normalPt1−xnormalMx (M=Ru,Mo,Co,Ta,Au,Sn) random alloy samples, covering most of the binary composition range, have been prepared via magnetron sputtering. The alloys were deposited through shadow masks onto 3M nanostructured thin-film catalyst support for testing in a 64-electrode polymer electron membrane fuel cell (PEMFC). CO stripping voltammograms and hydrogen oxidation polarization curves with pure hydrogen and with reformate containing up to 50ppm CO were measured on all the samples. In agreement with reports in the literature, Ru, Mo, and Sn were found to improve the CO tolerance of Pt, although the intrinsic hydrogen oxidation activity of Pt decreased significantly as the Sn content increased. The addition of Co to Pt had no impact on CO tolerance, possibly because of loss of surface Co through dissolution in the fuel cell. The addition of Au to Pt led to an increase in hydrogen oxidation overpotential when CO was present. Small amounts of Ta gave a small reduction in hydrogen oxidation overpotential in the presence of CO, but the overpotentials were still too high for practical application in a reformate-fed fuel cell.

A ternary composition spread, ͑Pt 1−x Ru x ͒ 1−y Mo y , 0 Ͻ x Ͻ 1; 0 Ͻ y Ͻ 0.3, was prepared through sputter deposition onto a nanostructured thin film support. The film was found to be reasonably stable when exposed to acid at 80°C, although there was evidence for loss of some Mo, presumably through a corrosion mechanism. The catalytic activity towards hydrogen oxidation of this composition range was measured simultaneously in a 64-electrode proton exchange membrane fuel cell with emphasis on performance in the presence of CO. The addition of either Mo or Ru to Pt led to a reduction in hydrogen oxidation overpotential for a simulated reformate gas stream containing up to 50 ppm CO. The best performance under CO-containing reformate was found for compositions containing both Ru and Mo, e.g., Pt 0.40 Ru 0.35 Mo 0.25 . The performance observed was significantly better than that measured on compositions containing Pt and Ru only. The use of air bleed was found to be most beneficial for compositions containing predominantly Pt and Ru.Proton exchange membrane ͑PEM͒ fuel cells have the potential to replace the internal combustion engine for automotive applications. In these fuel cells, hydrogen reacts electrochemically with oxygen from the air to generate electricity and water. Platinumbased catalysts are typically used for both the hydrogen oxidation reaction ͑HOR͒ and oxygen reduction reaction in order to allow the reactions to proceed at reasonable rates. Maximum efficiency and durability are obtained when using pure hydrogen as fuel. Significant progress has been made by automotive original equipment manufacturers demonstrating prototype vehicles with on-board storage of hydrogen and fuel cell power plant efficiencies sufficient for driving ranges approaching 300 miles. Due to the significant engineering and cost issues with on-board reforming, the practicality of that approach is no longer pursued by any fuel cell vehicle integrator, while the number of fleet vehicle hydrogen refueling stations is steadily increasing as the issues with developing the hydrogen supply and delivery sides of the equation are studied. However, impurities in the hydrogen fuel and air supplies remain as critical topics for research, regardless of the original source of hydrogen, or local operating environment of the vehicle. Hydrogen will be produced for prototype vehicles from both reformed hydrocarbon fuels and electrolyzers. Modern reformers typically produce a hydrogen gas stream containing high amounts of CO 2 and nitrogen together with trace amounts of CO ͑e.g., 1-50 ppm͒. 1 Even very low ͑1 ppm͒ levels of residual CO can poison the catalytic platinum surface of the anode, and large overpotentials ͑300-400 mV͒ are required to oxidize the adsorbed CO and recover all the platinum surface to catalyze the HOR. 2 There is thus a continuing need to develop COtolerant hydrogen oxidation catalysts.Of all the platinum alloys tested, platinum-ruthenium alloys, typically around the 1:1 composition, are the only ones to have been introduced co...

The hydrogen oxidation catalytic performance of a ternary composition spread (Pt1-xRux)1-yMoy sample has been determined in a 64-electrode proton exchange membrane fuel cell. Linear gradients of the three elements were sputter deposited onto 3M's nano-structured thin film support through a shadow mask to produce 64 different, electrically isolated, catalyst compositions. CO stripping voltammetry showed that pre-adsorbed CO was removed at lower potentials as the ruthenium content increased. The presence of Mo generated a redox couple, broadened the CO stripping peak and reduced its intensity. In the presence of CO in reformate, the hydrogen oxidation overpotential decreased as the ruthenium content increased, in agreement with previous experimental studies reported in the literature on Pt1-xRux binary alloys. At intermediate ruthenium content, the overpotential could be further reduced through the incorporation of some molybdenum. At high Ru/Mo content, the hydrogen oxidation overpotential was high, presumably due to the resultant low Pt content.