Effects of anode air bleeding on the performance of CO-poisoned proton-exchange membrane fuel cells

In the present work, the dynamic behavior of a PEM fuel cell under CO-poisoning and the effects of air bleeding on the recovery ratio are reported. Pt-Ru catalyst is used as the anode in a single cell and the hydrogen is pre-mixed with 53 ppm of CO as the fuel. The result indicates that even using a CO-tolerant catalyst, CO-poisoning cannot be avoided with the operating conditions in our study. About 80% of the output current is lost within 20 min. Upon anode air bleeding with 5% air, 90% of the current is recovered within 1 min. Higher air bleeding ratio only results in minor improvement of the cell performance. We have developed a transient model to estimate the current reduction due to CO-poisoning and to evaluate the amount of air bleeding needed for a given recovery ratio. A long-term durability test has also been conducted using simulated reformatted gas, in which 1% O₂ is injected into the fuel stream. After more than 3000 h, the cell voltage degradation is less than 3%.