WO2025136759A1 - Electrochemical capture and release of co2 using inorganic sorbent materials - Google Patents

Abstract

An electrochemical method and associated system for adsorption and desorption of CO2. The system comprises a porous inorganic oxide electrode and a non-aqueous solution comprising a dissolved electrolyte. The method comprises contacting the electrode with a gaseous input comprising CO2 wherein the CO2 saturates the electrolyte, and applying a negative voltage wherein the CO2 is adsorbed to the electrode. Once saturated, desorption of the CO2 from the inorganic oxide electrode is achieved by applying a positive voltage.

Description

ELECTROCHEMICAL CAPTURE AND RELEASE OF CO₂ USING INORGANIC

SORBENT MATERIALS

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is hereby claimed to U.S. provisional application Ser. No. 63/611,459, filed December 18, 2023, which is incorporated herein by reference.

BACKGROUND

Worldwide energy consumption is estimated to increase to 850 QBtu by 2050. (Raimi, D. et al., Global energy outlook 2022: Turning points and tension in the energy transition. Resources for the Future: Washington, DC, USA 2022.) Fossil fuels are projected to remain the dominant source of energy' and are predicted to cause more than 50 Gigatons of CO2 emissions per year. (Id.) To limit the impact of CO2 on global climate patterns, the development of efficient methods to capture and convert CO2 to useful chemicals is of paramount importance. At the heart of this challenge is the effective adsorption of CO2 to surfaces. See, for example, Alsarhan, L. M. et al., Circular carbon economy (CCE): A way to invest CO2 and protect the environment, a review. Sustainability 2021, 13 (21), 11625.

Current technology for CO2 capture uses nucleophilic sorbent materials that can selectively bind to CO2 molecules from dilute streams. Upon reaction of CO2 with inorganic materials such as calcium hydroxide and organic materials such as amines and supported amines, temperature or pressure is applied to transfer the CO2 to reservoirs of higher CO2 concentration, while the sorbent material is regenerated and reused for further CO2 absorption in subsequent capture cycles.

An example of this technology uses alkaline carbonates to remove CO2. In this system, K2CO3 reacts with water and CO2 to form KHCO3. See Smith, K. et al., Demonstration of a concentrated potassium carbonate process for CO2 capture. Energy & fuels 2014, 28 (1), 299- 306. The shortcoming of this approach is the high thermal energy’ required for regeneration (130 to 220 kJ mol'¹) and the slow absorption kinetics. (Hu, G. et al., Carbon dioxide absorption into promoted potassium carbonate solutions: A review. International Journal of Greenhouse Gas Control 2016, 53, 28-40.) Temperature swing approaches are commonly applied to capture CO2 via amines such as alkanolamines and alkanamines. Carbamate and protonated amine pairs or bicarbonates are formed after the CO2 absorption process, followed by regeneration through application of both heat and vacuum. Typically, the thermal energies required for regeneration are around 100 to 180 kJ mol'¹, but inefficiencies in the plant design decrease the efficiency by 20 to 25 %. Unfortunately, the amines are prone to decomposition under typical operating temperatures as well as forming carcinogenic products when reacting with contaminants in the CO2 gas streams, such as NO_X and SO_X. See Chen et al., Emerging N-nitrosamines and N- nitramines from amine-based post-combustion CO2 capture-a review. Chemical Engineering Journal 2018, 335, 921-935.

