Abstract: The stability of Pd-Fe alloy catalysts for the oxygen reduction reaction (ORR) was characterized in situ by using the rotating disk electrode and electrochemical quartz crystal microbalance (EQCM) techniques, both in acidic and alkaline solutions. The alloy catalyst was found to be unstable in the acidic solution because of the electrochemical and chemical dissolution of the catalyst. This dissolution resulted in a reduction of activity for the oxygen reduction reaction and also a reduction in the mass of the catalyst. In an alkaline solution, the mass of the Pd-Fe alloy catalyst deposited on the electrode surface and its electrochemically active surface area hardly changed. Consequently, the catalyst kept its activity for stable oxygen reduction.

Key words: Pd-Fe alloy, Electrochemical quartz crystal microbalance, Catalyst, Fuel cell, Stability