Investigation of carbon monoxide tolerance in proton exchange membrane fuel cells

The need for an efficient, low-polluting power source for vehicles in urban environments has resulted in increased attention to the option of fuel cell powered vehicles. Of the various fuel cell systems considered, the hydrogen fueled proton exchange membrane (PEM) fuel cell technology seems to be the most suitable one for the terrestrial transportation applications.; A chief current research goal is the design of PEM fuel cells that can operate with impure hydrogen containing traces of CO, which has been the objective of this research. Standard Pt and PtRu anode catalysts have been studied systematically under practical fuel cell conditions, in an attempt to understand the mechanism and kinetics of H2/CO electrooxidation on these noble metal catalysts. In the study of Pt as anode catalyst, it was found, thus, that the fuel cell performance is strongly affected by the anode flow rate and cathode oxygen pressure. This was found to be due to the fact that there is finite CO electrooxidation even on Pt anode with H2/CO as anode feed.; For PtRu anode catalyst, sustained potential oscillations were furthermore observed when the fuel cell was operated at constant current density with H2/CO as anode feed. Temperature was found to be the key bifurcation parameter besides current density and the anode flow rate for the onset of potential oscillations. The anode kinetic model was further extended to the unsteady state which could reasonably reproduce and adequately explain the oscillatory phenomenon.; It was further found that a PEM fuel cell operated in an autonomous oscillatory state produces higher time-averaged cell voltage and power density as compared to the stable steady-state operation, which may be useful for developing an operational strategy for improved management of power output in PEM fuel cells in the presence of CO in anode feed. (Abstract shortened by UMI.)...