Formation of g-C₃N₄@Ni(OH)₂ Honeycomb Nanostructure and Asymmetric Supercapacitor with High Energy and Power Density

Nickel hydroxide (Ni(OH)₂) has been regarded as a potential next-generation electrode material for supercapacitor owing to its attractive high theoretical capacitance. However, practical application of Ni(OH)₂ is hindered by its lower cycling life. To overcome the inherent defects, herein we demonstrate a unique interconnected honeycomb structure of g-C₃N₄ and Ni(OH)₂ synthesized by an environmentally friendly one-step method. In this work, g-C₃N₄ has excellent chemical stability and supports a perpendicular charge-transporting direction in charge-discharge process, facilitating electron transportation along that direction. The as-prepared composite exhibits higher specific capacities (1768.7 F g^-1 at 7 A g^-1 and 2667 F g^-1 at 3 mV s^-1, respectively) compared to Ni(OH)₂ aggregations (968.9 F g^-1 at 7 A g^-1) and g-C₃N₄ (416.5 F g^-1 at 7 A g^-1), as well as better cycling performance (∼84% retentions after 4000 cycles). As asymmetric supercapacitor, g-C₃N₄@Ni(OH)₂//graphene exhibits high capacitance (51 F g^-1) and long cycle life (72% retentions after 8000 cycles). Moreover, high energy density of 43.1 Wh kg^-1 and power density of 9126 W kg^-1 has been achieved. This attractive performance reveals that g-C₃N₄@Ni(OH)₂ with honeycomb architecture could find potential application as an electrode material for high-performance supercapacitors.