Anode contamination

During normal cell operation the anode contaminants that are more electrochemically active than copper (and less than hydrogen), mainly arsenic. 

Anode contamination by fuel impurities such as traces of H2S or NH3 are more irreversible than CO poisoning. Catalyst deactivation by H2S can be partially relieved by bringing the anode to oxidizing potentials and subsequent operation under hot and humid conditions [43]. 

The slow kinetics of the cathode oxygen reduction reaction (ORR) plays the key role in limiting PEMFC performance when pristine hydrogen is used as the fuel. Therefore, improving the catalytic activity for the ORR has drawn most of the research attention in catalysis studies. Cathode contamination has attracted less attention compared with anode contamination, and only a limited number of papers have been published. Pollutants in air include NOx (NO2 and NO), SOx (SO2 and... 

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] ... 

Anode Contaminants/Impurities and Their Basic Chemistry.54... 

Contaminants/impurities at the anode are mainly brought in by the fuel feed stream. Impurities in the hydrogen fuel, such as CO, H2S, NHj, organic sulfur-carbon, as well as carbon-hydrogen compounds, are primarily from the manufacturing process, in which natural gas or other organic fuels are reformed to produce hydrogen. In this section, several major anode contaminants, such as CO H2S, and NH3, will be discussed. 

Several mitigation methods for anode contamination are briefly introduced, mainly centered on CO mitigation. The addition of Ru to Ft is the widely adopted scheme to generate excellent CO tolerance. Elevating the operation temperature (>80°C) may improve the tolerance to impurities that poison the catalyst through adsorption, but the adoption of a novel proton exchange membrane is necessary. Chemical oxidants, like H2O2 or just O2, can be bled into the anode stream to react with CO and excellent results can be expected. Other than that, electrochemical methods, such as current or potential pulse, cyclic voltammetry, and OCV operation, have also been explored for the removal of CO and H2S. 

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