications. Additionally, comprehensive optimization of electrodeposited GDEs, including pore size, porosity, and surface area, is crucial to fully understanding CO2 desorption dynamics at the electrode-electrolyte interface.

[0142] While the study incorporated oxygen (7% O2) into the simulated flue gas to replicate real flue gas conditions, experimental results indicated that oxygen did not negatively impact the system’s performance, indicating oxygen tolerance. Moreover, sulfur oxides (SOx), such as sulfur dioxide (SO2), pose potential challenges [68, 69]. SOx species are known to cause catalyst degradation and passivation, which can lead to electrode performance decay in the EMAR process. Moreover, trace amounts of dissolved SOx-derived species, like hydrogen sulfide ions (HS−), can react with copper ions in the electrolyte, leading to unwanted copper sulfide precipitation that can impair system operation

[0070] . If required, without wishing to be bound by theory, established desulfurization techniques—such as flue gas desulfurization scrubbing, commonly implemented in power plants—can be integrated into the process with minimal disruption to the overall system design. Addressing these considerations can provide the long-term stability and operational robustness of the membraneless EMAR system, ultimately enhancing its readiness for future large-scale implementations.

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[0223] List of Reactions Involved in the EMAR Cycle

[0224] The EMAR cycle comprises a series of interconnected redox and non-redox reactions that enable efficient CO2 capture and amine regeneration. Table 1 presents the complete set of reactions involved in the EMAR cycle. The integration of these reactions creates a closed- loop system for CO2 capture and amine regeneration [1]. The lean amine solution (e.g., ethylenediamine, EDA) initially absorbs CO2 at the interface of the cathode gas diffusion electrode (GDE) (Eqn.1). As it becomes saturated EDA-CO2(aq), it migrates to the anode, where the copper oxidation provides Cu2+(aq) ions (Eqn.2). These cupric ions facilitate the release of CO2 from the amine through copper complexation with EDA (Eqn.3). The copper-EDA complex is reduced at the cathode, resulting in depositing copper and regenerating the amine solvent (Eqn.4).

[0225] To maintain system stability and prevent copper accumulation at the cathode or depletion at the anode GDEs, the roles of the electrodes were periodically switched during operation. This was accomplished by reversing the polarity, allowing the anode to function as the cathode and vice versa—while simultaneously redirecting the flue gas (i.e., stream gas) and sweep gas to the appropriate electrodes using 3-way valves for each gas channel. This strategy ensures balanced copper distribution across the electrodes, supporting continuous and stable system performance. A similar strategy was used in the previous studies with the conventional EMAR process scheme [2-4]. Table 1. Reactions Involved in the EMAR Cycle Type Location Reaction Nature CO2At theof the EDA(aq)Non- n GDE* (1) RedoxDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 02+ –CopperAnode GDECu(s)→ Cu(aq)+ 2e Corrosion (2)RedoxCopper At the Interface2+ 2+Non- Cu + 2EDA-CO → Cu(EDA) + 2CO(aq) 2 (aq) 2 (aq) 2 Complexio of the Anode Redox (3)(g)n GDE 2+ – 0Copper Cu(EDA) + 2e → Cu + 2EDA2 (aq) (s) (aq)Cathode GDE RedoxDeposition (4)* GDE: Gas Diffusion Electrode

[0226] Optimization of Electrolyte Composition and Applied Potential

[0227] Electrolyte Composition

[0228] Background Electrolyte. Two different background electrolytes, potassium sulfate (K SO ) and sodium sulfate (Na SO ), were tested at concentrations of 0.25 M and 0.5 M, each2 4 2 4combined with a fixed 0.25 M CuSO , to determine the optimal background electrolyte and4 concentration. Both sodium and potassium salts are commonly used in electrochemical systems due to their high mobility, solubility, non-reactivity, and low cost, as well as being non-toxic and abundant [5, 6]. Sulfate anions were chosen as they do not undergo parasitic chemical or electrochemical reactions in the EMAR process, unlike nitrate or chloride [7, 8], and offer high mobility, solubility, and abundance. These electrolytes were tested in the membraneless EMAR developed in this study, which was polarized at 1 V to evaluate their performance. The background electrolytes were compared in terms of carbon dioxide (CO ) removal efficiency (%), current2 2 density (A / m ), and energy consumption for desorption (kJ / molCO ). Although the differences2were not significant, 0.5 M Na SO was the most effective background electrolyte overall (Figure2 46 panel A).

[0229] Copper Concentration.

[0230] In the conventional EMAR, which operates with a two-compartment cell separated by a membrane, the copper concentration varies depending on the location along the electrode. However, in the membraneless EMAR, which uses a one-compartment cell, the concentration of copper theoretically remains constant throughout the process, as the same rate of copper oxidation and reduction results in no net change in copper concentration. For the conventional EMAR, the optimal copper concentration range has been identified as 0.1 M for the stream entering the anode compartment, 0.25 M at the midpoint, and 0.4 M at the exit of the anode compartment [7, 9]. Therefore, we aimed to find the most optimal copper concentration for the membraneless EMAR, focusing on the same concentration range.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0231] Similar to the optimization of the background electrolyte, the performance metrics of CO2 removal efficiency, current density, and energy consumption were used for comparison. The results indicated that 0.25 M Cu2+yielded the highest removal efficiency of 55%. The lowest efficiency, <10%, was observed at 0.4 M Cu2+. The highest current density was also observed at 0.25 M Cu2+. While increasing the copper concentration improves the deposition rate, it simultaneously decreases the corrosion rate, resulting in 0.25 M Cu2+being the best trade-off between these effects. Energy consumption was also the lowest for 0.25 M Cu2+and the highest for 0.4 M Cu2+(Figure 6 panel B). Operating at 0.4 M Cu2+offers a limited carbon capture capacity, as the majority of Cu2+is already complexed with EDA, which without wishing to be bound by theory, explains the low removal efficiency and high energy consumption at this concentration. Overall, 0.25 M Cu2+was identified as the most optimal concentration for the membraneless EMAR, considering all three performance metrics. It is important to note that these experiments were not performed using the most optimal GDE configuration, which explains the generally low efficiencies observed across all experiments.

