Classifications

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  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/01—Products
  • C25B3/03—Acyclic or carbocyclic hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
  • C25B11/077—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
  • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
  • C25B11/031—Porous electrodes
  • C25B11/032—Gas diffusion electrodes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/097—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds comprising two or more noble metals or noble metal alloys
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/01—Products
  • C25B3/07—Oxygen containing compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction
  • C25B3/26—Reduction of carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/13—Single electrolytic cells with circulation of an electrolyte
  • C25B9/15—Flow-through cells
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
  • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded

Definitions

• the present disclosure relates to catalysts and catalytic methods for electrochemical reduction of one or more carbon oxides (such as carbon monoxide and/or carbon dioxide) into alcohols such as n-propanol and/or ethanol.
• the present disclosure is about a gas diffusion electrode (GDE) suitable for carbon oxide electrolysis, a gas-fed flow cell comprising such GDE as well as a method for producing such GDE and a process using such GDE.
• GDE gas diffusion electrode
• Electrochemical reduction of CO provides an opportunity to produce fuels and chemicals in a carbon-neutral manner, assuming that CO is produced from CO2 which can be captured from the atmosphere or at least can be captured from the industrial emission before being released into the atmosphere. To do so requires efficient, selective, and stable catalysts. Copper-based materials are promising electrocatalysts for CO reduction.
• N-propanol and ethanol are of high- value interest and have not yet been produced efficiently via electrochemical CO reduction.
• the CusN-derived Cu electrocatalyst produces virtually no CH4, very little CO, and exhibits a faradaic efficiency of 68% in C2+ products (C2H4, C2H5OH, and C3H7OH) at a current density of -18.5 mA cm -2 and a cathode potential of -1.0 V versus the reversible hydrogen electrode (RHE).
• the catalyst produces more oxygenated products than hydrocarbons. It was shown that surface roughness is a good descriptor of catalytic performance. The roughest surface reached 98% CO utilization efficiency for C2+ product formation from CO2 reduction and the ratio of oxygenated to hydrocarbon products correlates with the degree of surface roughness.
• WO2019098474 relates to an electrochemical cell to be used when carbon dioxide is decomposed and reduced to a useful conversion product; and a catalyst to be used in an electrode for an anode within the cell.
• a C2+ compound can be selectively generated and a C2+ hydrocarbon can be stably generated by providing, as a catalyst for a reduction reaction of a material, a catalyst comprising a metal compound containing a metal ion having a standard reduction potential lower than the standard reduction potential when a monovalent or divalent copper cation within copper oxide is reduced to copper or a monovalent copper cation, and thus a catalyst having durability can be provided.
• Cu copper
• CO2RR carbon dioxide electrochemical reduction reaction
• Cu-based/CxNy catalysts were fabricated by facile pyrolysis of CuNCN in sealed quartz tubes. It is found that CuNCN pyrolyzed at 300 °C (CuNCN-300) exhibits a high C2H4 Faradaic efficiency of 48.5% at 500 mA cm-2.
• the multi-metallic catalyst according to the present disclosure comprising copper nitride-metal.
• the disclosure provides a catalyst suitable for electrochemical reduction reaction of one or more carbon oxides (such as carbon monoxide reduction (COR) reactions and/or carbon dioxide (CO2R) reduction), remarkable in that it comprises a nitride- doped multi-metallic material comprising a primary metal being copper and one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, iridium, osmium, and any mixture thereof; and in that the nitride-doped multi-metallic material comprises, as determined by XRD, copper, copper nitride and copper-Me alloy wherein Me is one of the secondary metals.
• COR carbon monoxide reduction
• CO2R carbon dioxide
• the catalysts being nitride-doped multi-metallic material comprising copper as the primary metal and at least one secondary metal, allow good selectivity into alcohol production such as n-propanol and/or ethanol.
• the one or more secondary metals are selected from silver, gold, and any mixture thereof.
• the nitride-doped multi-metallic material comprises from 0.5 to 10.0 mol% of the one or more secondary metals based on the total molar content of copper and one or more secondary metals as determined by XPS; preferably from 0.6 to 9.0 mol.% or from 1.0 to 10.0 mol%.
• the nitride-doped multi-metallic material comprises only one secondary metal.
• the nitride-doped multi-metallic material is a nitride-doped bimetallic material and comprises from 2.0 to 8.0 mol% of the secondary metal based on the total molar content of copper and the metal as determined by XPS; preferably from 3.0 to 7.0 mol.%.
• the nitride-doped multi-metallic material comprises two or more secondary metals, and comprises from 0.5 to 8.0 mol% of the secondary metals based on the total molar content of copper and the two or more secondary metals; with preference 1 .0 to 6.0 mol%.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least one of the secondary metals is silver or gold; preferably wherein at least two secondary metals are silver and gold.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least two secondary metals Me1 and Me2 are present in a ratio Me1/Me2 ranging from 1 to 15; preferably from 1 to 10; more preferably, from 1 to 4.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least two secondary metals Me1 and Me2 differ by their reduction potential wherein Me1 has a reduction potential greater than Me2, and Me1 and Me2 are present in a ratio Me1/Me2 greater than 1 ; preferably greater than 2; more preferably greater than 3.
• the nitride-doped multi-metallic material shows Cu (111) and Cu (200) facets as determined by XRD.
• the nitride-doped multi-metallic material is in the form of rode-shape particles and/or the particles have an average diameter ranging from 20 nm to 500 nm as measured by transmission electron microscopy; preferably, ranging from 50 nm to 400 nm or from 80 to 350 nm.
• the disclosure provides a method to produce a catalyst according to the first aspect.
• the method comprising a) providing copper particles; b) adding of one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, and any mixture thereof, wherein said step of addition comprises a step (b1) of galvanic exchange reaction or a step (b2) of electrodeposition or both steps (b1) of galvanic exchange reaction and step (b2) of electrodeposition, to obtain a multi-metallic material comprising copper as primary metal and one or more secondary metals; c) nitridation of the multi-metallic material obtained in step b) to obtain a nitride-doped multi- metallic material.
