Catalyst failure analysis of a direct methanol fuel cell membrane electrode assembly

Lifetime testing of a single cell direct methanol fuel cell (DMFC) was carried out at 100 mAcm(-2), ambient pressure and 60 degrees C. X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) were used to characterize the anode and cathode catalysts before and after lifetime testing. The XRD results showed that the particle sizes and lattice parameters of anode catalyst increased from 2.8 to 3.2 nm and from 3.8761 to 3.8871 angstrom; the cathode catalyst increased from 7.3 to 8.9 nm and from 3.9188 to 3.9204 angstrom before and after the lifetime test, respectively. The XPS results indicated that during the lifetime period, the extent of oxidation of the anode Pt and Ru components increased, and Ru appears in the XPS of the cathode. Polarization curves, power density curves, and in situ cyclic voltammetry were employed to test the performance of fuel cell and electrochemically active specific surface areas (S-EAS) of the anode and cathode catalysts before and after the lifetime test. The overall findings are that the cathode suffers the greatest degradation over the test period and that subtle changes at the anode can have substantial adverse effects on the cathode. (C) 2007 Elsevier B.V. All rights reserved.