This study proposes a novel layer wise anode structure to improve the CO-tolerance ability and utilization efficiency of catalyst. The layer wise structure consists of an outer and an inner catalyst layer. The outer catalyst layer acting as a CO barrier is composed of two nano-Ru layers (0.06 mg cm(-2)) by magnetron sputtering deposition method and a Pt-50-Ru-50 layer (0.10 mg cm(-2)) by screen-printing method on the GDL. The inner catalyst layer providing the hydrogen oxidation reaction is a pure Pt layer (0.07 mg cm(-2)) prepared by direct-printing method on PEM. The roles of the outer and inner catalyst layer relating to the improvement of CO-tolerance ability and utilization efficiency of catalyst for the proposed catalyst layer structure are investigated in this paper. SEM, X-ray, EDS and EPMA analysis were used to characterize microstructures, phases, chemical composition and distributions for the obtained electrocatalyst layers. The hydrogen fuel containing 50 ppm CO/hydrogen fuel containing 50 ppm CO + 2% O-2 is continuously fed to the anode side to investigate the dependence of CO-tolerance ability over time for the MEAs, respectively. The results demonstrate that this proposed anode catalyst layer structure presents a superior CO-tolerance ability and performance to those of conventional and Huag's structures in both oxygen free and oxygen present CO containing hydrogen fuels as well as pure hydrogen fuel. The filtering effect of the outer catalyst layer causes the improved CO-tolerance capability. (c) 2006 Elsevier Ltd. All rights reserved.