• the step b) is a step (b1) of galvanic exchange reaction and is performed by stirring the copper particles in an aqueous solution comprising one or more selected from chloroplatinic acid hexahydrate, ruthenium acetylacetonate, iridium acetylacetonate, osmium acetylacetonate, rhodium acetylacetonate, palladium acetylacetonate, palladium nitrate, palladium chloride, gold chloride trihydrate, silver nitrate, and any mixture thereof.
• the aqueous solution comprises gold chloride trihydrate, silver nitrate, and any mixture thereof.
• the nitride-doped multi-metallic material comprises two or more secondary metals
• the step b) is a step (b1) of galvanic exchange reaction comprising successive sub-steps of galvanic exchange reaction; with preference, the two or more secondary metals differ by their reduction potential and the successive sub-steps of galvanic exchange reaction are performed starting by the secondary metal having the highest reduction potential.
• the nitridation step comprises a calcination sub-step followed by a copper nitride synthesis sub-step; preferably the copper nitride synthesis sub-step is performed at a temperature ranging from 150 to 190°C and for a time ranging from 5 to 30 hours.
• the copper particles have an average diameter ranging from 5 nm to 200 nm as measured by transmission electron microscopy; preferably, the copper particles are nanoparticles and have an average diameter ranging from 5 nm to 100 nm as measured by transmission electron microscopy.
• the disclosure provides a gas diffusion electrode suitable for the electrochemical reduction of one or morecarbon oxides, said gas diffusion electrode having a gas diffusion layer, the gas diffusion electrode further comprising an ink deposited on the gas diffusion layer; wherein the ink comprises an ion-conducting polymer, said gas diffusion electrode is remarkable in that the ink further comprises the catalyst as defined according to the first aspect or produced according to the second aspect.
• the gas diffusion layer is a hydrophobic porous support.
• said hydrophobic porous support shows a pore size ranging from 400 nm to 500 nm as determined by scanning electron microscopy preferably, from 420 nm to 580 nm or from 440 nm to 560 nm.
• the gas diffusion layer is a hydrophobic, porous and chemically inert support; with preference, the gas diffusion layer is not soluble in KOH.
• the gas diffusion layer is or comprises polytetrafluoroethylene.
• the gas diffusion layer has a thickness ranging from 50 pm to 150 pm as measured by scanning electron microscopy, preferably from 60 pm to 120 pm more preferably from 70 pm to 100 pm.
• One or more of the following features advantageously define the ion-conducting polymer of the gas diffusion electrode of the disclosure:
• the ion-conducting polymer comprises an ionomer.
• the ion-conducting polymer is or comprises an ionomer with a tetrafluoroethylene backbone group (-CF2-CF2-).
• the ion-conducting polymer is or comprises a perfluorinated sulfonic acid, such as National®.
• the ion-conducting polymer is or comprises tetrafluoroethylene-perfluoro(3- hydrophobioxa-4-pentenesulfonic acid) copolymer, such as Aquivion®.
• the ink layer has a thickness ranging from 2 pm to 20 pm as measured by scanning electron microscopy, preferably from 5 pm to 15 pm.
• the disclosure provides a method for producing the gas diffusion electrode suitable for the electrochemical reduction of one or more carbon oxides as defined according to the second aspect, said method is remarkable in that it comprises the following steps: providing nitride-doped multi-metallic particles; adding an ion-conducting polymer and obtaining a dispersion by dispersing the nitride- doped multi-metallic particles into a solvent selected from water and/or an organic solvent; to obtain an ink providing a gas-diffusion layer and depositing said ink onto said gas-diffusion layer to obtain the gas diffusion electrode.
• the disclosure provides a gas diffusion electrode obtained by the method according to the third aspect.
• the disclosure provides a gas-fed flow cell suitable for the electrochemical reduction of one or more carbon oxides, said gas-fed flow cell comprising a gas chamber, a catholyte chamber and an anolyte chamber, wherein said gas chamber is separated from the catholyte chamber by a gas diffusion electrode, said gas diffusion electrode having a gas diffusion layer being comprised within said gas chamber, wherein said catholyte chamber and said anolyte chamber are separated by an anion exchange membrane, and wherein said catholyte chamber and said anolyte chamber comprise respectively a cathode and an anode, said gas-fed flow cell is remarkable in that the gas diffusion electrode is as defined according to the second aspect and/or with the fourth aspect.
• the disclosure provides a process for electrochemically reducing one or more carbon oxides into one or more hydrocarbons and alcohols characterized in that it comprises the following steps:
• the input flow comprising one or more carbon oxides selected from carbon monoxide, carbon dioxide, and a mixture of carbon monoxide and carbon dioxide ;
• the electrolyser further comprises a first interface in between the gas diffusion cathode and the ion-exchange membrane, wherein the first interface comprises a cathode comprising the catalyst as defined according to the first aspect or prepared according to the method according to the second aspect;
• the mixture of carbon monoxide and carbon dioxide comprises at least 20 mol.% based on the total molar content of the mixture; preferably at least 40 mol.%; more preferably at least 60 mol.%, even more preferably at least 80 mol.% and most preferably at least 90 mol.% or at least 95 mol.%.
• the disclosure provides for the use of a catalyst for electrochemical carbon monoxide reduction (COR) reactions to produce n-propanol and/or ethanol the use being remarkable in that the catalyst is according to the first aspect.
• the disclosure provides for the use of a catalyst for electrochemical carbon dioxide reduction (CO2R) reactions to produce n-propanol and/or ethanol the use being remarkable in that the catalyst is according to the first aspect.
• CO2R electrochemical carbon dioxide reduction
• Figure 2 XRD patterns of CusN/Ag(5%), CusN and Cu/Ag(5%) with the references.
• the black circles indicate CU2O.
• Figure 3 SEM images of CusN/Ag(5%), CU3N, Cu and Cu/Ag(5%).
• Figure 4 XRD patterns of CusN/Ag(5%) samples synthesized with different nitridation times (10-60 h). Black circles: Cu, white circles: CU3N and black squares: Ag.
