Electrochemical stability of carbon nanofibers in proton exchange membrane fuel cells

This fundamental study deals with the electrochemicalstability of several non-conventional carbon based catalyst supports, intended for low temperature protonexchangemembranefuelcell (PEMFC) cathodes. Electrochemical surface oxidation of raw and functionalized carbonnanofibers, and carbon black for comparison, was studied following a potential step treatment at 25.0 °C in acid electrolyte, which mimics the operating conditions of low temperature PEMFCs. Surface oxidation was characterized using cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cyclic voltammograms clearly showed the presence of the hydroquinone/quinone couple. Furthermore, identification of carbonyl, ether, hydroxyl and carboxyl surface functional groups were made by deconvolution of the XPS spectra. The relative increase in surface oxides on carbonnanofibers during the electrochemical oxidation treatment is significantly smaller than that on carbon black. This suggests that carbonnanofibers are more resistant to the electrochemical corrosion than carbon black under the experimental conditions used in this work. This behaviour could be attributed to the differences found in the microstructure of both kinds of carbons. According to these results, carbonnanofibers possess a high potential as catalyst support to increase the durability of catalysts used in low temperature PEMFC applications.