Incorporation of cobalt into Pd2Sn intermetallic nanoparticles as durable oxygen reduction electrocatalyst

Intermetallic compounds (IMCs) can enhance the electrocatalytic performance of the oxygen reduction reaction (ORR) because of their definite composition and structure and strong electron interaction. Here, we present a one-pot synthesis of structurally ordered Pd2Sn and Pd6Sn3Co nanoparticles supported on carbon material at low temperature without utilizing surfactant. Both XRD and high-resolution TEM results confirm the formation of IMC phase. The incorporation of Co atoms into Pd2Sn leads to a lattice contraction. EDX line scan analysis and ICP-AES demonstrate that the Pd:Sn:Co atomic ratio of ordered Pd6Sn3Co IMC is close to its nominal composition. The X-ray photoelectron spectroscopy indicates that the binding energies of Pd 3d3/2 and Pd 3d5/2 within the Pd6Sn3Co IMC are upshifted as compared with the Pd2Sn IMC, suggesting that a down-shift of d-band center relative to the Fermi level. This shift could explain that the Pd6Sn3Co IMC catalyst exhibits a higher activity and much better durability for the ORR in alkaline medium than the commercial Pt/C and Pd2Sn IMC catalysts.