There is disclosed a combined hydrothermal and activation process that uses hemp bast fiber as the precursor to achieve graphene-like carbon nanosheets, a carbon nanosheet comprising carbonized crystalline cellulose, a carbon nanosheet formed by carbonizing crystalline cellulose, a capacitative structure comprises interconnected carbon nanosheets of carbonized crystalline cellulose, a method of forming a nanosheet comprising carbonizing crystalline cellulose to create carbonized crystalline cellulose. The interconnected two-dimensional carbon nanosheets also contain very high levels of mesoporosity.