Fuel cell contaminants anions

PEMFC contamination can also adversely impact membrane performance and life. The common impurities in fuel cell include anions, cations, CO, HjS, NH3, SO , NO, and volatile organic compounds. - Cationic impurities, including alkaline metals and ammonium, can infiltrate the membrane, considerably reducing performance. Metal ions, such as Fe + and Cu, can catalyze the radical formation reactions, strongly accelerating the chemical degradation of membranes in a PEMFC. Stainless steel is unsuitable as a material for end plates in PEMFCs. ... 

Anions, such as halide ions (F, CL), SO, and NO3, also can be introduced into a fuel cell system during operation. Halide ions are the most important contaminants among all anions, and can enter fuel cells in different ways. 

The proton exchange membrane can be a source of fluoride ions as well [143]. Hydroxyl radicals, formed via crossover gases or reactions of hydrogen peroxide with Fenton-active contaminants (e.g., Fe +), could attack the backbone of Nafion, causing the release of fluoride anions these anions in turn promote corrosion of the fuel cell plates and catalyst, and release transition metals into the fuel cell [143]. Transition metal ions, such as Fe, then catalyze the formation of radicals within the Nafion membrane, resulting in a further release of fluoride anions. On the other hand, transition metal ions also can cause decreased membrane and ionomer conductivity in catalyst layers, as discussed in section 2.4 of this chapter. 

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