Facile synthesis of nanostructured gold for microsystems by the combination of electrodeposition and dealloying

For the successful exploitation of microelectrochemical systems, e. g., micro-sensors and micro-fuel cells, synthesis of porous electrodes on tiny current collectors is of great importance. Here, a facile electrochemical method based on the combination of electrodeposition and dealloying is proposed. AuCu alloy was deposited in a sulfuric acid solution containing cupric ions and tetrachloroaurate ions, and then was dealloyed in the same solution just by applying a more positive potential. The synthesized thin film was 100 at% polycrystalline Au and consisted of spongelike nanostructures with 50-100 nm thick ligaments and wider pores. The crystal lattice of the ligament surface was found to be contracted on the basis of the results of X-ray photoelectron spectroscopy and electron diffractometry. This is probably due to the residual stress caused by dealloying. The electrochemical measurements revealed that the surface area was ca. 25 times larger than its geometrical area (thickness: 780 nm), and that the surface contained well-ordered large Au(111) terraces. Finally, feasibility of the application of this synthesis to microsystems was proved by using microelectrode arrays. Thus, this method is promising for preparing Au electrodes for microelectrochemical devices.