A new hydrophobic thin film catalyst layer for PEMFC

A new hydrophobic thin film catalyst layer (CL) was prepared by the decal method in this work. Polytetrafluoroethylene (PTFE) was introduced to the catalyst ink with 1 wt.% Nafion® ionomer as the hyperdispersant. Aluminum foil was adopted as the transferring medium which enabled the sintering process of PTFE. Then an appropriate amount of Nafion® ionomer was sprayed onto the CL for proton conduction. At last, the CL was transferred onto a Nafion® membrane and the catalyst-coated membrane (CCM) was formed. Contact angle measurement and mercury intrusion porosimetry test were conducted to characterize the hydrophobicity and porosity of the thin film CL. The results showed that PTFE addition favored the CL hydrophobicity and porosity. The optimal PTFE content was also deduced by comparing the fuel cell performance under different PTFE contents. Electrochemical analysis revealed that PTFE addition decreased the electrochemical active area (ECA) but enhanced the diffusion process in the CL.