Fabrication and Performance of Membrane Electrode Assembly Using a Hydrophilic Pt/[TaOPO4/VC] Electrocatalyst

Thursday, October 15, 2015: 17:00
211-A (Phoenix Convention Center)
Y. Garsany (EXCET Inc.), M. B. Sassin, B. D. Gould (US Naval Research Laboratory), and K. Swider-Lyons (US Naval Research Laboratory)
Oxide- and phosphate-supported catalysts promote the oxygen reduction reaction (ORR) in acid and alkaline electrolyte.  We previously reported a high mass- and area-specific ORR activity for an electrocatalyst with 18 wt% loading of 2.4 nm Pt nanoparticles supported on a 3 wt% tantalum oxyphosphate-treated VC (Pt/[TaOPO4/VC]). The electrocatalyst was heat treated at 660C in a reducing atmosphere and characterized using thin-film rotating disc electrode (RDE) in an acidic electrolyte and alkaline electrolyte.  However preliminary experiments show that the performance of the Pt-TaOPO4 catalysts as measured by RDE is not representative of its performance in a proton exchange membrane fuel cell (PEMFC), possibly because of the hydrophilicity of the oxyphosphate.  We reconcile the difference between RDE and PEMFC performance by developing a range of catalyst layers (CLs) fabricated by decal method and by direct deposition of the Pt/[TaOPO4/VC] electrocatalyst onto the Nafion® membranes using an in-house built ultrasonic spray coating system.  Nitrogen adsorption, mercury porosimetry, and scanning electron microscopy (SEM) are used to investigate the effects of ionomer/carbon ratio (I/C) on the surface area, pore structure and morphology of the CLs; cyclic voltammetry and polarization curves are used to determine the electrochemically active area (ECSA) and PEMFC performance.