Liquid water uptake and contact angle measurement of proton exchange membrane fuel cell (PEMFC) electrodes

© 2018 by The Electrochemical Society. All rights reserved. In this work, capillary rise experiments were performed to assess the wetting properties of free-standing proton exchange membrane fuel cell catalyst layers (CLs) with several ionomer chemistries (equivalent weight-EW-ranging from 540 to 1115). The samples were attached to a micro-balance and then immersed into liquid water to (i) measure the mass gain from the liquid uptake and (ii) estimate the (external) contact angle to water. The results showed that the ionomer EW had an impact on the CL wettability. Specifically, a highly hydrophobic behavior was observed at high ionomer EW (i.e., 1115): 173° contact angle to water. More hydrophilic behavior was observed at low ionomer EW (i.e., 540): 107° contact angle to water. For an intermediate range of ionomer EW (i.e., from 620 to 1100), minimal variation in the CLs wetting properties was observed at an average contact angle of 160°