Blocking the sulfonate group in Nafion to unlock platinum’s activity in membrane electrode assemblies

The specific adsorption of ionomer sulfonate groups on Pt-based catalysts in membrane electrode assemblies (MEAs) has severely restricted Pt catalytic activity, Pt utilization, proton conductivity and mass transport. Here we report a blocking strategy using cyclohexanol to mitigate the detrimental impacts of the Nafion ionomer. Cyclohexanol with a chair or boat conformation blocked the adsorption path of the ionomer onto the Pt surface via coordination with the ionomer, which released the Pt activity sites and dramatically improved the mass transport path. This MEA with cyclohexanol exhibits striking performance improvement in the kinetic and mass transport regions, along with strong stability. The proposed strategy provides a direction to tune the Pt/ionomer interface and improve the catalytic activity of Pt in MEA. The full potential of the well-known platinum oxygen reduction catalyst has not been realized in membrane electrode assembly for fuel cells due to the detrimental impacts of the required ionomer layer. Here the authors show how cyclohexanol can block the interaction between Pt and sulfonate groups of Nafion with benefits for reaction kinetics and mass transport.