Simple preparation method of Pd nanoparticles on an Au electrode and its catalysis for dioxygen reductionElectronic supplementary information (ESI) available: XRD pattern of an evaporated Au electrode and CVs for the reduction of O2 on a bare Au(111) electrode or a Pd-nanoparticle-film-modified electrode. See: http://www.rsc.org/suppdata/nj/b3/b300566f/

Abstract

A simple method for the fabrication of Pd nanoparticles is described. The three-dimensional Pd nanoparticle films are directly formed on a gold electrode surface by simple electrodeposition at −200 mV from a solution of 1 M H2SO4 + 0.01 mM K2PdCl4. X-Ray photoelectron spectroscopy verifies the constant composition of the Pd nanoparticle films. Atomic force microscopy proves that the as-prepared Pd nanoparticles are uniformly distributed with an average particle diameter of 45–60 nm. It is confirmed that the morphology of the Pd nanoparticle films are correlated with the electrodeposition time and the state of the Au substrate. The resulting Pd-nanoparticle-film-modified electrode possesses high catalytic activity for the reduction of dissolved oxygen in 0.1 M KCl solution. Freshly prepared Pd nanoparticles can catalyze the reduction of O2 by a 4-electron process at −200 mV in 0.1 M KCl, but this system is not very stable. The cathodic peaks corresponding to the reduction of O2 gradually decrease with potential cycling and at last reach a steady state. Then two well-defined reduction peaks are observed at −390 and −600 mV vs. Ag/AgCl/KCl (sat.). Those two peaks correspond to a 2-step process for the 4-electron reduction pathway of O2 in this neutral medium. The former peak is ascribable to the 2-electron reduction of O2 to H2O2, while the latter is assigned to the reduction of H2O2 to H2O. The observed electrocatalysis for the reduction of O2 is attributable to the extraordinary catalytic activity of the Pd nanoparticles over the bulk gold electrode.