Electrochemical reactor and method for carbon dioxide capture and reduction

Abstract

A method for capturing carbon dioxide (CO2) includes alternating flow of a gas and a liquid catholyte through a copper-coated channel of a cathode plate, flowing a liquid anolyte through a channel of an anode plate that interfaces with the cathode plate via an anode and an ion exchange membrane, and applying a voltage across the anode and cathode plate. Dilute CO2 feedstocks, such as air, are suitable for use. A method of making an electrochemical reactor includes adhering a lower surface of a cathode plate to an upper surface of an at least one gasket, adhering a lower surface of at least one gasket to an upper surface of a windowless gasket with copper, adhering a lower surface of the windowless gasket to a support, flowing a copper ions though the cathode plate, and applying a voltage across the cathode plate and copper.

Description

ELECTROCHEMICAL REACTOR AND METHOD FOR CARBON DIOXIDE CAPTURE AND REDUCTIONRELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 669,089, filed on July 9, 2024. The entire teachings of the above application(s) are incorporated herein by reference.GOVERNMENT SUPPORT

[0002] This invention was made with government support under Grant No. DE-AR- 0001945 was awarded by the Department of Energy. The government has certain rights in the invention.BACKGROUND

[0003] Recently, there has been a significant interest in developing new methods to synthesize chemicals from alternative, underutilized sources of carbon such as, e.g. carbon dioxide (CO2) in the air. Such methods can reduce the chemical production costs, improve the resilience of the supply chain, and yield environmentally friendly chemical products.However, performing chemical reactions using feedstocks and energy sources different than fossil fuels is challenging.

[0004] There is a need for reactors and methods for energy-demanding chemical transformations.SUMMARY

[0005] Disclosed herein is a reactor that creates a microenvironment for an electrochemical reaction where mass and heat transfer limitations are overcome, creating a highly efficient electrochemical reaction that can be used for energy-demanding chemical transformations (z.e. carbon capture reactions, carbon conversion). The reactor design is modular and scalable, along with the catalysts present described herein.

[0006] Described herein is a method for capturing carbon dioxide (CO2) using an electrochemical reactor that uses an alternating gas and liquid catholyte flow, sometimes referred to as Taylor flow, for converting CO2 into a reduced CO2 product. In some instances, the reduced CO2 product that is formed is ethanol. The electrochemical reactor uses a cathode- 1 -4188550.V1plate with a channel that is coated with copper to achieve conversion to the reduced CO2 product.

[0007] Also described herein is a method of making the electrochemical reactor by electroplating copper onto a channel that is within a cathode plate by using a copper solution and an applied electrical potential.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIGs. 1 A-B are schematics comparing the reactive environment available in the currently used liquid phases electrochemical reactors (FIG. 1 A) vs the reactive environment of the present disclosure (FIG. IB).

[0009] FIG. 2A is a general schematic of a cross section of an electrochemical reactor and components of the electrochemical reactor. Also shown is a schematic of the formation of Taylor flow to the electrochemical reactor.

[0010] FIG. 2B is a schematic of a cross section of a copper-coated electrochemical reactor and components of the copper-coated electrochemical reactor.

[0011] FIG. 3A is a graph with a current recorded while applying -2.5 V of voltage against the counter electrode with an inset image of the Taylor flow slugs.

[0012] FIG. 3B is an1H NMR spectra of liquid products from Taylor flow reactor using air as the carbon source. DMSO is used as an internal standard for NMR measurement and is added after the reaction.

[0013] FIG. 4 is a graph of delivered current on a hybrid electrode in an electrochemical reactor with NF / NiFe oxygen evolution reaction (OER) catalyst as the anode; testing in KOH IM at 100 mA / cm2.

[0014] FIG. 5 is a cross-sectional view of a schematic of a transparent straight flow electrochemical reactor. The Taylor slug flow is created at the junction of the catholyte and gas inlet.

[0015] FIG. 6A is a photograph of a titanium plate without a catalyst.

[0016] FIG. 6B is a photograph of a titanium plate with a catalyst directly attached to the gasket.

[0017] FIG. 6C is a photograph of a titanium plate with a catalyst taped to the inner walls of the plate.

[0018] FIGs. 6D and 6E are graphs comparing catalysts for the production of CO2RR products at 45 mA (FIG. 6D) and 175 mA (FIG. 6E).- 2 -4188550.V1

[0019] FIG. 7A is a schematic of an electrochemical reactor with serpentine geometry for electroplating copper onto the channels of the cathode plate.

[0020] FIG. 7B is a photograph of the serpentine geometry and copper catalyst plated cathode plate.

[0021] FIG. 7C is a schematic of a flow plate with a channel having a serpentine arrangement.

[0022] FIG. 8 A is a graph showing reactivity of adding Tith nanoparticles to the catholyte in the electrochemical reactor with the Faradaic efficiency of converting CO2 to ethanol.

[0023] FIG. 8B is a graph of the applied potential to the electrochemical reactor with added Tith nanoparticles to the catholyte.

[0024] FIG. 9A is graph of the influence of the gas-to-liquid (G / L) ratio on the full cell potential. Liquid only flow was 20 pl / s, 0.5 liquid to gas (L:G) was 20 pl / s for both liquid and gas, 0.315 L:G was 27.2 pl / s for gas, and 8.6 pl / s for liquid.O.lM KHCO3 was used as the electrolyte.

[0025] FIG. 9B is a graph of the Faradaic efficiency of converting CO2 to formate. Liquid only flow was 20 pl / s, 0.5 L:G was 20 pl / s for both liquid and gas, 0.315 L:G was 27.2 pl / s for gas, and 8.6 pl / s for liquid.O.lM KHCO3 was used as the electrolyte.

[0026] FIG. 10 is a simplified flow diagram of the electrochemical reactor integrated into method for the synthesis of ethanol from air.DETAILED DESCRIPTION

[0027] A description of example embodiments follows.

