Oxygen reduction and transport characteristics at a platinum and alternative proton conducting membrane interface

Abstract

Kinetic and mass-transport properties were investigated for the oxygen reduction reaction for Nafion® 117 and sulfonated poly(arylene ether sulfone) membranes, both pre- and post-sulfonated analogs (SPES-40 & SPES-PS) under 100% relative humidity and as a function of pressure (1–4 atm total pressure, 323 K) and temperature (303–353 K, 3 atm) using a solid-state electrochemical cell. Kinetic parameters were obtained using slow-sweep voltammetry while mass-transport parameters, the diffusion coefficient ( D) and solubility ( C), were obtained using chronoamperometry at a Pt (microelectrode)|proton exchange membrane (PEM) interface. The oxygen reduction kinetics were found to be similar for all the membranes at the Pt microelectrode interface. The temperature dependence of O 2 permeation parameters showed identical trends for the membranes studied while the pressure dependence of O 2 permeation parameters displayed some differences. Despite higher ion exchange capacities and hence higher water uptake, the two SPES membranes exhibited relatively lower values of D as compared to Nafion® 117. The results are discussed in the context of their different microstructures.