An essential requirement for the proton exchange membrane fuel cell (PEMFC) is to deliver clean H-2 to the anode electrode, the kinetics of which are greatly hindered by traces of CO present from the upstream hydrocarbon reforming and water-gas shift processes. The removal of CO from hydrogen-rich stream to-a PEMFC tolerant level, by selective oxidation (SELOX) of CO, has been studied over 1%Pt/Al2O3, 1%Pt-1%Sn/Al2O3, 1%Pt/Nb2O5 and 1%Pt-1%Sn/Nb2O5 catalysts. The Nb2O5-supported catalysts presented higher activity in SELOX reaction at low temperatures, but with lower CO selectivity. The results were explained in terms of platinum modification by the presence of niobia (SMSI effect) and tin (bimetallic effect). (c) 2005 Elsevier B.V. All rights reserved.