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 (ZrO1.95) 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 ZrO1.95 nanotubes.