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PEMFC degradation effects under critical operating conditions like low fuel stoichiometry or cell reversal can be detected at both electrodes. The cell was characterized with electrochemical impedance spectroscopy to show changes of the conductivities and cyclic voltammetry to measure the reduction of the active platinum surface areas. The analyzing of the electrode corrosion at fuel starvation with online gas analysis shows small amounts of carbon dioxide at both gas outlets and carbon monoxide at the anode side. To analyze the carbon corrosion effects at the cathode side, potential effects were investigated and current distribution measurements were realized.

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Cathodes for fuel cells with platinum as catalyst supported on tubular carbon nanofibers (CNFs) were investigated for the oxygen reduction reaction. CNFs should find a promising application field in fuel cell technology, due to their electrical and structural properties. CNFs were plated with platinum particles by an electroless plating method. CNF-based electrodes were produced by a sedimentation method. Polarization curves were measured in half cell tests, and physical characterization was carried out by scanning electron microscopy. It was shown that the fibers are capable of providing the required porosity with low binder content and an excellent electrical conductivity, as well as a good performance with low catalyst loading. The fibers allowed a reduction of the binder content in the electrode to prevent covering of catalyst with binder. With an optimization of the thickness of the electrode, the catalyst is lowered by 40 % without a significant loss of performance.