In Situ Measurement of Oxygen Permeability in Polymer Electrolyte Membranes

摘要

Oxygen permeability in polymers (Nafion~? and Sulfonated polyether ether ketone or SPEEK) was measured in-situ using a cylindrical Pt microelectrode by chronoamperometry at conditions mimicking actual fuel cell operation. The micro electrode (working electrode) reduces instantaneously any oxygen permeating through the polymer by changing to a potential at which oxygen transport is limited by diffusion. From the current profile corresponding to the potential hold, diffusivity and concentration of oxygen in the polymer was estimated. Durability of fuel cell membrane has been a long standing issue in fuel cell commercialization. Membrane degradation occurs due to highly reactive oxygen species formed in a fuel cell environment. Two modes of membrane decay widely reported in the literature are formation of (ⅰ) hydrogen peroxide (H_2O_2) and its subsequent decomposition to yield radicals and (ⅱ) oxygen reduction reaction intermediates. Viability of the use of Pt microelectrode in detection of H_2O_2 in both liquid and solid electrolytes was also studied. In both cases H_2O_2 was forcibly added to the system.