Electrodeposition of porous nanostructured gold and its electrocatalytic activity towards dopamine and nitrite oxidation

Because of its intriguing structure and properties, nano-porous gold (NPG) has drawn considerable attention in recent years in the domain of electrochemical detection [1]. The extraordinary electrocatalytic properties [2] combined with facile synthesis of free-standing layers on electrode surfaces at competitive cost and the possibility to form a hybrid with electrochemically active organic functional materials make this material an attractive choice. We report here a simple and one-step electrochemical approach without the use of an alloy or template to fabricate NPG layers on gold electrode (GE) surface and the electrocatalytic features of such platform towards the anodic oxidation of nitrite and dopamine was examined. Electrodeposition of NPG on GE was carried out by slightly modifying the DHBT method [3] employing a typical 3-electrode cell comprising GE as working electrode, Ag/AgCl as reference electrode and a platinum wire as a counter electrode in a gold chloride precursor solution in 0.5 M H2SO4 at a fixed potential of -3 V. The formation of NPG layers on GE is manifested by the sharp increase in the characteristics cathodic and anodic peaks current for gold oxidation and gold oxide reduction respectively, as observed in cyclic voltammograms (CV) shown in Fig. 1a. The increase in redox peak currents results from the highly porous nature of gold layers. The electrocatalytic activity of NPG layers towards nitrite and dopamine oxidation was studied and compared with bare GE in a similar electrochemical setup in neutral 0.1 M PBS solution (Fig. 1b and 1c). The CVs of NPG modified GE exhibited a shift as well as an increase in anodic peaks corresponding to oxidation of nitrite at 0.76 V and dopamine at 0.23 V. For both analytes, the shift of the overpotential can be attributed to the formation of electrocatalytically active defects in the NPG modified GE and the current increase can result from the larger specific surface area of NPG. It should be pointed out that the reduction peak at 0.7 V in Fig. 1b and 1c corresponds to the reduction of the gold oxide layer. Further works are in progress to investigate the electrocatalytic properties of NPG-organic functional materials based composites.