Systems and methods for continuous direct air capture and electrochemical conversion of carbon dioxide and water in a solid electrolyte reactor

Abstract

A practical and scalable solid electrolyte electrochemical cell that can directly uptake CO2 and H2O from air and continuously convert them into basic petrochemical ethylene and oxygen with low voltage potential and current is provided. The DAC solid electrolyte reactor can produce approximately 70 mg of ethylene in 1 h, with about 80% energy efficiency, and remain in a lower temperature.

Description

SYSTEMS AND METHODS FOR CONTINUOUS DIRECT AIR CAPTURE AND ELECTROCHEMICAL CONVERSION OF CARBON DIOXIDE AND WATER IN A SOLID ELECTROLYTE REACTORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The current application claims the benefit of and priority under 35 U.S.C. § 119 (e) to U.S. Provisional Patent Application No. 63 / 649,263 entitled “Continuous Direct Air Capture and Electrochemical Conversion of CO2 and H2O into Ethylene and Oxygen in a Solid Electrolyte Reactor” filed May 17, 2024. The disclosure of U.S. Provisional Patent Application No. 63 / 649,263 is hereby incorporated by reference in its entirety for all purposes.FIELD OF THE INVENTION

[0002] The present invention generally relates to direct air capture (DAC) and conversion of carbon dioxide into valuable chemicals, and more particularly to a practical and scalable solid electrolyte electrochemical cell that can directly uptake CO2 and H2O from air and continuously convert them into basic petrochemical ethylene and oxygen with voltage potential of 0.6 V and 1 A current.BACKGROUND

[0003] The end use of carbon-based chemical products results in widespread carbon dioxide (CO2) emissions into the atmosphere, which are challenging to limit in comparison to point sources, such as power plants. For this reason, an effective approach to limiting the carbon footprint of the chemical industry sector is to develop carbon-neutral or -negative methods of producing commodity chemicals.SUMMARY OF THE INVENTION

[0004] Various embodiments of the disclosure are directed to methods and devices for direct air capture (DAC) and conversion of CO2 into valuable chemicals, and more particularly to a practical and scalable solid electrolyte electrochemical cell that can directly uptake CO2 and H2O from air and continuously convert them into basicpetrochemical ethylene and oxygen with voltage potential of about 0.6 V and about 1 A current. Many embodiments of the methods and devices are directed to DAC solid electrolyte reactors that can produce about 70 mg of ethylene in about 1 h, with about 80% energy efficiency, and remain in a lower temperature.

[0005] Some embodiments include a reactor for direct air capture and electrochemical conversion of carbon dioxide comprising: a cathode comprising a carbon foam, wherein the carbon foam comprises: a plurality of carbon nanotubes; a copper-based catalyst configured to catalyze a carbon dioxide reduction reaction at the cathode to produce ethylene; a carbon dioxide sorbent material configured to absorb gaseous carbon dioxide; and a water sorbent material configured to absorb water; an anode comprising a nickel foam filled with PEO / KOH configured to facilitate an oxygen evolving reaction; and a solid- state electrolyte disposed between the cathode and the anode, wherein the solid-state electrolyte comprises a polymer matrix comprising PEO / KOH.

[0006] In some embodiments, the plurality of carbon nanotubes comprises single wall carbon nanotubes.

[0007] In some embodiments, the copper-based catalyst comprises copper nanoparticles, copper oxide, or a combination thereof.

[0008] In some embodiments, the carbon dioxide sorbent material comprises polyethylenimine and zeolite 13X.

[0009] In some embodiments, the water sorbent material comprises calcium chloride.

[0010] In some embodiments, the solid-state electrolyte comprises polypropylene film filled with a PEO / KOH paste.

[0011] In some embodiments, the cathode further comprises sodium alginate crosslinked with calcium ions to form a porous structure encapsulating the sorbent materials.

[0012] In some embodiments, the plurality of carbon nanotubes supports the copperbased catalyst, the carbon dioxide sorbent material, and the water sorbent material.

[0013] In some embodiments, the carbon dioxide reduction reaction to produce ethylene consumes 8 electrons and 8 protons per ethylene molecule.

