An electrostatic attraction method is utilized for successfully attaching 10 nm Pd nanocubes on reduced graphene nanosheet (RGN) surfaces. The RGNs used to support the Pd nanocubes are prepared via both a sonoelectrochemical method (RGN(SECM)) and a chemical reduction method (RGN(CM)). X-ray photoelectron spectroscopic analyses indicate the domination of physical defects and C-OH groups on the surfaces of RGN(SECM) and RGN(CM), respectively. The linear scanning voltammograms, taken using rotating ring-disk electrode analyses in alkaline oxidation-reduction reactions (ORRs), show that the Pd nanocubes supported by RGN(SECM) (Pd cubes/RGN(SECM)) and RGN(CM) (Pd cubes/RGN(CM)) show improved onset potentials of 0.1 V on the order of Pd cubes/RGN(SECM) > Pd cubes/RGN(CM) > Pt/C similar to Pd/C > Pd nanocubes for their catalytic disk currents in the electron-transfer region. Mass-transfer-corrected Tafel diagrams demonstrate that RGN(SECM), which contains a greater number of physical defects, facilitated greater active sites of these Pd nanocubes due to its greater surface area, and thus better promoted ORRs. In terms of the kinetic current density, a greater mass activity (7.85 x 10(-2)mA.mu g(-1)) is observed for the Pd cubes/RGN(SECM) composite. Additionally, the durability test reveals that RGN(SECM) could provide good strength to stabilize Pd nanocubes during a long ORR period. (C) 2015 Elsevier Ltd. All rights reserved.