Water electrolyzers

Abstract

A water electrolyzer comprising a membrane comprising at least one of metallic Pt or Pt oxide, a cathode, and an anode. The cathode comprises a first catalyst consisting essentially of both metallic Pt and Pt oxide. The anode comprising a second catalyst comprising at least 95 percent by weight of collectively metallic Ir and Ir oxide present, calculated as elemental Ir, based on the total weight of the second catalyst.

1 . A water electrolyzer comprising:
 a membrane having first and second opposed major surfaces and comprising at least one of metallic Pt or Pt oxide;   a cathode on the first major surface of the membrane, the cathode comprising a first catalyst consisting essentially of both metallic Pt and Pt oxide; and   an anode on the second major surface of the membrane, the anode comprising a second catalyst, wherein the second catalyst is a nanostructured thin film catalyst comprising at least 95 percent by weight of collectively metallic Ir and Ir oxide, calculated as elemental Ir, based on the total weight of the second catalyst, wherein at least one of metallic Ir or Ir oxide is present.   
     
     
         2 . The water electrolyzer of  claim 1 , wherein the second catalyst consists essentially of at least one of metallic Ir or Ir oxide. 
     
     
         3 . The water electrolyzer of  claim 1 , wherein the second catalyst further comprises at least one of metallic Pt or Pt oxide. 
     
     
         4 . The water electrolyzer of  claim 3 , wherein the second catalyst consists essentially of at least one of metallic Pt or Pt oxide and at least one of metallic Ir or Ir oxide. 
     
     
         5 . The water electrolyzer of  claim 3 , wherein the at least one of metallic Ir or Ir oxide and at least one of metallic Pt or Pt oxide have a collective weight ratio, calculated as elemental Ir and Pt, respectively, of at least 20:1 Ir to Pt. 
     
     
         6 . The water electrolyzer of  claim 1 , wherein the at least one of metallic Ir or Ir oxide of the second catalyst collectively has an areal density of at least 0.01 mg/cm 2 . 
     
     
         7 . The water electrolyzer of  claim 1 , wherein the membrane further comprises polymer electrolyte. 
     
     
         8 . The water electrolyzer of  claim 7 , wherein the polymer electrolyte is at least one of perfluorosulfonic acid or perfluorosulfonimide acid. 
     
     
         9 . The water electrolyzer of  claim 1 , wherein the at least one of metallic Pt or Pt oxide is collectively present in the membrane at a concentration in a range from 0.05 mg/cm 3  to 100 mg/cm 3 . 
     
     
         10 . The water electrolyzer of  claim 1 , wherein the at least one of metallic Pt or Pt oxide is distributed throughout the membrane. 
     
     
         11 . The water electrolyzer of  claim 1 , wherein the membrane has a thickness extending between the first and second major surfaces, and first, second, and third regions equally spaced across the thickness, wherein the first region is the closest region to the first major surface, wherein the second region is the closest region to the second major surface, wherein the third region is located between the first and second regions, wherein the first and third regions are each essentially free of both metallic Pt and Pt oxide, and wherein the second region comprises the at least one of metallic Pt or Pt oxide in the membrane. 
     
     
         12 . The water electrolyzer of  claim 1 , wherein the membrane has a thickness extending between the first and second major surfaces, wherein the thickness has a midpoint between the first and second major surfaces, a first region between the first major surface and the midpoint, and a second region between the second major surface and the midpoint, and wherein the first region comprises the at least one of metallic Pt or Pt oxide in the membrane and the second region is essentially free of both metallic Pt and Pt oxide. 
     
     
         13 . The water electrolyzer of  claim 1 , wherein the membrane has a thickness extending between the first and second major surfaces, wherein the thickness has a midpoint between the first and second major surfaces, a first region between the first major surface and the midpoint, and a second region between the second major surface and the midpoint, and wherein the first region is essentially free of both metallic Pt and Pt oxide and the second region comprises the at least one of metallic Pt or Pt oxide in the membrane. 
     
     
         14 . The water electrolyzer of  claim 1 , wherein the membrane has a thickness extending between the first and second major surfaces, wherein the thickness has a midpoint between the first and second major surfaces, wherein the at least one of metallic Pt or Pt oxide in the membrane is present in and only within 0.05 micrometer to 0.5 micrometer from the midpoint toward both the first and second major surfaces of the membrane. 
     
     
         15 . The water electrolyzer of  claim 1 , wherein the at least a portion of the at least one of metallic Pt or Pt oxide in the membrane is present on a support. 
     
     
         16 . A method of generating hydrogen and oxygen from water, the method comprising:
 providing a water electrolyzer of  claim 1 ;   providing water in contact with the anode; and   providing an electrical potential difference across the membrane with sufficient current to convert at least a portion of the water to hydrogen and oxygen on the cathode and anode, respectively.