Interposed electrode assembly for electroreduction of carbon oxides to c2+ products

Abstract

The present disclosure relates to an electrode assembly for operating electroreduction of carbon monoxide into carbon products, the electrode assembly comprising a cathodic compartment having a cathodic inlet and a cathodic outlet; a cathode comprising a cathodic catalyst and being in fluid communication with the cathodic compartment; an anode comprising an anodic catalyst being positioned away from the cathode so as to form a gap; an anodic compartment being in fluid communication with the anode, the anodic compartment having an anodic inlet; and an interposer comprising a porous and hydrophilic material being positioned in the gap between the anode and the cathode, wherein the porous and hydrophilic material has pores being at least partially filled with an anolyte when electroreduction is performed to conduct both cations and anions across the gap via the anolyte.

Description

[0001] INTERPOSED ELECTRODE ASSEMBLY FOR ELECTROREDUCTION OF CARBON OXIDES TO C2+PRODUCTS

[0002] TECHNICAL FIELD

[0003]

[0001] The present techniques generally relate to electroreduction of CO, CO2or a mixture thereof to carbon products, and more particularly to an electrode assembly that is configured to enhance electroreduction performance by including an interposer.

[0004] BACKGROUND

[0005]

[0002] Electrochemical CO2reduction (CO2R), when powered by renewable energy, provides a promising route to upgrade waste CO2into valuable multi-carbon (C2+) chemicals and fuels. Performing CO2R in alkaline media enables an impressive energy efficiency (EE) over 40% towards C2+products (graph a, Figure 4). However, carbonate formation in alkaline CO2R leads to inefficient CO2utilization and prohibitive cost associated with CO2regeneration. Approaches such as performing CO2R in acidic electrolytes or employing bipolar membranes to regenerate CO2have addressed the CO2loss problem, but the EE of these systems remains below 20% (graph a, Figure 4).

[0006]

[0003] Cascade CO2R started with CO2-to-CO in a carbon-efficient system followed by CO reduction (COR) provides a carbon- and energy-efficient pathway towards the synthesis of C2+products. The first CO2-to-CO step can be performed in an established high-temperature solid-oxide electrolyzer (SOEC) with an EE over 80%. Recent energy analyses demonstrate that the CO2-to-CO step accounts for less than 10% of the total energy input of the cascade approach. Therefore, further advances of the cascade approach hinge on improvement of the COR step.

[0007]

[0004] CO does not react with hydroxide and thus avoids carbonate formation. Operating COR in alkaline conditions benefits from improved kinetics and reduced Nernstian pH losses. COR is typically performed in a membrane electrode assembly (MEA) which the cathode and anode are only separated by an anion exchange membrane (AEM, schematic b of Figure 4). AEM serves as an electrical and fluid isolator between the electrodes. The absence of catholyte minimizes distance between the electrodes, reducing ohmic resistance and improving energy efficiency. This enables an EE of 30% towards C2+ products (graph a, Figure 4). However, the economic viability of the technology requires further advance in EE beyond 50%. Inefficiency of COR systems arise from the high voltage losses associated with the electrolyzer - one such loss is from the membrane materials.

[0008]

[0005] The AEM is at the centre of the membrane electrode assembly, selectively conducting the anions (negatively charged hydroxides) via the hydrophilic cationic functional groups, while mitigating the transport of cations. However, current AEMs remain relatively low in conductivity compared to the cation exchange counterparts. The alkaline bulk electrolyte is more than 5-fold more conductive than AEMs.

[0009]

[0006] EP 3 460 103 A1 describes an electrochemical reaction device, comprising: an anode to oxidize a first substance; a first flow path facing on the anode and through which a liquid containing the first substance flows; a cathode to reduce a second substance; a second flow path facing on the cathode and through which a gas containing the second substance flows; a porous separator provided between the anode and the cathode; and a power supply connected to the anode and the cathode. A thickness of the porous separator is 1 pm or more and 500 pm or less. An average fine pore size of the porous separator is larger than 0.008 pm and smaller than 0.45 pm. A porosity of the porous separator is higher than 0.5.

[0010]

[0007] US 2023 / 0079481 A1 describes a carbon dioxide electrolytic device including an electrolysis cell including: an anode configured to oxidize water to produce oxygen; a cathode configured to reduce carbon dioxide to produce carbon compound; a cathode flow path plate having a surface provided in contact with the cathode and a cathode flow path provided on the surface and facing to the cathode; and a separator provided between the anode and the cathode. The surface has a hydrophilic region provided on the cathode and having a contact angle to water of less than 45 degrees.

[0011]

[0008] WO 2023 / 038116 A1 describes a carbon dioxide reduction electrolysis tank that electrochemically reduces carbon dioxide and that comprises: a cathode that reduces carbon dioxide; a carbon dioxide flow channel that supplies gaseous carbon dioxide to the cathode; an anode where an oxidation reaction progresses; an electrolyte flow channel that supplies an electrolyte to the anode; and a hydrophilic porous diaphragm disposed between the cathode and the anode. The carbon dioxide reduction electrolysis tank has a structure in which a first surface of the porous diaphragm contacts the cathode, and at least a portion of the cathode is hydrophilic.

[0009] There is thus still a need for a technology that overcomes at least some of the drawbacks of what is known in the field of carbon oxides electroreduction.

[0012] SUMMARY

[0013]

[0010] Electrochemical CO reduction (COR) offers a carbonate-free approach to produce C2+ products. However, current anion exchange membranes (AEMs) used for COR suffer low conductivities that result in low energy efficiency. Here, we developed an interposed electrode assembly (IEA), namely an electrode assembly where a hydrophilic interposer hydrated with highly conductive electrolytes allows fast conduction of ions across the electrodes, that is capable for enabling a 150-mV reduction in full-cell voltage compared to the AEM when operating at 200 mA / cm2. We further optimized the system by integrating the system with a highly active nickel-iron-boride (NiFeB) OER catalyst and tuning the operation temperature of the IEA. When operated at 50 °C, a full-cell voltage of -1.95 V and a record energy efficiency of 51 % towards C2+ products were achieved at 200 mA / cm2. The system also operated stably for more than 10 days (250 hours) and achieved a CO single-pass conversion of 97% and a C2H4concentration of 87 wt% from the cathode.

[0014]

[0011] In a first aspect, the present disclosure relates to an electrode assembly for operating electroreduction of carbon monoxide into carbon products, the electrode assembly comprising: a cathodic compartment having a cathodic inlet for receiving a gas stream comprising CO and a cathodic outlet for releasing the carbon products including ethylene that are produced according to COR; a cathode comprising a cathodic catalyst and being in fluid communication with the cathodic compartment; an anode comprising an anodic catalyst being positioned away from the cathode so as to form a gap; an anodic compartment being in fluid communication with the anode, the anodic compartment having an anodic inlet for receiving an anolyte and an anodic outlet for releasing oxygen produced according to an Oxygen Evolution Reaction (OER) at the anode; and an interposer comprising a porous and hydrophilic material being positioned in the gap between the anode and the cathode, wherein the hydrophilic material is defined as a material with a contact angle of at most 140 degress as determined according to ISO 19403-6:2017 wherein the pores of the porous and hydrophilic material have an average pore size ranging between 0.30 pm and 10 pm as measured by a porosimeter and the interposer has a thickness between 50 pm and 100 pm as measured by a thickness gauge.

[0015]

[0012] Advantageously, the porous and hydrophilic material has a porosity of at least 20% as measured by a porosimeter, preferably at least 35%, even more prefereably at least 60%, or most preferably at least 80%.

[0016]

[0013] Advantageously, the porous and hydrophilic material has a porosity ranging between 20 % and 99 % as measured by a porosimeter; preferably between 25% and 95%, more preferably between 30% and 90%, even more preferably between 35% and 85%.

[0017]

[0014] Advantageously, the pores of the porous and hydrophilic material have an average pore size of at least 0.05 pm as measured by a porosimeter, preferably at least 0.20 pm, even more preferably at least 0.30 pm, or most preferably at least 0.35 pm; or most preferably at least 0.40 pm; or most preferably at least 0.45 pm.

