Methods for prevention or removal of precipitated salts to improve electrochemical co2 reduction reactions

Abstract

An apparatus for the electrochemical reduction of CO 2 includes an anode compartment comprising anolytes and a cathode compartment comprising a cathode endplate and a cathode catalyst. The cathode endplate may include recessed flow channels included in a removable plate and/or coated with a hydrophobic coating. A method for the electrochemical reduction of CO 2 includes providing the apparatus as described above supplying a CO 2 feed stream to the cathode compartment, reducing the CO 2 feed stream at the cathode catalyst to form a carbon species by applying a voltage to the device where upon applying the voltage to the device, a portion of the anolytes crossover from the anode compartment to the cathode compartment, forming precipitated salts, and reducing accumulation of precipitated salts in the cathode compartment while reducing the CO 2 feed stream at the cathode catalyst. The method may include periodically injecting aqueous acid into the CO 2 feed stream.

What is claimed is: 
     
         1 . A method for removing precipitated salts formed during the electrochemical reduction of CO 2 , the method comprising:
 providing an electrochemical device comprising:
 a cathode compartment comprising a cathode endplate and a cathode catalyst; and 
 an anode compartment comprising anolytes; 
   supplying a CO 2  feed stream to the cathode compartment;   reducing the CO 2  feed stream at the cathode catalyst to form a carbon species by applying a voltage to the device;   wherein upon applying the voltage to the device, a portion of the anolytes crossover from the anode compartment to the cathode compartment, forming precipitated salts; and   reducing accumulation of precipitated salts in the cathode compartment while reducing the CO 2  feed stream at the cathode catalyst.   
     
     
         2 . The method of  claim 1 , wherein the CO 2  feed stream comprises CO 2  gas and water vapor, and wherein the precipitated salts are solvated by the water vapor and removed from the cathode compartment as solvated salts. 
     
     
         3 . The method of  claim 2 , wherein the CO 2  feed stream further comprises acid vapor. 
     
     
         4 . The method of  claim 1 , wherein the method comprises periodically injecting aqueous acid into the CO 2  feed stream. 
     
     
         5 . The method of  claim 1 , wherein the cathode endplate comprises recessed flow channels coated with a hydrophobic coating to prevent precipitation of the precipitated salts. 
     
     
         6 . The method of  claim 5 , wherein the hydrophobic coating is selected from the group consisting of parylene, acrylic resin, epoxy resin, polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polydimethylsiloxane, polyester, polyurethane, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein the cathode endplate comprises a removable plate with recessed flow channels, wherein the precipitated salts collect in the recessed flow channels and the removable plate is capable to be removed and cleaned while reducing the CO 2  feed stream at the cathode catalyst. 
     
     
         8 . The method of  claim 1 , wherein the CO 2  feed stream is supplied to the cathode compartment at a flow rate ranging from 0.02 to 0.1 sccm·cm 2 /mA. 
     
     
         9 . An apparatus for the electrochemical reduction of CO 2 , the apparatus comprising:
 a cathode compartment comprising:
 a cathode endplate and a cathode catalyst; 
 wherein the cathode endplate comprises a removable plate with recessed flow channels; and 
   an anode compartment comprising anolytes.   
     
     
         10 . The apparatus of  claim 9 , wherein the recessed flow channels are coated with a hydrophobic coating. 
     
     
         11 . The apparatus of  claim 10 , wherein the hydrophobic coating is selected from the group consisting of parylene, acrylic resin, epoxy resin, polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polydimethylsiloxane, polyester, polyurethane, and combinations thereof. 
     
     
         12 . A method for removing precipitated salts formed during the electrochemical reduction of CO 2 , the method comprising:
 providing the apparatus of  claim 9 ;   supplying a CO 2  feed stream to the cathode compartment;   reducing the CO 2  feed stream at the cathode catalyst to form a carbon species by applying a voltage to the device;   wherein upon applying the voltage to the device, a portion of the anolytes crossover from the anode compartment to the cathode compartment, forming precipitated salts; and   reducing accumulation of precipitated salts in the cathode compartment while reducing the CO 2  feed stream at the cathode catalyst.   
     
     
         13 . The method of  claim 12 , wherein the CO 2  feed stream comprises CO 2  gas and water vapor, and wherein the precipitated salts are solvated by the water vapor and removed from the cathode compartment as solvated salts. 
     
     
         14 . The method of  claim 13 , wherein the CO 2  feed stream further comprises acid vapor. 
     
     
         15 . The method of  claim 12 , wherein the method comprises periodically injecting aqueous acid into the CO 2  feed stream. 
     
     
         16 . The method of  claim 12 , wherein the apparatus is stable while reducing the CO 2  feed stream for continuous electrolysis with a current density ranging from 0 to 5000 mA cm −2 . 
     
     
         17 . The method of  claim 12 , wherein the recessed flow channels are coated with a hydrophobic coating. 
     
     
         18 . The method of  claim 17 , wherein the hydrophobic coating is selected from the group consisting of parylene, acrylic resin, epoxy resin, polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polydimethylsiloxane, polyester, polyurethane, and combinations thereof. 
     
     
         19 . The method of  claim 12 , wherein the precipitated salts collect in the removable plate with recessed flow channels and the removable plate may be removed and cleaned while reducing the CO 2  feed stream at the cathode catalyst. 
     
     
         20 . The method of  claim 12 , wherein the CO 2  feed stream is supplied to the cathode compartment at a flow rate ranging from 0.02 to 0.1 sccm·cm 2 /mA.