[0028] As used herein “about” means within an acceptable error range for the particular value, as determined by one of ordinary skill in the art. Typically, an acceptable error range for a particular value depends, at least in part, on how the value is measured or determined, e.g., the limitations of the measurement system. For example, “about” can mean within an acceptable standard deviation, per the practice in the art. Alternatively, “about” can mean a range of ± 20%, e.g., ± 10%, ± 5% or ± 1% of a given value. It is to be understood that the term “about” can precede any particular value specified herein, except for particular values used in the Exemplification.- 3 -4188550.V1

[0029] Carbon dioxide in the ambient air could be an excellent source of carbon used to synthesize fuels; however, its low concentration (400 ppm) makes it difficult to realize this chemical reaction.

[0030] Several electrochemical reactions, i.e., converting abundant carbon dioxide (CO2) to fuels, are realized by supplying gaseous feedstock to a liquid reactive phase. In such embodiments, mass transfer processes are slow, forming a so-called boundary layer in the vicinity of the cathode material. This layer prevents fast replenishing of the gaseous feed materials, and the thicker this layer is, the lower the current density achievable in the electrochemical system (measured in mA / cm2or A / cm2). It is difficult to achieve more than 1-10 mA / cm2when converting CO2 to liquid fuels (i.e., ethanol) or similar reactions (1). Since the current density is directly proportional to the output of the products from the reactor, it needs to be minimum of 100 mA / cm2to enable industrial applications (FIG. 1A). So far, such higher current densities have been reported only in gas-diffusion electrode reactors, which require the development of hydrophobic interfaces on the electrodes, which in turn makes the electrocatalytic materials prone to fast and non-reversible degradation. (2)

[0031] To overcome these challenges, the design described herein allows to operate the electrochemical reactions in a favorable, liquid environment. The design integrates a slow, controlled flow of large bubbles in the channels of the electrochemical reactor, which pushes the liquid on top of the electrode to a very thin layer; thus, the distance between the gas and liquid molecules and the thickness of the boundary layer is reduced by factor of 50-100 (FIG. IB). In addition to this, Taylor flow was incorporated into planar electrodes instead of simple metal rods that were previously reported in literature (3), making this design modular, scalable, as well as drastically improving current collection. As a result, current densities of 100 mA / cm2or higher are achieved, which were never reported for liquid-phase electrochemical reactions.

[0032] Electrochemical reactions are usually performed by contacting a gaseous feed with a liquid phase under room temperature and normal pressure - which is beneficial from the point of view of energy use and resources availability but difficult to realize with an efficiency that could yield an industrially-relevant chemical production process.

[0033] An electrochemical microtubular reactor allows for the creation of an in situ, biphasic gas-liquid flow (called Taylor flow), and performs the reactions in a favorable liquid environment, under conditions of intensified mass transfer. The reactor was designed to minimize the liquid film thickness on the side walls of the reactor channel, so that the reactor- 4 -4188550.V1side wall can be used as a catalytically active surface area with minimized mass transfer. Due to this, it is possible to significantly increase the area covered with catalyst, and therefore use a smaller reactor to produce a higher output of value-added chemicals.Method for Capturing Carbon Dioxide (CO2)

[0034] Described herein is a method for capturing carbon dioxide (CO2). The method can include alternating flow of a gas and a liquid catholyte through a copper coated channel of a cathode plate, flowing a liquid through a channel of an anode plate that interfaces with the cathode plate via an anode and an ion exchange membrane, and applying a voltage across the anode and the cathode plate, thereby forming a reduced CO2 product. The gas (such as air) can have a CO2 concentration less than about 350,000 parts per million (ppm).

[0035] An “electrolyte” is a compound (z.e. an acid, a base, or a salt) that conducts an electrical current in solution. A “catholyte” is an electrolyte dissolved in a liquid that contacts the cathode of the electrochemical reactor. An “anolyte” is an electrolyte dissolved in a liquid that contacts the anode of the electrochemical reactor. In some aspects, the catholyte comprises potassium hydroxide (KOH), potassium chloride (KC1), potassium bromide (KBr), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), sodium hydroxide (NaOH), sodium chloride (NaCl), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCXT), calcium hydroxide (Ca(OH)2), calcium chloride (CaCh), calcium carbonate (CaCOs), calcium bicarbonate (Ca(HCO3)2), barium chloride (BaCh), cesium hydroxide (CsOH), cesium carbonate (CS2CO3), cesium bicarbonate (CsHCOs), polyethylene glycol dimethyl ether, methanol, polyethylene glycol methyl isopropyl ether, propylene carbonate, N-methyl- 2-pyrrolidone, tributyl phosphate, methylcyanoacetate, glycerol, tetrahydrotiphene dioxide, or butanol. In some aspects, the liquid comprising the catholyte further comprises titanium dioxide (Tith) nanoparticles. In some aspects, the anolyte comprises potassium hydroxide (KOH), potassium chloride (KC1), potassium bromide (KBr), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), sodium hydroxide (NaOH), sodium chloride (NaCl), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCOs), calcium hydroxide (Ca(OH)2), calcium chloride (CaCh), calcium carbonate (CaCOs), calcium bicarbonate (Ca(HCO3)2), barium chloride (BaCh), cesium hydroxide (CsOH), cesium carbonate (CS2CO3), cesium bicarbonate (CsHCXh), polyethylene glycol dimethyl ether, methanol, polyethylene glycol methyl isopropyl ether, propylene carbonate, N-methyl-2-pyrrolidone, tributyl phosphate, methylcyanoacetate, glycerol, tetrahydrotiphene dioxide, or butanol. In some aspects, the- 5 -4188550.V1catholyte is 1 M KOH or 1 M KHCO3. In some other aspects, the catholyte is KOH, e.g., IM KOH. In some aspects, the anolyte is KOH, e.g., IM KOH.

