Observation of High Capacitance from Molecular Gd@C₈₂ in Aqueous Electrolyte Derived from Energy‐Level Matching with Proton

Abstract

Fullerenes with very high specific surface area have never been used as an electrode material in advanced energy storage, which is due to their incompatible electronic structures hindering any large Faradaic capacitance. Here, molecular endohedral metallofullerene of Gd@C₈₂ for the first time as a novel active material is observed a capacitance of 186 F g⁻¹ and good rate capability in aqueous electrolyte, exceeding other fullerenes (<10 F g⁻¹) and commercial activated carbon (YP‐50 ≈155 F g⁻¹). This less symmetric C₈₂ filled by gadolinium achieves apposite energy levels absorbing protons to greatly improve its capacitance, which is confirmed by the results of first‐principals calculations. Gibbs free energy analyses further demonstrate that the Gd@C₈₂ is spontaneous to accept electrons coupled with protons. This research would open up a path for fullerenes as a new‐type electrode material.