Membrane electrode assembly for a fuel cell, method for preparing the membrane electrode assembly, fuel cell system and vehicle

A membrane electrode assembly for a fuel cell, comprising

• a membrane (12),
• a catalyst layer (16) and
• a gas diffusion layer (14),
• wherein the catalyst layer (16) has a first side (18) facing the membrane (12) and a second side (20) facing the gas diffusion layer (14),
• wherein in the catalyst layer (16) an ionomer content increases towards the membrane,
• wherein the catalyst layer (16) comprises
• a first sublayer (22) in which supported catalyst particles (26) are coated with a first ionomer (28), and
• a second sublayer (24) comprising particles of a second ionomer (32) free of catalyst, the second sublayer (24) being closer to the membrane (12) than the first sublayer (22), the first sublayer (22) being closer to the gas diffusion layer (12) than the second sublayer (24),
• wherein pores (30) are present at least between the coated catalyst particles (26) and also between the particles of the second ionomer (32),
• wherein a porosity of the catalyst layer (16) increases from the first side (18) towards the second side (20) of the catalyst layer (16), and
• wherein the first and/or the second ionomer is/are a mixture of an ionomer and one or more polymers.