Fuel cell having metalized gas diffusion layer

Abstract

A fuel cell is described and which includes an ion exchange membrane; an electrode positioned in ion exchanging relation relative to the ion exchange membrane; a gas diffusion layer borne by the electrode and having an outwardly facing surface; a porous metal coating comprising one or more elements selected from the periodic table of elements and which has an atomic number of less than 75, and which is positioned at least in partial covering relation relative to the outwardly facing surface of the gas diffusion layer; and a current collector forcibly disposed in ohmic electrical contact with the porous metal coating.

1 . A fuel cell comprising: 
 an ion exchange membrane;    an electrode positioned in ion exchanging relation relative to the ion exchange membrane;    a gas diffusion layer borne by the electrode and having an outwardly facing surface;    a porous metal coating comprising one or more elements selected from the periodic table of elements and which has an atomic number less than 75, and which is positioned at least in partial covering relation relative to the outwardly facing surface of the gas diffusion layer; and    a current collector forcibly disposed in ohmic electrical contact with the porous metal coating.    
   
   
       2 . A fuel cell as claimed in  claim 1 , and wherein the fuel cell is operational at temperatures of less than about 300 degrees C.  
   
   
       3 . A fuel cell as claimed in  claim 1 , and wherein the porous metal coating comprises an alloy, oxide, nitride or carbide.  
   
   
       4 . A fuel cell as claimed in  claim 1 , and wherein the porous metal coating is selected from the group of metals in the periodic table of elements having atomic numbers from 13 to 74.  
   
   
       5 . A fuel cell as claimed in  claim 1 , and wherein the ion exchange membrane has opposite anode and cathode sides, and wherein the gas diffusion layer and the porous metal coating are disposed on only one of the anode or cathode sides.  
   
   
       6 . A fuel cell as claimed in  claim 1 , and wherein the ion exchange membrane has opposite anode and cathode sides, and wherein the gas diffusion layer and the porous metal coating are disposed on both the anode and cathode sides.  
   
   
       7 . A fuel cell as claimed in  claim 1 , and wherein the ion exchange membrane has opposite anode and cathode sides, and wherein the gas diffusion layer is located on both the anode and cathode sides, and wherein the porous metal coating is positioned on only one of the anode or cathode sides.  
   
   
       8 . A fuel cell as claimed in  claim 1 , and wherein the gas diffusion layer has first and second portions, and where the first portion has a porosity and the second portion has a porosity which is greater than the first portion.  
   
   
       9 . A fuel cell as claimed in  claim 1 , and wherein the gas diffusion layer comprises: 
 a carbon fiber based sheet having a porosity, and wherein the outwardly facing surface has a topology, and wherein the porous metal coating substantially conforms to the topology.    
   
   
       10 . A fuel cell as claimed in  claim 1 , and wherein the gas diffusion layer comprises: 
 a carbon fiber based sheet having a porosity, and wherein the outwardly facing surface has a topology, and wherein the porous metal coating substantially conforms to the topology and is deposited in an amount of about 8 to about 150 milligrams of the porous metal per square centimeter of surface area.    
   
   
       11 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a topology, and wherein the porous metal coating substantially conforms to the topology and is deposited in an amount which causes the resulting gas diffusion layer to have an air impedance of about 23 to about 300 seconds Gurley.  
   
   
       12 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a topology, and wherein the porous metal coating substantially conforms to the topology, and is deposited in an amount of about 8 to about 150 milligrams of the porous metal per square centimeter of surface area.  
   
   
       13 . A fuel cell as claimed in  claim 1 , and wherein the porous metal coating is continuous.  
   
   
       14 . A fuel cell as claimed in  claim 1 , and wherein the porous metal coating is discontinuous.  
   
   
       15 . A fuel cell as claimed in  claim 1 , and wherein the porous metal coating is selected from the group of metals and their alloys, oxides, nitrides, and carbides which have a density of about 2.0 to about 19.0 grams per cubic centimeter.  
   
   
       16 . A fuel cell as claimed in  claim 1 , wherein the porous metal coating is selected from the group of metals consisting essentially of aluminum, titanium, nickel, iron, stainless steel, manganese, zinc, chromium, copper, zirconium, silver, and tungsten, and their alloys, nitrides, oxides and carbides.  
   
   
       17 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a surface area, and wherein the porous metal coating comprises nickel which is deposited in an amount of about 28 to about 150 milligrams per square centimeter of surface area.  
   
   
       18 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a surface area, and wherein the porous metal coating comprises aluminum which is deposited in an amount of about 8 to about 40 milligrams per square centimeter of surface area.  
   
