Alkaline-carbonate-templated carbon: effect of template nature on morphology, oxygen species and supercapacitor performances

Abstract Nanocasting techniques are widely adopted for the fabrication of nanocarbons. However, there is little research on the effect of template nature on the physicochemical properties and performances of the nanocarbons. Herein, we investigated how the morphology, oxygen species as well as supercapacitor performance of the derived nanocarbons were governed by the morphology, surface basicity and thermal stability of MgCO3, CaCO3 and BaCO3 when the alkaline metal carbonates were used as templates. Using MgCO3 as catalytic template, the MgC973 produced after carbonization at 973K has ultrathin nanosheet morphology (∼20 nm), large specific surface area (952 m2/g), and superior supercapacitor performances, showing high capacitance of 421 F/g@1.0 A/g (maintaining 306 F/g@20 A/g), and large energy density of 31.1 Wh/kg@1000 W/kg. The superiority can be ascribed to the ultrathin morphology and thermal instability of the MgCO3 template, which upon decomposition generates CO2 and in situ activates the carbon skeleton. Moreover, the surface alkalinity of templates is conducive to the retention of electrochemically active oxygen, and BaC973 is with oxygen content (9.1 atom%) higher than MgC973 (7.9 atom%) and CaC973 (8.8 atom%). The present work provides insightful ideas for the synthesis of unique carbon materials with specific functionalities through the selection of suitable templates.