Dynamic Behavior of a PEM Fuel Cell During Electrochemical CO Oxidation on a PtRu Anode

The dynamic behaviour of a single PEM fuel cell (PEMFC) with a PtRu/C anode catalyst using CO containing H₂ as anode feed was investigated at ambient temperature. The autonomous oscillations of the cell potential were observed during the galvanostatic operation with hydrogen anode feed containing CO up to 1000 ppm. The oscillations were ascribed to the coupling of the adsorption of CO (the poisoning step) and the subsequent electrochemical oxidation of CO (the regeneration step) on the anode catalyst. The oscillations were dependent on the CO concentration of the feed gas and the applied current density. Furthermore, it was found that with CO containing feed gas, the time average power output was remarkably higher under potential oscillatory conditions in the galvanostatic mode than during potentiostatic operation. Accompanying these self-sustained potential oscillations, oscillation patterns of the anode outlet CO concentration were also detected at low current density (<100 mA/cm²). The online measurements of the anode outlet CO concentrations revealed that CO in the anode CO/H₂ feed was partially electrochemically removed during galvanostatic operation. More than 90% CO conversion was obtained at the current densities above 125 mA/cm² with low feed flow rates (100–200 mL/min).