• Figure 5 XRD patterns of CusN/Ag samples synthesized with 20 h of nitridation time and different contents of Ag (2-8 %). Black circles: Cu, white circles: CU3N and black squares: Ag.
• Figure 6 Activity for electrochemical CO reduction of Cu, CU3N, CusN/Ag(5%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-200 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• the scale bar of FEn-propanol of CusN/Ag at 150 mA. cm -2 was taken from the results of three independent experiments.
• Figure 7 Activity for electrochemical CO reduction of CusN/Ag(5%) catalysts synthesized with different nitridation times of 10 to 60 h.
• Anode Ni foam.
• Anolyte KOH
• Figure 8 Activity for electrochemical CO reduction of CusN/Ag(5%), CusN/Au(5%) and Cu3N/Pd(5%) catalysts synthesized with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-200 mA. cm -2 for 0.5 h.
• CO flow 10 ml. min -1 .
• Figure 9 Activity for electrochemical CO reduction of CusN/Ag catalysts with different contents of Ag (2-8%), synthesized with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 75-200 mA.cm-
• Figure 10 Activity for electrochemical CO reduction of CusN/Ag(5%) with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied currents 100-200 mA.cm -2 for 0.5 h.
• CO flow 10 ml. min -1 .
• Figure 11 Activity for electrochemical CO reduction of CusN/Ag(5%) with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 0.1-3 M, 60 mL.
• Catholyte KOH 0.1-3 M, 40 mL.
• Applied currents 100-200 mA.cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 12 XRD patterns of CusN/Ag(5%) and CU3N synthesized with nitridation time of 20 h, after 30 minutes of CORR electrolysis.
• Figure 13 XRD patterns of Cu 3 N/Ag(5%) synthesized with nitridation time of 20 h, after 30 minutes of CORR electrolysis and three scans of LSV.
• Figure 14 Activity for electrochemical CO2 reduction of Cu 3 N/Ag(5%) with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied currents 100-200 mA. cm -2 for 0.5 h.
• Figure 15 XPS survey spectrum and high resolution measurement of Nils, Cu2p and Ag3d in Cu 3 N/Ag(5%) sample.
• Figure 16 Activity for electrochemical CO reduction of Cu3N/Au(2%)Ag(0.1 %), Cu 3 N/Au(2%)Ag(0.3%), Cu 3 N/Au(2%)Ag(0.5%) and Cu 3 N/Au(2%)Ag(1 %) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 17 Activity for electrochemical CO reduction of Cu 3 N/Au(0.3%)Ag(0.3%), Cu 3 N/Au(1%)Ag(0.3%), Cu 3 N/Au(2%)Ag(0.3%) and Cu 3 N/Au(3%)Ag(0.3%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 18 Activity for electrochemical CO reduction of Cu 3 N/Au(1%)Ag(0.3%) catalysts at KOH concentrations of 0.1 , 0.5, 1 , 1.5 and 3 M with applied current of 100, 125 and 150 mA. cm -2 , respectively, for 0.5 h. Nitridation time of 20 h. Anode: Ni foam. Anolyte: KOH 60 mL. Catholyte: KOH 40 mL. CO flow: 10 ml.min-1. Error bars were made for ethanol and propanol, C2+ liquids alcohols is shown as the highest value obtained.
• Figure 19 Activity for electrochemical CO reduction of Cu 3 N/Au(1%)Ag(0.3%), CU 3 N/AU(5%) and Cu 3 N/Ag(5%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 20 the ratio between multicarbon alcohol products and ethylene from electrochemical CO reduction of Cu 3 N/Au(0.3%)Ag(0.3%), Cu 3 N/Au(1%)Ag(0.3%), Cu 3 N/Au(2%)Ag(0.3%), Cu 3 N/Au(3%)Ag(0.3%), Cu 3 N/Au(5%), and Cu 3 N/Ag(5%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 21 Activity for electrochemical CO reduction of Cu 3 N/Au(0.3%), Cu 3 N/Au(1%), CU 3 N/AU(2%), and Cu 3 N/Au(3%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 22 Activity for electrochemical CO reduction of Cu 3 N/Ag(0.3%), Cu 3 N/Ag(2%), Cu 3 N/Ag(5%), and Cu 3 N/Ag(8%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 23 Activity for electrochemical CO reduction of Cu3N/Au(1%)Ag(0.3%), and Cu3N/Ag(0.3%) catalysts with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 0.5 h.
• CO flow 10 ml.min-1.
• Figure 24 Activity for electrochemical CO reduction of Cu3N/Au(1%)Ag(0.3%) catalyst with nitridation time of 20 h.
• Anode Ni foam.
• Anolyte KOH 1 M, 60 mL.
• Catholyte KOH 1 M, 40 mL.
• Applied current 100-150 mA. cm -2 for 30 to 800 minutes.
• CO flow 10 ml.min-1.
• Figure 25 XRD patterns of Cu3N/Au(1%)Ag(0.3%) synthesized with nitridation time of 20 h, before and during 30 minutes of CORR electrolysis.
• Figure 1 illustrates the gas-fed flow cell 1 of the present disclosure.
• Said gas-fed flow cell comprises a gas diffusion electrode suitable for electrochemical carbon oxide reduction reactions, such as carbon monoxide reduction reactions and/or for carbon dioxide reduction reactions.
• the following description first describes the catalyst used in the gas diffusion electrode.
• the disclosure provides for a catalyst suitable for electrochemical carbon oxide reduction reactions (such as carbon monoxide reduction reactions and/or for carbon dioxide reduction reactions), remarkable in that it comprises a nitride-doped multi-metallic material comprising a primary metal being copper and one or more secondary metals selected from noble metals wherein the noble metals include silver; and in that the nitride-doped multi-metallic material comprises, as determined by XRD, copper, copper nitride and copper-Me alloy wherein Me is one of the secondary metals.
• the one or more secondary metals are selected from silver, gold, platinum, palladium, ruthenium, and any mixture thereof; preferably, the one or more secondary metals are selected from silver, gold, palladium, and any mixture thereof; more preferably, the one or more secondary metals are selected from silver, gold, and any mixture thereof.
