A modified subcell approach was used to measure the current density distribution of proton exchange membrane fuel cell (PEMFC) with straight channels flow field. For PEMFC with parallel channels flow field

subcells in inlet channels presented higher performance than those in middle channels

but showed lower performance than those in outlet channels. The experimental results with parallel channels flow field demonstrated that the current density distribution over the whole electrode was heterogeneous and was consistent with the velocity distribution from the mathematic model. Gas flow rate was one of prime factors to influence the current distribution of PEMFC cathode. With the decrease of reactant flow rate

the flooding process began at the flow field outlet region of a cell

and then propagated to the inlet area.