Conductive all-polymer gas diffusion layers for electrochemical devices

Abstract

A method of forming a gas diffusion material layer (GDL) includes depositing a metallic layer over a porous polytetrafluoroethylene (PTFE) layer, oxidizing 3,4-ethylenedioxythiophene (EDOT) over the metallic layer, and forming a porous poly(3,4-ethylenedioxythiophene) (PEDOT) layer over the porous PTFE layer. The porous PEDOT layer directly contacts the porous PTFE layer. The resulting PEDOT-PTFE GDL combines electrical conductivity with hydrophobicity and gas permeability, enabling efficient electrochemical conversion processes, particularly carbon dioxide reduction reaction. The PEDOT-PTFE GDL can be used in electrochemical systems comprising an electrochemical reactor and a catalyst layer supported on the PEDOT-PTFE GDL, to provides stable, selective, and efficient CO 2 reduction performance across alkaline, neutral, and acidic electrolytes. Compared with carbon-based GDLs, the PEDOT-PTFE electrodes exhibit reduced hydrogen evolution, high product selectivity, and durability under high current operation.

I/We claim: 
     
         1 . A method of forming a gas diffusion layer, comprising:
 (a) depositing a metallic layer over a porous polytetrafluoroethylene (PTFE) layer;   (b) oxidizing 3,4-ethylenedioxythiophene (EDOT) over the metallic layer; and   (c) forming a porous poly(3,4-ethylenedioxythiophene) (PEDOT) layer over the porous PTFE layer, wherein the porous PEDOT layer directly contacts the porous PTFE layer.   
     
     
         2 . The method of  claim 1 , wherein the depositing of the metallic layer onto the porous PTFE layer includes initiating a thermal evaporation process. 
     
     
         3 . The method of  claim 1 , wherein the oxidizing of the EDOT over the metallic layer includes initiating electrochemical oxidation to initiate polymerization. 
     
     
         4 . The method of  claim 1 , wherein the forming of the porous PEDOT layer over the porous PTFE layer includes dissolving the metallic layer. 
     
     
         5 . The method of  claim 4 , wherein the dissolving of the metallic layer includes applying one or more chemical agents to the metallic layer. 
     
     
         6 . The method of  claim 3 , wherein the metallic layer includes gold. 
     
     
         7 . The method of  claim 1 , wherein the forming of the porous PEDOT layer over the porous PTFE layer includes initiating an aqua regia process to dissolve the gold. 
     
     
         8 . The method of  claim 1 , wherein the porous PEDOT layer comprises PEDOT doped with counterions comprising at least one of PF 6   − , ClO 4   − , CF 3 SO 3   − , or BF 4   − . 
     
     
         9 . The method of  claim 3 , wherein the EDOT is polymerized in an electrolyte with counterions comprising at least one of PF 6   − , ClO 4   − , CF 3 SO 3   − , or BF 4 . 
     
     
         10 . The method of  claim 3 , wherein the polymerization includes applying a three-electrode configuration consisting of a working electrode, a counter electrode and a reference electrode, wherein the working electrode is the porous PTFE layer coated with the metallic layer, the counter electrode is a carbon paper, and the reference electrode is Ag/AgCl in saturated KCl. 
     
     
         11 . The method of  claim 10 , wherein the polymerization includes immersing the electrodes in an electrolyte with counterions comprising at least one of PF 6   − , ClO 4   − , CF 3 SO 3   − , or BF 4   − . 
     
     
         12 . The method of  claim 11 , wherein the polymerization includes applying a potential of about 2.1 V versus Ag/AgCl or 2 mA until reaching a targeted charge density. 
     
     
         13 . The method of  claim 1 , wherein the metallic layer has a thickness of about 150 nm. 
     
     
         14 . The method of  claim 1 , wherein the porous PEDOT layer has a thickness of about 1 μm. 
     
     
         15 . The method of  claim 1 , wherein fibers of the PEDOT layer have an average width of about 20 nm. 
     
     
         16 . A method of electrochemically reducing CO 2 , comprising:
 (a) providing an electrode comprising a poly(3,4-ethylenedioxythiophene) (PEDOT)-polytetrafluoroethylene (PTFE) gas diffusion layer, wherein the PEDOT-PTFE gas diffusion layer comprises a porous PEDOT layer formed over a porous polytetrafluoroethylene PTFE substrate, wherein the porous PEDOT layer directly contacts the porous PTFE layer;   (b) introducing CO 2  to the electrode; and   (c) applying a current density of at least about 100 mA/cm 2  to reduce CO 2 .   
     
     
         17 . The method of  claim 16 , wherein the method is performed in an alkaline, neutral, or acidic electrolyte. 
     
     
         18 . The method of  claim 16 , wherein the electrode comprises metal nanoparticles supported on the PEDOT-PTFE gas diffusion layer. 
     
     
         19 . An electrochemical system, comprising:
 an electrochemical reactor;   an electrode comprising a poly(3,4-ethylenedioxythiophene) (PEDOT)-polytetrafluoroethylene (PTFE) gas diffusion layer, wherein the PEDOT-PTFE gas diffusion layer comprises a porous PEDOT layer formed over a porous PTFE substrate, wherein the porous PEDOT layer directly contacts the porous PTFE layer; and   a catalyst layer supported on the PEDOT-PTFE gas diffusion layer.   
     
     
         20 . The system of  claim 19 , wherein the catalyst layer comprises metal nanoparticles, and the reactor is configured for CO 2  reduction.