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EP-4602196-B1 - CO2 ELECTROREDUCTION TO MULTI-CARBON PRODUCTS IN ACIDIC CONDITIONS COUPLED WITH CO2 REGENERATION FROM CARBONATE

EP4602196B1EP 4602196 B1EP4602196 B1EP 4602196B1EP-4602196-B1

Inventors

  • SCHREIBER, Moritz Wilhelm
  • PERAZIO, Alessandro
  • FONTECAVE, MARC
  • CREISSEN, Charles E.

Dates

Publication Date
20260513
Application Date
20230926

Claims (15)

  1. Process for electrolysing carbon dioxide, said process is characterized in that it comprising the following steps: a) providing a system comprising a gas-fed flow cell comprising a gas chamber with a gas inlet, a gas outlet, a catholyte chamber, and a gas diffusion electrode comprising a metal-based catalyst, wherein the gas diffusion electrode is placed between the gas chamber and the catholyte chamber; b) providing a catholyte flow and an anolyte flow into said gas-fed flow cell; c) activating said gas-fed flow cell under operating conditions; d) providing a gas input flow comprising carbon dioxide using the gas inlet of the gas chamber to produce a direct gas stream exiting from the gas outlet of the gas chamber and a liquid catholyte output flow from the catholyte chamber comprising products, wherein said liquid catholyte output flow is degassing in a catholyte reservoir to produce an indirect gas stream exiting from a gas outlet of the catholyte reservoir; wherein the catholyte flow is an acidic catholyte flow comprising one or more alkali metal cations and in that the gas-fed flow cell comprises a bipolar membrane includes a cation-exchange layer in contact with the catholyte and an anion-exchange layer in contact with the anolyte; wherein the cation-exchange layer provides protons to the catholyte and the anion exchange layer provides hydroxide ions to the anolyte; in that the acidic catholyte has a pH of at most 5.5 and in that the catholyte pH is less than the anolyte pH.
  2. The process according to claim 1 is characterized in that the indirect gas stream exiting from the catholyte reservoir comprises carbon dioxide, and in that the process further comprises a step e) of recovering the indirect gas stream exiting from the catholyte reservoir and recycling said indirect gas stream into the gas input flow comprising carbon dioxide of step d).
  3. The process according to claim 1 or 2 is characterized in that the gas input flow provided in step (d) has a flow rate ranging from 0.5 to 10 mL/min; preferably from 0.9 to 2.8 mL/min or from 1.0 to 2.5 mL/min.
  4. The process according to any one of claims 1 to 3 is characterized in that the acidic catholyte has a pH ranging from 0.5 to 5.4; preferably from 1.0 to 4.0.
  5. The process according to any one of claims 1 to 4 is characterized in that the anolyte has a pH ranging from 7 to 15; preferably from 10 to 14.
  6. The process according to any one of claims 1 to 5 is characterized in that the acidic catholyte comprises one or more acids at a concentration ranging from 0.01 to 1.0 M and one or more alkali metal cation donors at a concentration ranging from 1.0 to 5.0 M.
  7. The process according to claim 6 is characterized in that the one or more alkali metal cations are one or more selected from Cs + , K + , Li +, and Na + ; preferably the one or more alkali metal cations are or comprise K + .
  8. The process according to any one of claims 1 to 7 is characterized in that the acidic catholyte comprises one or more alkali metal cation donors selected from caesium chloride, caesium iodide, caesium sulfate, caesium phosphate, caesium hydroxide, potassium chloride, potassium phosphate monobasic, potassium sulfate, potassium iodide, potassium hydroxide, lithium chloride, lithium iodide, lithium sulfate, lithium phosphate, lithium hydroxide, sodium chloride, sodium sulphate, sodium iodide, sodium phosphate and sodium hydroxide; preferably selected from potassium chloride, potassium phosphate monobasic, potassium sulfate, potassium iodide, and potassium hydroxide; more preferably the one or more alkali metal cation donors are or comprise potassium chloride.
