Decoupling oxygen and water transport dynamics in polymer electrolyte membrane fuel cells through frequency response methods based on partial pressure perturbations

Abstract

Concentration frequency response analysis (CFRA) applies partial pressure of a certain reactant and detects current or voltage response depending on the electric control applied. In this paper experimental and theoretical spectra of this novel frequency response analysis method of polymer electrolyte fuel cells are analyzed. It is shown that the dynamic contribution of oxygen transport in the channel and water sorption in Nafion could be separated from other ones if oxygen and water partial pressure are respectively used as inputs. This allows to study these phenomena separately and to avoid ambiguities encountered in EIS spectra where several dynamics are often overlapped and indistinguishable. The time required to the oxygen to diffuse in the channel and in the porous electrode was directly estimated through analysis of patterns in the CFRA spectra.