Current progress in designing electrochemical CO2 capture methods has involved the use of redox active quinones as carriers for CO2. The current systems, however, are not stable in the presence of O2, resulting in the formation of superoxide that destructively reacts with the electrolyte, solvent, and quinones. See Jeziorek, D. et al., Theoretical and electrochemical study of the mechanism of anthraquinone-mediated one-electron reduction of oxygen: the involvement of adducts of dioxygen species to anthraquinones. Journal of the Chemical Society, Perkin Transactions 2 1997, (2), 229-236. For example, when using 2,3,5,6-tetrachloro-p-benzoquinone for electrochemical CO2 capture under a mix of 87: 10:3 of CCh Ch, quinones only survived a single adsorption-release cycle. (Barlow, J. M. et al., Oxygen-stable electrochemical CO2 capture and concentration with quinones using alcohol additives. Journal of the American Chemical Society 2022, 144 (31), 14161-141 9.) Poly(l,4-anthraquinone) supported on carbon was more energy efficient (40 to 90 kJ mol'¹) and lost about 30 % capacity after 7000 adsorption/desorption cycles under anaerobic conditions. (Voskian, S. et al., Faradaic electroswing reactive adsorption for CO2 capture. Energy & Environmental Science 2019, 12 (12), 3530-3547.) Typically, the use of organics in electrochemical CCh-capturing processes, such as electrochemically mediated amine regeneration and proton-coupled electron transfer-mediated CO2 capture involves expensive membranes. (Renfrew, S. E. et al., Electrochemical approaches toward CO2 capture and concentration. ACS Catalysis 2020, 10 (21), 13058-13074.) Thus, there remains a long-felt and unmet need to develop economical CO2 capture systems that address both the efficiency and stability challenges.

SUMMARY

Disclosed herein is an electrochemical method and associated system / apparatus for the adsorption/desorption of CO2. The system includes a porous inorganic oxide electrode (e.g., T1O2) disposed in a non-aqueous solution comprising a dissolved electrolyte (e g, tetrabutylammonium hexafluorophosphate (TBAPFe)). In operation, a gaseous input comprising CO2 is introduced whereupon it saturates the electrolyte with CO2. A negative voltage is applied to the electrode to generate nucleophilic sites on the surface of the inorganic oxide electrode which subsequently adsorbs the CO2 from the electrolyte solution. Once the electrode is saturated with CO2, the adsorbed CO2 is desorbed from the electrode by applying a positive voltage. In an exemplary system shown herein, a voltage sweep of -1.7 V to 0.6 V was sufficient to adsorb and desorb the CO2.

Thus, disclosed herein is a method of adsorbing CO2 in a gaseous input, the method comprising: contacting the gaseous input with a non-aqueous solution comprising a dissolved electrolyte and having disposed therein a working electrode comprising a porous inorganic oxide, and a counter electrode; and applying a negative voltage across the electrodes wherein at least a portion of the CO2 in the gaseous input is adsorbed to the working electrode.

Preferably, the inorganic oxide comprises at least one reducible oxide. Non-limiting examples of suitable reducible oxides include T1O2. WO3, SnCh. Sb-SnCh, In-SnCh, and the like. In certain versions, the inorganic oxide comprises T1O2.

The electrolyte may comprise TBAPFg. In certain versions, the electrolyte may comprise TBAPFe and 1 -ethyl -3-methylimidazolium tetrafluoroborate (EMIMBF4).

Preferably, the negative voltage applied to the electrode to adsorb CO2 ranges from about -1.2 to about -1.8 V. Voltages above and below this range are explicitly within the scope of the disclosed method.

The method may further comprise sparging the electrolyte with a noble gas after applying the negative voltage.

The method may further comprise applying a positive voltage across the electrodes to desorb the CO2. The positive voltage can be applied by a positive sweep of potential from the negative voltage.

Also disclosed herein is a system configured to adsorb and desorb CO2, the system comprising: a working electrode comprising a porous inorganic oxide; a counter electrode: and a non-aqueous solution comprising a dissolved electrolyte.

The inorganic oxide of the working electrode comprises at least one reducible oxide. In certain versions, the inorganic oxide comprises one or more of TiCh, WO3, SnCh, Sb-SnCh, and In-SnO2. In certain versions, the inorganic oxide comprises TiCh.

The electrolyte may comprise TBAPFg. In certain versions, the electrolyte may comprise TBAPFg and EMIMBF4.

