This thesis investigates the design, functionality, and manufacturing optimization of Membrane Electrode Assemblies (MEAs) in Proton Exchange Membrane Fuel Cells (PEMFCs), with a special focus on Epago Technologies’ thermochemical deposition method for catalyst layers. After introducing the key challenges in global decarbonization and the role of PEMFCs in sectors such as transport, aviation, maritime, and residential energy, the thesis delves into the structural components of the fuel cell, emphasizing the catalytic layer. The core of the study is dedicated to the enhancement of catalytic activity through Pt-based alloys and nanostructures—such as core–shell and dealloyed configurations—supported by literature and theoretical models. This is followed by a detailed review of existing catalyst coating techniques, from manual brush painting to sputter deposition, culminating in the in-depth presentation of Epago’s patented thermochemical process.