Improvement in high temperature proton exchange membrane fuel cells cathode performance with ammonium carbonate

Proton exchange membrane (PEM) fuel cells with optimized cathode structures can provide high performance at higher temperature (120 degrees C). A "pore-forming" material, ammonium carbonate, applied in the unsupported Pt cathode catalyst layer of a high temperature membrane electrode assembly enhanced the catalyst activity and minimized the mass-transport limitations. The ammonium carbonate amount and Nafion (R) loading in the cathode were optimized for performance at two conditions: 80 degrees C cell temperature with 100% anode/75% cathode R.H. and 120 degrees C cell temperature with 35% anode/35% cathode R.H., both under ambient pressure. A cell with 20 wt.% ammonium carbonate and 20 wt.% Nation (R) operating at 80 degrees C and 120 degrees C presented the maximum cell performance. Hydrogen/air cell voltages at a current density of 400 mA cm(-2) using the Ionomem/UConn membrane as the electrolyte with a cathode platinum loading of 0.5 mg cm(-2) were 0.70 V and 0.57 V at the two conditions, respectively. This was a 19% cell voltage increase over a cathode without the "pore-forming" ammonium carbonate at the 120 degrees C operating condition. (c) 2004 Elsevier B.V All rights reserved.