Ultrasmall and homogeneous bimetallic Pd_xBi nanoalloys are well distributed on a Vulcan carbon support by a facile, low-cost synthetic strategy. The electrochemical activity of the as-prepared homogeneous Pd_xBi nanoalloy/carbon black nanocomposites is closely related to the content of Bi, revealing their excellent electrocatalytic performance for selective oxidation of monohydric alcohols and vicinal diols in alkali medium.