MOF-derived NiO/Ni architecture encapsulated into N-doped carbon nanotubes for advanced asymmetric supercapacitors

Metal-organic frameworks (MOFs) are promising precursors for the construction of various functional materials for high-performance electrochemical energy storage devices. Herein, we introduce a novel strategy for the synthesis of NiO/Ni architecture encapsulated into N-doped carbon nanotubes (NiO/Ni/NCNTs) through a simple two-step method. First, 3D columnar nickel-based MOFs (Ni-MOFs) were synthesized via a solution reaction. Then the Ni2+ in Ni-MOFs was partly reduced to Ni to catalyze the formation of NCNTs through an inert atmosphere calcination treatment. These NiO/Ni/NCNTs nano-composites can not only provide more reactive sites for electrochemical reactions, but also provide conductive channels for electron transport. They exhibit a specific capacitance of 777.5 F g(-1) at 1 A g(-1) in a three-electrode system. An asymmetric supercapacitor is assembled using NiO/Ni/NCNTs as the anode electrode and porous carbon as the cathode electrode, which has demonstrated an energy density of 33.89 W h kg(-1) at a power density of 800 W kg(-1) and excellent cycling performance (capacitance retention is nearly 90% at a current density of 1 A g(-1) after 40 000 cycles). The NiO/Ni/NCNTs will become a great potential electrode material for supercapacitors.