Oxygen reduction at electrochemically deposited crystallographically oriented Au(1 0 0)-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 O 2-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.