The graphene-supported palladium and palladium-yttrium nanoparticles for the oxygen reduction and ethanol oxidation reactions: Experimental measurement and computational validation

Oxygen reduction and ethanol oxidation reaction (ORR and EOR) have been studied on graphene nanosheet-supported (GNS) pure Pd and Pd₃Y nanoscale-alloy (Pd/GNS and Pd₃Y/GNS) electrocatalysts. The electrochemical studies were carried out for ORR both in acidic and alkaline solutions employing a rotating disk electrode (RDE), and performed for EOR in alkaline media with cyclic voltammetry method. The structure and composition of the Pd and Pd₃Y nanoparticles were verified using TEM, XRD and XPS. We combine the experimental measurements with ab initio density functional theory (DFT) calculations to identify the d-band center position of Pd atom in the pure Pd and Pd₃Y alloys as a function of site on near the surface. Both approaches clearly show that alloying the Pd with Y significantly modifies the electronic structures of Pd atoms. Core-level of Pd 3d_5/2 shifts to a negative value, which increases the d-band center of Pd atom and enhances the bond strength of PdO, which implies good catalysts for EOR but ORR. Our results indicate that the electronic structure of the Y-modified bimetallic Pd alloy is a good descriptor for the catalytic activity.