Ultrasound-assisted polyol synthesis and electrocatalytic characterization of PdxCo alloy and core-shell nanoparticles

► Core-shell and alloyed PdxCo (x = 3, 4, and 8) nanoparticles (NPs) supported on carbon were synthesized by an ultrasound-assisted polyol process. ► They show greatly enhanced electrocatalytic activity towards the oxygen reduction reaction compared with Pd NPs. ► The core-shell Pd4Co NPs showed activity comparable to that of Pt NPs.