Enhanced Pseudocapacitive Performance of Electrochemically Deposited α-NiMoO4 Nanoworms on 3D Reduced Graphene Oxide Scaffold

The development of an efficient method for fabricating binder-free electrodes consisting of a three-dimensional (3D) carbon material as the conductive agent and a metal oxide as the active material is of interest. Here, an efficient two-step strategy was proposed for the fabrication of an rGO-supprted NiMoO4 electrode as a pseudocapacitive electrode. In the first step, rGO nanosheets were deposited on nickel foam by a hydrothermal process to obtain a 3D porous scaffold. In the next step, worm-like nickel molybdate nanoparticles were grown on the rGO framework by a cathodic galvanostatic electrodeposition and subsequent calcination. The structure and morphology of the electrodes were characterized by x-ray diffraction and field-emission scanning electron microscopy. The results demonstrated that NiMoO4 nanoworms were uniformly deposited on the surface of the rGO nanosheets, forming a 3D porous structure. Electrochemical characteristics of the electrodes were examined by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. According to the unique 3D structure, the hybrid electrode exhibited superior charge storage performance including a high specific capacitance of 1243 F g-1 at 1 A g-1, excellent cycling stability (92.3% capacitance retention after 2000 cycles), and good rate capability (68.1% capacitance retention with a 10-fold increase in the current rate).