[0014] In some embodiments, the oxygen evolving reaction at the anode generates a plurality of OH wherein the plurality of OH- is configured to transport through the solid- state electrolyte to the cathode.

[0015] In some embodiments, the gaseous carbon dioxide and water are in the air.

[0016] In some embodiments, a bias of less than or equal to 0.6 V is applied to produce ethylene and oxygen.

[0017] In some embodiments, the reactor produces at least 70 mg of ethylene per hour at or below 25 °C.

[0018] Some embodiments include a method for direct air capture and electrochemical conversion of carbon dioxide, comprising: absorbing carbon dioxide and water from air using a cathode comprising a carbon foam, wherein the carbon foam comprises a plurality of carbon nanotubes, a copper-based catalyst, a carbon dioxide sorbent material, and a water sorbent material; applying an electrical bias across the cathode and a nickel foam anode, wherein the cathode reduces carbon dioxide to ethylene and the anode evolves oxygen; and capturing the ethylene produced at the cathode.

[0019] In some embodiments, the ethylene is selectively trapped using an ionic liquid.

[0020] In some embodiments, the electrical bias applied is 0.6 and the current is 1 A.

[0021] In some embodiments, the reactor operates at or below 25 °C.

[0022] In some embodiments, the copper-based catalyst is formed by thermal decomposition of copper formate on the plurality of carbon nanotubes.

[0023] In some embodiments, the plurality of carbon nanotubes comprises single wall carbon nanotubes.

[0024] In some embodiments, the copper-based catalyst comprises copper nanoparticles or copper oxide; wherein the carbon dioxide sorbent material comprises polyethylenimine and zeolite 13X; wherein the water sorbent material comprises calcium chloride; wherein the nickel foam is filled with PEO / KOH; wherein the plurality of carbon nanotubes supports the copper-based catalyst, the carbon dioxide sorbent material, and the water sorbent material.

[0025] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination ofthe specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The description and claims will be more fully understood with reference to the following figures and data graphs, which are presented as exemplary embodiments of the invention and should not be construed as a complete recitation of the scope of the invention.

[0027] FIG. 1 provides a schematic diagram of catalytic electrochemical reduction mechanism of direct air captured CO2 and H2O into ethylene and O2 in accordance with various embodiments.

[0028] FIG. 2 provides a schematic diagram of catalytic electrochemical reduction mechanism of direct air captured CO2 and H2O into ethylene and O2 in accordance with various embodiments.

[0029] FIG. 3 provides a schematic diagram of a solid electrolyte reactor for direct air capture of CO2 and H2O in accordance with various embodiments.

[0030] FIG. 4 provides photographic images of the polypropylene film and the PEO / KOH-filled polypropylene film and photographic images of the nickel foam and the PEO / KOH-coated nickel foam (bottom) in accordance with various embodiments.

[0031] FIG. 5 provides a flow-chart for fabricating a conductive carbon cathode for CO2 and H2O direct air capture in accordance with various embodiments.

[0032] FIG. 6 provides a photographic picture of carbon foam and illustration of zeolite 13X / PEI800 and SWCNTs with copper nanoparticles embedded in the ionotropic gelation of sodium alginate and calcium chloride in accordance with various embodiments.

[0033] FIG. 7 provides photographic images of the assembled solid polyelectrolyte E-cell in accordance with various embodiments.

[0034] FIG. 8 provides a photographic picture of the F950 three gas analyzer for in situ measuring ethylene and O2 open to air and the detected ethylene and oxygen in the open environment in accordance with various embodiments.DETAILED DESCRIPTION

[0035] Various embodiments provide scalable solid electrolyte electrochemical cells that can directly uptake CO2 and H2O from air and continuously convert them into basic petrochemical ethylene and oxygen with low voltage potential and current. Embodiments of such a DAC solid electrolyte reactor can produce about 70 mg of ethylene in about 1 h, with about 80% energy efficiency, and remain at a lower temperature.