   
       19 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a surface area, and wherein the porous metal coating has an average thickness of about 25 to about 400 micrometers.  
   
   
       20 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a surface area which defines a topology, and wherein the porous metal coating substantially conforms to the topology; and has an average thickness of about 25 to about 400 micrometers on the surface area of the gas diffusion layer; and wherein the gas diffusion layer and the metal coating have a combined air impedance of about 23 to about 300 seconds Gurley.  
   
   
       21 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a surface area, and wherein a contact resistance is established between the current collector and the adjacent porous metal coating, and wherein the contact resistance is expressed in milliohms per square centimeter of surface area, and the pressure applied by the current collector is expressed in pounds per square inch, and wherein the contact resistance and the pressure can each be mathematically expressed as a logarithm, and wherein the relationship of the logarithm of the contact resistance, and the logarithm of the pressure applied by the current collector is characterized by a line having a slope of about 0 to about negative 0.8.  
   
   
       22 . A fuel cell as claimed in  claim 1 , and wherein a contact resistance is established between the current collector and the adjacent porous metal coating, and wherein the contact resistance is substantially constant and independent of the force applied by way of the current collector.  
   
   
       23 . A fuel cell as claimed in  claim 1 , and wherein the outwardly facing surface of the gas diffusion layer has a surface area, and wherein a contact resistance is established between the current collector and the adjacent porous metal coating, and wherein the contact resistance is substantially constant when exposed to a pressure of about 3 to about 300 pounds per square inch by way of the current collector.  
   
   
       24 . A fuel cell as claimed in  claim 1 , and wherein the electrode, ion exchange membrane, and the gas diffusion layer, form a resulting membrane electrode diffusion layer assembly, and wherein, during fuel cell operation, the membrane electrode diffusion layer assembly produces a substantially constant electrical current when exposed to a pressure of about 3 to about 300 pounds per square inch by way of the current collector.  
   
   
       25 . A fuel cell as claimed in  claim 1 , and wherein the electrode, ion exchange membrane, and the gas diffusion layer form a resulting membrane electrode diffusion layer assembly, and wherein, during fuel cell operation, the membrane electrode diffusion layer assembly generates electrical current, and a contact resistance is established between the porous metal coating and the juxtaposed current collector, and wherein the current produced, and the contact resistance experienced, is substantially constant, and independent of the force applied by the current collector.  
   
   
       26 . A fuel cell as claimed in  claim 1 , and wherein the electrode, ion exchange membrane, and the gas diffusion layer, form a resulting membrane electrode diffusion layer assembly, and wherein the outwardly facing surface of the gas diffusion layer has a surface area having a topology and wherein the porous metal coating substantially conforms to the topology, and wherein during fuel cell operation, the membrane electrode diffusion layer assembly generates electrical current, and a contact resistance is established between the porous metal coating and the juxtaposed current collector, and wherein the current produced is substantially constant, and independent of the pressure applied by the current collector, and wherein the contact resistance is expressed in milliohms per square centimeter of surface area, and the pressure applied by the current collector is expressed in pounds per square inch of surface area, and wherein both the contact resistance and the pressure applied by the current collector can each be mathematically expressed as a logarithm, and wherein the relationship between the logarithm of the contact resistance and the logarithm of the pressure applied by the current collector is characterized by a line having a slope of about 0 to about negative 0.8.  
   
   
       27 . A fuel cell as claimed in  claim 1 , and wherein the electrode, ion exchange membrane, and gas diffusion layer form a resulting membrane electrode diffusion layer assembly, and wherein the outwardly facing surface of the gas diffusion layer has a surface area having a topology: and wherein the porous metal coating substantially conforms to the topology, and wherein the fuel cell is operational at temperatures of less than about 300 degrees C.; and wherein the porous metal coating has an average thickness across the outwardly facing surface area of the gas diffusion layer of about 25 to about 400 micrometers, and wherein the gas diffusion layer and the porous metal coating have a combined air impedance of about 23 to about 300 seconds Gurley, and wherein during fuel cell operation, the membrane electrode diffusion layer assembly generates electrical current, and a contact resistance is established between the porous metal coating and the juxtaposed current collector, and wherein the current produced is substantially constant and substantially independent of the pressure applied by the current collector, and wherein the contact resistance is expressed in milliohms per square centimeter of surface area, and the pressure applied by the current collector is expressed in pounds per square inch of surface area, and wherein both the contact resistance, and the pressure applied by the current collector can each be mathematically expressed as a logarithm, and wherein the relationship between the logarithm of the contact resistance, and the logarithm of the pressure applied by the current collector is characterized by a line having a slope of 0 to about negative 0.8.  
   
