Selective knockout of gold active sites.

KEYWORDS Electrochemistry • gold • kinetics • radicals • voltammetry 2 ABSTRACT It has long been known that defects on a gold surface play an important role in electrocatalysis, but the precise mechanism has always been unclear. This work indicates that the defect sites provide partially filled d-orbitals that stabilize free-radical intermediates. Strong evidence for this hypothesis is that the sites can be selectively knocked out by treatment with OH • radicals generated by Fenton's reagent. The knockout effect is demonstrated using oxygen reduction, hydrogen reduction, and the redox electrochemistry of hydroquinone.