Effect of a Rigid Gas Diffusion Media Applied as Distributor of Reagents in a PEMFC in Operation, Part I: Dry Gases

摘要

Several mass transport phenomena develop during the operation of a PEMFC; each one of this generates a mechanical - physics resistance to some extent, implying limitations during operation. In a conventional PEMFC, the feeding reactive gases to the reaction sites are conduced by a series of elements such as: channels in gas distributor, diffusion layer on the electrodes and the active layer. Inside of this elements reagents concentration gradients are generates before arriving to the active sites. Additionally, at high values of current density, the resistance to the mass transport of reagents is increased by the presence of water-product in the pores of electrodes, reducing significantly the performance of the PEMFC. This work focuses on reducing the resistance to mass transport by applying a rigid gas diffusion media including as gas distributor including a high number of macropores. This gas distributor is manufactured using a composite commercial material (carbon and graphite powders). The results show significant effects on the zone of diffusion in the PEMFC polarization curves, it is possible to reduce the mass transport limitations at high current density, however the ohmic losses zone on the polarization curves show an important electro-conductive limitation due to a deficient matrix.