  9. The process according to claim 8 is characterized in that the one or more alkali metal cation donors at a concentration ranging from 0.5 to 5.0 M; preferably ranging from 2.0 to 4.0 M.
  10. The process according to any one of claims 1 to 9 is characterized in that the acidic catholyte comprises one or more acids selected from hydrochloric acid, sulfuric acid, hydrobromic acid, hydriodic acid, perchloric acid, and chloric acid; preferably sulfuric acid.
  11. The process according to claim 10 is characterized in that the one or more acids are present at a concentration ranging from 0.01 to 1.0 M; preferably, from 0.02 to 0.5 M; more preferably ranging from 0.03 to 0.2 M.
  12. The process according to any one of claims 1 to 11 is characterized in that the metal of the metal-based catalyst is selected from copper, silver and any mixture thereof; and/or the metal-based catalyst is or comprises copper oxide nanoparticles and the process comprises a catalyst activation step to reduce copper oxide to metallic copper.
  13. The process according to any one of claims 1 to 12 is characterized in that the operating conditions at which the flow cell is operated in step c) comprise current density ranging from -100 mA.cm 2 to -1.5 A.cm 2 ; preferably from -150 mA.cm 2 to -800 mA.cm 2 .
  14. A system (1) suitable to perform the process for electrolysing carbon dioxide according to any one of claims 1 to 13, the system comprising a gas-fed flow cell (3) comprising a gas chamber (5), a catholyte chamber (7) and an anolyte chamber (9), wherein said gas chamber (5) is separated from the catholyte chamber (7) by a gas diffusion electrode (17), said gas diffusion electrode (17) having a gas diffusion membrane being comprised within said gas chamber, wherein said catholyte chamber (7) and said anolyte chamber (9) comprise respectively a cathode and an anode, and wherein the system (1) further comprises catholyte (23) and anolyte (25) and means (27; 29) to flow the catholyte (23) and the anolyte (25) within respectively said catholyte chamber (7) and said anolyte chamber (9); wherein the system is characterized in that the catholyte flow is an acidic catholyte flow comprising one or more alkali metal cations and in that the gas-fed flow cell comprises a bipolar membrane (19) that includes a cation-exchange layer in contact with the catholyte and an anion-exchange layer in contact with the anolyte; wherein the cation-exchange layer provides protons to the catholyte and the anion exchange layer provides hydroxide ions to the anolyte; in that the acidic catholyte has a pH of at most 5.5 and in that the catholyte pH is less than the anolyte pH; and wherein the system (1) further comprises a catholyte reservoir to receive and degas the liquid catholyte output flow exiting the catholyte chamber, and with preference, means (31) to recover an indirect gas stream exiting the gas outlet (33) of the catholyte reservoir, and means (35) to recycle the said indirect gas stream back into the gas chamber (5).
  15. Use of a system comprising a gas-fed flow cell (3) with a bipolar membrane (19) in a process for electrolysing carbon dioxide under acidic conditions in the presence of one or more alkali metal cations; wherein the system is according to claim 14 and/or the process is according to any one of claims 1 to 13.

