An in situ method for determination of current distribution in PEM fuel cells applied to a direct methanol fuel cell

This paper describes and demonstrates a new method for determination of current density distribution in an operating polymer electrolyte membrane (PEM) fuel cell. The technique is a modification of the current mapping technique that relies on an array of shunt resistors embedded within a current collecting plate. Standard, nonaltered membrane electrode assemblies are utilized with gas diffusion layers in direct contact with an electrically segmented current collector/flow field. Multiple current measurements are taken simultaneously, allowing transient distribution detection with a multichannel potentiostat. Both steady state and transient data are presented for an operating liquid fed direct methanol fuel cell. Cathode flooding is predicted, and shown to occur at relatively high cathode flow rates. This technique can contribute to knowledge and understanding of key phenomena including water management and species distribution in PEM fuel cells. (C) 2002 The Electrochemical Society.