[0232] Applied Potential

[0233] The applied potential was optimized by varying it at 0.25, 0.5, 0.75, 1.0, and 1.25 V. Similar to the electrolyte composition investigation, three performance metrics—CO2removal efficiency, current density, and energy consumption—were monitored for each applied potential. The current density increased with the applied potential, as expected from the Butler-Volmer equation

[0010] . The lowest energy consumption of 63 kJ / molCO2was achieved at 0.75 V, in contrast to the highest energy consumption of 362 kJ / molCO2 recorded at 0.25 V. Energy consumption slightly increased to 80 kJ / molCO2at 1 V. Considering the significantly higher current density at 1 V (176.6 A / m2) compared to 0.75 V (77 A / m2) and the minor differences in energy consumption, operating at 1 V was determined to be the most optimal potential. At the cost of slightly higher energy consumption, a current density more than double that of 0.75 V was achieved at 1 V, effectively reducing the required electrode area by more than half. CO2desorption efficiency remained high when increasing the potential from 0.75 V to 1 V (Figure 7). Further increasing the potential beyond 1 V, while beneficial for current density, increased the risk of GDE degradation and parasitic redox reactions, particularly water splitting.

[0234] Carbon-Based Substrates for GDEsDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0235] Three carbon-based substrates were used as gas diffusion media for the GDEs to facilitate the removal of desorbed CO2: Toray 060, GDS 230, and GDL 240. All substrates consisted of carbon fiber paper, but only GDL 240 was coated with a carbon black microporous layer (MPL). Additionally, both Toray 060 and GDL 240 were wet-proofed with a 5% polytetrafluoroethylene (PTFE) layer. The presence of PTFE in Toray and GDL 240 was confirmed by the detection of fluorine (F) in their atomic composition from EDS analysis, as shown in Table 2. Toray 060 exhibited the highest tensile strength (50 N / cm) and flexural modulus (10 GPa) compared to the other substrates, which without wishing to be bound by theory, can lead to better mechanical stability and durability under operating conditions. This can be beneficial in maintaining structural integrity during prolonged use. A summary of the key characteristics of each substrate is provided in Table 2, and photos of these substrates are shown in Figure 8. Table 2. Key characteristics of the carbon-based substrates used for GDEs Elemental*reported for cross direction (the first value) and machine direction (the second value)

[0236] Electrodeposited GDEs

[0237] Chronopotentiometry was used to prepare the electrodeposited GDEs from carbon- based substrates at a constant current of 50 mA for varying durations. Deposition times of 15, 22.5, 30, 45, and 60 minutes resulted in copper loadings of 0.7, 1.2, 1.7, 2.5, and 3.3 mg / cm2, respectively. The voltage profiles corresponding to these fixed current applications for each carbon substrate were recorded (Figure 9). The voltage consistently remained within the range of 0.8 to 0.9 V, regardless of the carbon substrate or deposition time. The coulombic efficiency of the deposition (i.e., the ratio of actual deposition to the theoretical deposition based on transferredDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 charge) was about 100% for all samples. These observations confirm the reproducibility and efficiency of the electrodeposition process. SEM images in Figure 9 show the uniform growth of the deposited copper layer on the surface of the substrates, without significant local agglomerations.

[0238] Cross-Sectional SEM and EDS Analyses

[0239] Cross-sectional analyses were performed to evaluate the layer compositions and structure of the substrates. These analyses also provided insights into the copper deposition process. Figure 10 shows non-limiting, exemplary cross-sectional SEM images of the three substrates and their corresponding EDS results. The SEM images highlight the porous structure of the substrates, which is essential for gas diffusion. In the case of GDL 240, the presence of the MPL layer is clearly visible on top of the porous media. In all three samples, carbon (C) was the dominant element detected. For both Toray 060 and GDL 240, the presence of fluorine (F) was confirmed due to the PTFE treatment. Traces of oxygen (O) were also observed.

[0240] The copper deposition process was also investigated using combined cross- sectional SEM and EDS analyses. The results show that deposition begins at the surface and gradually builds up on the top layer (Figure 11). This deposited layer can act as a physical barrier against the transport of desorbed CO₂, leading to a drop in removal efficiency. This impact becomes more pronounced as copper loading increases, which without wishing to be bound by theory, explains the lower efficiencies observed at higher copper loadings.

[0241] The Developed Electrochemical Cell Configuration

[0242] A membraneless one-chamber electrochemical cell was designed and manufactured in the lab. The cell consisted of a main cylindrical chamber that holds 4 mL of electrolyte, with two side end plates featuring central circular notches (20 mm in diameter) for CO2absorption and desorption. The end plates also include small inlet and outlet ports on the sides to introduce either the simulated flue gas on the cathodic side, consisting of 15% CO2, 7% O2, and 78% N2, corresponding to a CO2partial pressure of 0.15 atm, or sweep water vapor on the anodic side to facilitate the removal of CO2 bubbles from the electrode surface. Figure 12 shows a non-limiting, exemplary schematic representation of the cell with all the components.

[0243] Current Profiles of Desorption Experiment for the Electrodeposited GDEs

[0244] Described herein are representative current profiles recorded during the 15-minute desorption experiments for electrodeposited GDEs prepared on three different carbon-basedDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 substrates: Toray 060, GDS 230, and GDL 240. The experiments were conducted at room temperature (22°C) under a constant applied potential of 1 V. Current responses were recorded using EC-Lab (Biologic), and the experiments were performed for two different copper loadings, 1.7 mg / cm2and 2.5 mg / cm2, on each GDE substrate. The resulting current-time (I–t) profiles are presented in Figure 13. The recorded current profiles exhibit stable behavior throughout the 15- minute desorption period across all tested configurations. For each substrate and copper loading, the current rapidly reached a steady-state value within the initial moments of the experiment and maintained this level for the remainder of the run. This indicates a stable electrochemical environment and consistent CO2desorption performance during the applied potential.

[0245] Electrochemical CO2Desorption: Quantity and Quality Measurements

[0246] The quantity and quality of desorbed CO2 were monitored by evaluating the liquid phase (i.e., electrolyte) using the acid titration method and the gas phase using gas chromatography (GC).

[0247] Titration.

[0248] For the acid titration method, the procedure involved transferring 1 mL of the electrolyte solution into a vial, followed by the addition of 1 mL of 4 M HCl using an injection syringe. The 4 M HCl concentration was chosen based on its effectiveness in removing all CO2from the electrolyte, as supported by previous studies [2, 7]. The increased proton concentration from the acid addition facilitates CO2desorption by protonating EDA and also shifting the bicarbonate equilibrium towards gaseous CO2. The released gas was then directed into a U-shaped (or U-Tube) manometer, where the volume of released gas was measured by observing the liquid level changes in both arms of the manometer. This volume was then converted to moles to calculate the CO2loading of the electrolyte. A non-limiting, exemplary photo of the apparatus is shown in Figure 14 panel A.

