An ingenious design of nanoporous nafion film for enhancing the local oxygen transport in cathode catalyst layers of PEMFCs

An intractable issue accompanied with continuously reducing the Pt loading in cathodes of polymer electrolyte membrane fuel cells (PEMFCs) deals with a sudden increase in the oxygen transport resistance in cathode catalyst layers (CCLs), especially the local oxygen transport resistance that results from oxygen permeating through Nafion ultrathin film covering on Pt surface. Herein, we successfully regulate a nanoscale distribution of Nafion film via using polyvinyl alcohol (PVA) as a sacrificial pore-forming agent, which can well multiply triple-phase boundaries and provides more oxygen reduction reaction sites. The pore-forming mechanism is clarified via molecular dynamics (MD) simulation, while the oxygen transport resistance and fuel cell performance are electrochemically measured in situ. The results shows that the as-created nanopores on/in the Nafion film could greatly diminish the local oxygen transport resistance from 0.37 s cm(-1) to 0.08 s cm(-1), corresponding to a 78% decrease, thus improving fuel cell performance. It is believed that the nanoscale controlling of Nafion ionomer morphology in CCLs is innovative and instructive in PEMFC electrode design and could shed light on numerous types of electrochemical equipment.

Automated summary

This study successfully regulated the nanoscale distribution of the Nafion film using polyvinyl alcohol (PVA) as a sacrificial pore-forming agent, which reduced the oxygen transport resistance and improved the performance of fuel cells.