Microscopic Investigation of Platinum Deposition in PEMFC Cross-Sections Using AFM and SEM

Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate platinum (Pt) deposition in the membrane of degraded proton exchange membrane fuel cells (PEMFCs). This study focuses on Pt distribution and microscopic aspects of accelerated membrane degradation. To facilitate post-mortem analysis, a 4-cell stack was specially designed with cells composed of two membranes. Considerable Pt deposition was observed in both membranes and at their interface. Significant crystallite growth in the form of a Pt band and membrane thinning was present in the membrane at the cathode side, which supports the hypothesis that Pt deposition accelerates polymer decomposition. Furthermore, a large continuous area of Pt crystals across the whole cathode membrane was detected. In addition, conductive AFM measurements revealed electronic connections across the membrane. These results indicate the formation of electronic short-circuits in the cell due to the accumulation of Pt particles, which has not been previously reported. Moreover, AFM proved to be more sensitive to detect Pt deposits and its effects than SEM. (C) 2013 The Electrochemical Society. All rights reserved.