[0249] Gas Chromatography (GC).

[0250] To qualitatively assess the composition of the desorbed gas from the membraneless EMAR cell, GC (990 micro GC, Agilent) was employed. The GC system comprised two channels: Channel A was designated for detecting O2 and N2, using argon as the carrier gas, while Channel B was utilized for identifying CO2and other organic gases, such as CH4and C2H2, with helium as the carrier gas. Desorbed gas samples were collected via the upward gas delivery method into a small vial from the electrochemical cell and subsequently transferred to a 10 mL syringe.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 Additionally, the headspace gas prior to the CO2 desorption experiment was collected in a 10 mL syringe to accurately monitor the composition of the gas before and after desorption. Both samples were injected into the GC for detailed analysis.

[0251] The detector responses were displayed as peaks corresponding to retention times, as shown in Figure 14 panel B. In Channel A, two distinct peaks were identified at retention times of 45 seconds and 55 seconds, corresponding to O2and N2, respectively. The relative intensities of these peaks indicated that the concentrations of O2and N2in the headspace gas were higher than in the desorbed gas, as the presence of CO2 in the desorbed gas reduced the partial pressures of O2 and N2. Channel B exhibited two major peaks: (1) a cumulative response from Channel A at 17 seconds, and (2) a peak for CO2at 20 seconds. These results confirm that the headspace gas predominantly contained O2 and N2, with minimal CO2 (due to the CO2 in the air), in contrast to the desorbed gas, which had a significantly higher concentration of CO2. Overall, the results verify that the desorbed gas was only composed of CO2, confirming the effectiveness of the CO2desorption process within the electrochemical cell.

[0252] S9. Evaluation of the Electrolyte Stability

[0253] To ensure the long-term viability of the membraneless EMAR system, the stability of the electrolyte—particularly the EDA amine—was thoroughly evaluated. Both the gas and liquid phases were analyzed to detect any potential degradation products that can impact system performance. The gas phase was analyzed using GC to identify any volatile byproducts in the desorbed gas stream, while the liquid phase was examined using Fourier Transform Infrared (FTIR) spectroscopy to monitor changes in functional groups. Together, these analyses provide a complimentary assessment of the electrolyte’s chemical stability under the experimental conditions.

[0254] GC Measurements.

[0255] During the experiment, the gas phase generated at the anode was collected using helium as the sweep gas and introduced into the GC instrument for analysis. Helium was selected as the sweep gas because it does not interfere with CO2 detection on the same column, allowing for a clear observation of CO2 evolution throughout the experiment. The GC results from both channels confirmed the evolution of CO2on Channel B as the only gas collected from the anode GDE (Figure 15 panel A). Aside from the desorbed CO2and helium (the sweep gas observed on Channel A), no other gases were detected in either channel, validating that no electrolyteDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 degradation or unwanted side reactions occurred during the electrochemical process. A detailed description of the GC procedure, along with information on Channels A and B, is provided herein.

[0256] Fourier Transform Infrared (FTIR) Spectroscopy.

[0257] FTIR spectroscopy was conducted to evaluate any molecular or structural changes in the electrolyte before and after the desorption experiments. The measurements were performed using a Thermo Scientific Nicolet iS5 spectrometer with an Attenuated Total Reflection (ATR) setup employing a diamond crystal. Spectra were recorded in absorbance mode over a wavenumber range of 450–4000 cm–1at ambient room temperature. As shown in Figure 15 panel B, no significant differences were observed between the spectra before and after the experiment, indicating that the electrolyte remained chemically stable throughout. Key peaks include a broad band at 3233 cm–1corresponding to O-H stretching due to the aqueous nature of the electrolyte, a peak at 1636 cm–1attributed to H-N-H scissoring vibrations, and peaks in the range of 1486–1332 cm–1associated with carbonates and bicarbonates formed during CO2saturation. Additionally, a peak at 1100 cm–1corresponds to C-O stretching [11, 12]. These identical peaks for both before and after desorption confirm that no degradation or side product formation in the liquid phase occurred during the experiments.

[0258] Minimum Work Requirements

[0259] It is essential to evaluate the thermodynamic minimum separation work based on the free energy of mixing. This indicates the theoretical lower limit of energy required to separate CO2from a gas mixture regardless of the specific separation mechanism employed. For a system splits the feed stream (15% CO2) into two outlet streams: a CO2-lean stream containing approximately 1.5% CO2(after 90% capture) and a CO2-rich stream containing the captured CO2(100% CO2), the thermodynamic minimum separation work can be calculated as

[0013] : ^^^^^^^^ ∑ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (^^^^ ln^^^^ + ^^^^ ln^^^^ − ∑ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ =^^^^^^^^2 ^^^^^^^^2 ^^^^^^^^^^^^ ^^^^^^^^2 ^^^^^^^^^^^^ ^^^^^^^^2) (^^^^^^^^^^^^2 ln ^^^^^^^^^^^^2+ ^^^^^^^^^^^^^^^^ ^^^^^^^^2 ln^^^^^^^^^^^^^^^^ ^^^^^^^^2)^^^^^^^^^^^^(5)fractions of the components in each stream, and ∆mCO2 is the moles of CO2 captured from the flue gas. The “non-CO2” gasses included those present in the flue gas (78% N2and 7% O2). The theoretical minimum separation work was calculated as 6.37 kJ / mol CO2. This value indicates the minimum thermodynamic work required for capturing 90% CO2from a 15% CO2feed stream andDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 removing it as a 100% CO2 stream with no other gases, which is slightly lower than the reported absolute thermodynamic minimum of 7.6 kJ / mol CO2 that assumes 100% removal efficiency [4].

[0260] In addition to calculating the thermodynamic minimum separation work, we also determined the second law efficiency (^^^^2^^^^^^^^) to provide a standardized basis for evaluating our system against other CO2separation technologies and to highlight opportunities for further optimization

[0013] . ^^^^^^^^^^^^^^^^^^^^2^^^^^^^^=^^^^^^^^^^^^^^^^^^^^^^^^^^^^ × 100 % (6)our actual energy consumption (Wactual = 60 kJ / mol CO2) to theminimum separation work (6.37 kJ / mol CO2) yields a second-law efficiency of approximately 10.6%.

