The selective oxidation of carbon monoxide in a hydrogen-rich stream is an important reaction in fuel cell technology. Fuel cells that use hydrogen produced from a combustion source contain small amounts of CO that must be removed to extremely low levels (< 10 ppm), otherwise, it will poison the anode of the polymer electrolyte fuel cells (PEFC). Our research group has developed an improved Pt catalyst on alumina using a water-pretreatment method. However, at temperatures below 100degreesC, water from the hydrogen-oxidation side reaction accumulates on the catalyst causing it to deactivate. To better understand the deactivation, the water-pretreated catalyst was characterized at room temperature (28 degreesC) and at 50 degreesC with various reaction conditions (O-2 and H2O concentration) by analyzing the activity of the catalyst and by measuring the reactor temperature profile using an infrared (IR) camera. The IR images clearly showed a decrease in the reactor temperature over time indicating the deactivation of the catalyst. As the catalyst became more deactivated, the reactor temperature decreased, the H-2 and CO conversions decreased, while the CO selectivity increased to nearly 100%. (C) 2003 Elsevier B.V. All rights reserved.