Abstract: The lifetime behavior of the proton exchange membrane fuel cell(PEMFC) fabricated with polystyenesulfonic acid(PSSA) membrane was investigated in order to present the degradation mechanism of the PSSAmembrane. The water evacuated from the anode and the cathode of the cell during the lifetime experiment was analyzed by the method of high-performance liquid chromatogram. The distribution of Sconcentration in the cross-section of the PSSAmembrane was measured by energy dispersive spectrograph. Infrared spectroscopic measurements were carried out to investigate the structure of the PSSAmembrane before and after the fuel cell experiment. The degradation mechanism of the PSSAmembrane is indicated as that: during the fuel cell operation, the reduction of O₂ gas at the cathode proceeds through a peroxide intermediate. H₂O₂ reacts with the trace metal ions in the cell to form HO^·, HO₂^· and other oxidation radicals, which can chemically attack the tertiary hydrogen at the α-carbon of the PSSAmembrane. The degradation of the PSSAmembrane mainly occurs from the cathode of the cell. The loss of the aromatic ring and the SO₃^- group simultaneously occurs from the PSSAmembrane. A PSSA-Nafion composite membrane was prepared according to the above-mentioned degradation mechanism of the PSSAmembrane. The Nafion 101 membrane of 25 μm thickness is located at the cathode. The PEMFCwith the PSSA-Nafion composite membrane could be operated steadily for more than 800 hours without significant performance deterioration.

Key words: Proton-exchange membrane fuel cells, Polystyenesulfonic acid membrane, Degradation mechanism, High-performance liquid chromatography, Energy dispersive spectrograph, Infrared spectra