[0018]

[0015] Advantageously, the pores of the porous and hydrophilic material have an average pore size ranging between 0.05 pm and 15 pm, or between 0.1 pm and 10 pm as measured by a porosimeter; with preference between 0.07 and 9 pm, more preferably between 0.09 and 5 pm, even more preferably between 0.25 pm and 1 pm, most preferably between 0.30 pm and 0.90 pm, and most preferably and 0.45 pm and 0.80 pm.

[0019]

[0016] Advantageously, the interposer has a thickness of at most 120 pm as measured by a thickness gauge, preferably at most 100 pm, more preferably 95 pm, even more preferably at most 90 pm, preferably at most 85 pm, preferably at most 80 pm, preferably at most 75 pm, preferably at most 70 pm.

[0020]

[0017] Advantageously, the interposer may have a thickness of at least 5 pm as measured by a thickness gauge, preferably at least 15 pm, more prefereably at least 25 pm, even more prefereably at least 35 pm, even more preferably at least 45 pm, and most prefereably at least 50 pm, or at least 55 pm or at least 60 pm.

[0018] Advantageously, the interposer has a thickness between 5 pm and 500 pm as measured by a thickness gauge; with preference, between 15 pm and 450 pm, or between 25 pm and 400 pm, or between 35 pm and 350 pm, or between 45 pm and 300 pm, or between 50 pm and 275 pm, or between 55 pm and 250 pm, or between 60 pm and 200 pm as measured by a thickness gauge.

[0021]

[0019] In a prefered embodiment, the interposer has a thickness between 5 pm and 120 pm as measured by a thickness gauge, optionally, between 15 pm and 100 pm, or between 25 pm and 95 pm, or between 35 pm and 90 pm, or between 45 pm and 85 pm, or between 50 pm and 80 pm, or between 55 pm and 75 pm, or between 60 pm and 70 pm as measured by a thickness gauge.

[0022]

[0020] Advantageoulsly, the porous and hydrophilic material is one or more selected from polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone, polypropylene, polyethylene, nylon, polycarbonate, cellulose acetate, cellulose nitrate, mixed cellulose ester. With preference, the porous and hydrophilic material is or comprises polytetrafluoroethylene (PTFE) and / or polyvinylidene fluoride (PVDF). More preferably the porous and hydrophilic material is or comprises polytetrafluoroethylene (PTFE).

[0023]

[0021] Advantageously, the anodic catalyst is a metal-based catalyst comprising nickel, iron, iridium, ruthenium, cobalt, magnesium, or any combinations thereof. With preference, the anodic catalyst is a metal-based catalyst comprising nickel and / or iron.

[0024]

[0022] For example, the anodic catalyst comprises an oxide, a boride, a sulfide, a nitride, and / or a phosphide of the metal-based catalyst.

[0025]

[0023] For example, the anodic catalyst is a NiFe catalyst.

[0026]

[0024] For example, the anodic catalyst comprises metal and / or non-metal dopants in the range of 0.1-10 atomic weight % as determined by X-ray photoelectron spectroscopy, optionally the dopant being boron.

[0027]

[0025] For example, the anodic catalyst is a NiFe catalyst with metal and / or non-metal dopants in the range of 0.1-10 atomic weight % as determined by X-ray photoelectron spectroscopy.

[0028]

[0026] For example, the anodic catalyst is a NiFe catalyst comprises boron and is a NiFe- B catalyst.

[0027] Advantageously, the cathodic catalyst comprises Cu, Ag, Au, Sn, Pb, Bi, Pd, an alloy thereof, or any combinations thereof. With preference, the cathodic catalyst comprises Cu.

[0029]

[0028] In a second aspect, the present disclosure relates to the use of a porous and hydrophilic material in an electrolyzer to perform electroreduction of carbon monoxide into carbon products, wherein the porous and hydrophilic material is used as an interposer being positioned between a cathode and an anode of the electrolyzer, wherein the hydrophilic material is defined as a material with a contact angle of at most 140 degress as determined according to ISO 19403-6:2017, the pores of the porous and hydrophilic material have an average pore size between 0.30 pm and 10 pm as measured by a porosimeter and the interposer has a thickness between 50 pm and 100 pm as measured by a thickness gauge.

[0030]

[0029] Advantageously, the interposer has at least one feature as defined above.

[0031]

[0030] In a third aspect, the present disclosure relates to a process for electroreducing carbon monoxide into carbon products, the process comprising: providing an electrode assembly as defined in the first aspect, supplying the gas stream comprising CO to the cathodic inlet of the cathodic compartment of the eleclectrode assembly, wherein, based on the total weight of the input gas stream, the CO is present at a content of between 5 wt.% and 100 wt.% as determined by gas chromotography; supplying the anolyte to the anodic inlet of the anodic compartment of the electrode assembly; applying a current density to the anode and the cathode to sustain ion conduction through the interposer and generate carbon products in the product stream.

[0032]

[0031] Advantageously, the CO may be present at a content of between 5 wt.% and 100 wt.%, preferably between 10 wt.% and 95 wt.%, or most preferably between 15 wt.% and 90 wt.% based on the total weight of the input gas stream as determined by gas chromatography.

[0033]

[0032] In some implementations, the CO may be present at a content of at least 5 wt.%, or at least 10 wt.% or at least 15 wt.% based on the total weight of the input gas stream as determined by gas chromotography.

[0033] In some implementations, the CO may be present at a content of at most 100 wt.%, or at most 95 wt.% or at most 90 wt.% based on the total weight of the input gas stream as determined by gas chromotography.

[0034]

[0034] Advantageously, the current density is between 50 and 1500 mA.cnr2, or between 150 and 1250 mA. cm-2, or between 200 and 1000 mA.cnr2. With preference, the current density is between 50 and 500 mA. cm-2, preferably between 100 and 300 mA.cnr2, more preferably between 150 and 250 mA.cnr2, or most preferably between 180 and 220 mA. cm-2.

[0035]

[0035] In one embodiment, the anolyte is preferably alkaline and the anolyte preferably comprises LiOH, NaOH, KOH, CsOH or any mixtures thereof. For example, the anolyte is NaOH.

[0036]

[0036] In another embodiment, the anolyte is preferably neutral and the anolyte preferably comprises an alkali sulfate, an alkali bicarbonate or a combination thereof.

[0037]

[0037] Advantageously, the anolyte has a concentration between 0.1M and 10M, optionally between 1 M and 3M, further optionally between 1.5M and 2M. Preferably, the anolyte concentration is between 1.5M and 2.5M. Most preferably, the anolyte concentration is between 1.8M and 2.2M.

[0038]

[0038] For example, the anolyte has a concentration of at most 10 M, preferably of at most 3 M, more preferably of at most 2 M, even more preferably of at most 2.5M, or most preferably of at most 2.2M.

[0039]

[0039] For example, the anolyte has a concentration of at least 0.1 M, preferably of at least 1 M, more preferably of at least 1.5 M, or most preferably at most 1.8M.

[0040]

[0040] Advantageously, the process further comprises the step of heating the electrode assembly to maintain the anolyte at a temperature between 20°C and 80°C, optionally between 20°C and 50°C. Preferably, the temperature of the anolyte is between 30°C and 70°C, or more preferably between 40°C and 60°C, or most prefereably between 45°C and 55°C.

[0041]

[0041] Advantagesouly, the gas stream is supplied to the cathodic inlet with a flow rate between 0.05 and 20 seem. cm-2, further optionally between 0.75 and 3 seem. cm-2. Preferably, supplying the gas stream to the cathodic inlet is performed at a flow rate between 0.1 and 1 seem. cm-2,

[0042]

[0042] Advantageoulsy, the gas stream comprises CO and CO2. For example, a CO / CO2ratio can be between 1 :9 and 9:1 .

