Methods for electrochemical reduction of carbon dioxide

Abstract

Method of reducing carbon dioxide to form one or more hydrocarbon products, the method comprising: providing an electrochemical cell comprising: a working electrode comprising a copper composite comprising a copper nanosheet array comprising a plurality of copper nanosheets, wherein the plurality of copper nanosheets comprise copper(100) facets; a counter electrode; optionally a reference electrode; and an electrolyte solution comprising an electrolyte and CO 2 , wherein the electrolyte solution is between and in contact with the working electrode, the counter electrode, and optionally the reference electrode; and applying an electric current between the working electrode and the counter electrode resulting in electrolytic reduction of the CO 2 thereby forming the one or more hydrocarbon products.

1 . A method of reducing carbon dioxide to form one or more hydrocarbon products, the method comprising:
 providing an electrochemical cell comprising:   a working electrode comprising a copper composite comprising a copper nanosheet array comprising a plurality of copper nanosheets, wherein the plurality of copper nanosheets comprise copper(100) facets, the copper nanosheet array is disposed on a surface of a modified copper substrate, the copper nanosheet array is chemically bonded to the modified copper substrate, and the copper composite is prepared by contacting a copper substrate with an oxidizing agent thereby forming an oxidized copper composite comprising a modified copper substrate and an oxidized copper nanosheet array, wherein the oxidized copper nanosheet array is disposed on a surface of the modified copper substrate and the oxidized copper nanosheet array is chemically bonded to the modified copper substrate, and electrochemically reducing the oxidized copper composite thereby forming the copper composite;   a counter electrode;   optionally a reference electrode; and   an electrolyte solution comprising an electrolyte and CO 2 , wherein the electrolyte solution is between and in contact with the working electrode, the counter electrode, and optionally the reference electrode; and applying an electric current at a voltage of −1.0 to −1.2V (versus a reversible hydrogen electrode) between the working electrode and the counter electrode resulting in electrolytic reduction of the CO 2  thereby forming the one or more hydrocarbon products.   
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1 , wherein the plurality of copper nanosheets have an average thickness of 20-30 nm. 
     
     
         4 . The method of  claim 1 , wherein the copper composite further comprises potassium ions disposed on at least one surface of the copper nanosheet array. 
     
     
         5 . The method of  claim 1 , wherein the electrolyte comprises a metal carbonate, a metal bicarbonate, a metal hydroxide, a metal oxide, or a mixture thereof. 
     
     
         6 . The method of  claim 1  further comprising electrochemically reducing the oxidized copper composite thereby forming the copper composite. 
     
     
         7 . The method of  claim 6 , wherein the step of reducing the oxidized copper composite is conducted in situ in the electrochemical cell. 
     
     
         8 . The method of  claim 6  further comprising contacting the copper substrate with the oxidizing agent thereby forming the oxidized copper composite. 
     
     
         9 . The method of  claim 8 , wherein the copper substrate is a copper foil, a copper foam, or a copper mesh. 
     
     
         10 . The method of  claim 8 , wherein the oxidizing agent is potassium persulfate. 
     
     
         11 . The method of  claim 1 , wherein the one or more hydrocarbon products comprise C 1 -C 3  hydrocarbons. 
     
     
         12 . The method of  claim 1 , wherein the one or more hydrocarbon products comprise formic acid, methanol, methane, ethylene, ethanol, or n-propanol. 
     
     
         13 . The method of  claim 1 , wherein the one or more hydrocarbon products comprise C 2-3  hydrocarbons and C 1  hydrocarbons in a molar ratio of 2:1 to 7.2:1, respectively. 
     
     
         14 . The method of  claim 1 , wherein the one or more hydrocarbon products comprise ethylene as a major product. 
     
     
         15 . The method of  claim 1 , wherein the plurality of copper nanosheets have an average thickness between 20-30 nm; the electrolyte comprises K 2 CO 3 , KHCO 3 , KOH, or a mixture thereof; and the one or more hydrocarbon products comprise C 2-3  hydrocarbons and C 1  hydrocarbons in a molar ratio of 2:1 to 7.2:1, respectively. 
     
     
         16 . The method of  claim 15 , wherein the electrolyte comprises KHCO 3 ; and the one or more hydrocarbon products comprise C 2-3  hydrocarbons and C 1  hydrocarbons in a molar ratio of 6:1 to 7.2:1, respectively. 
     
     
         17 . A method of reducing carbon dioxide to form one or more C 1-3  hydrocarbon products, the method comprising:
 providing an electrochemical cell comprising:   a working electrode comprising a copper composite, wherein the copper composite comprises a modified copper substrate and a copper nanosheet array comprising a plurality of copper nanosheets comprising copper(100) facets, wherein the plurality of copper nanosheets have an average thickness of 20-30 nm, wherein the copper nanosheet array is disposed on a surface of the modified copper substrate and the copper nanosheet array is chemically bonded to the modified copper substrate, and the copper composite is prepared by contacting a copper substrate with an oxidizing agent thereby forming an oxidized copper composite comprising a modified copper substrate and an oxidized copper nanosheet array, wherein the oxidized copper nanosheet array is disposed on a surface of the modified copper substrate and the oxidized copper nanosheet array is chemically bonded to the modified copper substrate, and electrochemically reducing the oxidized copper composite thereby forming the copper composite;   a counter electrode;   optionally a reference electrode; and   an electrolyte solution comprising a KHCO 3  and CO 2 , wherein the electrolyte solution is between and in contact with the working electrode, the counter electrode, and optionally the reference electrode; and   applying an electric current at a voltage of −1.0 to −1.2V (versus a reversible hydrogen electrode between the working electrode and the counter electrode resulting in electrolytic reduction of the CO 2  thereby forming the one or more C 1-3  hydrocarbon products, wherein the one or more hydrocarbon products comprise C 2-3  hydrocarbons selected from the group consisting of ethylene, ethanol, and n-propanol and C 1  hydrocarbons selected from the group consisting of formic acid, methanol, and methane in a molar ratio of C 2-3  hydrocarbons to C 1  hydrocarbons of 6:1 to 7.2:1, respectively.   
     
     
         18 . The method of claim  18  further comprising contacting the copper substrate with potassium persulfate thereby forming the oxidized copper composite; and electrochemically reducing the oxidized copper composite thereby forming the copper composite. 
     
     
         19 . The method of  claim 18 , wherein the step of reducing the oxidized copper composite is conducted in situ in the electrochemical cell. 
     
     
         20 . The method of  claim 17 , wherein the one or more hydrocarbon products comprise ethylene as a major product.