RGO-loaded double phase Mo-doped NiS for enhanced battery-type energy storage in hybrid supercapacitors

The Mo-doped NiS/rGO composite was obtained by vulcanization of NiMoO 4 and morphology adjustment by GO. A nanosheet-like structure was demonstrated in the composite, which was assembled by double-phase Mo-doped NiS (Mo-NiS) nanodots loading on reduced graphene oxide (rGO) nanosheets. The doping of Mo and the resultant synergistic effect between Mo and Ni can offer the bimetallic sulfide of Mo-NiS with higher capacity output and enhanced cycle stability. The surface oxygen-containing functional groups of GO provide abundant nucleation centers for the uniform loading of Mo-NiS nanodot during synthesis, and the resultant rGO sheets in the final composite ensures continuous electron transport and promoted ionic exchange for Mo-NiS. Besides, the Mo-NiS nanoparticles loaded on the surface of rGO can also inhibit its stacking and form a highly integrated composite structure. The synergistic effect of Mo-doping, double-phase NiS and conductive rGO substrates attributed to the high specific capacity output (1664.7 C g −1 at 1 A g −1 ), long cycle life and excellent rate performance in the final composite. The Mo-NiS/rGO composite was also applied as a battery-type electrode in asymmetric supercapacitors (ASCs), which showed acceptable performance for potential practicability, including attractable energy densities and power densities, as well as impressive cyclic ability with large capacity retention of 90.3% in 7000 cycles. Graphical Abstract