Carbon‐supported catalysts of Pt, Pt/Ru, Pt/Ru/W, and Pt/Ru/Pd were evaluated for the electro‐oxidation of methanol in phosphoric acid at 180°C. These catalysts were characterized using cyclic voltammetry and x‐ray diffraction. Addition of Ru to a 0.5 mg/cm2 Pt catalyst (1:1 atomic ratio) caused a large reduction in polarization. The open‐circuit voltage was reduced by 100 mV and polarization at 400 mA/cm2 was reduced by 180 mV. A Pt/Ru (5:2) catalyst with the same Pt content lowered the open‐circuit voltage 70 mV. Additions of W to form Pt/Ru/W (1:1:1, atomic ratio) and Pd to form Pt/Ru/Pd (2:2:1), all with the same platinum loading, gave the same performance as Pt/Ru (1:1) without the additions. All of the catalysts showed two Tafel slopes, 140 mV/dec at lower polarizations and 100 to 120 mV/dec at higher polarizations, indicating that the reaction mechanisms are the same for all of the catalysts. Methanol oxidation is greatly enhanced at 180°C in phosphoric acid compared to the lower operating temperatures of a perfluorosulfonic acid electrolyte. The exchange current density for methanol oxidation is higher than that for O2 reduction. Ru metal dissolves from catalysts at high potentials. Hydrogen oxidation in the presence of 1 mole percent carbon monoxide showed carbon monoxide tolerance in the order: Pt/Ru/Pd > Pt/Ru > Pt.

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Proton exchange membrane (PEM) fuel cells are typically classified as methanol-based or hydrogen-based depending on the fuel used to convert chemical energy into electricity. Although direct methanol fuel cells have advantages of fuel availability and storage, long unsolved problems of poor anode kinetics and high methanol crossover limit their potential use mainly to applications with low power requirements, such as portable appliances.

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Five carbon-supported Pt/Ru-based catalysts ͑Pt/Ru, Pt/Ru/Os, Pt/Ru/Au, Pt/Ru/SnO x , and Pt/Ru/WO x ) were studied for electrooxidation of H 2 and H 2 with 1% CO at the anode of a proton exchange membrane fuel cell. For H 2 oxidation, the performance of the Pt/Ru anode was not affected by addition of W, Os, and Au. However, the Pt/Ru/SnO x catalyst was found to result in a very poor performance for H 2 oxidation. For electro-oxidation of H 2 with 1% CO, the Pt/Ru/WO x catalyst was the most active catalyst and the Pt/Ru/Au catalyst was the poorest. Pt/Ru/WO x was almost twice as active as the Pt/Ru catalyst at practical potentials. A new intermediate mechanism was proposed to explain the CO tolerance of Pt/Ru-based catalysts.