• the catalyst be prepared by nitridation of a multi-metallic material.
• the first step is to prepare such multi-metallic material. This can be done by the addition of one or more secondary metals to copper particles.
• the copper particles have an average diameter ranging from 5 nm to 200 nm as measured by transmission electron microscopy; preferably, from 10 nm to 180 nm; more preferably, from 15 nm to 150 nm; even more preferably from 20 nm to 120 nm.
• the copper particles are nanoparticles and have an average diameter ranging from 5 nm to 100 nm as measured by transmission electron microscopy; preferably, from 10 nm to 80 nm; more preferably, from 15 nm to 60 nm; even more preferably from 20 nm to 50 nm or from 5 nm to 40 nm.
• the step of addition comprises a step (b1) of galvanic exchange reaction or a step (b2) of electrodeposition or both steps (b1) of galvanic exchange reaction and step (b2) of electrodeposition; preferably the step of addition comprises a step (b1) of galvanic exchange reaction or both steps (b1) of galvanic exchange reaction and step (b2) of electrodeposition; even more preferably, the step of addition comprises a step (b1) of galvanic exchange reaction.
• the step (b1) using a galvanic exchange reaction the copper particles are doped with one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, iridium, osmium, and any mixture thereof; preferably, the one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, and any mixture thereof; for example, the one or more secondary metals are selected from silver and/or gold.
• the step (b1) is performed by stirring the copper particles in an aqueous solution comprising one or more noble metal ions precursors.
• the step (b1) is performed by stirring the copper particles in an aqueous solution comprising one or more selected from chloroplatinic acid hexahydrate (F ⁇ PtCle-etW); ruthenium acetylacetonate (Ru(acac)s); iridium acetylacetonate (Ir(acac)s), osmium acetylacetonate (Os(acac)s), rhodium acetylacetonate (Rh(acac)s), palladium acetylacetonate (Pd(acac)3), palladium nitrate (Pd(NOs)2), palladium chloride (F ⁇ PdCU), gold chloride trihydrate (HAuC SFW), silver nitrate (AgNCh), and any mixture thereof.
• the one or more secondary metal concentration in the step (b1) was performed with a content of from 0.5 to 10.0 mol% of the one or more secondary metals based on the molar content of copper; preferably from 0.6 to 9.0 mol%; more preferably from 0.8 to 8.0 mol%; even more preferably from 1.0 to 7.5 mol%; most preferably from 1.1 to 7.0 mol%; even most preferably from 1 .2 to 6.5 mol% or from 1 .3 to 6.0 mol%.
• the one or more secondary metal concentration in the step (b1) was performed with a content of at least 0.5 mol% of the one or more secondary metals based on the molar content of copper; preferably at least 0.6 mol%; more preferably at least 0.8 mol%; even more preferably at least 1.0 mol%; most preferably at least 1.1 mol%; even most preferably at least 1 .2 mol% or at least 1.3 mol%.
• the one or more secondary metal concentration in the step (b1) was performed with a content of at most 10.0 mol% of the one or more secondary metals based on the molar content of copper; preferably at most 9.0 mol%; more preferably at most 8.0 mol%; even more preferably at most 7.5 mol%; most preferably at most 7.0 mol%; even most preferably at most 6.5 mol% or at most 6.0 mol%.
• the nitride-doped multi-metallic material is a nitride-doped bimetallic material and only one secondary metal is used as dopant.
• the secondary metal concentration in the step (b1) was performed with a content of from 1.0 to 10.0 mol% of the secondary metal based on the molar content of copper; preferably from 1.5 to 9.0 mol%; more preferably from 2.0 to 8.0 mol%; even more preferably from 2.5 to 7.5 mol%; most preferably from 3.0 to 7.0 mol%; even most preferably from 3.5 to 6.5 mol% or from 4.0 to 6.0 mol%.
• the nitride-doped multi-metallic material comprises two or more secondary metals
• the step b) is a step (b1) of galvanic exchange reaction comprising successive sub-steps of galvanic exchange reaction.
• the secondary metals are added successively, one after the other, in separate sub-steps of galvanic exchange reaction.
• the two or more secondary metals differ by their reduction potential, and the successive sub-steps of galvanic exchange reaction are performed starting with the secondary metal having the highest reduction potential.
• Such galvanic exchange reaction sub-steps are separated or followed by an equal number of washing sub-step with H2O and ethanol.
• the nitride-doped multi-metallic material comprises two or more secondary metals, and each of the two or more secondary metal concentrations in the sub-step (b1) was performed with a content of 0.5 to 10.0 mol% or 0.5 to 8.0 mol% of the one or more secondary metals based on the molar content of copper; preferably from 0.6 to 9.0 mol%; more preferably from 0.8 to 8.0 mol%; even more preferably from 1.0 to 7.5 mol%; most preferably from 1.1 to 7.0 mol%; even most preferably from 1.2 to 6.5 mol% or from 1.3 to 6.0 mol% or from 1 .0 to 6.0 mol%.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least one of the secondary metals is silver or gold; preferably wherein at least two secondary metals are silver and gold.
• the examples surprising results are obtained with multi-metallic material comprising copper, silver and gold (i.e. , with nitride-doped tri-metallic material).
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least two secondary metals Me1 and Me2 are present in a ratio Me1/Me2 ranging from 1 to 15; preferably from 1 to 12; more preferably from 1 to 10; even more preferably, from 1 to 8; most preferably from 1 to 6; and even most preferably, froml to 4.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least two secondary metals Me1 and Me2 differ by their reduction potential wherein Me1 has a reduction potential greater than Me2, and Me1 and Me2 are present in a ratio Me1/Me2 greater than 1 ; preferably greater than 2; more preferably greater than 3.
• the step (b1) (or each sub-step of b1) was performed for a time ranging from 10 min to 5 hours; preferably from 15 min to 2.5 hours; more preferably from 20 min to 1 .5 hours, or from 10 min to 1 hour.