[0036] Direct CO2 conversion into chemical products is a promising avenue through biological, thermochemical, photochemical, and electrochemical ways to lower carbon emission. Electrochemical conversion of CO2 using the electricity produced from renewable energy sources into chemical products is a carbon-neutral or carbon-negative means to penetrate renewables into chemical products with a more controllable and scalable version. The lab-scale electrochemical reduction of CO2 is into syngas, carbon monoxide, formic acid, methane, methanol, ethylene, ethanol, and n-propanol.

[0037] Of these major CO2 reduction products, ethylene is the basic feedstock of modern fuel and chemical products. Global production capacity for ethylene may grow from 180 million Mt in 2017 to 270 million Mt in 2026. Ethane cracking may generate 1 -1.2 Mt of CO2 / Mt of ethylene produced, while naphtha cracking may generate 1.8-2 Mt of CO2 / Mt of ethylene in current industrial manufacturing.

[0038] With electrochemical reduction of CO2, 3.1 Mt of CO2 will be consumed per Mt of ethylene produced using renewable electricity. This will save 4.14-5.14 Mt of CO2 emission in total. Current lab-scale electrochemical reduction of CO2 would generate additional carbon emissions because using commercial CO2 requires capture, storage, and transportation of CO2. It may be hard to claim carbon-neutral or -negative electrochemical production.

[0039] Various embodiments according to this disclosure provide a solid-state electrolyte reactor for direct air capture of CO2 and H2O using CO2 sorbent materialspolyethylenimine (PEI) 800 / zeolite 13X and gyroscopic salt calcium chloride (CaCl2) and to electrochemically convert them into ethylene and O2 on copper- or copper-oxide- covered single-walled carbon nanotubes (SWCNTs) and a poly-(ethylene oxide) (molecular weight of about 4000) (PEO) / KOH-filled nickel anode, respectively. The solid- state polyelectrolyte reactor continuously functions with about 80% energy efficiency, and the device temperature remains less than about 25 °C.

[0040] The working principle according to some embodiments, is as follows: PEI / zeolite 13X absorbs CO2, and hygroscopic calcium chloride absorbs H2O. Adsorbed CO2 can accept one electron from directly contacted SWCNTs and one proton from H2O to form HCOO. HCOO continuously accepts one electron from SWCNTs and decomposes into CO and HO". This is demonstrated by producing CO without a copper catalyst. On the nanoscale copper surface, CO-CO coupling occurs to form ethylene by taking eight electrons and eight protons.

[0041] FIG. 1 provides a schematic diagram of catalytic electrochemical reduction mechanism of direct air captured CO2 and H2O into ethylene and O2 in accordance with various embodiments. PEI / zeolite 13X 101 can be incorporated into the cathode 102 of the solid-state electrolyte reactor. The cathode 102 can be copper- or copper-oxide- covered SWCNTs. The cathode 102 can also incorporate CaCl2 (not shown). PEI / zeolite 13X can absorb CO2 and CaCl2 can absorb H2O. The absorbed CO2 can accept one electron (e-) from SWCNTs on the cathode 102 and one proton (H+) from H2O to form a formate ion HCOO' 103. HCOO' can continue the process by accepting one e- from SWCNTs to form CO 104 and HO". CO-CO coupling 105 can occur on the cathode 102 to form ethylene 106 by taking 8 e- and 8 H+.

[0042] FIG. 2 provides a schematic diagram of catalytic electrochemical reduction mechanism of direct air captured CO2 and H2O into ethylene and O2 in accordance with various embodiments. Cathode 201 including copper or copper oxide covered SWCNTs, PEI / zeolite 13X, and CaCl2. The cathode 201 absorbs CO2 202 and H2O. The absorbed CO2 accepts one e~ from the cathode 201 and one H+from H2O until it forms formic acid 203. Copper or copper oxide on the cathode can catalyze CO dimerization 204 and assist with product promotion. Dimerized CO 205 can continue to accept e~ from cathode and H+from H2O to form ethylene 206.