[0036] In some aspects, the applied voltage is about -4V to about 3 V. In some further aspects, the applied voltage is about -3V to about 3V.

[0037] In some aspects, the residence time for the flowing gas is from about 0.002s to about 0.2s. In some aspects, the residence time for the flowing liquid catholyte is from about 0.001s to about 0.1s. In some other aspects, the residence time for the flowing liquid anolyte is about 0.000002s to about 0.2s.

[0038] In some aspects, flowing the gas is at a rate from about 1 pL / s to about 700 pL / s. In some further aspects, flowing the gas is at a rate from about 1 pL / s to about 500 pL / s. In some further aspects, flowing the gas is at a rate from about 1 pL / s to about 250 pL / s. In some further aspects, flowing the gas is at a rate from about 1 pL / s to about 100 pL / s. In some further aspects, flowing the gas is at a rate from about 5 pL / s to about 50 pL / s. In some further aspects, flowing the gas is at a rate from about 9 pL / s to about 11 pL / s.

[0039] In some aspects, flowing the liquid catholyte is at a rate from about 1 pL / s to about 700 pL / s. In some further aspects, flowing the liquid catholyte is at a rate from about 1 pL / s to about 500 pL / s. In some aspects, flowing the liquid catholyte is at a rate from about 1 pL / s to about 250 pL / s. In some aspects, flowing the liquid catholyte is at a rate from about 1 pL / s to about 100 pL / s. In some further aspects, flowing the liquid catholyte is at a rate from about 10 pL / s to about 50 pL / s. In some further aspects, flowing the liquid catholyte is at a rate from about 14 pL / s to about 18 pL / s.

[0040] In some aspects, flowing the liquid anolyte is at a rate from about 5 mL / min to about 350 mL / min. In some further aspects, flowing the liquid anolyte is a rate from about 5 mL / min to about 250 mL / min. In some further aspects, flowing the liquid anolyte is a rate from about 5 mL / min to about 150 mL / min. In some further aspects, flowing the liquid anolyte is a rate from about 5 mL / min to about 50 mL / min. In some further aspects, flowing the liquid anolyte is at a rate from about 7 mL / min to about 20 mL / min. In some further aspects, flowing the liquid anolyte is at a rate from about 9 mL / min to about 11 mL / min. In some other aspects, a peristaltic pump generates flow for the anolyte.

[0041] In some aspects, applying the voltage generates a current density of at least 100 mA / cm2. In some aspects, applying the voltage generates a current density of about 100 mA / cm2to about 300 mA / cm2. In some further aspects, applying the voltage generates a- 6 -4188550.V1current density of about 125 mA / cm2to about 175 mA / cm2. In some further aspects, applying the voltage generates a current density of about 150 mA / cm2to about 170 mA / cm2.

[0042] As used herein “reduced CO2 product” refers to CO2 converted into a hydrocarbon molecule by adding at least two electrons to the carbon of CO2, thereby reducing the carbon and resulting in the carbon of the CO2 to bond with other atoms it interacts with. “Reduced CO2 product,” “CO2R product,” and “CO2RR product” are used interchangeably throughout this disclosure. In some aspects, the reduced CO2 product is one or more of methanol, ethanol, propanol, isopropanol, methane, formic acid, ethylene, and propylene. In some further aspects, the reduced CO2 product is ethanol. In some further aspects, the Faradaic efficiency of ethanol is about 5% to about 80%. In some further aspects, the Faradaic efficiency of ethanol is about 10% to about 50%. In some aspects, the reduced CO2 product is dissolved in or miscible with the liquid catholyte. In some aspects, the method further involves collecting the liquid catholyte comprising the reduced CO2 product. The liquid catholyte can be further distilled to separate the reduced CO2 product to be collected.

[0043] A “cathode plate” has an internal channel that allows for liquid and / or gas to flow therethrough from an inlet port to an outlet port. Typically, flow is driven by an exterior force (z.e. gravity, a pump, a syringe, multiple syringes). The flow circulates to the inlet port via tubing and the flow exits the plate from the outlet port that may be connected to tubing. The tubing of the outlet port may be connected to a pump to recirculate the flow back into the cathode plate. The cathode plate itself is in contact with a cathode catalyst. The cathode catalyst can be copper. In some aspects, the cathode catalyst can be porous. The cathode plate can have a copper-coated channel. In some aspects, the copper-coated channel of the cathode plate comprises electrodeposited or electroplated copper. In some aspects, the copper-coated channel of the cathode plate has a serpentine arrangement. In some aspects, the copper-coated channel of the cathode plate is further coated with Tith nanoparticles. In some aspects, the copper-coated channel of the cathode plate has a cross-sectional area of about 16 mm2to about 90,000 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 1,000 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 100 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 81 mm2.

[0044] The cathode plate may be described further herein as a “cathode flow field plate.” This terminology is used interchangeably throughout the present application and has the meaning of a “cathode plate.”- 7 -4188550.V1

[0045] An “anode plate” has an internal channel that allows for liquid and / or gas to flow therethrough from an inlet port to an outlet port. Typically, flow is driven by an exterior force (z.e. gravity, a pump, a syringe, multiple syringes). The flow circulates to the inlet port via tubing and the flow exits the plate from the outlet port that may be connected to tubing. The tubing of the outlet port may be connected to a pump to recirculate the flow back into the anode plate. The anode plate contacts an anode catalyst. Anode catalysts are known in the art, and non-limiting examples include: platinum, titanium, nickel, iron, nickel-iron foam, stainless steel, and copper. In some aspects, the anode catalyst may be porous. In some aspects, the channel of the anode plate has a serpentine arrangement. In some aspects, the channel of the anode plate is further coated with Tith nanoparticles. In some aspects, the channel of the anode plate has a cross-sectional area of about 16 mm2to about 90,000 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 1,000 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 100 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 81 mm2.

