Xu et al. reported the synthesis of sulfur, and nitrogen dual-doping porous carbon materials produced by carbonizing the shells of broad beans by a chemical activation method for use as the electrode materials for energy storage devices . The shells of broad beans were carbonized in an inert gas (CSB), and then further chemically activated using KOH at 650 ˚C for 1 h under nitrogen to obtain the N, S-dual doped biomass derived porous carbon (ASCB). The XPS analysis of CSB showed nitrogen, and sulfur heteroatoms with 2.2, and 0.97 at. %, while ASCB displayed 2.0, and 0.94 at. %, respectively. The BET studies showed the maximum specific surface of 655.4 m 2 g -1 , and a total pore volume of 0.38 cm 3 g -1 for ASCB sample. The electrochemical measurements were performed in a three-electrode system using 6 M KOH aqueous solution. The ASCB electrode exhibited the specific capacitance of 202 F