Air-breathing fuel cell with a columnar cathodic plate for the passive removal of water

Abstract

Due to their high power density and reduced system requirements, passive proton-exchange membrane fuel cells (PEMFCs) are most appropriate for small and portable applications. These cells use static hydrogen and ambient air which poses important mass transport limitations of liquid water in the porous electrodes. In this work, a new cathodic plate is studied to optimize water transport and its removal from a passive PEMFC. The plate has an array of columns to favour the mobility and elimination of water drops over the cathode surface by the combining effects of gravity, capillarity, and evaporation. The performance of the new columnar plate is assessed by comparing with a perforated planar plate, and with a conventional PEMFC with flow-field plates. It is found that the columnar plate doubles the mass transport limiting current and peak power density of the planar plate. The analysis of the polarization curves and electrochemical impedance spectroscopy show that the columnar plate decreases water saturation in the cathodic gas diffusion layer (GDL) which improves the transport of gases. It is also found that the columnar plate decreases the dependence of cell performance on orientation which is advantageous for the operability in different applications. The peak power density of the passive air-breathing cell with columnar plate is 15% below that of a conventional cell with flow field plates, which allows to anticipate higher specific power density of the whole system in portable applications.