Modeling of Size Dependent Catalytic Activation Energies of Ag@Pd Spherical Core-Shell Nanoparticles

Abstract

The core/shell materials have attracted enormous attention as potential applications in diverse areas in biosensors, catalysts, and energy storage systems. Recently, Ag-Pd core-shell nanoparticles (NPs) have been synthesized and shown their superior electro- catalytic activity of small sizes for fuel-cell applications. On this line, the size-dependent catalytic activation energies based on the thermodynamics continuum model have first applied for different sizes of AgcorePdshell spherical NPs as diameters of 4-20nm. We have created AgcorePdshell NPs by following two routes as (i) the constant Ag core size with increasing thicknesses of Pd shells, (ii) the constant Pd shell thicknesses with different Ag core sizes. By expressing the surface to volume ratio for each size of model NPs, the size-dependent melting temperature of spherical Ag@Pd NPs have obtained. It has found that the melting temperatures of Ag@Pd NPs are below than those of the melting points of bulk materials for pure elements. Thus the catalytic activation energies at their melting points have also computed. Both the melting points and catalytic activation energies of those NPs reduce with the mole fraction of Pd atoms decrease. Our results are agreeing with experiment and molecular dynamics simulations.