Comparison of the stabilities and activities of Pt–Ru/C and Pt3–Sn/C electrocatalysts synthesized by the polyol method for methanol electro-oxidation reaction

Carbon-supported Pt, Pt–Ru, Pt3–Sn electrocatalysts have been synthesized by a modified polyol method. Energy dispersive spectroscopic (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopic (XPS) analyses reveal that the as-prepared samples are composed of mainly Pt and RuO2 or SnO2 and the formation of alloys is found only after heat-treatment at 200 °C in a flowing 10% H2–90% Ar atmosphere. The activity and durability for the methanol electro-oxidation reaction (MOR) have been evaluated by accelerated durability test (ADT) carried out by scanning the electrode potential for extended number of cycles in the potential ranges of 0.02–0.6, 0.02–0.8, and 0.02–1.2 V vs. NHE. Regardless of heat-treatment, the initial activity for MOR decreases in the order Pt–Ru/C > Pt3–Sn/C > Pt/C and the durability decreases in the order Pt/C > Pt3–Sn/C > Pt–Ru/C. During the ADT of the as-prepared Pt–Ru/C and Pt3–Sn/C, no detectable amount of dissolved Sn ions was found in the electrolyte solution, while almost 40% of Ru could be found in the electrolyte solution after ADT between 0.02 and 1.2 V vs. NHE. With MOR activity comparable to and durability better than that of Pt–Ru, the Pt-Sn based catalysts offer the potential to be employed as anode catalysts in direct methanol fuel cells.

► Catalytic activity and durability of Pt/C, Pt–Ru/C, and Pt3–Sn/C are compared.
► The activity of Pt–Ru/C decreases significantly when exposed to higher than 0.8 V.
► Significant amount of Ru dissolves out of Pt–Ru electrode, changing the surface characteristics.
► Pt3–Sn/C has higher durability than Pt–Ru/C.
► The Sn dissolution is negligible even at potential cycles up to 1.2 V.