3D-Addressable Redox: Modifying Porous Carbon Electrodes with Ferrocenated 2 nm Gold Nanoparticles

Nanostructured, high-surface-area carbon electrodes have large electrochemical double-layer capacitances compared to smooth-surfaced electrodes because of their enhanced internal surface areas, e.g., several hundred m2g–1. In the present work, we demonstrate that the electrical capacitance of carbon “nanofoams”, both in commercially available forms and as prepared by the authors, can be significantly enhanced by the insertion into their pores of small Au nanoparticles (∼2 nm diameter core) to whose surfaces are bonded ferrocenyl-hexane thiolate ligands (SC6Fc) (>40 per nanoparticle). The enhanced capacitive behavior of the modified nanoporous carbon (in CH3CN or CH2Cl2 with 1.0 or 2.0 M Bu4NPF6 as the supporting electrolyte) is clearly seen in their cyclic voltammetric responses and is attributed to a combination of the ferrocene redox-capacity and the double-layer capacity of the intercalated nanoparticles. Footprint-normalized, volume-normalized, and gravimetric-normalized integral capacitances of 0.28 F cm–2, 39 F cm–3, and 66 F g–1 are realized over a 1 V potential range. We suggest this approach as a conceptual pathway to improve the science of electrochemically based energy storage systems (e.g., “supercapacitors”).