[0043]

[0043] For example, the gas stream further comprisies H2, namely the gas stream is syngas. For example, a H2 / carbon oxides ratio can be between 1 :1 and 3:1.

[0044]

[0044] Advantageoulsy, said process is catholyte-free.

[0045]

[0045] Alternatively, said process advantageously comprises a catholyte. With preference, said catholyte can be the same as the anolyte defined herein. For example, the catholyte can include LiOH, NaOH, KOH, CsOH or any mixtures thereof.

[0046]

[0046] While the present techniques will be described in conjunction with example embodiments, it will be understood that it is not intended to limit the scope of the invention to such embodiments. On the contrary, it is intended to coverall alternatives, modifications and equivalents as may be included as defined by the present description. The objects, advantages and other features of the present invention will become more apparent and be better understood upon reading of the following non-restrictive description of the invention, given with reference to the accompanying drawings.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048]

[0047] Implementations of the IEA and related process are represented in and will be further understood in connection with the following figures.

[0049]

[0048] Figure 1 includes schematic a representing the structure of an Interposed Electrode Assembly (IEA) as encompassed herein; graph b showing cell voltage versus current density for COR performance in a Membrane Electrode Assembly (MEA) including an AEM or in the IEA using a 2M NaOH electrolyte; graph c showing Energy Efficiency (EE) in carbon products versus current density for COR performance in the MEA or in the IEA using the 2M NaOH electrolyte; and graph d showing crossover gas composition from the cathode to the anode versus current density for COR performance in the MEA or in the IEA using the 2M NaOH electrolyte.

[0049] Figure 2 includes Scanning Electron Microscopy (SEM) images a and b of the surface of a porous and hydrophilic material being polytetrafluoroethylene (PTFE) and used as an interposer in an IEA according of the present invention.

[0050]

[0050] Figure 3 is a Scanning Electron Microscopy (SEM) image of the surface of a cathode including a copper catalyst.

[0051]

[0051] Figure 4 includes graph a showing a single-pass conversion efficiency versus Energy Efficiency toward ethylene in alkaline CO2R, acidic CO2R, neutral CO2R, alkaline COR, alkaline COR in IEA; schematic b representing a conventional Membrane Electrode Assembly (MEA), graph c showing Faradaic Efficiency in carbon products and Cell Voltage versus Current Density for alkaline COR using a copper COR catalyst; and graph d showing Energy Efficiency by carbon products versus Current Density for alkaline COR using a copper COR catalyst.

[0052]

[0052] Figure 5 includes graph a showing anode crossover gas composition and C2H4Faradaic efficiency found at anode versus current density for COR using a membrane- free electrolyzer; graph b showing Faradaic Efficiency of H2and ethylene versus current density for COR using the membrane-free electrolyzer; and graph c showing Faradaic Efficiency share for ethylene between anode and cathode versus current density for COR using the membrane-free electrolyzer.

[0053]

[0053] Figure 6 includes graph a showing cell voltage versus current density for COR using an Interposed Electrode Assembly (IEA) for three different electrolytes LiOH, NaOH and KOH; graph b showing Faradaic Efficiency of products vs current density for COR using the IEA and 2M LiOH as anolyte; graph c showing Faradaic Efficiency of products vs current density for COR using the IEA and 2M NaOH as anolyte; and graph d showing Faradaic Efficiency of products vs current density for COR using the IEA and 2M KOH as anolyte.

[0054]

[0054] Figure 7 includes graph a showing cell voltage versus current density for COR using an Interposed Electrode Assembly (IEA) for three different concentrations of the NaOH anolyte; graph b showing Faradaic Efficiency of products vs current density for COR using the IEA and 1 M NaOH as anolyte; graph c showing Faradaic Efficiency of products vs current density for COR using the IEA and 2M NaOH as anolyte; and graph d showing Faradaic Efficiency of products vs current density for COR using the IEA and 5M NaOH as anolyte.

[0055] Figure 8 is a SEM image of the surface of an anode including a NiFe-B catalyst.

[0055]

[0056] Figure 9 includes six transmission electron microscopy (TEM) energy dispersive x-ray elemental mappings images of the surface of an anode including a NiFe-B catalyst (with “mix” referring to a mapping combining Fe, Ni, B and O elements).

[0056]

[0057] Figure 10 includes graphs a and b being X-ray photoelectron spectrograms of a NiFe-B catalyst showing Ni, Fe, and B elemental signals.

[0057]

[0058] Figure 11 includes graph a showing Faradaic Efficiency of products vs current density for COR using the IEA including a Cu cathode and an IrOx anode in 2M NaOH as anolyte; and graph b showing Faradaic Efficiency (FE) of products vs current density for COR using the IEA including a Cu cathode and a NiFe-B anode in 2M NaOH as anolyte.

[0058]

[0059] Figure 12 includes graph a showing cell voltage versus current density for COR using the IEA including a Cu cathode and an IrOx or NiFe-B anode in 2M NaOH as anolyte; graph b showing Energy Efficiency (EE) towards carbon products versus current density for COR using the IEA including a Cu cathode and an IrOx or NiFe-B anode in 2M NaOH as anolyte; graph c showing Faradaic Efficiency (FE) of products vs current density for COR using the IEA including a Cu cathode and a NiFe-B anode in 2M NaOH as anolyte at three different temperatures; graph d showing cell voltage vs current density for COR using the IEA including a Cu cathode and a NiFe-B anode in 2M NaOH as anolyte at three different temperatures; and graph e showing EE of carbon products vs current density for COR using the IEA including a Cu cathode and a NiFe-B anode in 2M NaOH as anolyte at three different temperatures.

[0059]

[0060] Figure 13 includes graph a showing cell voltage and FE in H2and carbon products versus time during galvanostatically prolonged COR electrolysis in an IEA at 200 mA / cm2and 35°C; graph b showing FE and Single Pass Conversion Efficiency (SPCE) in certain products versus CO flow rate in an IEA at 200 mA / cm2and 20°C; graph c showing Cathodic Outlet Gas concentration and Ethylene concentration versus CO flow rate in an IEA at 200 mA / cm2and 20°C; and graph d being a diagram showing comparative CO-to- C2+ performance in an IEA as defined herein and in other published works (prior art).

[0060]

[0061] Figure 14 is a graph showing cell voltage versus current density for COR using the IEA including a Cu cathode, an NiFe-B anode in 2M NaOH as anolyte, and one of the nine different porous and hydrophilic materials for the interposer.

[0062] Figure 15 includes graph a showing cell voltage at 200mA cm-2for different interposer thicknesses; graph b showing cell voltage at 200mA cm-2for different interposer materials; and graph c showing cell voltage at 200mA cm-2for different interposer pore size.

[0061]

[0063] Figure 16 includes graph a showing C2+ partial current density versus water permeability for COR using eleven different IEA options; and graph b showing cell voltage versus water permeability for COR using the eleven different IEA options as per graph a.

[0062] DETAILED DESCRIPTION

[0063]

[0064] There is provided an interposed electrode assembly (IEA), namely an electrode assembly including a porous hydrophilic interposer that provides electrical and fluid isolation without suffering resistive losses that are inherent to readily known charge- selective materials. The porous hydrophilic interposer separates electrodes of the IEA and is configured to enhance ion conduction via an electrolyte that fills and hydrates pores of the porous hydrophilic interposer. The IEA also comprises an anodic catalyst to perform an Oxygen Evolution Reaction (OER), for example being an active nickel-iron-boride (NiFe-B) alkaline anodic catalyst. As shown in the experimental results section, an Energy Efficiency (EE) towards C2+ products of 51% was achieved using an IEA as defined herein when performing COR. The IEA sustained stable EE > 50% for over 250 hours and achieved a CO single-pass conversion efficiency of 97% and a C2H4concentration of 54 vol.% (87 wt.%) directly out of a cathodic outlet of the IEA.

