Platinum-monolayer electrocatalysts Palladium interlayer on IrCo alloy core improves activity in oxygen-reduction reaction

We describe the synthesis and electrocatalytic properties of a new low-Pt electrocatalyst consisting of an IrCo core a Pd interlayer and a surface Pt monolayer emphasizing the interlayer s role in improving electrocatalytic activity for the oxygen reduction reaction on Pt in HClO4 solution We prepared the IrCo alloys by decomposing at 800 C hexacyanometalate KCoIr(cN)(6) adsorbed on the carbon surfaces The synthesis of Ir3Co/C involved heating a mix of metal salts and carbon in hydrogen at 500 degrees C Thereafter we placed a palladium and/or platinum monolayer on them via the galvanic displacement of an underpotentially deposited copper monolayer The electrocatalysts were characterized using structural- and electrochemical techniques For Pt-ML/Pd-ML/IrCo/C we observed a Pt mass activity of 1 18 A/mg((Pt)) and the platinum group-metals mass of 0 16 A/mg((Pt Pd Ir)) In comparison without a Pd interlayer le Pt-ML/IrCo/C the activities of 0 15 A/mg(pt) and 0 036 A/mg((Pt Pd Ir)) were considerably lower We consider that the palladium interlayer plays an essential role in achieving high catalytic activity by adjusting the electronic interaction of the platinum monolayer with the IrCo core so that it accelerates the kinetics of adsorption and desorption of the intermediates of oxygen reduction A similar trend was observed for Pt-ML/Pd-ML, and Pt-ML deposited on Ir3Co/C alloy core We used density functional theory to interpret the observed phenomena (C) 2010 Elsevier B V All rights reserved