Methods of operation for systems for electrochemically generating chemical products

Abstract

Some aspects of the present disclosure are generally directed to systems for electrochemically generating compounds, for example, for generating hydrogen peroxide or other applications. In some cases, the systems may include electrodes containing a substrate comprising non-woven fibers comprising carbon, PTFE particles on the substrate, and/or an active material, for example, carbon particles, on the substrate and/or the PTFE. In some embodiments, the systems may generate and/or flow a two-phase solution over and/or through at least a portion of an electrode. Some systems using the electrode structures and/or two-phase solution may promote the formation of three-phase boundaries, and thus may facilitate the electrocatalytic generation of certain compounds at the three-phase boundaries. Still other aspects are directed to methods of making and/or using the systems, or the like.

1 . A method of electrochemically generating a compound, comprising:
 purging an electrode stack by flowing gas through an electrode stack;   flowing deionized water through the electrode stack;   flowing an electrolyte through the electrode stack for greater than or equal to 1 minute while an absolute magnitude of an applied current is less than or equal to 0.1 mA/cm 2 ;   increasing the absolute magnitude of the applied current density by an amount greater than or equal to 15 mA/cm 2  and less than or equal to 125 mA/cm 2  every 5 minutes until the applied current density reaches at least 150 mA/cm 2 ;   electrochemically generating a compound in the electrode stack and heating the electrode stack to at least 35 degrees C. while the applied current remains at least at 150 mA/cm 2 ; and   increasing the absolute magnitude of the applied current to at least 300 mA/cm 2 .   
     
     
         2 . The method of  claim 1 , wherein the compound is hydrogen peroxide. 
     
     
         3 . The method of  claim 1 , wherein heating the electrode stack comprises joule heating. 
     
     
         4 . The method of  claim 1 , wherein heating the electrode stack comprises heating the electrolyte solution. 
     
     
         5 . The method of  claim 4 , wherein heating the electrolyte solution comprises joule heating. 
     
     
         6 . The method of  claim 1 , wherein heating the electrolyte solution comprises using a resistive heating coil. 
     
     
         7 . The method of  claim 1 , wherein heating the electrolyte solution comprises using a heat exchanger. 
     
     
         8 . The method of  claim 1 , wherein an average temperature of the electrolyte solution is at least 35 degrees C. when flowing into and/or through the electrode stack. 
     
     
         9 . The method of  claim 1 , wherein the absolute magnitude of the applied current density is increased by less than or equal to 10 mA/cm 2 /min. 
     
     
         10 . The method of  claim 1 , wherein electrochemically generating a compound occurs at an electrode in the electrode stack, and wherein the electrode comprises a substrate including non-woven fibers comprising carbon. 
     
     
         11 . (canceled) 
     
     
         12 . The method of claim  11 , wherein the electrode further comprises a first hydrophobic polymer formed on at least a portion of the substrate. 
     
     
         13 . The method of  claim 10 , wherein the electrode further comprises a catalyst layer comprising a second hydrophobic polymer and/or an active material on at least a portion of the substrate. 
     
     
         14 . The method of  claim 12 , wherein the first hydrophobic polymer and/or the second hydrophobic polymer comprises polytetrafluoroethylene (PTFE) particles. 
     
     
         15 . (canceled) 
     
     
         16 . The method of  claim 13 , wherein the catalyst layer comprises an active material on at least a portion of the substrate, wherein the active material comprises carbon. 
     
     
         17 . The method of  claim 13 , wherein the active material comprises less than or equal to 0.01 wt % metal. 
     
     
         18 . The method of claim  11 , wherein the substrate comprises a carbon felt. 
     
     
         19 . A method of shutting down an electrode stack, comprising:
 electrochemically generating a compound in the electrode stack;   decreasing an absolute magnitude of an applied current to the electrode stack to less than or equal to 0.1 mA/cm 2 ;   flowing liquid through the electrode stack for greater than or equal to 1 minute while the absolute magnitude of the applied current is less than or equal to 0.1 mA/cm 2 ; and   flowing gas through the electrode stack to purge the electrode stack of liquid.   
     
     
         20 . The method of  claim 19 , further comprising flowing deionized (DI) water through the electrode stack, wherein the gas and the DI water are flowed through the electrode stack at the same time in the form of a two-phase solution. 
     
     
         21 . A method of cleaning an electrode stack, comprising:
 electrochemically generating a compound in the electrode stack;   decreasing an absolute magnitude of an applied current to the electrode stack to less than or equal to 0.1 mA/cm 2 ;   removing a precipitate from the electrode stack by flowing a solution comprising a reducing agent and/or a chelating agent for less than or equal to 5 minutes; and   flowing deionized (DI) water through the electrode stack for greater than or equal to 30 minutes.   
     
     
         22 - 37 . (canceled) 
     
     
         38 . The method of  claim 1 , wherein, during the increasing, the absolute magnitude of the applied current density is increased by 30 mA/cm 2  every 5 minutes until the applied current density reaches at least 150 mA/cm 2 .