Interrelation between ink viscoelasticity and crack structure of fuel cell microporous layers

Cracks in the microporous layers of fuel cells greatly affect their performance. It is essential to understand the viscoelasticity of ink, the key precursor during MPL fabrication, to gain insights into crack formation and control. This work has comprehensively investigated ink rheology with different solid content and the resulting MPL crack structure from a theoretical and practical level. The network microstructure strength of the ink is evaluated by rheological measurements, and the interrelation between ink viscoelasticity and two distinct crack configurations is established. The detailed SEM characterization shows that an appropriate ink cohesive energy produces more intersected cracks within the MPL, while lower or higher cohesive energy is prone to unpenetrated and interlayer cracks. The range of CE in this study is 0.03-100 J/m3, the CE of ink is more likely to produce intersected cracks at about 10 J/m3. Moreover, the CE variation affects the PTFE distribution. A lower CE variation from 1 to 500 s-1 which is associated with the coating process promotes a homogeneous PTFE distribution.