Oxygen reduction reaction activity of Pd-based bimetallic electrocatalysts in alkaline medium

A series of 10 wt.% Pd-M (M: Ag, Ca, Co, Cu, Fe, Ni, Sn, Zn) / C electrocatalysts, with Pd to M mass ratio equal to 3:1, were prepared via the wet impregnation method, physicochemically characterized employing various techniques (BET, XRD, TEM, XPS) and electrochemically characterized towards their ORR activity in 0.1 M KOH solution using the RDE technique. Presence of alloy formations was revealed in the bulk of the Pd-Zn and Pd-Sn electrocatalysts. The highest ORR activity was exhibited by the Pd-Cu electrocatalyst, surpassing the activity of the 10 wt.% Pt/C reference. Specific ORR activity higher than that of 10 wt.% Pt/C was also exhibited, in descending order, by the Pd-Zn, Pd-Sn and Pd-Ni electrocatalysts. 10 wt.% Pd/C reference electrocatalyst exhibited the lowest ORR activity among all the tested samples. The superior ORR activity of the Pd-Cu electrocatalyst was mainly associated with an optimum Pd lattice strain.