Gas diffusion electrode suitable for use in carbon dioxide electrolyzer and methods for making the same

Abstract

Gas diffusion electrode suitable for use in carbon dioxide electrolyzer and methods for making the same. According to one embodiment, the gas diffusion electrode may include a gas diffusion layer and a catalyst layer coupled to the gas diffusion layer. The gas diffusion layer, in turn, may include an electron-conductive domain and a non-conductive hydrophobic domain. The electron-conductive domain includes a plurality of pores. The non-conductive hydrophobic domain randomly occupies a portion of the volume of the pores of the electron-conductive domain and is, itself, sufficiently porous to permit gas transport through the electron-conductive domain, for example, by incompletely filling the pores, thereby leaving spaces in the pores, and/or by being made of an inherently porous material. The electron-conductive domain may be in the form of a metal mesh, a carbon paper, or similar structures. The non-conductive hydrophobic domain may be in the form of sintered polymer particles.

What is claimed is: 
     
         1 . A gas diffusion electrode suitable for use in a carbon dioxide electrolyzer, the gas diffusion electrode comprising:
 (a) a gas diffusion layer, the gas diffusion layer comprising
 (i) an electron-conductive domain, the electron-conductive domain having a thickness and comprising a plurality of pores, and 
 (ii) a non-conductive hydrophobic domain, the non-conductive hydrophobic domain having a thickness ranging from about 10% to about 100% of the thickness of the electron-conductive domain, the non-conductive hydrophobic domain randomly occupying a portion of the volume of the pores of the electron-conductive domain, the non-conductive hydrophobic domain being porous to permit gas transport through the gas diffusion layer; and 
   (b) a catalyst layer, the catalyst layer being coupled to the gas diffusion layer.   
     
     
         2 . The gas diffusion electrode as claimed in  claim 1  wherein the non-conductive hydrophobic domain comprises at least one of an ether polymer, an acrylic polymer, a fluorocarbon polymer, a polystyrene polymer, a poly(vinyl chloride) polymer, and a poly(N-vinylpyrrolidone) polymer. 
     
     
         3 . The gas diffusion electrode as claimed in  claim 1  wherein the non-conductive hydrophobic domain comprises at least one of a fiber, a particle, a pellet, and a rod. 
     
     
         4 . The gas diffusion electrode as claimed in  claim 3  wherein the non-conductive hydrophobic domain comprises a particle and wherein the particle has a size ranging from about 1 nm to about 1 mm. 
     
     
         5 . The gas diffusion electrode as claimed in  claim 4  wherein the non-conductive hydrophobic domain has a size ranging from about 5 nm to about 100 μm. 
     
     
         6 . The gas diffusion electrode as claimed in  claim 3  wherein the non-conductive hydrophobic domain comprises at least one of a fiber and a rod and wherein the non-conductive hydrophobic domain has a diameter ranging from about 1 nm to about 1 mm and a length ranging from nanometer to centimeter scale. 
     
     
         7 . The gas diffusion electrode as claimed in  claim 6  wherein the non-conductive hydrophobic domain has a diameter ranging from about 5 nm to about 100 μm. 
     
     
         8 . The gas diffusion electrode as claimed in  claim 1  wherein the electron-conductive domain comprises carbon, wherein the non-conductive hydrophobic domain has a mass, wherein the electron-conductive domain has a mass, and wherein the mass of the non-conductive hydrophobic domain ranges from about 30 wt % to about 600 wt % of the mass of the electron-conductive domain. 
     
     
         9 . The gas diffusion electrode as claimed in  claim 1  wherein the electron-conductive domain comprises at least one of carbon, copper, iron, stainless steel, silver, gold, nickel, aluminum, molybdenum, zinc, titanium, and brass. 
     
     
         10 . The gas diffusion electrode as claimed in  claim 1  wherein the electron-conductive domain comprises at least one of a paper, a foam, a felt, a sinter, a cloth, and a mesh. 
     
