Porous lanthanum titanium oxide nanostructure composite membrane to enhance the power output and chemical durability of low-humidifying polymer electrolyte fuel cells: impact of additive morphology

Abstract

Tuning the morphologies for improving the properties of the additive materials receives immense attention during the fabrication of proton-exchange membranes for fuel cells. This study reports the synthesis of lanthanum titanium oxide (LTO) nanostructures with different morphologies (cube, spherical, and tubular) via the pyrolysis of nanofibers containing metal precursors. A mixed matrix membrane is fabricated by incorporating LTO cubes (LTO-C), LTO spheres (LTO-S), or LTO tubes (LTO-T) into a Nafion matrix, with improved physicochemical, thermomechanical, and electrochemical properties compared to those of the unmodified Nafion and Nafion-212 membranes. We investigate the effect of LTO morphology on the performance of the Nafion membranes in low-humidity polymer electrolyte fuel cells (LH-PEFCs). The water retention and diffusion behavior of LTO-T nanostructures improve the proton conductivity and LH-PEFC performance of the Nafion composite membranes. The coexistence of La3+ and Ti4+ affords efficient radical scavenging during long-term LH-PEFC operation, which realizes higher durability for the composite membranes compared to Nafion. Accordingly, this study proposes a novel strategy to resolve the major challenges associated with the operation of LH-PEFCs with Nafion membranes: dehumidification and oxidative degradation.