Fuel cell contaminants toluene

Li, H., et al. 2009. PEM fuel cell contamination Effects of operating conditions on toluene-induced cathode degradation. /. Electrochem. Soc. 156 B252-B257. 

Steady-state polarization curves of a fuel cell contaminated by toluene in the air stream. Operating conditions stoichiometry 1.5/3.0 for Hj/air RH 80% cell temperature 80°C back pressure 30 psig. MEA anode/cathode Pt loading 0.4 mg cm". (From Li, H. et al. 2008. /. Power... 

One of the difficulties in fuel cell contamination modeling is estimating the unknown ORR parameters. In the case of no toluene being present, we needed to know the forward and backward reaction rates or their ratios for reaction (6.36) to reaction (6.38). To do this, we simulated experimental baseline data free of toluene contamination. The parameters used for the simulation are listed in Table 6.1, and the modeling results and experimental polarization curves are shown in Figure 6.3. 

FIGURE 8.14 Voltage versus time curves with various levels of toluene at different current densities. Cell temperature = 80°C, Relative humidity = 80%, 30 psi back pressure, stoichiometry 1.5/3.0 for Hj/air. (Reprinted from Journal of Power Sources, 185, Li, H. et al. Polymer electrolyte membrane fuel cell contamination Testing and diagnosis of toluene-induced cathode degradation, 272-279, Copyright (2008), with permission from Elsevier.)... 

Li, H., Zhang, J. L., Fatih, K. et al. 2008. Polymer electrolyte membrane fuel cell contamination Testing and diagnosis of toluene-induced cathode degradation. Journal of Power Sources 185 272-279. 

The class of chemicals designated as VOCs includes a wide range of carbon-based molecules of sufficient vapor pressure to be present in the air, such as aldehydes and ketones. The most common VOC is methane, the primary component of nafural gas. There are various sources, both natural and human, of VOCs. The response of the fuel cell to VOCs will vary significantly, depending on the molecules in question, but can be significant. For example, benzene and toluene at the ppm level have both been found to significantly affect performance, with the dominant effect believed to be due to adsorption on the catalyst surface resulting in kinetic losses. A semiem-pirical model for toluene contamination based on kinetic losses is described in chapter 3, section 3.8. 

Hui et al. [29] conducted toluene contamination tests at different toluene concentrations. They also studied the effects of different operational conditions on toluene contamination, including the effects of fuel cell relative humidity (RH), of Pt loading in the cathode catalyst layer, of back pressure, and of air stoichiometry [30]. Figure 3.8 shows a set of representative results of contamination tests at 1.0 A cm with various levels of toluene concentration in the air. It can be seen that the cell voltage starts to decline immediately after the introduction of toluene, and then reaches a plateau (steady state). These plateau voltages indicate the saturated nature of the toluene contamination. For example, the cell voltage drops from 0.645 V to 0.522 V at 1.0 A cm-2 within 30 min of the cathode... 

Semiempirical Model for Fuel Cell Performance in the Presence of Toluene In the presence of toluene in the air stream, the fuel cell performance degraded. Figure 3.15 illustrates two sets of representative results of toluene contamination tests, conducted with various levels of toluene concentration at current densities of 0.75 and 1.0 A cm , respectively. The cell voltage experienced a transient period (nonsteady state) immediately after the introduction of toluene, then reached a plateau (steady state). The duration of the transient period and the magnitude of the cell voltage drop to the plateau were strongly dependent on toluene concentration and current density. 

As discussed eariier, the effect of toluene contamination on PEM fuel cell performance features a transient decay followed by a plateau in the cell performance. The performance plateau represents the maximum performance depression (MPD %) that toluene can cause to the cell performance at a given current density and toluene concentration. Based on the difference... 

Effects of toluene contamination on transient fuel cell performance at different current densities (a) 1,. (d) 1,. = 1.0 Acm". (From Shi, Z. et al. Power Sources, 186 (2009) 435. With permission.)... 

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