Mixing of a Pt-sputtered protic ionic liquid (PIL) containing 3,4-ethylenedioxythiophene and a carbon support at room temperature for 3 min produces carbon-supported Pt nanoparticles (Pt-NPs), in which the PIL acts as an adhesive. Its electrochemical oxidation generates a conducting poly(3,4-ethylenedioxythiophene) (PEDOT) network in the thin PIL layer that is present between Pt-NPs and the carbon support. The prepared material possesses high electrocatalytic activities toward oxygen reduction reaction and it exhibits high durability against carbon corrosion-inducing accelerated deterioration test.