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 3d5/2 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.

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► Uniformly dispersed Pd and Pd3Y nanoparticles on GNS at loadings up to 60 wt.%.
► Electrocatalytic activities of the Pd and bimetallic Pd–Y alloy for ORR and EOR.
► Experimental and theoretical validation of electronic structure on Pd in the Pd and Pd3Y.
► Fundamental relationship between d-band center position and activity for ORR and EOR.