Screening Bifunctional Pt Based NSTF Catalysts for Durability with the Rotating Disk Electrode: The Effect of Ir and Ru

Abstract

Various amounts of Ir (<20 μg cm −2) and Ru (up to 12 μg cm −2) on a consistent base Pt loading of 85 μg cm −2 , were sputter deposited on a nanostructured thin film catalyst support to mimic a hydrogen fuel cell's cathode catalyst. The nanostructured support was grown on glassy carbon disks designed for a rotating disk electrode, which was used to simulate what happens to a fuel cell cathode during repeated start-up, operation, and shutdown. The testing protocol subjected the catalyst to a minimum potential of 0.65 V RHE and a maximum between 1.53 and 1.8 V RHE. The upper potential was achieved with a galvanostatic hold which is an alternative way to simulate potential transients on the cathode caused by start-up and shutdown. Increasing Ir loading improved the durability of both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. When combined with Ir, Ru provided no benefit to OER durability except at an Ir loading of 10 μg cm −2. Ru addition (no Ir present) improved the ORR durability compared to pure Pt. ORR durability was not influenced by Ru addition to Ir-containing samples. In general, ORR durability showed no dependence on Ru loading for all the Ru containing samples and ORR activity was decreased by OER catalyst addition, though more so for Ir than Ru.