   
       28 . A fuel cell comprising: 
 an ion exchange membrane;    an electrode borne by the ion exchange membrane;    a gas diffusion layer having an outwardly facing surface area and which is borne by the electrode; and    a current collector forcibly disposed in ohmic electrical contact with the gas diffusion layer, and wherein a substantially force independent contact resistance is established between the current collector and the gas diffusion layer during fuel cell operation.    
   
   
       29 . A fuel cell as claimed in  claim 28 , and wherein the electrode, ion exchange membrane, and the gas diffusion layer, form a membrane electrode diffusion layer assembly, and wherein the membrane electrode diffusion layer assembly, during fuel cell operation, produces a substantially constant electrical current when exposed to a pressure of greater than about 3 pounds per square inch and less than about 300 pounds per square inch of surface area by way of the current collector.  
   
   
       30 . A fuel cell as claimed in  claim 28 , and wherein the contact resistance is substantially constant when exposed to a pressure of less than about 300 pounds per square inch of surface area by way of the current collector.  
   
   
       31 . A fuel cell as claimed in  claim 28 , and wherein the contact resistance is substantially constant when exposed to a pressure of greater than about 3 pounds per square inch, and less than about 300 pounds per square inch of surface area by way of the current collector.  
   
   
       32 . A fuel cell as claimed in  claim 28 , and wherein the ion exchange membrane and the gas diffusion layer are operational at fuel cell operating temperatures of less than about 300 degrees C.  
   
   
       33 . A fuel cell as claimed in  claim 28 , and wherein a porous metal coating is applied to the outwardly facing surface area, and which is disposed in ohmic electrical contact with the current collector.  
   
   
       34 . A fuel cell as claimed in  claim 28 , and wherein a porous metal coating is applied to the outwardly facing surface, and is further disposed in ohmic electrical contact with the current collector, and wherein the porous metal coating comprises one or more elements selected from the periodic table of elements and which has an atomic number of  13  to  74 .  
   
   
       35 . A fuel cell as claimed in  claim 28 , and wherein a porous metal coating is applied to the gas diffusion layer, and wherein the porous metal coating lies in ohmic electrical contact with the current collector, and wherein the contact resistance is expressed in milliohms per square centimeter of surface area, and the pressure is expressed in pounds per square inch of surface area, and wherein the contact resistance, and the pressure applied by the current collector can each be mathematically expressed as a logarithm, and wherein the relationship of the logarithm of the contact resistance, and the logarithm of the pressure applied by the current collector, is represented by a line having a slope of about 0 to about negative 0.8.  
   
   
       36 . A fuel cell as claimed in  claim 28 , and wherein the gas diffusion layer is a porous substrate which has a porous metal coating applied thereto.  
   
   
       37 . A fuel cell as claimed in  claim 36 , and wherein the porous substrate is a carbon fiber based sheet, and wherein the gas diffusion layer has an air impedance of less than about 300 seconds Gurley.  
   
   
       38 . A fuel cell as claimed in  claim 28 , and wherein the gas diffusion layer is a carbon fiber based sheet which has a topology, and wherein a porous metal layer substantially conforms to the topology.  
   
   
       39 . A fuel cell as claimed in  claim 28 , and wherein the gas diffusion layer is a carbon fiber based sheet having a topology, and wherein a porous metal layer substantially conforms to the topology, and wherein the gas diffusion layer and the porous metal layer have a combined air impedance of about 23 to about 300 seconds Gurley.  
   
   
       40 . A fuel cell as claimed in  claim 28 , and wherein the gas diffusion layer is a carbon fiber based sheet, and wherein a metal layer is deposited on the outwardly facing surface in an amount of about 8 to about 150 milligrams per square centimeter of surface area, and wherein the contact resistance is expressed in milliohms per square centimeter of surface area, and the pressure is expressed in pounds per square inch of surface area, and wherein the contact resistance and the pressure applied by the current collector, can each be mathematically expressed by a logarithm, and wherein the relationship between the logarithm of the contact resistance measured between the gas diffusion layer and the current collector, and the logarithm of the pressure applied by the current collector to the gas diffusion layer is characterized by a line having a slope of 0 to about negative 0.8.  
   
