Chronoamperometric analysis of the oxygen reduction reaction (ORR) at Pt microelectrode | perfluorosulfonic acid (PFSA) ionomer interfaces in a solid state electrochemical cell reveals an increase in both the oxygen diffusion coefficient (Db) and oxygen permeability (Dbcb) upon consecutive potential step measurements. From a vapor-equilibrated, electrochemically unperturbed state under conditions of 70% RH and 50°C, Db and Dbcb increased by factors of 2 and 1.5, respectively. Db and Dbcb return to their initial values after resting the electrode at the open circuit potential. The electrochemical generation of water is believed responsible for the time-dependent mass transport parameters of ORR.
ECS Electrochemistry Letters4, no. 1 (1 November 2014): F9–F12.