[0046] The anode plate may be described further herein as a “anode flow field plate.” This terminology is used interchangeably throughout the present application and has the meaning of a “anode plate.”

[0047] In some aspects, the gas has a concentration of CO2 of about 400 ppm to about 350,000 ppm. In some further aspects, the gas has a concentration of CO2 of about 400 ppm to about 300,000 ppm. In some aspects, the gas has a concentration of CO2 of about 400 ppm to about 1,000 ppm. For example, the methods described herein do not require concentrated (e.g., pure) CO2 feedstock. In other words, the method can be used to capture dilute, gaseous CO2, such as CO2 in ambient air. More concentrated feedstocks can also be used, but are not required. For example the feedstock for methods described herein can be an effluent from a power plant, where the CO2 concentration can be approximately 140,000 ppm, or other source of CO2 resulting from hydrocarbon combustion.

[0048] The ion exchange membrane can be an anion exchange membrane, a cation exchange membrane (e.g., a proton exchange membrane), or a bipolar membrane. In some preferred embodiments, the ion exchange membrane is an anion exchange membrane. The choice of membrane can affect the selectivity for formation of reduced CO2 product.

[0049] Alternating flow of gas and liquid catholyte is sometimes referred to as “Taylor flow” or “TF.” Taylor flow, also called “slug flow,” refers to a flow regime observed in two- phase systems where gas bubbles and liquid slugs alternate within a confined channel. This- 8 -4188550.V1flow pattern can appear as elongated bubbles with a diameter that can be larger than the channel diameter (z.e. the bubble diameter is measured across the length of the channel rather than the diameter of the channel, whichever is larger) that may have a capsular shape, with a thin liquid film separating the gas bubble from the channel walls.

[0050] In some aspects, alternating flow of gas and liquid catholyte (z.e., Taylor flow) is initiated outside of the cathode plate. FIGs. 2A and 2B show the liquid catholyte 229 and the gas 230 enter a junction 231 to form the alternating gas bubble 220 and liquid catholyte slug 221 flow that enters the cathode plate 222 and leaves the cathode plate after interacting with the cathode 223 of FIG. 2A or the copper-coated cathode plate channel 222 of FIG. 2B. The alternating flow of gas and liquid catholyte is maintained throughout the cathode plate and upon exiting the cathode plate. Upon entering the cathode plate 222, voltage is applied to the cathode 222 and the anode 226 while the anolyte 228 flows through the anode plate 227 while the alternating gas and liquid catholyte flows through the cathode plate. Ions pass through the ion exchange membrane 225 held within the gasket 224 of the electrochemical reactor. The combination of the cathode, anode, and the membrane enables the reduction reaction of CO2 within the gas to form a reduced CO2 product. The reduced CO2 product exits the cathode plate via the outlet port, along with the liquid catholyte and unreacted gas. The serpentine channel arrangement for the copper-coated channel of the cathode plate and channel for the anode plate is shown in FIGs. 7B and 7C. When the plate is used as a cathode plate, alternating gas and liquid catholyte enter an inlet port 774 and flow through the serpentine channel 775 to exit through the outlet port 776. When the plate is used as an anode plate, anolyte enters an inlet port 774 and flows through the serpentine channel 775 to exit through the outlet port 776.

[0051] In some other aspects, the alternating flow of gas and liquid catholyte may be formed within the cathode plate. FIG. 5 shows an electrochemical reactor with two inlet ports 555 and 556 on the support plate 551. Gas and liquid catholyte enter from each respective inlet port to generate the alternating flow. The gas 554 and liquid catholyte flow through the channel of the cathode plate 552 to the outlet port 550 while interacting with the cathode adhered to a gasket 553. Simultaneously, liquid anolyte 558 enters through the inlet port 562 of the support plate 560 and flows through the channel of the anode plate 558 the outlet port 557 of the anode plate. The liquid anolyte interacts with the anode adhered to a gasket 559. The flow across both plates occurs while a voltage is applied across the cathode 553 and anode 559, resulting in transfer of ion across the ion exchange membrane 561 within a- 9 -4188550.V1gasket. The combination of the cathode, anode, and the membrane enables the reduction reaction of CO2 within the gas to form a reduced CO2 product. The reduced CO2 product exits the cathode plate via the outlet port 550.Method for Electroplating Copper onto an Electrochemical Reactor

[0052] Described herein is a method of making an electrochemical reactor. The method can include adhering a lower surface of a cathode plate comprising a channel therein to an upper surface of at least one gasket comprising a window, adhering a lower surface of the at least one gasket to an upper surface of a windowless gasket, wherein the windowless gasket comprises copper adhered to at least a potion of its upper surfaces, adhering a lower surface of the windowless gasket to an upper surface of a support, flowing a liquid catholyte comprising copper ions through the channel of the cathode plate, and applying a voltage across the cathode plate and the copper, thereby electroplating copper onto the channel of the cathode plate.

[0053] In some aspects, a gasket comprising a window refers to a gasket that has a hole cut through the gasket so the channel of the cathode plate is exposed to the next layer of the electrochemical reactor. In some aspects, at least one gasket may be one gasket, two gaskets, three gaskets, four gaskets, five gaskets, six gaskets, seven gaskets, eight gaskets, nine gaskets, or ten gaskets. In some aspects, the at least one gasket comprising a window refers to one gasket to five gaskets. In some aspects, the at least one gasket comprising a window refers to three gaskets. In some aspects, the at least one gasket comprising a window is made out of a non-electricity conducting material. In some aspects, the non-electricity conducting material is rubber.

[0054] In some aspects, a windowless gasket refers to a gasket that has a compartment to place or adhere copper to the gasket, without allowing for liquid or gas to pass through the gasket. In some aspects, the copper is a porous copper, such as copper mesh.