• the step (b1) (or each sub-step of b1) was performed at a temperature ranging from 40 to 250 °C.
• the method further comprises a step (b2) of electrodeposition on the copper particles of one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, iridium, osmium, and any mixture thereof; preferably, the one or more secondary metals are selected from silver, gold, platinum, palladium, ruthenium, and any mixture thereof; more preferably, the one or more secondary metals are selected from silver and/or gold.
• one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, and any mixture thereof; more preferably, the one or more secondary metals are selected from silver and/or gold.
• step of addition of one or more secondary metals is followed by a step of nitridation of the multi-metallic material obtained in step b) to obtain a nitride-doped multi-metallic material.
• the step of nitridation comprises a calcination sub-step followed by a copper nitride synthesis sub-step.
• a calcination sub-step is performed at a temperature ranging from 350 to 800°C for a time ranging from 30 min to 2 hours.
• the calcination sub-step is performed in condition to transform at least a part and preferably all Cu to CuO as evidenced by XRD.
• the calcination sub-step is followed by a sub-step of copper nitride (CusN) synthesis that is preferably performed at a low temperature by mixing the recovered calcined multi-metallic particles obtained from the calcination sub-step with sodium amide (NaNH2) at a temperature ranging from 150 to 190°C for a given time.
• Copper nitride synthesis at low temperature is known to the person skilled in the art and described in A. Miura, et al. J. Asian Ceram. Soc., 2014, 2, 326-328, which is incorporated herein by reference.
• the copper nitride synthesis sub-step is performed at a temperature ranging from 120 to 200°C; preferably from 150 to 190°C; more preferably from 160 to 180°C.
• the copper nitride synthesis sub-step is performed for a time ranging from 5 to 60 hours, preferably from 5 to 30 hours, and preferably from 10 to 25 hours. It was found that, at a given temperature, the nitridation time affects the activity of the catalyst, a too-long nitridation time results in a reduction of the catalyst activity.
• the copper nitride synthesis sub-step is performed to be incomplete (i.e. that some Cu remains in the catalyst) this can be achieved by a temperature below 150°C or a reduced nitridation time. In a preferred embodiment, the copper nitride synthesis sub-step is performed at a temperature ranging from 150 to 190°C and for a time ranging from 5 to 30 hours.
• the nitride-doped multi-metallic material shows an XRD pattern with a copper (Cu°) peak and copper nitride (CusN) peak. So that the catalyst comprises a mixture of copper and copper nitride.
• the nitride-doped multi-metallic material shows Cu (111) and Cu (200) facets as determined by XRD.
• the method to produce a catalyst may comprise: a) providing copper particles; b) addition of one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, iridium, osmium, and any mixture thereof, wherein said step of addition comprises a step (b1) of galvanic exchange reaction or a step (b2) of electrodeposition or both steps (b1) of galvanic exchange reaction and step (b2) of electrodeposition, to obtain a multi-metallic material comprising copper as primary metal and one or more secondary metals; c) nitridation of the multi-metallic material obtained in step b) to obtain a nitride-doped multi-metallic material.
• the method to produce a catalyst may comprise: a) providing copper particles; b) addition of one or more secondary metals selected from silver, gold, platinum, palladium, ruthenium, iridium, osmium, and any mixture thereof, wherein said step of addition comprises a step (b1) of galvanic exchange reaction; c) nitridation of the multi-metallic material obtained in step b) to obtain a nitride-doped multi-metallic material.
• the nitride-doped multi-metallic material comprises from 0.5 to 10.0 mol% as determined by XPS of the one or more secondary metals based on the total molar content of copper and one or more secondary metals; preferably from 0.6 to 9.0 mol% more preferably from 0.8 to 8.0 mol%; even more preferably from 1.0 to 7.5 mol%; most preferably from 1.1 to 7.0 mol%; even most preferably from 1.2 to 6.5 mol% or from 1 .3 to 6.0 mol%.
• the nitride-doped multi-metallic material comprises at least 0.5 mol% of the one or more secondary metals based on the molar content of coppe and one or more secondary metals r; preferably at least 0.6 mol%; more preferably at least 0.8 mol%; even more preferably at least 1.0 mol%; most preferably at least 1.1 mol%; even most preferably at least 1.2 mol% or at least 1.3 mol%.
• the nitride-doped multi-metallic material comprises at most 10.0 mol% of the one or more secondary metals based on the molar content of copper and one or more secondary metals; preferably at most 9.0 mol%; more preferably at most 8.0 mol%; even more preferably at most 7.5 mol%; most preferably at most 7.0 mol%; even most preferably at most 6.5 mol% or at most 6.0 mol%.
• the nitride-doped multi-metallic material is a nitride-doped bimetallic material and comprises from 1.0 to 10.0 mol% of the secondary metal based on the molar content of copper and the secondary metal; preferably from 1.5 to 9.0 mol%; more preferably, from 2.0 to 8.0 mol%; even more preferably from 2.5 to 7.5 mol%; most preferably from 3.0 to 7.0 mol%; even most preferably from 3.5 to 6.5 mol% or from 4.0 to 6.0 mol%.
• the nitride-doped multi-metallic material comprises two or more secondary metals, and comprises from 0.5 to 10.0 mol% or 0.5 to 8.0 mol% of the one or more secondary metals based on the molar content of copper two or more secondary metals; preferably from 0.6 to 9.0 mol%; more preferably from 0.8 to 8.0 mol%; even more preferably from 1.0 to 7.5 mol%; most preferably from 1.1 to 7.0 mol%; even most preferably from 1.2 to 6.5 mol% or from 1.3 to 6.0 mol% or from 1 .0 to 6.0 mol%.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least one of the secondary metals is silver or gold; preferably wherein at least two secondary metals are silver and gold.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least two secondary metals Me1 and Me2 are present in a ratio Me1/Me2 ranging from 1 to 15; preferably from 1 to 12; more preferably from 1 to 10; even more preferably, from 1 to 8; most preferably from 1 to 6; and even most preferably, froml to 4.
