WATER ELECTROLYZERS

A water electrolyzer comprising: a membrane having first and second opposed major surfaces, a thickness extending between the first and second major surfaces; a cathode comprising a first catalyst on the first major surface of the membrane; and an anode comprising a second catalyst on the second major surface of the membrane, wherein the membrane, if planar, has a length direction, an average length, a width direction, an average width, a thickness direction, and an average thickness, wherein the average length and the average width are each greater than the average thickness, wherein the average width is no greater than the average length, wherein the average thickness is defined between first and second major surfaces of the membrane, wherein the average length, the average width, and the average thickness define a membrane volume, wherein has the length direction, the width direction, and the thickness direction are each perpendicular to each other, wherein the membrane volume comprises at least one of metallic Pt or Pt oxide, wherein the membrane volume comprises at least 5 of alternating first and second regions across at least one plane in the membrane, wherein the first region has a first concentration within a 100 micrometer3 cube volume collectively of metallic Pt and Pt oxide that is at least 0.1 microgram/cm3, wherein the second region has a second concentration within a 100 micrometer3 cube volume collectively of metallic Pt and Pt oxide that is not greater than 0.01 microgram/cm3, and wherein the first concentration is at least 10 times greater than the second concentration.