[0055] In some aspects, the support is made out of a solid material that is rigid. In some further aspects, the support is made out of a metal material. In some aspects, the support is a metal plate. In some further aspects, the support is an anode plate. If the support is an anode plate (like the anode plate described in the “Method for Capturing Carbon Dioxide”), a liquid anolyte does not need to flow through the anode plate as the support is non-reactive in the electroplating process. The anode plate may be used in this process out of convenience and ensuring a strong adherence.- 10 -4188550.V1

[0056] In some aspects, adhering refers to using screws, bolts, clamps, or glue to combine the components of the electrochemical reactor described herein, so there is liquid and / or gas that may escape the electrochemical reactor unless the liquid and / or gas is leaving the electrochemical reactor by design (z.e. an outlet port).

[0057] In some aspects, the catholyte comprises copper (II) ions. In some aspects, the catholyte comprises copper (II) sulfate. In some other aspects, the residence time of the liquid catholyte is from about 0.000002s to about 0.002s. In some aspects, the flowing the liquid catholyte is at a flow rate of about 1 mL / min to about 100 mL / min. In some further aspects, the flowing the liquid catholyte is at a flow rate of about 5 mL / min to about 50 mL / min.

[0058] In some aspects, the channel of the cathode plate has a serpentine arrangement. In some aspects, the channel of the cathode plate has a cross-sectional area of about 16 mm2to about 90,000 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 1,000 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 100 mm2. In some further aspects, the cross-sectional area is about 16 mm2to about 81 mm2.

[0059] In some aspects, the voltage applied across the cathode plate and copper is from about 1 V to about 3 V for about 2 minutes to about 40 minutes.

[0060] FIG. 7A illustrates how the electrochemical reactor is made by flowing a liquid catholyte comprising copper ions 778 into the cathode plate 770 that is separated by the at least one gasket comprising windows 771. The copper 777 adhered to the windowless gasket 772 adhered to the support 773 has a voltage applied across the copper and cathode plate, allowing for electroplating of copper onto the channel of the cathode plate.EXEMPLIFICATIONElectrochemical reactor

[0061] The electrochemical reactor of the present disclosure has multiple designs. In general, the electrochemical reactor has several plates, allowing Taylor flow to the reactor to contact the cathode catalyst, membrane, anode catalyst, and current collection. The general reactor scheme can be seen in FIG. 2, along with the schematic for the generation of Taylor flow that forms at a junction or pipe T-fitting.

[0062] In general, the electrochemical reactor is assembled with a stainless-steel, copper or titanium cathode flow field plate that can have serpentine geometry. The cathode flow field plate is supplied with gas (i.e., at a flow rate of ~10pL / s) and electrolyte (z.e., 0.1 M- 11 -4188550. vlliquid potassium bicarbonate at a flow rate of 16 pL / s) to the same inlet tube to induce the slugs indicative of Taylor flow. There is a sealing gasket with a cut out of its center that accommodates the cathode that is attached to the cathode flow field plate (222 of FIG. 2A). Preferably, the cathode can be a porous cathode (z.e., copper mesh, copper on a porous, polymeric support) adhered to the gasket (223 of FIG. 2 A), with a conductive tape against the cathode flow field plate, but a nonporous cathode (copper tape) can be used as well. An additional sealing gasket (224 of FIG. 2A) is attached to the cathode gasket, with a membrane (z.e. anion exchange membrane; 225 of FIG. 2) attached to another sealing gasket with a cut out to accommodate the anode catalyst (226 of FIG. 2A). The porous anode catalyst (z.e., iron-plated nickel foam) is adhered to the gasket (226 of FIG. 2A) along with conductive tape against the anode flow field plate (227 of FIG. 2A). The anode flow field plate can be made of titanium, nickel, copper or stainless steel and can also have serpentine geometry. The anolyte (z.e., 0.1 M potassium bicarbonate) flows at a rate of ~10 mL / min and is flowed through the anode flow field plate via a peristaltic pump.

[0063] In one specific design, the thin film is effectively created on the side walls, using our reactor design. A plate reactor was used to create a Taylor flow in a Ti flow field with a channel of 1.6 x 2.5 x 70 mm (FIG. 5), designed around two transparent Polymethyl Methacrylate (PMMA) plates (92 x 22 mm), one cathode side and one anode side. Each plate is designed with ten four mm screw holes around the edge, which when put together are tightened to around one N.m. Each plate has two ~5.5 mm-thick PMMA plates, put together with cyanoacrylate super glue. The top plate has inlets of 3.28 mm to fit l / 8th inch tubing tightly, and the bottom plate has inlets of 2.2 mm. The cathode plate has three inlets: two at the bottom, 5 mm apart, and one at the top ~65 mm from the bottom inlet. The bottom-most inlet is used for catholyte flow, and the inlet 5 mm above is used for gas flow to form the Taylor slug flow. The anode plate has the same top and bottom inlet but no third inlet. The PMMA plate then has a silicon gasket placed between it and a metal flow field to ensure no leaks occur. The catalyst, another silicon membrane, and the ion exchange membrane are placed on this flow plate. This is repeated in a mirrored direction until the other PMMA plate is put on top and tightened together. This reactor allows for a direct observation of the formation of Taylor flow (TF) and correlating changes in bubble sizes and shapes to the technical metrics of interest, such as current density, full cell potential, or selectivity to the product of interest.- 12 -4188550. vl

[0064] Using the reactor of FIG. 5, an electrochemical reduction of carbon dioxide (CO2RR) was performed and CO2RR products were measured based on different reaction parameters that were used: a) empty, catalyst-free Ti flow field 660, b) catalyst 661 (Cu mesh, Cu foam, Cu gauze, Cu foil, Cu electroplated on a Carbon paper) directly attached to the flow field, c) catalyst 662 directly attached to the gasket (FIGs. 6A and 6B). Regardless of the applied current, experiments with the catalyst attached to the Ti plate (with a gasket or not, result were the same) resulted in hydrogen being the main product, and hydrogen evolution (HER) was similar for the case of the catalyst-free Ti plate and plate with the catalyst (FIG. 6D). This indicates that the flow field side walls (bare Ti in all cases) were the dominant surface for the reaction. It was further confirmed by covering the inner wall with Cu tape (FIG. 6C), and indeed, this was only the case where CO2RR products were detected. In contrast to the existing designs for gas-diffusion electrode, membrane-electrode assemblies, or other high current density CO2RR reactors, the reactor allows using the inner walls as a dominant surface for catalysis.

