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 shut-down. 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 shut-down. 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.

Bifunctional Pt-IrO2 Catalysts for the Oxygen Evolution and Oxygen Reduction Reactions: Alloy Nanoparticles vs. Nanocomposite Catalysts

“…A similar degradation protocol was employed in previous work. 40 The degradation test was conducted in the O2-saturated HClO4 electrolyte maintaining a rotation of 1600 rpm. The current was stepped between 0 and -5 mA cmgeo -2 , which is roughly the diffusion limited current during ORR in a RDE measurement at 1600 rpm, with a rest time of 1 s. This procedure was repeated for 5 times followed by a current step to 1 mA cmgeo -2 for one second.…”

Elucidating Pt-Based Nanocomposite Catalysts for the Oxygen Reduction Reaction in Rotating Disk Electrode and Gas Diffusion Electrode Measurements

“…The trend in stability observed in the RDE measurements is less straightforward and depends on the applied ADT protocol. Based on literature and our previous work 27,51 , one might expect an improvement in stability when adding Ir NPs to the Pt/C benchmark catalyst. Such improvement is indeed observed, when choosing an ADT protocol that applies highly oxidizing conditions, see Figure 2.…”

Elucidating Pt-Based Nanocomposite Catalysts for the Oxygen Reduction Reaction in Rotating Disk Electrode and Gas Diffusion Electrode Measurements

“…The trend in stability observed in the RDE measurements is less straightforward and depends on the applied ADT protocol. Based on literature and our previous work [27,47], one might expect an improvement in stability when adding Ir NPs to the Pt/C benchmark catalyst. Such improvement is indeed observed, when choosing an ADT protocol that applies highly oxidizing conditions, see Figure 2.…”