[0043] In various embodiments, the electrolyte layer can be a PEO / KOH-filled polypropylene (PP) sheet. Porous PP can be filled with paste. Some embodiments utilize PP with 0.2 pm pore size filled with PEO / KOH (1 :0.18 weight ratio) paste. The solid polyelectrolyte provides the path channels for OH" migration from the conductive cathode to the nickel anode under an electric field and generates water from the nickel anode to the conductive cathode.

[0044] FIG. 3 provides a schematic diagram of the solid-state electrolyte reactor in accordance with various embodiments. The solid-state electrolyte reactor 300 includes a cathode 301 , a solid-state electrolyte layer 302, and an anode 303. The cathode 301 can include copper or copper oxide covered SWCNTs, PEI / zeolite 13X, and CaCl2. CO2 reduction reactions can occur on the cathode 301. Ethylene can be generated at the cathode. The anode 303 can be PEO / KOH-filled nickel. Oxygen evolving reactions can occur on the anode 303. The solid-state electrolyte 302 can be PEO / KOH-filled polypropylene (PP) sheet. The solid PP provides the path channels for OH" migration from the cathode 301 to the anode 303 under an electric field. The OH" can form water at the anode 303 and the generated water can transport through the electrolyte 302 to the conductive cathode 301. FIG. 3 shows the reactor for direct air capture of CO2 and H2O, electroreduction of CO2 into ethylene in the cathode, the oxygen evolving reaction in the anode, and the transportation of OH" and H2O in the solid electrolyte reactor in accordance with various embodiments.

[0045] In various embodiments, the anode can be PEO / KOH-filled nickel foam (110 PPI, pore size of 0.25 mm). Solid KOH might limit the corrosive damage to the nickel foam. OH" can be oxidized into oxygen and H2O. Oxidized oxygen forms bulbs in the PEO / KOH-filled nickel foam surface. H2O is attracted back to the cathode by gyroscopic salt CaCl2. Consumed OH" is supplied by migration of OH" from cathodes through solid polyelectrolytes.

[0046] FIG. 4 provides photographic images of the PP film (the inset is the crosssection SEM image of the PP film showing a 0.2 pm pore size) and the PEO / KOH-filled PP film (the inset is the PEO / KOH paste) (top) and photographic images of the nickel foam (the inset is the SEM image of the nickel foam) and the PEO / KOH -coated nickel foam (bottom) in accordance with various embodiments.

[0047] In various embodiments, the cathode is highly conductive carbon foam (1 g, 100 PPI pore size, 3% relative density, 0.125 x 4 x 4 inch) filled with 2 g of high- pressure carbon monoxide conversion (HiPCO) SWCNTs for facilitating the electron reduction reaction coated with copper nanoparticles (2.5 g) as the catalyst for ethylene formation formed through thermal decomposition of copper formate. The aqueous solution of copper formate (125 g / L) is soaked onto carbon nanotubes. After water is evaporated, blue copper formate covers the carbon nanotubes. The conductive carbon electrode is baked at 90 °C to decompose copper formate into copper and copper oxide (dark brown color). On carbon foam filled with SWCNTs with copper nanoparticles, zeolite 13X / PEI800 / sodium alginate mixture is filled inside. The ionotropic gelation of a sodium alginic acid solution with Ca2+can occur by adding CaCl2 aqueous solution, a hygroscopic salt to form polymer beads with the porous structure as the scaffold of CO2 sorbent material zeolite 13X / PEI800, and SWCNTs with copper nanoparticles occur inside pores of carbon foams. The CO2 sorbent material PEI / zeolite 13X which has about 26 wt % adsorption of CO2 and H2O is filled in the carbon cathode. Zeolite 13X has been utilized in aerospace vehicles and space stations for CO2 absorption. Sodium alginate can be added as the organic binder when coordinated with hygroscopic calcium chloride, which can assist water capture in an arid environment.

[0048] FIG. 5 provides a flow-chart for fabricating a highly conductive carbon cathode containing CO2 and H2O direct air capture and electrochemical reduction catalyst carbon nanotubes and copper or copper oxide. The steps include coating HiPCO SWCNTs onto carbon foam; coating copper formate onto carbon foam; decomposing copper formate into copper and copper oxide; adding CO2 sorbent material PEI800 / zeolite 13X / sodium alginate; and adding CaCl2 to cross-link alginate as a H2O sorbent.

