Effect of Dispersion Method on Ink Rheology and Microstructure of Microporous Layer for PEMFCs

In the modern design of proton exchange membrane fuel cells (PEMFCs), a microporous layer (MPL) is often introduced between the gas diffusion layer and catalyst layer to facilitate water management and reduce contact resistance. In this study, an experimental investigation of MPL fabrication, particularly on ink preparation, is carried out to assess the relationship between ink properties and MPL’s microstructure. Two dispersion methods for ink preparation, i.e., sonication and ball-milling, are employed. Rheological and agglomerate size measurements of the inks are performed. Structural properties of the MPL are characterized by the Brunauer–Emmett–Teller method. The MPL inks prepared by ball-milling and sonication dispersion are found to have different rheological properties. The viscosity of ball-milled inks is around 20 mPa·s, whereas for sonicated inks it is about one order of magnitude lower. The surface cracks of the MPL by ball-milling appear to be more extensive and fewer in number than those by sonication. A distinct layer structure forms when the inks are dispersed by ball-milling, whereas sonicated inks penetrate the gas diffusion substrate. The MPL fabricated by a ball-milled ink for 2 h has the most uniform microstructural characteristics among the cases tested. Characterization techniques are employed to investigate MPLs made using different dispersion methods and spray-coating. Rheological properties of microporous layer inks prepared with ball-milling and sonication are compared. Morphology and microstructure of microporous layers made using inks prepared by different dispersion methods are analyzed.