The role of ambient conditions on the performance of a planar, air-breathing hydrogen PEM fuel cell

This paper presents experimental data on the effects of varying ambient temperature (10-40 degrees C) and relative humidity (20-80%) on the operation of a free-breathing fuel cell operated on dry-hydrogen in dead ended mode. We visualize the natural convection plume around the cathode using shadowgraphy, measure the gas diffusion layer (GDL) surface temperature and accumulation of water at the cathode, as well as obtain polarization curves and impedance spectra. The average free-convection air speed was 9.1, cm s(-1) and 11.2 cm s(-1) in horizontal and vertical cell orientations, respectively. We identified three regions of operation characterized by increasing current density: partial membrane hydration, full membrane hydration with GDL flooding, and membrane dry-out. The membrane transitions from the fully hydrated state to a dry out regime at a GDL temperature of approximately 60 degrees C, irrespective of the ambient temperature and humidity conditions. The cell exhibits strong hysteresis and the dry membrane regime cannot be captured by a sweeping polarization scan without complete removal of accumulated water after each measurement point. Maximum power density of 356 mW cm(-2) was measured at an ambient temperature of 20 degrees C and relative humidity of 40%. (c) 2006 Elsevier B.V. All rights reserved.