[0065] To further improve upon the electrochemical reactor, a catalyst synthesis procedure was developed to cover the inner walls of the reactor with a catalyst of choice (z.e., Cu, Ag, Sn, bi- or trimetallic combinations of catalysts). Using electroplating or electroless plating, both methods were widely studied in the literature for the deposition on flat surfaces (z.e., metal foils, gas diffusion electrodes), but never reported as a way to attach the catalyst to the inner walls of the reactor. For the catalyst of choice, a plating solution is circulated through a peristaltic pump through a flow reactor with a flow rate from 0 to 100 ml / min, as depicted in FIG. 7A, and the applied potential and residence time allow to control the shapes and size of deposited particles. Exemplary applications of this process include depositing Cu on the walls of a titanium flow field. Process parameters are given in Table 1, and the catalyst deposited in channels in FIG. 7B. The depicted catalyst was used to perform CO2 electroreduction, and we obtained 10.5% Faradaic efficiency to ethanol at 100 mA / cm2. FIG. 7C further indicates the inlet and outlet port of the catalyst plated flow field exhibiting serpentine geometry.4188550. vlTable 1. Copper electroplating synthesis procedure for in-flow inner walls plating.2-Electrode, Flow CellCu Plating Solution 0.15 M CuSCU + 0.5 M H2SO4Working Electrode Flowfield plateCounter Electrode 6.25 cm2Cu MeshReference ElectrodeFlow Rate (mL / min) 20Applied Potential -0.3 V, 20 min.Average Current Density (mA / cm2) -18

[0066] To further enhance selectivity in the electrochemical reactor, improving the catalyst wettability was found to increase the selectivity towards liquid products, as increasing the hydrophilicity can improve the formation of TF itself. Two approaches to implement this into the reactor are possible: i) adding titanium dioxide (TiCh) nanoparticles to the electrolyte, or ii) pre-treating the catalytic surface with TiCh soaking.

[0067] TiCh nanoparticles were added in concentrations between 0.02 and 0.2 wt.% in a IM KOH solution and used this as the catholyte in the catalyst-coated serpentine reactor. Increasing the surface hydrophilicity allowed for an increase in Faradaic efficiency (FE) to ethanol by a factor of up to 2.5 without increasing the overpotential (FIG. 8B), and a lower concentration proved to be more effective (FIG. 8A). This effect was also observed by surface pre-treatment with TiO2 to the catalyst using a TiO2 solution. Consistent reduction of the wetting angle post-treatment was observed and confirmed that it can be maintained after electrolysis.Synthesis of Liquid Fuels Directly from Air

[0068] The electrochemical reactor was fed with 10 pL / s gas flow and 16 pL / s catholyte flow (0.1 M KHCOs). Anolyte was circulated with a peristaltic pump, copper mesh was used as a cathode catalyst, and electroplated nicked foam was used as an anode catalyst. The full cell voltage applied was -2.5 V (vs. counter electrode, electroplated nickel foam), FIG. 3 A. The electrochemical reactor was able to achieve around 190 mA / cm2of current density in a liquid environment, being at least an order of magnitude improvement of the state of the art. 2.5 V of applied current corresponds to over 50% energy efficiency, among the most energyefficient electrochemical reactors reported in the carbon conversion field (4). The achievable- 14 -4188550. vlcurrent while using pure CO2 instead of air was compared and noted only a 1% difference, suggesting that the reactor is well suited to operate with diluted feedstocks. Liquid samples were collected after 5, 10, and 45 minutes and analyzed by 700 MHz Bruker Avance NMR. The consistent appearance of ethanol peaks corresponds to ca. 20% selectivity towards ethanol (FIG. 3B); notably, a simplified copper mesh was used as a catalyst and did not optimize the catalyst. Literature reports do not show any significant ethanol synthesis on an inactivated copper mesh (5), confirming that the microenvironment within the reactor contributed to conversion of air to ethanol.

[0069] In another example, the electrochemical reactor can selectively synthesize ethanol, formate, or propanol using either concentrated carbon dioxide or air directly. This process uses a titanium reactor that comprises a serpentine flow field, where the TF is created in channels of ~0.7 mm x 0.7 mm, with a total channel length of 26 mm, and another serpentine flow field of the same dimensions for the anolyte flow, separated with rubber gaskets.Reactor plates are directly used for current collection. The inner channels of the reactors were covered with Cu catalyst deposited through the procedure described herein.

[0070] Product selectivity can be manipulated by using different gas-to-liquid (G / L) ratios in the electrochemical reactor. Different ratios of G / L allow to create slugs of different sizes, which in turn affect the product selectivity. Out of all G / L ratio tested, bubbles created under the same ratio of gas to liquid (label “0.5 L:G”) result in a higher potential (e.g., than for large gas slugs “0.315 L:G”), FIG. 9A. All G / L ratios are similarly stable over time. The bubbles created under the same ratio of gas to liquid (label “0.5 L:G”) resulted in a significant increase in the FE towards formate (FIG. 9B). Further, exemplary data is shown in Table 2.- 15 -4188550. vlTable 2. Exemplary experimental results for the use of the reactor, with copper cathode catalyst deposited on the cathode flow field plate and an Ni / NiFe anode. Note that due to the high dilution of the gaseous products, hydrogen quantification cannot be performed with the same accuracy as the quantification of liquid products (and therefore all Faradaic efficiencies do not sum up to 100%).

