A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium catalysts dissolution, and the membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were found to dissolve in 1 M sulfuric acid solution and the dissolution increased exponentially with the upper potential limit (UPL) between 0.6 and 1.6 vs. RHE. 2-20% of the Pt (depending on the catalyst type) was found to be dissolved during the experiments. Under the same conditions, 30-100% of the Ru (depending on the catalyst type) was found to be dissolved. The faster dissolution of ruthenium compared to platinum in the alloy type catalysts was also confirmed by X-ray diffraction measurements. The dissolution of the carbon supported catalyst was found one order of magnitude higher than the unsupported catalyst. Other factors like medium acidity, chloride content and oxygen partial pressure all turned out to influence the noble metal dissolution. The degradation of the polyfluorinated sulfonic acid membrane electrolyte was also found to be an important source of increased acidity in the Three-Phase-Boundary (TPB), and consequently the dissolution of the noble metal catalysts. (C) 2010 Elsevier B.V. All rights reserved.
Solid State Ionics, 2011, Vol 192, Issue 1, p. 602-606