Tailorable nanostructured mercury/gold amalgam electrode arrays with varied surface areas and compositions
The mercury electrode is an attractive material for a working electrode due to its atomically smooth, self-healing surface and large potential window. Amalgams are attractive substitutes for toxic Hg in various electrochemical applications. They are typically prepared by mixing different metals with Hg, or by electrodeposition of Hg on the metals’ surfaces. These methods offer little to no control of the amalgam compositions and morphology, which is a major disadvantage of their usage. Here, we show a highly controllable method used to fabricate an array of nanostructured Au amalgam electrodes in a single step, with tailored sensitivity and composition. This method is based on the direct electrochemical co-deposition of Au and Hg from their cyano complexes, which results in branched AuxHgy structures with controlled ratios between both metals. We investigated the effects of solution composition and deposition potential on the electroactive surface area, its morphology, and the electrode potential window. The nanostructured amalgam could replace the Hg electrode for heavy metal detection with high sensitivity, due to its enhanced area and potential window similar to that of Hg. This method of in situ wet-chemistry fabrication of the Hg/Au amalgam, with tailorable nanostructure and composition, opens the door to a renaissance of Hg-based electrodes.