Hierarchical electrodes assembled by alternate NiCo hydroxide nanowires arrays and conductive interlayers with enhanced properties for electrochemical supercapacitors.

Abstract Transition metal oxides/hydroxides materials attract much attention in the field of energy storage materials because of their high theoretical specific capacity and low cost. However, it is normally difficult to improve the capacitance of the electrode by simply increasing the mass loading or thickness of the electrode. To raise the utilizing efficiency of the active material, hierarchical integrated electrodes assembled by NiCo hydroxide nanowires arrays and reduced graphene oxide interlayers are well designed and synthesized. The surface morphology and inner structure of the hierarchical electrode are characterized by SEM. The electrochemical performances of the electrodes are evaluated by three-electrode and two-electrode system in 2 M KOH respectively. Assisted with two reduced graphene oxide interlayers, NiCo hydroxide nanowires arrays exhibit a specific capacity of 2.41 C cm−2 at 1 mA cm−2. Even at a high current density of 50 mA cm−2, nearly 47% of the capacity could still remain. The results show that, the multi-level nanowires arrays structure provides multi-dimensional transmission path for ions and electrons, and achieved higher specific capacities and rate properties. Graphical abstract Image 1 Highlights • A multi-step hydrothermal method is proposed to prepare hierarchical electrode. • Combination of multi-layer NiCo-H NWAs and rGO interlayers are required. • The hierarchical structure provides multi-dimensional transmission path for ions and electrons. [ABSTRACT FROM AUTHOR]