Oxygen permeation through Nafion 117 membrane and its impact on efficiency of polymer membrane ethanol fuel cell

► Oxygen permeation from cathode to anode compartment, in direct ethanol fuel cell through Nafion 117 membrane has been detected. ► Oxygen permeating from cathode reacts with ethanol on the surface of anode catalyst. ► Parasitic oxidation of ethanol leads to significant amounts of acetaldehyde and acetic acid under open circuit conditions. ► Oxygen permeating from cathode severely impact DEFC fuel efficiency.