Description

Technological field The present disclosure relates to processes and systems comprising a gas-fed flow cell for electrochemical carbon dioxide reduction, for example, to upgrade greenhouse gases such as carbon dioxide to valuable fuels and feedstocks. Technological background Electrochemical carbon dioxide reduction (CO2R) offers a sustainable route to generate valuable chemical products from CO2 and renewable electricity sources. Recent progress has brought CO2R closer to commercial viability through the development of devices that overcome the severe limitations of mass transport arising from the low solubility of CO2 in aqueous solutions. One example is the gas-fed flow cell, in which the CO2 is supplied as a gas through the back of a gas-diffusion electrode (GDE) in contact with a flowing electrolyte solution. These devices can regularly attain high current densities (hundreds of mA cm-2) at low overpotentials (<1 V). However, the common use of alkaline or neutral pH electrolyte solutions has prohibited high conversion yields due to the unwanted reaction of CO2 with hydroxide ions, which results in reactant loss through the formation of (bi)carbonate (Figure 3a). These species can be externally converted back to CO2, but the regeneration process accounts for more than half of the energy required for the electrolyser in the case of an alkaline flow cell. The problem can be partly addressed by using acidic electrolyte solutions where the pH is below the pKa of bicarbonate formation. In such systems, while the CO2 is still converted to (bi)carbonate (Eq.1 and Eq. 2) by the alkaline local pH at the cathode arising from hydroxide ions generated during CO2 reduction (Eq. 3), these (bi)carbonate species are immediately converted back to CO2 (termed r-CO2 as this is regenerated) due to the low bulk pH (Eq. 4). (Figure 3b). This provides the possibility to recycle and re-react the r-CO2, which maximizes the conversion yield of the CO2R since all the reactant is ultimately converted into reduction products and is not permanently lost as (bi)carbonate.         CO2 + OH- HCO3-     Equation 1         HCO3- + OH- CO32- + H2O     Equation 2         CO2 + H2O + 2e- CO + 2 OH-     Equation 3         HCO3- + H+ r-CO2+ H2O     Equation 4 However, a major fraction of input CO2 is consumed by the electrolyte through reactions with the hydroxide to form carbonate/bicarbonate in both alkaline and neutral reactors. Acidic routes for CO2R have been studied to overcome this limitation. However, it was found that the acidic route also promotes the hydrogen evolution reaction (HER). X. Huang et al., in Science, 2021, 372, 1074-1078 report that concentrating potassium cations in the vicinity of electrochemically active sites accelerates CO2 activation to enable efficient CO2R in acid. CO2R was achieved on copper at pH <1 with a single-pass CO2 utilization of 77%, including a conversion efficiency of 50% toward multicarbon products (ethylene, ethanol, and 1-propanol) at a current density of 1.2 amperes per square centimeter and a full-cell voltage of 4.2 volts. Y. Xie et al., in Nature Catalysis, 2022, 5, 564-570, report a design strategy that suppresses hydrogen evolution reaction activity by maximizing the co-adsorption of CO and CO2 on Cu-based catalysts to weaken H* binding. Using density functional theory studies, it was found Pd-Cu promising for selective C2+ production over C1, with the lowest ΔGOCCOH* and ΔGOCCOH* - ΔGCHO*. Pd-Cu catalysts were synthesized and reported a crossover-free system (liquid product crossover <0.05%) with a Faradaic efficiency of 89 ± 4% for CO2 to C2+ at 500 mA cm-2, simultaneous with single-pass CO2 utilization of 60 ± 2% to C2+. J. Gu et al., in Nature Catalysis, 2022, 5, 268-276, show that by suppressing the otherwise predominant hydrogen evolution using alkali cations, efficient CO2 electroreduction can be conducted in an acidic medium, overcoming the carbonate problem. The cation effects are general for three typical catalysts including carbon-supported tin oxide, gold, and copper, leading to Faradaic efficiency of as high as 90% for formic acid and CO formation. The analysis suggests hydrated alkali cations physisorbed on the cathode modify the distribution of electric field in the double layer, which impedes hydrogen evolution by suppressing the migration of hydronium ions while at the same time promoting CO2 reduction by stabilizing key intermediates. Although the above techniques are promising, there is still room for improvement. For example, the use of proton exchange membranes leads to a crossover of metal ions, cationic electrolyte species, and products, which can negatively impact device performance and stability over long durations. The use of acidic anolytes requires acid-tolerant oxygen evolution reaction (OER) catalysts based on precious metals such as Ir or Ru, which increase the costs involved. WO2019/051609 discloses processes and apparatus for electrocatalytically reduc