New methanol-tolerant catalysts in the form of 27 nm, 48 nm, and 63 nm palladium nanocubes enclosed by {1 0 0} facets were successfully used for the oxygen reduction reaction (ORR) in a 0.5 M H2SO4(aq) solution. Based on X-ray photoelectron spectroscopy and high resolution transmission electron microscopy analyses, the surface of the smallest Pd nanocubes was easily oxidized to PdO. The data provided by the analysis of a mass-transfer-corrected Tafel curve in a free methanol electrolyte showed that the specific activities of the 27 nm, 48 nm, and 63 nm Pd nanocubes at 0.65 V (vs. Ag/AgCl) in terms of the kinetic current density (j(k)) were 11.51 x 10(-2) mA cm(-2), 12.32 x 10(-2) mA cm(-2), and 10.06 x 10(-2) mA cm(-2), respectively. In contrast, Pd and Pt nanoparticles featured specific activities of 3.7 x 10(-2) mA cm(-2) and 13.2 x 10(-2) mA cm(-2), respectively. Further Tafel analyses conducted using a rotating ring-disk electrode in a methanol electrolyte showed that the j(k)s of the 27 nm, 48 nm, and 63 nm Pd nanocubes at 0.65 V (vs. Ag/AgCl) were 14.87 x 10(-2) mA cm(-2), 16.55 X 10(-2) mA cm(-2), and 12.98 x 10(-2) mA cm(-2), respectively. The nanocubes have a high activity toward the ORR; the greatest j(k) was occurred on the 48 nm nanocube even larger than 5.65 x 10(-2) mA cm(-2), the j(k) of the Pd nanopartides in the methanol electrolyte, where Pt nanoparticles effected methanol oxidation in preference to the ORR. Despite working in methanol-tolerant solutions, the prepared 48 nm Pd nanocubes exhibited high electroactivity. (C) 2012 Elsevier B.V. All rights reserved.