[0049] FIG. 6 provides a photographic picture of carbon foam (left) and cartoon illustration of zeolite 13X / PEI800 and SWCNTs with copper nanoparticles embedded in the ionotropic gelation of sodium alginate and calcium chloride (right) in accordance with various embodiments. Oxidized oxygen forms bulbs in the PEO / KOH-filled nickel foam surface.

[0050] The direct air capture (DAC) cathode, solid PEO / KOH PP electrolyte layer, and PEO / KOH-filled nickel foam can be assembled to form the electrochemical cell (E- cell). FIG. 7 provides photographic images of the assembled solid polyelectrolyte E-cell (top) and the functional DAC E-cell supplied with 0.6 V and 1A DC with the remaining temperature at 25 °C (bottom) (the inset shows the O2 bubbles from the working DAC E- cell) in accordance with various embodiments. Copper wires can be inserted inside the DAC cathode for efficient charge supply. The DAC cathode is connected to a negative direct current (DC) supplier, and the nickel electrode is connected to a positive DC supplier. To activate the E-cell, 10-15 V DC needs to be applied shortly. The initial high electric field is needed to trigger the ion motion in the solid electrolyte reactor. Once the E-cell starts, the potential automatically drops to 0.4-0.6 V (much less than the minimum potential difference of 1.23 V for H2O hydrolysis) with a current up to 1 A. The oxygen bubbles can be observed on the PEO / KOH-filled nickel foam. The E-cell can continuously run for 24 h and 7 days a week and remain at a temperature around or below 25 °C. The E-cells can be further optimized by using different materials and / or structures. Without copper nanoparticles, the electroreduction of captured CO2 and H2O mainly produces CO and oxygen. With copper nanoparticles, the electroreduction of captured CO2 and H2O can produce ethylene and oxygen.

[0051] FIG. 8 provides a photographic picture of the F950 three gas analyzer for in situ measuring ethylene and O2 open to air (left) and the plot of the ethylene concentration in parts per million and O2 in percentage against the running time, respectively, obtained from the F950 three gas analyzer (right) in accordance with various embodiments. Detected ethylene is up to 200 ppm, and the oxygen concentration is up to 30% in air.

[0052] In various embodiments, produced ethylene is trapped with ionic liquid 1 - ethyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide. The rest of the gas is released into the air. Trapped ethylene is about 70 mg after 1 h of reaction. It requires 12 electrons to convert 2 CO2 moieties into 1 ethylene molecule (FIGs. 1 and 2). Therefore, 1 kg of ethylene will need (1000 / 28) x 6.02 x 1023 x 12 electrons. If one assumes that the electrochemical reduction of CO2 and H2O will be supplied with 0.6 V DC, then 1 kWh can provide 1000 x 3600 x 6.24 x 1018 / 0.6 electrons. Theoretically, 87 mg of ethylene can be produced with 0.6 DC power supply at 1 A for 1 h. This is equivalent to 80%electro-reduction efficiency. This demonstrates that the solid electrolyte reactor is more efficient than the liquid electrochemical cells. The liquid electrochemical cells have about 34% full-cell energy efficiency at an applied voltage of 2.4 and an average current density of 110 mA / cm2using copper as a catalyst.

[0053] Various embodiments of the disclosure provide a solid electrolyte reactor comprising of a highly conductive cathode capable of direct air capture of CO2 and H2O, a PEO / KOH -filled PP polyelectrolyte, and a PEO / KOH-filled nickel anode continuously functioning to produce ethylene and O2 with 80% energy efficiency. Direct air capture of CO2 and H2O uses CO2 sorbent material PEI / zeolite 13X composites and hygroscopic salt CaCl2 embedded in conductive carbon foams. The incorporated highly conductive SWCNTs act as support for CO2 and H2O sorbent materials, electron conductors, and simultaneously effective cathodes for electron injection to PEI-bound CO2 to reduce to CO. The co-existence of PEI with carbon nanotubes can help in stabilizing reduced CO2 and concentrating CO2 on the catalyst for electrochemical reduction. Copper and copper oxide on the surface of carbon nanotubes decomposed from copper formate perform as catalysts for the coupling of in situ produced CO-CO to yield ethylene and OH" by consuming eight electrons and eight protons. Formed OH" migrated into the PEO / KOH- filled nickel anode through the PEO / KOH-filled PP polyelectrolyte under an electric field and oxidized to H2O and O2.EXEMPLARY EMBODIMENTS