• the nitride-doped multi-metallic material comprises two or more secondary metals, wherein at least two secondary metals Me1 and Me2 differ by their reduction potential wherein Me1 has a reduction potential greater than Me2, and in that Me1 and Me2 are present in a ratio Me1/Me2 greater than 1 ; preferably greater than 2; more preferably greater than 3.
• the nitride-doped multi-metallic material is in the form of rode-shape particles.
• At least 50 % of the nitride-doped multi-metallic material are in the form of particles having an average diameter ranging from 20 nm to 500 nm as measured by transmission electron microscopy; preferably, ranging from 30 nm to 450 nm; more preferably from 50 nm to 400 nm; even more preferably from or from 80 to 350 nm and most preferably from 100 nm to 300 nm.
• At least 60 % of the nitride-doped multi-metallic material are in the form of particles having an average diameter ranging from 20 nm to 500 nm as measured by transmission electron microscopy; preferably at least 70 %; more preferably, at least 80 % and most preferably at least 90 %.
• At least 80 % of the nitride-doped multi-metallic material are in the form of particles having an average diameter ranging from 20 nm to 500 nm as measured by transmission electron microscopy; preferably, ranging from 30 nm to 450 nm; more preferably from 50 nm to 400 nm; even more preferably from or from 80 to 350 nm and most preferably from 100 nm to 300 nm.
• the gas diffusion electrode has a gas diffusion layer and an ink deposited on the gas diffusion layer; wherein the ink comprises an ion-conducting polymer, said gas diffusion electrode is remarkable in that the ink further comprises the above-described catalyst comprising nitride- doped multi-metallic material, preferably in the form of particles.
• the gas diffusion layer allows for the diffusion of carbon oxide (such as CO and/or CO2) as the main reactant of the electrochemical reduction reaction (i.e. the electrolysis reaction) into the electrochemical cell and is preferably a hydrophobic porous support.
• the gas diffusion layer is comprised within the gas chamber of said gas-fed flow cell.
• said support shows a pore size ranging from 400 nm to 500 nm as determined by scanning electron microscopy, preferably from 420 nm to 580 nm or from 440 nm to 560 nm. gas diffusion layer.
• the gas diffusion layer is a hydrophobic, porous and chemically inert support; with preference, the gas diffusion layer is not soluble in KOH.
• the gas diffusion layer is or comprises polytetrafluoroethylene (PTFE). Examples of suitable membranes are commercially available from Dioxide Materials.
• the gas diffusion layer has a circular shape and/or has a surface area of at least 1 cm 2 , or of at least 1 .5 cm 2 .
• the gas diffusion layer has a thickness ranging from 2 pm to 50 pm measured by scanning electron microscopy, preferably from 5 pm to 40 pm, more preferably from 8 pm to 30 pm.
• the ink is deposited on the gas diffusion layer and comprises an ion-conducting polymer.
• the ion-conducting polymer is or comprises an ionomer.
• the ionconducting polymer is or comprises an ionomer with a tetrafluoroethylene backbone group (- CF2-CF2-).
• ionomers are capable of creating strongly hydrophobic nanoporous networks.
• said ion-conducting polymer is or comprises a perfluorinated sulfonic acid, such as National® (tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer); and/or the ion-conducting polymer is or comprises tetrafluoroethylene- perfluoro(3-hydrophobioxa-4-pentenesulfonic acid) copolymer, such as Aquivion®.
• a perfluorinated sulfonic acid such as National® (tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer)
• tetrafluoroethylene- perfluoro(3-hydrophobioxa-4-pentenesulfonic acid) copolymer such as Aquivion®.
• ink has a ratio of the nitride-doped multi- metallic particles over the ion-conducting polymer.
• the gas diffusion electrode has a mass loading of the ink onto said gas diffusion layer ranging from 0.50 mg/cm 2 to 2.00 mg/cm 2 , preferably from 1.00 mg/cm 2 to 1.50 mg/cm 2 .
• the mass loading can be determined by weighing before and after deposition and drying.
• gas-fed flow cell suitable for the electrochemical reduction of one or more carbon oxides (such as the electrochemical reduction of carbon monoxide and/or the electrochemical reduction of carbon dioxide) of the present disclosure will then be described.
• the gas-fed flow cell comprises a gas chamber, a catholyte chamber and an anolyte chamber.
• the gas chamber has a gas channel, through which a flow of CO is circulating.
• the gas chamber is separated from the catholyte chamber by a gas diffusion electrode.
• the catholyte chamber and the anolyte chamber are separated by an anion exchange membrane (AEM).
• AEM anion exchange membrane
• the catholyte chamber and the anolyte chamber comprise respectively a cathode and an anode, for example, a Ni foam anode.
• any oxygen evolution reaction (OER) catalyst and anode compartment design can be used.
• the gas-fed flow cell of the present disclosure is remarkable in that the gas diffusion electrode is as defined above and in that the gas diffusion layer of said gas diffusion electrode is comprised within the gas chamber.
• the ink comprising the ion-conducting polymer and the nitride-doped multi-metallic particles as described above is comprised within the catholyte chamber.
• the gas-fed flow cell comprise a reference electrode.
• said reference electrode is an Ag/AgCI electrode filled with KCI at a concentration ranging from 3.0 to 3.8 M; preferably from 3.2 to 3.6 M; even more preferably with 3.4 M of KCI.
• the reference electrode could also be a reversible hydrogen electrode (RHE).
• the preparation of the catalyst i.e. of the nitride-doped multi-metallic particles, is as described above
• the nitride-doped multi-metallic particles described above are washed and dried after step (c) and/or before the steps reguired to prepare the gas diffusion electrode.
• the step of washing is performed with an organic solvent and the step of drying lasts at least 12 hours, preferably at least 24 hours and/or lasts no more than 48 hours, preferably no more than 36 hours.
• the organic solvent is selected from dichloromethane, ethyl acetate, acetone, dimethylformamide, acetonitrile, n-butanol, n- propanol, methanol, ethanol and any mixture thereof; with preference, the organic solvent is or comprises ethanol and/or methanol.
