Fabrication of 3D Co-doped Ni-based MOF hierarchical micro-flowers as a high-performance electrode material for supercapacitors

Ni-based metal organic frameworks have attracted great interests as novel electrode materials for applications in supercapacitors, in virtue of their large specific surface area, high porosity and diverse coordination structure. Unfortunately, their specific capacitance and rate property are usually unsatisfying because of the poor conductivity of MOF materials. Herein, 3D Co-doped Ni-based MOF (Cox-Ni-MOF, x = 100n (Co/Ni) = 0.5, 2 and 5) flower-like hierarchical microspheres are prepared via a facile hydrothermal process. The introduction of Co promotes the electrochemical behaviors of Ni-MOF, especially Co2-Ni-MOF. It exhibits a prominent specific capacitance of 1300 F/g at 1 A/g along with a superb rate performance (1021 F/g at 10 A/g). Meanwhile, capacitance for Co2-Ni-MOF retains 71% of the original capacitance even after 3000 cycles. The improvement of electrochemical performance could be due to their unique structural and morphological characteristics including the 3D flower-like hierarchical microspheres structure, higher specific surface area and enhanced electrical conductivity. Moreover, a hybrid supercapacitor based on the Co2-Ni-MOF achieves an excellent energy density of 25.92 Wh/kg at a power density of 375 W/kg.