2D Hierarchical NiMoO₄ Nanosheets/Activated Carbon Nanocomposites for High Performance Supercapacitors: The Effect of Nickel to Molybdenum Ratios

Abstract

Supercapacitors have the potential to be used in a variety of fields, including electric vehicles, and a lot of research is focused on unique electrode materials to enhance capacitance and stability. Herein, we prepared nickel molybdate/activated carbon (AC) nanocomposites using a facile impregnation method that preserved the carbon surface area. In order to study how the nickel-to-molybdenum ratio affects the efficiency of the electrode, different ratios between Ni-Mo were prepared and tested as supercapacitor electrodes, namely in the following ratios: 1:1, 1:2, 1:3, 1:4, and 1:5. X-ray diffraction, X-ray photoelectron spectroscopy, FESEM, HRTEM, and BET devices were extensively used to analyze the structure of the nanocomposites. The structure of the prepared nickel molybdates was discovered to be 2D hierarchical nanosheets, which functionalized the carbon surface. Among all of the electrodes, the best molar ratio between Ni-Mo was found to be 1:3 NiMo3/AC reaching (541 F·g−1) of specific capacitance at a current density of 1 A·g−1, and 67 W·h·Kg−1 of energy density at a power density of 487 W·Kg−1. Furthermore, after 4000 repetitive cycles at a large current density of 4 A·g−1, an amazing capacitance stability of 97.7% was maintained. This remarkable electrochemical activity for NiMo3/AC could be credited towards its 2D hierarchical structure, which has a huge surface area of 1703 m2·g−1, high pore volume of 0.925 cm3·g−1, and large particle size distribution.

Keywords

• activated carbon
• nickel molybdate
• hierarchical structure
• nanocomposite
• supercapacitors