Local Characterization of PEFCs by Differential Cells: Systematic Variations of Current and Asymmetric Relative Humidity

Systematic variations of current density and asymmetric relative humidity are realized on differential Polymer Electrolyte Fuel Cells (PEFCs). The water distribution is visualized and quantified by high resolution in-plane imaging, and its effect on performance is discussed. Two cells are investigated: one using paper type gas diffusion layers (GDLs) and one with cloth type GDLs. The novel output of this work is an extensive database of local measurements obtained by the differential cell approach and an asymmetric variation of relative humidity. This should be particularly valuable for the validation of modeling studies. The negative impact of water accumulation on the performance is clearly stronger for the paper type GDLs than for the cloth type GDLs. On the contrary, the performance of the cell with cloth GDLs is low in dry conditions. The accumulation of water in the channel region of the cathode GDL has a crucial impact on performance. The anode side is observed to play an important role for water removal. The presence of a maximal liquid water saturation in the GDL for a wide range of current densities is observed and discussed. In-plane water distribution profiles are presented for the channel and rib regions for all conditions.