Porous carbons are considered as promising electrode materials for supercapacitors due to their excellent microstructural properties. Synthesizing porous carbon from a bio-waste material has received significant importance due to their natural abundance and low-cost. Here we report the synthesis of porous carbon from a bio-waste, sweet corn husk precursor. Influence of morphology and crystallinity of pre-activated carbon on the microstructural properties of the resultant activated carbons are studied. The chemical activation method results in carbon with turbostratic nature, high specific surface area (1370 m2 g-1) with large mesoporous volume fraction and 2D layered-like morphology. Similar specific surface area is observed for samples prepared with the variation in the amount of activating agent due to higher pre-carbonization temperature. The resultant activated carbon (ASCH-1:1) shows a specific capacitance of 127 F g−1 with low energy density (4.4 Wh kg−1) in 6 M KOH electrolyte. A high energy density of 20 Wh kg−1 is obtained in 1 M TEABF4/AN electrolyte with a high specific capacitance of 80 F g−1 at 1 A g−1. It shows good cyclic stability by retaining 90% of initial capacitance after 5000 cycles at 2 A g−1. Our results demonstrate that activated carbons reported here are promising materials for high operating voltage supercapacitors. © 2020 Elsevier B.V.