[0054] The following are provided as exemplary of the methods and processes that may be used to implement various embodiments of the disclosure and are not intended to describe the full breadth of the disclosure.Materials And Methods:

[0055] Materials: 1 -Ethyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide (EM IM TFSI), copper formate tetrahydrate 98%, polyethylene glycol) M.W. 4000, potassium hydroxide 99.98%, poly(ethylene imide) branched M. W. 800, sodium alginate, porous nickel foam (300 mm L x 200 mm W x 1.6 mm T), Duocel Reticulated VitreousCarbon Foam 0.125" x 4"x4" 100 PPI 3% relative density, UOP Molsiv Adsorbent 13X, HiPCO single-walled carbon nanotubes are used.

[0056] Experimental: PEO / KOH (1 / 0.18 weight ratio) paste was formed in deionized water. The PEO / KOH paste was filled on polypropene film to form solid electrolyte. PEO / KOH paste was filled in nickel foam to form anode. Carbon nanotube slurry (paste) was formulated by mixing 1 g HiPCO single-walled carbon nanotubes in 100 g de-ionized water. HiPCO SWCNTs (2 g) was filled in the highly conductive carbon foam (1 g, 100 PPI pore size, 3% relative density, 0.125 inch x 4 inch x 4 inch). The copper formate solution (125 g / L) was prepared by dissolving copper formate in deionized water. The aqueous solution of copper formate was soaked onto HiPCO SWCNTs filled carbon foams. After water evaporated, the blue copper formate S-1 covered on carbon nanotubes. The conductive carbon electrode was baked at 90 °C to decompose copper formate into copper and copper oxide (dark brown color). About 2.5 g copper nanoparticles or copper oxide were formed inside the HiPCO SWCNTs filled carbon foam. Zeolite 13X / (60weight%) PEI800 was mixed and further formulated with sodium alginate (20 weight%). The Zeolite 13X / PEI800 / Sodium Alginate was pasted onto carbon foam filled with HiPCO SWCNTs and copper nanoparticles. The 10 g CaCl2 was dissolved in de-ionized water and was soaked onto carbon foam filled with HiPCO SWCNTs and copper nanoparticles and zeolite 13X / PEI800 / Sodium Alginate. The ionotropic gelation of a sodium alginic acid solution with Ca2+by adding CaCI? aqueous solution, a hygroscopic salt to form polymer beads with porous structure as scaffold of CO2 sorbent materials zeolite 13X / PEI800 and SWCNTs with copper nanoparticles, occurs inside pores of carbon foams. PEO / KOH filled nickel foam and the carbon cathode sandwich the PEO / KOH filled PP solid electrolyte to form the solid electrolyte reactor. The assembled solid electrolyte reactor was powered with a DC power supply. F-950 Three gas analyzer was used to detect ethylene, oxygen and carbon dioxide. Carbon monoxide meter was used to detect CO. The temperature of solid electrolyte reactor was monitored with infrared thermometers.DOCTRINE OF EQUIVALENTS

[0057] This description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use. The scope of the invention is defined by the following claims.

[0058] As used herein, the singular terms “a,” “an,” and “the” may include plural referents unless the context clearly dictates otherwise. Reference to an object in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”

[0059] In this disclosure, the words “including,” “such as,” “e.g.,” and related terms are not closed-ended and should be interpreted as having the explanatory language “but not limited to.” Likewise, the term “include” is not closed-ended and should be interpreted such that what proceeds is not limiting on the term that precedes.

[0060] As used herein, the terms “approximately” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. When used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ± 10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1 %, less than or equal to ±0.5%, less than or equal to ±0.1 %, or less than or equal to ±0.05%.

