Effect of convective channel-to-channel mass flow in a polymer electrolyte fuel cell

The effect of convective channel-to-channel mass flow on the local performance of a polymer electrolyte fuel cell (PEFC) air cathode is determined experimentally by using submillimeter resolved current density distribution measurements in channel and land areas. A special cell is employed, where the two parallel channels of the cathode flow field can be operated at different pressure. For isobaric operation of the channels (Δp = 0 mbar), the lateral current density distribution shows a distinct minimum in the land area between the channels as diffusive mass transport becomes limiting at a higher cell polarization. Toward higher Δp, the local cell performance in the land area improves initially as a result of an improving convective channel-to-channel mass flow. However, as the pressure difference exceeds a value of 10 mbar, no noteworthy additional benefit is observed with further increasing Δp. Under these conditions, the convective mass flow provides an abundant reactant supply in the land area and, since reactant depletion is no longer limiting, the lateral current density distribution is primarily governed by the local ohmic resistance. As a result, the current density exhibits a maximum in the land area, where the local ohmic resistance shows a minimum.

► Reactant supply in land areas of a polymer electrolyte fuel cell is a critical issue.
► The convective channel-to-channel mass transport in flow fields is investigated.
► Performance improves up to 70% with convective flow in the land areas.
► Key parameters for flow field modeling can be determined with the novel method.
► Optimization of flow field plates is important for efficient catalyst utilization.