Analysis of H2/Air Polarization Curves: The Influence of Low Pt Loading and Fabrication Process

Abstract

Significant effort has been devoted to reduce the cathode platinum loading for proton exchange membrane fuel cells (PEMFCs). To achieve this, it is imperative to have a comprehensive understanding of the polarization behavior for the low-Pt-loading electrodes, and to reduce the polarization loss due to oxygen transport limitation. Herein, a systematic breakdown of six types of polarization sources is presented to elaborate the effect of cathode Pt loading and the catalyst layer fabrication process. Four modifications are applied to accommodate low cathode Pt loading. GORE PRIMEA catalyst-coated membranes (CCMs) were used as a baseline and tested with 0.4 and 0.1 mg cm−2 cathode Pt loading. A novel electrode fabrication method, reactive spray deposition technology (RSDT), was employed to fabricate 0.1 mg cm−2 Pt loading cathode using Ketjen black carbon as catalyst supports. Non-electrode concentration overpotential is determined by the cathode Pt loading and the type of diffusion medium, while cathode electrode concentration overpotential is determined by the ionomer thin film and ionomer/Pt interface which are dependent on the fabrication process. It is shown that the RSDT process can improve fuel cell performance at 0.1 mg cm−2 cathode Pt loading by reducing the cathode electrode concentration overpotential.