An anode structure comprising a ruthenium catalyst is disclosed. The catalyst consists essentially of ruthenium deposited on a conducting support wherein the ruthenium is in metallic form or in a form that is readily reducible to the metallic form at temperatures of 25.degree. C. to 150.degree. C. The anode structure is particularly of use in proton exchange membrane fuel cell to prevent poisoning of the electrocatalyst by impurities in the fuel stream to the anode.