[0262] In addition to the thermodynamic minimum separation work, the electrochemical minimum work based on the Nerstian potential for the conventional EMAR has been conducted by considering a thermodynamic cycle of a 4-stage system where flue gas with an initial CO2 partial pressure of 0.13 bar (15% CO2) is absorbed into an amine solution and subsequently released at 0.88 bar (100% CO2) [4, 7]. This process involved electrochemically modulating copper loadings between 0.2 and 0.8 (mol Cu / mol amine), with the Nernst equation governing the copper redox reactions during CO2 desorption:^^^^ = ^^^^ +^^^^^^^^ 0 ln([^^^^^^2+^^^^^^^^ ^^ ]) (7)the gas constant (8.314 J K−1mol−1), T is the temperature (K), and n is the number of electrons transferred during the redox reaction (here n = 2). The minimum electrochemical work (^^^^^^^^^^^^^^^^,^^^^^^^^^^^^^^^^^^^^^^^^^^^^) required was calculated by integrating the oxidative (Eox, V) and reductive (Ered, V) potentials over the copper loading cycle: ^^^^ 1 ^^^^^^^^^^^^,^^^^^^^^^^^^^^^^^^^^^^^^^^^^=^^^^°^^^^^^^^ �∫Cu ^^^^^^^^^^^^ ^^^^^^^^ − ∫Cu ^^^^^^^^^^^^^^^^ ^^^^^^^^� (8)was then 15.6 kJ / mol CO2, approximately double the thermodynamic minimum (6.37 kJ / mol CO2) [4, 7, 14, 15].

[0265] In the developed membraneless EMAR configuration, GDEs enabled cathodic absorption with simultaneous amine regeneration and anodic desorption with simultaneous CO2removal, enabling a 2-stage process. As a result of the CO2 removal from the anode, theDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 equilibrium Nernstian potential for the cathodic reaction becomes more positive, while it becomes more negative for the anode, eventually bringing the minimum electrochemical work for this 2- stage system closer to the minimum thermodynamic limit [7, 9, 14, 16]. Therefore, the minimum electrochemical work for the membraneless system falls between 15.6 kJ / mol CO2 and the thermodynamic minimum of 6.37 kJ / mol CO2.

[0266] It is important to note that the calculations presented above represent only the idealized minimum electrochemical work for CO2separation and do not account for additional energy penalties such as overpotentials from ohmic resistance, kinetic limitations, and mass transport losses. Moreover, our thermodynamic analysis excludes the significant energy requirement for separating water vapor from CO2in the product stream. At the anode, water vapor functions as a sweep gas for CO2 removal, resulting in a mixture with an estimated water:CO2 ratio of 3:1 to 5:1. In some embodiments, considering the additional energy required to separate CO2 from water vapor through condensation, the actual energy demand can exceed the estimated 60 kJ / molCO2. This condensation energy is not incorporated into our initial energy assessment or TEA, as our design used the easily available single-pass water vapor stream. An effective approach to eliminate this energy penalty is to modify the gas channel configuration using a closed-loop design, in which the desorbed CO2itself serves as the sweep gas. This configuration removes the need for downstream separation of CO2 from water vapor and is the focus of our ongoing work.

[0267] Mesh-attached GDEs Fabricated at Higher Pressure and Temperatures

[0268] To eliminate the microgap between the mesh and the carbon-based substrate, fabrication of the mesh-attached GDEs was done under elevated pressures and temperatures. The goal was to create a zero-gap electrode by mechanically pressing the materials, thus improving the CO2 removal efficiency by enhancing the contact between the mesh and the substrate. However, these attempts were unsuccessful due to the fragility of the carbon paper, which led to structural failure under these conditions. Figure 16 shows the structural damage observed in the carbon- based substrates after applying elevated pressures and temperatures.

[0269] Techno-Economic Analysis

[0270] Process Design

[0271] Figure 17 shows the process flow diagrams for CO2separation and concentration from flue gas (i.e., stream gas) using conventional and membraneless EMAR systems. In the conventional setup, flue gas CO2 is absorbed by an EDA solution in an absorption column andDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 then desorbed in an electrochemical cell's anode compartment. The resulting mixture undergoes gas-liquid separation in a flash tank, with the lean liquid recycled through the cathode and back to the absorption column. The condensers minimize volatile losses from gaseous streams, while makeup flows compensate for evaporation. The dry flue gas is directed to the vent and a compressor is used to compress CO2 to 150 bar, preparing it for subsequent use or storage.

[0272] The membraneless EMAR design operates as a batch system, integrating both CO2absorption and desorption within a single electrochemical unit. Flue gas CO2is absorbed at the GDE cathode using EDA and subsequently desorbed at the GDE anode, simultaneously with copper oxidation. Water vapor was used as a sweep gas to remove desorbed CO2from the anode side of the cell. The gas stream then undergoes condensation, and the resulting dry CO2is compressed to 150 bar. This streamlined design eliminates the need for a separate absorption column, several pumps, and a flash tank, reducing equipment requirements compared to the conventional system.

[0273] Levelized Cost of Carbon Capture (LCOCC)

[0274] Table 3 provides the baseline performance metrics used for LCOCC calculations for both the conventional and membraneless EMAR systems. The data for the conventional EMAR reflects average values reported across a wide range of previously developed EMAR systems [2, 3, 7, 17-32]. For the membraneless EMAR, performance data were based on the GDE configuration with the highest performance, specifically the Toray 060 substrate with a copper loading of 1.7 mg / cm2, which demonstrated the best combination of removal efficiency, current density, and energetics.

