| CPC H01M 8/1004 (2013.01) [C23C 14/35 (2013.01); C25B 9/23 (2021.01); C25B 11/031 (2021.01); C25B 11/053 (2021.01); C25D 3/50 (2013.01); H01M 4/8657 (2013.01); H01M 4/881 (2013.01); H01M 4/8871 (2013.01); H01M 4/8892 (2013.01); H01M 4/8896 (2013.01); H01M 4/92 (2013.01); H01M 4/926 (2013.01); H01M 4/96 (2013.01)] | 8 Claims |

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1. A membrane-electrode-assembly (20) for a proton exchange membrane (PEM) fuel cell or an electrolyzer comprising the following components:
a first gas-permeable electrode layer (5, 5-1),
a first self-supporting nanoporous catalyst layer (4, 4-1) comprising a noble metal (2),
a membrane (10),
wherein the first self-supporting nanoporous catalyst layer (4, 4-1) extends between the first gas-permeable electrode layer (5, 5-1) and the membrane (10), characterized in that the first self-supporting nanoporous catalyst layer (4, 4-1) is formed by a plurality of grains (100) of a first catalyst compound, wherein gaps (101) are formed in between the grains (100) such as to form an increased surface area of the first self-supporting nanoporous catalyst layer (4, 4-1) for enhancing catalytic reactions, and wherein a median value of an equivalent spherical diameter of the grains is in the range of 450 nm to 750 nm, while a range of the equivalent spherical diameters of the grains is in the range of 200 nm to 1,300 nm, wherein the assembly (20) is formed using a method for manufacturing a catalytically-active membrane-electrode-assembly (20) with one or more electrodes, the method comprising at least the steps of:
i) depositing a heterogenous layer (3) on a substrate (5), the heterogeneous layer (3) comprising a base metal (1) and a noble metal (2) heterogeneously distributed in the heterogenous layer (3), wherein the noble metal comprises a plurality of grains, wherein a median value of an equivalent spherical diameter of the grains is in the range of 450 nm to 750 nm, while a range of the equivalent spherical diameters of the grains is in the range of 200 nm to 1,300 nm;
ii) leaching of the base metal (1) out of the heterogeneous layer (3), such that a first self-supporting nanoporous catalyst layer (4) comprising the noble metal (2) is formed on the substrate (5);
iii) adding at least one kind of proton-conductive ionomers (40) and/or at least one kind of hydrophobic particles (41) and/or an ionic liquid (42) to the first self-supporting nanoporous catalyst layer (4); and
iv) forming the catalytically-active membrane-electrode-assembly (20) by attaching the self-supporting nanoporous catalyst layer (4) to a first side of a membrane (10), such that a catalytically-active membrane-electrode-assembly (20) with one electrode is formed.
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