• the nitride-doped multi-metallic particles are, in step (d), dispersed into ethanol to obtain a second dispersion. It is preferred that the second dispersion is sonicated. With preference, said sonicating is achieved at room temperature, for example at a temperature ranging from 20°C and 30°C. With preference yet, said sonicating is achieved for at least 10 minutes, preferably for at least 15 minutes and/or for no more than 60 minutes, preferably no more than 45 minutes.
• step (e) an ion-conducting polymer, such as National®, is added to obtain the ink.
• the ink is then deposited in step (f) on a gas-diffusion layer, for example, a gas-diffusion layer that is or comprises polytetrafluoroethylene.
• a gas-diffusion layer for example, a gas-diffusion layer that is or comprises polytetrafluoroethylene.
• the ink is drop-casted on the gas-diffusion layer.
• the present disclosure is about a process for electrochemically reducing carbon oxides (such as carbon monoxide and/or carbon dioxide), said process comprising the following steps: i. providing a gas-fed flow cell; ii. providing at least one electrolyte flow into said gas-fed flow cell wherein the at least one electrolyte flow is a catholyte flow and an anolyte flow; iii. activating said gas-fed flow cell; iv. providing an input flow comprising one or more carbon oxides selected from carbon monoxide, carbon dioxide, and a mixture of carbon monoxide and carbon dioxide to produce an output flow of catholyte comprising at least n-propano and/or ethanol; v. recovering said output flow comprising at least n-propanol and/or ethanol; said process is remarkable in that the gas-fed flow cell provided at step (i) is as defined above.
• the process needs to have both a flowing catholyte and a flowing anolyte.
• the current density is at least 100 mA cm- 2 with preference at least 150 mA cm- 2
• electrolyte flow hereafter refers to the catholyte flow but also applies to the anolyte flow in the case of a flowing anolyte.
• the electrolyte flow provided in step (ii) has a flow rate that is ranging from 2.5 mL min-1 to 8.5 mL min-1 , preferably from 3.0 mL min-1 to 8.0 mL min-1 , more preferably from 3.5 mL min-1 to 7.5 mL min-1.
• the electrolyte flow provided in step (ii) is a flow of an aqueous solution of one or more inorganic bases.
• the one or more inorganic bases are alkali selected from NaOH, KOH, Ca(OH)2, LiOH, Mg(OH)2, RbOH, CsOH and any mixture thereof.
• the one or more inorganic bases are or comprise KOH and/or NaOH.
• the aqueous solution of one or more inorganic bases has a pH ranging from 7 to 15.
• the aqueous solution of one or more inorganic bases has a concentration of at least 0.05 M, or at least 0.1 M, or or at leats 1 M, or at least 2 M, or at least 3 M, or at least 4 M.
• the aqueous solution of one or more inorganic bases has a concentration of at most 10 M, of at most 8 M, or at most 7 M, or at most 6 M, or at most 5 M.
• the concentration of the aqueous solution of one or more inorganic bases is ranging from 0.1 M to 10 M; preferably from 3 M to 7 M, or preferably from 0.1 M to 5 M.
• the aqueous solution of one or more inorganic bases is an aqueous solution of KOH at a concentration of at least 0.05 M, or at least 0.1 M, or at least 1 M, or at least 2 M, or at least 3 M, or at least 4 M.
• said at least one alkaline compound is an aqueous solution of KOH at a concentration of at most 10 M, of at most 8 M, or at most 7 M, or at most 6 M or at most 5 M.
• the concentration of KOH in a solution of water ranges from 0.1 to 10 M; preferably from 3 M to 7 M, more preferably from 0.1 M to 5 M.
• said step (iii) is performed by injecting carbon oxide (such as carbon monoxide and/or carbon dioxide) at a potential gradient starting at -0.3 V versus a reference electrode and ending at -2.0 V versus said reference electrode at a sweep rate ranging from 15 mV s-1 to 100 mV s-1 or from 30 mV s-1 to 60 mV s-1.
• the potential gradient starts at -0.5 V versus a reference electrode and ends at -1.8 V versus said reference electrode.
• the reference electrode is an Ag/AgCI electrode filled with 3.4 M of KCI.
• the output flow of catholyte in addition to comprising n-propanol and/or ethanol, can also comprise one or more selected from acetate.
• said step (iv) lasts at least 1 hour, more preferably at least 2 hours, even more preferably at least 3 hours, most preferably at least 4 hours, even most preferably at least 5 hours or at least 6 hours.
• the input flow comprising one or more carbon oxides provided in step (iv) has a flow rate that ranges from 5 mL min -1 to 150 mL min -1 , preferably from 8 mL min -1 to 100 mimin' 1 , more preferably from 10 mL min -1 to 80 mL min -1 , even more preferably from 15 mL min' 1 to 50 mL min -1 .
• said step (iv) is performed at room temperature, for example at a temperature ranging from 20°C to 30°C.
• said step (iv) is performed at atmospheric pressure, for example at a pressure ranging from 0.09 MPa to 0.11 MPa.
• Mass loading of the ink onto the gas diffusion layer The membrane was weighed using an analytical balance before deposition and after drying overnight in a vacuum desiccator.
• TEM analysis was conducted using a Jeol 21 OOF microscope equipped with Schottky Field Emission electron gun and an ultra-high resolution polar piece.
• X-Ray Diffraction X-Ray Diffraction data were obtained from a D8 ADVANCE diffractometer (Bruker) using a Cu Ka X-ray source (1.5406A). Peaks were attributed using the PDF-2/release 2013 RDB database.
• XPS measurement Surface elemental composition was determined by X-ray photoelectron spectroccopy (XPS; Thermo Electron Escalab 250) using a monochromated Al Ka radiation (1486.6 eV) and photoelectron take-off angle of 90°. Survey and high resolution spectra energy was 100 eV and 20 eV, respectively. Thermo Electron software Avantage was used for curve fitting of the XPS spectra.
• Example 1 the bimetallic catalysts
• Cu powder with a size of 25 nm purchased from Sigma Aldrich was used as the substrate.