   
       41 . A fuel cell as claimed in  claim 28 , and wherein a porous metal layer is borne by the gas diffusion layer and positioned in ohmic electrical contact with the current collector, and wherein the current collector applies a pressure of about 3 to about 300 pounds per square inch of surface area, and further has a predetermined open area of about 10 to about 85 percent, and wherein the contact resistance established between the current collector and the adjacent metal layer is expressed in milliohms per square centimeter of surface area, and wherein the contact resistance, and the pressure applied by the current collector can each be mathematically expressed as a logarithm, and wherein the relationship of the logarithm of the contact resistance, and the logarithm of the pressure applied by the current collector is characterized by a line having a slope of about 0 to about negative 0.8.  
   
   
       42 . A fuel cell as claimed in  claim 28 , and wherein a metal layer is borne by the gas diffusion layer and disposed in ohmic electrical contact with the current collector, and wherein the metal layer is selected from the group of metals consisting essentially of aluminum, titanium, nickel, iron, stainless steel, manganese, zinc, chromium, copper, zirconium, silver, tungsten, and their respective nitrides, oxides, carbides and alloys.  
   
   
       43 . A fuel cell as claimed in  claim 28 , and wherein a porous metal layer is borne by the gas diffusion layer and oriented in ohmic electrical contact with the current collector, and wherein the porous metal layer is selected from the group of metals and their respective nitrides, oxides carbides and alloys which have a density of about 2.0 to about 19.0 grams per cubic centimeter.  
   
   
       44 . A fuel cell as claimed in  claim 28 , and wherein a nickel layer is borne by the gas diffusion layer and is oriented in ohmic electrical contact with the current collector, and wherein the nickel layer is deposited in an average amount equal to about 28 to about 150 milligrams per square centimeter of surface area of the gas diffusion layer.  
   
   
       45 . A fuel cell as claimed in  claim 28 , and wherein an aluminum layer is borne by the gas diffusion layer and is oriented in ohmic electrical contact with the current collector, and wherein the aluminum layer is deposited in an average amount of about 8 to about 40 milligrams per square centimeter of surface area of the gas diffusion layer.  
   
   
       46 . A fuel cell as claimed in  claim 28 , and wherein a metal layer is borne by the gas diffusion layer and disposed in ohmic electrical contact with the current collector, and wherein the metal layer has an average thickness of about 25 to about 400 micrometers.  
   
   
       47 . A fuel cell comprising: 
 an ion exchange membrane;    an electrode borne by the ion exchange membrane;    a gas diffusion layer borne by the ion exchange membrane; and    a current collector forcibly juxtaposed into ohmic electrical contact with the gas diffusion layer, and wherein a pressure independent contact resistance is established between the gas diffusion layer and the current collector, and wherein the fuel cell is operational at fuel cell operating temperatures of less than about 300 degrees C.    
   
   
       48 . A fuel cell comprising: 
 an ion exchange membrane;    an electrode borne by the ion exchange membrane;    a gas diffusion layer borne by the ion exchange membrane; and    a current collector forcibly juxtaposed relative to the gas diffusion layer, and wherein, during fuel cell operation, the gas diffusion layer, electrode, and the ion exchange membrane produce an electrical current which is substantially constant relative to the pressure applied by the current collector.    
   
   
       49 . A fuel cell comprising: 
 an ion exchange membrane;    an electrode borne by the ion exchange membrane;    a gas diffusion layer borne by the electrode and which has an outwardly facing surface area; and    a current collector forcibly juxtaposed relative to the gas diffusion layer, and wherein, during fuel cell operation, a contact resistance is created between the gas diffusion layer and the current collector and which is expressed in milliohms per square centimeter of surface area, and wherein pressure applied by the current collector is expressed in pounds per square inch of surface area, and wherein the contact resistance, and the pressure applied by the current collector can each be individually mathematically expressed as a logarithm, and wherein the relationship of the logarithm of the contact resistance, and the logarithm of the pressure applied by the current collector is defined by a line having a slope of about 0 to about a negative 0.8.    
   
   
       50 . A fuel cell comprising: 
 an ion exchange membrane;    an electrode disposed in at least partial covering relation relative to the ion exchange membrane;    a gas diffusion layer borne by the electrode and which has an outwardly facing surface area;    a porous metal coating applied on the outwardly facing surface area of the gas diffusion layer; and    a current collector juxtaposed relative to the porous metal coating, and wherein a pressure of less than about 300 pounds per square inch is applied by the current collector to the juxtaposed gas diffusion layer and porous metal coating, and which creates a substantially constant contact resistance, during fuel cell operation, between the porous metal coating and the current collector, and wherein the fuel cell, during operation, generates a substantially constant electrical current when exposed to a pressure of less than about 300 pounds per square inch by the current collector at operating temperatures of less than about 300 degrees C.