Carbon monoxide (CO) in hydrogen reformed from carbon based fuels is known to degrade the performance of a proton exchange membrane fuel cell (PEMFC) by poisoning the anode active sites, as shown in Reaction 1:Pt+CO→Pt−CO  [1]
To mitigate the detrimental effects of CO on the performance of a PEMFC, researchers have explored ways to modify fuel cell operation including using elevated temperatures (e.g., 120° C.), air bleeding, in situ voltage pulsing, and the like. Even with these techniques, fuel cells may not tolerate the concentration level of CO coming out of a reformer, which is typically 0.1-1% (1000-10,000 ppm). To reduce the CO concentration in reformate H2 to parts per million levels, methods such as pressure swing adsorption, preferential oxidation, or catalytic methanation can be used. However, volume, weight, power, and fuel-efficiency penalties may be substantial when using these methods, particularly for small-scale fuel cell systems. A single-cell electrochemical CO filter external to the fuel cell has been previously proposed. This filter lowers the CO concentration by periodically oxidizing the adsorbed CO via the following reaction 2:Pt−CO+H2O→Pt+CO2↑+2H++2e−  [2]
However, low exit CO concentrations and a high selectivity of CO to H2 oxidation could not be simultaneously achieved due to the reformate continuously flowing through the filter cell during oxidation.
As such, a fuel cell that can effectively the issue of CO degradation in performance would be desirable. A method that utilizes such fuel cells would also be beneficial.