Graphene oxide template-directed synthesis of porous carbon nanosheets from expired wheat flour for high-performance supercapacitorsElectronic supplementary information (ESI) available. See DOI: 10.1039/c8nj01587b

Two-dimensional (2D) N,S co-doped porous carbon nanosheets are prepared in the presence of graphene oxide (GO) from expired wheat flour. It is found that GO can effectively direct the morphologies of the activated products, resulting in unique 2D structures. The as-obtained 2D N,S co-doped porous carbon nanosheets as electrodes for supercapacitors exhibit a high specific capacitance of 291 F g −1 at a current density of 0.5 A g −1 and good rate capability with a capacitance retention of 70% at a high current density of 30 A g −1 . The 2D N,S co-doped porous carbon nanosheet electrodes also exhibit good cycling performance, possessing a high capacitance retention of over 93% after 5000 charge-discharge cycles at a current density of 5 A g −1 . Experimental and theoretical results reveal that the synergistic effect of the N and S species can improve the electrochemical performance. The peculiar 2D structural characteristics featuring a short ion transport distance and abundant porous channels also can increase the specific capacitance. 2D N,S co-doped porous carbon nanosheets are prepared in the presence of GO from expired wheat flour.