Reduction of Platinum Loading in Gas Diffusion Electrodes for High Temperature Proton Exchange Membrane Fuel Cell Application: Characterization and Effect on Oxygen Reduction Reaction Performance

Abstract

Lowering the Pt loading in catalyst layers of high temperature proton exchange membrane fuel cells (HT PEMFC) is of particular importance due to the currently high amounts of noble metal needed for the required performance. This work focusses on lowered Pt loadings at the cathode of a HT PEMFC outgoing from the state-of-the-art loadings of 0.85 mg cm-2. Therefore, a commercial half-cell setup is utilized for investigation of gas diffusion electrodes (GDE) in concentrated H3PO4 at 140 °C. Self-fabricated GDEs from ultrasonic spray-coating of the catalyst layers using a commercial PtNi/C catalyst are optimized with respect to the binder content and analyzed by µ computed tomography (µ-CT). Performances of GDEs with various Pt loadings are intensively tested and related to the Pt utilization and possible (mass transport) limitations. It is shown that the commercial GDE can be outperformed by self-prepared GDEs with comparable and lower Pt loadings. µ-CT is used to determine the catalyst layer thicknesses and a comparison of oxygen and air as reactant gases gives insights into occurring mass transport limitations. The implementation of spray-coated GDEs into MEAs and the performances observed in HT PEMFC measurements provide new insights into transferring GDE half-cell results to single-cell tests.