Abstract

The core-shell nanoparticles embedded on reduced graphene oxide (rGO) nanosheets usually exhibit enhanced catalytic activity because of their lattice strain effect. In this study, rGO supported core-shell Au-Pd nanoparticles (Au@Pd/rGO) were synthesized by a facile one pot sonochemical method and studied for their enhanced catalytic activity. The ultrasonic liquid processor at the frequency of 20 kHz and the power of 40 W (with an amplitude of 35%) was used to perform the synthesis. The existence of the spherical shaped Au core and size controlled Au-Pd core-shell nanoparticles incorporated into the rGO nanosheets were identified using high resolution transmission electron microscopy (HR-TEM) and high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) analyzes. The ordered nature and the elemental presence of Au@Pd/rGO and the mapping were studied using Raman, X-ray photoelectron (XPS) and energy dispersive X-ray (EDS) spectroscopic analyses, respectively. The electrode modified with Au@Pd/rGO deliberately showed an improved electrocatalytic activity for the oxygen reduction reaction (ORR). The kinetics involved in the ORR was intensively studied using the rotating disk electrode (RDE) and identified as the developed Au@Pd/rGO possessed a better catalytic activity compared to Au/rGO and analogous activity with the other standard ORR catalysts such as Pd-20/C and Pt-20/C. The number of electron exchanged for the reaction was calculated as four using Koutecky-Levich (K-L) plot.