[0275] Table 3. Baseline performance metrics for LCOCC calculations ValueCurrent density176 176 A / m21 0.7 V Voltage

[0276] Table 4 outlines the general assumptions used as a baseline for calculating LCOCC for both systems. These assumptions align with those typically used in the TEA of similar electrochemical systems, such as flow batteries [34-37].Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 Table 4. General assumptions for LCOCC calculation Economic Parameter Value Unit Annual carbon emissions 3.1 Mtonne / year Plant lifetime25Interest rate 10 % EMAR unit lifetime 8 years Capacity factor 90 % Capital recovery factor 11 % Electricity price 64.4 $ / MWh AEM price 50 $ / m2GDE Price 15 $ / m2

[0277] LCOCC for the conventional and membraneless EMAR processes includes capital expenditures (CapEx) with depreciation over the duration of the plant lifetime and operating expenses (OpEx). The CapEx was calculated by considering the annual depreciation cost and was estimated by multiplying the capital recovery factor (CRF) by fixed capital investment (FCI) (Eqn. 7). CRF was derived from the interest rate (i) and plant lifetime (n) using Eqn. 8, and FCI was estimated using Eqns. 9 and 10 based on the Percentage of Delivered-Equipment Cost method

[0038] .^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ℎ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = ^^^^^^^^^^^^ × ^^^^^^^^^^^^ (9)^^^^ (10)(11)^^^^^^^^^^^^^^^^ = ^^^^^^^^ ∑(1 + ^^^1^ + ^^^2^ + ⋯+ ^^^^^^^^) (112)where the factors f1, f2, f3, …, fn are multiplying factors for various cost components such as piping, electricalcosts and are listed in Table 5, adapted from ref.

[0038] . Ci represents the purchased cost of equipment i: ^^^^^^^^ = ^^^^^^^^^^^^ × ^^^^^^^^^^^^^^^^^^^^2023^^^^is the equipment size. The Chemical Engineering Plant Cost Index (CEPCI) was used to update the size- adjusted equipment costs to 2023 values using a scaling factor (k) of 0.6

[0039] .Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0278] Table 5. Ratio factors for estimating capital investment items based on Delivered- Equipment Cost. The ratios used are suitable for a solid-fluid processing plant and are adapted from ref.

[0037] . Fraction of delivered 0.390.26Piping (installed) 0.31 Electrical systems (installed) 0.10 Buildings (including services) 0.29 Yard improvements 0.12 Service facilities (installed) 0.55 Total Direct Costs 2.02 Indirect Costs Engineering and ConstructionLegal expenses 0.04 Contractor's fee 0.19 Contingency 0.37 Total Indirect Costs 1.26

[0279] Based on the process design, the equipment components were divided into two groups: the electrochemical unit’s components and process components (e.g., absorption column). The costs for the electrochemical unit’s components were estimated by scaling up the process using EMAR electrochemical modules, and the final Ciare shown in Table 6. The sizing calculations of the EMAR modules were based on the CO2 desorption rate and material requirements. The total required surface area (ATotal) was determined using: ^^^^^= ^^^^ ^^^^^^^^^^^^^^^^^^^^^^^×^^^^ (14)area ratio (-). I is the total current that needs to be exchanged (A), and is calculated from Eqn. (15): °^^^^ = ^^^^^^^^^^^^×^^^^^^^^^^^^2^^^^ (15)F is Faraday constant (96,485 C / mol), I is current density (unit), and ηFEis faradaic efficiency (%).Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0282] The total number of cells was then calculated by dividing the total required surface area by the individual cell’s area, which is assumed to be 2.56 m2as the typical EMAR stack, adopted from the literature

[0034] . The cells were grouped into stacks of 500 cells each, based on literature suggestion

[0034] . The stacks were further organized into 6 modules in series, following the established segmented electrode configuration in EMAR system design

[0034] . A summary of the sizing parameters is provided in Table 7.

[0283] Table 6. The purchased costs for electrochemical components for both conventional and membraneless EMAR Purchased Equipment Cost, Ci(M$) Conventional 45.3 –– 132Support 31.1 29 Gasket 1.6 1.5 Endplate 14 1.3 Electrode 22.3 – Membrane 255.2 –

[0284] Table 7. Electrochemical desorption unit parameters Value Parameter Unit Conventional Membraneless Cell areaa2.56 2.56 m2Total1,633,007.9 1,407,765.4 m2Electrode active surface area ratioc90 90 % Total number of cellsd637,893 549,908 - Total number of cells per stacke500 500 - Total number of stacksf1276 1100 - Total number of modulesg6 6 - Total number of stacks per moduleh213 183 - a Cell area is related to a typical EMAR stack, adopted from the literature

[0034] ^^^^Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0285] The Ci for process components were estimated based on sizing and data reported for an EDA-based carbon capture unit

[0034] , which employed the same 550 MWe coal-fired powerplant as the National Energy Technology Laboratory (NETL) reference, with a CO2capture unit capacity of 3.1 MtonneCO2 per year. The process parameters, such as absorbent compound and concentration, and CO2 compression pressure were consistent with this reference. Therefore, we opted to use the same process design and equipment sizing in our study, as shown in Table 8. However, all cost values needed to be updated using the Chemical Engineering Plant Cost Index (CEPCI). The calculated Ci for the process components for both conventional and membraneless EMAR processes are listed in Table 9.

[0286] Table 8. Process equipment sizing parameters for the process components for both conventional and membraneless EMAR systems EquipmentConventionMembranele al ssParameter UnitInlet gas2.45 Flow rate / hDirect contact cooler water705 3pump0 – Flow rate m / h Absorption Column 9.8 × 2.25 –Diameter ×Length m × mRich amine pump 274 – kWe Catholyte pump 285 –kWe Lean amine pump 256 – Power kWe Compressor 9650 9650 Pressure kPa Flash tank 15 –Residence5Time minCooling tower 1.01 × 10 – Flow rate m3 / h Cell utility pump 52.6 – Power kWe Absorption column utility pump1.00 – Power MWeCondenser 1 13.5 13.5 Duty MWe Condenser 2 13.5 13.5 Duty MWe Reboiler 2.46 × 1052.46 × 105 Steam Flow 3rate m / h

[0287] Table 9. The purchased costs for the process components for both conventional and membraneless EMAR systems Purchased Equipment Cost, CiDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 Inlet gas blower 6.22 6.22 Direct contact cooler water pump0.65 –Absorption Column 12.04 – Rich amine pump 2.54 – Catholyte pump 2.6 – Lean amine pump 2.44 – Compressor 34.53 34.53 Flash tank 0.6 – Cooling tower 14.45 – Cell utility pump 0.94 – Absorbption column utility pump5.54 –Condenser 1 0.73Condenser 2 0.73 Reboiler 3.71 3.71

[0288] The OpEx included both feedstock and non-feedstock components. The feedstock component was directly related to the electricity required to run the system, while the non- feedstock component included costs associated with labor, on-site feedstock handling, and maintenance. The breakdown of OpEx is shown in the following equations:^^^^^^^^^^^^^^^^ = ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^−^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (16)^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = ^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (17)(18), and Celectricity is the electricity price, assumed to be at 64.4 $ / MWh

