Facile growth of hexagonal NiO nanoplatelet arrays assembled by mesoporous nanosheets on Ni foam towards high-performance electrochemical capacitors

Highlights: ► Hexagonal nickel oxide nanoplatelet arrays free-standing on Ni foam. ► NiO nanoplatelets were assembled by ultrathin mesoporous nanosheets. ► Binder-free NiO arrays deliver high specific capacitance at high rates. ► Self-supported NiO arrays electrode kept excellent cycling stability. - Abstract: In the work, we develop a novel two-step strategy to synthesize self-supported hexagonal nickel oxide nanoplatelet arrays on Ni foam: precipitating hydroxides followed by calcinating process. These nanoplatelets are composed of a multilayer of ultrathin mesoporous NiO nanosheets. The unique Ni foam-supported mesoporous NiO nanoplatelet arrays electrode promises fast ion and electron transport, large electroactive surface area, and excellent structural stability. As a result, superior pseudocapacitive performance is achieved with large specific capacitance in the range of 1124–864 F g−1 and excellent cycling stability up to 5000 cycles, suggesting their promising application for electrochemical capacitors.