A preferential oxidation of CO remaining in reformed H-2 fuels (PROX) is one of the processes to avoid a serious poisoning of anode-catalysts in fuel cells. The crucial requirement for the PROX catalyst is high CO oxidation rate with high selectivity at low-temperatures of less than or equal to200 degreesC. We propose new Pt-Fe/mordenite catalysts for the PROX, which is extremely superior to conventional Pt/Al2O3 catalysts, even to our Pt/mordenite. TEM observation showed that the most parts of metal catalysts were loaded in mordenite molecular pores. The performances were examined in comparison with Pt/mordenite at various experimental conditions. i.e. temperature ranges (80-300 degreesC), gas-compositions including water vapor, gas hourly space velocities (GHSV: 20,000-80,000 h(-1)) or the compositions of metal-catalysts supported on mordenite, and found to exhibit a sufficient stability for the whole experimental period. On Pt-Fe/mordenite, we show a complete removal of CO with 100% selectivity by the addition of stoichiometric amount O-2 from a simulated reformate, e.g. 1% CO, 25% CO2, 20% H2O and H-2 balance. at 80-150 degreesC with an extremely high GHSV (similar to80,000 h(-1)). FTIR and TPD data showed that CO coverage and CO bond strength on Pt are extremely lowered by the combination with Fe. (C) 2003 Elsevier B.V. All rights reserved.