Size-Dependent Activity of Gold Nanoparticles for Oxygen Electroreduction in Alkaline Electrolyte

The dependence of the kinetics of electrocatalytic oxygen reduction in basic electrolyte on the size of Au nanoparticles was determined for 3 and 7 nm clusters supported on carbon. The size-selected nanoparticles were prepared by reverse micelle encapsulation using PS−P2VP diblock copolymer, and the kinetic current for oxygen reduction was measured with a rotating disk electrode (RDE). The kinetic current was found to be 2.5 times higher for the 3 nm gold nanoparticles compared to the 7 nm gold nanoparticles at 23 °C. The 3 nm particles were found to facilitate four-electron electroreduction, whereas a two-electron electroreduction was inferred from the RDE data on the 7 nm particles. From experiments of the temperature-dependent current the apparent activation energy for the 3 nm clusters was found to be half that of the 7 nm clusters (0.1 and 0.2 eV, respectively).