The method and system described herein address both the efficiency and stability challenges associated with current CO2 capture systems (e g., energy intensive desorption processes and degradation of organic materials via radical formation). Instead of applying substantial amounts of heat, the present method relies on the application of current at select voltages. In addition, the use of reducible inorganic oxides as electrosorbents (e g., TiCh) addresses both the energy and stability limitations described above. Further, an electrochemical approach has the potential to be agnostic to the CO2 concentration in the source gas. The method can also be run entirely on renewable electricity, thereby avoiding C'Ch-generating externalities.

The objects and advantages of the disclosure will appear more fully from the following detailed description of the preferred embodiment of the disclosure made in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1: A schematic illustration of the electrochemical adsorption and desorption process of CO2 on TiO2 as described herein.

Fig. 2: A scanning electron microscopic image of porous TiO2.

Fig.3: A graph showing the current caused by CO2 desorption by running a CV scan from -1.7 V to 0.6 V.

Fig. 4: A GC chromatogram showing signals of CO2 desorbed from a porous TiCh electrode after an oxidative cyclovoltammetry scan from -1.5 V to 0.6 V vs Ag/AgCl (10), and signals of CO2 remaining in acetonitrile solution after Ar sparging but before the oxidative desorption (12).

Fig. 5: A histogram showing maximum (white) and minimum (black) energies required to capture 1 mol of CO2 under flue gas conditions. GM NPQ (glyme-modified naphthoquinone) derivative was tested under anaerobic conditions. The porous TiCh system according to the present disclosure is circled. Abbreviations: MCDI: membrane capacitive deionization; PCET: proton-coupled electron transfer; BPMED: bipolar membrane electrodialysis; EMAR: electrochemically mediated amine regeneration; Co-SAC PSE: cobalt single atom catalyst porous solid electrolyte; GM NPQ: glyme-modified naphthoquinone; PAQ-CNT: Polyanthraquinone carbon nanotubes.

Fig. 6: Cyclic voltammetry scans of porous TiCh electrode after holding potentials in saturated CO2 acetonitrile, 0.1 M TBAPFe (2000 seconds) at -1.7 V (26), -1.6 V (22) and -1.5 V (18). The dashed lines 24 (-1.7 V), 20 (-1.6 V), and 16 (-1.5 V) are cyclic voltammetry scans performed under the corresponding potential conditions but under saturated CO2 solutions for 800 seconds, then followed by 1200 seconds of argon sparging while maintaining the potential hold. The solid line 14 is the cyclic voltammetry scan of argon-saturated solution. Fig. 7: Cyclic voltammetry scans of porous T1O2 electrode after holding potentials in saturated CO2 acetonitrile, 0.1 M TBAPFg and varying EMIMBF4 concentrations. The solid “Ar” line at bottom is a cyclic voltammetry scan of argon-saturated solution.

Fig. 8: Cyclic voltammetry scans of porous TiCh after holding potentials (—1.7 V, 600 seconds) in CO2 saturated acetonitrile, 0.1 M TBAPFg and 0.02 M EMIMBF4 concentrations. Cyclic voltammetry scans of porous TiCh electrode, placed in the same electrolyte concentrations and holding potential value, but for 600 seconds in saturated CO2 solution and 1200 seconds under argon sparging. The cyclic voltammetry scan of argon-saturated solution is shown in the solid “Ar” line at bottom.

DETAILED DESCRIPTION

Abbreviations and Definitions

ATO = Antimony-doped Tin Oxide (Sb-SnO2).

EMIMBF4 = l-Ethyl-3-methylimidazolium tetrafluoroborate.

ITO = Indium tin oxide (In-SnO2).

TBAPFg = Tetrabutylammonium hexafluorophosphate.

