Electrolyzer for gaseous carbon dioxide

Abstract

An electrochemical device and method can include techniques involving bipolar membrane electrolysis to transform an input product into an output product. Some embodiments can include a gas-diffusion electrode as a cathode, a bipolar membrane configured to facilitate autodissociation, and an anode that can be configured as a liquid-electrolyte style electrode or a gas-diffusion electrode. In some embodiments the electrochemical device can be configured as a CO 2 electrolyzer that is designed to utilize input product including carbon dioxide gas and water to generate output products that can include gaseous carbon monoxide or other reduction products of carbon dioxide and gaseous oxygen or the oxidation products of a depolarizer such as hydrogen, methane, or methanol. Embodiments can be utilized in the production of fuels or feedstocks for fuels and carbon-containing chemicals, in air purification systems, flue gas treatment devices, and other machines and facilities.

What is claimed is: 
     
         1 . An electrochemical device, comprising:
 an electrochemical cell comprising a cathode, an anode, and a membrane;   wherein:
 at least a portion of the cathode is separated from at least a portion of the anode by the membrane; 
 the cathode comprises a gas-diffusion electrode; 
 the anode comprises at least one of a liquid-electrolyte style electrode and a gas-diffusion electrode; and 
 the membrane is a bipolar membrane, the bipolar membrane being configured to maintain a flux of protons to the cathode and also maintain a flux of hydroxide ions to the anode, 
 wherein the electrochemical cell is configured to receive carbon dioxide gas and water and output reduction products of carbon dioxide at the cathode and oxygen or other oxidized products of a depolarizer at the anode. 
   
     
     
         2 . The electrochemical device recited in  claim 1 , wherein the bipolar membrane comprises a cation exchange membrane and an anion exchange membrane. 
     
     
         3 . The electrochemical device recited in  claim 1 , wherein the bipolar membrane is configured to promote autodissociation of water. 
     
     
         4 . The electrochemical device recited in  claim 1 , wherein the bipolar membrane further comprises a membrane catalyst. 
     
     
         5 . The electrochemical device recited in  claim 4 , wherein the membrane catalyst comprises at least one of a silicate, an amine polymer, graphite oxide, and an anolyte solution. 
     
     
         6 . The electrochemical device recited in  claim 2 , wherein the anion exchange membrane comprises a cation-exchange polymer film. 
     
     
         7 . The electrochemical device recited in recited in  claim 1 , wherein the electrochemical cell has a cell first end and a cell second end, the electrochemical device also comprising:
 a cathode flow medium positioned between the bipolar membrane and the cathode; and   an anode flow medium positioned between the bipolar membrane and the anode.   
     
     
         8 . The electrochemical device recited in  claim 7 , wherein:
 the cathode flow medium has at least one cell inlet and at least one cell outlet; and   the anode flow medium has at least one cell inlet and at least one cell outlet.   
     
     
         9 . The electrochemical device recited in  claim 8 , wherein the cathode flow medium comprises carbon and the anode flow medium comprises carbon. 
     
     
         10 . The electrochemical device recited in  claim 8 , wherein:
 the electrochemical device is configured as a carbon dioxide electrolyzer,   the cathode comprises a cathode catalysts configured as a carbon dioxide reduction catalyst; and   the anode comprises an anode catalyst configured as a water oxidation catalyst or as a catalyst for oxidation of the depolarizer, the depolarizer comprising hydrogen, methane, or methanol.   
     
     
         11 . The electrochemical device recited in  claim 10 , wherein the electrochemical cell is configured to receive carbon dioxide gas and generate reduction products of carbon dioxide that include any one or combination of formic acid, methanol, methane, formaldehyde, acetaldehyde, acetic acid, glyoxal, ethanol, ethene, ethane, ethylene glycol, dimethyl ether, methyl formate, propene, propane, n-propanol, isopropanol, and isomers of butanol, and hydrogen. 
     
     
         12 . A method of reducing product crossover in an electrochemical cell of an electrochemical device, the method comprising:
 configuring a bipolar membrane of an electrochemical cell that is positioned between an anode and a cathode to cause ions to travel towards an anode electrode and a cathode electrode of the electrochemical cell when the electrochemical cell is under an applied current condition;   operating the electrochemical cell so that the bipolar membrane facilitates a supply of protons (H + ) to the cathode to cause water (H 2 O) to self-ionize via autodissociation to generate hydroxide ions (OH − ) and protons H +  to supply a flux of the OH −  to the anode and supply a flux of the H +  to the cathode.   
     
     
         13 . The method recited in  claim 12 , wherein the flux of H +  provided by the bipolar membrane opposes product crossover in the electrochemical cell. 
     
     
         14 . The method recited in  claim 12 , wherein the bipolar membrane has an anion exchange layer and a cation exchange layer joined together at an interfacial layer, the interfacial layer configured to catalyze autodissociation of H 2 O. 
     
     
         15 . The method recited in  claim 14 , further comprising
 depositing at least one catalyst layer on the interfacial layer.   
     
     
         16 . The method recited in  claim 15 , further comprising tuning water dissociation reactions at the interfacial layer via adjusting a type of the catalyst and/or an amount of the catalyst. 
     
     
         17 . The method recited in  claim 15 , wherein the at least one catalyst layer comprises graphite oxide. 
     
     
         18 . The method recited in  claim 15 , wherein the cation exchange layer and the anion exchange layer define a cation-anion exchange junction region; and
 wherein the cation-anion exchange junction is configured so that the cation exchange layer interpenetrates the anion exchange layer and/or the anion exchange layer interpenetrates the cation exchange layer.   
     
     
         19 . The method recited in  claim 18 , further comprising:
 generating a plurality of transport pathways for water dissociation products H +  and OH −  to flow via the interpenetrating cation exchange layer and anion exchange layer.   
     
     
         20 . The method recited in  claim 19 , wherein:
 the electrochemical device is a carbon dioxide electrolyzer,   the cathode comprises a cathode catalyst configured as a carbon dioxide reduction catalyst;   the anode comprises an anode catalyst configured as a water oxidation catalyst or as a catalyst for a depolarizer, the depolarizer comprising hydrogen, methane, or methanol; and   the electrochemical cell includes:
 a cathode flow medium between the cathode and the bipolar membrane, the cathode flow medium comprising carbon, at least one cell inlet of the cathode flow medium is configured to receive carbon dioxide, and at least one cell outlet of the cathode flow medium is configured to output carbon monoxide gas and/or water; 
   an anode flow medium between the anode and the bipolar membrane, the anode flow medium comprising carbon, at least one cell inlet of the anode flow medium configured to receive water and/or an electrolyte and/or the depolarizer, and at least one cell outlet of the anode flow medium configured to output oxygen or the oxidized product of the depolarizer;   and wherein the operating of the electrochemical cell comprises:   feeding water and/or an electrolyte and/or the depolarizer to the anode flow medium;   feeding a flow of carbon dioxide and water to the cathode flow medium;   outputting oxygen and/or the oxidation products of the depolarizer from the anode flow medium; and   outputting carbon monoxide and/or other reduction products of carbon dioxide from the cathode flow medium.