Gas Diffusion Electrodes, Membrane-Electrode Assemblies and Method for the Production Thereof
A method for forming a patterned noble metal coating on a gas diffusion medium substantially free of ionomeric components comprising subjecting an electrically conductive web with a patterned mask overlaid thereto to a first ion beam having an energy not higher than 500 eV, and to a second beam having an energy of at least 500 eV, containing the ions of at least one noble metal and a gas diffusion electrode.
1 - 18 . (canceled)
19 . A method for forming a patterned noble metal coating on a gas diffusion medium substantially free of ionomeric components comprising subjecting an electrically conductive web with a patterned mask overlaid thereto to a first ion beam having an energy not higher than 500 eV, and to a second beam having an energy of at least 500 eV, containing the ions of a least one noble metal.
20 . The method of claim 19 , wherein said patterned mask is a thin metal sheet or polymer film provided with a geometrical pattern of openings.
21 . The method of claim 20 , wherein said thin metal sheet is chemically etched.
22 . The method of claim 20 , wherein the distance between the centers in adjacent couples of openings is between 0.02 and 0.5 cm.
23 . The method of claim 19 , wherein said patterned mask has an open ratio between 30 and 80%.
24 . The method of claim 19 , wherein said patterned mask is a polygonal grid.
25 . The method of claim 24 , wherein said polygonal grid comprises equally spaced polygonal openings, optionally hexagonal openings, with a circular filled center, and the resulting patterned noble metal coating is comprised of equally spaced polygons, optionally hexagons, having a round hole center.
26 . The method of claim 19 , wherein said patterned noble metal coating has a thickness of between 5 and 250 nm and a loading of from 0.01 to 0.3 mg/cm 2 .
27 . The method of claim 19 , wherein said first ion beam has an energy comprised of between 100 and 500 eV and said second ion beam has an energy comprised of between 500 and 5,000 eV.
28 . The method of claim 19 , wherein said at least one noble metal is platinum.
29 . A gas diffusion electrode comprising an electrically conductive web, a non catalyzed gas diffusion layer comprising at least one electroconductive filler and at least one optionally fluorinated binder, and a patterned noble metal coating obtained by the method of claim 19 .
30 . The gas diffusion electrode of claim 29 , wherein said electroconductive filler comprises carbon particles,
31 . The gas diffusion electrode of claim 29 , wherein said electroconductive filler is acetylene black carbon particles.
32 . The gas diffusion electrode of claim 29 , wherein said electroconductive filler is furnace black carbon particles
33 . The gas diffusion electrode of claim 29 , wherein said electroconductive filler comprises multiple layers of acetylene black and multiple layers of furnace black carbon particles.
34 . The gas diffusion electrode of claim 30 , wherein said gas diffusion layer has a smoothness of at least 1000 Gurley-seconds.
35 . A member-electrode assembly comprising at least one gas diffusion electrode of claim 29 and an ion-exchange membrane.
36 . The membrane-electrode assembly of claim 34 , wherein said at least one gas diffusion electrode and said ion-exchange membrane are mutually bonded by hot pressing.