Furthermore, the same symmetric cell demonstrated the reasonable energy density of 10.9 Wh Kg -1 along with 98.2% of retention of capacitance after 10000 cycles at 5 A g -1 . The availability of interconnected hollow particles along with appreciable nitrogen content are believed to be HCl solution . The usage of MgO as a hard template to generate porous carbon fibers with N-doping is owing to its variety of fascinating aspects such as less cost and easy removal that could evade the usage of complicated hard templates, harsh reagents and difficult activations.