The electrocatalytic activities of Pt0.8Ir0.2, Pt0.5Cu0.5, Pt0.67Cu0.33, Pt, and Ir for ammonia oxidation have been studied comparatively in KOH solutions by cyclic voltammetry and potentiostatic polarization. The anodic oxidation began on Ir at a lower potential than on Pt by about 0.1V, whereas the oxidation peak current density on Ir was much lower than that on Pt. On the binary alloy of Pt0.8Ir0.2, the oxidation started at slightly lower potential than on Pt, and the peak current density was slightly higher than that on Pt. In contrast, Pt0.5Cu0.5 and Pt 0.67Cu0.33 alloys showed almost the compatible activity inferior to Pt. These facts suggested that alloying in the Pt-Ir binary system may lead to the enhancement of ammonia oxidation activity due to a kind of cooperative interaction between Pt and Ir.
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