[0064]

[0065] The electrode assembly is configured to operate electroreduction of carbon monoxide into carbon products and includes: a cathodic compartment having a cathodic inlet for receiving a gas stream comprising CO and a cathodic outlet for releasing the carbon products including ethylene that are produced according to COR; a cathode comprising a cathodic catalyst and being in fluid communication with the cathodic compartment; an anode comprising an anodic catalyst being positioned away from the cathode so as to form a gap; an anodic compartment being in fluid communication with the anode, the anodic compartment having an anodic inlet for receiving an anolyte and an anodic outlet for releasing oxygen produced according to an Oxygen Evolution Reaction (OER) at the anode; and an interposer comprising a porous and hydrophilic material being positioned in the gap between the anode and the cathode, wherein the hydrophilic material is defined as a material with a contact angle of at most 140 degress as determined according to ISO 19403-6:2017 wherein the pores of the porous and hydrophilic material have an average pore size ranging between 0.30 pm and 10 pm as measured by a porosimeter and the interposer has a thickness between 50 pm and 100 pm as measured by a thickness gauge.

[0065]

[0066] Referring to schematic a of Figure 1 exemplifying COR, the porous and hydrophilic material is used as the interposer (also referred to as the porous hydrophilic interposer) to separate the electrodes of the assembly. A hydrophilic material is defined as a material with a contact angle of at most 140 degrees, as determined according to ISO 19403- 6:2017. With preference, the contact angle of the hydrophilic material is at most 120 degrees, preferably at most 100 degrees, and most preferably at most 90 degrees.

[0066]

[0067] In schematic a of Figure 1 , the interposer is shown facing a catalyst layer of the cathode. Referring to the SEM images a and b of Figure 2 showing the porous structure of the interposer, the interposer is structured to allow ion conduction through its hydrated pores when filled with the electrolyte (anolyte) and avoids gas crossover, thereby preventing for example O2contamination in the product stream.

[0067]

[0068] It should be noted that pores of the porous and hydrophilic material of the IEA are at least partially filled because, under most conditions, all pores would be hydrated with electrolyte but certain operation conditions might lead to pores being only partially filled (e.g. a buildup in pressure for the gas product) so gas could occupy some of the pores.

[0068]

[0069] For example, the porosity of the porous and hydrophilic material is at least 20% as measured by a porosimeter, preferably at least 35%, even more prefereably at least 60%, or most preferably at least 80%. For example, the porosity of the porous and hydrophilic material is ranging between 20% and 99% as measured by a porosimeter, preferably between 25% and 95%, more preferably between 30% and 90%, or even more preferably between 35% and 85%. The porosity is a measure of the void spaces in a material.

[0070] Unlike the AEMs where only a small amount of cation is diffused to the cathode, the interposer is uncharged and allows both cations and anions to migrate to the counter electrodes as schematized in schematic a of Figure 1 .

[0069]

[0071] Table 1 provides characteristics of example materials that can be used as the interposer.

[0070] Material Name Tradename Pore size Porosity Thickness

[0071] Polytetrafluoroethylene PTFE-0.1 Omnipore 0.1 pm 80% 30 pm

[0072] (PTFE) PTFE-b.45- Omnipore 6.45 pm 80% 65 pm thin

[0073] PTFE-0.45- Millipore 0.45 pm 80% 140 pm thick

[0074] PTFE-10 Omnipore 10 pm 80% 85 pm

[0075] Polyvinylidene fluoride PVDF-0.45 Durapore 0.45 pm 70% 125 pm

[0076] (PVDF)

[0077] Polyethersulfone (PESj PES-6.45 Millipore 0.45 pm 60% 130-150 pm

[0078] Express

[0079] Polypropylene (PP) PP-0.45 0.45 pm 40% 190 pm ±

[0080] 50 pm

[0081] PP-Celgard N / A N / A -250 pm

[0082] Zirfon UTP220 Zirfon- 0.45pm 50% 220 pm

[0083] * Composite materials UTP220 of zirconia and polysulfone

[0084] Table 1

[0085]

[0072] A suitable porous and hydrophilic material is available commercially from Merck KGaA as Omnipore PTFE Membrane Filter, 0.45 pm Pore Size, 65 pm thickness (JHWP02500).

[0086]

[0073] The porous and hydrophilic material can have an average pore size of at least 0.05 pm as measured by a porosimeter, preferably at least 0.20 pm, even more preferably at least 0.30 pm, or most preferably at least 0.35 pm; or most preferably at least 0.40 pm; or most preferably at least 0.45 pm. Optionally, the porous and hydrophilic material can have an average pore sizebetween 0.05 and 15 pm, or between 0.1 and 10 pm as measured by a porosimeter, with preference between 0.07 and 9 pm, more preferably between 0.09 and 5 pm, even more preferably between 0.25 pm and 1 pm, most preferably between 0.30 pm and 0.90 pm, and most preferably and 0.45 pm and 0.80 pm.

[0087]

[0074] In the case where the pores are spherical, the pore size refers to the pore diameter.

[0088]

[0075] In some implementations, the porous and hydrophilic material can be one or more selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethersulfone (PES), polypropylene (PP), polyethylene (PE), nylon, polycarbonate (PC), cellulose acetate, cellulose nitrate, mixed cellulose ester (MCE) or other composite materials. With preference, the porous and hydrophilic material is or comprises polytetrafluoroethylene (PTFE) and / or polyvinylidene fluoride (PVDF). More preferably the porous and hydrophilic material is or comprises polytetrafluoroethylene (PTFE).

[0089]

[0076] The material may require surface treatment to become sufficiently hydrophilic as defined by the aforementioned contact angle requirement. The surface treatment may be performed by any suitable methods. For example, a PTFE membrane may be exposed to specific chemical solutions that modify the surface chemistry. Potential chemical solution could be KMnO4+ H2SO4, hot NaOH or chromic acid (CrO3 / H2SO4). Other suitable surface treatment methods may be plasma treatment, UV / ozone activation and surfactant impregnation.

[0090]

[0077] The interposer may have a thickness of at most 120 pm as measured by a thickness gauge, preferably at most 100 pm, more preferably 95 pm, even more preferably at most 90 pm, preferably at most 85 pm, preferably at most 80 pm, preferably at most 75 pm, preferably at most 70 pm

[0091]

[0078] The interposer may have a thickness of at least 5 pm as measured by a thickness gauge, preferably at least 15 pm, more prefereably at least 25 pm, even more prefereably at least 35 pm, even more preferably at least 45 pm, and most prefereably at least 50 pm, or at least 55 pm or at least 60 pm.

[0092]

[0079] In some implementations, the interposer has a thickness between 5 pm and 500 pm as measured by a thickness gauge, optionally, between 15 pm and 450 pm, or between 25 pm and 400 pm, or between 35 pm and 350 pm, or between 45 pm and 300 pm, or between 50 pm and 275 pm, or between 55 pm and 250 pm, or between 60 pm and 200 pm.

[0080] In a prefered embodiment, the interposer has a thickness between 5 pm and 120 pm as measured by a thickness gauge, optionally, between 15 pm and 100 pm, or between 25 pm and 95 pm, or between 35 pm and 90 pm, or between 45 pm and 85 pm, or between 50 pm and 80 pm, or between 55 pm and 75 pm, or between 60 pm and 70 pm as measured by a thickness gauge.

[0093]

[0081] It is noted that other properties can be used to define the interposer. For example, the interposer can be further characterized by a water permeability thereof. In some implementations, the water permeability of the interposer can be of at most 500 mL.min-1.cnr2, preferably of at most 450 mL.min'1.cm'2, more preferably of at most 400 mL.min-1.cnr2. In some implementations, the water permeability of the interposer can be of at least 20 mL.min'1.cm'2, preferably at least 40 mL.min'1.cm'2, or more preferably at least 50 mL.min'1.cm'2. Referring to Figure 16, higher water permeabilities are shown to improve performance of the conversion into ethylene. Water permeability can be measured by determining the water flow rates through the interposer with one side of the interposer being exposed to water and the other side of the interposer being held under vacuum at a pressure of 0.75 bar (0.075 MPa).

