Low-temperature method for electrochemical conversion of carbon dioxide to carbon

Abstract

A method for converting carbon dioxide to carbon (e.g., graphite, graphene, or amorphous porous carbon), the method comprising passing the carbon dioxide through a molten anhydrous salt maintained at a temperature within a range of 400° C.-800° C. while the molten anhydrous salt is in contact with a cathode and an anode that are electrically interconnected to impart a voltage to the molten anhydrous salt, wherein the cathode has a metal composition comprising at least one of nickel, iron, and cobalt, wherein the voltage is within a range of 2 V to 3.5 V, and wherein the temperature and voltage are applied for a period of time of 5 minutes to 10 hours (or, e.g., 0.1-10 or 1-10 hours) to result in conversion of the carbon dioxide to carbon.

What is claimed is: 
     
         1 . A method for converting carbon dioxide to carbon, the method comprising passing the carbon dioxide through a molten anhydrous salt maintained at a temperature within a range of 400° C.-800° C. while the molten anhydrous salt is in contact with a cathode and an anode that are electrically interconnected to impart a voltage to the molten anhydrous salt, wherein the cathode has a metal composition comprising at least one of nickel, iron, and cobalt, wherein the voltage is within a range of 2 V to 3.5 V, and wherein the temperature and voltage are applied for a period of time of 5 minutes to 10 hours to result in conversion of the carbon dioxide to carbon. 
     
     
         2 . The method of  claim 1 , wherein the molten anhydrous salt comprises a lithium salt or lithium oxide and at least one salt selected from non-lithium alkali metal salts and alkaline earth metal salts, provided that the molten anhydrous salt has a melting point within a range of 400° C.-800° C. 
     
     
         3 . The method of  claim 1 , wherein the molten anhydrous salt comprises a lithium salt or lithium oxide and at least one salt selected from non-lithium alkali metal salts and alkaline earth metal salts and at least one metal hydroxide selected from sodium hydroxide and potassium hydroxide, provided that the molten anhydrous salt has a melting point within a range of 400° C.-800° C. 
     
     
         4 . The method of  claim 1 , wherein the molten anhydrous salt comprises lithium carbonate and at least one salt selected from non-lithium alkali metal salts and alkaline earth metal salts, provided that the molten anhydrous salt has a melting point within a range of 400° C.-800° C. 
     
     
         5 . The method of  claim 1 , wherein the molten anhydrous salt comprises lithium carbonate and at least one salt selected from sodium carbonate and potassium carbonate. 
     
     
         6 . The method of  claim 1 , wherein the molten anhydrous salt comprises lithium carbonate, sodium carbonate, and potassium carbonate. 
     
     
         7 . The method of  claim 1 , wherein the molten anhydrous salt is maintained at a temperature within a range of 400° C.-700° C. 
     
     
         8 . The method of  claim 1 , wherein the molten anhydrous salt is maintained at a temperature within a range of 400° C.-600° C. 
     
     
         9 . The method of  claim 1 , wherein the molten anhydrous salt is maintained at a temperature within a range of 400° C.-550° C. 
     
     
         10 . The method of  claim 1 , wherein the cathode is a porous cathode. 
     
     
         11 . The method of  claim 10 , wherein the cathode is a nickel foam cathode. 
     
     
         12 . The method of  claim 10 , wherein the carbon produced by the method is substantially graphitic, with a degree of graphitization of at least 0.95. 
     
     
         13 . The method of  claim 10 , wherein the molten anhydrous salt is maintained at a temperature within a range of 500° C.-800° C. at a voltage within a range of 2.5 V to 3.5 V and the carbon produced by the method is substantially graphitic, with a degree of graphitization of at least 0.95. 
     
     
         14 . The method of  claim 13 , wherein the voltage is within a range of 2.5 V to 3.0 V. 
     
     
         15 . The method of  claim 13 , wherein the temperature and voltage are maintained for a period of time of 0.1-3.5 hours to result in conversion of the carbon dioxide to the substantially graphitic carbon. 
     
     
         16 . The method of  claim 10 , wherein the molten anhydrous salt is maintained at a temperature within a range of 400° C.-500° C. and the carbon produced by the method comprises graphene. 
     
     
         17 . The method of  claim 1 , wherein the cathode is a nickel or steel plate, and the carbon produced by the method is substantially amorphous carbon. 
     
     
         18 . The method of  claim 17 , wherein the substantially amorphous carbon is porous carbon. 
     
     
         19 . The method of  claim 18 , wherein the porous carbon comprises microporous or mesoporous carbon. 
     
     
         20 . The method of  claim 1 , wherein the molten anhydrous salt is maintained at a temperature within a range of 500° C.-700° C. and the carbon produced by the method is substantially amorphous carbon. 
     
     
         21 . The method of  claim 20 , wherein the temperature and voltage are maintained for a period of time of 3-10 hours to result in conversion of the carbon dioxide to the substantially amorphous carbon. 
     
     
         22 . The method of  claim 20 , wherein the temperature and voltage are maintained for a period of time of 4-10 hours to result in conversion of the carbon dioxide to the substantially amorphous carbon. 
     
     
         23 . The method of  claim 20 , wherein the cathode is a nickel or steel plate. 
     
     
         24 . The method of  claim 20 , wherein the substantially amorphous carbon is porous carbon. 
     
     
         25 . The method of  claim 24 , wherein the porous carbon comprises microporous or mesoporous carbon.