     
         11 . The gas diffusion electrode as claimed in  claim 1  wherein the electron-conductive domain is coated with at least one hydrophobic polymer with a loading ranging from about 0.1 wt % to about 40 wt % of the electron-conductive domain. 
     
     
         12 . The gas diffusion electrode as claimed in  claim 1  wherein the electron-conductive domain has a thickness ranging from about 0.5 μm to about 2 mm. 
     
     
         13 . The gas diffusion electrode as claimed in  claim 1  further comprising an interlayer, the interlayer being disposed between and in direct contact with each of the gas diffusion layer and the catalyst layer, the interlayer being porous and electron-conductive. 
     
     
         14 . The gas diffusion electrode as claimed in  claim 13  wherein the interlayer has a thickness ranging from about 5 nm to about 30 μm. 
     
     
         15 . The gas diffusion electrode as claimed in  claim 13  wherein the interlayer comprises at least one of carbon, copper, iron, stainless steel, silver, gold, nickel, aluminum, molybdenum, zinc, titanium, and brass. 
     
     
         16 . The gas diffusion electrode as claimed in  claim 13  wherein the interlayer is coated with one or more hydrophobic materials with a weight ratio of about 5 wt % to about 40 wt % of the interlayer. 
     
     
         17 . The gas diffusion electrode as claimed in  claim 13  wherein the interlayer comprises a mixture of electron-conductive particles and hydrophobic polymer particles. 
     
     
         18 . The gas diffusion electrode as claimed in  claim 17  wherein the hydrophobic polymer particles are present in the interlayer at a mass ratio ranging from about 5 wt % to about 200 wt % of the electron-conductive material particles. 
     
     
         19 . The gas diffusion electrode as claimed in  claim 1  wherein the catalyst layer comprises at least one of copper, silver, gold, carbon, bismuth, iron, boron, nitrogen, oxygen, fluorine, aluminum, silicon, phosphorus, sulfur, chromium, manganese, cobalt, nickel, zinc, gallium, selenium, molybdenum, ruthenium, rhodium, palladium, iridium, and platinum. 
     
     
         20 . The gas diffusion electrode as claimed in  claim 1  wherein the non-conductive hydrophobic domain comprises a porous hydrophobic particle. 
     
     
         21 . The gas diffusion electrode as claimed in  claim 20  wherein the porous hydrophobic particle has a particle size of about 1 nm to about 1 mm. 
     
     
         22 . The gas diffusion electrode as claimed in  claim 21  wherein the porous hydrophobic particle has at least one internal pore, with a pore diameter ranging from about 50 nm to about 5 μm. 
     
     
         23 . The gas diffusion electrode as claimed in  claim 20  wherein the porous hydrophobic particle is made by cryo-milling a bulk quantity of a porous material into powder. 
     
     
         24 . The gas diffusion electrode as claimed in  claim 20  wherein the porous hydrophobic particle comprises at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyvinyl chloride (PVC). 
     
     
         25 . A method of fabricating a gas diffusion electrode, the method comprising the steps of:
 (a) forming a gas diffusion layer, wherein said gas diffusion layer forming comprises
 providing a slurry, the slurry comprising at least one hydrophobic material and at least one organic solvent; 
 providing an electron-conductive substrate, the electron-conductive substrate having a thickness and comprising a plurality of pores; 
 loading the slurry into the pores of the electron-conductive substrate; and 
 sintering the slurry, whereby the solvent evaporates, forming a non-conductive hydrophobic domain within the pores of the electron-conductive substrate, the non-conductive hydrophobic domain having a thickness ranging from about 50% to about 100% of the thickness of the electron-conductive domain, the non-conductive hydrophobic domain configured to permit gas transport through the electron-conductive substrate; and 
   (b) positioning a catalyst layer over the gas diffusion layer.   
     