[0094]

[0082] Yet another property can be used to define the interposer, this property being a bubble point of the interposer. The bubble point can be defined as the pressure at which gas can pass through the wetted interposer. In some implementations, the bubble point can be between 10 and 100 psi, or between 15 and 95 psi, or between 20 and 90 psi. For example, the bubble point can be measured by a method including wetting the interposer with water, gradually increasing gas pressure on the interposer until a steady stream of bubbles, known as the “first bubble,” emerge from the largest pore in the interposer, and identifying the gas pressure at which the first bubble is observed and which corresponds to the bubble point of the interposer.

[0095]

[0083] In some implementations, the catalyst of the anode of the IEA can be tailored to facilitate the Oxygen Evolution Reaction (OER). The anodic catalyst can thus be a metalbased catalyst comprising nickel, iron, iridium, ruthenium, cobalt, magnesium, or any combination of the previous. With preference, the anodic catalyst is a metal-based catalyst comprising nickel and / or iron.

[0096]

[0084] For example, the anodic catalyst comprises an oxide, a boride, a sulfide, a nitride, and / or a phosphide of the metal-based catalyst.

[0085] For example, the anodic catalyst can be a NiFe catalyst.

[0097]

[0086] For example, the anodic catalyst comprises metal and / or non-metal dopants in the range of 0.1-10 atomic weight % as determined by X-ray photoelectron spectroscopy, optionally the dopant being boron (B).

[0098]

[0087] For example, the anodic catalyst is a NiFe catalyst with metal and / or non-metal dopants in the range of 0.1-10 atomic weight % as determined by X-ray photoelectron spectroscopy. For example, the anodic catalyst is a NiFe catalyst comprises boron (B) and is a NiFe-B catalyst.

[0099]

[0088] The cathodic catalyst can further comprise Cu, Ag, Au, Sn, Pb, Bi, Pd, an alloy thereof, or any combinations thereof. For example, the cathodic catalyst can further comprise Cu, an alloy of Cu with other metal, Cu with metal and non-metal dopants, or Cu modified with polymer additives.

[0100]

[0089] There is also provided the use of a porous and hydrophilic material in an electrolyzer to perform electroreduction of carbon monoxide into carbon products, wherein the porous and hydrophilic material is used as an interposer being positioned between a cathode and an anode of the electrolyzer, wherein the hydrophilic material is defined as a material with a contact angle of at most 140 degress as determined according to ISO 19403-6:2017, the pores of the porous and hydrophilic material have an average pore size between 0.30 pm and 10 pm as measured by a porosimeter and the interposer has a thickness between 50 pm and 100 pm as measured by a thickness gauge.

[0101]

[0090] In some embodiments, the interposer has at least one feature as defined above.

[0102]

[0091] There is further provided a process for electroreducing carbon monoxide into carbon products including operating the IEA as defined herein under tailored conditions. The present techniques including the assembly and related process / operating conditions can both be applied to COR and CO2R. For example, the gas stream can consist of CO. In another example, the gas stream can comprise both CO and CO2. Optionally, the gas stream can be a syngas, therefore further comprising H2. The anolyte can be tailored to the desired pH conditions.

[0103]

[0092] The gas stream comprising CO is supplied to the cathodic inlet of the IEA so as to contact the cathodic COR catalyst, while the anolyte is supplied to the anodic inlet of the anodic compartment of the IEA. A current density is applied to the anode and the cathode to sustain ion conduction through the interposer and generate carbon products in the product stream.

[0104]

[0093] In a preferred implementation, the process for electroreducing carbon monoxide into carbon products comprises: providing an electrode assembly as disclosed above; supplying the gas stream comprising CO to the cathodic inlet of the cathodic compartment of the eleclectrode assembly, wherein, based on the total weight of the input gas stream, the CO is present at a content of between 5 wt.% and 100 wt.% as determined by gas chromotography; supplying the anolyte to the anodic inlet of the anodic compartment of the electrode assembly; applying a current density to the anode and the cathode to sustain ion conduction through the interposer and generate carbon products in the product stream.

[0105]

[0094] As shown in the Experimental Results section, while the design of the IEA as defined herein provides enhanced production of carbon products by avoiding gas crossover and favoring both cation and anion conduction, certain operation conditions can be tuned to further enhance the yielding of carbon products. For example, the process can include adjusting at least one of a temperature of the anolyte (e.g. by heating the IEA), the current density, a nature of the anolyte, or an inlet flow rate of the gas stream.

[0106]

[0095] Based on the total weight of the input gas stream, CO may be present at a content of between 5 wt.% and 100 wt.% as determined by gas chromotography, preferably between 10 wt.% and 95 wt.%, or most preferably between 15 wt.% and 90 wt.%. In some implementations, the CO may be present at a content of at least 5 wt.%, or at least 10 wt.% or at least 15 wt.% based on the total weight of the input gas stream as determined by gas chromotography. In some implementations, the CO may be present at a content of at most 100 wt.%, or at most 95 wt.% or at most 90 wt.% based on the total weight of the input gas stream as determined by gas chromotography.

[0107]

[0096] In some implementations, the current density can be between 50 and 1500 mA.cnr2, or between 150 and 1250 mA. cm-2, optionally between 200 and 1000 mA.cnr2; with preference, the current density is between 50 and 500 mA.cnr2, preferably between 100 and 300 mA.cnr2, more preferably between 150 and 250 mA. cm-2, or most preferably between 180 and 220 mA. cm-2.

[0108]

[0097] In some implementations, the COR can be operated in alkaline conditions such that the anolyte is chosen alkaline. For example, the anolyte can comprise an alkali hydroxide, an alkali carbonate or a combination thereof. For example, the anolyte can be alkaline and the anolyte comprise LiOH, NaOH, KOH, CsOH or any mixtures thereof. Optionally, the anolyte can be NaOH.

[0109]

[0098] It is noted that the nature of the anolyte can also be adapted to all pH conditions including neutral or acidic conditions. For example, a neutral anolyte comprises an alkali sulfate, an alkali bicarbonate or a combination thereof. For example, an acidic anolyte comprises sulfuric acid.

[0110]

[0099] In addition to the nature of the electrolyte (anolyte), it has been shown that the concentration of the electrolyte can have an effect on the yield of carbon products. The anolyte may have a concentration of at most 10M, preferably at most 3M, more preferably of at most 2M, even more preferably at most 2.5M, or most preferably at most 2.2M. The anolyte may have a concentration of at least 0.1 M, preferably at least 1 M, more preferably at least 1.5M, or most preferably at least 1.8M.

[0111]

[0100] In some implementations, the anolyte can have a concentration between 0.1 M and 10M, optionally between 1M and 3M, further optionally between 1.5 M and 2M. Preferably, the anolyte concentration is between 1.5M and 2.5M. Most preferably, the anolyte concentration is between 1.8M and 2.2M.

[0112]

[0101] In some implementations, the process can further include maintaining the temperature of the anolyte between 20°C and 80°C, optionally between 20°C and 50°C. Preferably, the temperature of the anolyte is between 30°C and 70°C, or more preferably between 40°C and 60°C, or most prefereably between 45°C and 55°C. The temperature can be maintained by providing external heat to the IEA, for example by a heating pad.

[0113]

[0102] In some implementations, supplying the gas stream to the cathodic inlet can be performed at a flow rate between 0.05 and 20 seem. cm-2, further optionally between 0.75 and 3 seem. cm-2. Preferably, supplying the gas stream to the cathodic inlet is performed at a flow rate between 0.1 and 1 seem. cm-2,

[0114]

[0103] In some preferred implementations, the gas stream comprises CO and CO2. For example, a CO / CO2ratio can be between 1 :9 and 9:1.

[0104] In some implementations, the gas stream further comprisies H2, namely the gas stream is syngas. For example, a H2 / carbon oxides ratio can be between 1 :1 and 3:1.

[0115]

[0105] In some preferred implementations, said process is catholyte-free.

