Alloyed nanoparticles are promising electrocatalysts for electrochemical energy storage and conversion devices. However, syntheses of alloyed nanoparticles with controllable size and stoichiometry remain challenging. In this study, continuous, uniform and monodispersed bimetallic AgPd nanoparticles (NPs) with diameters similar to 10 nm are achieved by electrochemical synthesis from quaternary ionic liquid microemulsion (ILM) for use as electrocatalysts for ethanol oxidation reaction (EOR). It is found that the ionic liquid, 1-butyl-3-methyl-imidazolium chloride ([BMIMICI), acts not only as a soft template and co-surfactant for the formation of micro-reactors, but also as an electrolyte for enhancing conductivity. The stoichiometry (AgxPdy), size and size distribution of AgPd NPs can be accurately tuned by varying electrolyte composition, electrodeposition conditions, and ionic liquids concentrations. Attributed to the high surface area, optimal stoichiometric ratio, and strong attachment onto substrates without using organic binders, the as-deposited AgxPdy NPs exhibit extraordinary electrocatalytic activity and stability for EOR. It is found that the mass activity of Ag49Pd51 NPs/Pt electrode reaches 3360 mA mg(-1) for EOR in 1.0 M ethanol and 1.0 M KOH aqueous solution, which is much higher than commercial Pd/C catalyst (210.5 mA mg(-1)) and also the highest among state-of-the-art AgPd NPs electrocatalysts reported to date for EOR in alkaline media. (C) 2019 Elsevier Inc. All rights reserved.