Herein, we report a scalable, large-area synthesis of nitrogen-doped carbon nanosheets (N-AC) from bamboo biomass using KOH and urea as the activating and doping agent, respectively, for high performance asymmetric supercapacitor applications. The carbonization of the biomass bamboo at 300 °C for 2 h yields N-AC0 (char) while activation at 900°C for 2 h under inert atmosphere yields N-AC. The detailed characterization of N-AC revealed the significance of heteroatom doping for the supercapacitor application. The N-AC electrode delivered the half-cell specific capacitance of 475 Fg−1 at 1 Ag−1. The assembled asymmetric N-AC||N-AC0 supercapacitor device delivered the highest specific capacitance of 296 Fg−1 at 1 Ag−1 with specific energy of 42 Whkg−1 at specific power of 4500 Wkg−1, which are very high compared to other reported nitrogen-doped carbon materials. This enhanced performance can be attributed to the synergistic effect of larger specific surface area (of 769.714 m2g−1) and hetero-atom (N) doping, which helped in rapid charge-transfer, improved electrical conductivity and efficient electrode-electrolyte interactions. Furthermore, the N-AC asymmetric supercapacitor device works until 1.2 V with 6 M KOH as with 150% capacitance retention over 10,000 charge-discharge cycles. Thus, the strategy presented here provides new directions to synthesize low cost, green, sustainable electrodes for high energy supercapacitor applications. © 2021 Elsevier Ltd