[0116]

[0106] Alternatively, said process advantageously comprises a catholyte. With preference, said catholyte can be the same as the anolyte defined herein. For example, the catholyte can include LiOH, NaOH, KOH, CsOH or any mixtures thereof.

[0117] REFERENCE METHODS

[0118]

[0107] Hydrophilicity is determined by contact angle as measured according to ISO 19403-6:2017.

[0119]

[0108] Pore size and porosity is determined by a porosimeter using the bubble point test. Bubble point is defined in Reti, A. R. (1977). An assessment of test criteria in evaluating the performance and integrity of sterilizing filters. Bull. Parenteral Drug Assoc., 31, 187- 194. For example, the porosimeter may be the Integritest® 5 Filter Integrity Test Instrument from Merck KGaA. Another method for measuring pore size is mercury porosimetry according to ISO 15901-1 :2016. For example, BELPORE mercury porosimeter MP from Microtrac Inc. is a porosimeter for mercury porosimetry.

[0120]

[0109] Thickness is determined using a thickness gauge

[0121]

[0110] The atomic weight percentage of the dopant in the anodic catalyst was determined using X-ray Photoelectron Spectroscopy (XPS). High-resolution spectra of the dopant and metal core levels were collected and quantified using sensitivity factor-corrected peak areas. The atomic percentage was calculated by normalizing the dopant signal to the total signal of all detected elements.

[0122]

[0111] The content of CO in a gas stream is determined by gas chromatography according to ASTM D2504: Standard Test Method for Noncondensable Gases in C2 and Lighter Hydrocarbon Products by Gas Chromatography (H2, N2, O2, CO).

[0123] EXPERIMENTAL RESULTS

[0124]

[0112] Figures 1 to 16 and the further below examples were obtained using the following experimental methods and materials. Synthesis of the NiFe-B catalyst

[0125]

[0113] The NiFe-B catalyst was synthesized using the following method steps. Firstly, 332.8 mg of NiCI26H2O (99.9%, Sigma-Aldrich) and 227.1 mg of anhydrous FeCI3(>99.99%, Sigma-Aldrich) were dissolved in 2 mL of deionized (DI) water. In a separate vial, 2 mL of 5 M NaBH4(>98%, Sigma-Aldrich) was prepared in DI water. All solutions were then cooled in an ice bath for 10 minutes to prevent uncontrolled hydrolysis to avoid formation of precipitates. A Ni and Fe precursor solution was then added dropwise to the NaBH4solution. The resulting black powder was then washed and centrifuged with water and ethanol three times each before vacuum drying.

[0126] Electrode preparation

[0127] Cathode

[0128]

[0114] Cathodes were prepared by spray coating a Cu ink onto hydrophobic carbon paper. To prepare the Cu ink, 75 mg of Cu nanoparticles (25 nm particle size, Sigma-Aldrich) and 250 pL of Nation solution (5 wt.% in mixture of lower aliphatic alcohols and water, contains 45% water, Sigma-Aldrich) was dispersed in 5 mL of methanol to form an ink mixture. The ink mixture was then sonicated for at least one hour before being spray coated on a 5 x 5 cm2hydrophobic carbon paper (Sigracet 39BB, Fuel Cell Store). The cathode was then air-dried overnight before use. Before the test, the cathode was cut to 1x1 cm2for measurement. For the stability test, a home-made hydrophobic carbon paper was used instead.

[0129]

[0115] The home-made hydrophobic carbon paper was made by blade casting a 0.5 mm layer of mixed PTFE and carbon nanoparticles ink over a 15 x 20 cm2carbon paper gas diffusion layer (AvCarb MGL 190 with 50% wet proof, Fuel Cell Earth). The carbon ink was prepared by mixing 0.4 g of carbon nanoparticles with 35 mL of isopropanol and 4 drops of Triton-X100 (Sigma-Aldrich). The PTFE dispersion was prepared by mixing 4 g of PTFE preparation (60 wt.% dispersion in H2O, Sigma-Aldrich) and 6 g of DI water. Before the blade casting, the carbon ink and the PTFE dispersion were each vortexed for 1 minute, then mixed and stirred for an additional 40 seconds. After blade casting, the resulting substrate was air-dried for 3 hours before being placed in an oven for 3 hours at 280 °C and 1 hour at 340 °C. The resulting substrate was then used as the carbon paper for the stability test.

[0130] Anode

[0116] IrOx anodes were purchased from Magneto Special Anodes (Ir-MMO coated titanium felt), cut to 1 x 1 cm2and used directly. To prepare the NiFe-B anode, 40 mg of the synthesized NiFe-B powder, 133 pL of Nation solution (5 wt.%) were dispersed in 3 mL methanol. The ink mixture was then sonicated for at least one hour. The resulting dispersion was then spray coated onto a 2.5 x 5 cm2IrOx anode.

[0131] Electrolyzer configuration

[0132]

[0117] All experiments were performed in a customized electrolyzer (316L stainless steel cathode plate, and grade 2 titanium anode plate) with an active area of 1 cm2accessed with a serpentine channel. The membrane electrode assembly (MEA) experiments were performed with an AEM (Sustainion X37-50 Grade RT, Dioxide Materials) which was sandwiched between the cathode and the anode. Both the cathode and the anode were protected and surrounded by a 0.01-inch-thick silicone gasket for leak proof. For the interposed systems (IEA), all setup remained the same except the AEM was replaced by an interposer as defined herein that was placed between the cathode and the anode. Unless otherwise specified, 20 seem of CO (High-purity, 2.5 grade, Praxair or Linde) was fed into the cathode while the anode was circulated with an anolyte at a rate of 5 mL / min (e.g., 2M NaOH). Heating pads were used to heat the IEA or MEA electrolyzer for experiments with higher temperatures. The temperature was measured by a thermocouple and was controlled by a PI D controller.

[0133]

[0118] For the interposer, the tested porous and hydrophilic materials were PTFE-0.1 (Omnipore, hydrophilic, 0.1 pm pore size), PTFE-0.45-thin (Omnipore, hydrophilic, 0.45 pm pore size), PTFE-0.45-thick (Millipore, hydrophilic, 0.45 pm pore size), PTFE-10 (Omnipore, hydrophilic, 10 pm pore size), PVDF-0.45 (Durapore, hydrophilic, 0.45 pm pore size), PES-0.45 (Millipore Express, hydrophilic, 0.45 pm pore size), or PP-0.45 (hydrophilic, 0.45 pm pore size) that were purchased from Sigma-Aldrich. The tested porous and hydrophilic material also included PP-Celgard (3419S microporous & 3420 non-woven membrane) that was purchased from Celgard. Zirfon-UTP220 was purchased from Agfa. The detailed properties of all these interposer materials are listed in Table 1. All experiments are performed with PTFE-0.45-thin unless otherwise specified.

[0134]

[0119] Contact angle values were measured for the following tested porous and hydrophilic materials. PTFE-0.45-thin (Omnipore, hydrophilic, 0.45 pm pore size) has a contact angle of 56°; PP-Celgard (3419S microporous & 3420 non-woven membrane) has a contact angle of 95°; Zirfon-UTP220 has a contact angle of 96°. Electrochemical measurement

[0135]

[0120] All electrochemical measurements were carried out using an electrochemical workstation (Autolab PGSTA204) connected to a current booster (Metrohm Autolab, 10A). All voltage was reported directly without iR-compensation. Gas products were collected directly from the electrolyzer cathode outlet using a gas-tight syringe and analyzed with a gas chromatography (PerkinElmer Clarus 590) coupled with a thermal conductivity detector and flame ionization detector. The liquid products were collected separately from the cathode outlet and anolyte, respectively, and quantified using proton nuclear magnetic resonance spectroscopy (1 H+NMR) using water suppression model, with DMSO as the internal standard.

