Review of catalyst-deposition techniques for PEMFC electrodes

Catalyst deposition has been a significant part of fuel-cell manufacturing since their entry into mass-production industry, especially to limit the inevitable use of critical raw materials. This review focuses on a variety of techniques that may be applied towards a controlled deposition onto PEMFC substrates. The current manufacturing process consists of depositing inks onto decal-transfer carrier films, then bound to the membrane by heat and pressure. Among the conventional methods for ink deposition, gravure printing and screen printing appear the most promising. The former consists of engraving the desired image areas into the surface of a cylinder; the ink lies ultimately within engraved cells and is transferred from those cells to the substrate. In screen printing, the ink is forced through a fine fabric screen and flows through the open meshes, according to the desired pattern. Additive layer manufacturing and inkjet printing are also considered as prominent alternatives, thanks to their higher ink-deposition control onto the substrate, mainly through the drop-on-demand approach. The need for achieving higher flexibility and quality in MEA production seems to favor inkjet printing and additive layer manufacturing, able to lead to a significantly higher catalyst-layer homogeneousness. However, they require assessment of ink rheological properties and formulation.