Nitrogen-doped carbon dots decorated ultrathin nickel hydroxide nanosheets for high-performance hybrid supercapacitor

Owing to their unique electronic properties and capability to host diverse functional groups on the surface, carbon dots (CDs) have attracted increasing attention in energy storage field. Herein, ultrathin nitrogen-doped carbon dots (NCDs) decorated nickel hydroxide (Ni(OH)₂) nanosheets were fabricated by a facile hydrothermal approach, where NCDs play an important role as a structure-directing agent in tuning the size and thickness of the Ni(OH)₂. With the merits of the battery-type faradaic behavior of Ni(OH)₂ and high electronic properties of NCDs, the achieved Ni(OH)₂/NCDs ultrathin nanosheets show a specific capacitance of about 1711.2 F g^-1 at a current density of 1 A g^-1, which istwice morethan that of pristine Ni(OH)₂. A hybrid supercapacitor device was constructed using Ni(OH)₂/NCDs ultrathin nanosheets as the positive electrode and three-dimensional graphene (3DGE) as the negative electrode, respectively, which presents high energy density of 23.8-34.6 Wh kg^-1 at power density of 700-7000 W kg^-1. The enhanced electrochemical properties of Ni(OH)₂/NCDs nanocomposite hold potential for future high-performance energy storage applications.