Anode Catalyst Layer Degradation

1 Anode Catalyst Layer Degradation Caused by Contamination 

3 lists U.S. National Ambient Air Quality Standards (NAAQS). In high air pollution regions, especially in developing countries and industrial areas, the pollutant concentration can exceed the amounts in Table 23.3. Traces of metal ions, especially Fenton agent such as Fe and Cu, coming from the humidifier or other components are also harmful to the ionomers in the catalyst layer. The effect 

CO poisoning of the Pt electrocatalyst in the anode causes fuel cell performance loss. The effect of CO poisoning on fuel cell performance is strongly 

it would be expected that the best performance would occur on an electrode where Ru and Pt atoms are adjacent to one another. However, oxidation of Ru causes Ru to dissolve and cross over to the cathode, resulting in eelt performance decline. This will be discussed in the following section. 

2 Anode Contamination by Sulfur-containing Species Sulfur-containing species, such as sulfur dioxide (SO2) and sulfur hydrogen (H2S), in the fuel or air stream of a fuel cell are also strongly adsorbed on the Pt eatalyst surface. H2S can be catalyzed by Pt to form Pt-Sajs and H2 on the Pt surfaee [58]  

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As a summary, we conclude that overall hydrogen starvation results in negative cell voltage and carbon corrosion in addition to water oxidation within the anode catalyst layer. Degradation reaction rates increase with decreasing fuel stoichiometry. 

Anode Catalyst Layer Degradation-Voltage Reversal... 

Figure 17.5. The dependence of the Pt ratio to Ru, Pt/(Ru + Pt), of the anode catalyst layer after the cell voltage reversal experiment for 2 min, determined by EDX on the sample location [19]. (Reprinted from Journal of Power Sources, 130(1-2), Taniguchi A, Akita T, Yasuda K, Miyazaki Y, Analysis of electrocatalyst degradation in PEMFC caused by cell reversal during fuel starvation, 42-9, 32004, with permission from Elsevier.)...

They also found that ruthenium dissolution from individual catalyst particles occurred in the anode catalyst layer, the most severe degradation occurring in the anode plane and the area close to the outlet region. 

The described experiments and simulations support Reiser et al. s theory of the RCD mechanism. This mechanism occurs during start-up and shutd-own of the cell provided that the anode is not completely filled with hydrogen or air. Carbon and water are oxidized in the cathode catalyst layer, resulting in a reverse current and cell degradation. 

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