     
         26 . The method as claimed in  claim 25  wherein the loading step comprises one of screen printing, doctor blade coating, slot-die coating, vacuum filtration coating, and airbrush coating. 
     
     
         27 . The method as claimed in  claim 26  wherein the slurry further comprises at least one of water and one or more binders. 
     
     
         28 . The method as claimed in  claim 26  wherein the loading step comprises airbrush coating and wherein the airbrush coating is conducted at a pressure ranging from about 0.5 bar to about 15 bar. 
     
     
         29 . The method as claimed in  claim 28  wherein the pressure ranges from about 2 bar to about 6 bar. 
     
     
         30 . The method as claimed in  claim 25  wherein the sintering step is performed at a temperature no greater than the melting point of the at least one hydrophobic material. 
     
     
         31 . The method as claimed in  claim 30  wherein the temperature is about 0° C. to about 50° C. below the melting point of the at least one hydrophobic material. 
     
     
         32 . The method as claimed in  claim 25  wherein the sintering step is performed at a pressure ranging from about 0 lb. to about 5000 lbs. 
     
     
         33 . The method as claimed in  claim 25  further comprising the step of positioning an interlayer directly between the catalyst layer and the electron-conductive substrate. 
     
     
         34 . The method as claimed in  claim 33  wherein the interlayer positioning step comprises at least one of spraying, screen printing, doctor blade coating, vacuum filtration coating, compression coating, and slot-die coating. 
     
     
         35 . A gas diffusion electrode made by the method of  claim 25 . 
     
     
         36 . A method of fabricating a gas diffusion electrode, the method comprising the steps of:
 (a) forming a gas diffusion layer, wherein said gas diffusion layer forming comprises
 providing at least one non-conductive hydrophobic polymer; 
 providing at least one electron-conductive material; 
 mixing the at least one non-conductive hydrophobic polymer and the at least one electron-conductive material to form a mixture; 
 extruding the mixture to form a sheet; 
 stretching the sheet at a temperature below the melting point of the at least one non-conductive hydrophobic polymer to form pores for gas transport through the sheet; and 
   (b) positioning a catalyst layer over the gas diffusion layer.   
     
     
         37 . The method as claimed in  claim 36  wherein the stretching comprises at least one of uniaxial stretching and biaxial stretching of the sheet. 
     
     
         38 . The method as claimed in  claim 36  wherein a mass ratio of the at least one electron-conductive material to the at least one non-conductive hydrophobic polymer ranges from about 15 wt % to about 300 wt %. 
     
     
         39 . The method as claimed in  claim 38  wherein the mass ratio is from about 50 wt % to about 200 wt %. 
     
     
         40 . The method as claimed in  claim 36  wherein the at least one electron-conductive material is one or more of carbon, copper, iron, stainless steel, silver, gold, nickel, aluminum, molybdenum, zinc, titanium, and brass. 
     
     
         41 . The method as claimed in  claim 36  wherein the at least one electron-conductive material is one or more of a fiber, a particle, a pellet, and a rod. 
     
     
         42 . The method as claimed in  claim 41  wherein the at least one electron-conductive material has a particle size ranging from about 1 nm to about 1 mm. 
     
     
         43 . The method as claimed in  claim 41  wherein the at least one electron-conductive material is at least one of a fiber and a rod and wherein the at least one electron-conductive material has a diameter ranging from about 1 nm to about 1 mm and a length ranging from the nanometer scale to the centimeter scale. 
     
     
         44 . The method as claimed in  claim 36  wherein the temperature is the melting point temperature of the at least one non-conductive hydrophobic polymer. 
     
     
         45 . The method as claimed in  claim 36  wherein the mixture further comprises a lubricating agent and a pore former. 
     
     
         46 . The method as claimed in  claim 36  wherein the stretching comprises stretching at a ratio ranging from about 2:1 to about 40:1. 
     
     
         47 . A gas diffusion electrode made by the method of  claim 36 . 
     