[0136]

[0121] The following equations were used to determine the FE for the gas and liquid products respectively: where x, represents the volume fraction of gas product i, v represents the gas flow rate at the outlet in seem, zpj represents the number of electrons required to produce one molecule of product i, F represents the Faraday constant, P represents atmospheric pressure in Pa, R represents the ideal gas constant, T represents the temperature, and Itotai represents the total current; n, represents the number of moles of the product i, and Q represents the charged passed while the liquid products are being collected.

[0137] Energy efficiency was calculated as follows: n

[0138] EE = yEthermo-ix FEi

[0139] Ecell where Ethermoj represents the thermodynamic potential of product i, and Eceii represents the full cell voltage (non iR-compensated) of the electrolyzer.

[0140]

[0122] Single-pass conversion efficiency was calculated as follows:

[0141] 24.5 X 1O3(^) X 6O (^) SPCE = y

[0142] ^CO, input where zr,i represents number of electrons required to react one molecule of CO for product i, Vco, input represents the CO input flow rate in seem.

[0143] Example 1 - COR performance in a MEA (comparative)

[0144]

[0123] CO reduction experiments were performed using a conventional membrane electrode assembly (MEA) as schematized in scheme b of Figure 4 and operating in alkaline conditions. To establish a baseline, COR was performed using an MEA including a Cu cathode, which microstructure is shown in Figure 3, and an iridium oxide (IrOx) anode separated by an AEM. Referring to graph c of Figure 4, operating in a highly alkaline electrolyte (2M NaOH), the C2H4and C2+ faradaic efficiency (FE) increased with applied current density, exceeding 35% and 86%, respectively at current densities over 200 mA / cm2. A full-cell voltage was measured to be 2.43 V at 200 mA / cm2, corresponding to an EE of 36% for C2+ products and 16% for C2H4as shown in graph d of Figure 4.

[0145] Example 2 - COR performance in a membrane-free electrolyzer (comparative)

[0146]

[0124] Additional experiments were performed in an attempt to further increase the yield towards carbon products relying on the conductivity of the alkaline electrolyte being five times the one of an AEM. A membrane-free setup was used where the electrodes were only separated by a layer of bulk electrolyte. However, this configuration did not yield lower cell voltage, likely due to the considerable electrolyte distance (< 0.5 mm yet still 10x larger than the thickness of the AEM) between the electrodes, necessary to prevent shortcircuiting. Referring to graphs a to c of Figure 5, the cathode gas crossover to the anode compartment was measured to be more than 20% of the total produced C2H4. In addition, O2from the anodic oxygen evolution reaction (OER) was detected in the cathodic gas outlet. It was shown that gas bubbles generated at the electrode surface can rise through the electrolyte due to buoyancy-driven convection, leading to the cross-mixing of the gas streams.

[0147] Example 3 - COR performance in an Interposed Electrode Assembly (IEA) (invention)

[0148]

[0125] Electroreduction experiments were further performed using an IEA as defined herein that can include the material compositions, thicknesses, pore sizes and porosities that are provided in Table 1.

[0149] Interposer

[0126] Referring to Figure 14 and Figure 15, an IEA including Cu as a cathode catalyst and using a 0.2 M concentrated anolyte NaOH was used to perform COR with different porous and hydrophilic materials. Improved full-cell voltages and higher C2+ partial current densities were observed with materials possessing higher porosities and larger pore sizes. This can be due to a higher water permeability offered by porous materials, providing hydrated pathways for fast ion transport. Lowering the interposer thicknesses also resulted in reduced full cell voltage. Among the tested materials, PTFE interposers resulted in the most significant reduction in full cell voltage.

[0150]

[0127] Regarding the product distribution resulting from COR in the IEA system, and compared to the AEM case of Example 1 , the IEA enabled a higher C2+ FE of 95% and was able to suppress the H2FE to 5% at current densities higher than 200 mA / cm2as shown in graph c of Figure 6 using NaOH as anolyte. This improvement in performance is associated to a higher availability of cations at the cathode, especially as cations are deemed essential for the carbon-carbon coupling process. These results suggest that the IEA can be well-suited for improving performance of COR.

[0151] Anolyte

[0152]

[0128] Different electrolytes were further tested to evaluate the cation effect on the performance in the IEA. Referring to graphs b to d of Figure 6, increased production of liquid oxygenates was observed with Li+<Na+<K+. While Li+allowed higher C2H4FE especially at lower current densities, it also resulted in more H2production. For example, Na+can be selected as candidate for the cation of the anolyte.

[0153] Anolyte concentration

[0154]

[0129] Different anolyte concentrations were also tested for a same cation (e.g., Na+). Referring to graphs b to d of Figure 7, a concentration of 2 M NaOH allowed for the highest C2+FE under a wide window of current density while providing satisfactory cell voltage (see graph a of Figure 7).

[0155]

[0130] Referring to graph b of Figure 1 , operating at a current density of 200 mA / cm2, the full-cell voltage in the IEA with 2 M NaOH was found to be a reduced full-cell voltage of - 2.28 V in comparison to the voltage obtained in the same conditions with an MEA including an AEM (a 150 mV reduction compared to the AEM case).

[0156]

[0131] Referring to graph c of Figure 1 , the full-cell voltage together with the better FE corresponds to an improved C2H4EE of 19% and C2+EE of 41%. Referring to graph d f Figure 1 , the anode crossover gas composition was evaluated to detect any gas product and / or reactant crossover from the cathode. The IEA is shown to have similar product and / or reactant crossover performance compared to the AEM except for H2gas. The higher H2gas crossover can be due to the faster diffusion through water compared to other gases.

[0157] Anodic catalyst to facilitate OER

[0158]

[0132] The effect of the catalyst was further studied by testing two different COR catalysts namely IrOx and NiFe-B catalysts. The catalyst yielding to the lowest cell voltage can be considered as a satisfactory candidate. Earth-abundant Ni-based catalysts had been reported to outperform Ir-based catalysts for alkaline OER. A NiFe-B catalyst, as shown in Figures 8 and 9, was tested in comparison to commercial IrOx catalyst to sustain the anodic OER reaction in alkaline conditions provided by the 2M NaOH anolyte. The distribution of the various atoms in the NiFe-B catalyst is shown in Figure 9 based on TEM images with elemental mapping (with the exception of the first TEM image in the left above corner that is taken without elemental mapping). The TEM images show that the Ni, Fe and B are evenly distributed (and the approximate amount) in the catalyst. Referring to Figure 10, X-ray photoelectron spectroscopy (XPS) shows Ni, Fe, and B elemental signals, confirming successfull incorporation of boron into the NiFe matrix. Comparing graphs a and b of Figure 11 , it was found that the product distribution remained similar with the different anode catalysts. However, referring to graphs a and b of Figure 12, operating at 200 mA / cm2, the NiFe-B catalyst enabled a full-cell voltage of 2.15 V - a fully 140 mV reduction compared to the IrOx case and an increased C2H4EE of 20% and C2+EE of 43%.

[0159] Temperature

[0160]

[0133] Another operation condition, i.e. temperature, was varied to test its effects on COR performance. Referring to graphs c to e of Figure 12, it has been found that the C2H4EE can be increased towards 50% by increasing the temperature (e.g., by applying external heat to the IEA). Elevated temperatures accelerate kinetics of both the cathodic COR and anodic OER and increases the conductivity of electrolyte. Referring to graph c of Figure 12, at higher temperatures, a reduction in H2FE was observed and coincided with a slight improvement in C2H4FE and C2+FE to over 55% and 96%, respectively. The peak C2H4FE and C2+FE shifted towards lower current densities, that can be attributed to the decreased CO solubility and a more optimal CO coverage on the cathode surface. However, further increasing the current densities above 500 mA / cm2at 50 °C resulted in an increase in H2production which indicates that it may have surpassed the most optimal CO coverage and the reaction is mass transport-limited at higher reaction rates. Referring to graphs d and 2 of Figure 12, reductions in full-cell voltage were measured with increasing temperatures, and a full-cell voltage of -1.95 V and a C2+ EE over 50% were found at 200 mA / cm2and 50°C, being the highest EE among all CO2R / COR as shown in graph a of Figure 4.

