Enhancing liquid water transport by laser perforation of a GDL in a PEM fuel cell

The presence of liquid water in a polymer electrolyte membrane fuel cell hinders gas diffusion to the active sites, which results in large concentration overpotentials and instability of the fuel cell performance. In this paper, a new customized gas diffusion layer (GDL) is presented that enhances liquid water transport from the electrode to the gas channels and therefore lowers mass transport losses of oxygen through the porous media. The GDL is systematically modified by laser-perforation with respect to the flow field design. The holes are characterized by SEM images. The performance of the laser-treated GDL was investigated in a small test fuel cell with a reference electrode by voltammetry and chronoamperometry measurements and compared to corresponding data with a non-modified GDL. Voltammetry experiments with different humidification levels of the inlet gases were conducted. In all cases, the cathode overpotential with the perforated GDL clearly shows reduced saturation which can be seen in a lower overpotential in the region limited by mass transport resulting in a higher limiting current density. The investigated current response of the chronoamperometry measurements clearly shows a better dynamic and overall performance of the test cell with the perforated GDL. (C) 2007 Elsevier B.V. All rights reserved.