[0034] .^^^^ = ^^^^ ^^^^ ^^^^ℎ^^^^ (18)where I is the current (calculated from Eqn.15), U is the applied potential, and Nhris the number of operational hours in a year based on the capacity factor of 90%. Non-feedstock operating costs are modeled as 5% of CapEx annually, as suggested by several TEA studies [40-42]. This cost includes labor, on-site feedstock-associated costs, and maintenance.^^^^^^^^^^^^^^^^^^^^^^^^^^^^−^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = 0.05 × ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ℎ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (19)

[0289] Finally, LCOCC was calculated by considering both annual CapEx and OpEx and normalizing by the capture capacity (R; tonneCO2 / year):

[0290] ^^^^^^^^^^^^^^^^^^^^ = ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ℎ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +^^^^^^^^^^^^^^^^^^^^ (20)Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0292] A sensitivity analysis was performed to examine the impact of key variables on the LCOCC. Detailed sensitivity analysis assumptions, including the base values, and lower and upper bounds are presented in Table 10.

[0293] Table 10. The base values and lower and upper bounds of parameters in the sensitivity analysis Upper Variable Base Lower Bound UnitCell lifetime 8 4 12 year Capture capacity 3.1 1 5 MtonneCO2 / year

[0294] Cost Target Analysis for Lower GDE Costs

[0295] With a reduction in the GDE cost to $10 / m2(Figure 18 panel A), achieving a levelized cost below $50 / tonneCO2 becomes more feasible, with an operational zone bounded by efficiencies above 78% and current densities exceeding 220 A / m2. Further reduction of the GDE cost to $5 / m2(Figure 18 panel B) significantly expands this operational zone, allowing for efficiencies above 72% and current densities exceeding 135 A / m2. According to a recent DOE report, GDE costs vary significantly depending on production scale. At commercial-scale production, the cost can be reduced to approximately $5 / m2, while at smaller production scales, the cost increases to around $30 / m2

[0037] . This indicates that achieving these lower GDE costs is realistic at large-scale production, broadening the operational zone for cost-effective CO2 removal. This highlights the potential for achieving more economically favorable carbon capture with improvements in GDE manufacturing costs, which can further optimize the system's cost- effectiveness.

[0296] References Cited Herein

[0297] [1] M. C. Stern, "Electrochemically-mediated amine regeneration for carbon dioxide separations," Thesis, Massachusetts Institute of Technology, 2014. [Online]. Available: dspace.mit.edu / handle / 1721.1 / 87130

[0298] [2] M. Rahimi, K. M. Diederichsen, N. Ozbek, M. Wang, W. Choi, and T. A. Hatton, "An electrochemically mediated amine regeneration process with a mixed absorbent forDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 postcombustion CO2 capture," Environmental Science & Technology, vol. 54, no. 14, pp.8999- 9007, 2020.

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[0339] An Integrated Electrochemical System for Simultaneous Carbon Capture and Conversion

[0340] Efforts to manage carbon dioxide (CO2) have focused on two separate areas: capturing CO2 and converting it into useful products. Traditionally, the role of the capture unit was to separate and concentrate CO2from mixed gas streams, such as flue gas. Conversion systems operated independently, using a purified CO2stream as input—irrespective of how it's captured— to produce value-added chemicals [8, 17]. This resulted in un-coupled systems, operating independently for capture and conversion processes.

[0341] Recent research trajectories, however, are converging towards the development of coupled CO2 capture and conversion systems, especially by utilizing electrochemical processes [10, 18, 19]. These systems function in a sequential manner, where the first electrochemical cell desorbs CO2, which is then channeled to a second cell for conversion. Despite being housed within a single enclosure, the capture and conversion processes remain distinct, facilitated by two separate electrochemical units. The need for two separate cells is because CO2 is typically liberated at the anode of the capture cell, while the conversion to value-added chemicals occurs at the cathode. This necessitates independent electrochemical control for each process, thereby preventing the full integration of capture and conversion into a single cell.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0342] In contrast to this sequential approach, we describe a new concept: a membraneless electrochemical cell equipped with a dual-function gas diffusion electrode (GDE) that serves as a bipolar electrode. This innovative GDE design allows for simultaneous capture and conversion within a single electrochemical environment. The capture-facing side of the GDE is positively charged, functioning as an anode, while the opposite side, designated for conversion, carries a negative charge, operating as a cathode. This bipolar configuration facilitates the direct transfer of CO2from the anodic side, where it is generated, through the GDE, to the cathodic side. Here, it encounters a catalyst layer designed for CO2 conversion into desired chemicals (Figure 19).

[0343] PROCESS SCHEME | The process combines both carbon capture and conversion compartments. In the capture and concentration compartment, an amine (Am) serves as the CO2absorbent. The copper in the bipolar gas diffusion electrode (GDE) undergoes oxidation, releasing copper ions that bond with the amine, facilitating CO2 desorption. This desorbed CO2 is subsequently transferred to the conversion compartment via the bipolar GDE. Meanwhile, the copper-amine complex (Cu-Am) diffuses to the compartment's cathode, where it is reduced to metallic copper, thereby regenerating the amine. This regenerated amine is then ready to capture more CO2from the inlet gas, which is transferred through the GDE on the capture side, forming Am-CO2.

[0344] The conversion compartment is inspired by the state-of-the-art water-fed CO2 electrolyzer utilizing an anion exchange membrane (AEM) and a cation exchange membrane (CEM). As illustrated in Figure 19, CO2, transferred from the capture compartment, undergoes reduction on the CO2 reduction reaction (CRR) catalysis to form formate (HCOO−). This formate subsequently reacts with protons (H+) released at the anode, where oxygen evolution reaction (OER) occurs, leading to the production of formic acid (HCOOH).

[0345] The implementation of this integrated system can be a significant leap forward in carbon management technology. It embodies a holistic approach that is well-aligned with the overarching goals of the energy transition, offering a solution that integrates the mitigation of emissions with the generation of valuable products. The successful demonstration of such a system can not only be a technical success but also a strategic advancement, reinforcing our commitment to a sustainable energy future.

[0346] References Cited HereinDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0347] 1. Stern, M.C., F. Simeon, H. Herzog, and T.A. Hatton, Post-combustion carbon dioxide capture using electrochemically mediated amine regeneration. Energy & Environmental Science, 2013.6(8): p.2505-2517.

