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-C 3 N 4 /C (Ni(OH) 2 –g–C 3 N 4 /C) are designed by biological template induction and a hydrothermal method. Ni(OH) 2 –g–C 3 N 4 /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-C 3 N 4 and can also improve the overall conductivity of the composite. Compared to Ni(OH) 2 (522 F g −1 ), g-C 3 N 4 /C (76.2 F g −1 ), and g-C 3 N 4 (16 F g −1 ), the Ni(OH) 2 –g–C 3 N 4 /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.