A comparative study on the supercapacitive properties of MnMoO₄/MWCNT and MnMoO₄ was conducted to assemble a high-performance supercapacitor device for future energy technologies.

The cycling performance of supercapacitors sometimes becomes limited when electrode materials slough off during frequent charge–discharge cycles, due to weak bonding between the active material and the current collector. In this work, a flexible graphite foil substrate was successfully used as the current collector for supercapacitor electrodes. Graphite foil substrates were treated in different ways with different acid concentrations and temperatures before being coated with an active material (NiMoO₄/nanographite). The electrode treated with HNO₃(65%) and H₂SO₄(95%) in a 1:1 ratio at 24°C gave better electrochemical performance than did electrodes treated in other ways. This electrode had capacitances of 441 and 184 Fg^–1at current densities of 0.5 and 10 Ag^-1, respectively, with a good rate capability over the current densities of the other treated electrodes. SEM observation of the electrodes revealed that NiMoO₄with a morphology of nanorods 100–120 nm long was properly accommodated on the graphite surface during the charge–discharge process. It also showed that treatment with high-concentration acid created an appropriately porous and rough surface on the graphite, enhancing the adhesion of NiMoO₄/nanographite and boosting the electrochemical performance.

In this study, we show the synthesis of reduced graphene oxide/hydroxyapatite (rGO/HA) composites using a hydrothermal autoclave with argon-15% hydrogen gas injection. This both increases the hydrothermal pressure and uses hydrogen as a reductive agent in the process. The synthesized powders were then consolidated with spark plasma sintering method. The analysis of the consolidated samples included Vickers Indentation technique and cell viability. The results showed that injected gases in the autoclave produced powders with a higher crystallinity compared to synthesis without the gases. Also, hydrogen gas led to increased reduction of GO. The microscopic analysis confirmed existing graphene sheets with folding and wrinkling in the powders and indicated that various preferential directions played a role in the growth of hydroxyapatite crystals. The results showed that in general, graphene sheets increased the mechanical properties of HA. In the samples synthesized with injected gases, this increase was more significant. Interface analysis results indicate that reduced graphene oxide (rGO)/HA interface is likely coherent. These nanocomposites were biocompatible and showed some hydrophobicity compared to pure HA.

This paper presents research on the synergistic effects of nickel molybdate and reduced graphene oxide as a nanocomposite for further development of energy storage systems. An enhancement in the electrochemical performance of supercapacitor electrodes occurs by synthesizing highly porous structures and achieving more surface area. In this work, a chemical precipitation technique was used to synthesize the NiMoO₄/3D-rGO nanocomposite in a starch media. Starch was used to develop the porosities of the nanostructure. A temperature of 350 °C was applied to transform graphene oxide sheets to reduced graphene oxide and remove the starch to obtain the NiMoO₄/3D-rGO nanocomposite with porous structure. The X-ray diffraction pattern of the NiMoO₄ nano particles indicated a monoclinic structure. Also, the scanning electron microscope observation showed that the NiMoO₄ NPs were dispersed across the rGO sheets. The electrochemical results of the NiMoO₄/3D-rGO electrode revealed that the incorporation of rGO sheets with NiMoO₄ NPs increased the capacity of the nanocomposite. Therefore, a significant increase in the specific capacity of the electrode was observed with the NiMoO₄/3D-rGO nanocomposite (450 Cg⁻¹ or 900 Fg⁻¹) when compared with bare NiMoO₄ nanoparticles (350 Cg⁻¹ or 700 Fg⁻¹) at the current density of 1 A g⁻¹. Our findings show that the incorporation of rGO and NiMoO₄ NP redox reactions with a porous structure can benefit the future development of supercapacitors.