Nickel cobalt sulfide (NiCo2S4) nanosheets were successfully grown on porous graphitic carbon nitride (g-C3N4) nanosheets (NiCo2S4 NSs/P-g-C3N4), which was employed as supercapacitor electrode materials. The NiCo2S4 NSs/P-g-C3N4 electrode shows specific capacity as high as 506 C g(-1) at a current density of 1 A g(-1), outstanding rate capability and cycling stability (almost no attenuation after 1500 cycles at 3 A g(-1)), which can be attributed to the unique 'sheets on sheets' architectures providing short ion diffusion pathways, and good ion permeability. NiCo2S4 NSs/P-g-C3N4 was combined with activated carbon (AC) to construct NiCo2S4 NSs/P-g-C3N4//AC asymmetric supercapacitor (ASC), which offers a specific energy of 16.7 W h kg(-1) at a specific power of 200 W kg(-1), and high cycling performance (about 99% retention after 5000 continuous cycles). An ASC device could power a mini-fan for about 60 s, demonstrating that NiCo2S4 NSs/P-g-C3N4 is a potential electrode material for energy storage. (C) 2017 Elsevier Ltd. All rights reserved.