Abstract
Underpotential deposition (UPD) of Cu ad-layers onto gold electrodes in an alkaline solution was investigated, for the first time. Modified single crystal Au(111) and polycrystalline Au electrodes were applied to oxygen reduction reaction (ORR) using rotating ring-disk electrode hydrodynamic voltammetry in an O2-saturated 0.1 M NaOH solution. In comparison to bare substrate, a considerable enhancement of the disproportionation of hydrogen peroxide was observed at all Cu-modified Au electrodes. Additionally, the well-pronounced positive shifts of the reduction waves were attributed to the enhancement of the catalytic activity towards both the two-electron reduction steps of O2 to HO2- and OH- at the Cu-modified electrodes. Very interestingly, the direct four-electron ORR took place at potentials more negative than ca. -0.8 V vs. Ag|AgCl, which is ca. 400 mV more positive than what is shown at a bare polycrystalline Au electrode.