Enhanced Oxygen Reduction Activity on Pt/C for Nafion-free, Thin, Uniform Films in Rotating Disk Electrode Studies

Commercially available nanoparticle platinum on high surface area carbon black (Pt/HSC) electrocatalysts were characterized in rotating disk electrode (RDE) setups using varying ink formulations and film drying techniques in an attempt to obtain thin, uniform films and reproducible activity. Electrodes prepared from Nafion-free inks that were dried under an isopropyl alcohol (IPA) atmosphere produced uniform, thin films at low electrocatalyst loadings of ∼4.5 μg/cm² Pt. These Nafion-free/IPAdried electrodes were found to exhibit oxygen reduction reaction (ORR) activities higher than conventional Nafion-based/Air-dried electrodes by a factor of ∼2.8. The magnitude of mass and specific activities were determined to be i _m∼771 ±56 mA/mgPt and i_s∼812 ±59 mA/cm2 Pt respectively and appear to be the highest values reported for RDE measurements on Pt/HSC in 0.1M HClO₄ at 20 mV/s and 25oC. Electrochemical diagnostics including ORR I-V profiles, cyclic voltammograms and electrochemical impedance spectroscopy (EIS) studies were conducted to investigate the thin film Pt/HSC electrodes and correlate results to film morphology and electrochemical activity.