     
         48 . A method of fabricating a gas diffusion electrode, the method comprising the steps of:
 (a) forming a gas diffusion layer, wherein said gas diffusion layer forming comprises
 providing a first gas diffusion layer piece, the first gas diffusion layer piece being porous and electron-conductive; 
 providing a second gas diffusion layer piece, the second gas diffusion layer piece being porous, non-conductive and hydrophobic, wherein the first gas diffusion layer piece and the second gas diffusion layer piece are complementarily shaped to mate with one another in the same plane; and 
 mating together the first gas diffusion layer piece and the second gas diffusion layer piece; and 
   (b) positioning a catalyst layer over the gas diffusion layer.   
     
     
         49 . The method as claimed in  claim 48  wherein the first gas diffusion layer piece and the second gas diffusion layer piece form an interdigitated construction. 
     
     
         50 . The method as claimed in  claim 48  wherein the first gas diffusion layer piece comprises a transverse opening and wherein the second gas diffusion layer piece is dimensioned to mate with the transverse opening. 
     
     
         51 . The method as claimed in  claim 48  wherein the gas diffusion layer has a uniform distribution of one or more electron-conductive areas and one or more non-conductive, hydrophobic areas. 
     
     
         52 . The method as claimed in  claim 48  wherein each of the first gas diffusion layer piece and the second gas diffusion layer piece has an area and wherein a ratio of the areas of the first and second gas diffusion layer pieces ranges from about 1:2, respectively, to about 2:1, respectively. 
     
     
         53 . The method as claimed in  claim 48  wherein the first gas diffusion layer piece comprises at least one of carbon paper, metal foam, metal mesh, and metal paper. 
     
     
         54 . The method as claimed in  claim 48  wherein the second gas diffusion layer piece comprises at least one of a fluoropolymer film and a polyvinyl chloride film. 
     
     
         55 . The method as claimed in  claim 48  wherein the first and second gas diffusion layer pieces have similar thicknesses. 
     
     
         56 . A gas diffusion electrode made by the method of  claim 48 . 
     
     
         57 . A method for fabricating a gas diffusion electrode, the method comprising the steps of:
 (a) forming a gas diffusion layer, wherein said gas diffusion layer forming comprises
 providing a porous electron-conductive substrate, the porous electron-conductive substrate having an outer surface; 
 preparing a slurry, the slurry comprising a random mixture of at least one electron-conductive material, at least one non-conductive hydrophobic polymer material, and at least one solvent; 
 coating the outer surface of the porous electron-conductive substrate with the slurry, which, upon drying, forms a porous coating on the outer surface of the porous electron-conductive substrate; and 
   (b) positioning a catalyst layer over the porous coating of the gas diffusion layer.   
     
     
         58 . The method as claimed in  claim 57  wherein a volume ratio of the at least one electron-conductive material to the at least one non-conductive hydrophobic polymer material ranges from about 9:1, respectively, to about 1:3, respectively. 
     
     
         59 . The method as claimed in  claim 58  wherein the porous coating has a thickness ranging from about 1 μm to about 200 μm. 
     
     
         60 . The method as claimed in  claim 58  wherein the at least one electron-conductive material has a particle size from about 10 nm to about 5 μm. 
     
     
         61 . The method as claimed in  claim 58  wherein the at least one non-conductive hydrophobic polymer material has a particle size of from about 20 nm to about 200 μm. 
     
     
         62 . The method as claimed in  claim 58  wherein the coating step comprises at least one of doctor blade coating, slot-die coating, bar-coating, and screen printing. 
     
     
         63 . The method as claimed in  claim 58  further comprising, prior to the coating step, pre-coating the electron-conductive substrate with at least one hydrophobic material to a weight percentage of about 0.1 wt % to about 40 wt %. 
     
     
         64 . A gas diffusion electrode made by the method of  claim 57 .