Porous Graphitic Carbon Nanosheets Derived from Cornstalk Biomass for Advanced Supercapacitors

Porous graphitic carbon nanosheets (PGCS) are synthesized by an in situ self‐generating template strategy based on the carburized effect of iron with cornstalks. Cornstalks firstly coordinate with [Fe(CN)6]4− ions to form the cornstalk–[Fe(CN)6]4− precursor. After carbonization and removal of the catalyst, PGCS are obtained. Series experiments indicate that PGCS can only be formed when using an iron‐based catalyst that can generate a carburized phase during the pyrolytic process. The unique structures of PGCS exhibit excellent capacitive performance. The PGCS‐1‐1100 sample (synthesized from 0.1 M [Fe(CN)6]4− with a carbonization temperature of 1100 °C), which shows excellent electrochemical capacitance (up to 213 F g−1 at 1 A g−1), cycling stability, and rate performance in 6 M KOH electrolyte. In the two‐electrode symmetric supercapacitors, the maximum energy densities that can be achieved are as high as 9.4 and 61.3 Wh kg−1 in aqueous and organic electrolytes, respectively. Moreover, high energy densities of 8.3 and 40.6 Wh kg−1 are achieved at the high power density of 10.5 kW kg−1 in aqueous and organic electrolytes, respectively. This strategy holds great promise for preparing PGCS from natural resources, including cornstalks, as advanced electrodes in supercapacitors. Fields of gold? Porous graphitic carbon nanosheets (PGCS) have been synthesized by a self‐generating template strategy based on the carburized effect of iron with cornstalks. The synthesized PGCS exhibit excellent capacitive performance owing to their unique porous nanostructures and graphitic carbon nanosheets, which can facilitate ion and electron transport, respectively.