[0061] Additionally, amounts, ratios, and other numerical values may sometimes be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-rangeis explicitly specified. For example, a ratio in the range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, but also to include individual ratios such as about 2, about 3, and about 4, and sub-ranges such as about 10 to about 50, about 20 to about 100, and so forth.

Claims

WHAT IS CLAIMED IS:1 . A reactor for direct air capture and electrochemical conversion of carbon dioxide comprising: a cathode comprising a carbon foam, wherein the carbon foam comprises: a plurality of carbon nanotubes; a copper-based catalyst configured to catalyze a carbon dioxide reduction reaction at the cathode to produce ethylene; a carbon dioxide sorbent material configured to absorb gaseous carbon dioxide; and a water sorbent material configured to absorb water; an anode comprising a nickel foam filled with PEO / KOH configured to facilitate an oxygen evolving reaction; and a solid-state electrolyte disposed between the cathode and the anode, wherein the solid-state electrolyte comprises a polymer matrix comprising PEO / KOH.

2. The reactor of claim 1 , wherein the plurality of carbon nanotubes comprises single wall carbon nanotubes.

3. The reactor of claim 1 , wherein the copper-based catalyst comprises copper nanoparticles, copper oxide, or a combination thereof.

4. The reactor of claim 1 , wherein the carbon dioxide sorbent material comprises polyethylenimine and zeolite 13X.

5. The reactor of claim 1 , wherein the water sorbent material comprises calcium chloride.

6. The reactor of claim 1 , wherein the solid-state electrolyte comprises polypropylene film filled with a PEO / KOH paste.

7. The reactor of claim 1 , wherein the cathode further comprises sodium alginate crosslinked with calcium ions to form a porous structure encapsulating the sorbent materials.

8. The reactor of claim 1 , wherein the plurality of carbon nanotubes supports the copper-based catalyst, the carbon dioxide sorbent material, and the water sorbent material.

9. The reactor of claim 1 , wherein the carbon dioxide reduction reaction to produce ethylene consumes 8 electrons and 8 protons per ethylene molecule.

10. The reactor of claim 1 , wherein the oxygen evolving reaction at the anode generates a plurality of OH', wherein the plurality of OH' is configured to transport through the solid-state electrolyte to the cathode.11 . The reactor of claim 1 , wherein the gaseous carbon dioxide and water are in the air.

12. The reactor of claim 1 , wherein a bias of less than or equal to 0.6 V is applied to produce ethylene and oxygen.

13. The reactor of claim 1 , wherein the reactor produces at least 70 mg of ethylene per hour at or below 25 °C.

14. A method for direct air capture and electrochemical conversion of carbon dioxide, comprising: absorbing carbon dioxide and water from air using a cathode comprising a carbon foam, wherein the carbon foam comprises a plurality of carbon nanotubes, a copper-based catalyst, a carbon dioxide sorbent material, and a water sorbent material;applying an electrical bias across the cathode and a nickel foam anode, wherein the cathode reduces carbon dioxide to ethylene and the anode evolves oxygen; and capturing the ethylene produced at the cathode.

15. The method of claim 14, wherein the ethylene is selectively trapped using an ionic liquid.

16. The method of claim 14, wherein the electrical bias applied is 0.6 V and the current is 1 A.

17. The method of claim 14, wherein the reactor operates at or below 25 °C.

18. The method of claim 14, wherein the copper-based catalyst is formed by thermal decomposition of copper formate on the plurality of carbon nanotubes.

19. The method of claim 14, wherein the plurality of carbon nanotubes comprises single wall carbon nanotubes.

20. The method of claim 14, wherein the copper-based catalyst comprises copper nanoparticles or copper oxide; wherein the carbon dioxide sorbent material comprises polyethylenimine and zeolite 13X; wherein the water sorbent material comprises calcium chloride; wherein the nickel foam is filled with PEO / KOH; wherein the plurality of carbon nanotubes supports the copper-based catalyst, the carbon dioxide sorbent material, and the water sorbent material.

Images