Effect of Interfacial Mass Transport Losses at the Ultrathin Film Catalyst Layer to Diffusion Layer of a PEMFC at Sub-zero Conditions

Abstract

In the race for a viable alternative source of power for internal combustion engines, automotive polymer electrolyte membrane fuel cell (PEMFC) continues to be one of the leading commercially viable options. This is due to their lack CO2 emission, high efficiency and adaptability. However, factors inhibiting effective commercialization of PEMFC includes low power density, reliability at sub-zero temperature and prohibitive cost of production. The cost of catalyst is being reduced by increasing the activity and reducing the loading from 0.4 mgPt/cm2 to below 0.1 mgPt/cm2. This results in nominal operational mass transport losses at the diffusion media/catalyst layer interface. It is anticipated that subzero losses will be exacerbated due to limited reactant diffusivity and proton conductivity.
This research attempts to investigate the mass transport mechanisms of dilute oxygen at the interface between the cathode catalyst layer and the diffusion media of a PEMFC at sub-zero conditions. At -20°C isothermal water fill tests will be performed to assess the water fill capacity of the cathode catalyst layer and the related O2 concentration dependent voltages and hydration dependent ionic conductivity. The interfacial losses at the interface of the ultra-thin film catalyst layers of a PEMFC will be determined by altering the diffusivity with the carrier gas. By varying the diluents (i.e. N2, He, and Ar), we wish to establish the relationship between different carrier gasses and diffusivity of O2 at the gas diffusion layer.