“Non-aqueous solvent” is used broadly herein to denote solvents other than water. Nonaqueous polar aprotic solvents are generally preferred, including but not limited to acetone, acetonitrile, dichloromethane, dimethylformamide, dimethyl sulfoxide, ethyl acetate, pyridine, sulfolane, tetrahydrofuran, and the like. Additionally, carbonate solvents may also be used, including, but not limited to ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, and the like. Halogenated benzenes, such as fluorobenzenes, may also be used. Ionic liquids such as imidazoles and their cations (imidzaoliums) may also be used - e g., ethylmethylimidazolium, dimethylimidazolium, etc. Also included within the definition are stable anions such as tetrafluorborate, perchlorate, and the like. Also included are halogenated acids such as trifluoromethanesulfonic acid.

Numerical ranges as used herein are intended to include every number and subset of numbers contained within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 2 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.

All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice-versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. The indefinite article '‘a” means ‘'one or more,” unless explicitly specified to the contrary. The word “or” is used inclusively and should be read as “and/or.”

All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary- by the context in which the referenced combination is made.

The methods of the present disclosure can comprise, consist of, or consist essentially of the essential elements and limitations of the method described herein, as well as any additional or optional ingredients, components, or limitations described herein or otherwise useful in electrochemistry. The disclosure provided herein may be practiced in the absence of any element or step which is not specifically disclosed herein.

Overview

To inhibit the exponential increase of atmospheric CO2 concentrations and their negative effects in changing global climate patterns, the development of efficient methods to capture and convert CO2 to useful chemicals is of paramount importance. Current technologies for CO2 capture rely on changes in pressure and temperature to adsorb and release CO2. Typically, the thermal energy required for CO2 release is high (around 100 to 180 kJ mof¹) and the adsorbents suffer from poor stability. Hope for better energy efficiencies was raised by the advent of electrochemical capture techniques. These approaches utilize electron transfer to an adsorbent (often a substituted quinone), which leads to the generation of negatively charged nucleophilic sites that reversibly bind to CO2. Carbonates are formed in the process. Yet, like thermal sorbents, these electrochemical sorbents continue to suffer from poor energy efficiency and stability, often lasting for only a few cycles of adsorption / desorption.

In the present method, these shortcomings are addressed by directly linking the CO2 adsorption site to the Fermi level of the electrode surface while avoiding the use of organic chemicals in the electrochemical CO2 sorption. This is possible when using inorganic reducible oxides as electrosorption materials. Like quinones, these materials can take up electrons under reducing conditions, forming nucleophilic sites that bind CO2. Because reducible oxides are only weakly able to promote the electrocatalytic transformation of CO2 to other products, applying oxidizing conditions afterwards allows for the release of CO2 from the material. Oxides are inorganic materials with very high mechanical, thermal, and electronic stability, thus the approach overcomes the major shortcomings of organic CO2 electrosorbents. The Method and System

To inhibit the exponential increase of atmospheric CO2 concentrations and their negative effects in changing global climate patterns, the development of efficient methods to capture and convert CO2 to useful chemicals is of paramount importance. Current technology for CO2 capture relies on changes in pressure and temperature to adsorb and release CO2. Typically, the thermal energy required for CO2 release is high (around 100 to 180 kJ mol'¹) and the adsorbents suffer from poor stability. Commercial CO2 capture plants from Climeworks (Zurich, Switzerland) use amine-functionalized sorbents such as 3-aminopropylmethyldiethoxysilane in thermal vacuum swings. They achieve relative stability only up to about 20 capture and release cycles. (Sim, Y. and Ruhaimi, A. Recent progress on (3 -Aminopropyl) triethoxysilane (APTES) functionalized-adsorbent for CO2 capture. In Journal of Physics: Conference Series, 2022; IOP Publishing: Vol. 2259, p 012008.) However, even the 20-cycle limit was achieved under non- realistic conditions. Hope for better energy’ efficiencies was raised by the advent of electrochemical capture techniques using substituted quinones. Yet, like thermal sorbents, these electrochemical sorbents continue to suffer from poor stability and energy efficiency

Disclosed herein is a novel electrochemical method to adsorb and desorb carbon dioxide molecules on porous inorganic oxide electrodes. The method achieves better energy efficiency and far greater stability than the conventional organic sorbents. The method disclosed herein uses titanium dioxide (T1O2) as a model compound inorganic oxide electrode. This is for brevity only. The method can be easily implemented using other reducible oxides. Non-limiting examples of the reducible oxides that can be used include WO3, SnCE, Sb-SnCh (ATO), In-SnCh (ITO), etc.

