Design of Hierarchically Porous Carbons with Interlinked Hydrophilic and Hydrophobic Surface and Their Capacitive Behavior

In this contribution, we report a general surface engineering strategy to transform nonpolar nanocarbons ( e.g., carbon nanotube and graphene) into amphiphilic nanocarbons with unique ultrahydrophilic@ultrahydrophobic surface configuration and hierarchical structure by grafting a thin layer of metal–organic frameworks followed by pyrolysis and leaching. The outer ultrahydrophilic carbon layer features rich surface heterogeneity (B-/N-doping both up to ca. 10 at. %) and high density of microporosity, while the inner nonpolar CNT or graphene provides a high electronic conductivity. The unique bipolar surface and high heterogeneity as well as highly accessible hierarchical structures render this family of nanocarbons capable of a high surface efficiency under both aqueous and organic conditions, as it is reflected in the behavior of the electrodes for supercapacitors by comparing a wide range of highly porous nonpolar carbons. The bipolar hierarchical carbons’ efficiency in terms of areal capacitance and energy density are 3–6 times and 2–3 times higher than that of typical benchmark materials ( e.g., commercially popular YP-50F carbons, CNT, and graphene etc. ). More importantly, the study of this series of model carbon materials may help researchers to understand in-depth how carbon surface chemistry with a high density of doping sites influences the wetting, transport, and electrosorption behavior of charged ions in aqueous and organic conditions.