Bimodal Behavior of Catalyst Layers Prepared By Electrospray: High Water Uptake and Superhydrophobicity

Electrosprayed catalyst layers (CLs) for electrodes of proton exchange membrane fuel cells (PEMFCs) combine high water vapor uptake with a superhydrophobic character. Such ‘bimodal behavior’ is the basis for their high performance as cathode in PEMFC, and must be explained in the light of the film morphology resulting from the electrospray deposition process. A microscopic analysis of the deposited films, covering different scales, reveals important differences in particles and ionomer distribution between the electrosprayed and sprayed layers. The resulting electrosprayed CL shows pore surfaces covered by dendritic structure that provide the superhydrophobic character. Other experimental evidences point to an specific interaction of the ionomer with the catalyst in electrosprayed films.