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_?F/cm 2 exhibited by a planar gold surface.