Electrochemical capacitance of mesoporous gold

The surfaces of nanoscale gold particles and components are oxide-free under normal ambient conditions. This unusual attribute permits the exploration of microstructures and functionalities that would not be feasible for less noble metals. Here we consider the electrochemical properties of mesoporous gold sponges, prepared by de-alloying an AuAl2 precursor. The sponges have a high specific surface area, with an average pore diameter of 12 nm, but are prone to sinter. They may be prepared in bulk, or, more usefully, as coatings. Their electrochemical capacitance divided by their nominal surface area is high and, at a cell voltage of 0.6 V, reaches 100 mF/cm(2) for bulk samples and 2 mF/cm(2) for coatings. This is up to a thousand times greater than the 50 to 100 mu F/cm(2) exhibited by a planar gold surface.