Graphene oxide (GO) acts as an insulator but when reduced to reduced graphene oxide (RGO), it has high heat storage capacity. This can result in lowering the phase change temperature when embedded in a material such as expanded polystyrene (EPS), thus making it a good heat-resistance material. In this study, the thermal and the mechanical effects of GO and RGOs over EPS were analysed. GO was synthesized using modified Hummer’s method, while the reduction process was taken through different routes using three different reductants: hydrazine (RGO-HZ), ascorbic acid (RGO-AA) and the extract of Amaranthus hybridus (RGO-AH). The same content of graphite and its derivatives were separately and chemically bonded together with EPS forming composites (i.e., graphite composite, GO composite, RGO-HZ composite, RGO-AA composite and RGO-AH composite) and cast on a mould at room temperature to form a dog-bone shape. Fourier transform infrared spectroscopy, differential thermal analysis, scanning electron microscopy and mechanical tests were conducted on ordinary EPS and on each of the composite samples. The results showed a significant enhancement of thermal and mechanical properties of the composites over ordinary EPS.

Ab-initio, anatase titanium dioxide (TiO2) nanotubes were prepared from pristine anatase titanium dioxide (TiO2) nanoparticles via a low temperature modified stirring-hydrothermal technique. Scanning electron microscope (SEM) characterization of the as-synthesized sample depicted uniformly distributed one-dimensional nanotubular morphology, with an average length, thickness and diameter of ∼ 4μm, 17 nm and 20 nm, respectively. N2 physisorption of the sample revealed two distinct peaks at mesopore and macropore scales of 3 nm and 100 nm, respectively. The specific surface area of the materials was observed to have increased from 8 m² g⁻¹ for the pristine to 62 m² g⁻¹ for the nanotubes. X-ray diffraction analysis indicated a tetragonal symmetry for the anatase TiO2nanotubes sample, which is similar to those reported in the literature. Core levels and elemental analyses showed the presence of titanium and oxygen in good proportion. Electrochemical performances of the TiO2nanotubes electrode offered good cyclic stability, good rate capability and a fairly large capacity of 160 mA h g⁻¹ at a specific current of 36 mA g⁻¹.

Banana peels, a common fruit waste was adopted as a material precursor in this study to synthesize highly porous activated carbon from banana peels (ABP) which serves as an electrode material for a symmetric supercapacitor device. The activation was done using KOH pellets at different carbonization temperatures ranging from 750 C to 950 C. The ABP sample obtained from the 900 C carbonization temperature (ABP900) exhibited unique material properties such as hierarchical porous nano-architecture containing micropores, and mesopores with the highest specific surface area (1362 m 2 g À1). Electrochemical performance investigation in different neutral aqueous electrolytes showed that the best response was obtained in NaNO 3 for the ABP900 electrode. The symmetric device subsequently assembled using 1 M NaNO 3 operated in a potential window of 1.8 V, exhibited a specific capacitance of 165 F g À1 with a corresponding energy density of 18.6 W h kg À1 at 0.5 A g À1. A 100% capacitance retention and columbic efficiency were obtained after 10000 continuous charge-discharge cycles at 5 A g À1. Remarkably, after subjecting the symmetric device to a voltage holding test for 60 h, the specific capacitance was observed to increase from 165 F g À1 to 328 F g À1 with a corresponding increased energy density to about 36.9 W h kg À1 at 0.5 A g À1 , suggesting a 98% increase in device energy density from its initial value after voltage holding. Thus, the results reported showcase the ABP900 material as a potential nanostructured porous material useful in the design of high-performance electrodes for stable electrochemical capacitors.