Porous zirconium oxide nanotube modified Nafion composite membrane for polymer electrolyte membrane fuel cells operated under dry conditions

Abstract

We report a high performance and durable electrolyte membrane operated in polymer electrolyte membrane fuel cells under low relative humidity (RH). This was accomplished by incorporating water retaining mesoporous zirconium oxide (ZrO<inf>1.95</inf>) nanotubes (ZrNT) in a perfluorosulfonic acid (Nafion) membrane. Porous ZrNT with average diameters of 90nm was synthesized by pyrolysing electrospun zirconium precursor embedded polymer fibers at 600°C under an air atmosphere. The superior water retention ability and the tubular morphology of the ZrNT fillers resulted in facile water diffusion through the membrane, leading to a significant improvement in membrane proton conductivity under both fully humid and dry conditions. Compared to a commercial membrane (Nafion, NRE-212) operated under 50% and 100% RH at 80°C, the Nafion-ZrNT membrane exhibited 2.7 and 1.2 times higher power density at 0.6V, respectively. Under dry conditions (18% RH at 80°C), the Nafion-ZrNT membrane exhibited 3.1 times higher maximum power density than the NRE-212 membrane. In addition, the Nafion-ZrNT membrane also exhibited durable operation for 200h under 18% RH at 80oC. The remarkably high performance of the Nafion-ZrNT composite membrane was mainly attributed to the reduction of ohmic resistance by incorporating the mesoporous hygroscopic ZrO<inf>1.95</inf> nanotubes. © 2015 Elsevier B.V.