Hierarchical flower-like architecture of nickel phosphide anchored with nitrogen-doped carbon quantum dots and cobalt oxide for advanced hybrid supercapacitors.

The exploitation of hybrid supercapacitors with excellent electrochemical properties is of great significance for energy storage systems. Herein, a three-dimensional hierarchical flower-like architecture of nickel phosphide (NiP) decorated with nitrogen-doped carbon quantum dots (N-CQDs) and cobalt oxide (CoO) is constructed by an effective two-step hydrothermal strategy followed by in situ phosphorization process. Introducing N-CQDs with superior electrochemical characteristics can not only induce the formation of N-CQDs deposited nickel hydroxide (Ni(OH)) flower-like architecture but also significantly enhance the electrochemical features of Ni(OH) nanosheets. After combination with CoO nanoparticles and phosphorization treatment, an advanced cathode of NiP/CoO/N-CQDs with enriched surface phosphate ions is obtained, which possesses an ultra-high capacity of 1044 C g (2088 F g) at 1 A g with a splendid rate capacity of 876 C g (1752 F g) at 20 A g. Moreover, a device assembled by NiP/CoO/N-CQDs hierarchical flower-like architecture and p-phenylenediamine functionalized reduced graphene oxide (PPD/rGO) nanosheets depicts a commendable energy density of 53.5 Wh kg at 772.9 W kg. This work provides a novel hierarchical multi-component electrode material with decent electrochemical capacities for hybrid supercapacitors, which has a broad prospect in energy storage devices.