The present method rests on the property of TiO2 (and other reducible inorganic oxides) to form nucleophilic sites upon reduction. These nucleophilic sites serve as adsorption sites for CO2. Electrochemical reduction of TiO2, transforms some Ti⁴⁺ sites to Ti³⁺, which possess nucleophilic character. In the presence of H⁺ or Li⁺, for example, the charge on these reduced Ti centers is compensated by cation intercalation. This effect is used in some Li-ion batteries for energy storage (“LTO anodes"), where Li-intercalation and deintercalation can be carried out for thousands of cycles. This phenomenon confirms the robust stability of TiCL-based electrodes. In absence of such ions, however, the negative charge can be stabilized through its transfer to CO2, which leads to its binding in the form of a carbonate ion. Surprisingly, this effect has not been exploited for CO2 capture. T1O2 is shown herein to be an equally efficient and stable sorbent material for the electrochemical capture and release of CO2.

As shown in Fig. 1, the designed system involves the use of anon-aqueous solution (e.g., acetonitrile) with dissolved electrolytes as a medium for CO2 capture, a surface of porous titania as the working electrode, a counter electrode, a reference electrode, and a potentiostat. Mesoporous T1O2 was prepared by deposition of a titania paste dispersed in ethanol, which was subsequently calcined at 500 °C for 30 minutes. The surface morphology of the porous TiCh surface is shown in Fig. 2, compared the morphology- of the polished TiCh surface, the “rough"’ surface of the porous material is expected to accommodate adequate amount of CO2 adsorption.

Through analysis via cyclic voltammetry (CV), linear sweep voltammetry (LSV) and gas chromatography (GC), it was demonstrated successful electrochemical adsorption and subsequent desorption of CO2 in acetonitrile containing 0.1 M of tetrabutylammonium hexafluorophosphate (TBAPFg) as supporting electrolyte. To adsorb CO2, the electrolyte was saturated with CO2 and a potential of -1.7 V vs Ag/AgCl was applied for up to 14 min. (The Ag/AgCl electrode was a “leakless electrode” acquired commercially from eDAQ Pty Ltd, Denistone East, NSW, Australia) While still applying the same potential, CO2 was subsequently removed by sparging the electrolyte with argon. This step was followed by a positive sweep of the potential from -1.7 V to 0.6 V at 100 mV sec"¹. During this sweep, a cunent was observed corresponding to the desorption of CO2, demonstrating that T1O2 surfaces can be employed as an inorganic electrochemical CO2 capture medium as shown in Fig. 3.

In Fig. 4, line 10 shows the released CO2 dissolved in 1 mL of acetonitrile after adsorbing CO2 at - 1.5 V vs Ag/AgCl followed by sparging the solvent with Ar to remove excess CO2 in the solution. The amount of captured CO2 is calculated to be 1.15 pmol from a 0.20 cm² TiCh surface. The total number of charges passing through the electrode during the adsorption process is 144 mC, thus if assuming CO2 adsorption is a one electron process, the Faradaic efficiency is 90 %.

For efficient CO2 capture, the potential gap between the onsets of desorption and adsorption should be as small as possible since this voltage difference represents a loss in energy between the potential at which adsorption takes place and the one at which CO2 can be desorbed. The method demonstrates the onset of CO2 adsorption is at slightly below -1.4 V. As the adsorption of CO2 mostly occurred by holding the electrode under -1.7 V and the onset of desorption is at approximately 60 mV more positive or 6 kJ mol"¹, this is less than the 16 kJ mol" ¹ energy loss for the best sorbent material known to date, which is 4,4'-azopyridine. Even more, since the electrosorbent is an inorganic solid, it features substantially better stability- than existing adsorbent materials. For example, a test was performed for 210 cycles; a capacity fade of only 3% was observed.

