Corrosion Induced Degradation of Pt/C Model Electrodes Measured with Electrochemical Quartz Crystal Microbalance

Degradation of fuel cell model electrodes during accelerated aging was studied using electrochemical quartz crystal microbalance with dissipation monitoring. The model electrodes, consisting of Pt particles (5 nm) on planar carbon and Pt-only and carbon-only films, were prepared by thermal evaporation onto uncoated quartz crystal sensors. The characterization of electrode composition and morphology was performed by X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and atomic force microscopy. The experiments were conducted in a flow cell with 0.5 M H2SO4 at room temperature and up to 70 degrees C by repeated cycling between 0.02 and 1.4 V-RHE (where RHE is reversible hydrogen electrode) at 50 mV s(-1). During cyclic corrosion, the Pt-only sample loses mass equivalent to 0.6% of a monolayer per cycle in a process that is not temperature-dependent. The experiments with the Pt particle layer on a carbon electrode show a mass loss that is almost 2 times larger than the Pt-only sample and exhibits an Arrhenius type of temperature dependence. The results suggest that the presence of Pt catalyzes carbon corrosion with an apparent activation energy of 0.33 eV. In all measurements, the carbon-only sample loses much less mass than the other samples.