[0348] 2. Rahimi, M., F. Zucchelli, M. Puccini, and T. Alan Hatton, Improved CO2 capture performance of electrochemically mediated amine regeneration processes with ionic surfactant additives. ACS Applied Energy Materials, 2020.3(11): p.10823-10830.

[0349] 3. Wang, M., M. Rahimi, A. Kumar, S. Hariharan, W. Choi, and T.A. Hatton, Flue gas CO2 capture via electrochemically mediated amine regeneration: System design and performance. Applied Energy, 2019.255: p.113879.

[0350] 4. Wang, M., H.J. Herzog, and T.A. Hatton, CO2 capture using electrochemically mediated amine regeneration. Industrial & Engineering Chemistry Research, 2020. 59(15): p. 7087-7096.

[0351] 5. Arlota, C. and H.K. de Medeiros Costa, Climate change, Carbon Capture and Storage (CCS), energy transition, and justice: where we are now, and where are (should be) we headed?, in Carbon Capture and Storage in International Energy Policy and Law.2021, Elsevier. p.385-393.

[0352] 6. Lau, H.C., S. Ramakrishna, K. Zhang, and A.V. Radhamani, The role of carbon capture and storage in the energy transition. Energy & Fuels, 2021.35(9): p.7364-7386.

[0353] 7. Baylin-Stern, A. and N. Berghout, Is carbon capture too expensive? International Energy Agency, 2021.

[0354] 8. Bui, M., C.S. Adjiman, A. Bardow, E.J. Anthony, A. Boston, S. Brown, P.S. Fennell, S. Fuss, A. Galindo, and L.A. Hackett, Carbon capture and storage (CCS):the way forward. Energy & Environmental Science, 2018.11(5): p.1062-1176.

[0355] 9. Wang, M., R. Shaw, E. Gencer, and T.A. Hatton, Technoeconomic analysis of the electrochemically mediated amine regeneration CO2 capture process.Industrial & Engineering Chemistry Research, 2020.59(31): p.14085-14095.

[0356] 10. Rahimi, M., A. Khurram, T.A. Hatton, and B. Gallant, Electrochemical carbon capture processes for mitigation of CO2 emissions. Chemical Society Reviews, 2022.51: p.8676- 8695.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0357] 11. Sharifian, R., R. Wagterveld, I. Digdaya, C. Xiang, and D. Vermaas, Electrochemical carbon dioxide capture to close the carbon cycle. Energy & Environmental Science, 2021.14(2): p.781-814.

[0358] 12. Rahimi, M., K.M. Diederichsen, N. Ozbek, M. Wang, W. Choi, and T.A. Hatton, An electrochemically mediated amine regeneration process with a mixed absorbent for postcombustion CO2 capture. Environmental Science & Technology, 2020.54(14): p.8999-9007.

[0359] 13. Hassan, A., A. Refaie, P. Aleta, M. Afshari, E. Kalantari, Y. Fang, and M.M. Rahimi, Reviving the absorbent chemistry of electrochemically mediated amine regeneration for improved point source carbon capture. Chemical Engineering Journal, 2024: p.149566.

[0360] 14. Rahimi, M., T. Kim, C.A. Gorski, and B.E. Logan, A thermally regenerative ammonia battery with carbon-silver electrodes for converting low-grade waste heat to electricity. Journal of Power Sources, 2018.373: p.95-102.

[0361] 15. Al Juaied, M. and A. Whitmore, Realistic costs of carbon capture.2009, Energy Technology Innovation Policy Research Group, Belfer Center for ….

[0362] 16. Vikara, D., C.Y. Shih, S. Lin, A. Guinan, T. Grant, D. Morgan, and D. Remson, US DOE’s economic approaches and resources for evaluating the cost of implementing carbon capture, utilization, and storage (CCUS). Journal of Sustainable Energy Engineering, 2017.5(4): p.307-340.

[0363] 17. Saha, P., S. Amanullah, and A. Dey, Selectivity in electrochemical CO2 reduction. Accounts of chemical research, 2022.55(2): p.134-144.

[0364] 18. Sullivan, I., A. Goryachev, I.A. Digdaya, X. Li, H.A. Atwater, D.A. Vermaas, and C. Xiang, Coupling electrochemical CO2 conversion with CO2 capture. Nature Catalysis, 2021.4(11): p.952-958.

[0365] 19. Li, M., E. Irtem, H.-P. Iglesias van Montfort, M. Abdinejad, and T. Burdyny, Energy comparison of sequential and integrated CO2 capture and electrochemical conversion. Nature Communications, 2022.13(1): p.5398. EXAMPLE 3

[0366] Non-Limiting, Exemplary 13% CO2Optimization and Performance Report

[0367] Operation BasicsDocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025

[0368] Membraneless cell with Cu electroplated GDEs as anode and cathode was used for optimization. The gas channels were facing the outer side of the GDEs with both anode and cathode channels having a fixed flow rate of about 7 ml / min that includes 13% CO2(0.91 ml / min) compared to 87% other gases. All gases were fed through gas flow controllers calibrated for specific gases. Both anode and cathode exiting gas channels had their flow rates measured with gas flowmeters calibrated to detect changes in gas flow rates during the absorption and desorption of CO2.

[0369] Optimization of the Cell

[0370] Cell operating voltage / current can be optimized first. Fixed current is applied for five minutes followed by five minutes of open-circuit voltage (“OCV”). The current polarization is switched to negative thus switching the anode and cathode roles, and the absorption and desorption. Released gases from both anode and cathode channels are measured with GFM on the left and right sides of the cell. Applied currents are in increasing order, starting from 25 mA to 125 mA with an interval of 25 mA each cycle. Voltage increases with the applied current, and corresponding gas flow rates change on the left and right gas flow meters are given in Table 11 as well. Voltage increases with the applied current. Corresponding gas flow rate changes on the left and right gas flow meters are given in Table 11 as well. With increasing current, the desorbed and absorbed CO2 increases, however the absorption after 75 mA goes to a plateau indicating the mass transport limitation of the GDE. For the energetics and efficiency, the lower current 25 mA yields the highest energetics and lowest efficiency because of limited desorption of the CO2. However, at 50 mA, it is slightly lower, although it results in lesser absorption and desorption compared to inlet CO2flowrate (0.91 ml / min), which can require significantly larger sizes of the cell or the CapEx. Figure 20 (Panel A and Panel B) shows this optimization. The most optimized conditions for 13 % is 75 mA. It was selected for further log run experiments. Current 25mA 50mA 75mA 100mA 125mADocket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 Absorption 29.67 56.04 73.63 81.98 80.66 (%) per 0.91 theoptimization of a membraneless cell.

