Comparison of α-NiMoO4 nanorods and hierarchical α-NiMoO4@δ-MnO2 core-shell hybrid nanorod/nanosheet aligned on Ni foam for supercapacitors

Three-dimensional (3D) hierarchical α-NiMoO4@δ-MnO2 core-shell hybrid nanorods/nanosheets are fabricated directly on Ni foam via a two-step approach which involves hydrothermal and one-pot chelation-mediated aqueous processes. The α-NiMoO4 nanorods are full covered by ultrathin δ-MnO2 nanosheets and the morphological evolution process of α-NiMoO4@δ-MnO2 electrode has been investigated by scanning electron microscopy (SEM) at different time intervals. When this hybrid, along with porous Ni foam, is employed as binder-free electrode for supercapacitors, exhibiting high capacitance of 1136 F g−1 at a current density of 2 A g−1 and super-long cycling life with 101.9% retention rate after 5000 cyclic voltammetry cycles, which are much better than the single α-NiMoO4 nanorod electrode. Moreover, according to the electrochemical impedance spectroscopy (EIS) analysis, it is found that the equivalent series resistance (Rs) and charge transfer resistance (Rct) of the hybrid electrode are 0.22 Ω and 4.03 Ω, respectively. In view of the outstanding electrochemical performance and the cost-effective fabrication process, this unique integrated nanoarchitecture would hold great promise for electrochemical energy storage.