[0161] Stability

[0162]

[0134] Referring to graph a of Figure 13, to demonstrate stability of the IEA, galvanostatically prolonged electrolysis was performed at 200 mA / cm2and either 35 °C or 50°C. At 35°C, it was found that the system maintains a C2+EE ~50% over 10 days (240 hours) with the changes in FE and voltage limited to less than 5%. At 50°C, the system remained stable for 250 operating hours, with EE decaying by less than 10% by the end of the stability run. Referring to graph d of Figure 13, the present experimental results correspond to the longest operation found for CO2 / CO-to-C2+electrolysis operating at industrially relevant current densities. Referring to graph b of Figure 13, the CO singlepass conversion efficiency (SPCE) was also found to increase by constraining the CO flow rate to the electrolyzer. High CO SPCE can lead to high product concentration which in turn lowers the energy that is required for downstream separation. Referring to graphs b and c of Figure 13, operating at 200 mA / cm2and 20°C at a flow rate of 0.75 sccm / cm2, a slight increase in the H2FE with the C2H4FE and C2+FE reaching 56% and 90%, respectively, were observed and correspond to a SPEC of 97% towards C2+products. The near-full conversion also yielded a high C2H4concentration. More particularly, as shown in graph c of Figure 13, the C2H4concentration at the cathodic outlet was measured to be 54 vol% (or 86 wt%). In comparison with prior COR reports, the IEA exhibited superior performance in FE, EE, SPCE, and stability towards C2+products (see graph d of Figure 13 with prior works referring to Ripatti, D. S., Veltman, T. R. & Kanan, M. W. Carbon Monoxide Gas Diffusion Electrolysis that Produces Concentrated C2 Products with High Single-Pass Conversion. Joule 3, 240-256 (2019); Ozden, A. et al. Cascade CO2 electroreduction enables efficient carbonate-free production of ethylene. Joule 5, 706-719 (2021); and Ozden, A. et al. Energy- and carbon-efficient CO2 / CO electrolysis to multicarbon products via asymmetric ion migration-adsorption. Nat. Energy 2023 82 8, 179-190 (2023)).

[0135] In the above description, an embodiment is an example or implementation of the invention. The various appearances of “one embodiment,” “an embodiment” or “some implementations” do not necessarily all refer to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

Claims

CLAIMS1 . An electrode assembly for operating electroreduction of carbon monoxide into carbon products, the electrode assembly comprising: a cathodic compartment having a cathodic inlet for receiving a gas stream comprising CO and a cathodic outlet for releasing the carbon products including ethylene that are produced according to COR; a cathode comprising a cathodic catalyst and being in fluid communication with the cathodic compartment; an anode comprising an anodic catalyst being positioned away from the cathode so as to form a gap; an anodic compartment being in fluid communication with the anode, the anodic compartment having an anodic inlet for receiving an anolyte and an anodic outlet for releasing oxygen produced according to an Oxygen Evolution Reaction (OER) at the anode; and an interposer comprising a porous and hydrophilic material being positioned in the gap between the anode and the cathode, wherein the hydrophilic material is defined as a material with a contact angle of at most 140 degress as determined according to ISO 19403-6:2017 wherein the pores of the porous and hydrophilic material have an average pore size ranging between 0.30 pm and 10 pm as measured by a porosimeter and the interposer has a thickness between 50 pm and 100 pm as measured by a thickness gauge.

2. The assembly of claim 1 , wherein the porous and hydrophilic material has a porosity between 20 % and 99 % as measured by a porosimeter.

3. The assembly of claim 1 or 2, wherein the pores of the porous and hydrophilic material have an average pore size ranging between 0.45 pm and 10 pm as measured by a porosimeter.

4. The assembly of any one of claims 1 to 3, wherein the interposer has a thickness between 55 pm and 80 pm as measured by a thickness gauge.

5. The assembly of any one of claims 1 to 4, wherein the porous and hydrophilic material is one or more selected from polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone, polypropylene, polyethylene, nylon, polycarbonate, cellulose acetate, cellulose nitrate, mixed cellulose ester; with preference, the porous and hydrophilic material is polytetrafluoroethylene.

6. The assembly of any one of claims 1 to 5, wherein the anodic catalyst is a metal-based catalyst comprising nickel, iron, iridium, ruthenium, cobalt, magnesium, or any combinations thereof.

7. The assembly of claim 6, wherein the anodic catalyst comprises an oxide, a boride, a sulfide, a nitride, and / or a phosphide of the metal-based catalyst.

8. The assembly of claim 6 or 7, wherein the anodic catalyst is a NiFe catalyst.

9. The assembly of any one of claims 6 to 8, wheren the anodic catalyst comprises metal and / or non-metal dopants in the range of 0.1-10 atomic weight % as determined by X- ray photoelectron spectroscopy, optionally the dopant being boron (B).

10. The assembly of any one of claims 1 to 9, wherein the cathodic catalyst comprises Cu, Ag, Au, Sn, Pb, Bi, Pd, an alloy thereof, or any combinations thereof.11 . Use of a porous and hydrophilic material in an electrolyzer to perform electroreduction of carbon monoxide into carbon products, wherein the porous and hydrophilic material is used as an interposer being positioned between a cathode and an anode of the electrolyzer, wherein the hydrophilic material is defined as a material with a contact angle of at most 140 degress as determined according to ISO 19403-6:2017, the pores of the porous and hydrophilic material have an average pore size between 0.30 pm and 10 pm as measured by a porosimeter and the interposer has a thickness between 50 pm and 100 pm as measured by a thickness gauge.

12. The use of claim 11 , wherein the interposer has at least one feature as defined in any one of claims 2 to 10.

13. A process for electroreducing carbon monoxide into carbon products, the process comprising: providing an electrode assembly as defined in any one of claims 1 to 10; supplying the gas stream comprising CO to the cathodic inlet of the cathodic compartment of the eleclectrode assembly, wherein, based on the total weight of theinput gas stream, the CO is present at a content of between 5 wt.% and 100 wt.% as determined by gas chromotography; supplying the anolyte to the anodic inlet of the anodic compartment of the electrode assembly; applying a current density to the anode and the cathode to sustain ion conduction through the interposer and generate carbon products in the product stream.

14. The process of claim 13, wherein the current density is between 50 and 1500 mA.cnrr 2; with preference, the current density is between 100 and 300 mA.cnr2.

15. The process of claim 13 or 14, wherein the anolyte is alkaline and the anolyte comprises LiOH, NaOH, KOH, CsOH or any mixtures thereof.

16. The process of claim 13 or 14, wherein the anolyte is neutral and the anolyte comprises an alkali sulfate, an alkali bicarbonate or a combination thereof.

17. The process of any one of claims 13 to 16, wherein the anolyte has a concentration between 0.1M and 10M, and optionally between 1M and 3M; with preference, the anolyte concentration is between 1.5M and 2.5M.

18. The process of any one of claims 13 to 17, further comprises the step of heating the electrode assembly to maintain the anolyte at a temperature between 20°C and 80°C; with preference, the temperature of the anolyte is between 40°C and 60°C.

19. The process of any one of claims 13 to 18, wherein the gas stream is supplied to the cathodic inlet with a flow rate between 0.05 and 20 seem. cm-2, preferably between 0.1 and 1 seem. cm-2.

20. The process of any one of claims 13 to 19, the gas stream comprises CO and CO2.

21. The process of claim 20, wherein a CO / CO2ratio is between 1 :9 and 9:1.

22. The process of claim 20 or 21 , wherein the gas stream further comprises H2.

23. The process of claim 22, wherein a H2 / carbon oxides ratio is between 1 :1 and 3:1.

24. The process of any one of claims 13 to 23, wherein said process is catholyte-free.

25. The process of any one of claims 13 to 23, wherein said process comprises a catholyte, with preference, said catholyte LiOH, NaOH, KOH, CsOH or any mixtures thereof.

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