Synthesis of Ni(OH)2-g-C3N4/C Composite by Biological Template for Asymmetric Supercapacitor

Nickel hydroxide (Ni(OH)(2)) is recognized as a promising material for electrodes in supercapacitors owing to its exceptional theoretical specific capacitance. However, Ni(OH)(2) has several drawbacks, including a short cycle life, susceptibility to volume expansion, and poor electrical conductivity. In this work, Ni(OH)(2) nanosheets anchored on layered g-C3N4/C (Ni(OH)(2)-g-C3N4/C) are designed by biological template induction and a hydrothermal method. Ni(OH)(2)-g-C3N4/C has unique petal-like structures, which can provide a vertical charge transport channel to increase reaction potential of the material during the charge-discharge process. The introduction of biomass carbon can solve the problem of the bulk phase accumulation of g-C3N4 and can also improve the overall conductivity of the composite. Compared to Ni(OH)(2) (522 F g(-1)), g-C3N4/C (76.2 F g(-1)), and g-C3N4 (16 F g(-1)), the Ni(OH)(2)-g-C3N4/C-0.75 (NGC-0.75) composite exhibits the highest specific capacitance of 1034 F g(-1) at 1 A g(-1). Furthermore, after 5000 cycles at 5 A g(-1), the capacitance of the material is maintained at 85.97%. Meanwhile, the asymmetric supercapacitor based on the NGC-0.75 shows a high energy density of 18.29 Wh kg(-1) at the power density of 400.02 W kg(-1) with excellent cyclic stability of 127.45% over 10 000 cycles.