The Impact of sub ppm Carbon Monoxide and ppm Level CO/Toluene and Methylcyclohexane/CO Mixtures on PEMFC Performance and Durability

Abstract

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.

Effect of Toluene on PEMFC Performance

“…The effect of impurity mixtures cannot be expected to be the sum of the effects of two single impurities. Previous studies have shown that the effect of impurity mixtures can be higher or of similar magnitude, and/or have different overvoltage‐time behavior than the effects of the same impurity concentrations solely , , . In these measurements, the CO with the toluene mixture had a smaller overall effect than the calculated sum of the effects.…”

Carbon monoxide poisoning and mitigation strategies for polymer electrolyte membrane fuel cells – A review

“…77,78 The effects of a mixture of 2 ppm C7H8 with 0.2 ppm CO had the same effects than the CO alone. 78 However, when 20 ppm C7H8 was mixed with 2 ppm CO, the resultant overpotential increased to higher values than the sum of the individual contributions (Figure 9).…”

“…and CO, and mixtures thereof, have been studied. [77][78][79] Concentrations of 2 ppm or 20 ppm C7H8 did not have a significant effect on the performance of the cell due to its hydrogenation to methylcyclohexane (C7H14). 77,78 The effects of a mixture of 2 ppm C7H8 with 0.2 ppm CO had the same effects than the CO alone.…”

“…[77][78][79] Concentrations of 2 ppm or 20 ppm C7H8 did not have a significant effect on the performance of the cell due to its hydrogenation to methylcyclohexane (C7H14). 77,78 The effects of a mixture of 2 ppm C7H8 with 0.2 ppm CO had the same effects than the CO alone. 78 However, when 20 ppm C7H8 was mixed with 2 ppm CO, the resultant overpotential increased to higher values than the sum of the individual contributions (Figure 9).…”

“…As the CO is adsorbed on the surface, the HOR and C7H8 hydrogenation compete for the active sites, hampering the fuel cell performance. 77 Angelo et al (2010) subsequently evaluated the effects of a mixture containing 0.2 ppm CO and 2 ppm C7H14. It was found that the effects on the performance were similar to the exposure of CO alone.…”