Molybdenum-doped CuO nanosheets on Ni foams with extraordinary specific capacitance for advanced hybrid supercapacitors

Copper oxide (CuO) electrodes have outstanding potentials for supercapacitors in virtue of their low cost, environment friendly, especially, and the high theoretical specific capacitance (1800 F g−1). However, their poor electronic conductivity restricts the practical application. Doping appropriate transitional metal ions into host materials is an effective method to modulate the electronic structure and improve the conductivity, furthermore, enhancing the energy storage capacity. Herein, Mo-doped CuO nanosheets on Ni foams were obtained by combining a simple hydrothermal process and calcination treatment. Different doping concentrations of Mo were discussed, and the as-prepared 3 at.% Mo-doped CuO (Mo-CuO-2) exhibited the best electrical conductivity and the highest specific capacitance of 1392 F g−1 at 2 A g−1. In addition, an asymmetric supercapacitor device was assembled using Mo-CuO-2 and activated carbon as a positive electrode and a negative electrode, which exhibited a remarkable energy density of 36 Wh kg−1 at 810 W kg−1 and an excellent cycle life with 81% capacitance retention for over 5000 cycles. More significantly, Mo-CuO-2 is a promising material candidate for practical energy storage applications.