[0071] The full process of using the electrochemical reactor is further described. In the absence of carbon or nitrogen reducing catalysts, and in the presence of oxygen evolution catalyst on the anode side, and an anion exchange membrane which was previously immersed in a bicarbonate solution. The created slug flow allows for an efficient contact between the gaseous phase, comprising CO2 of concentration between 100 ppm to 35 mol%, preferably between 400 ppm and 30 mol%, and the solvent, which preferentially dissolves CO2 out of the gaseous mixture. Exemplary solvents are listed in Table 3. An exemplary embodiment of this process, where 1 M potassium hydroxide solution (IM KOH) was used as a solvent in a potential-free system, allowed us to capture 1.49 g of CO2 per g of solvent, using air directly.4188550. vlTable 3. Exemplary solvent to be used for CO2 capture in the proposed system.Solvent class Solvent nameAminesAmmoniaSalts Potassium HydroxidePotassium CarbonatePotassium BicarbonatePotassium ChlorideSodium HydroxideSodium CarbonateSodium BicarbonateCalcium HydroxideCalcium CarbonateCalcium BicarbonatePotassium ChloridePhysical solventsDimethyl ether of polyethylene glycolsMethanolPolethylene glycol methyl isopropyl etherPolypropylene carbonateN-Methyl- 2-PyrrolidoneTributyl phosphateMethylcyanoacetateGlycerolTetrahydrotiphene dioxideButanol

[0072] A process for forming ethanol from air is shown in FIG. 10 (simplified process diagram), along with how the reactor may be scaled up to use. Gas and a catholyte mixture (R-101) enter a reactor on the cathode side of the reactor, and the anolyte mixture (R-106) enters on the anode side of the reactor. After passing through the electrochemical reactor, gas and catholyte (R-102) are sent to a phase split unit where unreacted gas is separated from the catholyte (phase separation under atmospheric pressure; unreacted air is released to the atmosphere). Subsequently, catholyte stream (S-101) is sent to a vacuum membrane distillation unit, where ethanol and pure water are separated from the catholyte stream. The catholyte stream (S-106) is recycled back to the electrochemical reactor, after replenishing water through a make-up unit (S-105). The purge stream (S-l 10) is used to remove the impurities and oxygen from the unit. Ethanol and water separated through the vacuum membrane distillation can be further purified by a subsequent membrane separation unit, if a purity over 40 vol% ethanol is needed.4188550. vl

[0073] On the anode side of the reactor, anolyte is also sent to a phase separation unit (R- 103) to remove oxygen produced at the anode side (phase separation under atmospheric pressure), oxygen is released to the atmosphere (R-l 10) or collected in cylinders water is added to the anolyte (R-107) and the anolyte is recycled back to the reactor (R-106).Anode-Electroplating Procedure

[0074] The anode described in the present disclosure involve the use of a Nickel (Ni) based anode synthesized following the procedure given below. Ni foam was immersed in a plating solution containing Earth-abundant metals at various concentrations, such as 3 mM Ni(NO3)2.6H2O and 3 mM Fe(NO3)3.9H2O and used as a working electrode for the Ni / Fe deposition process. 3 M Ag / AgCl was used as the reference electrode, and carbon paper as the counter electrode, and the electrochemical deposition of Ni / Fe was performed during 10 mins under 1 V of applied potential. Notably, better results using carbon paper as the counter electrode as opposed to more common counter electrode materials such as platinum were obtained.

[0075] The significant improvement of the electrochemical performance is enabled by the “Hybrid electrode System”, where the counter electrode used for electrodeposition differs from the one used for a specific application. Data showed a significant increase in the current being delivered on this reaction setup and stable performance of the catalyst over time of use, with just slight oscillation throughout the process. The catalytic performance of the synthesized material on alkaline medium testing is shown in FIG. 4 with a high current density of 167.099 mA / cm2at 1.6 V, which is higher when compared to previous studies using just a classic single synthesis-testing cell setup for OER catalysts (6).REFERENCES

[0076] 1. T. Burdyny, W. A. Smith, CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions. Energy Environ. Sci. 12, 1442-1453 (2019).

[0077] 2. M. K. Kovalev, H. Ren, M. Zakir Muhamad, J. W. Ager, A. A. Lapkin, MinorProduct Polymerization Causes Failure of High-Current CO 2 -to-Ethylene Electrolyzers. ACS Energy Lett. 7, 599-601 (2022).- 18 -4188550. vl

[0078] 3. F. Zhang, C. Chen, Y. Tang, Z. Cheng, CO2 reduction in a microchannel electrochemical reactor with gas-liquid segmented flow. Chemical Engineering Journal 392, 124798 (2020).

[0079] 4. S. Garg, M. Li, A. Z. Weber, L. Ge, L. Li, V. Rudolph, G. Wang, T. E.Ruff ord, Advances and challenges in electrochemical CO 2 reduction processes: an engineering and design perspective looking beyond new catalyst materials. J. Mater. Chem. A 8, 1511-1544 (2020).

[0080] 5. M. Rahaman, A. Dutta, A. Zanetti, P. Broekmann, Electrochemical Reduction of CO2 into Multicarbon Alcohols on Activated Cu Mesh Catalysts: An Identical Location (IL) Study. ACSCatal. 7, 7946-7956 (2017).

[0081] 6. X. Lu, C. Zhao, Electrodeposition of hierarchically structured three- dimensional nickel-iron electrodes for efficient oxygen evolution at high current densities. Nat Commun 6, 6616 (2015).

