Synthesis of NiMoO4/3D-rGO Nanocomposite in Alkaline Environments for Supercapacitor Electrodes

Abstract

Although Graphene oxide (GO)-based materials is known as a favorable candidate for supercapacitors, its conductivity needs to be increased. Therefore, this study aimed to investigate the performance of GO-based supercapicitor with new methods. In this work, an ammonia solution has been used to remove the oxygen functional groups of GO. In addition, a facile precipitation method was performed to synthesis a NiMoO4/3D-rGO electrode with purpose of using synergistic effects of rGO conductivity properties as well as NiMoO4 pseudocapacitive behavior. The phase structure, chemical bands and morphology of the synthesized powders were investigated by X-ray diffraction (XRD), Raman spectroscopy, and field emission secondary electron microscopy (FE-SEM). The electrochemical results showed that the NiMoO4/3D-rGO(II) electrode, where ammonia has been used during the synthesis, has a capacitive performance of 932 Fg−1. This is higher capacitance than NiMoO4/3D-rGO(I) without using ammonia. Furthermore, the NiMoO4/3D-rGO(II) electrode exhibited a power density of up to 17.5 kW kg−1 and an energy density of 32.36 Wh kg−1. These results showed that ammonia addition has increased the conductivity of rGO sheets, and thus it can be suggested as a new technique to improve the capacitance.

Treatment of NiMoO4/nanographite nanocomposite electrodes using flexible graphite substrate for aqueous hybrid supercapacitors

“…This confirms the Faradaic behavior of NiMoO 4 nanorods. According to the literature [ 4 , 27 , 28 ], molybdenum is not involved in the redox reactions, but rather enhances the electrical conductivity of nickel molybdate. Moreover, the CV curves of the electrodes with pre-treated graphite foil substrate indicate a larger enclosed area than that of the NMOG-G electrode with pristine G substrate.…”

“…Actually, at higher current densities, intercalation of ions into the inner active sites becomes more difficult, reducing the specific capacitance. Moreover, the mechanical expansion of NiMoO 4 during the ion intercalation/deintercalation process can cause some NiMoO 4 to slough off, lowering the capacitance [ 26 , 27 , 30 ]. At a current density of 0.5 Ag −1 , the NMOG-GHC60 and NMOG-GHC24 electrodes display specific capacitances of 454.5 and 441 Fg −1 , respectively, higher than those of the NMOG-GLC24 and NMOG-G electrodes, with specific capacitances of 385 and 241 Fg −1 , respectively.…”

Synthesis of a NiMoO4/3D-rGO Nanocomposite via Starch Medium Precipitation Method for Supercapacitor Performance

“…Mo is not involved in redox reactions. This element, with a high conductivity, can increase the whole capacity of the cell [26,44]. As shown in Figure 6b, the CV curves of the NiMoO 4 /3D-rGO electrode, similar to the NiMoO 4 electrode (Figure 6a), at low scan rates displayed two redox peaks related to NiMoO 4 faradaic reactions (Ni 2+ /Ni 3+ ).…”

“…This is related to the electrode internal resistance, which limits the charge transfer at high scan rates. At lower scan rates, a pair of redox peaks could be seen in each CV curve, indicating the Faradic reaction of Ni(II)/Ni(III) [26,42] due to the reversible phase change between Ni(OH) 2 and NiOOH (0.44 V and 0.18 V) [43]. By scanning the electrode, the OH − ions will be dispersed on the surface of Ni(OH) 2 layer and form the NiOOH phase, as shown in Equation 6:…”

“…where Q (Cg −1 ) is the charge stored [7], I (A) refers to the discharge current, ∆t (s) is attributed to the discharge time, and m (g) is related to the mass loading of the active material on the current collector [26,27].…”