Hierarchically porous carbon nanosheets derived from alkali metal carbonates and their capacitance in alkaline electrolytes

Abstract With the assistance of alkali metal carbonate M 2 CO 3 (M is Na and K) as a carbon source and silicon as a displacement agent, an exothermic and self-sustaining reaction to produce two-dimensional (2-D) hierarchically porous carbon nanosheets (denoted as HP-CNSs) was achieved. The combustion reaction developed a temperature in the range of 1100–1400 °C and resulted in a two-phase product consisting of HP-CNSs and alkali metal silicate (M 2 O⋅ n SiO 2 ). After dissolving the M 2 O⋅ n SiO 2 in distilled water, a black carbon powder was formed. Despite the simple synthesis process, the HP-CNSs had a BET surface area of about 178.6–860 m 2 g −1 and a pore diameter in the range 0.5–150 nm. HP-CNSs based capacitors showed a specific capacity of about 85–240 Fg −1 and good cyclic performance for over 1000 cycles.