[0082] 7. US Patent No. 8,283,062 B2INCORPORATION BY REFERENCE; EQUIVALENTS

[0083] The teachings of all patents, published applications and references cited herein (including those patents, published applications and references cited in the attached documents filed herewith) are incorporated by reference in their entirety.

[0084] While example embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the embodiments encompassed or contemplated herein.- 19 -4188550. vl

Claims

CLAIMSWhat is claimed is:

1. A method for capturing carbon dioxide (CO2), the method comprising: a) alternating flow of a gas and a liquid catholyte through a copper-coated channel of a cathode plate, wherein the gas has a CO2 concentration less than about 350,000 parts per million (ppm); b) flowing a liquid anolyte through a channel of an anode plate that interfaces with the cathode plate via an anode and an ion exchange membrane; c) applying a voltage across the anode and the cathode plate, thereby forming a reduced CO2 product.

2. The method of claim 1, wherein the catholyte comprises potassium hydroxide (KOH), potassium chloride (KC1), potassium bromide (KBr), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), sodium hydroxide (NaOH), sodium chloride (NaCl), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCOi), calcium hydroxide (Ca(OH)2), calcium chloride (CaCh), calcium carbonate (CaCOs), calcium bicarbonate (Ca(HCO3)2), barium chloride (BaCh), cesium hydroxide (CsOH), cesium carbonate (CS2CO3), cesium bicarbonate (CsHCOs), polyethylene glycol dimethyl ether, methanol, polyethylene glycol methyl isopropyl ether, propylene carbonate, N-methyl-2-pyrrolidone, tributyl phosphate, methylcyanoacetate, glycerol, tetrahydrotiphene dioxide, or butanol.

3. The method of claim 1, wherein the anolyte comprises potassium hydroxide (KOH), potassium chloride (KC1), potassium bromide (KBr), potassium carbonate (K2CO3), potassium bicarbonate (KHCO3), sodium hydroxide (NaOH), sodium chloride (NaCl), sodium carbonate (Na2COs), sodium bicarbonate (NaHCOi), calcium hydroxide (Ca(OH)2), calcium chloride (CaCh), calcium carbonate (CaCOs), calcium bicarbonate (Ca(HCO3)2), barium chloride (BaCh), cesium hydroxide (CsOH), cesium carbonate (CS2CO3), cesium bicarbonate (CsHCOs), polyethylene glycol dimethyl ether, methanol, polyethylene glycol methyl isopropyl ether, propylene carbonate, N-methyl-2-pyrrolidone, tributyl phosphate, methylcyanoacetate, glycerol, tetrahydrotiphene dioxide, or butanol.- 20 -4188550. vl4. The method of claim 1, wherein the applied voltage is about -4V to about 3 V.

5. The method of claim 1, wherein flowing the gas is at a residence time from about 0.002s to about 0.2s6. The method of claim 1, wherein flowing the liquid catholyte is at a residence time from about 0.001s to about 0.1s7. The method of claim 1, wherein flowing the liquid anolyte is at a residence time from about 0.000002s to about 0.2s8. The method of claim 1, wherein applying the voltage generates a current density of at least 100 mA / cm2.

9. The method of claim 1, wherein a peristaltic pump generates flow for an anolyte.

10. The method of any one of claims 1-9, wherein the reduced CO2 product is one or more of methanol, ethanol, propanol, isopropanol, methane, formic acid, ethylene, and propylene.

11. The method of claim 10, wherein the copper-coated channel of the cathode plate or the channel of the anode plate has a serpentine arrangement.

12. The method of claim 10, wherein the copper-coated channel of the cathode plate comprises electrodeposited or electroplated copper.

13. The method of claim 10, wherein the anode comprises platinum, titanium, nickel, iron, nickel -iron foam, copper or stainless steel.

14. The method of claim 10, wherein the gas has a concentration of CO2 of about 400 ppm to about 300,000 ppm.

15. The method of claim 10, wherein the liquid comprising the catholyte or anolyte further comprises titanium dioxide (TiCh) nanoparticles.

16. The method of claim 10, wherein the copper-coated channel of the cathode plate is further coated with TiCh nanoparticles.- 21 -4188550. vl17. The method of claim 10, wherein the copper-coated channel of the cathode plate or the channel of the anode plate has a cross-sectional area from about 16 mm2to about 81 mm2.

18. The method of claim 10, further comprising collecting the liquid catholyte comprising the reduced CO2 product.

19. The method of claim 18, further comprising distilling the liquid catholyte comprising the reduced CO2 product and collecting the reduced CO2 product.

20. The method of claim 10, wherein the reduced CO2 product is ethanol.

21. The method of claim 10, wherein the ion exchange membrane is a proton exchange membrane or a bipolar membrane.

22. A method of making an electrochemical reactor, the method comprising: a) adhering a lower surface of a cathode plate comprising a channel therein to an upper surface of at least one gasket comprising a window; b) adhering a lower surface of the at least one gasket to an upper surface of a windowless gasket, wherein the windowless gasket comprises copper adhered to at least a portion of its upper surface; c) adhering a lower surface of the windowless gasket to an upper surface of a support; d) flowing a liquid catholyte comprising copper ions through the channel of the cathode plate; and e) applying a voltage across the cathode plate and the copper, thereby electroplating copper onto the channel of the cathode plate.

23. The method of claim 22, wherein the catholyte comprises copper (II) sulfate.

24. The method of claim 22, wherein flowing the liquid catholyte has a residence time of about 0.000002s to about 0.002s.

25. The method of claim 22, wherein the applied voltage across the cathode plate and copper is from about 1 V to about 3 V for about 2 minutes to about 40 minutes.- 22 -4188550. vl26. The method of claim 22, wherein the channel of the cathode plate has a serpentine arrangement.

27. The method of claim 22, wherein the channel of the cathode plate or the channel of the anode plate has a cross-sectional area from about 16 mm2to about 81 mm2.- 23 -4188550. vl

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