Improved Electrochemical Ammonia Synthesis

Abstract

The invention regards a method for electrochemical ammonia synthesis, comprising the steps of: —providing an electrolysis cell having a cathode, —contracting the cathode with a source of cations preferably lithium cations, a source of nitrogen a source of oxygen, and a source of protons, wherein the oxygen source provides a predefined oxygen concentration, and —subjecting the cell to a potential and current load, whereby ammonia is synthesized.

1 . A method for electrochemical ammonia synthesis, comprising the steps of:
 providing at least one electrolysis cell having a cathode,   contacting the cathode with a source of cations, a source of nitrogen, a source of oxygen, and a source of protons, wherein the oxygen source provides a predefined oxygen concentration,   subjecting the cell to a potential and current load, whereby ammonia is synthesized.   
     
     
         2 . The method according to  claim 1 , wherein the oxygen concentration is below 20%. 
     
     
         3 . The method according to  claim 1 , wherein the source of oxygen comprises an oxygen partial pressure of between 0.02-2.5 bar. 
     
     
         4 . The method according to  claim 1 , further comprising a step of subjecting the cathode to a continuous pulsed cathode potential, including a pulsed cathodic current load. 
     
     
         5 . The method according to  claim 4 , wherein the cathode potential is pulsed between a first cathode potential, including a first cathodic current load, and a second cathode potential, including a second cathodic current load. 
     
     
         6 . The method according to  claim 4 , wherein the cathode potential is pulsed between the lithium reduction potential and a less negative cathode potential, such as wherein the cathode potential is pulsed between the lithium reduction potential and the cell OCP. 
     
     
         7 . The method according to  claim 1 , wherein the pulsed cathodic current load is pulsating DC and/or pulsating AC. 
     
     
         8 . The method according to  claim 5 , wherein the pulses at the first cathodic current load has a current density below −1 mA/cm geo   2 . 
     
     
         9 . The method according to  claim 5 , wherein the pulses at the second cathodic current load has a current density above -0.5 mA/cm geo   2 . 
     
     
         10 . The method according to  claim 1 , wherein the temperature is between 10-150° C. 
     
     
         11 . The method according to  claim 1 , wherein the pressure is equal to or below 20 bar. 
     
     
         12 . The method according to  claim 1 , wherein the source of nitrogen is selected from the group consisting of: gaseous N 2 , liquidly dissolved N 2 , and combinations thereof. 
     
     
         13 . The method according to  claim 1 , wherein the source of oxygen is selected from the group of: air, CO 2 , CO, NO x , or H 2 O, alcohols, aldehydes, peroxides, superoxides, and organic acids which contain oxygen, and oxygen from transition metal electrodes in the form of oxides and carbonates. 
     
     
         14 . The method according to  claim 1 , wherein the source of oxygen and/or nitrogen is processed synthetic air, processed to a defined oxygen concentration. 
     
     
         15 . The method according to  claim 14 , wherein the synthetic air is processed to an oxygen concentration of below 20%. 
     
     
         16 . The method according to  claim 1 , wherein the source of protons is selected from the group consisting of: gaseous Hz, liquidly dissolved Hz, ethanol, water, alkyl alcohols, tert-butanol, perfluorinated alcohols, polyethyleneglycols, ethanethiol, alkyl thiols, alkyl ketones, alkyl esters and mixtures thereof. 
     
     
         17 . The method according to  claim 1 , wherein the cathode comprises a high surface area metal electrode. 
     
     
         18 . The method according to  claim 17 , wherein the cathode comprises a Cu electrode made by hydrogen bubbling templating on a transition metal substrate. 
     
     
         19 . An apparatus for electrochemical ammonia synthesis, comprising
 at least one electrolysis cell having a cathode, said electrolysis cell connectable to at least one power source and at least one nitrogen source and at least one oxygen source, and   at least one controller configured for regulating the power source input to the electrolysis cells and the oxygen input to the electrolysis cells,   wherein the apparatus is configured for
 contacting the cathode of the electrolysis cell with a source of cations, a source of nitrogen, a source of oxygen, and a source of protons, 
   subjecting the electrolysis cell to a potential and current load by regulating the power source input to the electrolysis cell, and   regulating the oxygen input to the electrolysis cell such that the concentration of oxygen in the electrolysis cell is below 20%.   
     
     
         20 . The apparatus according to  claim 19 , further comprising an oxygen separator fluidly connectable to the oxygen source and/or nitrogen source.