Contaminants were selected from the Environmental Protection Agency lists. Six qualitative down selection criteria were used to reduce the list to the 21 1 st tier contaminants. The effect of 1 st tier contaminants, mostly organic with the exception of ozone, on PEMFC performance is reported. The behavior of these contaminants was classified into 5 different cases; no effect, recoverable effect, partly recoverable effect, irrecoverable effect and supra-recoverable effect. The steady state contamination and irrecoverable performance losses respectively varied from 0 to 90% and −2 to 80%. Contamination and recovery time scales significantly varied within a ∼0.01 to ∼28 h range. Acetaldehyde and propene were characterized by the new supra-recoverable effect. For trichlorofluoromethane, iso-propanol and propene, a decrease of the relative humidity led to a significant change in cell performance (steady states, time scales). This effect was ascribed to several causes including the scavenging effect of liquid water by contaminant dissolution and a non zero water reaction order. Two quantitative selection criteria based on observed fuel cell performance were used to reduce the 1 st tier list to 7 2 nd tier contaminants for more resource intensive tests. These 2 nd tier contaminants are acetonitrile, acetylene, bromomethane, iso-propanol, methyl methacrylate, naphthalene and propene.

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A multitude of contaminants are present in atmospheric air. A large proportion of these contaminants have unknown effects on fuel cell performance. An assessment of the overall performance impact of all suspected contaminants is a costly and time consuming task. Thus, a method is required to select the most relevant contaminants. A two tier down selection approach is presented. Six qualitative criteria were used to create a shorter list of 19 contaminants (first tier). Two quantitative criteria were developed based on the cell performance response to further down select contaminants for detailed studies (second tier). First tier contaminants were injected into fuel cells. Performance data were used to provide a preliminary evaluation of the second tier down selection criteria.

The impact of fuel impurities toluene (C7H8) and carbon monoxide (CO) on the performance of polymer electrolyte membrane fuel cells (PEMFCs) was investigated. Single and mixed impurities were injected into the fuel cell via the anode feed stream. Experiments were accompanied by gas chromatography analysis to determine the conversion and reaction processes occurring during contaminant exposure. Impurity injections of 2 and 20 ppm C7H8 caused an insignificant overpotential change of 2 and 8 mV respectively. An almost complete conversion of C7H8 to methylcyclohexane (C7H14) was observed. Impurity injections of 2 ppm CO caused a significant overpotential change of 247 mV. At steady state conditions more than 60% of the injected CO was converted to CO2 in the fuel cell. When the impurities were injected into the anode feed stream as a mixture the overpotential change was 100 mV greater than the sum of the overpotential changes the single impurities caused .Hydrogenation of C7H8 to C7H14 was observed but in contrast to the single C7H8 impurity experiment it stopped when a certain CO coverage was reached. The strong adsorption of CO caused a competition between the hydrogen reduction reaction and the hydrogenation of C7H8 for the available reaction sites.

The effects of the airborne contaminants naphthalene, acetonitrile, and propene on the performance of a single PEMFC were investigated at different operating conditions. The results indicated that higher contaminant concentrations resulted in higher performance losses and faster degradations, while the rate of performance recovery was more rapid. Lower temperatures caused increased performance losses, more rapid degradations, slower recoveries, and irrecoverable losses. Higher contaminant concentrations and lower temperatures caused voltage oscillations when the PEMFC was contaminated with naphthalene. The exposure of the PEMFC to propene at higher temperatures resulted in performance recovery to a level that was temporarily greater than its performance prior to propene exposure. The PEMFC performance loss at different current densities was dependent on specific contaminants. At higher current densities, naphthalene and propene caused greater performance losses as well as faster degradation and recovery. Acetonitrile caused similar performance losses at all current densities. The performance degradation caused by naphthalene and acetonitrile may be dependent on the cathode potential. EIS analysis indicated that contaminant exposure affected catalytic and mass transport processes for all the impurities tested and that acetonitrile increased the membrane resistance.

This work studied the effects that exposure to the hydrogen fuel impurities: carbon monoxide (CO), toluene and methylcyclohexane (MeCH) had on the performance and durability of GORE™ PRIMEA® MESGA (A510.1/M710.18/C510.4) 1 membrane electrode assemblies (MEAs) used in hydrogen proton exchange membrane fuel cells (PEMFCs). MEAs used in this work had anode platinum catalyst loadings of 0.1 mg Pt cm -2 and were subjected to both single impurities and impurity mixtures. Gas chromatography was used to study the magnitude of conversion for CO to carbon dioxide (CO 2 ) and toluene to MeCH. The effects of operating temperature with CO as an impurity in the fuel stream were also investigated. For CO as a single impurity, 0.2 ppm concentration exposures had a measurable effect on performance that increased significantly at sub-ambient operating temperature. The conversion of carbon monoxide to carbon dioxide at steady state was observed to decrease with decreased operating temperature. For toluene and MeCH as single impurities, cell performance was not affected beyond the accuracy of the calculations to determine the impurity performance impact. Toluene to MeCH conversion was 100%. For an impurity mixture of 0.2 ppm CO and 2 ppm toluene or 0.2 ppm CO and 2 ppm MeCH the effect on performance was of similar magnitude to that of 0.2 ppm CO as a single impurity. The conversion of toluene to MeCH decreased to 96% when present with CO in an impurity mixture. In all cases, performance loss related to the impurities was reversible. The presence of fuel impurities appeared to increase the loss of anode electrochemical area.