Efficient water management of composite membranes operated in polymer electrolyte membrane fuel cells under low relative humidity

Abstract

High performance and durable electrolyte membrane operated in polymer electrolyte membrane fuel cells (PEMFCs) under low relative humidity (RH) has been achieved by incorporating various diameter sizes of mesoporous hygroscopic TiO2 nanotubes (TNT) in a perfluorosulfonic acid (Nafion®) membrane. Porous TNTs with different tube diameters are synthesized by thermal annealing the electrospun polymer containing titanium precursor mat at 600°C under an air atmosphere. The diameter of the TNT is significantly controlled by changing the concentration of the precursor solution. Compared to a commercial membrane (Nafion, NRE-212), the Nafion-TNT-10 composite membrane operated under 100% RH at 80°C generates about 1.3 times higher current density at 0.6V, and 3.4 times higher maximum power density operated under dry conditions (18% RH at 80°C). In addition, the Nafion-TNT-10 composite membrane also exhibits stable and durable operation under dry conditions. The remarkably high performance of the Nafion-TNT-10 composite membrane is mainly attributed to the significant reduction of the ohmic resistance as well as the improvement of cathode catalyst utilization by incorporating TNTs, which greatly enhances the water retention and the water management capability through the membrane. Furthermore, Nafion–TNT membranes exhibit superior mechanical property.