Rapid rotating-disk-electrode evaluation of catalyst performance and durability during transient conditions: The Pt–Hf binary system

A comprehensive set of rotating disk electrode (RDE) tests has been developed to test the suitability of fuel cell catalyst candidates for use as either anode or cathode catalysts for transient conditions. The activity for Hydrogen Oxidation reaction (HOR), Oxygen Reduction reaction (ORR) and Oxygen Evolution reaction (OER) is tested together in one protocol. A total of 5 Pine Instruments RRDE test stations have been set up with automatic gas flow switching and computer software to control all aspects of the data collection process. The user simply sets up the electrochemical cell with a gas bubbler, reference electrode, counter electrode and sample and then selects a series of tests to be run. The software then switches gas flow, rotation rates and potentiostat set up files automatically. This infrastructure allows the rapid characterization of catalyst candidate materials. The series of tests is described, along with the purpose of each test in the protocol. As an example, the data collected from a Pt1−xHfx composition spread is presented. The optimal composition is found to be approximately 30 at.% Hf, when the ORR performance begins to decrease at a faster rate than the HOR performance and the OER current at 1300 mV is also a maximum. However, it was determined that from an applied point of view the drop in ORR performance was insufficient to adequately protect the cathode from the effects of the transient potentials during start-up of the fuel cell.