[0372] Long Term Performance at 75 mA

[0373] Cells were run for 50 hours at the optimized point. The operating conditions are in the following order: OCV, +75mA, OCV, -75mA; each was run for 5 minutes, the whole cycle took about 20 minutes before switching the polarization to the same electrode as it was started with. Figure 21 Panel A shows the voltage changes with the applied current. The voltage profiles are not compensated for the Ohmic drop in the cell. Resulting gas flow rate profiles are presented for both the left and right sides in Figure 21 Panel B. The calculated energetics and faradic efficiency after compensating for the voltage with 1.5 Ω (solution resistance) are presented in Figure 21 Panel C. Figure 22 Panels A-C are also provided by limiting the time to the first 5 hours.

[0374] Ion Chromatography Test for Electrolyte Stability

[0375] An ion chromatography test for the electrolyte before and after was performed (Figure 23 Panel A and Panel B). The sulphate was the only ion present in the electrolyte, and notably, no sulphate reduction was detected. The fluorides were not detected, indicating that the PTFE layer coated for the hydrophobicity isn’t damaged. Absence of other ions including nitrate, phosphate, and chloride indicates stable operation. ***** EQUIVALENTS

[0376] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific substances and procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the following claims.

Claims

Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 CLAIMS What is Claimed is:

1. A membraneless electrochemical cell comprising: a power supply; an electrolyte chamber separating two gas diffusion electrodes (GDE), wherein the electrolyte chamber comprises an aqueous absorbent-containing electrolyte solution, wherein one GDE is a cathode gas diffusion electrode (cGDE), and wherein one GDE is an anode gas diffusion electrode (aGDE); a stream gas channel on the exterior of the cGDE, wherein the stream gas channel comprises a stream gas inlet and a stream gas outlet; and a sweep gas channel on the exterior of the aGDE, wherein the sweep gas channel comprises a sweep gas inlet and a sweep gas outlet.

2. The electrochemical cell of claim 1, wherein the aqueous absorbent-containing electrolyte solution comprises a cupric ion source, an amine source, and a background electrolyte.

3. The electrochemical cell of claim 2, wherein: the background electrolyte comprises sodium sulfate (Na2SO4), potassium sulfate (K2SO4), or a combination thereof; the cupric ion source comprises copper (II) sulfate pentahydrate (CuSO4, 5H2O); the amine source comprises ethylenediamine (EDA), monoethanolamine (MEA), or a combination thereof; or any combination thereof.

4. The electrochemical cell of claim 2, wherein: the cupric ion source is present from about 0.1 M to about 0.4 M;Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 the background electrolyte is present from about 0.2 M to about 2.0 M; the amine source is present in a concentration of about 0.5 M to about 1.5 M; or any combination thereof.

5. The electrochemical cell of claim 1, wherein the GDE comprises a gas diffusion layer (GDL), wherein the GDL comprises a porous current collector adjacent to the gas channel; a microporous layer (MPL), wherein the MPL is adjacent to the GDL or integrated into the GDL; and a copper layer (Cu0) adjacent to the MPL or the GDL with the integrated MPL and interfacing with the electrolyte layer.

6. The electrochemical cell of claim 5, wherein: the porous current collector comprises a carbon fiber composite paper or a carbon cloth; and the MPL comprises a conductive composition, a hydrophobic composition, or a combination thereof.

7. The electrochemical cell of claim 6, wherein the conductive composition comprises carbon black.

8. The electrochemical cell of claim 6, wherein the hydrophobic composition comprises polytetrafluoroethylene (PTFE).

9. The electrochemical cell of claim 5, wherein: the copper layer comprises about 0.7 mg / cm2to about 3.3 mg / cm2copper loading; the cell absorbs about 0.01% to about 100% CO2from the stream gas;Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 the cell comprises an absorption capacity of about 0.1 mol CO2 / mol absorbent to about 0.9 mol CO2 / mol absorbent; or any combination thereof.

10. The electrochemical cell of claim 1, wherein the cell does not comprise an anionic exchange membrane (AEM), an absorption column, a flash tank, a pump, or any combination thereof.

11. A method of carbon dioxide separation using the membraneless electrochemical cell of claim 1, the method comprising: applying an electric potential to the membraneless electrochemical cell; flowing a stream gas through the stream gas channel on the exterior of the cGDE, thereby absorbing carbon dioxide present in the stream gas into the cathode gas diffusion electrode (cGDE) and into the absorbent-containing electrolyte solution; and flowing a sweep gas through the sweep gas channel on the exterior of the aGDE, thereby removing the carbon dioxide from the electrolyte solution and desorbing the carbon dioxide through the aGDE.

12. The method of claim 11, wherein the electric potential comprises about 0.5 V to about 1.5 V.

13. The method of claim 11, wherein the stream gas comprises less than 0.01% to about 100% CO2.

14. The method of claim 11, wherein the method comprises a CO2removal efficiency of about 30% to about 100%.

15. The method of claim 11, wherein the method comprises a current density of about 50 A / m2to about 300 A / m2.Docket No.: 2957092-000007-WO1 Date of Filing: October 6, 2025 16. The method of claim 11, wherein the method comprises an energy consumption of about 6 kJ / mol CO2to about 250 kJ / mol CO2.

17. The method of claim 11, wherein the membraneless electrochemical cell operates at a temperature less than 50 degrees Celsius.

18. The method of claim 11, wherein the membraneless electrochemical cell facilitates the transport of the copper-amine complex and CO2 amine complex to their respective electrodes using non-convective forces.

19. The method of claim 18, wherein the non-convective forces comprise a combination of electric forces and concentration gradients.

20. The method of claim 18, wherein the membraneless electrochemical cell operates in batch mode.

21. The method of claim 11, wherein each GDE comprises either a mesh attached assembly or an electrodeposited assembly.

22. The method of claim 21, wherein the mesh attached assembly comprises a metal mesh mechanically attached to a porous carbon-based substrate.

23. The method of claim 21, wherein the electrodeposited assembly comprises metal electrodeposited onto the same porous carbon-based substrate.

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