Unusual Redox Behavior of Ruthenocene Confined in the Micropores of Activated Carbon

We demonstrate reversible charge/discharge in ruthenocene, RuCp2(Cp = eta(5)-C5H5), using activated carbon (AC) as a support. RuCp2 is supported in the micropores of AC as clusters consisting of multiple RuCp2 molecules via gas-phase adsorption. Upon subsequent electrochemical oxidation using an aqueous H2SO4 electrolyte, the clusters are disassembled and the RuCp2 molecules are finely dispersed in the micropores. The resulting RuCp2 has a large contact area with conductive carbon surfaces, thereby realizing rapid charge transfer at the contact interface. Consequently, rapid charge storage occurs via the reversible redox reaction of the supported RuCp2 in aqueous H2SO4 without dimerization or disproportionation reactions, which is confirmed by X-ray absorption spectroscopy. Since hybridization can produce different properties of the host and guest materials, their infinite combinations would have the possibility to yield properties far surpassing those of existing materials.