• Copper-silver (Cu/Ag), copper-gold (Cu/Au), and copper-palladium (Cu/Pd) bimetallic compounds were prepared by a galvanic exchange method, in which the Cu powder was stirred in an aqueous solution of AgNCh, HAuCk or Pd(NOs)2 with from 2 to 8 mol% as the second metal to Cu, at 60 °C for 30 minutes.
• Cu, Cu/Ag, Cu/Pd or Cu/Au powder was calcined in air at 500 °C for 1 h to transform the Cu species to CuO.
• the powder (10 mg) was mixed with NaNH2 98% purchased from Sigma Aldrich (100 mg) by mortar and pestle, then put into a Teflon-lined autoclave in a glovebox filled with Ar.
• the autoclave was heated at 170 °C for 20 h. After cooling down, ethanol was added to the mixture and the catalyst was collected after washing and centrifuging with water and ethanol.
• the CusN/Ag(5%) was composed of CU3N, CuAg and Cu.
• the CU3N was mainly comprised of Cu and CU3N. While Cu/Ag(5%) contained Cu, CuAg and a small relative amount of CU2O which could be due to oxidation in air.
• Cu substrate was composed of nanoparticles with sizes from 25 to 40 nm.
• Cu/Ag(5%) sample contained particles of similar size and its surface was decorated with lots of smaller particles of a size of several nanometers. This result indicated that a galvanic exchange reaction between AgNCh and Cu substrate occurred.
• CU3N was completely formed with 25 h of nitridation.
• the amount of CU3N or Cu(0) was dependent on the nitridation time. Varying the content of Ag affected the relative amount of Cu in the sample, the CusN/Ag(5%) showed both Cu(111) and Cu(200) phases, while CusN/Ag(2 or 8%) showed only Cu(111) phase. Besides, the peak intensity of Ag increased as the content of Ag was increased.
• Example 2 gas diffusion electrodes preparation with bimetallic catalysts
• the catalyst was mixed with National® (tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer) and ethanol with a ratio of 1.5 mg : 5 l : 100 pl. Then, the suspension was drop cast onto a gas diffusion layer (PTFE of 30%) purchased from dioxide materials with a loading of 1.5 mg.cnr 2 . The thus obtained catalyst-loaded gas diffusion electrode was used as the cathode.
• PTFE gas diffusion layer
• the GDEs of example 2 were electrically connected in a gas-fed flow cell for electrochemical testing.
• the activity was investigated for CO reduction of the copper nitride, copper nitride-silver and silver-copper catalysts, taking the Cu sigma powder as the reference.
• CusN sample showed FE for n-propanol of 17-18% at -100 and -150 mA. cm -2 , while FE for ethanol was almost the same and acetate was slightly lower compared to that of Cu sigma. This result indicates that nitridation was effective to enhance the selectivity for n-propanol.
• FE for propanol was around 10%
• FE for ethanol was around 20% at -100 and -150 mA. cm -2
• CusN/Ag sample showed a significant improvement of activity for n-propanol with a high FE of 23% and 39% at -100 and -150 mA.cnr 2 , respectively. This high efficiency for propanol is comparable to the highest value reported so far (by Sargent and colleagues, Nat Energy, 2022, 7, 170-176). It is noteworthy that the total FE for alcohols (propanol and ethanol) is about 62%.
• the nitridation time for the sample was also optimized.
• the activity of the samples prepared with different nitridation times (10-60 h) is presented in Fig. 5.
• nitridation time had a significant effect on the activity of CusN/Ag(5%) for CO reduction to propanol
• the sample synthesized with 20 h of nitridation showed the highest FE for n-propanol of 39% at -150 mA. cm -2 of current density.
• the nitridation time of 10 h showed the second highest FE for n-propanol of 25% at 100 and 150 mA. cm -2 , respectively.
• a significant increase in nitridation time to 40 or 60 h gave a lower FE for n- propanol of 15%.
• the activity for CO reduction was also investigated with different content of Ag.
• the sample with 5% of Ag showed the highest FE for propanol at 150 mA. cm -2 .
• the sample with 2% of Ag showed the highest FE for propanol of around 35%.
• the activity for CO reduction was also investigated in the highly active CusN/Au(5%) and CusN/Ag(5%) catalysts at different current densities.
• Cu powder with a size of 25 nm purchased from Sigma Aldrich was used as the substrate.
• Copper-gold (Cu/Au) bimetallic compounds were prepared by a galvanic exchange method, in which the Cu powder was stirred in an aqueous solution of HAuCk with from 0.3 to 5 mol% as the second metal to Cu, at 60 °C for 30 minutes.
• the thus obtained powder was collected and washed with water and ethanol by centrifugation.
• Cu, or Cu/Au/Ag powder was calcined in air at 500 °C for 1 h to transform the Cu species to CuO. Then, the powder (10 mg) was mixed with NaNF 98% purchased from Sigma Aldrich (100 mg) by mortar and pestle, then put into a Teflon-lined autoclave in a glovebox filled with Ar. The autoclave was heated at 170 °C for 20 h. After cooling down, ethanol was added to the mixture and the catalyst was collected after washing and centrifuging with water and ethanol.
• Example 5 gas diffusion electrodes preparation with tri-metallic catalysts
• the catalyst of example 4 was mixed with National® (tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid copolymer) and ethanol with a ratio of 1.5 mg : 5 pl : 100 pl. Then, the suspension was drop cast onto a gas diffusion layer (PTFE of 30%) purchased from dioxide materials with a loading of 1.5 mg. cm -2 . The thus obtained catalyst-loaded gas diffusion electrode was used as the cathode.
• PTFE gas diffusion layer
• the GDEs of example 5 were electrically connected in a gas-fed flow cell for electrochemical testing.
• the activity was investigated for CO reduction of the trimetallic catalysts.
• the highest ratio FE a icohois/FE e thysiene of 5.4 was achieved with Cu3N/Au(1%)Ag(0.3%).
• Au and Ag co-presence gave much higher FE a icohois/FE e thysiene ratio than Au or Ag alone.

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