Table 1, below-, compares results of the method and system disclosed herein to notable literature reports. Table 1. Comparison to Conventional CO2 Capture Methods

References:

1. Voskian, S.; Hatton, T. A. Faradaic electro-swing reactive adsorption for CO2 capture. Energy & Environmental Science 2019, 12 (12), 3530-3547.

2. Li, X.; Zhao, X.; Liu, Y .; Hatton, T. A.; Liu, Y. Redox-tunable Lewis bases for electrochemical carbon dioxide capture. Nature Energy 2022, 7 (11), 1065-1075.

3. Diederichsen, K. M.; Liu, Y.; Ozbek, N.; Seo, H.; Hatton, T. A. Toward solvent-free continuous-flow electrochemically mediated carbon capture with high-concentration liquid quinone chemistry. Joule 2022, 6 (1), 221-239. 4. Gebald, C.; Wurzbacher, J. A.; Tingaut, P.; Steinfeld, A. Stability of amine- functionalized cellulose during temperature-vacuum-swing cycling for CO2 capture from air. Environmental science & technology 2013, 47 (17), 10063-10070.

5. Liu, Y .; Ye, H; Diederichsen, K. M.; Van Voorhis, T.; Hatton, T. A. Electrochemically mediated carbon dioxide separation with quinone chemistry in salt-concentrated aqueous media. Nature Communications 2020, 1 1 , 2278.

As shown in Fig. 5, the maximum (white) and minimum (black) energies required to capture 1 mol of CO2 under flue gas conditions were also compared. A GM NPQ (glyme- modified naphthoquinone) derivative was tested under anaerobic conditions. The porous TiCh system (circled) requires much less energy to capture 1 mol of CO2 compared to other technologies.

Mechanistic Investigation

To gain insight into the electrochemical adsorption of CO2 to TiCh, a series of experimental investigations were performed, the results of which are displayed in Fig. 6. At 100 mV sec'¹, the largest desorption peak occurs at ca. -1.4 V. Secondary CO2 desorption peaks appear at about -0.3 V and +0.2 V vs Ag/AgCl. These peaks have a much larger potential gap from the adsorption onset; therefore they are considered to have higher binding energies. The desorption peaks attributed to the higher binding energy sites decrease with increasing time of Ar sparging. Furthermore, none of the more strongly bound CO2 w as observed when adsorption of CO2 was carried out at potentials below -1.6 V.

From a practical standpoint, CO2 desorption from the higher binding energy sites is less useful (because it requires more energy). Therefore, the Ar sparging does not significantly affect the CO2 binding at the preferred low er energies (preferred because of the small or non-existent adsorption/desorption potential gap). It also demonstrates that CO2 is chemisorbed strongly enough that sparging in noble gases will not remove the adsorbed CO2 on the T1O2 surface.

When testing the impact of the electrolyte, a rise in the absolute quantity of CO2 adsorbed was seen when adding EMIMBF4, to the base TBAPFg electrolyte. This phenomenon was observed while keeping the porous TiCL electrode under the same conditions as mentioned above. Fig. ⁷ shows this effect when increasing the concentration of EMIMBF4 from 0 M to 0.04 M in 0.01 M intervals. Most importantly, much of the increase in desorption peak intensity is in the voltage range betw een -1.7 V to -1.2 V, which is the preferred desorption site due to the adsorption potentials being in the same region. The improved binding of CO2 is due to improved stabilization of CCh' at the electrode surface. As shown in Fig. 8, with Ar sparging applied, there is no evident loss of CO2 adsorption on the T1O2 surface compared to that without Ar sparging.

