Iridium-Titanium Oxide as Support for Pt Catalyst in PEFC Cathodes

Platinum supported on iridium-titanium oxide was investigated as cathode catalyst under polymer electrolyte fuel cell relevant conditions. Degradation of the cathode catalyst layer during automotive fuel cell operation was simulated by performing 1000 cyclic voltammetry scans between 0.5 V vs. RHE and 1.5 V vs. RHE in 0.1 M perchloric acid at room temperature. The electrochemically active platinum surface area was determined by CO stripping voltammetry with a novel method of baseline subtraction, and was found to reduce by 42% under these conditions. The activity of the metal oxide supported platinum catalyst towards oxygen reduction reaction was determined before and after the degradation test by rotating disk electrode measurements. The absolute kinetic current suffered a loss of 36% during the start / stop cycling. In contrast, the specific kinetic current was found to increase, which could be explained with a particle size effect due to platinum nanoparticle growth during potential cycling.