Improvement of catalyst utilisation in PEM fuel cells through inhomogeneous distribution of Pt under channels and ribs

Abstract

The non-uniform distribution of platinum across the channel and rib area within the cathode catalyst layers of proton exchange membrane fuel cells was experimentally and numerically studied. A two-dimensional, two-phase flow, isothermal model was developed to investigate the influence of various parameters on the current density with respect to electrode surface area and platinum loading. Approximately 70% cell performance was retained when no platinum was placed under the rib. Owing to the slow oxygen supply to the rib area, increasing the platinum loading significantly reduced the effective oxygen concentration under the rib, leading to low platinum utilisation in this region. The large channel/rib width ratio and highly porous gas diffusion layer improved the cell performance when the conductivity was sufficiently high. The optimal platinum loading under the rib matched the oxygen consumption rate under the rib and the rate of oxygen supply to the rib area from the channel.