Enhanced water retention in carbon nanotube sheets-sandwiched gas diffusion layer in polymer electrolyte membrane fuel cells operated under low humidity conditions

Abstract

This study introduces the polymer electrolyte membrane fuel cell (PEMFC) using sandwiched-carbon nanotube (CNT) sheets into the gas diffusion layer (GDL). The CNT sheegts are synthesized via floating catalyst chemical vapor deposition and formed into sheets using the direct spinning technique. The sandwiched-CNT sheets PEMFC indicates high electrochemical performance across a range of relative humidity conditions, remarkably in non-humidified conditions of the cathode. This notable achievement can be attributed to the distinctive physical properties of the CNT sheets. In contrast to the microporous layers, the CNT sheets possess a nanoporous structure that enhances reactant diffusion, and appropriate hydrophobicity enhances the water retention capacity in GDL. These properties are confirmed by polarization curves, electrochemical impedance spectroscopy (EIS), quantitative capillary pressure, and water removal rate test in constant current mode at 0.4 A/cm2. In the non-humidified cathode condition, the peak power density of the sandwiched-CNT sheets PEMFC is 45% higher than conventional PEMFC. Moreover, it demonstrates significantly reduced ohmic resistance in EIS. The water retention capability of the PEMFC is assessed through quantitative capillary pressure and water removal rate test. Based on these assessments, we validate that the sandwiched-CNT sheets PEMFC exhibits high performance even under non-humidified cathode conditions.