Oxygen reduction at electrochemically deposited crystallographically oriented Au(100)-like gold nanoparticles

Abstract

A novel electrocatalyst for oxygen reduction has been proposed based on the electrodeposition of Au nanoparticles onto glassy carbon (nano Au/GC) electrodes in the presence of some additives, typically cysteine. Steady-state hydrodynamic voltammetric studies for the oxygen reduction reaction (ORR), in O₂-saturated 0.5 M KOH solution, at the thus-prepared nano Au/GC disk electrode have revealed an increasing disk current (I_D) (current maxima) up to −0.5 V vs. Ag/AgCl/KCl(sat) compared to the other nano Au/GC disk electrodes prepared under different conditions. This high value (maxima) of I_D is associated with a low value of the corresponding Pt ring current (I_R) and in turn a higher number of electrons (n) is exchanged at the disk electrode during the ORR in alkaline medium in this potential window. At more cathodic potentials, this disk current maxima vanished and the nano Au/GC disk current showed a minimal value associated with a significant increase in I_R. This resembles the behaviour of the ORR at single crystalline Au(1 0 0) disk electrodes in the similar media. Thus, a 4-electron reduction of oxygen to water can be accomplished at a reasonably low cathodic overpotential.