Gold nanoparticle-assisted electroreduction of oxygen

The electrocatalytic effect of nano-sized gold (Au) particles towards reduction of oxygen has been investigated in neutral aqueous media. The self-assemblies of -NH2 terminated short chain disulfide, cystamine (CYST) and aromatic dithiol, 1,4-benzenedimethanethiol (BDMT) were utilized for anchoring nanostructured citrate-stabilized Au particles. The cyclic voltammetric peak for the reduction of oxygen at cystamine monolayer-modified Au electrode (CYST-Au) is rather broad and it appears at around −0.5 V vs. Ag/AgCl, which is 250 mV more negative than that at the bare Au electrode. The BDMT monolayer-modified Au electrode (BDMT-Au) does not show any characteristic peak for the reduction of oxygen, as the monolayer completely blocks the permeation of oxygen to the electrode surface. Interestingly, reduction of oxygen at less negative potential was observed when Au nanoparticles were anchored on these thiol monolayer-modified electrodes. The Au nanoparticle on the electrode surface efficiently catalyzes the reduction of oxygen to hydrogen peroxide. Compared to the bare polycrystalline Au electrode, a significant increase in the cathodic peak current and a 130-mV positive shift in the cathodic peak potential have been observed at the Au nanoparticle-anchored electrodes.