Three kinds of Au-modified Pd catalysts with the alloy, core-shell and physically-mixed structures are prepared with carbon nanotubes as the support. The structural details and the particle sizes of the prepared catalysts are characterized by X-ray diffraction and transmission electron microscopy. The experimental results indicate that the Au-modified Pd catalysts show smaller particle sizes with narrower particle size distributions than the mono-Pd catalyst does. The catalytic activities of the prepared catalysts for oxygen reduction and ethanol oxidation are examined by electrochemical measurements. Compared with the mono-Pd catalyst, the Au-modified Pd catalyst with the physically-mixed structure exhibits increased catalytic activity for oxygen reduction, but decreased catalytic activity for ethanol oxidation in alkaline media. The cell performance with the Au-modified Pd as the cathode catalyst yielded a peak power density of as high as 185 mW cm(-2), which is about 1.4 times higher than that with the mono-Pd cathode. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.