Advantages and Use of the System

The present disclosure addresses both the efficiency and stability challenges of current electrochemical CO2 capture systems. The system works using very inexpensive materials, such as TiO2, which is widely available and commonly used in white paint, coatings, ink and even toothpaste. Electrochemical CO2 capture/release on inorganic oxides offers the ability to control the nucleophilicity of the electrode surface. Defining the difference of the onset potential at the desorption peak and the negative potential at which the electrode was held at during adsorption of CO2, then the energy of releasing the captured low-binding energy CO2 is calculated to be approximately 6 kJ mol for when CO2 was captured at -1.7 V. This energy is lower than that for typical pressure, temperature swings, and systems using quinones. Also, the present method and system does not require the membranes that are required when using organic compounds in electrochemical CO2 capturing processes. Electrochemically mediated amine regeneration and proton-coupled electron transfer-mediated CO2 capture requires such membranes to function.

The system disclosed herein can be used as a device to electrochemically capture CO2 under ambient conditions. The method has a substantially smaller energy gap between the adsorption and desorption potential. The adsorbent material is entirely inorganic and can thus be expected to feature substantially higher stability than the commonly used organic sorbents which are notoriously unstable.

The system disclosed herein can be used as a component in enclosed spaces that require scrubbing of CO2 from the local atmosphere, such as in high-altitude aircraft, spacecraft, and submarines. It can also be used to remove CO2 from flue gas. The system disclosed herein will play a crucial part in the effort of using cheap and renewable electricity to capture and store CO2, hence leaving investment opportunities for companies that wish to earn carbon credits or to avoid emission penalties.

Claims

CLAIMS What is claimed is:

1. A method of adsorbing CO2 in a gaseous input, the method comprising: contacting the gaseous input with a non-aqueous solution comprising a dissolved electrolyte and having disposed therein a working electrode comprising a porous inorganic oxide, and a counter electrode: and applying a negative voltage across the electrodes wherein at least a portion of the CO2 in the gaseous input is adsorbed to the working electrode.

2. The method of claim 1, wherein the inorganic oxide comprises at least one reducible oxide.

3. The method of any one of claims 1-2, wherein the inorganic oxide comprises one or more of T1O2. WO3, SnCh, Sb-SnCh, and In-SnCh.

4. The method of any one of claims 1-3, wherein the inorganic oxide comprises T1O2.

5. The method of any one of claims 1-4, wherein the electrolyte comprises hexafluorophosphate (TBAPFg)

6. The method of any one of claims 1-5, wherein the electrolyte comprises TBAPFg and l-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4).

7. The method of any one of claims 1 -6, wherein the CO2 saturates the electrolyte upon contacting the gaseous input with the electrolyte.

8. The method of any one of claims 1-7, wherein the negative voltage ranges from about -1.2 to about -1.8 V.

9. The method of any one of claims 1-8, further comprising sparging the electrolyte with a noble gas after applying the negative voltage.

10. The method of any one of claims 1-9, further comprising applying a positive voltage across the electrodes to desorb the CO2.

11. The method of claim 10, wherein the positive voltage is applied by a positive sweep of potential from the negative voltage.

12. A system configured to adsorb and desorb CO2, the system comprising: a working electrode comprising a porous inorganic oxide; a counter electrode: and a non-aqueous solution comprising a dissolved electrolyte.

13. The system of claim 12, wherein the inorganic oxide comprises at least one reducible oxide.

14. The system of any one of claims 12-13, wherein the inorganic oxide comprises one or more of T1O2. WO3, SnCh, Sb-SnCh, and In-SnCh.

15. The system of any one of claims 12-14, wherein the inorganic oxide comprises T1O2.

16. The system of any one of claims 12-15, wherein the electrolyte comprises TBAPFe.

17. The system of any one of claims 12-16, wherein the electrolyte comprises TBAPF₆ and EMIMBF4.