The Effect of Ru or Ir Addition on Nano-Structured-Thin-Film Supported Pt Fuel Cell Catalysts under Rotating Disk Electrode Simulated Start-up Shut-down

Abstract

In this study, small amounts of either Ir or Ru (up to 22 μg cm−2) were added to 85 μg cm−2 Pt by either co-sputtering or over-layer sputtering onto 3M Company's NSTF catalyst support, which was grown on glassy carbon electrodes for the purpose of simulating fuel cell start-up and shut-down with rotating disk electrode techniques. The transient cathode potentials caused by fuel cell start-up, shut-down and operating conditions were simulated with a combination of potentiostatic and galvanostatic holds. Constant potential was used to simulate fuel cell run, rest and idle, and constant current was used to simulate the start-up and shut-down events. Over the course of an experiment, the catalyst would experience potential as low as 0.650 VRHE (run) and as high as 1.53–1.8 VRHE (dependent on the behavior of the composition) under the galvanostatic holds. All compositions including either Ir or Ru lasted significantly longer than for pure Pt under repeated start-up/shut-down. The stability of the over-layer Ir-Pt compositions was significantly higher than for the co-sputtered deposition. The compositions containing 9 and 22 μg cm−2 Ir over-layer on Pt showed no ORR activity decrease over the course of 1400 SU/SD simulations (2800 potential peaks >1.5 VRHE).