Remarkable Extension of Membrane Lifetime with Improved Output Performance in Fuel Cells by Use of ZrO 2 -Containing Pt/C Anode Catalyst Layers

The addition of ZrO 2 nanoparticles (NPs) to commercial Pt/C anode catalyst layer was found to provide a remarkably prolonged lifetime (max. 25 times) of a Nafion polymer electrolyte membrane (PEM) in an accelerated stress test of single cell at 90 °C and 40% relative humidity (RH), accompanied with improved output performances. It was clarified in the single cell that the use of ZrO 2 -NPs increased the water content of PEM (reduced ohmic resistance), resulting in effective utilization of Pt cathode catalyst, which could contributed to the increased output performances together with suppression of membrane degradation. The H 2 O 2 formation rate on Pt/C, which can decompose into ·OH radicals to attack PEMs, was observed to decrease by adding ZrO 2 -NPs at a practical H 2 oxidation potential in 0.1 M HClO 4 at 90 °C in a half cell. Density functional theory calculations suggested that the adsorption energy of H atom can decrease on Pt NP contacting with ZrO 2 , which played an important role in suppressing H 2 O 2 formation. In a single cell test at 40% RH and 90 °C, the limiting current density for the oxygen reduction on Pt/C in dilute O 2 decreased with increasing amount of ZrO 2 -NPs, which could slow down the O 2 -diffusion rate.