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

Abstract

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.