shows the voltammograms of the gold (Au), GC/AuNPs/E and GC/AuNPs/C electrodes at 0.1 V s−1.
The modified electrodes with AuNPs contain two anodic peaks at 0.93 and 1.12 V while the Au electrode at 1.24 and 1.46 V, which are associated with the formation of gold oxides.
The cathodic peak was shifted tomore negative potentials with the decrease in size of nanoparticles from 0.80 V (Au) to 0.70 V (GC/AuNP/E) and 0.68 V GC/AuNPs/C corresponded to the reduction of the formed gold oxides [39–42].
On the other hand, the oxygen evolution starts at less positive potentials to the electrodes containing AuNPs than gold electrode and the residual current was higher in the electrodes with nanoparticles, these changes may be due to the amount of exposedcarbon and gold as well as aggregation on the electrode surface