Enhancing ORR Performance of Bimetallic PdAg Electrocatalysts by Designing Interactions between Pd and Ag

Abstract

Precise tuning of the electronic properties of Ag/C using under potentially deposited (UPD) Cu and subsequent galvanic displacement to deposit atomically dispersed loading of Pd resulted in a robust bimetallic alloy with significant activity for the oxygen reduction reaction in alkaline media. The specific design of the catalyst and atomic arrangement of Pd–Ag outperforms conventional Pd/C and Ag/C commercial catalysts. The ORR activity of Pd deposited onto Ag/C was determined on the basis of rotating disk electrode voltammetry studies, showing a 2-fold increase in Pd mass activities compared to results obtained using Pd/C. While scanning transmission electron microcopy (STEM) coupled with electron energy loss spectroscopy (EELS) probed the uniformity of the nanoparticles, the origin of the outstanding activity was traced to the structural properties of the Pd–Ag interface as shown by X-ray absorption spectroscopy (XAS), along with X-ray photoelectron spectroscopy (XPS). Segregation of metals with a suitable geometric arrangement of the Ag to Pd ratio at the interface resulted in an increased performance where the active sites were key steps of oxygen bond breaking.