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 Pd-O, 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. (C) 2012 Elsevier B.V. All rights reserved.